GB2615111A

GB2615111A - Cooling arrangements for analytical device

Info

Publication number: GB2615111A
Application number: GB2201123.3A
Authority: GB
Inventors: Goeger Dirk; Nocon Blasius; Deck Alexander
Original assignee: Agilent Technologies Inc
Current assignee: Agilent Technologies Inc
Priority date: 2022-01-28
Filing date: 2022-01-28
Publication date: 2023-08-02
Also published as: CN116518572A; GB202201123D0

Abstract

A cooling arrangement 100 for an analytical device for analysing a fluidic sample to be cooled. The cooling arrangement comprises a cooling room 102 coupled with a cooling path 126 along which a cooling fluid circulates, an evaporator unit 104 coupled with the cooling room, a condenser unit 106, a compressor unit 108 and an expansion unit 110. The cooling arrangement features a condenser temperature controller 112 to control the condenser temperature to control temperature and pressure of the cooling fluid. The cooling device may instead have the expansion device configured for regulating a pressure at the evaporator unit. A temperature sensor 118 may be used to supply temperature information to the condenser temperature controller. The cooling arrangement may also include a superheat controller 114 for controlling the superheating of the cooling fluid.

Description

DESCRIPTION

COOLING ARRANGEMENTS FOR ANALYTICAL DEVICE BACKGROUND ART

[0001] The present invention relates to cooling arrangements for an analytical device, an analytical device, and methods of cooling a cooling room by circulating cooling fluid in an analytical device for analyzing a sample.

[0002] In liquid chromatography, a fluidic sample and an eluent (liquid mobile phase) may be pumped through conduits and a separation unit such as a column in which separation of sample components takes place. The column may comprise a material which is capable of separating different components of the fluidic sample.

The separation unit may be connected to other fluidic members (like a sampler or an injector, a detector) by conduits. Before the fluidic sample is introduced into a separation path between a fluid drive unit (in particular a high pressure pump) and the separation unit, a predefined amount of fluidic sample shall be intaken from a sample source (such as a sample container) via an injection needle into a sample loop by a corresponding movement of a piston within a metering device. Thereafter, an injector valve is switched so as to introduce the intaken amount of fluidic sample from the sample loop of a metering path into the separation path between the fluid drive unit and the separation unit for subsequent separation. As a result, the fluidic sample is injected into the mobile phase, such as a solvent or a solvent composition.

[0003] For injecting a fluidic sample as well as for fractionating a separated fluidic sample after sample separation, sample cooling may be desired. This may lead to reproducible injection and separation conditions and may allow to store a for instance temperature sensitive sample after fractionation, respectively.

[0004] However, sample cooling should be made with low space consumption, low energy consumption and with high precision.

DISCLOSURE

[0005] It is an object of the invention to enable sample cooling in a compact, energy-efficient and/or accurate way. This object is solved by the independent claims. -1 -

Further embodiments are shown by the dependent claims.

[0006] According to an exemplary embodiment of a first aspect of the present invention, a cooling arrangement for an analytical device for analyzing a fluidic sample to be cooled is provided, wherein the cooling arrangement comprises a cooling room coupled with a cooling path along which a cooling fluid circulates, an evaporator unit for evaporating cooling fluid, wherein the evaporator unit is thermally coupled with the cooling room, a condenser unit for condensing cooling fluid evaporated in the evaporator unit, a compressor unit for compressing cooling fluid flowing from the evaporator unit towards the condenser unit, an expansion unit for expanding cooling fluid flowing from the condenser unit towards the evaporator unit, and a condenser temperature controller configured for controlling a condenser temperature to control temperature and pressure of the cooling fluid.

[0007] According to another exemplary embodiment of the first aspect of the invention, a method of cooling a cooling room by circulating cooling fluid along a cooling path in an analytical device for analyzing a sample is provided, wherein the method comprises evaporating cooling fluid by an evaporator unit which is thermally coupled with the cooling room, condensing cooling fluid evaporated in the evaporator unit by a condenser unit, compressing cooling fluid when flowing from the evaporator unit towards the condenser unit by a compressor unit, expanding cooling fluid when flowing from the condenser unit towards the evaporator unit by an expansion unit, and controlling a condenser temperature to control temperature and pressure of the cooling fluid.

[0008] According to an exemplary embodiment of a second aspect of the present invention, a cooling arrangement for an analytical device for analyzing a fluidic sample to be cooled is provided, wherein the cooling arrangement comprises a cooling room coupled with a cooling path along which a cooling fluid circulates, an evaporator unit for evaporating cooling fluid, wherein the evaporator unit is thermally coupled with the cooling room, a condenser unit for condensing cooling fluid evaporated in the evaporator unit, a compressor unit for compressing cooling fluid flowing from the evaporator unit towards the condenser unit, and an expansion unit for expanding cooling fluid flowing from the condenser unit towards the evaporator unit, wherein the expansion unit is configured for regulating a pressure at the evaporator unit. -2 -

[0009] According to another exemplary embodiment of the second aspect of the invention, a method of cooling a cooling room by circulating cooling fluid along a cooling path in an analytical device for analyzing a sample is provided, wherein the method comprises evaporating cooling fluid by an evaporator unit which is thermally coupled with the cooling room, condensing cooling fluid evaporated in the evaporator unit by a condenser unit, compressing cooling fluid when flowing from the evaporator unit towards the condenser unit by a compressor unit, expanding cooling fluid when flowing from the condenser unit towards the evaporator unit by an expansion unit, and regulating a pressure at the evaporator unit by the expansion unit.

[0010] According to still another exemplary embodiment, an analytical device for analyzing a fluidic sample is provided, wherein the analytical device comprises a cooling arrangement having the above-mentioned features for cooling the fluidic sample.

[0011] In the context of the present application, the term "cooling room" may particularly denote a spatially defined volume which is brought to a temperature below ambient temperature by the cooling effect of a cooling fluid being processed in a cooling arrangement and being brought in thermal exchange with an interior of the cooling room. In particular, a cooling room may be a cooling chamber which can be fully circumferentially delimited with respect to an environment.

[0012] In the context of the present application, the term "cooling path" may particularly denote a closed loop along which a cooling fluid is driven to flow and which includes a portion being thermally coupled with or extending through or along the cooling room. Driving cooling fluid along the closed cooling path may be repeated continuously as long as the cooling arrangement is active. For instance, at least part of the cooling path may be defined by fluidic conduits such as capillaries.

[0013] In the context of the present application, the term "cooling fluid" or coolant may particularly denote a medium which can be repeatedly converted between a liquid phase and a gaseous phase while circulating along the cooling path to thereby continuously cool the cooling room and material (for example a fluidic sample in a sample container) therein. For instance, the cooling fluid may comprise isobutane. In order to tune its properties, the cooling fluid may also comprise one or more additives. -3 -

[0014] In the context of the present application, the term "evaporator unit" may particularly denote a device used in the cooling process to turn a liquid form of the cooling fluid into its gaseous form or vapor. At least part of the liquid cooling fluid may thus be evaporated or vaporized by the evaporator unit into its gas form. One example for an evaporator unit is a radiator coil used in the closed, compressor-driven cooling loop along which the cooling fluid flows. For example, an evaporator unit may comprise finned tubes and may absorb heat from gas blown through a coil by a fan. Fins and tubes may be made of metals with high thermal conductivity to obtain a high heat transfer. The cooling fluid may vaporize from the heat it absorbs in the evaporator. Many other configurations of an evaporator unit are possible. In particular, an evaporator unit may be capable of operating or vaporizing cooling medium to evaporate or vaporize from liquid to gas within the cooling path while absorbing heat from the enclosed cooling room as cooled region.

[0015] In the context of the present application, the term "condenser unit" may particularly denote an entity such as a heat exchanger which may be used to at least partially condense a gaseous cooling fluid into a liquid state through cooling. In so doing, latent heat may be released by the cooling fluid and may be transferred to the surrounding environment. In the cooling arrangement, a condenser unit may be used for heat dissipation away from the cooling fluid.

[0016] In the context of the present application, the term "compressor unit" may particularly denote a mechanical device that increases the pressure of the cooling medium in an at least partially gaseous state by reducing its volume. For instance, this may be accomplished by a piston mechanism. More precisely, a piston may be driven by a motor to suck in and compress the cooling fluid in a cylinder. As the piston moves down into the cylinder, it sucks the cooling fluid from the evaporator unit. An intake valve may close when the pressure of the cooling fluid inside the cylinder reaches that of the pressure in the evaporator unit. When the piston hits the point of maximum downward displacement, it compresses the cooling fluid on the upstroke. The cooling fluid may be pushed through the exhaust valve into the condenser unit.

Both the intake and exhaust valves may be designed so that the flow of the cooling fluid only travels in one direction through the cooling path.

[0017] In the context of the present application, the term "expansion unit" may -4 -particularly denote an entity in the cooling path which expands the cooling fluid after condensing and prior to evaporation. Thus, the expansion unit may process cooling fluid in an at least partially liquid state. In particular, the expansion unit may define the amount of cooling fluid released into the evaporator unit. For example, the expansion unit may be an expansion valve, in particular a thermal expansion valve, or merely a capillary of the cooling path. The design of the expansion unit may vary significantly in different embodiments.

[0018] In the context of the present application, the term "condenser temperature controller" may particularly denote a controller or regulator controlling or regulating the temperature of the cooling fluid in the condenser unit. When controlling the temperature of the cooling fluid in the condenser unit, the condenser temperature controller may also control the pressure of the cooling fluid in the condenser unit.

[0019] In the context of the present application, the term "regulating a pressure at the evaporator unit" may particularly denote adjusting the pressure value of the cooling fluid when flowing through the evaporator unit in a defined way.

[0020] In the context of this application, the term "analytical device" may particularly denote any apparatus which is capable of analyzing a sample, in particular a fluidic sample. For example, the analytical device may be a sample separation apparatus configured for separating different fractions of a fluidic sample by applying a certain separation technique, in particular liquid chromatography.

[0021] According to an exemplary embodiment of both aspects of the invention, a fluidic sample may be cooled in an analytical device (such as an HPLC) by bringing the fluidic sample in thermal exchange with a cooling room of a cooling arrangement. The cooling room can be cooled by a cooling fluid circulating along a cooling path which encompasses the cooling room. In the cooling room, the cooling fluid can be at least partially evaporated from a previously liquid phase to a subsequently gaseous phase. During this process, thermal energy required for evaporation of the cooling fluid is taken from the cooling room, which is thereby cooled. In order to continuously cool the cooling room, the evaporated cooling fluid may then be compressed and subsequently condensed into an at least partially liquid phase. During the latter mentioned condensation, heat may be removed from the condensing cooling fluid and may be dissipated to an environment, so that the cooling medium is cooled again. -5 -

Thereafter, the liquefied cooling fluid may be expanded in an expansion unit before being introduced again into the cooling room. The process may then be repeated, in particular continuously.

[0022] According to an exemplary embodiment of the first aspect of the invention, the thermal conditions of the cooling fluid circulating in the closed loop cooling path, as described, may be adjusted by a condenser temperature controller which may ensure that temperature and pressure of the cooling fluid in the region of the condenser unit are controlled. This may have the advantage that a very simple expansion unit may be used, for instance a simple capillary rather than a more complex thermal expansion valve. Thus, the condenser temperature controller may influence the cooling fluid in the condenser unit so that it is properly conditioned for subsequent expansion. Active control of the cooling fluid flow in the expansion unit may then be dispensable. Descriptively speaking, a sophisticated thermal expansion valve may be emulated by a very simple expansion unit (for instance a passive flow restriction, such as a capillary) in combination with a programming of the operation of the cooling arrangement for temperature and pressure control of cooling fluid at the condenser unit. This may render a sophisticated expansion unit dispensable and allows to construct the cooling arrangement in a compact way. This may be advantageous in particular for an application of the cooling arrangement for sample cooling in an analytical device where the installation space may be limited.

Furthermore, the described concept of controlling temperature and pressure of the cooling fluid by controlling condenser temperature may contribute to an adjustment of the supply of cooling fluid to the amount of extracted heat. Said condenser temperature control may control the condenser unit to operate at a desired operation point what concerns pressure and temperature. As a result, a cooling arrangement may be obtained which allows precise cooling of a fluidic sample of an analytical device with low space requirements and with reasonable energy consumption. Furthermore, sample cooling may be very accurate, which may have a positive impact on the precision of sample analysis in the analytical device.

[0023] According to an exemplary embodiment of the second aspect of the invention, an expansion unit may be provided which regulates pressure conditions during subsequent evaporation of cooling fluid, i.e. while the cooling fluid is in thermal exchange with the cooling room. For instance, the expansion unit may be embodied -6 -as expansion valve which can adjust the pressure at its outlet. More specifically, the expansion unit may be for example a throttle valve which adjusts itself based on a pressure value at its evaporator-sided outlet. For this purpose, the expansion unit may for instance be embodied as a pressure regulating expansion valve. Descriptively speaking, an adjusted pressure of the cooling fluid in the cooling room may correspond to a desired evaporation temperature. When applying this concept to a sample cooling arrangement of an analytical device, sample cooling may be achieved with low space consumption and in an energy efficient way. Moreover, the described architecture of sample cooling may be very accurate. Furthermore, pressure (and consequently temperature) control of the cooling fluid in the evaporator unit may also have a positive impact on the subsequent compression unit which can be supplied with property conditioned cooling fluid. The pressure controlling expansion unit may contribute (in particular in combination with the compressor unit) to a regulation of the cooling power in accordance with the requirements of the cooling performance in the cooling room.

[0024] In the following, further embodiments of the cooling arrangements, the analytical device, and the methods will be explained.

[0025] Next, further embodiments of the first aspect will be explained: [0026] In an embodiment, the condenser temperature controller is configured for controlling the condenser temperature based on at least one temperature of the cooling fluid next to the condenser. For example, the real temperature of the cooling fluid may be measured at the condenser unit. This actual temperature value may then be compared with a target condenser temperature, and the condenser unit may be controlled or regulated correspondingly.

[0027] In an embodiment, the at least one temperature of the cooling fluid used as a basis for controlling the condenser temperature comprises at least one of a temperature of the cooling fluid at an inlet of the condenser, at an outlet of the condenser and/or between the condenser unit and the expansion unit. The cooling fluid may flow from the compressor unit towards the condenser unit and from there to the expansion unit. Temperature sensing as a basis for the condenser temperature control may be performed upstream of the condenser unit (i.e. between the compressor unit and the condenser unit) and/or downstream of the condenser unit -7 - (i.e. downstream of the condenser unit and upstream of the expansion unit). It may be preferred to sense said temperature after the cooling fluid has passed the condenser unit in order to obtain temperature information reflecting the actual operation of the condenser unit. A beneficial position of the mentioned temperature sensor may be a position that reflects the condensing temperature. If measured above the liquid phase, the excessively high hot gas temperature may be measured. In contrast to this, the temperature of the supercooled liquid may be measured well behind the condenser unit. Care should thus be taken to properly select a temperature measurement position of a corresponding sensor.

[0028] In an embodiment, the cooling arrangement comprises one or more temperature sensors for sensing and supplying to the condenser temperature controller temperature information indicative of the at least one temperature of the cooling fluid next to the condenser. For instance, said temperature sensor may be attached to a capillary through which the cooling fluid flows between condenser unit and expansion unit. For example, said temperature sensor may be a resistive temperature sensor.

[0029] In an embodiment, the condenser temperature controller is configured for controlling the condenser temperature based on a condenser temperature set point (in particular for controlling the condenser temperature so that it assumes or approaches the condenser temperature set point) indicative of a target cooling power of the cooling arrangement. As a basis for its control or regulation function, the condenser temperature controller may compare the actually sensed temperature with the condenser temperature set point, i.e. a desired target value. Said target value may be selected so that a desired cooling power of the cooling arrangement is achieved when the actual temperature of the cooling fluid at the condenser unit is brought to the condenser temperature set point. For instance, the condenser temperature set point may be a fixed reference temperature, or, even more preferred, may be a temperature value selected based on the actual present conditions of the cooling arrangement.

[0030] In an embodiment, the condenser temperature set point is provided to the condenser temperature controller by a superheat controller configured for controlling a superheating characteristic of the cooling fluid. Thus, the superheat controller may -8 - control superheating of the cooling fluid. In particular downstream of the evaporator unit, at least part of the cooling fluid may be in a superheated condition. Thus, superheating of cooling fluid may occur in the evaporator unit. In this context, the term "superheating" may denote in particular raising the temperature of gaseous or steam-type cooling fluid to a temperature value above its boiling point. Thus, superheating may denote heating a vapor above its boiling point. Superheating cooling fluid may be caused by evaporation in the evaporator unit and may prevent it from condensing in the compressor unit. Superheating may be advantageous for the compressor unit because a cooling fluid being present as a liquid-gas mixture might damage the compressor unit, in view of the incompressibility of liquid.

[0031] In an embodiment, the superheat controller is configured for determining the condenser temperature set point based on at least one of the following parameters, in particular based on each of the following parameters: [0032] -a temperature of the cooling fluid in the cooling room upstream of the evaporator unit, in particular sensed by a temperature sensor (thus, the condenser temperature set point may depend on the temperature of the cooling fluid directly before evaporating, i.e. may depend on an evaporation temperature); [0033] -a temperature of the cooling fluid in the cooling room downstream of the evaporator unit, in particular sensed by a (in particular further) temperature sensor (hence, the condenser temperature set point may depend on the temperature of the cooling fluid directly after evaporating, i.e. may depend on a suction gas temperature); and [0034] -a superheating temperature set point indicative of a target superheating temperature of the cooling fluid (which may be a predefined or user-defined reference value being indicative of the target cooling power for the cooling arrangement).

[0035] In an embodiment, the expansion unit comprises or consists of an evaporator capillary. Advantageously, a simple capillary may be sufficient for functioning as evaporator unit. This may reduce the space consumption of the cooling arrangement. For instance, the capillary-type expansion unit may have a smaller inner diameter than other parts of the conduits of the cooling path, in particular than the entire conduits of the remaining cooling path. In combination with the condenser -9 -temperature control, the capillary-type expansion unit may emulate a more complex thermal expansion valve or an electronic expansion valve. Thus, when configuring the condenser temperature controller for emulating a function of an evaporator expansion valve, the hardware requirements of the expansion unit may be significantly relaxed without compromising on cooling performance and accuracy.

[0036] In an embodiment, the expansion unit is a non-controlling and/or non-adjustable expansion unit. Since the expansion unit needs no adjustment for controlling one or more other units of the cooling arrangement, it can be constructed in a very simple way, for instance as a flow restriction such as a capillary. To put it shortly, the expansion unit may operate entirely passive.

[0037] In an embodiment, the cooling arrangement comprises a ventilator arranged for impacting a heat exchanger of the condenser unit and being controllable by the condenser temperature controller. For example, the condenser unit may be embodied as a fan-controlled heat exchanger. Said heat exchanger may dissipate heat from the cooling fluid towards an environment. When a ventilator applies an air flow to such a condenser unit, the strength of the air flow may influence the heat exchanger efficiency and may therefore adjust the condensing function of the condenser unit. The condensing power may therefore be adjusted in accordance with a desired operating point of the cooling arrangement. This may adjust the condenser temperature.

[0038] In an embodiment, the cooling arrangement comprises an evaporator temperature controller configured for controlling a temperature of the cooling fluid downstream of the expansion unit, in particular during evaporation by the evaporation unit. The evaporator temperature controller may regulate the evaporation pressure via the temperature, which may be measured directly after the expansion unit.

Depending on this measured temperature and its setpoint, the speed of the compressor unit may be changed. . It is possible that the evaporator temperature control ensures that the cooling temperature in the cooling room is not too low, for instance to prevent undesired freezing of the evaporator unit. This may make it possible to operate the cooling arrangement and in particular the evaporator unit without defrosting. Protecting samples from freezing may be a beneficial consequence of this.

[0039] In an embodiment, the evaporation temperature controller is configured for controlling the temperature of the cooling fluid downstream of the expansion unit, in particular during evaporation, by controlling the compressor unit. The compressor unit may influence the evaporation temperature and pressure, i.e. the temperature during evaporation. Advantageously, the evaporator temperature controller may control the compressor unit (which may be arranged directly downstream of the evaporator unit) so that a desired evaporation pressure and consequently evaporation temperature of the cooling fluid may be achieved. For this purpose, it is for example possible that a compressor control signal is generated by the evaporator temperature controller for controlling a drive unit (such as a motor) of the compressor unit for adjusting an intake volume. For example, a compressor speed signal may adjust a driving speed of the drive unit driving the compressor unit.

[0040] In an embodiment, the evaporation temperature controller is configured for controlling the temperature of the cooling fluid after or downstream of the expansion unit, in particular during evaporation, based on at least one of the following parameters, in particular based on each of the following parameters: [0041] -a temperature of the cooling fluid in the cooling room upstream of the evaporator unit, in particular sensed by a temperature sensor (thus, a compressor speed signal may depend on the temperature of the cooling fluid directly before evaporating, i.e. an evaporation temperature); and [0042] -an evaporator temperature set point indicative of an evaporation target temperature of the cooling fluid (which may be a predefined or user-defined reference value being indicative of desired evaporation properties, for instance to ensure that a temperature of an aqueous fluidic sample to be cooled remains reliably above the freezing point of water). First and foremost, protection of the evaporator unit from icing can be implemented. As a result, protection of the sample against icing can be achieved. As a result, continuous operation without defrost cycle can be made possible.

[0043] In an embodiment, the cooling arrangement comprises at least one temperature sensor (such as a Pt100 sensor) for sensing sensor data indicative of at least one temperature of the circulating cooling fluid. As already mentioned above, a respective temperature sensor may be arranged upstream and/or downstream of the evaporator unit in the cooled room to sense a temperature of the cooling fluid directly before and/or directly after evaporation. It is also possible that a further temperature sensor is provided downstream of the condenser unit to sense the temperature of the cooling fluid directly after condensing, which may be a meaningful parameter for condenser temperature control. If desired or required, one or more additional or alternative temperature sensors may be provided. Additionally or alternatively, one or more pressure sensors may be provided along the cooling path.

[0044] Next, further embodiments of the second aspect will be explained: [0045] In an embodiment, the evaporation pressure does not regulate the cooling performance or cooling capacity alone. In addition, at least the evaporator surface exposed to refrigerant may contribute to the regulation of the cooling performance as well. For example, a smaller area at lower temperature can provide the same cooling performance as a larger area at higher temperature. The evaporation pressure may be therefore only partially responsible for the cooling performance achieved. In an embodiment of the invention, the surface exposed to refrigerant may be regulated by the speed of the compressor unit.

[0046] In an embodiment, the cooling arrangement is configured for controlling a cooling power of the cooling arrangement by said pressure regulation. When the expansion unit, preferably embodied as expansion valve, is gradually opened to enable an increased flow of cooling fluid into the evaporator unit, a mass flow of cooling fluid through the cooling path may be increased, thereby increasing the cooling power. Correspondingly, when the expansion valve is gradually closed to enable only a decreased flow of cooling fluid, the mass flow of cooling fluid through the cooling path and into the evaporator unit may be decreased, so that the cooling power may be decreased as well. Hence, the pressure regulation at the evaporator unit by the expansion unit may impact the cooling power and may thus function as a cooling power adjustment mechanism.

[0047] In an embodiment, the expansion unit is configured as expansion valve.

Preferably, said expansion valve may comprise a (for instance spring-) biased 30 membrane, wherein the condenser unit may be arranged on one side of the membrane and the evaporator unit may be arranged on the other side of the membrane. For example, the biasing force of the expansion valve may be set to a fixed value by a user or at a factory side. Depending on the pressure conditions on both sides (in particular depending on the pressure difference between both sides, in combination with the biasing force) of the membrane, the degree of opening of the expansion valve may be adjusted in a self-sufficient way. As a result, more or less cooling fluid may be supplied to the evaporator unit, thereby impacting the pressure in the evaporator unit. Consequently, the described valve configuration of the expansion unit may allow to execute the above described pressure regulation in a passive way, i.e. without actively controlling the expansion valve.

[0048] Alternatively, the expansion valve may be an actively controlled valve which may be electronically controlled for instance based on at least one pressure value sensed by at least one pressure sensor. Such a pressure sensor may be arranged for example at the evaporator unit or between the expansion unit and the evaporator unit.

[0049] In an embodiment, the expansion unit is configured for regulating the pressure at the evaporator unit to a predefined constant value. Hence, a regulation algorithm may keep the pressure at the evaporator unit at a predetermined fixed value. Thus, the expansion unit may make sure that the pressure at the evaporator unit always remains constant. If the pressure at the evaporator unit exceeds beyond the predefined constant value (for example since the compressor unit intakes or draws in a relatively small amount of cooling fluid), the expansion valve may be gradually closed so as to reduce the amount of supplied cooling fluid. If however the pressure at the evaporator unit falls below the predefined constant value (for example since the compressor unit intakes or draws in a relatively large amount of cooling fluid), the expansion valve may be gradually opened so as to increase the amount of supplied cooling fluid.

[0050] In an embodiment, the expansion unit is configured for regulating a temperature at the evaporator unit, in particular to a predefined constant value. Descriptively speaking, an adjusted pressure value at the evaporator unit corresponds to an assigned evaporator temperature. Hence, when the pressure in the cold room or cooling room is regulated to assume a target value, the evaporator temperature may be also at a desired value.

[0051] In an embodiment, the cooling arrangement comprises a superheat -13-controller configured for controlling a superheating characteristic of the cooling fluid. For instance, the superheat controller may be configured for controlling a superheating temperature of the cooling fluid, in particular for controlling the superheating temperature to a predefined value. After evaporation in the evaporator unit, the cooling fluid may be in a superheated condition. Hence, the superheat controller may control for example temperature and/or amount of superheating of the cooling fluid. In particular between evaporator unit and compressor unit, at least part of the cooling fluid may be in the above-described superheated condition. By superheating cooling fluid, a highly undesired presence of condensed liquid cooling fluid in the compressor unit may be avoided which may disturb or even damage the compressor unit. By adjusting the superheating characteristics, integrity of the cooling arrangement may be ensured and the cooling power may be set to a reasonable level.

[0052] In an embodiment, the superheat controller is configured for controlling a speed of a drive unit (in particular a motor) for driving the compressor unit to thereby adjust a cooling power of the cooling arrangement. The higher the compressor speed, the larger may be the intake volume of the compression unit, and the higher will be the cooling power. For example in the event of an initial cooling of fluidic samples prior to analyzing them in an analytical device, a higher cooling power may be needed than in a steady-state operation of the cooling arrangement at which the fluidic samples are already cooled to a target temperature. Adjusting a compressor speed may be a simple mechanism of adjusting cooling power.

[0053] In an embodiment, the cooling arrangement comprises a cooling room temperature controller configured for controlling a temperature of the cooling room, in particular by correspondingly controlling the superheat controller. Preferably, the cooling room temperature controller is configured for controlling the temperature of the cooling room based on a comparison between a predefined cooling room target temperature (which may also be denoted as a cold room temperature set point) and a sensed actual temperature in the cooling room. By taking this measure, the desired temperature of the cooling fluid in the cooling room may be adjusted precisely.

[0054] In an embodiment, the superheat controller is configured for controlling the compressor unit based on an output of the cooling room temperature controller and a temperature of the cooling fluid in the cooling room downstream of the evaporator unit -14- (which may also be denoted as suction gas temperature), in particular sensed by a temperature sensor. Hence, a speed of a drive unit for driving the compressor unit may be adjusted precisely when taking into account an actually measured temperature next to an outlet of the evaporator unit.

[0055] In an embodiment, the cooling arrangement comprises a condenser temperature controller configured for controlling a temperature at the condenser unit based on a comparison between a predefined target temperature (which may also be denoted as condensing setpoint) and a temperature of the cooling fluid sensed or measured at an outlet of the condenser unit and/or between the condenser unit and the expansion unit. Such a control scheme is very simple and allows to adjust the temperature of the cooling fluid at the condenser unit in an appropriate way.

[0056] In an embodiment, the analytical device is configured as sample separation apparatus On particular a liquid chromatography device, such as an HPLC (high performance liquid chromatography)) for separating the fluidic sample and comprises a fluid drive (for example an analytical pump, such as a high-pressure piston pump) for driving the fluidic sample and/or a mobile phase (such as a solvent or solvent composition) in which the fluidic sample is injected, and a sample separation unit (preferably a chromatographic separation column) for separating the fluidic sample in the mobile phase. In the context of this application, the term "fluidic sample" may particularly denote any liquid and/or gaseous medium, optionally including also solid particles, which is to be analyzed. Such a fluidic sample may comprise a plurality of fractions of molecules or particles which shall be separated, for instance small mass molecules or large mass biomolecules such as proteins. Separation of a fluidic sample into fractions may involve a certain separation criterion (such as mass, volume, chemical properties, etc.) according to which a separation is carried out. In the context of this application, the term "mobile phase" may particularly denote any liquid and/or gaseous medium which may serve as fluidic carrier of the fluidic sample during separation. A mobile phase may be a solvent or a solvent composition (for instance composed of water and an organic solvent such as ethanol or acetonitrile).

In an isocratic separation mode of a liquid chromatography apparatus, the mobile phase may have a constant composition over time. In a gradient mode, however, the composition of the mobile phase may be changed over time, in particular to desorb fractions of the fluidic sample which have previously been adsorbed to a stationary phase of a separation unit. In the context of the present application, the term "fluid drive" may particularly denote an entity capable of driving a fluid (i.e. a liquid and/or a gas, optionally comprising solid particles), in particular the fluidic sample and/or the mobile phase. For instance, the fluid drive may be a pump (for instance embodied as piston pump or peristaltic pump) or another source of high pressure. For instance, the fluid drive may be a high-pressure pump, for example capable of driving a fluid with a pressure of at least 100 bar, in particular at least 500 bar. In the context of the present application, the term "sample separation unit" may particularly denote a fluidic member through which a fluidic sample is transferred and which is configured so that, upon conducting the fluidic sample through the separation unit, the fluidic sample will be separated into different groups of molecules or particles. An example for a separation unit is a liquid chromatography column which is capable of trapping or retarding and selectively releasing different fractions of the fluidic sample.

[0057] In an embodiment, the cooling arrangement is configured for cooling a sample container, in particular in a sample rack, containing the fluidic sample to be analysed. In particular prior to a sample separation run in a chromatographic sample separation apparatus, a precise temperature adjustment of the fluidic sample may be highly advantageously for defining accurate and reproducible separation conditions. Thus, an accurate temperature control may lead to a high separation precision and reproducibility.

[0058] In an embodiment, the cooling arrangement comprises an injector implementing the cooling arrangement and being configured to inject the fluidic sample into mobile phase for analyzing the fluidic sample. For instance, such an injector may comprise a needle being movable by a robot or the like to immerse the needle into the temperature-controlled fluidic sample in a sample container.

Thereafter, fluidic sample may be aspirated through the needle into a sample loop of the injector. This intake process may be carried out by withdrawing a piston of a metering device. Thereafter, the needle may be driven in a needle seat, and the aspirated fluidic sample may be injected from the sample loop into a separation path between a fluid drive and a sample separation unit (such as a chromatographic separation column).

[0059] In an embodiment, the cooling arrangement comprises a fractionation unit implementing the cooling arrangement and being configured to collect analyzed fluidic sample. After separating a fluidic sample in fractions in a sample separation apparatus, the separated fractions may be filled in different sample vials or other sample containers where they can be stored at a controlled temperature by the cooling arrangement. For example, the separated fractions downstream of a sample separation unit or of a detector may be guided through a fractionating needle into sample containers.

[0060] Although the previously described embodiments primarily use a cooling arrangement according to an exemplary embodiment in an analytical device, other applications are possible as well (for instance a use of a cooling arrangement in a refrigerator).

[0061] Embodiments may be implemented in conventionally available HPLC systems, such as the analytical Agilent 1290 Infinity II LC system or the Agilent 1290 Infinity II Preparative LC/MSD system (both provided by the applicant Agilent Technologies -see www.aqilent.com -which shall be incorporated herein by reference).

[0062] One embodiment of a sample separation apparatus comprises a pump having a pump piston for reciprocation in a pump working chamber to compress liquid in the pump working chamber to a high pressure at which compressibility of the liquid becomes noticeable. This pump may be configured to know (by means of operator's input, notification from another module of the instrument or similar) or elsewise derive solvent properties.

[0063] The sample separation unit of the sample separation apparatus preferably comprises a chromatographic column (see for instance http://en.wikipedia.orq/wiki/Column chromatoaraphy) providing a stationary phase.

The column may be a glass or steel tube (for instance with a diameter from 50 pm to 5 mm and a length of 1 cm to 1 m) or a microfluidic column (as disclosed for instance in EP 1577012 or the Agilent 1200 Series HPLC-Chip/MS System provided by the applicant Agilent Technologies). The individual components are retained by the stationary phase differently and at least partly separate from each other while they are propagating at different speeds through the column with the eluent. At the end of the column they elute one at a time or at least not entirely simultaneously. During the entire chromatography process the eluent may be also collected in a series of fractions. The stationary phase or adsorbent in column chromatography usually is a solid material. The most common stationary phase for column chromatography is silica gel, surface modified silica gel, followed by alumina. Cellulose powder has often been used in the past. Also possible are ion exchange chromatography, reversed-phase chromatography (RP), affinity chromatography or expanded bed adsorption (EBA). The stationary phases are usually finely ground powders or gels and/or are microporous for an increased surface.

[0064] The mobile phase (or eluent) can be a pure solvent or a mixture of different solvents (such as water and an organic solvent such as ACN, acetonitrile). It can be chosen for instance to adjust the retention of the compounds of interest and/or the amount of mobile phase to run the chromatography. The mobile phase can also be chosen so that the different compounds or fractions of the fluidic sample can be separated efficiently. The mobile phase may comprise an organic solvent like for instance methanol or acetonitrile, often diluted with water. For gradient operation water and organic is delivered in separate bottles, from which the gradient pump delivers a programmed blend to the system. Other commonly used solvents may be isopropanol, THF, hexane, ethanol and/or any combination thereof or any combination of these with aforementioned solvents.

[0065] A fluidic sample analyzed by a sample separation apparatus according to an exemplary embodiment of the invention may comprise but is not limited to any type of process liquid, natural sample like juice, body fluids like plasma or it may be the result of a reaction like from a fermentation broth.

[0066] The pressure, as generated by the fluid drive, in the mobile phase may range from 2-200 MPa (20 to 2000 bar), in particular 10-150 MPa (150 to 1500 bar), and more particular 50-120 MPa (500 to 1200 bar).

[0067] The sample separation apparatus, for instance an HPLC system, may further comprise a detector for detecting separated compounds of the fluidic sample, a fractionation unit for outputting separated compounds of the fluidic sample, or any combination thereof. For example, a fluorescence detector may be implemented.

[0068] Embodiments of the invention can be partly or entirely embodied or supported by one or more suitable software programs, which can be stored on or otherwise provided by any kind of data carrier, and which might be executed in or by any suitable data processing unit. Software programs or routines can be preferably applied in or by the control unit.

BRIEF DESCRIPTION OF DRAWINGS

[0069] Other objects and many of the attendant advantages of embodiments of the present invention will be readily appreciated and become better understood by reference to the following more detailed description of embodiments in connection with the accompanied drawings. Features that are substantially or functionally equal or similar will be referred to by the same reference signs.

[0070] Figure 1 shows a sample separation apparatus in accordance with embodiments of the present invention, particularly used in high performance liquid chromatography (H PLC).

[0071] Figure 2 shows a schematic view of a cooling arrangement according to an exemplary embodiment of the invention.

[0072] Figure 3 shows a portion of a cooling arrangement according to an exemplary embodiment of the invention.

[0073] Figure 4 shows a portion of a cooling arrangement according to an exemplary embodiment of the invention.

[0074] Figure 5 shows a schematic view of a cooling arrangement according to another exemplary embodiment of the invention.

[0075] The illustration in the drawing is schematically.

[0076] Before describing the figures in further detail, some basic considerations of the present invention will be summarized based on which exemplary embodiments 25 have been developed.

[0077] According to an exemplary embodiment of the first aspect of the invention, a temperature at a condenser unit of a cooling arrangement for cooling a fluidic sample in an analytical device may be controlled to thereby control temperature and pressure of cooling fluid of the cooling arrangement in particular upstream of an expansion unit. This may allow to emulate a function of a complex thermal expansion valve by a combination of a simple flow restriction (such as a capillary) as expansion unit with a (for example software-based) temperature control of the condenser unit.

In particular, it may be advantageous to control the condenser temperature in order to control the temperature and thus the pressure of the cooling fluid.

[0078] More specifically, an embodiment of the first aspect may relate to a superheating control with an expansion unit which does not require a thermal steering.

[0079] Conventional cooling arrangements may require an expansion unit that adjusts the pressure of a high pressure side of a cooling path to the pressure of a low pressure side by generating a pressure difference. In many cooling arrangements, such as refrigerators, capillary tubes are used which are robust and cheap. However, these capillary tubes are designed for a specific operating point. Characteristic operating variables are evaporation and liquefaction pressure or associated temperatures. Furthermore, the energy input to an evaporator unit, the environment of the cooling arrangement and the mass flow conveyed by the compressor unit may play a role. The mass flow through the capillary tube may be largely dependent on the temperature in the condenser unit, the temperature in the evaporator unit and the supercooling of the coolant upstream of the capillary tube.

[0080] Changes in these parameters may lead to altered mass flow that the compressor unit conveys. If the energy input to the evaporator unit is reduced, for example because the medium to be cooled has being cooled to a set temperature, less coolant evaporates. As a result, the evaporation distance in the evaporator unit may shift towards the compressor unit and the superheating may decrease. If the amount of heat supplied to the evaporator unit is too low, liquid coolant may be sucked in by the compressor unit as a result. This may lead to a damage of the compressor unit. Insufficient superheating of suction gas can result in compression into a wet steam region, especially with R600a as cooling medium. In order to take account of these issues, thermostatic or electronic expansion valves may be used to ensure superheating of the gas sucked in by the compressor unit, which promotes a safe operation of the cooling arrangement. Alternatively, inefficient evaporator units may be used, which may be designed to be larger than necessary and ensure -20 -superheating of the suction gas in view of operational safety.

[0081] To avoid the above issues, mechanically adjustable expansion units may be used. These require additional installation space, may be not available for certain (in particular small) power classes and may cause high effort. Thermal expansion units may require a high minimum superheating, for which a correspondingly larger evaporator unit needs be used.

[0082] According to an embodiment of the first aspect, a cooling arrangement and a method for controlling superheating in a cooling arrangement with a thermally non-regulating and in-service non-adjustable expansion unit is provided. This may ensure a proper regulation of superheating of gaseous cooling fluid sucked in by the compressor unit. In particular, a temperature control of the condenser unit may be adapted to cooling capacity requirements, superheating and load conditions of a respective application.

[0083] Embodiments may ensure a safe and efficient operation in a wide range of operating points using a simple expansion unit such as a capillary or another flow restriction. An evaporator unit may be operated without inappropriate superheating zone.

[0084] For small cooling arrangements, thermal and electronic expansion valves are often not available, or may involve considerable effort. Embodiments of the invention may simulate or emulate the function of an expansion valve that regulates superheating.

[0085] In partial load ranges of the cooling arrangement, this may make it possible to ensure sufficient superheating at an inlet of the compressor unit when using a capillary as an expansion unit. Advantageously, this may also lead to a protection of the compressor unit. Under full load, exemplary embodiments may ensure a proper (in particular an optimal) filling of the evaporator unit with cooling fluid (in particular to adjust a maximum cooling capacity). Furthermore, exemplary embodiments may allow to carry out an adaptation of superheating in accordance with load requirements of a specific application. Beyond this, exemplary embodiments may ensure an energy-efficient operation of the cooling arrangement.

Further advantageously, exemplary embodiments of the invention may render the -21 -cooling arrangement additionally tolerant with respect to overfilling with cooling fluid, partial loss of the cooling fluid over time and manufacturing tolerances. By a control algorithm according to an exemplary embodiment of the invention, superheating of suction gas may be adapted to the requirements of the cooling arrangement at a current operating point.

[0086] Further advantages of exemplary embodiments may be the following: Operational safety may be improved even in an operation mode with partial load. Furthermore, a safe operating range may be extended. Operation may be made possible in multiple cooling zones and/or in multiple environmental conditions (in particular in terms of ambient temperature, humidity, etc.). Beyond this, the effort involved with the provision of an expansion unit may be reduced. An adjustment of the mass flow of the cooling fluid by the expansion unit according to the mass flow sucked in by the compressor unit may be carried out. This may protect the compressor unit against liquid shocks and insufficient cooling. Exemplary embodiments may also form a basis for an extremely precise temperature control of the cooling room. Furthermore, it may be possible to reliably prevent a shift of cooling fluid in the cooling arrangement. A cooling arrangement according to an exemplary embodiment may also reduce energy consumption and/or may increase the cooling capacity (and thereby the Energy Efficiency Ratio, EER, i.e. the ratio of output cooling energy to input electrical energy at a given operating point) by lowering the liquefaction pressure, for instance to the minimum necessary pressure. Apart from this, robustness against manufacturing tolerances of the cooling arrangement may be increased. Furthermore, overfilling of the cooling arrangement with cooling fluid and partial loss of the cooling fluid may be reliably prevented.

[0087] According to an exemplary embodiment of the second aspect of the invention, an expansion unit of the cooling arrangement may be configured so that it may regulate the cooling fluid pressure at the evaporator unit. More specifically, the expansion unit may be embodied as expansion valve which can adjust its pressure at its outlet. This may make it possible to control the cooling power of the cooling arrangement by a pressure regulated expansion valve. Hence, the expansion valve may define and control the pressure for the evaporator unit which in turn defines the temperature in the cooling room. For example, the speed of the compressor unit may be controlled in order to control the cooling power in the cooling room.

-22 - [0088] In a nutshell, an exemplary embodiment of the second aspect may enable to control the cooling capacity and superheating in a cooling arrangement with a pressure-controlled expansion unit.

[0089] As mentioned above, cooling arrangements may require an expansion unit that adjusts the pressure of the high pressure side to the pressure of the low pressure side. Potential shortcomings of capillary tubes, if not designed appropriately, are mentioned above. A further shortcoming of capillaries may be that the design of the capillary and the required amount of coolant are usually carried out experimentally. If operating parameters or system properties change, such as changes in the properties of the cooling fluid used, the systems no longer work as intended and has to be designed experimentally again.

[0090] Another realization for an expansion unit is a thermal expansion valve (in particular with internal or external pressure compensation), which may regulate the superheating at the evaporator outlet. These expansion valves may require a region at the end of the evaporator unit where the vaporous cooling fluid can continue to absorb energy and may thus superheat. This may require a significant area of the evaporator unit, as these expansion valves may for instance try to adjust a superheating of 8K. In general, the control range of these expansion valve may range from 4K to 12K superheating. The mentioned superheating surface may for instance occupy 30% of the evaporator unit and can therefore no longer contribute significantly to the cooling capacity. The result is a significantly reduced cooling capacity with a given installation space.

[0091] Furthermore, pressure-regulating expansion valves, which regulate the evaporation pressure, may be used. These may have the advantage that the evaporation temperature can be limited downwards and thus the evaporator unit may remain ice-free or sensitive elements to be cooled are not affected. A major disadvantage of these valves is their operation in a partial load range. If a temperature of the cooling room is close to the evaporation temperature, only a reduced energy input into the evaporator unit takes place. As a result, the boiling distance in the evaporator unit may be extended and the superheating of the suction gas in the evaporator unit may decrease. As a result, the evaporation section in the evaporator unit may shift towards the compressor unit. If the amount of heat supplied to the -23 -evaporator unit is too low, liquid cooling fluid may be sucked in by the compressor unit as a result. This may lead to a damage of the compressor unit. Insufficient superheating of suction gas can result in compression into a wet steam area, especially with R600a.

[0092] Another way to control superheating is through electronic expansion valves. These motorized valves may allow a minimum superheating of 2K and may thus achieve high cooling capacities with a given evaporator size. However, a sensor may be needed to measure the temperature at the evaporator output. In addition, a complex electronic control may be needed. Furthermore, electronic expansion valves may be not available for all cooling fluids and power ranges.

[0093] According to an exemplary embodiment of the second aspect, a cooling arrangement may be provided for adapting the mass flow of cooling fluid in a cooling path as required or desired, using a pressure-regulating expansion valve for an expansion unit. Hence, exemplary embodiments may overcome the conventional shortcoming of liquid beats in the compressor unit by providing a cooling arrangement with evaporation pressure regulating expansion unit. This may be advantageous in particular in a partial load range or in the event of insufficient energy input into the evaporator unit during operation. In addition, such a cooling arrangement may allow a simple control of cooling capacity.

[0094] Advantageously, the control or regulation architecture of embodiments of the second aspect may prevent liquid shocks when using pressure-regulating expansion valves in partial load operation. Furthermore, a corresponding cooling arrangement may have a high robustness against fluctuating environmental conditions, fluctuations in the properties of cooling fluid oil or oil/cooling fluid pairing and their mass fractions, and/or fluctuations in the amount of cooling fluid (in particular during filling and in case of loss during operation). Furthermore, embodiments of the second aspect may limit evaporation temperature downwards in all load cases and may thereby prevent undesired icing. Furthermore, exemplary embodiments of the second aspect may provide a simple cooling control by controlling superheating characteristics. Hence, even for small cooling arrangements, an efficient way of embodying expansion unit and evaporation unit may be provided.

[0095] Advantageously, an exemplary embodiment of the second aspect may -24 -enable an efficient utilization of the evaporator unit due to a possible short evaporation distance. Furthermore, the range of applications with regard to cooling-related environmental conditions may be extended. Moreover, a very high cooling capacity may be achieved. Beyond this, an efficient operation of the cooling arrangement may be ensured. Further advantageously, a small or even minimum superheating may be feasible. Since a load-dependent reduction of superheating may be accomplished by an exemplary embodiment, a high cooling capacity may be achieved. Due to a possible load-dependent increase in superheating, a highly efficient operation at partial load may be ensured as well. Furthermore, a simple control electronics and a simple sensor system may be implemented which may reduce the effort of manufacturing the cooling arrangement. Since exemplary embodiments of the second aspect may be operated with full and partial load, a corresponding cooling arrangement may be constructed in a simple and compact way. In contrast to conventional approaches, a significantly increased operational safety may be achieved.

[0096] Further advantageously, exemplary embodiments of the first aspect and of the second aspect of the invention may allow to apply compressor-based cooling in perfect compliance with requirements of analytical devices such as an HPLC. Such a compliance may be achieved with respect to cooling power, accuracy and long-term stability. Furthermore, such embodiments are compatible with a moderate energy consumption which keeps the ecological footprint small.

[0097] Referring now in greater detail to the drawings, Figure 1 depicts a general schematic of a sample separation apparatus-type analytical device 10 according to an exemplary embodiment of the invention. A fluid drive 20 (such as a piston pump) receives a mobile phase from a solvent supply 25 via degassing unit 27, which degases and thus reduces the amount of dissolved gases in the mobile phase. The fluid drive 20 drives the mobile phase through a separation unit 30 (such as a chromatographic column) comprising a stationary phase. A sampler or injector 40, implementing a fluidic valve 95, can be provided between the fluid drive 20 and the separation unit 30 in order to subject or add (often referred to as sample introduction) a sample fluid into the mobile phase so that a fluidic sample and mobile phase may be provided towards a separation path where actual sample separation occurs. Before loading the fluidic sample into injector 40, the fluidic sample may be contained -25 -in a sample container 130, for instance in a sample rack (not shown). The stationary phase of the separation unit 30 is configured for separating compounds of the sample liquid. A detector 50 is provided for detecting separated compounds of the sample fluid. A fractionation unit 60 can be provided for outputting separated compounds of sample fluid in sample containers 130.

[0098] While the mobile phase can be comprised of one solvent only, it may also be mixed from plural solvents. Such mixing might be a low pressure mixing executed by a mixer 97 provided upstream of the fluid drive 20, so that the fluid drive 20 already receives and pumps the mixed solvents as the mobile phase. Alternatively, the fluid drive 20 may comprise plural individual pumping units, with plural of the pumping units each receiving and pumping a different solvent or mixture, so that the mixing of the mobile phase (as received by the sample separation unit 30) occurs at high pressure and downstream of the fluid drive 20 (or as part thereof). The composition of the mobile phase may be kept constant over time, the so called isocratic mode, or varied over time, the so called gradient mode.

[0099] A data processing unit or control unit 70, which can be a PC or workstation, may be coupled (as indicated by the dotted arrows) to one or more of the devices in the analytical device 10 in order to receive information and/or control operation. For example, the control unit 70 may control operation of the fluid drive 20 (for example setting control parameters) and receive therefrom information regarding the actual working conditions (such as output pressure, etc. at an outlet of the pump). Optionally, the control unit 70 may also control operation of the solvent supply 25 (for example setting the solvent/s or solvent mixture to be supplied) and/or the degassing unit 27 (for example setting control parameters and/or transmitting control commands) and may receive therefrom information regarding the actual working conditions (such as solvent composition supplied over time, vacuum level, etc.). The control unit 70 may further control operation of the sampling unit or injector 40 (for example controlling sample injection or synchronization sample injection with operating conditions of the fluid drive 20). The separation unit 30 may also be controlled by the control unit 70 (for example selecting a specific flow path or column, setting operation temperature, etc.), and send -in return -information (for example operating conditions) to the control unit 70. Accordingly, the detector 50 may be controlled by the control unit 70 (for example with respect to spectral or wavelength settings, setting time constants, -26 -start/stop data acquisition), and send information (for example about the detected sample compounds) to the control unit 70. The control unit 70 may also control operation of the fractionation unit 60 (for example in conjunction with data received from the detector 50) and provides data back. Moreover, it is possible that the control unit 70 controls operation of the respective cooling arrangement 100 for cooling fluidic sample in a respective sample container 130.

[00100] As already mentioned, Figure 1 shows a sample container 130 containing a fluidic sample to be aspirated by the injector 40 for subsequent injection between the fluid drive 20 and the sample separation unit 30. Moreover, Figure 1 illustrates different sample containers 130 into which different fractions of the separated fluidic sample are inserted by the fractionation unit 60. Both in the injector 40 and in the fractionation unit 60 cooling of fluidic sample and sample containers 130 may be desired or required. The subsequently described embodiments focus predominantly on sample cooling in an injector 40 according to exemplary embodiments of the invention. However, corresponding considerations apply to sample handling in the fractionation unit 60. As shown in Figure 1, a corresponding cooling arrangement 100 may be implemented in the injector 40 and/or in the fractionation unit 60. Each of said cooling arrangements 100 can for instance be embodied as will be described below referring to Figure 2 to Figure 5.

[00101] Figure 2 shows a schematic view of a cooling arrangement 100 according to an exemplary embodiment of the invention.

[00102] The illustrated cooling arrangement 100 for an analytical device 10 for analyzing a fluidic sample (such as the one shown and Figure 1) comprises a cooling room 102 coupled with a cooling path 126 along which a cooling fluid circulates. The cooling room 102 may be a chamber assigned to injector 40 or fractionation unit 60 according to Figure 1 in which one or more sample containers 130 or one or more corresponding sample racks may be arranged for sample cooling. Cooling path 126 may be a closed loop circumferential fluidic path along which a cooling fluid or coolant may circulate, in particular driven by one or more pumps. For example, the cooling fluid may comprise isobutane, optionally comprising additives. For example, the cooling fluid R600a may be used. According to Figure 2, the cooling fluid circulates along cooling path 126 in a counter clockwise direction. A skilled person will -27 -understand that a cooling arrangement 100 may also operate with a cooling fluid circulating in a clockwise direction along a cooling path 126 (not shown).

[00103] Again referring to Figure 2, an evaporator unit 104 is provided for evaporating cooling fluid when the latter is in a liquid phase. The evaporator unit 104 is integrated in the cooling path 126. As shown, the evaporator unit 104 is thermally coupled with the cooling room 102, for instance is arranged inside of the cooling room 102. For instance, the evaporator unit 104 may comprise a heat exchanger which receives thermal energy from the cooling room 102 for evaporating cooling fluid. As a result, the cooling room 102 and material inside thereof will be cooled.

[00104] Figure 2 also shows that the cooling arrangement 100 comprises a condenser unit 106 for condensing cooling fluid, as refrigerant, evaporated in the evaporator unit 104. The condenser unit 106 is integrated in the cooling path 126. The condenser unit 106 may comprise a heat exchanger 134 at which heated gaseous cooling fluid dissipates thermal energy towards an environment and is thereby returned to a lower temperature and condenses into a liquid phase. A gas flow generated by a controllable ventilator 116 may be directed towards the heat exchanger 134 to control a degree of heat exchange. The stronger the gas flow created by ventilator 116, the more pronounced will be the heat exchange between cooling fluid and heat exchanger 134, and vice versa. Directly downstream of the condenser unit 106, the cooling fluid may be liquid and at a relatively high pressure.

[00105] Moreover, the cooling arrangement 100 of Figure 2 comprises a compressor unit 108 for compressing cooling fluid, as refrigerant, flowing from the evaporator unit 104 towards the condenser unit 106. The compressor unit 108 is integrated in the cooling path 126. For example, the compressor unit 108 may be a piston stroke compressor driven by a drive unit 132 such as a motor. However, other kinds of compressor units are known by a person skilled in the art and can be used in other embodiments as well. The drive unit 132 may be driven with very variable speed to thereby adjust the amount according to which the compressor unit 108 compresses the cooling fluid which has been at least partially evaporated by evaporator unit 104.

An increased speed increases the intake volume. The density of the aspirated gas may then result in the suctioned amount of gas per time. Due to the described design of the cooling arrangement 100, the construction of the compressor unit 108 can be -28 -compact.

[00106] Beyond this, the cooling arrangement 100 comprises an expansion unit 110 for expanding cooling fluid flowing from the condenser unit 106 back towards the evaporator unit 104. The expansion unit 110 is integrated in the cooling path 126. The condenser unit 106 is integrated in the cooling path 126. Advantageously, the expansion unit 110 may be configured, in the embodiment of Figure 2, as a simple flow restriction, such as a capillary having a smaller interior cross-section than the rest of the fluidic conduits of the cooling path 126. No active control of expansion unit 110 is necessary under these circumstances, and the construction of the expansion unit 110 may be simple and compact. Cooling fluid which has been liquefied by condenser unit 106 can be expanded by expansion unit 110, for instance can be adiabatically expanded.

[00107] In other embodiments, it is however also possible that the expansion unit 110 comprises a thermal expansion valve or a motor-driven expansion valve. It is also possible that the expansion unit 110 is embodied as a manual valve. Such a manual valve may be set and fixed to an appropriate opening degree, for instance at a factory side.

[00108] After passing expansion unit 110, the cooling fluid will be reintroduced into the evaporator unit 104 in the cooling room 102, so that the cooling mechanism can be repeated continuously in a cyclic manner. The expansion unit 110 (for example a capillary) may provide a pressure difference between a high-pressure side and a low-pressure side. The evaporation and thus the expansion of the coolant may then take place in the evaporator unit 104.

[00109] Advantageously, the cooling arrangement 100 according to Figure 2 comprises a condenser temperature controller 112 configured for controlling a condenser temperature of the cooling fluid at the condenser unit 106 to thereby control temperature and pressure of the cooling fluid being thermally coupled with the condenser unit 106. Descriptively speaking, the control algorithm of the condenser temperature controller 112 may be configured for emulating, together with the capillary-type expansion unit 110, a function of an evaporator expansion valve (the latter being substituted by the capillary-type expansion unit 110). By taking this measure, it can be ensured that the re-liquefied cooling fluid may be brought to a -29 -desired working temperature and pressure. Consequently, the mass flow of the cooling fluid may be adjusted in particular to comply with a desired cooling power. This may also make it possible to construct the expansion unit 110 in the above-described simple way, for instance as capillary or other flow restriction. For example, the condenser temperature controller 112 may be a processor, a plurality of processors, or part of a processor. The condenser temperature controller 112 may be embodied in software and/or in hardware. It is also possible that the condenser temperature controller 112 forms part of the control unit 70 shown in Figure 1.

[00110] As illustrated, the condenser temperature controller 112 may be configured for controlling the condenser temperature by a control signal applied at an outlet of the condenser temperature controller 112. Said control signal is applied to ventilator 116 with controllable speed being arranged for impacting heat exchanger 134 of the condenser unit 106 under control of the condenser temperature controller 112.

[00111] The control performed by the condenser temperature controller 112 may be based on a temperature, tc, of the cooling fluid sensed by a temperature sensor 118 arranged at an outlet of the condenser unit 106 or between the condenser unit 106 and the expansion unit 110. Said temperature, tc, is provided at an inlet of the condenser temperature controller 112.

[00112] Furthermore, the condenser temperature controller 112 is configured for controlling the condenser temperature based on a condenser temperature set point, tc,, being indicative of a target cooling power of the cooling arrangement 100. Said condenser temperature set point, tc,sp, is applied to a further inlet of the condenser temperature controller 112. The condenser temperature set point, tc., is provided to the condenser temperature controller 112 by a superheat controller 114. Said superheat controller 114 can be configured for controlling a superheating characteristic of the cooling fluid. By evaporation in evaporator unit 104, at least part of the cooling fluid may be superheated, i.e. may be rendered gaseous and may be brought to a temperature above the boiling point of the cooling fluid. This superheating characteristic can be defined by the superheat controller 114. For example, the superheat controller 114 may be a processor, a plurality of processors, or part of a processor. It is also possible that the superheat controller 114 forms part of the control unit 70 shown in Figure 1. The superheat controller 114 may be embodied in software -30 -and/or in hardware.

[00113] More specifically, the superheat controller 114 may be configured for determining the condenser temperature set point, tcsp, based on the following parameters (i), (ii), (iii), which may be applied to three inlets of the superheat controller 114: [00114] (i) a temperature, to, of the cooling fluid in the cooling room 102 upstream of the evaporator unit 104 as sensed by a further temperature sensor 120. The temperature, to, may be denoted as evaporation temperature.

[00115] (ii) a temperature, to2, of the cooling fluid in the cooling room 102 10 downstream of the evaporator unit 104 as sensed by yet another temperature sensor 122. The temperature, to2, may be denoted as suction gas temperature.

[00116] (iii) a superheating temperature set point tsh.sp, indicative of a target superheating temperature of the cooling fluid. The superheating temperature set point tsh.sp, may be a reference or target value which may be adjusted depending on a desired cooling power of the cooling arrangement 100.

[00117] Moreover, the cooling arrangement 100 comprises an evaporator temperature controller 124 configured for controlling a temperature of the cooling fluid downstream of the expansion unit 110, in particular during evaporation by the evaporator unit 104. As soon as evaporation has occurred and further energy is supplied, the overheating of the cooling fluid begins. A goal may be to regulate the temperature during evaporation. For example, the evaporator temperature controller 124 may be a processor, a plurality of processors, or part of a processor. It is also possible that the evaporator temperature controller 124 forms part of the control unit 70 shown in Figure 1. The evaporator temperature controller 124 may be embodied in software and/or in hardware. The evaporation temperature controller 124 may be configured for controlling or adjusting the temperature of the cooling fluid downstream of the expansion unit 110, in particular during evaporation in evaporation unit 104 by controlling the compressor unit 108. For this purpose, the evaporation temperature controller 124 may transmit a control signal at its outlet to drive unit 132 (for example a motor) for driving the compressor unit 108. -31 -

[00118] More specifically, the evaporation temperature controller 124 may be configured for controlling the temperature of the cooling fluid downstream of the expansion unit 110, in particular during evaporation, based on the following two parameters (I), (II) each applied at a respective inlet of the evaporation temperature controller 124: [00119] (I) the temperature, to, of the cooling fluid in the cooling room 102 upstream of the evaporator unit 104 as sensed by further temperature sensor 120.

[00120] (II) an evaporator temperature set point, to,, indicative of an evaporation temperature of the cooling fluid. The evaporator temperature set point, to.sp, may be set to a temperature value ensuring that the evaporator unit 104 is prevented from icing. As a result, protection of the sample against icing can be achieved, and a continuous operation without defrost cycle can be made possible..

[00121] Hence, the embodiment of Figure 2 provides a control mechanism allowing a control of the superheating of gaseous cooling fluid sucked in by the compressor unit 108 in the cooling arrangement 100 with a capillary tube as expansion unit 110.

[00122] The superheating control accomplished according to Figure 2 may comprise the following components: [00123] -The condenser unit 106 with speed-controllable ventilator 116, sensor 118 for detecting the condensing temperature, tc, and a temperature control loop provided by condenser temperature controller 112 that regulates the condensing temperature to condensing temperature set point, tc,sp, by controlling the ventilator 116 accordingly.

[00124] -The compressor unit 108 which may preferably be operated in accordance with an adjustable drive speed. Alternatively, a compressor unit 108 with fixed speed 25 may be used as well. In yet another embodiment, a compressor unit 108 may be used that can gradually change its speed.

[00125] -The evaporator unit 104 with sensor 120 to detect the boiling temperature, to, of the cooling fluid, further sensor 122 for detecting a cooling fluid temperature, to2, at the output of the evaporator unit 104, and evaporator temperature controller 124 that regulates the boiling temperature, to, to boiling temperature setpoint, to,sp, by -32 -controlling the speed of the drive unit 132 driving the compressor unit 108.

[00126] -The superheat controller 114 receiving superheating setpoint, tsh.sp, which may be a fixed value or may be otherwise determined (see for example Figure 3 and Figure 4). Furthermore, superheat controller 114 may be supplied with the actual value of the boiling temperature, to, (or a measure thereof) of the cooling fluid, and the temperature of the cooling fluid, t02, (or a measure thereof) at the outlet of the evaporator unit 104. In terms of its control or regulation, the superheat controller 114 may determine a setpoint of the condensing temperature, tc,sp, which can be supplied as an input to condenser temperature controller 112.

[00127] -The expansion unit 110 which may be embodied as a simple capillary tube, or another type of flow restriction.

[00128] The control of superheating (t02 -to) may make use of the dependence of the mass flow through the capillary tube on the pressure difference above the capillary tube. The condensing pressure may be directly related to the associated condensing temperature, tc, the evaporation pressure may be directly related to the evaporation temperature, to. By influencing these temperatures, the pressure in the respective component can therefore be changed as well in a characteristic way. By the mass flow, the amount of cooling fluid evaporating in the evaporator unit 104 can be influenced, and thus the length of the boiling distance on the evaporator unit 104.

From the end of evaporation, the superheating of the sucked-in gaseous cooling fluid finally takes place. By evaporation and in particular by superheating, the cooling fluid may become completely gaseous and free of a liquid contribution.

[00129] Figure 2 illustrates the cooling arrangement 100 with components contributing to control superheating. This cooling arrangement 100 may operate according to the following regulations: [00130] -Control of the evaporation pressure/temperature: The evaporation pressure may be controlled by the evaporation temperature controller 124. This may involve the setpoint of the evaporation temperature, to,sp, as well as the actual evaporation temperature value, to. Depending on the difference, to,sp -to, the setpoint of the compressor speed may be increased or decreased. If the evaporation temperature is too low, the speed of the drive unit 132 for driving the compressor unit -33 - 108 may be reduced. The setpoint of the evaporation temperature, to, can be a fixed value or can be determined by another control device (compare for instance Figure 3 and Figure 4).

[00131] -Superheating control: If the superheating temperature, to2 -to, deviates from the superheating setpoint, to,sp, the superheat controller 114 may determine a new liquefaction temperature setpoint, tc,sp. If the actual value of the superheating is greater than the setpoint, the superheat controller 114 may determine a higher liquefaction temperature setpoint for the condenser temperature controller 112, and vice versa. Here, too, the setpoint of the superheating can be a fixed value, or be determined by a further control (see for instance Figure 3).

[00132] -Control of the condensing pressure/temperature: The condenser temperature controller 112 may regulate the condensing temperature and may use for this purpose the setpoint, tc.sp, and the actual value, tc, of the condensing temperature. If the actual value is above the setpoint, the speed of the ventilator 116 of the condenser unit 106 may be increased until the actual value corresponds to the setpoint, and vice versa.

[00133] In the following, additional details concerning superheating control will be explained. By extending the above described operation, properties of the cooling arrangement 100 and its operating state can be specifically influenced.

[00134] Figure 3 shows a portion of a cooling arrangement 100 according to an exemplary embodiment of the invention which may be based on the construction according to Figure 2. Referring to Figure 3, a simple control of the cooling room temperature will be explained. Figure 3 illustrates a temperature control of the cooling room 102 by adaptive determination of the setpoints of evaporation temperature and superheating.

[00135] The cooling arrangement 100 according to Figure 2 can be provided with components for controlling the temperature of the cooling room 102 according to Figure 3. For this purpose, a measurement of the cooling room temperature, tcR, in cooling room 102 may be carried out. This may be accomplished by still another sensor 138.

-34 - [00136] Next, control of evaporator temperature setpoint, to,sp, will be explained: With the difference between a setpoint, tca,sp, and the actual value, tca, of the cooling room temperature, a setpoint of the evaporation temperature, to,sp, can be determined. This may serve as a setpoint for the evaporating temperature controller 124 instead of a fixed value. The described control can be carried out by evaporation setpoint controller 140.

[00137] In the following, control of the evaporator performance will be explained: The cooling capacity of the evaporator unit 104 may depend on the temperature difference between the air to be cooled and the temperature of the evaporator surface, as well as the amount of the cold surface of the evaporator unit 104. This area may be largely determined by the route loaded with boiling cooling fluid. If more cooling capacity is required or desired at a given boiling temperature, the distance can be increased. The difference between the setpoint, tca,sp, and the actual value, tca, of the cooling room temperature can also be used to close the required cooling capacity.

Said actual value, tca, can be detected by temperature sensor 138 in the cool room 102. Accordingly, the length of the boiling distance in the evaporator unit 104 can be adjusted. A short boiling distance at a fixed evaporation temperature in the evaporator unit 104 may be achieved with a short boiling distance and thus low cooling capacity as well as a high superheating of the suction gas. A long boiling distance may be achieved with a higher cooling capacity, as well as a lower superheating of the suction gas. A cooling power controller 142 can be used to determine a setpoint for superheating, tsh,sp. This may serve as input setpoint for the superheat controller 114.

[00138] Figure 4 shows a portion of a cooling arrangement 100 according to an exemplary embodiment of the invention which may be based on the construction according to Figure 2. Referring to Figure 4, control of the cooling room temperature by enhanced superheating controller 144 will be explained.

[00139] The enhanced superheat controller 144 may control the electrical power consumption by a compressor power controller 146. The compressor power controller 146 allows a control of the electrical power consumption of the compressor unit 108.

The power consumption may serve as a measure of the actual load state of the cooling arrangement 100. The power consumption may be determined by the engine speed and the engine torque. The engine torque may be directly related to the -35 -necessary work to compress a sucked-in volume from the intake pressure to the output volume under the prevailing pressure in the high-pressure side of the cooling arrangement 100. Accordingly, it may be possible to directly control the condenser temperature controller 112 in Figure 2 via the setpoint of the condensing temperature, tc,so. The compressor power controller 146 may receive its compressor power setpoint, Pam-Ipso, from the superheat controller 114. As a further input signal, a measured electrical power consumption, Pan, of the compressor unit 108 may be provided. The parameter can be used to define limits for the upper and lower power consumption, P compfarge, of the compressor unit 108. By the upper limit, the power supply can be effectively protected against overload.

[00140] According to Figure 4, the superheat controller 114 of Figure 2 may be extended. The superheating to be set is not determined according to a simple setpoint in Figure 4, but taking into account a parameter set. The basic mode of action according to Figure 2, where the superheating is regulated by temperature measurements on the evaporator unit 104 and corresponding control of the condensing temperature, may be retained.

[00141] By comparing the set temperature setpoint, tcn.sp, in the cooling room 102 with the actual temperature, tcn, in the cooling room 102, a cooling room superheat demand estimator 148 may generate a superheating demand cooling room signal 150 that maps the cooling capacity requirement. With this signal and the signals evaporation temperature, to, and suction gas temperature, to2, the superheat controller 114 may generate setpoint, Pcomp,so, for the necessary compressor power, Pcomp. As additional parameters, a minimum superheat setpoint, tsh.sp.rnin, and a maximum superheat setpoint, tsh,sp,max, may be taken into account to protect the compressor unit 108.

[00142] Figure 5 shows a schematic view of a cooling arrangement 100 according to another exemplary embodiment of the invention.

[00143] Now referring to Figure 5, the illustrated cooling arrangement 100 for an analytical device 10 for analyzing a fluidic sample such as the one shown and Figure 1 comprises a cooling room 102 coupled with a cooling path 126 along which a cooling fluid circulates. The cooling room 102 may be a chamber assigned to injector 40 or fractionation unit 60 according to Figure 1 in which one or more sample containers -36 -or one or more corresponding sample racks may be arranged for sample cooling.

[00144] Cooling path 126 may be a closed loop circumferential fluidic path along which a cooling fluid or coolant may circulate. According to Figure 5, the cooling fluid circulates along cooling path 126 in a counter clockwise direction. According to an exemplary embodiment of invention, a cooling fluid or refrigerant can be moved along cooling path 126. The cooling fluid evaporates in the evaporator unit 104 and may be sucked in and compressed by compressor unit 108.

[00145] Again referring to Figure 5, an evaporator unit 104 is provided for evaporating cooling fluid when the latter is in a liquid phase. As shown, the evaporator unit 104 is thermally coupled with the cooling room 102, for instance is arranged inside of the cooling room 102. For instance, the evaporator unit 104 may be embodied as heat exchanger which receives the energy from the cooling room 102 for evaporating cooling fluid. As a result, the cooling room 102 and material inside thereof will be cooled.

[00146] Figure 5 also shows that the cooling arrangement 100 comprises a condenser unit 106 for condensing cooling fluid evaporated in the evaporator unit 104. The condenser unit 106 may comprise a heat exchanger 134 at which heated gaseous cooling fluid dissipates thermal energy towards an environment and is thereby returned to a lower temperature. A gas flow generated by a ventilator 116 may be directed towards the heat exchanger 134 to control a degree of heat exchange. The stronger the gas flow created by ventilator 116, the more pronounced will be the heat exchange between cooling fluid and heat exchanger 134. Directly downstream of the condenser unit 106, the cooling fluid may be liquid and at a relatively high pressure. However, the gas or air flow can also be a constant gas or air flow generated by a constant speed fan. For example, this gas or air flow can be regulated by mechanical actuators (for example flaps).

[00147] However, condenser unit 106 and evaporator unit 104 do not necessarily have to carry out an energy exchange with gas, such as air. For example, a corresponding heat exchanger may transfer its energy to a water circuit or absorb energy from a liquid carrier (for example a brine) at the evaporator unit 104. The condenser unit 106 can then be controlled in its temperature by the mass flow of the coolant. Instead of controlling a fan, the control of the speed of the driving pump or a -37 -valve or the position of a mixer can then be executed.

[00148] Moreover, the cooling arrangement 100 of Figure 5 comprises a compressor unit 108 for compressing cooling fluid flowing from the evaporator unit 104 towards the condenser unit 106. For example, the compressor unit 108 may be a piston stroke compressor driven by a drive unit 132 such as a motor. The drive unit 132 may be driven with very variable speed to thereby adjust the intake volume of the cooling fluid processed by the compressor unit 108, which has been at least partially evaporated by evaporator unit 104.

[00149] Beyond this, the cooling arrangement 100 comprises an expansion unit 110 for expanding cooling fluid flowing from the condenser unit 106 towards the evaporator unit 104. Advantageously, the expansion unit 110 of the embodiment of Figure 5 is embodied as an expansion valve being configured for regulating a pressure at the evaporator unit 104. By the pressure regulation performed by the expansion unit 110, a cooling power of the cooling arrangement 100 may be influenced as well. The valve of the expansion unit 110 may ensure an appropriate evaporation temperature. An adjustment of the cooling performance may then be carried out over an evaporation distance and by the amount of evaporated cooling fluid. This may be determined, in turn, by the speed of the compressor unit 108, which may have an impact on the intake volume.

[00150] For example, the expansion unit 110 can be configured for regulating the pressure at the evaporator unit 104 to a predefined constant value. This regulation logic may be obtained by using a purely passive expansion valve. It is also possible that the expansion unit 110 is configured for regulating a temperature at the evaporator unit 104 to a predefined constant value.

[00151] When the expansion valve of the expansion unit 110 is embodied as a passive valve, it may control the pressure of the cooling fluid in the evaporator unit 104 in a self-sufficient way, i.e. without an active control device such as a processor. In such a passive configuration, the expansion valve may for example comprise a spring-biased membrane (not shown). Such an expansion valve may be more or less opened and will thereby adjust the mass flow of cooling fluid passing the valve's restriction and thereby flowing between condensing unit 106 and evaporator unit 108.

-38 - [00152] A valve which may be implemented in the expansion unit 110 of the present embodiment may be for example an automatic expansion valve. Such a valve may be simply dependent on the pressure in the evaporator unit 104 and a preloaded counter spring. A diaphragm may be deflected by the pressure of the evaporator unit 104 and the back pressure of the environment (or a known enclosed volume) and a spring with adjustable preload. Therefore, the degree of opening of the valve may be determined by the difference in the spring force (in accordance with a spring characteristic and a displacement) on the one hand and the force through the diaphragm on this biased spring on the other hand The valve may be almost independent of the pressure of the condenser unit 106.

[00153] Descriptively speaking, the expansion unit 110 of Figure 5 may be an expansion throttle which adjusts itself depending on a pressure value at its outlet, i.e. at its fluidic interface with the evaporator unit 104. Thus, the expansion unit 110 of Figure 5 may be an expansion valve which may adjust the pressure at its outlet. By the opportunity of the expansion unit 110 to adjust the pressure at its outlet, it may be possible for operating the cooling arrangement 100 of Figure 5 in different load states. For example for cooling down a fluidic sample in a sample container 130 located in the cooling room 102, the cooling power may be higher than in a steady-state operation in which the sample container 130 in the cooling room 102 is already at its target temperature below ambient temperature. The present cooling power depends on the mass flow of cooling fluid. The valve of the expansion unit 110 may carry out an adjustment depending on how much refrigerant is sucked in by the compressor unit 108. The cooling capacity may therefore be determined by the valve and the operation of the compressor unit 108 (in particular its speed).

[00154] In another embodiment (not shown), the expansion valve of the expansion unit 110 may be an active expansion valve, which can be actively controlled by a control unit. The control unit may apply a control signal to the expansion valve defining the degree of opening thereof. A pressure control is indicated schematically in Figure 5 with reference sign 168.

[00155] Still referring to Figure 5, the cooling arrangement 100 comprises a superheat controller 114 which is configured for controlling a superheating temperature of the cooling fluid. In particular, the cooling fluid may be superheated in -39 -the section of the cooling path 126 between the evaporator unit 104 and the compressor unit 108. For instance, superheat controller 114 may be configured for controlling the superheating temperature to a predefined value. In order to achieve the adjustment of the superheating temperature for cooling fluid, the superheat controller 114 may adjust a speed of the drive unit 132 for driving the compressor unit 108 to thereby adjust a cooling power of the cooling arrangement 100. Thus, in the embodiment of Figure 5, the superheat controller 114 may also function as compressor speed controller.

[00156] As shown in Figure 5, the cooling arrangement 100 comprises a cooling room temperature controller 160 which is configured for controlling a temperature of the cooling room 102 by correspondingly controlling the superheat controller 114. More specifically, the cooling room temperature controller 160 may be configured for controlling the temperature of the cooling room 102 based on a comparison between a predefined cooling room target temperature and a sensed actual temperature in the cooling room 102. The superheat controller 114, in turn, may be configured for controlling the compressor unit 108 based on an output of the cooling room temperature controller 160 and a temperature of the cooling fluid in the cooling room 102 downstream of the evaporator unit 104 and sensed by a temperature sensor 122.

[00157] The superheat controller 114 of Figure 5 has two inlets. At a first inlet, a suction gas temperature, to2, is supplied to the superheat controller 114. The suction gas temperature, to2, can be measured by sensor 122 at the outlet of the evaporator unit 104. At a second inlet, a superheating setpoint, Ato,sp, is applied to the superheat controller 114. The superheating setpoint, Ato,sp, is provided at an outlet of cool room temperature controller 160. Descriptively speaking, the superheating setpoint, Ato,sp, may indicate whether more or less cooling power is needed. The cool room temperature controller 160 may determine the superheating setpoint, Ato,sp, based on two values applied to two inlets of the cool room temperature controller 160. At a first inlet of the cool room temperature controller 160, an actual cold room temperature, tcn, measured in the cold room 102 by temperature sensor 138 is provided. At a second inlet of the cool room temperature controller 160, a cold room temperature setpoint, tcn,sp, is provided. The cold room temperature setpoint, tcn,sp, may be a fixed reference or target value. The superheat controller 114 may also know a temperature at the inlet of the evaporator unit 104 (denoted as, to, in Figure 2). This temperature -40 -may be pre-known or may be sensed by a sensor 120 (not shown in Figure 5).

[00158] Advantageously, the cooling arrangement 100 according to Figure 5 comprises a condenser temperature controller 112 configured for controlling a temperature at the condenser unit 106 based on a comparison between a predefined target temperature and a temperature of the cooling fluid between the condenser unit 106 and the expansion unit 110. Said condenser temperature controller 112 may be configured for controlling a condenser temperature of the cooling fluid at the condenser unit 104 to thereby control temperature and pressure of the cooling fluid. As shown, the condenser temperature controller 112 may be configured for controlling the condenser temperature by a control signal applied at an outlet of the condenser temperature controller 112. Said control signal is applied to ventilator 116 with controllable speed being arranged for impacting the condenser unit 106 under control of the condenser temperature controller 112. The control performed by the condenser temperature controller 112 may be based on temperature, to, of the cooling fluid sensed by a temperature sensor 118 arranged at an outlet of the condenser unit 106 or between the condenser unit 106 and the expansion unit 110. Said temperature, to, is provided at an inlet of the condenser temperature controller 112.

[00159] Furthermore, the condenser temperature controller 112 is configured for controlling the condenser temperature based on a condenser temperature set point, to,, being indicative of a target cooling power of the cooling arrangement 100. Said condenser temperature set point, to,, may be applied to a further inlet of the condenser temperature controller 112. The condenser temperature set point, tc,sp, may be a fixed reference or target value according to Figure 5.

[00160] Hence, Figure 5 shows a cooling arrangement 100 with control components and sensors configured for executing a control method for controlling the mass flow of the cooling fluid implementing the described expansion valve that regulates the evaporation pressure.

[00161] The cooling arrangement 100 of Figure 5 comprises the following components: [00162] -Condenser unit 106 with speed-controllable ventilator 116, sensor 118 for detecting the condensing temperature, to, and a temperature control that regulates -41 -the liquefaction temperature to the condensing temperature, tc,sp, by controlling the ventilator 116 [00163] -Speed controllable compressor unit 108 [00164] -Superheat controller 114 for controlling superheating of cooling fluid [00165] -Evaporator unit 104 with sensor 122 for detecting the temperature, to2, of the cooling fluid at the evaporator output (which may be denoted as suction gas), a control device that regulates the actual value of the suction gas temperature, to2, to a setpoint of the suction gas temperature, tozsp, by controlling the speed of the drive unit 132 of the compressor unit 108 accordingly. The value, t02.sp, may result from the sum of the boiling temperature, to, of the cooling fluid kept constant by the expansion valve added to a necessary superheating, Ato,sp, determined by the control device (to2= to + Ato,sp).

[00166] -Temperature control of the cooling room 102: Sensor 138 for detecting the temperature of the cooling room 102 with appropriate control device that regulates the temperature, tcn, of the cooling room 102 to a setpoint, tcn,sp, set by the user by determining the setpoint, Ato,sp, and applying it to the control device for controlling cooling fluid superheating at the outlet of the evaporator unit 104.

[00167] -Pressure-regulating expansion valve of expansion unit 110, which keeps the pressure and thus the boiling temperature, to, of the cooling fluid in the evaporator unit 104 constant via the cooling fluid supply.

[00168] The valve-type expansion unit 110 may regulate the pressure in the evaporator unit 104 by increasing or reducing the restriction depending on the pressure in the evaporator unit 104. If the amount of cooling fluid sucked in by the compressor unit 108 changes, the valve-type expansion unit 110 may adjust to keep the pressure stable. If the compressor unit 108 has more cooling fluid, the valve-type expansion unit 110 may reduce its restriction. This may increase the cooling capacity of the evaporator unit 104, as more cooling fluid is available for evaporation. If the temperature difference between the cooling room 102 and the evaporator unit 104 remains constant, the length of the evaporation distance changes. If the evaporation distance is extended, the evaporator surface area available for superheating the -42 -suction gas may be reduced. The superheating (Ato2= to2 -to) of the suction gas falls. The arrangement and regulation of the embodiment according to Figure 5 may take advantage of this connection by regulating the output temperature of the gas from the evaporator unit 104 and thus regulating the superheating of the suction gas on the one hand and the cooling capacity on the other hand. The value (Ato2) for this may be determined by cold room temperature controller 160 that compares, tCR,sp, to the setpoint, tcR, with the measured actual temperature value. Preferably, the value Ato2 shall move within limits being appropriate for the cooling arrangement 100.

[00169] It should be noted that the term "comprising" does not exclude other elements or features and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined. It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

-43 -

Claims

CLAIMS1. A cooling arrangement (100) for an analytical device (10) for analyzing a fluidic sample to be cooled, wherein the cooling arrangement (100) comprises: a cooling room (102) coupled with a cooling path (126) along which a cooling fluid circulates; an evaporator unit (104) for evaporating cooling fluid, wherein the evaporator unit (104) is thermally coupled with the cooling room (102); a condenser unit (106) for condensing cooling fluid evaporated in the evaporator unit (104); a compressor unit (108) for compressing cooling fluid flowing from the evaporator unit (104) towards the condenser unit (106); an expansion unit (110) for expanding cooling fluid flowing from the condenser unit (106) towards the evaporator unit (104); and a condenser temperature controller (112) configured for controlling a condenser temperature to control temperature and pressure of the cooling fluid.
2. The cooling arrangement (100) according to claim 1, wherein the condenser temperature controller (112) is configured for controlling the condenser temperature based on at least one temperature of the cooling fluid next to the condenser unit (106).
3. The cooling arrangement (100) according to claim 2, comprising at least one of the following features: wherein the at least one temperature of the cooling fluid comprises at least one of a temperature of the cooling fluid at an inlet of the condenser unit (106), at an outlet of the condenser unit (106) and/or between the condenser unit (106) and the expansion unit (110); comprising a temperature sensor (118) for sensing and supplying to the condenser temperature controller (112) temperature information indicative of the at least one temperature of the cooling fluid next to the condenser unit (106).
4. The cooling arrangement (100) according to any of claims 1 to 3, wherein the condenser temperature controller (112) is configured for controlling the condenser -44 -temperature based on a condenser temperature set point, in particular to the condenser temperature set point, indicative of a target cooling power of the cooling arrangement (100).
5. The cooling arrangement (100) according to claim 4, wherein the condenser temperature set point is provided by a superheat controller (114) configured for controlling a superheating characteristic of the cooling fluid.
6. The cooling arrangement (100) according to claim 5, wherein the superheat controller (114) is configured for determining the condenser temperature set point based on at least one of the following parameters, in particular based on each of the following parameters: a temperature of the cooling fluid in the cooling room (102) upstream of the evaporator unit (104), in particular sensed by a temperature sensor (120); a temperature of the cooling fluid in the cooling room (102) downstream of the evaporator unit (104), in particular sensed by a temperature sensor (122); and a superheating temperature set point indicative of a superheating target temperature of the cooling fluid.
7. The cooling arrangement (100) according to any of claims 1 to 6, comprising at least one of the following features: wherein the expansion unit (110) comprises or consists of an evaporator capillary; wherein the condenser temperature controller (112) is configured for emulating a function of an evaporator expansion valve; wherein the expansion unit (110) is a non-adjustable entity; comprising a ventilator (116) arranged for impacting a heat exchanger (134) of the condenser unit (106) and being controllable by the condenser temperature controller (112).
8. The cooling arrangement (100) according to any of claims 1 to 7, comprising an evaporator temperature controller (124) configured for controlling a temperature of the cooling fluid downstream of the expansion unit (110).
-45 - 9. The cooling arrangement (100) according to claim 8, wherein the evaporation temperature controller (124) is configured for controlling the temperature of the cooling fluid downstream of the expansion unit (110) by controlling the compressor unit (108).
10. The cooling arrangement (100) according to claim 8 or 9, wherein the evaporation temperature controller (124) is configured for controlling the temperature of the cooling fluid downstream of the expansion unit (110)based on at least one of the following parameters, in particular based on each of the following parameters: a temperature of the cooling fluid in the cooling room (102) upstream of the evaporator unit (104), in particular sensed by a temperature sensor (120); and an evaporator temperature set point indicative of an evaporation target temperature of the cooling fluid.
11. The cooling arrangement (100) according to any of claims 1 to 10, comprising at least one temperature sensor (118, 120, 122) for sensing sensor data indicative of at least one temperature of the circulating cooling fluid, in particular upstream and/or downstream of the evaporator unit (104) in the cooling room (102) and/or downstream of the condenser unit (106).
12. A cooling arrangement (100) for an analytical device (10) for analyzing a fluidic sample to be cooled, wherein the cooling arrangement (100) comprises: a cooling room (102) coupled with a cooling path (126) along which a cooling fluid circulates; an evaporator unit (104) for evaporating cooling fluid, wherein the evaporator unit (104) is thermally coupled with the cooling room (102); a condenser unit (106) for condensing cooling fluid evaporated in the evaporator unit (104); a compressor unit (108) for compressing cooling fluid flowing from the evaporator unit (104) towards the condenser unit (106); and an expansion unit (110) for expanding cooling fluid flowing from the condenser unit (106) towards the evaporator unit (104); wherein the expansion unit (110) is configured for regulating a pressure at the -46 -evaporator unit (104).
13. The cooling arrangement (100) according to claim 12, comprising at least one of the following features: configured for controlling or influencing a cooling power by said pressure regulation; wherein the expansion unit (110) is configured as expansion valve, in particular as active or passive expansion valve; wherein the expansion unit (110) is configured for regulating the pressure at the evaporator unit (104) to a predefined constant value; wherein the expansion unit (110) is configured for regulating a temperature at the evaporator unit (104), in particular to a predefined constant value; comprising a superheat controller (114) configured for controlling a superheating characteristic of the cooling fluid, wherein in particular the superheat controller (114) is configured for controlling a speed of a drive unit (132) for driving the compressor unit (108) to thereby adjust a cooling power of the cooling arrangement (100); comprising a condenser temperature controller (112) configured for controlling a temperature at the condenser unit (106) based on a comparison between a predefined target temperature and a temperature of the cooling fluid at an outlet of the condenser unit (106) and/or between the condenser unit (106) and the expansion unit (110).
14. The cooling arrangement (100) according to any of claims 12 to 13, comprising a cooling room temperature controller (160) configured for controlling a temperature of the cooling room (102), in particular by correspondingly controlling the superheat controller (114).
15. The cooling arrangement (100) according to claim 14, comprising at least one of the following features: wherein the cooling room temperature controller (160) is configured for controlling the temperature of the cooling room (102) based on a comparison between a predefined cooling room target temperature and a sensed actual temperature in the cooling room (102); -47 -wherein the superheat controller (114) is configured for controlling the compressor unit (108) based on an output of the cooling room temperature controller (160) and a temperature of the cooling fluid in the cooling room (102) downstream of the evaporator unit (104), in particular sensed by a temperature sensor (122).
16. An analytical device (10) for analyzing a fluidic sample, wherein the analytical device (10) comprises a cooling arrangement (100) according to any of claims 1 to 15 for cooling the fluidic sample.
17. The analytical device (10) according to claim 16, configured as sample separation apparatus for separating the fluidic sample and comprising: a fluid drive (20) for driving the fluidic sample and/or a mobile phase in which the fluidic sample is injected; and a sample separation unit (30) for separating the fluidic sample in the mobile phase.
18. The analytical device (10) according to claim 16 or 17, comprising at least one of the following features: wherein the cooling arrangement (100) is configured for cooling a sample container (130), in particular of a sample rack, containing the fluidic sample to be analysed; comprising an injector (40) implementing the cooling arrangement (100) and being configured to inject the fluidic sample into mobile phase for analyzing the fluidic sample; comprising a fractionation unit (60) implementing the cooling arrangement (100) and being configured to collect analyzed fluidic sample; the analytical device (10) is configured as a chromatography sample separation apparatus, in particular a liquid chromatography sample separation apparatus, a gas chromatography sample separation apparatus or a supercritical fluid chromatography sample separation apparatus; the sample separation unit (30) is a chromatographic separation column; comprising a detector (50) configured to detect the separated fluidic sample; comprising a degassing apparatus (27) for degassing at least part of the -48 -mobile phase.
19. A method of cooling a cooling room (102) by circulating cooling fluid along a cooling path (126) in an analytical device (10) for analyzing a sample, wherein the 5 method comprises: evaporating cooling fluid by an evaporator unit (104) which is thermally coupled with the cooling room (102); condensing cooling fluid evaporated in the evaporator unit (104) by a condenser unit (106); compressing cooling fluid when flowing from the evaporator unit (104) towards the condenser unit (106) by a compressor unit (108); expanding cooling fluid when flowing from the condenser unit (106) towards the evaporator unit (104) by an expansion unit (110); and controlling a condenser temperature to control temperature and pressure of the cooling fluid.
20. A method of cooling a cooling room (102) by circulating cooling fluid along a cooling path (126) in an analytical device (10) for analyzing a sample, wherein the method comprises: evaporating cooling fluid by an evaporator unit (104) which is thermally coupled with the cooling room (102); condensing cooling fluid evaporated in the evaporator unit (104) by a condenser unit (106); compressing cooling fluid when flowing from the evaporator unit (104) towards the condenser unit (106) by a compressor unit (108); expanding cooling fluid when flowing from the condenser unit (106) towards the evaporator unit (104) by an expansion unit (110); and regulating a pressure at the evaporator unit (104) by the expansion unit (110).-49 -