EP3171105A1 - Cooling device with several temperature zones - Google Patents

Abstract

In a refrigerator, the work space (1) is divided into two temperature zones (2, 3), wherein in the upper temperature zone (3) a higher temperature is to be maintained than in the lower one. Furthermore, air conveying means (10, 11, 12, 13) are provided for introducing air from a cooling module (8) from below into the work space (1) and removing it from above from the work space (1) and returning it to the cooling module (8). The controller (14) of the apparatus is adapted to maintain a first setpoint temperature in the lower temperature zone and a second setpoint temperature in the upper temperature zone by (a) controlling the flow rate of the air conveying means (10, 11, 12, 13). (b) selects the temperature of the cooling module (8) depending on the desired temperatures in the temperature zones.

Description

Field of the invention

The invention relates to a refrigerator, in particular a refrigerator or a freezer, according to the preamble of claim 1, and a method for operating such a refrigerator.

background

It is known to subdivide the useful space of a cooling device, in particular of a refrigerator, into a plurality of temperature zones, for example into a lower temperature zone and an upper temperature zone. For these temperature zones different setpoint temperatures are specified, e.g. 0-2 ° C for the lower temperature zone and 4-6 ° C for the upper temperature zone. Thus, in the lower temperature zone, articles may be stored which should be kept relatively cool, e.g. Meat while in the upper temperature zone items are stored, which should not be kept as cold as e.g. Cheese.

Furthermore, devices are also known in which cooling air is circulated between a cooling module and work space. If two temperature zones with different temperature are to be realized in such devices, separate air supply into the individual zones or additional, individually controllable coolant are required.

Presentation of the invention

It has as its object to provide a device of the type mentioned, which is simple in terms of apparatus.

• Einen Nutzraum mit mindestens einer unteren und einer oberen Temperaturzone: Der Nutzraum dient der Aufnahme des zu kühlenden Guts.
• Ein Kühlmodul zum Kühlen von Luft: Dabei handelt es sich z.B. um den Verdampfer einer Wärmepumpe oder um die kalte Seite eines Peltier-Elements.
• Luftfördermittel, um die Luft vom Kühlmodul von unten in den Nutzraum einzuleiten und von oben aus dem Nutzraum abzuleiten und zum Kühlmodul zurückzuführen: Diese Luftfördermittel umfassen beispielsweise einen Ventilator und geeignete Luftkanäle.
• Eine Steuerung: Die Steuerung dient zum Steuern der Komponenten des Geräts. Sie ist dazu ausgestaltet, in der unteren Temperaturzone eine erste Solltemperatur und in der oberen Temperaturzone eine zweite Solltemperatur aufrechtzuerhalten, und zwar indem sie die folgenden zwei Grössen abhängig von der (gemessenen oder geschätzten) momentanen Temperatur in der ersten und der zweiten Temperaturzone steuert:
  1. a) die Strömungsgeschwindigkeit der von den Luftfördermitteln geförderten Luft sowie auch
  2. b) die Temperatur des Kühlmoduls.

This object is achieved by the device according to claim 1. Accordingly, the device has the following components:

• A usable space with at least one lower and one upper temperature zone: The usable space serves to accommodate the material to be cooled.
• A cooling module for cooling air: This is, for example, the evaporator of a heat pump or the cold side of a Peltier element.
• Air conveying means to introduce the air from the cooling module from below into the work space and to divert from the top of the work space and due to the cooling module: These air conveying means include, for example, a fan and suitable air ducts.
• A controller: The controller is used to control the components of the device. It is designed to maintain a first setpoint temperature in the lower temperature zone and a second setpoint temperature in the upper temperature zone by controlling the following two quantities depending on the (measured or estimated) instantaneous temperature in the first and second temperature zones:
  1. a) the flow velocity of the air conveyed by the air conveyor and also
  2. b) the temperature of the cooling module.

The invention is based on the finding that the temperatures in the two temperature zones can be set independently of one another within wide ranges by a suitable choice of the two variables mentioned. This will be described in more detail below.

The invention also relates to a method for operating such a cooling device, in which the instantaneous temperatures in the lower and upper temperature zones are measured and, depending on the deviation of the instantaneous temperatures from desired values, the flow velocity as well as the temperature of the cooling module are selected.

Brief description of the drawings

• Fig. 1 einen schematischen Schnitt durch ein Kühlgerät,
• Fig. 2 die Temperatur abhängig von der Position im Nutzraum für verschiedene Strömungsgeschwindigkeiten v und Anfangstemperaturen T0,
• Fig. 3 die Korrektur für eine zu tiefe Temperatur am Ort x1 und
• Fig. 4 die Korrektur für eine zu tiefe Temperatur am Ort x2.

Further embodiments, advantages and applications of the invention will become apparent from the dependent claims and from the following description with reference to FIGS. Showing:

• Fig. 1 a schematic section through a refrigerator,
• Fig. 2 the temperature depends on the position in the working space for different flow velocities v and initial temperatures T0,
• Fig. 3 the correction for too low a temperature at location x1 and
• Fig. 4 the correction for too low a temperature at location x2.

Ways to carry out the invention

The device according to Fig. 1 has a working space 1, which is at least mentally divided into a lower temperature zone 2 and an upper temperature zone 3, wherein the lower temperature zone 2 is arranged lower than the upper temperature zone 3.

To the user side, the utility room 1 is completed by a door 4.

The work space 1 is advantageously air-permeable in the vertical direction, i. that cooling air can rise through the working space 1 from the lower end of the working space to the upper end of the working space.

As shown, the two temperature zones 2 and 3 can be separated from each other by a partition plate 5, which has at least one air passage opening. Such a partition plate 5 reduces the temperature exchange between the two temperature zones due to diffusion and radiation, but still allows the flow of air from the bottom to the top.

The device according to Fig. 1 further comprises a heat pump comprising a compressor 6, a condenser 7, an evaporator 8 and a throttle (not shown) between the condenser 7 and the evaporator 8. In operation of the compressor 6, the evaporator 8 is cooled and the condenser 7 is heated.

In addition, air conveying means are provided, which comprise an air outlet 10 at the upper end of the work space 1, a connecting duct 11, a fan 12 and an air inlet 13 at the lower end of the work space 1.

The air outlet 10 at the upper end of the work space 1 consists in the present embodiment of several openings on the ceiling of the work space, which connect the work space with the connecting channel 11. The air inlet 13 is similarly formed by a plurality of openings at the bottom of the work space. However, the openings of the air outlet 13 and of the air inlet 10 can also be arranged, for example, in the region of the edges of the ceiling or of the floor of the work space 1, possibly behind suitable diaphragms.

The delivery rate of the fan 12, i. the flow velocity of the air in the work space 1, is advantageously dimensioned so that the work space 1 is laminar flows through with air, i. it comes when flowing through the usable space 1 is not a swirling of the air.

With the air conveying means, air can be sucked up from the working space 1, whereupon this air is guided through the connecting channel 11 and fan 12 to the evaporator 8 and cooled there. From the evaporator 8, the air passes through the air inlet 13 back into the usable space. 1

The heat thus generated by the system is dissipated via the condenser 7, which is cooled, for example, with ambient air (not shown).

For controlling the components of the device, a controller 14 is provided. This has the required hardware and software components to control the system in the manner described below.

The controller 14 preferably has a memory in which setpoint temperatures for the upper and lower temperature zones 3 and 2 are stored. These target temperatures are advantageously between 0 and 10 ° C, the target temperature for the lower temperature zone is lower than for the upper temperature zone, in particular by at least 1 ° C.

The controller 14 may further include input means (not shown) that allow the user to specify one or both of these setpoint temperatures, in which case the controller 14 should ensure that the setpoint temperature for the lower temperature zone is lower than for the upper temperature zone , again in particular at least 1 ° C.

Next are in Fig. 1 two temperature sensors 17 and 18 shown. The first temperature sensor is located at a height x1 in the lower temperature zone 2 and the second temperature sensor 18 is located at a height x2 in the upper temperature zone 3.

When the air cooled by the evaporator 8 flows through the utility space 1 from bottom to top in the direction x, it heats up. In the equilibrium state of the device, the heating is due to the fact that the air is heated on the side walls of the work space, since the insulation of the work space is not ideal.

It can be shown that the temperature T (x) as a function of the position x (ie the vertical position in the work space 1) in the equilibrium state of the system, neglecting the heat exchange via diffusion and radiation, and assuming a constant density of the air, can be approximated by the following relationship: $$\mathrm{T}\left(\mathrm{x}\right)=\left(\mathrm{T}\mathrm{0}-\mathrm{U}\right)\cdot \exp \left(-\mathrm{k}\cdot \mathrm{x}/\mathrm{v}\right)+\mathrm{U}$$

T0 denotes the temperature at the lower end of the working space, U the ambient temperature, k a constant proportional to the thermal conductivity of the side walls, and v the flow velocity of the air in the working space 1.

The temperature T0 is referred to below as the initial temperature, and it is equated for the sake of simplicity of the temperature of the evaporator 8 or cooling module.

• Die (mittlere) Flussgeschwindigkeit v kann variiert werden, indem die Drehzahl des Ventilators 8 variiert wird oder indem der Ventilator in kurzen Intervallen mit geeignetem Ein-/Ausschaltverhältnis getaktet betrieben wird.
• Die (mittlere) Anfangstemperatur T0 kann variiert werden, indem die Leistung der Wärmepumpe variiert wird oder indem der Kompressor in kurzen Intervallen mit geeignetem Ein-/Ausschaltverhältnis getaktet betrieben wird.

As can be seen from equation 1, therefore, the temperature of the air in the working space 1 increases from bottom to top. The speed of the increase is essentially given by the flow velocity v of the air, while the initial temperature T0 substantially corresponds to the temperature of the evaporator 8. Both of these parameters can be varied by the controller 14:

• The (average) flow velocity v can be varied by varying the speed of the fan 8 or by cycling the fan at short intervals with a suitable on / off ratio.
• The (middle) initial temperature T0 can be varied by varying the heat pump's power or by cycling the compressor at short intervals with a suitable on / off ratio.

Fig. 2 shows the course of the temperature T in the work space 1 as a function of the height position x. In this case, the curve 20 shows the temperature profile for a given initial temperature T0 and a certain flow velocity v.

If the flow velocity v is increased, but the initial temperature T0 is left constant, the curve is less steep (see curve 21). If, however, the flow velocity V is reduced at a constant initial temperature T0, the curve is steeper (curve 22).

If, however, the flow velocity v is kept constant, but the initial temperature T0 is reduced, generally lower temperatures result in the cooling space (curve 23), while higher initial temperatures T0 result in higher temperatures (curve 24).

Fig. 2 illustrates that by suitably selecting the parameters T0 and v, the temperatures T1 and T2 in the lower temperature zone 2 and the upper temperature zone 3 at the locations x1 and x2 can be selected substantially independently of each other by the initial temperature T0 and the flow velocity v suitable be set. In other words, for given values T1 = T (x1) and T2 = T (x2), Equation 1 can be solved for parameters T0 and, as far as the conditions given to the person skilled in the art from Equation 1 and from the physical laws, such as T1 < T2, T1 <U and T2 <U.

In this way it is possible to achieve the two desired temperatures T1 and T2 in the lower and in the upper temperature zones 2 and 3, respectively, by the power of the fan 12 and thus the flow velocity v and the power of the compressor 6 and thus the temperature of the evaporator 8 are suitably selected by the controller 14.

For example, as in Fig. 3 illustrates, at the current flow rate v 'and initial temperature T0', the temperature T2 in the upper temperature zone 3 is correct, but the temperature T1 'in the lower temperature zone 2 is too low, the controller 14 raises the temperature of the evaporator 8 to a higher value T0> T0 ', and it also increases the flow rate to a somewhat higher value v'> v, causing the temperature profile curve to start at a higher T0 but increase less rapidly.

Is, however, as in Fig. 4 illustrates, at the current flow velocity v 'and initial temperature T0', the temperature T1 in the lower temperature zone 2 is correct, but the temperature T2 'in the upper temperature zone is too low, the controller 14 reduces the flow velocity to a value v <v' ( whereby the curve becomes steeper) and slightly reduces the initial temperature to a value T0 <T0 '.

In this way, rules for changing the values of v and T0 for the various deviation scenarios can be found, and / or Equation 1 allows the direct approximate calculation of the appropriate values of flow velocity v and initial temperature T0 for given values of temperatures T1 and T2.

Equation 1 represents a very simple model which the controller 14 can use for the calculation of the temperature profile in the work space 1 as a function of the flow velocity v and the initial temperature T0. In this case, the thermal conductivity k in Equation 1 can be e.g. be fixed at the manufacturer, while the second parameter, the ambient temperature U, either directly measured with a suitable temperature sensor or can be estimated based on the current temperatures T1 and T2 at a known flow rate v and initial temperature T0.

The controller 14 may also use a more complex thermal model of the workspace, taking into account, for example, in addition the thermal masses and instantaneous temperatures of the product to be stored in the lower and upper temperature zones as model parameters, and / or also the temperature-varying density of the Air. In particular, the thermal masses and instantaneous temperatures enter the model as a priori unknown parameters. However, they can be measured by measuring the temperatures at locations x1 and x2 as a function of time, the flow velocity v and the initial temperature T0 from the controller 14 in operation is estimated by means of compensation calculation (ie "curve fitting") and then used for an improved control of the device.

In other words, the controller 14 may thus be configured to use a mathematical model of the thermal properties of the work space 1 described by parameters for selecting the flow velocity v and the initial temperature T0. The parameters of the model may be e.g. to be the above-mentioned values of k and / or U and / or the thermal mass and / or instantaneous temperature of the loads and / or the air in the temperature zones. Further, the controller 14 is configured to measure at least one, preferably a plurality of temperatures as a function of time, the flow velocity v and the initial temperature T0 in the working space, thereby determining the parameters of the model.

In this way, the controller can estimate the effect of changes in the flow velocity v and the initial temperature T on the temperature distribution in the work space 1, which allows it to more precisely control the temperatures in the two temperature zones.

While preferred embodiments of the invention are described in the present application, it should be clearly understood that the invention is not limited to these and may be practiced otherwise within the scope of the following claims.

Claims (9)

Refrigerator, in particular refrigerator or freezer, with
a work space (1) having at least one lower and one upper temperature zone (2, 3),
a cooling module (8) for cooling air, air conveying means (10, 11, 12, 13) to introduce the air from the cooling module (8) from below into the work space (1) and from the top of the work space (1) and derive Attributed cooling module (8) and
a controller (14),
characterized in that the controller (14) is adapted to maintain a first setpoint temperature in the lower temperature zone (2) and a second setpoint temperature in the upper temperature zone (3) by controlling a flow velocity (v) of the air conveying means (10, 10). 11, 12, 13) and a temperature (T0) of the cooling module (8) depending on a current temperature in the lower and upper temperature zone (2, 3) controls. Cooling device according to claim 1, wherein in the lower temperature zone (2) a first temperature sensor (17) is arranged and the controller (14) is adapted to the temperature at the first temperature sensor (17) by controlling the flow velocity (v) and the temperature ( T0) of the cooling module (8). Refrigerator according to one of the preceding claims, wherein in the upper temperature zone (3) a second temperature sensor (18) is arranged and the controller (14) is adapted to the temperature at the second temperature sensor (18) by controlling the flow velocity (v) and the Temperature (TO) of the cooling module (8) to regulate. Refrigerator according to one of the preceding claims, wherein the air conveying means (10, 11, 12, 13) an air inlet (13) at a lower end of the working space (1) and an air outlet (10) at an upper end of the work space (1). Refrigerator according to claim 4, wherein the conveying means for laminar flow through the work space (1) are designed with air. Refrigerator according to one of the preceding claims, wherein the temperature zones (2, 3) by a partition plate (5) are separated from each other, wherein the partition plate (5) has at least one air passage opening. Refrigerator according to one of the preceding claims, characterized in that the controller (14) is adapted to use a mathematical, described by parameters model of thermal properties of the usable space (1) for selecting flow velocity (v) and the initial temperature (TO), and wherein the controller (14) is further configured to measure in the working space (1) at least one, preferably a plurality of temperatures as a function of time, the flow velocity (v) and the initial temperature (T0) and thereby to determine the parameters of the model. Cooling device according to one of the preceding claims, wherein the first setpoint temperature is lower than the second setpoint temperature, and in particular wherein the first setpoint temperature is at least 1 ° C lower than the second setpoint temperature. Method for operating the refrigerating appliance according to one of the preceding claims, characterized in that the instantaneous temperatures in the lower and the upper temperature zone are measured, and depending on a deviation of the instantaneous temperatures from nominal values, the flow velocity (v) as well as the temperature (TO) of Cooling module (8) can be selected.

Images