DE102004005802A1 - A refrigeration system has an expansion valve by which the refrigerant flow rate is controlled according to the temperature difference between the inlet and outlet of the evaporator - Google Patents

Abstract

The system is used for a cooling bath and the evaporator inlet temperature (to1) is monitored by a sensor and compared to the outlet temperture (to2) to control the electronically controlled expansion valve.A reference temperature (SOLto1) is determined to which the inlet temperature is targeted.

Description

The The invention relates to a method for controlling a refrigerating machine according to the evaporator principle according to the preamble of claim 1.

One Another aspect of the invention relates to an exercise for the Method suitable arrangement according to the preamble of the claim 14th

To the State of the art belongs already a method according to the preamble of claim 1 or an arrangement according to the preamble of claim 14 with an electronic Injection system consisting of regulator, electronic expansion valve and two transducers or sensors with which a refrigerant flow control dependent from a temperature difference of the refrigerant between an evaporator inlet and leakage (Dubbel, Paperback for Mechanical Engineering, 18th edition, page M 65.) With this electronic injection system should a steady, cool load-adapted course the evaporation pressure can be achieved, with a higher evaporation pressure due to less overheating should enter. As further advantages are higher performance figures for the refrigeration, lower compressor run times and greater control accuracy, too with load changes called.

Around a high efficiency or higher Performance figures for refrigeration machines With an evaporator to achieve, one is generally anxious, the Temperature difference between evaporator outlet and evaporator inlet, also overheating called, if possible to keep low. But are the control parameters too small overheating set, the control becomes unstable. That's why in practice the evaporator with at least as much overheating as the smallest stable overheating MSS (minimum stable signal) operated.

Of the The present invention is based on the object, a method for controlling a chiller according to the evaporator principle of the type mentioned or a to create appropriate device with the efficiency the chiller is further increased with stable performance.

These The object is achieved by the method with the specified in claim 1 Characteristics solved.

With the solution according to the invention is achieved that the wet vapor in the evaporator only briefly up to the evaporator outlet and about that is extended, so an overheating area in which expanded, gaseous refrigerant just overheated is largely avoided. Nevertheless, the regulation is the Refrigerant supply stable in the evaporator.

To becomes dependent from a temperature difference of the refrigerant on an evaporator side of the Evaporator output on the one hand and at the evaporator inlet on the other - and optionally other sizes, in particular the temperature of a bath liquid, see claim 3 - in the controller according to a special characteristic, which is defined below, a setpoint the temperature at the evaporator inlet or a desired temperature formed and a regulator subordinate to the controller, which controls this Target temperature with an actual value of this temperature or actual temperature at the evaporator entrance, which depends on the comparison result the refrigerant over the controllable expansion element, an injection valve, into the evaporator is fed. The above temperature difference as a criterion the setpoint formation of the temperature at the evaporator inlet is preferably, as explained below not from the temperature of the refrigerant directly at the evaporator outlet, So the conventional defined overheating, out.

According to the inventive method, the first controller evaluates the temperature difference of the refrigerant on the evaporator side of the evaporator outlet on the one hand and the evaporator inlet on the other hand according to the criterion of whether it is in a range above a first predetermined value, a tolerance value of, for example, 3 K or in a lower range , Only in the former case, the target value of the temperature at the evaporator inlet is increased time-dependent continuously, which is the refrigerant injection is amplified in the evaporator via the lower controller and controlled by him expansion, but otherwise kept constant in the lower region of said temperature difference regardless of this and optionally at transition to an even deeper area below a second predetermined Value of the said temperature difference, which is at most as high as the first predetermined value and is preferably up to about 2 Kelvin lower than this, is reduced in a defined manner, as will be explained below.

at Start of evaporation and start of a first control cycle is on the lower controller the target temperature of the refrigerant at the evaporator input preset to a low value, which results has that little refrigerant is injected into the evaporator, by its Überhit tion in the area of the evaporator outlet a large temperature difference of refrigerant on the evaporator side of the evaporator outlet on the one hand and the On the other hand the first predetermined value arises. Therefore, at the subordinate Controller the DESIRED temperature of the refrigerant at the evaporator inlet increases continuously, creating more refrigerant flows into the evaporator, until the temperature of the refrigerant on the evaporator side of the evaporator outlet substantially the temperature at the evaporator inlet drops, causing the overflow the evaporator with not complete vaporized refrigerant indicating a rapid drop in temperature is characteristic. - If there the first preset value of said temperature difference reached and fallen below, there is no further increase in SET temperature of the refrigerant at the evaporator input more, but because of this temperature difference first one Constant attitude and optionally below the second predetermined Value of said temperature difference even a defined reduction. The thus kept constant or even reduced coolant supply has delayed again a no longer completely filling the evaporator wet steam area result. - A new time-dependent controlled control cycle begins in which said temperature difference of the refrigerant rises and the target temperature of the refrigerant at the evaporator inlet or injection again automatically continuously elevated becomes.

This The process is repeated depending on the event, namely on the said temperature difference dependent in control cycles continuously.

The mentioned above Lowering the target temperature of the refrigerant at the evaporator inlet takes place first at every transition said temperature difference of the refrigerant among the second predetermined value with a single temperature jump (Δ SOLL_to 1- offset) given size, the in particular according to claim 2 in a range of values of the temperature of the bath liquid each one temperature of the bath is permanently assigned. The temperature jump is dependent of several parameters typically at -1 K for a temperature of 0 ° C of the bath liquid and falls with decreasing temperatures of the bath liquid from. Instead of the temperature of the bath liquid can be used for the design the temperature jump also from the target temperature of the refrigerant be assumed at the evaporator inlet. In addition, but in practice Not always necessary, the target temperature according to claim 5 time-dependent be lowered relative to the time at which the said Temperature difference (to 2 - to 1) of the refrigerant the second predetermined value for a predetermined time of e.g. 40 seconds below. This reduction can according to claim 6 first as another jump and after another predetermined Time of e.g. 40 sec continuously, in particular fall off linearly.

The Lowering the target temperature is in any case terminated when the said Temperature difference the second predetermined value of said temperature difference again, or respectively at the end of a control cycle.

• – großen Kältemitteldurchsatz,
• – hohen Verdampfungsdruck Po 1 (z.B. Kältemittel R404A: 5.0 bar),
• – hohe Einspritztemperatur to 1 (z.B. -6°C; aus Kältemitteltabelle),
• – hohe Kühlleistung (z.B. 1700W);

Einspritzventil nur wenig geöffnet hat zur Folge:

• – geringen Kältemitteldurchsatz,
• – kleinen Verdampfungsdruck Po 1 (z.B. Kältemittel R404A; 0.85 bar),
• – tiefe Einspritztemperatur to 1(z.B. -50°C; aus Kältemitteltabelle),
• – geringe Kühlleistung (z.B. 150 W).

The regulation is based on the following relationship with the refrigerant used (eg R404A):
Injector valve wide open results in:

• - large refrigerant flow rate,
• - high evaporation pressure Po 1 (eg refrigerant R404A: 5.0 bar),
• - high injection temperature to 1 (eg -6 ° C, from refrigerant table),
• - high cooling capacity (eg 1700W);

Injector only slightly open results in:

• Low refrigerant flow rate,
• - small evaporation pressure Po 1 (eg refrigerant R404A, 0.85 bar),
• - low injection temperature to 1 (eg -50 ° C, from refrigerant table),
• - low cooling capacity (eg 150 W).

The pre-set SOLL temperature at the evaporator inlet before starting the evaporator is lower than the desired temperature tb of a bath of a tempering medium cooled with the refrigerated circulator set to, so that the temperature of the bath liquid or bath temperature tb is safely reached, for example, for tb = - 40 ° C to - 50 ° C.

More Specifically, at the beginning of evaporation, the target temperature at the evaporator inlet starting from the low preset value dependent from a series of parameters, continuous or quasi-continuous elevated. If the detected Temperature difference of the refrigerant on both sides of the evaporator falls below the second predetermined value, the controller lowers the setpoint temperature at the subordinate controller at the evaporator entrance slightly, i.e. in turn dependent of several parameters, from, for example, less than 1 K, as you can read above.

Of the Regulators, i. Main controller, in the course of cyclic control at the subordinate controller the target temperature of the refrigerant forms at the evaporator inlet in the manner described, thus regulating the level the evaporator with not complete vaporized refrigerant up to its output and briefly beyond that in the manner of a Two-point or three-step control quickly and accurately. The extent of the Naßdampfbereichs in the evaporator takes place deliberately temporarily until its expansion to the evaporator outlet and above but not completely vaporized refrigerant from the evaporator can escape only briefly, because in this Situation the filling the evaporator with not complete vaporized refrigerant automatic is moved back to the evaporator outlet before running. After that rises the filling with not complete vaporized refrigerant again until reaching the evaporator outlet continuously at. Thus, the filling varies of the evaporator with the refrigerant by regulation in control cycles constantly by a value close to a complete filling lies. The efficiency of the chiller is optimized.

The Injection temperature to 1 or actual temperature at the evaporator inlet is the temperature of the temperature control, in particular a Temperierflüssigkeit a bath of a liquid thermostat tracked where the DESIRED temperature of the refrigerant at the evaporator input is affected accordingly.

To the above-described initial mode of regulation, in which maximum Cooling capacity the scheme can go to another mode, in which the temperature of the bath liquid or the bath temperature is kept substantially constant at a set value.

The dynamic behavior of this tracking in the initial mode is improved by the measure specified in claim 3, after which the Temperature of the bath liquid detected and differentiated in time to the nominal temperature at the evaporator inlet is added additive.

The above defined formation of the target temperature of the refrigerant at the evaporator entrance, i. the setpoint takes place in the parent Regulator not necessarily completely continuous in time Type of analog control, but expedient with digital means in successive fixed timed regulator passes, the each briefly opposite a typical control cycle.

To has for typical chillers a clock of controller passes proved to be appropriate by 1 Hz. With each controller cycle a new setpoint SOLL_to 1 of the refrigerant at the evaporator inlet according to the in Claim 9 specified control algorithm formed.

to simplified precise Evaluation of a temperature lift, located on the evaporator side dependent on the evaporator output of its filling is particularly useful the measure specified according to claim 10, whereby the resulting temperature easy to evaluate 4 - 10 K can be. This big one Temperaturhub is based on that in the operating case, in which no liquid Refrigerant off the evaporator outlet exits, the temperature at the measuring point as a result of the addition supplied heat flow relatively strong elevated, because by the exiting from the evaporator gaseous refrigerant little heat is derived, but in the operating case, in the not fully evaporated liquid refrigerant exits the evaporator outlet, a larger part of the measuring point additionally supplied heat flow is derived, causing the temperature of the measuring point significantly less is high.

The dependent on the state of the refrigerant from the evaporator output increase the temperature at the measuring point can be achieved by heat conduction to the measuring point of a separate heater and particularly advantageous according to claim 12 by heat conduction from an inner heat exchanger to the measuring point. - The process performed with the inner heat exchanger according to claim 11 has the main purpose that in the inner heat exchanger from the evaporator outlet temporarily leaking liquid refrigerant components are re-evaporated, so that the compressor is always fed only with gaseous refrigerant and liquid hammering in the compressor can be avoided, which can otherwise destroy it permanently.

claim 13 includes a known convenient method of temperature detection - actual value - at the Evaporator inlet.

The Features of an exercise arrangement of the control method according to the invention are specified in claim 14. Thereafter, the arrangement comprises two controllers. In a first controller, which also acts as an external controller or main controller can be designated, from the actual temperature difference of the refrigerant respectively on the evaporator side of an evaporator outlet on the one hand and on the other hand, at a vaporizer input, a set value of the injection temperature or a nominal temperature of the refrigerant at the evaporator input calculated or formed, in a the main controller subordinate regulator or auxiliary regulator is fed to it with the actual temperature of the refrigerant to be compared at the evaporator entrance. To the output of the subordinate Reglers is connected to the controllable expansion organ that works with the Input of the evaporator is in communication.

Of the subordinate controller is thus in a the main controller, the Nominal value forms, subordinate or inner control loop arranged, whose controlled system is the evaporator inlet; he regulates the temperature of the refrigerant at the evaporator entrance, i. the injection temperature, on the Setpoint of this temperature. As above for the process in detail specified determines the temperature at the evaporator inlet or the Injection temperature the rate of expanded refrigerant entering the evaporator passes and flows through it, and that gives for a typical refrigerant a small, i. low temperature at the evaporator inlet a low Refrigerant flow rate through the evaporator and a large, i. relatively high temperature at Evaporator input a high refrigerant flow rate.

Of the subordinate or inner loop is part of an outer loop, which can also be referred to as the main control loop, and the Main regulator, the subordinate regulator, the expansion organ and the evaporator with Temperaturmeßstelle on the evaporator side includes the evaporator outlet.

The exercised with this arrangement Regulatory procedure on which the particularities of the order are based, is described above in connection with claim 1.

In summary shows the controller arrangement thereby approximately two-point behavior for the control of Naßdampfbereichs in the evaporator. Two-point behavior is especially present when with the controller only by the first predetermined value and not by the second predetermined value of the temperature difference of the refrigerant on the evaporator side of the evaporator outlet on the one hand and the On the other hand, evaporator input is regulated. The regulator is then only for set forth in claim 14 areas (A) and (B) set. - So far except the first predetermined value and the second predetermined value of the said temperature difference determines the scheme is the parent Regulator for designed a three-step control, at which the target temperature on the input of the slave controller is not changed, if the determined temperature difference of the refrigerant on the evaporator side the evaporator outlet and at the evaporator inlet between the first and second predetermined values, but defined is lowered when the second predetermined value falls short is, in this case, too, the target temperature of the refrigerant at the evaporator inlet and thus the refrigerant flow rate to change so that the wet steam fluctuates only slightly over a maximum value at the evaporator outlet.

By the controller arrangement, the evaporator as much as possible over time with wet steam filled, what the efficiency of the chiller is optimized. Nevertheless, the regulation is not unstable.

Further advantageous features of the arrangement are specified in claims 15 - 24.

As mentioned above, it comes on the basis of the present control concept regularly to a short-term leakage not completely evaporated refrigerant from the evaporator, whereby a directly downstream of the evaporator compressor would be disturbed, in which liquid shocks can occur. In order to avoid this, an internal heat exchanger is arranged between the outlet of the evaporator and the compressor according to claim 18, which vaporizes the refrigerant completely gaseous before its entry into the compressor and for this purpose by the compressed and liquefied refrigerant, which is supplied to the controllable expansion element, is heated. - In addition, the heat exchanger can be used in a particularly advantageous manner to increase detectable with the temperature sensor at the evaporator output temperature elevation by a few Kelvin by the heat exchanger with the temperature measuring in a thermally conductive line section between the heat exchanger and the evaporator outlet is in communication. The heat exchanger can thus perform various functions in the control system and the refrigeration machine controlled thereby.

Around disturbing Fluctuations in the temperature of the tempering medium, i. the bath temperature in the case of a bath thermostat quickly regulate, the temperature tb of the bath liquid or the bath temperature detected directly and in time in the main controller differentiated to the value formed in the main controller of the target temperature added to the evaporator input, with which the setpoint input of the subordinate regulator is applied. This will change the injection temperature or the temperature at the evaporator inlet of the temperature of the bath liquid quickly tracked.

SOLL_to 1_alt

der Wert der SOLL-Temperatur am Ende eines vorangegangenen Reglerdurchlaufs,

Δ SOLL_to 1

der bis zum Ende des aktuellen Regelzyklus Reglerdurchlaufs nach Maßgabe der besagten Temperaturdifferenz gebildete Differenzwert der SOLL-Temperatur,

Gradienttb

der Gradient bzw. das zeitliche Differential der Badtemperatur tb.

The dynamically stable and uncomplicated controller or main controller is time-controlled with fixed clock, the controller is suitable to complete a controller cycle after each timer-controlled controller call and at each controller pass the setpoint temperature (SOLL to 1) of the refrigerant at the evaporator input according to the following control algorithm including Generating the temperature jumps of the target temperature to form: SOLL_to 1 = SOLL_to 1 old + Δ SOLL_to 1 + gradient tb, where is:

SOLL_to 1 _old

the value of the DESIRED temperature at the end of a previous controller cycle,

Δ SOLL_to 1

the differential value of the DESIRED temperature formed up to the end of the current control cycle controller cycle in accordance with the said temperature difference,

Gradienttb

the gradient or the time differential of the bath temperature tb.

The The invention will be described below by way of example with reference to a drawing described with seven figures. Show it:

1 a schematic representation of the refrigerator,

2 the control circuits implemented herein having an outer main regulator and an inner auxiliary regulator,

3 a characteristic of the main regulator, namely a dependence of a setpoint change of the target temperature of the refrigerant at the evaporator inlet Δ SOLL to 1 from the temperature difference (to 2 - to 1) of the refrigerant at an evaporator side of the evaporator outlet on the one hand and the evaporator inlet on the other hand,

4 in addition to 3 the time change of the setpoint change SOLL_to 1 in state C of 3 .

5 in addition to 4 the time change of the setpoint change Δ SOLL_to 1 in state A of 3 .

6 in addition to 3 a characteristic curve of the dependency of predefinable value values of a desired value jump (Δ SOLL_to 1 offset) on the temperature tb of the temperature control liquid which is generated at each transition from the region B into the region A of said temperature difference (to 2 - to 1), and

7 a typical time profile of the setpoint temperature SOLL_to 1 and further control parameters after the start time of the control.

In 1 is designated by 1 an evaporator, which is part of a bath thermostat with a bath 2 a tempering medium is. The temperature of the tempering medium or of the temperature control is with a temperature sensor 3 detected.

Upstream of an evaporator inlet 4 is a controllable organ of expansion 5 arranged a liquid refrigerant which evaporates by expansion behind the expansion element while heat from the environment, in particular the tempering medium in the bath 2 receives. The controllable organ of expansion 5 is realized in the embodiment by an expansion valve, which is adjustable by means of a stepping motor and a spindle.

Between the expansion organ 5 and the evaporator inlet are a temperature sensor 6 and a pressure sensor 7 arranged with which the temperature or the pressure at the evaporator inlet 4 is detected. All it takes is one of these two sensors 6 . 7 , The temperature sensor 6 is less complicated to implement. The temperature at the evaporator inlet can also be used with the pressure sensor 7 be determined by refrigerant-dependent conversion.

Another temperature sensor 8th is located at a temperature measuring point on an evaporator side of an evaporator outlet 9 of which a conduit to an internal heat exchanger 10 leads. A line section 11 between the evaporator outlet 9 and the inner heat exchanger 10 in which the temperature sensor 8th is preferably arranged approximately centrally, consists of good heat conducting material, in particular copper.

In the further cycle of the refrigerant follow the heat exchanger 10 a compressor 12 , an air-cooled condenser 13 and a refrigerant collector 14 , the output side via a dryer 15 with the heat exchanger 10 connected is. The expansion organ 5 gets out of the inner heat exchanger 10 , in which the refrigerant heat is removed, fed.

For controlling the refrigerant feed rate, via the expansion device 5 in the evaporator 1 is fed, serve a first controller 16 , which is also referred to as the main controller or external controller, as well as a downstream subordinate regulator 17 ,

In an outer loop, the main controller 16 at his entrance 18 with signals from the temperature sensors 6 and 8th fed, such that in it the temperature difference can be evaluated to 2 - to 1 of the refrigerant on the evaporator side of the evaporator outlet on the one hand and the evaporator inlet walls on the other hand. Another entrance 19 comes with a signal from the temperature sensor 3 fed according to the bath temperature tb.

In the timed with fixed clock of 1 Hz controller 16 From the above temperature difference to 2 - to 1 of the refrigerant at each controller pass after a controller call a setpoint SOLL_to 1 the temperature at the evaporator inlet 4 formed from the value of the target temperature of a previous controller run, from a differential value of the set temperature formed for the current controller cycle and the gradient of the bath temperature according to the control algorithm specified above. On a time dependence of the setpoint the formation of setpoint jumps will be discussed below.

The resulting setpoint of the temperature to 1 at the evaporator inlet 4 is in an input of the subordinate regulator 17 fed. In this he is using the actual value of the temperature at the evaporator inlet 4 compared. Depending on the resulting deviation of the temperature at the evaporator inlet is the expansion organ 5 from the output of the slave controller 17 adjusted.

In the characteristic according to 3 shows an example in which value ranges of the temperature difference to 2 - to 1 of the refrigerant, with the temperature sensor 8th and the temperature sensor 6 through the regulator 16 can be detected, the target temperature (SOLL_to 1) is changed differently. Shown are three areas A, B, C for the formation of the setpoint difference Δ SOLL_to 1 in a current controller cycle compared to a previous controller cycle SOLL_to 1 _old , which enters into the above-mentioned formula: SOLL_to 1 = SOLL_to 1 old + Δ SOLL_to 1 + gradient tb.

• C. für to 2 – to 1 größer als 3K,
• B. für to 2 – to 1 zwischen 3K und 1,5 K und
• A. für to 2 – to 1 kleiner als 1, 5.

According to 3 the three ranges are defined by the temperature difference to 2 - to 1, viz

• C. for to 2 - to 1 greater than 3K,
• For example, for to 2 - to 1 between 3K and 1.5K and
• A. for to 2 - to 1 less than 1, 5.

there the above first predetermined value is 3 K and the above said second predetermined value 1.5 K.

In the upper area C, the controller increases 16 the setpoint SOLL_to 1 according to time 4 , In the case of a transition from the middle region B, in which no setpoint change occurs, to the lower region A, a one-time setpoint jump (Δ SOLL_to 1-offset) in the controller is initially performed 16 generated, which reduces the setpoint to 1. The predetermined dependence of the desired value jump on the temperature of the temperature control fluid tb or the bath temperature associated with the temperature sensor 3 is detected shows 6 , From this, the decreasing bath temperature linearly falling course of the setpoint jump can be seen. Finally, the controller 16 in the area A, the setpoint SOLL_to 1 continues according to 5 decrease if said temperature difference to 2 - to 1 longer, in 5 at least 40 sec, in the area A stops, so the evaporator output is "wet".

On the regulator 16 the setpoint SOLL_to 1 is preset low, eg to -26 ° C according to 7 in such a way that at the start time of the chiller, a wet steam area in only over a small part of the evaporator 1 extending from the evaporator inlet, while in the remaining evaporator 1 the gaseous refrigerant is overheated to a value above the bath temperature.

Starting from this start state of the chiller, which is also the beginning of a first control cycle, is at the minor controller 17 the DESIRED temperature of the refrigerant at the evaporator inlet SOLL_to 1 according to 4 increased in controller runs virtually continuously. By correspondingly increased coolant supply, the wet steam region expands in the evaporator 1 continue until it reaches the evaporator outlet and not yet fully evaporated refrigerant from the evaporator 1 exit. When the latter occurs, it coincides with the temperature sensor 8th detected temperature to 2 very quickly from about the height of the temperature to 1, which is detected at the entrance of the evaporator, see 7 , where first in the area B of the characteristic 3 a further setpoint increase does not occur and, as soon as the temperature difference to 2 - to 1 passes into the area A, a desired value step Δ SOLL_to 1 - offset of a height according to FIG 6 is produced. Thereafter, the setpoint SOLL_to 1 can be controlled by the main controller 16 on the subordinate controller 17 after a dead time of 40 sec in 5 abruptly further reduced somewhat and after an additional dead time of 40 sec continuously further reduced. Thus, a longer overflow of refrigerant in the wet steam region is avoided, if not already done before the end of the first dead time easily, and the temperature rises to 2 at the outlet of the evaporator 9 certainly back on. The beginning of this increase marks the beginning of the next control cycle. - These control cycles are repeated continuously, with the filling of the evaporator 1 with wet steam of the refrigerant to a maximum at the evaporator outlet 9 constantly fluctuates somewhat. The evaporator 1 is largely filled on average over time with not completely vaporized refrigerant, whereby the efficiency of the refrigerator is optimized. This also applies to a change in the bath temperature tb, since their tendency to change is immediately added to the desired value SOLL - to 1, whereby the temperature to 1 at the inlet of the evaporator, ie the injection temperature, the bath temperature is tracked.

The periodically exiting at the outlet of the evaporator, not yet completely evaporated refrigerant is in the inner heat exchanger 10 after-evaporated, so that only gaseous refrigerant the compressor 12 achieved, which is thus operated gently.

In another example of the control, the following typical operating states result in the steady state:
Evaporator partially filled with fully vaporized refrigerant:

Evaporator to the evaporator outlet completely filled with wet steam refrigerant:

The temperature sensor 8th , with which above values were measured to 2, is in a line section 11 between the evaporator outlet 9 and the inner heat exchanger 10 arranged approximately in the middle. Due to heat conduction processes from the inner heat exchanger to the temperature sensor and from there to the evaporator outlet, the temperature difference to 2 of 6.5 ° C at the two above filling states of the evaporator is substantially greater than in the case where the values to 2 are directly at the evaporator outlet would be detected.

It it turned out that with the control method described above, the level control for the Evaporator with wet steam refrigerant conceived can be compared to previous overheating regulations the efficiency the evaporator and thus the chiller clearly increased becomes. This is an increase the cooling capacity the chiller associated. In bath thermostats, a significantly lower final temperature of the tempering achieved. - The Regulatory procedure can be but also for other cooling systems Use as a bath thermostat advantageous.

1

Evaporator

2

bath

3

temperature sensor

4

evaporator inlet

5

expansion element

6

temperature sensor

7

pressure sensor

8th

temperature sensor

9

evaporator outlet

10

internal heat exchangers (Intermediate heat exchanger)

11

line section

12

compressor

13

condenser

14

Refrigerant collector

15

dryer

16

regulator (Main controller)

17

minor regulator

18

entrance

19

Another entrance

20

pressure line

Claims (24)

Method for controlling a refrigerating machine according to the evaporator, principle, in which a refrigerant via a controllable expansion element ( 5 ) an evaporator ( 1 ), which is in thermally conductive connection with a temperature control medium, wherein the refrigerant supply rate at least depends on a temperature difference (to 2 - to 1) of the refrigerant on an evaporator side of an evaporator outlet ( 9 ) on the one hand and at an evaporator inlet ( 4 ) on the other hand with a controller ( 16 ), characterized in that with a regulator ( 16 ) subordinate controller ( 17 ) the actual temperature (to 1) at the evaporator inlet ( 4 ) via the controllable expansion organ ( 5 ), that with the regulator ( 16 ) a nominal temperature (SOLL to 1) at the evaporator inlet ( 4 ) is formed automatically from said temperature difference (to 2 - to 1) of the refrigerant and to the subordinate controller ( 17 ) is discharged, such that at start of the evaporation of the refrigerant in the evaporator ( 1 ) low preset target temperature (SOLL to 1) at the evaporator inlet ( 4 ) in the course of evaporation by the regulator ( 16 ) is continuously increased automatically until said temperature difference (to 2 - to 1) of the refrigerant, which thereby decreases, reaches a first predetermined value, and by the regulator ( 16 ) with a further decrease in the said temperature difference (to 2 to 1) below a second predetermined value which is at most as high as the first predetermined value, a temperature jump which decreases the set temperature (SOLL_to 1) at the evaporator inlet (Δ SOLL_to 1 -Offset ) is generated, after which a new control cycle can begin, in which said temperature difference (to 2 - to 1) above the first predetermined value increases and the set temperature (SOLL_to 1) at the evaporator inlet by the controller ( 16 ) is again continuously increased independently. Method according to Claim 1, characterized in that the magnitude of the temperature jump (Δ SOLL_to 1 offset) which reduces the setpoint temperature (SOLL_to 1) at the evaporator inlet is predetermined as a function of a temperature (tb) of a thermostating liquid which is mixed with the evaporator ( 1 ) is cooled. Method according to at least one of claims 1 and 2, characterized in that the temperature (tb) of the heat transfer liquid in the regulator ( 16 ) time-differentiated to the value of the nominal temperature (SOLL_to 1) of the refrigerant at the evaporator inlet formed in accordance with said temperature difference (to 2 to 1) of the refrigerant ( 4 ) is added additive. Process according to claim 1 and at least one of claims 2 and 3, characterized in that the temperature (tb) of the bath liquid in a bath ( 2 ) of a bath thermostat is detected. A method according to claim 1 and optionally one of claims 2 to 4, characterized in that, after said temperature difference (to 2 - to 1) of the refrigerant, which decreases after the start of the evaporation, falls below the second predetermined value for a predetermined time has, with the regulator ( 16 ) on the subordinate controller ( 17 ) the nominal temperature (SOLL_to 1) at the evaporator inlet ( 4 ) is automatically lowered further before the new control cycle begins. Process according to claims 1 and 5 and optionally at least one of the claims 2 to 4, characterized in that the further lowering of the Target temperature (SOLL_to 1) at the evaporator inlet after the specified Time from reaching the second predetermined value takes place as a jump and after a further predetermined time additionally continuous (integral) runs. Method according to claim 1 and optionally at least one of claims 2 to 6, characterized in that the formation of the target temperature (SOLL-to 1) by time control of the controller ( 16 ) takes place cyclically in controller runs. Method according to claim 7, characterized in that that the Controller runs timed with about 1 Hz. Process according to claims 1 and 7 and optionally at least one of claims 2 to 6 and 8, characterized in that the nominal temperature (SOLL_to 1) of the refrigerant at the evaporator inlet in the controller passes is formed in each case according to the following control algorithm: SOLL_to 1 = SOLL_to 1 old + Δ SOLL_to 1 + gradient tb , where: SOLL_to 1 _{old is} the value of the DESIRED temperature at the end of a preceding controller run, Δ SOLL_to 1 is the difference value of the DESIRED temperature formed for the current controller cycle compared to the preceding controller cycle in accordance with said temperature difference (to 2 to 2), Gradient tb the gradient or the time differential of the bath temperature tb. Method according to at least one of claims 1 to 9, characterized in that a temperature measuring point on the evaporator side of the evaporator outlet ( 9 ), at which the temperature (to 2) of the evaporator ( 1 ) flowing refrigerant is detected, an additional, approximately constant heat flow is supplied. Process according to at least one of Claims 1 to 10, characterized in that the product from the evaporator outlet ( 9 ) vaporized refrigerant via an internal heat exchanger ( 10 ) a compressor ( 12 ), in which it is compressed, then liquefied during cooling and then via the inner heat exchanger ( 10 ) and through the subordinate controller ( 17 ) controlled expansion organ ( 5 ) the entrance of the evaporator ( 1 ) is redirected. Process according to claims 1, 10, 11 and optionally at least one of claims 2 to 9, characterized in that the additional, approximately constant heat flow of the temperature measuring point ( 8th ) on the evaporator side of the evaporator outlet ( 9 ) by heat conduction from the inner heat exchanger ( 10 ) is supplied. Method according to at least one of the preceding claims, characterized in that the Temperature (to 1) of the refrigerant at the evaporator inlet ( 4 ) is detected by pressure measurement at the evaporator inlet and refrigerant-dependent conversion. Arrangement for controlling a refrigeration machine according to the evaporator principle, in which a refrigerant via a controllable expansion element ( 5 ) an evaporator ( 1 ) is supplied with at least one controller ( 16 ), in which at least one temperature difference (to 2 to 1) of the refrigerant in each case on an evaporator side of an evaporator outlet ( 9 ) on the one hand and at an evaporator inlet ( 4 ) on the other hand, an expansion organ ( 5 ) controlling output, characterized in that the controller ( 16 ) a subordinate controller ( 17 ) whose output is connected to the controllable expansion element ( 5 ) and the at least one input of an actual temperature value (to 1) at the evaporator input ( 4 ) and one in the controller ( 16 ) depending on said temperature difference (to 2 - to 1) of the refrigerant formed SOLL temperature (SOLL_to 1) of the refrigerant at the evaporator inlet, that the subordinate controller ( 17 ) to a low DESIRED temperature value (SOLL_to 1) at the evaporator inlet ( 4 ) is preset and that the controller ( 16 ) is suitable, in a region (C) above a first predetermined value of said temperature difference (to 2 to1) of the refrigerant increasing SOLL temperature values (SOLL_to 1) of the refrigerant at the evaporator inlet ( 4 ), in a range (B) below the first predetermined value up to a second predetermined value of said temperature difference (to 2 - to 1) of the refrigerant which is at most equal to the first predetermined value, the target temperature value ( SOLL_to 1) of the refrigerant at the evaporator inlet ( 4 ) to keep constant independently of said temperature difference (to 2 - to 1) and on transition from the range (B) which is below the first predetermined value to the second predetermined value of said temperature difference (to 2 to 2) of the Refrigerant extends, in a region (A), which is below the second predetermined value of the said temperature difference (to 2 - to 1), one of the target temperature (SOLL_to 1) at the evaporator inlet ( 4 ) to generate a decreasing temperature jump (Δ SOLL_to 1 - offset) of predetermined size. Arrangement according to claim 14, characterized in that the regulator ( 16 ) Comprises means which are suitable for generating the magnitude of the temperature jump (Δ SOLL_to 1 - offset) as a function of a detected temperature (tb) of a temperature control liquid according to a predetermined, preferably linear relationship. Arrangement according to claim 14 and optionally claim 15, characterized in that the controller ( 16 ) is adapted to form in the region (A) below a second predetermined value of said temperature difference (to 2 to 1), delayed in time, a further reduced desired temperature value (SOLL_to 1) of the refrigerant at the evaporator inlet. Arrangement according to at least one of claims 14 to 16, characterized in that a temperature measuring point of the refrigerant on the evaporator side of the evaporator outlet ( 9 ), on the one with the controller ( 16 ) related temperature sensor ( 8th ) is thermally coupled to a heating element. Arrangement according to at least one of claims 14 to 17, characterized in that an internal heat exchanger ( 10 ) in a line of the refrigerant between the evaporator outlet ( 9 ) and a compressor ( 12 ) is arranged, that a pressure line ( 20 ) from the compressor ( 12 ) to a cooled condenser ( 13 ), which via the inner heat exchanger ( 10 ) with the controllable expansion organ ( 5 ) and that the inner heat exchanger ( 10 ) serves as a heating element of the temperature measuring point, which in a line section ( 1 1) between the evaporator outlet ( 9 ) and the inner heat exchanger ( 10 ) is arranged. Arrangement according to at least one of claims 14 to 18, characterized in that a temperature sensor ( 6 ) located at the evaporator inlet ( 4 ) is arranged, each with an input 18 ) of the controller ( 16 ) and the subordinate controller ( 17 ) is in signal- or data-transmitting connection. Arrangement according to at least one of claims 14 to 18, characterized in that a pressure gauge ( 7 ), between the expansion organ ( 5 ) and the evaporator inlet ( 4 ) is arranged, via a pressure / temperature converter with one input of the controller ( 16 ) and the subordinate controller ( 17 ) is in signal- or data-transmitting connection. Arrangement according to at least one of the preceding claims, characterized in that a temperature control liquid temperature sensor ( 3 ) in a bath ( 2 ) of a bath thermostat immersed with the evaporator ( 1 ) is thermally conductively connected, and that the Temperierflüssigkeit temperature sensor ( 3 ) with an input of the controller ( 16 ), which differentiates the Temperierflüssigkeit temperature value (tb) and on the in the controller ( 16 ) according to the said temperature difference (to 2 - to 1) of the refrigerant formed value of the set temperature (SOLL_to 1) of the refrigerant at the evaporator inlet ( 4 ) added up. Arrangement according to at least one of the preceding claims, characterized by a timing control of the regulator ( 16 ), which completes a controller pass after each one controller call. Arrangement according to at least Claims 14 and 22 and optionally at least one of Claims 15 to 21, characterized in that the controller ( 16 ) for establishing the target temperature (SOLL_to 1) of the refrigerant at the evaporator inlet at each controller pass according to the following control algorithm: SOLL_to 1 = SOLL_to 1 old + Δ SOLL_to 1 + gradient tb, where: SOLL_to 1 _{old is} the value of the DESIRED temperature at the end of a previous controller cycle, Δ SOLL_to 1 is the difference value of the DESIRED formed to the end of the current controller cycle compared to the end of the previous controller cycle in accordance with said temperature difference (to 2 - to 1) Temperature, gradient tb the gradient or the time differential of the bath temperature tb. Arrangement according to at least one of the preceding claims, characterized in that the controller ( 16 ) and the subordinate controller ( 17 ) are electronic controllers.