EP2320189A2 - Method for operating a recooling circuit with a hybrid cooler for an assembly with discontinuous heat discharge and device for same - Google Patents

Abstract

The method involves spray regulation of a hybrid cooler (2) i.e. dry cooler, and continuously detecting actual operating parameters e.g. actual temperature, of a system (3) i.e. adsorption refrigerator. The detected operating parameters are compared with a preset value in a regulation unit (17). A spray device (18) of the hybrid cooler is activated when reaching and/or exceeding the preset value by the actual detected operating parameters until reaching or exceeding another preset value. The actual temperature within a recooling circuit (1) is detected. An independent claim is also included for a device for operating a recooling circuit.

Description

The invention relates to a method for operating a recooling circuit with a hybrid cooler for a system with a discontinuously occurring heat emission according to the preamble of claim 1 and an apparatus therefor according to the preamble of claim 5.

Recoolers and recirculating cooling circuits are used to dissipate heat from a heat source to the environment. In this case, a recooling medium is used to conduct the heat from the heat source to a heat exchange surface, which is in thermal contact with the environment. For this purpose, a variety of different configurations are known. The heat is transferred to the environment either via a dry recooler, in which the recooling medium flows through pipes within the heat exchange surface and thus transfers the heat to the environment, or via a wet cooler, in which the predominantly formed in the form of water Rückkühlmedium directly evaporated or evaporated , as is the case for example with a cooling tower.

With a hybrid cooler, the principle of dry recooling and wet cooling is combined. In this case, there is a dry recooling, which is supported by water spraying, sprinkling or wetting the cooling surfaces or the surrounding air.

The conventional control of the operation of a hybrid cooler is such that the spray is then put into operation when a certain temperature in the supply air or at the outlet of the recooler is established. Upon activation of the spray, a valve is opened and water is continuously sprayed into the supply air stream. By thus causing lowering of the temperature in the supply air, a higher heat dissipation in the recooling circuit is made possible. The spraying is usually controlled by detecting the temperature at the recooler outlet. This is compared with a predetermined setpoint.

This control method has the disadvantage that the water consumption in the spraying and thus the efficiency of the spray of the recooler can be influenced to a very limited extent. The known control method is designed for continuous spraying. The water consumption is therefore disproportionately large, the constant spraying also leads to dirt and lime deposits in the recooler. This additionally worsens the efficiency of the re-cooling and in turn leads to an additional water consumption during the spraying.

In addition, the regulation of the spray of the recooler proves to be very limited in the currently known methods. For technical reasons, it has a fixed hysteresis which prevents the spraying on and off being timed precisely. The entire control process is thus very slow.

The mentioned disadvantages become particularly serious when systems are to be recooled, which have a discontinuous heat output, which also changes within relatively short time cycles. The conventional recooling control procedures in this case result in the spray being useless in operation whenever it is discharged from the plant no or only a small amount of heat is dissipate. The known spraying control method, because of its inertia, is unable to respond to the changing cyclic heat loads of the plant. As a result, the re-cooling of such a system is inefficient.

It is therefore the object to make a recooling circuit with a hybrid cooler so that it is particularly well suited for systems with a discontinuous heat dissipation. The recooling circuit should be particularly suitable for systems in which the heat transfer within relatively short time cycles changes. The recooling circuit should have a reduced water consumption during the spraying, increase the efficiency of the recooling and ensure an increased life of the components present in the recooling circuit, in particular of the hybrid cooler itself. In conjunction with this, the operating and maintenance costs of the recooling circuit and beyond the system should be lowered and optimized.

The object is achieved with regard to the method aspect according to the teaching for operating a recooling circuit having the features of claim 1 and with regard to the device aspect with a device for operating a recooling circuit having the features of claim 5. The respective subclaims contain expedient and / or advantageous embodiments of the method or the device.

• Es erfolgt ein kontinuierliches Erfassen eines aktuellen Betriebsparameters innerhalb der Anlage. Der so erfasste Betriebsparameter wird mit einem vorgegebenen ersten Wert in einer Regeleinheit verglichen. Eine Besprüheinrichtung des Hybridkühlers wird bei einem Erreichen und/oder Überschreiten des vorgegebenen Wertes durch den aktuell erfassten Betriebsparameter aktiviert, bis ein vorgegebener zweiter Wert erreicht und/oder unterschritten worden ist.

According to the invention, the method for operating a recooling circuit with a hybrid cooler for a system with a discontinuous heat release by spraying the hybrid cooler is characterized by the following method steps:

• There is a continuous recording of a current operating parameter within the system. The operating parameter thus detected is compared with a predetermined first value in a control unit. A Sprühheinrichtung the hybrid cooler is at a reaching and / or exceeding the predetermined Values activated by the currently detected operating parameters until a predetermined second value has been reached and / or fallen below.

The spraying device remains activated as long as the relevant operating parameter is exceeded. Thereafter, the sprayer is deactivated by closing a valve. Alternatively, the valve can be opened or closed during a fixed interval so that the hybrid cooler is sprayed at intervals.

In one embodiment of the process, the discontinuous heat removal plant is an adsorption chiller. The operating parameter in one embodiment of the method is a temperature within the system.

In one embodiment, a continuous detection of a current temperature takes place within a heat carrier circuit of the adsorption refrigeration system. The thus detected current temperature is compared with a predetermined temperature setpoint in a control unit. A spraying device of the hybrid cooler is activated by the control unit when the temperature setpoint is reached and / or exceeded by the current temperature. This activation continues until an undershooting of the temperature setpoint takes place due to the current temperature and is then terminated.

In contrast to the conventional control of the spraying device, which is fed back to the temperature value at the outlet of the recooler, an operating parameter, for example a temperature value, from the system itself is used to control the spraying device. The operation of the spraying device is thus directly coupled with the operating sequences of the system and thus with the heat-generating process occurring there. The spraying device thus reacts directly to the operating processes and thus to the heat generation within the system. As a result, the response times of the control of the sprayer are significantly shortened, so a true discontinuous and / or cyclical operation of the spraying device according to the discontinuous heat generation within the plant is executable. The spraying device thereby reacts in particular to operating cycles running within the system and is coupled to these. Thus, the amount of water consumed for spraying and thus the stress on the hybrid cooler is lowered sustainably and set the recirculation circuit in an effective manner to the heat load delivered by the system.

The plant can be designed as an adsorption chiller. In this case, the currently detected operating parameter is detected within an evaporator in a cold water circuit or a condenser in the adsorption refrigerator. When the operating setpoint is reached and / or exceeded, a switching signal for opening a valve in the spraying device is output via a control unit until the desired value of the operating parameter sets again or a maximum spraying time has been exceeded.

Adsorption chillers are characterized by a discontinuously generated and cyclic heat output. For such purposes, the inventively operated Rückkühlkreislauf is thus particularly advantageous.

On the device side, the recooling circuit with hybrid cooler according to the invention for a system with a discontinuous heat output by a sensor device for detecting an operating parameter within the system, a control unit coupled to the sensor device with a comparison member and a valve coupled to the control unit in a spraying of the hybrid radiator.

In an advantageous embodiment, the plant is an adsorption refrigerating machine, wherein the temperature sensor is arranged in the region of a secondary side of an adsorber, condenser and / or evaporator of the refrigerating machine is. The hybrid radiator in one embodiment is configured as a dry recooler with ventilation and spraying in the direction of ventilation.

The method and the device for carrying out the method will be explained in more detail below on the basis of exemplary embodiments. To clarify serve the FIGS. 1 to 5 , The same reference numerals are used for identical and / or equivalent parts.

Fig. 1

eine Darstellung einer zyklischen Arbeitsweise einer Adsorptionskältemaschine,

Fig. 2

eine Darstellung eines beispielhaften Rückkühlkreislaufs im Überblick,

Fig. 3

eine zweckmäßige Ausführungsform eines beispielhaften Hybridkühlers,

Fig. 4

eine Darstellung eines Temperaturverlaufs am Austritt eines Hybridkühlers unter dem Einfluss einer zeitlich diskontinuierlichen Wärmelast mit und ohne Besprühungsintervalle und

Fig. 5

eine Darstellung einer Maschinenarbeitszahl einer rückgekühlten Adsorptionskältemaschine in Abhängigkeit von einer Außentemperatur mit und ohne Besprühung.

Hereby show:

Fig. 1

a representation of a cyclic operation of an adsorption chiller,

Fig. 2

a representation of an exemplary recooling cycle at a glance,

Fig. 3

an expedient embodiment of an exemplary hybrid cooler,

Fig. 4

a representation of a temperature profile at the outlet of a hybrid cooler under the influence of a time-discontinuous heat load with and without Sprühungsintervalle and

Fig. 5

a representation of an engine operating coefficient of a recooled adsorption refrigeration machine as a function of an outside temperature with and without spraying.

The method according to the invention is illustrated by way of example below on the basis of an operation of a recooling circuit, in particular a recooling water circuit, coupled to an adsorption refrigerating machine. As for all thermally driven refrigeration systems, efficient and efficient re-cooling of the supplied drive energy and the generated cooling energy is also of great importance for such systems. The one from the machine Therefore, reusable energy in the form of heat, which can no longer be utilized, must be efficiently removed via the recooling circuit and via a heat exchange. For this purpose circulates in the recooling circuit, a heat carrier, which consists for example of water or a mixture of water and glycol.

Due to the heat absorption in the machine, the heat carrier temperature in the recooling circuit increases. The heat transfer medium is cooled down to a lower temperature level along the recooling circuit and in particular on a cooler designed as a heat exchanger. He is then the refrigeration system thus for the new heat absorption available. The efficiency and performance of the recooling circuit depend on the outside temperature, the type of cooler used, its peripheral components and the refrigeration system itself.

Fig. 1 shows a representation of the cyclic operation of a Adsorptionskältemaschine. The characteristic discontinuous mode of operation of the machine is characterized by the structure and the changing processes of adsorption and desorption. In order to keep the machine operating as continuously as possible, adsorption and desorption processes are alternately carried out in two adsorbers. In the outlet temperature of a heat transfer medium circuit shown in the curve C, the fluctuations are extremely steep and occur cyclically. These fluctuations are also reflected in a damped form at the inlet temperature of the heat transfer circuit at the curve D. The cyclical operation of the machine is particularly clearly expressed in the course of a cooling capacity shown by the curve E. In the example shown here, a maximum cooling capacity of 8 kW and a minimum cooling capacity of 2 kW is achieved.

The outside temperature represented by the curve F shows up to a point X a course with natural fluctuations. The sudden increase in the outside temperature at point X is due to incident solar radiation. The increase in the outside temperature has a delayed rise in the inlet temperature at curve D and outlet temperature at curve C of the heat transfer circuit result. The reduction of the cooling capacity at curve E after point X is due to the temperature increase in the circuit.

FIG. 2 shows an exemplary recooling circuit 1 provided for the adsorption refrigerating machine 1, FIG. 3 an exemplary embodiment of a circuit connected hybrid cooler.

The recooling circuit contains a suitably arranged outdoors hybrid cooler 2 and a system 3, for example, a Adsorptionskältemaschine with in Fig. 1 shown operating cycles, which gives off intermittently heat to the recooling circuit. The heat carrier flowing in the recooling circuit flows via a feed line 4 from the system into the hybrid cooler. There he transfers the heat absorbed by the system to the ambient air. For this purpose, a cooling element 5 is provided in a lamellar construction, which offers a particularly good thermal contact with the environment.

The cooled in the hybrid cooler heat carrier flows back through a return line 6 to the plant. For circulating the heat carrier within the recooling circuit, a pump 7 is provided. The flow of the heat carrier in the recooling circuit can be regulated via a series of valves. About arranged in the vicinity of the pump check valves 10, the flow can be locked if necessary. An associated with the recooling circuit reservoir and expansion tank 11 compensates for pressure fluctuations.

Within the system cooled by the recooling circuit, a process medium flows within a process cycle. In the case of an adsorption chiller, the process cycle corresponds to the cycle of the adsorbed and desorbed refrigerant which is customary in such systems. This exchanges heat via arranged in the circuit heat exchanger, in particular a condenser 13, two adsorbers 14 and an evaporator 15 with adjacent operating components.

For this purpose, the evaporator 15 is thermally coupled to an external cold water circuit (not shown here). This includes, for example, a cooling ceiling or a cooling coil. These facilities are not shown here.

The adsorbers 14 are in turn thermally coupled to an external hot water circuit containing, for example, a solar storage, not shown here, a district heating device or a waste heat of a combined heat and power plant.

At various points on the secondary sides of the heat exchangers or in the recooling circuit, temperature sensors 16 are provided, in particular in the region of the condenser, the evaporator and / or the adsorber. These pass the operating parameters detected at these locations, i. the temperature values measured in this example, to a control unit 17.

The hybrid cooler already mentioned is a dry hybrid cooler with a spraying device 18 and a ventilation system 19. The spraying device consists of a nozzle arrangement 20 arranged below the cooling element 5, which is supplied with cold water from a supply line 21. The water supply via the supply line can be released or shut off via a check valve 22. The opening state of the check valve is determined by the control unit 17 via a control line 17a and the transmitted via this line electrical switching signals. The check valve is for this purpose designed as an electrically switchable valve, for example as a solenoid valve.

In the structure of the hybrid cooler present here, ambient air is sucked in through the ventilation. This flows through the cooling element and exits the hybrid cooler again. In the dry recooler with spray in the direction of ventilation, the nozzle arrangement is in the form of a nozzle block under the cooling element. The sucked ambient air thus flows first through the nozzle and rips the water sprayed there with it. By spraying water in the flow direction of the air flow the cooling element is wetted on its surface. An evaporation effect which occurs in the air volume flow and on the surface of the finned heat exchanger wall of the cooling element makes it possible to cool the heat carrier to a temperature which is below the ambient temperature. As a result, the cooling of the heat carrier in the recooling circuit is intensified. About the switching state of the check valve, the spray can be activated or deactivated and thus the effectiveness of the cooling can be adjusted.

Fig. 4 shows the effect of discontinuous spraying using an exemplary diagram. The diagram shows the time course of an exit temperature at the recooler under the influence of a discontinuous heat load during a work cycle of the adsorption chiller. This essentially repeats periodically.

The curve A shows the temperature profile of the outlet temperature from the recooler without spraying, the curve B indicates the temperature profile of the outlet temperature with Besprühung. In the example shown here, the spraying is carried out during the working cycle within two time intervals t _S1 . From the course of curve A, it can be seen that the temperature at the outlet of the recooler initially reaches a maximum which asymptotically decreases with time due to the incipient action of the recooler against a limit value.

As the curve B shows, the initial temperature maximum is considerably reduced by the spraying during the first time interval t _S1 . The temperature curve then shows a much flatter course. In contrast to the temperature profile in curve A, the initial temperature present at the time t = 0 can be quickly reached again by a subsequent spraying, again taking place within a time interval t _S1 . The short-term spraying in the two time intervals is thus sufficient to smooth the temperature profile at the outlet of the hybrid cooler and thus a constant cooling capacity of the hybrid cooler to ensure a discontinuous heat load. The spraying performed only within the time intervals is sufficient to effectively dissipate the discontinuously supplied heat.

This effect is caused by the reduced temperature of the ambient air sucked in by the ventilation due to the spraying. The temperature profile of the ambient air is represented by the curve B '.

The beginning and the duration of the respective time intervals t _S1 are determined by the control unit. The spraying then starts when the temperature T reaches or exceeds a desired value T _soll at a point in the refrigeration cycle of the adsorption chiller. It is then turned off and the valve 22 is closed when the predetermined operating parameters, in this case, the target value T _set, has fallen again. The strong flattening of the curve B in comparison to A is explained by the fact that the spraying of the cooling element in the hybrid cooler already starts before the now more heated heat transfer medium has reached the cooling element via the supply line. As a result, the cooling element is already wetted and can thus absorb the heat introduced by the heat transfer medium very effectively.

As can also be seen from the diagram, the spraying thus starts at a point in time when the temperature of the heat carrier is still rising. The minimum reached in the curve B 'of the air temperature during the time interval t _S1 thus coincides with the rising portion of the curve B of the outlet temperature. The effectiveness of regulated by the control unit intermittent spraying thus results primarily from the fact that the temperature rise of the heat carrier in the return cooling circuit is met timely and already at the beginning.

An experimentally performed comparison of the mentioned Sprühart for the hybrid chiller with the conventional operation of a quasi-continuous spraying shows that in the execution of the latter, a significantly larger amount of water is consumed. Compared to the conventional mode of operation In the method according to the invention, the water consumption during the spraying is reduced to about one seventh.

Fig. 5 shows the beneficial influence of in Fig. 4 illustrated embodiment of the spraying on a machine operating a adsorption chiller with such operated recirculating cooling circuit at different ambient temperatures. The machine operating rate is a measure of the effectiveness of the adsorption chiller. It indicates the ratio between the heat pumped by the adsorption chiller and the energy required for it. A high machine operating count thus means a high efficiency of the refrigeration system.

The graph shows that the machine operating count is expected to decrease as the outside temperature increases. It reaches a value of less than 10 without spraying at a temperature of 26 ° C. At this temperature the spraying follows according to the procedure Fig. 3 put into operation, the machine work rate increases significantly to a value of 15 and thus to one and a half times.

The method and the device according to the invention were explained in more detail by means of exemplary embodiments. In the context of professional action, further embodiments of the method and the device are possible. These remain all within the scope of the inventive concept. Further embodiments emerge from the subclaims.

LIST OF REFERENCE NUMBERS

1

Rear cooling circuit

2

hybrid cooler

3

Plant with discontinuous heat emission

4

leader

5

cooling element

6

returns

7

pump

10

check valves

11

Reservoir and expansion tank

13

capacitor

14

adsorber

15

Evaporator

16

temperature sensor

17

control unit

17a

control line

18

Spraying Device

19

ventilation

20

nozzle assembly

21

supply line

22

check valve

A

Exit temperature without spraying

B

Exit temperature with interval spray

B '

Temperature of the ambient air

C

Cyclically varying outlet temperature in the heat transfer circuit of an AKM

D

cyclically varying inlet temperature in the heat transfer circuit of the AKM

e

cyclically varying cooling capacity of the AKM

Claims (8)

Method for operating a recooling circuit (1) with a hybrid cooler (2) for a system (3) with a discontinuous heat output,
marked by
a spraying of the hybrid cooler with the following process steps: continuous detection of a current operating parameter of the plant, Comparison of the acquired operating parameter with a predetermined first value in a control unit (17), - Activating a spraying device (18) of the hybrid cooler when reaching and / or exceeding the predetermined value by the currently detected operating parameters until reaching or exceeding a predetermined second value. Method according to claim 1,
characterized in that
the plant (3) is an adsorption chiller. Method according to claim 1 or 2,
characterized in that
the currently detected operating parameter is a temperature (T) in the system. Method according to one of the preceding claims,
characterized in that - The current temperature (T) is detected within a heat transfer circuit and - When reaching and / or exceeding the temperature setpoint (T _soll ) via a control unit, a switching signal to open a valve the spraying device _is output until it falls below the temperature setpoint (T _soll ). Device for operating a recooling circuit (1) with a hybrid cooler (2) for a system (3) with discontinuous heat dissipation, characterized by
a sensor device (16) for detecting an operating parameter within the system, a control unit coupled to the sensor device with a comparison element and a valve (22) coupled to the control unit in a spraying device of the hybrid cooler. Device according to claim 5,
characterized in that
the system is an adsorption chiller, wherein the sensor device (16) is designed as a temperature measuring device arranged on the evaporator and / or condenser of the adsorption chiller. Device according to one of claims 5 and 6,
characterized in that
a temperature sensor (16) within a heat carrier circuit of the system, a control unit (17) coupled to the temperature sensor with a comparison element and a switching unit and a valve (22) coupled to the switching unit is provided in a spray device (18) of the hybrid cooler. Device according to one of the preceding claims,
characterized in that
the hybrid cooler (2) is designed as a dry recooler with ventilation and spraying in the ventilation direction.

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