Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B49/00—Arrangement or mounting of control or safety devices
  • F25B49/04—Arrangement or mounting of control or safety devices for sorption type machines, plants or systems
  • F25B49/043—Operating continuously
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
  • F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
  • F25B30/00—Heat pumps
  • F25B30/04—Heat pumps of the sorption type

Definitions

• the present invention relates to an absorption heat pump and a method for operating an absorption heat pump.
• a solution containing a refrigerant is heated in a cooker, for example by means of a gas or oil burner, electrically or with the aid of additional heat exchangers by means of waste heat or solar energy, in order to expel refrigerant as refrigerant vapor from the solution.
• the refrigerant vapor is brought to a high temperature level or high pressure level by this process.
• the refrigerant vapor is then condensed against a heating medium in a condenser and thus supplies the heating medium with heat.
• the strongly cooled and expanded refrigerant is evaporated in an evaporator against a medium that supplies ambient energy to the refrigerant and then fed to at least one absorber.
• the solution depleted of refrigerant from the cooker is fed to the absorber via a heat exchanger, where the solution depleted of refrigerant is combined with refrigerant that has passed through the evaporator.
• the resulting heat of solution is made available to the expeller process and the consumer or is only dissipated to the consumer.
• the resulting refrigerant-rich solution from the absorber is pumped by means of a solution pump from the low-pressure level of the absorber, which corresponds approximately to the evaporation pressure, to a high-pressure level and is returned to the cooker.
• the heating medium heated in the condenser is fed to a consumer and the heating medium cooled by the consumer is returned to the condenser.
• the concentration stratification prevailing in the operation of the absorption heat pump in the cooker is reduced and brought to the level of the low-refrigerant solution.
• a concentration stratification required for the steady-state operating state can be built up in the cooker only by gradually adding rich solution. After switching off the cooker, considerable startup times and energy losses must therefore be accepted when such a system is put back into operation.
• EP-B-0 202 432 proposes a clocking absorption heat pump system in which the high-pressure part and the low-pressure part are blocked by means of solenoid valves in order to minimize the restart losses.
• a disadvantage of this technique is that when the burner output changes, e.g. can be caused by temperature fluctuations, heat pump operation is not always guaranteed.
• the invention is therefore based on the object of providing an absorption heat pump and a method for operating an absorption heat pump of the type described at the outset, in which or in which the energy losses which occur when the absorption heat pump is started up are minimized while reliable operation of the heat pump is nevertheless continuously ensured.
• This object is achieved in a method for operating an absorption heat pump, as defined in the preamble of claim 1, which is based on EP-B-0 202 432, in that the outside temperature and the temperature of the heating medium are measured and the output of the The burner is set as a function of the measured temperature values, that the amount of refrigerant supplied to the evaporator is regulated, that the amount of solution depleted in refrigerant supplied to the at least one absorber is regulated, and that the delivery rate of the solution pump is also regulated.
• an absorption heat pump as defined in the preamble of claim 22, which is also based on EP-B-0 202 432, in that there are further provided: a first control device which arranged one outdoors External sensor for measuring the outside temperature, at least one heating medium sensor for measuring the temperature of the heating medium, and a first controller for regulating the output of the burner as a function of the measured temperature values, a second regulating device for regulating the amount of refrigerant supplied to the evaporator, a third regulating device for regulating the amount of solution depleted in refrigerant supplied to the at least one absorber, and a fourth regulating device for regulating the delivery quantity of the solution pump.
• the solution according to the invention which enables modulating operation of the absorption heat pump by means of the control and regulating circuits mentioned, minimizes unsteady start-up losses, while at the same time ensuring reliable heat pump operation.
• a cycle operation as was provided in the systems proposed in the prior art, is prevented by the modulating technology.
• an absorption heat pump comprises a cooker or expeller 1, in which a solution containing a refrigerant is heated by means of a burner 2 in order to expel refrigerant as refrigerant vapor from the solution.
• the refrigerant vapor is fed in a line 30 via a rectifier 3 to a condenser 13, in which the refrigerant vapor is condensed against a heating medium.
• the heating medium heated in this way is in turn fed into a line 32, the so-called preliminary to a consumer 34, for example a radiator.
• Heating medium which has passed the consumer 34 returns to the absorption heat pump via a line 36, the so-called return.
• the heating medium cooled in the consumer 34 can be heated in an exhaust gas heat exchanger 9 against hot exhaust gas emerging from the burner 2, which is released into the atmosphere at 44 or is otherwise disposed of or processed, before it is fed to an absorber 6.
• the absorber 6 which can be, for example, a plate heat exchanger, the heating medium is fed again in a line 38 to the condenser 13, so that a closed heating medium circuit results.
• the refrigerant which has been greatly cooled and expanded against the heating medium in the condenser 13, is fed in a line 40 to an aftercooler 10, from which it is supplied to an evaporator 11 via a throttle point 12.
• Ambient energy is supplied to the refrigerant in the evaporator 11, which may in particular be heat that is generated in the surroundings (indicated at 42 in FIG. 1) of the building to be heated by the consumer 34, for example in the ground, in water, in air , especially stored in brine.
• Refrigerant which leaves the evaporator 11, is again passed through the aftercooler 10 and from there to the absorber 6.
• the absorber 6 or, as shown in FIG. 1, in a mixer 46 arranged in front of the absorber, the refrigerant is mixed with solvent which has left the cooker 1 via a line 48.
• the resulting heat of solution is made available to the expeller process in the cooker 1 and the consumer 34 or is only dissipated to the consumer 34.
• the refrigerant-rich solution leaving the absorber 6 is pumped after passing through a solution reservoir 7 by means of a solution pump 8 from the low-pressure level of the absorber 6, which corresponds approximately to the evaporation pressure, to a high-pressure level and is fed again to the cooker 1.
• the solution rich in refrigerant can be absorbed by the absorber 6 as shown in FIG. 1 shown are passed over the rectifier 3 and a heat exchanger 4, in which the solution rich in refrigerant is subjected to a heat exchange against the refrigerant vapor leaving the cooker 1 or the solvent leaving the cooker 1.
• Refrigerant, which already condenses in the rectifier 3, is returned to the cooker 1 via a return 50.
• the aim of the absorption heat pump burner control is to achieve burner output control that is adapted to the heat requirements of the building to be heated, in order to ensure continuous operation of the absorption heat pump.
• the concept described here unlike the known systems described at the outset, is based on the knowledge that, with suitable control and regulation of the system, it is quite sensible and energetically worthwhile not to switch off the absorption heat pump entirely when the heating requirement is reduced, but to regulate it down, because the losses that otherwise occur when the system is restarted outweigh the energy savings achieved by the shutdown.
• an external sensor 14 for measuring the ambient temperature and a heating medium sensor for measuring the temperature of the heating medium are provided, wherein the heating medium sensor can be designed as a return sensor 15 for detecting the return temperature or as a flow sensor 16 for detecting the return temperature.
• the outside sensor 14 and the return sensor 15 and / or the flow sensor 16 are connected to a controller 17, the output of which is connected to the burner 2.
• the burner 2 is a controllable burner with a power consumption of, for example, 4 to 18 kW.
• the controller 17 compares the measured return or flow temperature with a setpoint and throttles the burner output when the return or flow temperature approaches the setpoint.
• the regulation can take place according to preset heating curves.
• the burner output can be directly related to the measured outside temperature by assigning certain values for the burner's power consumption to certain outside temperature values. For example, a burner output of 4 kW could be assigned to an outside temperature of +15 ° C, while the burner output should be 13 kW at an outside temperature of -15 ° C.
• the flow and / or the return temperature can also serve as control parameters for the burner output. For example, a return temperature of 25 ° C can be assigned to an outside temperature of +15 ° C, while a return temperature of 45 ° C can be assigned to an outside temperature of -15 ° C.
• the temperature spread of the heating medium i.e.
• the difference between flow and return temperature serve as control parameters.
• the types of control mentioned can be implemented individually or together.
• the burner control described thus modulates the entire heat energy generated by the absorption process to modulate the heat demand of the building to be heated, which can change continuously, for example, through individual settings (e.g. radiators are closed) or due to external influences (variation of solar radiation etc.).
• the condensate throttle is regulated according to the concept described here.
• the condensate throttle control also has the task of avoiding an unnecessarily high condensation pressure and thus contributes to an improvement in the overall efficiency.
• the condensate throttle can take place with the aid of several different control parameters.
• a pressure sensor 18 by means of a pressure sensor 18, the pressure p KKein of the refrigerant vapor entering the condenser 13 is measured.
• This pressure value p KKein can then be converted into a temperature value T KKein with the aid of Ziegler's fundamental equation familiar to the person skilled in the art .
• the temperature value T KKein calculated in this way is then compared with a reference temperature by means of a controller 19, in the illustrated example a PID controller, in order to form an output signal for controlling a continuously controllable actuator.
• a controller 19 in the illustrated example a PID controller
• the temperature T flow of the heating medium emerging from the condenser 13 which is measured by means of a temperature sensor 16. If the temperature difference T KKein - T Vorlauf is less than a predetermined setpoint of, for example, 1 to 4 K, the amount of refrigerant supplied to the evaporator 11 is reduced by means of the adjustable throttle point 12, which can be designed, for example, as a pulse-width modulated valve. If, on the other hand, the said temperature difference is greater than the predetermined target value, the amount of refrigerant supplied to the evaporator 11 is increased. The setpoint ensures that condensate subcooling of approx. 2 to 5 K always occurs. If the difference T KNo - T flow is equal to the specified setpoint, the valve position is optimal.
• FIG. 3 A variant of the condensate throttle control of FIG. 2 is shown in FIG. 3 outlined.
• a temperature sensor 20 is provided here, which detects the temperature T KKaus of the refrigerant emerging from the condenser 13. This temperature T KKaus is in turn compared with the temperature T flow of the heating medium emerging from the condenser 13.
• the prevailing condensate supercooling can be assessed on the basis of the temperature difference between the flow temperature T flow , which corresponds to the condensation temperature, and the temperature T KK from the condensate, which is determined using a controller 19.
• the throttle point 12 can be opened or closed completely or partially based on a comparison between the temperature difference mentioned and this setpoint.
• the setpoint value for the condensate subcooling is preferably in the range between 2 and 5 K.
• FIG. 4 Another variant of the condensate throttle control of FIG. 2 is shown in FIG. 4 shown.
• the embodiment of FIG. 4 differs from that of FIG. 3 in that the temperature of the heating medium is not measured at the outlet of the condenser 13 but at its inlet.
• the temperature T KKaus of the refrigerant emerging from the condenser 13 measured by means of a temperature sensor 20 is then compared with the temperature T HKein of the heating means entering the condenser 13 measured by means of a temperature sensor 21, the controller 19 preferably comprising a difference former for this purpose.
• the temperature difference resulting from the comparison of the two temperatures mentioned can in turn be compared with a Setpoint value compared and the throttle point are regulated depending on this comparison.
• Closing the solution throttle has corresponding opposite effects.
• the temperature T KVein of the refrigerant supplied to the evaporator 11 is measured by means of a temperature sensor 22. With the aid of a second temperature sensor 23, the temperature T KVaus of the refrigerant emerging from the evaporator 11 is detected .
• a PID controller 26 forms a difference from the two measured temperature values and, based on the result of the difference formation, applies an actuating signal to the solution throttle 5.
• the ascertained temperature difference is compared with a predetermined setpoint value, similarly to the methods described above, a particularly preferred range for this setpoint value of 7 to 10 K being achieved in the embodiment described here.
• the solution throttle 5 is closed; If the determined temperature difference is smaller than the specified target value, the solution throttle 5 is opened.
• the regulation of the solution throttle 5 can also be done by measuring the flow temperature, as described with reference to FIG. 2 and 3 has been explained, influenced by the setpoint for the difference between the temperature T KVein the evaporator 11 supplied refrigerant and the temperature T KVaus of the refrigerant emerging from the evaporator 11 is varied depending on the flow temperature T flow .
• control can be designed so that the setpoint for the temperature difference mentioned on the evaporator at a flow temperature of 30 ° C is, for example, 14 K, while this setpoint is lowered to, for example, 7 K at a flow temperature of 50 ° C.
• the temperature T KVein of the refrigerant supplied to the evaporator 11 measured by the temperature sensor 22 is compared with the temperature T MVein of the medium supplied to the evaporator 11 (brine, water, air, etc.) measured by means of a temperature sensor 24. Based on this comparison, the controller 26 delivers an actuating signal to the solution throttle 5 as a function of a predetermined target value.
• FIG. 7 Another variant of the solution throttle control is shown in FIG. 7, wherein the pressure p KVaus of the refrigerant emerging from the aftercooler 10 and the temperature T KVaus of the refrigerant emerging from the evaporator 11 are measured by means of a pressure transducer 28.
• the measured pressure value can then be converted into a temperature value in a manner similar to that described above with reference to the condensate throttle control used here, and can be compared with the temperature value measured by means of the temperature sensor 24.
• the temperature difference determined in this way is then compared with a predetermined target value in order to obtain a control signal for the solution throttle 5.
• the in FIG. The arrangement of the pressure transducer 28 and the temperature sensor 24 shown in FIG.
• both transducers could also be modified such that both transducers are arranged at essentially the same point in the process flow.
• both the pressure transducer 28 and the temperature sensor 24 could be placed between the aftercooler 10 and the mixer 46 or between the evaporator 11 and the aftercooler 10.
• FIG. 8 shows an embodiment of the solution pump control used in the present absorption heat pump concept.
• the solution leaving the absorber 6 and rich in refrigerant after passing through the solution reservoir 7 is pumped by means of a solution pump 8 from the low pressure level of the absorber 6 to a high pressure level and fed again to the cooker 1.
• the exemplary embodiment of the solution pump control shown in FIG. 8 is detected by means of a float 29 arranged in the solution reservoir 7, advantageously a magnetically inductive float, and the fill level of the solution reservoir 7 is detected and, based on the measured fill level, the speed of the solution pump 8 and thus the solution mass flow are adapted to the process.

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• Engineering & Computer Science (AREA)
• Physics & Mathematics (AREA)
• Mechanical Engineering (AREA)
• Thermal Sciences (AREA)
• General Engineering & Computer Science (AREA)
• Sorption Type Refrigeration Machines (AREA)

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Cited By (8)

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• 1999
  • 1999-04-14 DE DE19916907A patent/DE19916907C2/de not_active Expired - Fee Related
• 2000
  • 2000-03-02 EP EP00104384A patent/EP1045214B1/fr not_active Expired - Lifetime
  • 2000-03-02 AT AT00104384T patent/ATE327486T1/de active
  • 2000-03-02 DE DE50012799T patent/DE50012799D1/de not_active Expired - Lifetime
  • 2000-04-11 US US09/547,717 patent/US6332328B1/en not_active Expired - Lifetime

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