JP2006226655A - Compression type heat pump system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compression type heat pump system capable of suppressing deterioration of COP following dropping of a heat source temperature of an evaporator while generating sufficient heat to suppress heat shortage. <P>SOLUTION: The compression type heat pump system is provided with a refrigerant circuit 1 circulating a refrigerant X comprised of carbon dioxide through each of a compressor 2, a condenser 3, an expansion valve 4, and the evaporator 5 in this order. A prime mover 10 is provided for driving the compressor 2, and an exhaust heat recovery part 20 is provided for recovering heat from combustion exhaust gas E exhausted from the prime mover 10. It is composed to supply combustion exhaust gas E' exhausted from the exhaust heat recovery part 20 as a heat source for the evaporator 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  According to the present invention, a refrigerant composed of carbon dioxide includes a compressor that compresses the refrigerant, a condenser that dissipates heat from the refrigerant, an expansion valve that expands the refrigerant, and an evaporator that absorbs heat from the refrigerant. The present invention relates to a compression heat pump system including a circulating refrigerant circuit.

  As a compression heat pump system as described above, in recent years, from the viewpoint of protecting the ozone layer and preventing global warming, a natural refrigerant such as carbon dioxide is used instead of an artificial refrigerant such as Freon, and the operating pressure of the compressor ( That is, the refrigerant discharge pressure) is set to the supercritical pressure of the natural refrigerant, and the carbon dioxide is condensed from the evaporator by utilizing heat absorption / radiation when changing the state between the gas phase and the gas-liquid two-phase state. A compression heat pump apparatus that operates in a supercritical heat pump cycle that forcibly moves heat to the vessel side has been put into practical use (see, for example, Patent Document 1).

  A conventional compression heat pump apparatus using carbon dioxide as a refrigerant can supply air to the evaporator as a heat source, and can heat the hot and cold water to a relatively high temperature (80 ° C. to 95 ° C.) in the condenser. As widely sold.

  On the other hand, a prime mover such as an internal combustion engine that drives a generator to generate electric power, such as a hot water heating section that heats hot water by heat exchange with a relatively high-temperature combustion exhaust gas discharged from the prime mover. A waste heat recovery unit that recovers the heat of the combustion exhaust gas discharged from the engine, and is configured to effectively use the heat generated by the power generation by the prime mover for hot water heating for hot water supply or heating. A generation system is known (see, for example, Patent Document 2).

JP 2004-132606 A JP 2004-263589 A

In the cogeneration system, the prime mover aims to improve the power generation efficiency in the power generation unit, and the efficiency is improved. However, the higher the efficiency, the lower the overall efficiency (the sum of power generation efficiency and heat recovery efficiency). There is a tendency.
Therefore, in some cases, there is a so-called heat shortage in which the amount of heat that can be generated in the exhaust heat recovery unit is insufficient with respect to the heat demand. In this case, if the fuel is newly burned by a boiler or the like to compensate for the heat, In some cases, the effect of improving the power generation efficiency in the section is reduced by the fuel consumption in the boiler.

  Therefore, in such a cogeneration system, for example, a compressor is provided with a compression heat pump system configured to drive the compressor with the power generation output of the prime mover, and the heat recovered in the exhaust heat recovery unit is generated in the condenser. It may be configured to compensate for heat.

However, in a conventional compression heat pump apparatus that supplies atmospheric air as a heat source for an evaporator, a coefficient of performance (indicated by a ratio of heating heat to work applied to the compressor is shown. ")" Depends on the temperature of the atmosphere as a heat source, and the COP decreases as the temperature decreases. Furthermore, when the temperature of the atmosphere is low, defrosting in the evaporator is also necessary, which is a factor that further reduces COP.
Therefore, even if such a compression heat pump system is provided in the cogeneration system, the total efficiency may not be sufficiently improved due to the above-described problem of COP reduction.

  The present invention has been made in view of the above problems, and its purpose is to generate sufficient heat to suppress the occurrence of heat shortage, but to reduce the COP accompanying the decrease in the heat source temperature of the evaporator. It is in the point which provides the compression type heat pump system which can be suppressed.

In order to achieve the above object, a compression heat pump system according to the present invention comprises a compressor in which carbon dioxide refrigerant compresses the refrigerant, a condenser that radiates heat from the refrigerant, and an expansion valve that expands the refrigerant. , A compression heat pump system provided with a refrigerant circuit that circulates in the order of the evaporator that absorbs heat into the refrigerant, the first feature of which is a prime mover that burns fuel and outputs the driving force of the compressor When,
An exhaust heat recovery unit that recovers heat from the combustion exhaust gas discharged from the prime mover,
The combustion exhaust gas discharged from the exhaust heat recovery unit is configured to be supplied as a heat source of the evaporator.
In the present application, the prime mover refers to one that converts combustion energy of fuel into mechanical energy or electrical energy that is used as a driving force of the compressor.

  According to the first characteristic configuration, by providing a prime mover that burns the fuel and outputs the driving force of the compressor, in addition to the heat radiation from the refrigerant in the condenser, the exhaust heat recovery unit recovered from the combustion exhaust gas. Heat can be generated and generation of heat shortage can be suppressed.

  In addition, although the relatively low-temperature combustion exhaust gas discharged from the exhaust heat recovery unit has recovered heat in the exhaust heat recovery unit but is maintained at a higher temperature than the atmosphere, the combustion exhaust gas is used as a heat source in the evaporator. As a result, the evaporating temperature of the refrigerant in the evaporator is increased, the COP is improved, and further, there is no need for defrosting in winter.

In addition, the combustion exhaust gas discharged from such an exhaust heat recovery unit contains a large amount of water vapor generated by burning the fuel, and the dew point of the water vapor is higher than the boiling point of the refrigerant in the evaporator. Therefore, in the evaporator, heat exchange between the combustion exhaust gas and the relatively low temperature refrigerant absorbs the latent heat of condensation of the water vapor to the refrigerant side in addition to the sensible heat of the combustion exhaust gas. In addition, the heat recovery efficiency with respect to the calorific value of the fuel is improved.
Furthermore, in the evaporator, the combustion exhaust gas side is in the form of condensation heat transfer, and the refrigerant side is in the form of evaporation heat transfer, so the overall heat transfer coefficient can be kept high, and the temperature difference can be relatively large. The evaporator can be made considerably smaller than when the atmosphere is supplied as a heat source.

  A second characteristic configuration of the compression heat pump system according to the present invention is that, in addition to the first characteristic configuration, the prime mover is configured to perform lean combustion in an excess air state of fuel.

  In a prime mover, for example, in order to achieve high thermal efficiency and low NOx, when the fuel is lean-burned in an excess air state, the dew point of water vapor contained in the combustion exhaust gas discharged from the prime mover decreases to about 40 ° C., for example. Therefore, it is difficult to recover the latent heat of condensation of water vapor in the exhaust heat recovery unit. Therefore, according to the second characteristic configuration, the combustion exhaust gas discharged from the exhaust heat recovery unit is supplied as a heat source of the evaporator, so that the refrigerant also absorbs the condensation latent heat of water vapor with such a low dew point. It can be recovered.

The third characteristic configuration of the compression heat pump system according to the present invention includes hot water that heats hot water by heat exchange with the combustion exhaust gas as the exhaust heat recovery unit in addition to any of the first to second characteristic configurations. With a heating section,
The condenser is configured to heat hot water supplied to the hot water heater by heat exchange with the refrigerant.
In the present application, the hot water may be a relatively warm water or a relatively low temperature water.

  According to the third characteristic configuration, the hot water heated by the condenser can be heated to a higher temperature by heat exchange with the hot combustion exhaust gas in the hot water heating section, and can be effectively used for hot water supply and heating. Can produce hot and cold water. In addition, since the heating temperature of the hot water in the condenser can be kept relatively low, the operating pressure of the compressor can be made relatively low in a compression heat pump system using carbon dioxide as a refrigerant. A small and inexpensive one can be used, and further, the power of the compressor can be reduced to improve energy saving.

  According to a fourth feature of the compression heat pump system of the present invention, in addition to any of the first to third features, the exhaust heat recovery unit is supplied to the prime mover by heat exchange with the combustion exhaust gas. It is in the point provided with the air preheating part which preheats the combustion air.

  According to the fourth characteristic configuration, the output of the prime mover is improved by providing the air preheating part and performing so-called heat regeneration for preheating combustion air supplied to the prime mover by heat exchange with the combustion exhaust gas. Can do.

According to a fifth feature of the compression heat pump system according to the present invention, in addition to any of the first to fourth features, the prime mover comprises an internal combustion engine.
The compressor is driven by shaft output or power generation output of the internal combustion engine.

  According to the fifth characteristic configuration, when the engine is provided with an internal combustion engine such as a reciprocating engine or a gas turbine engine, the compressor is driven by the shaft output of the internal combustion engine, or The compressor can be driven in such a form that the motor for driving the compressor is operated by the power generation output of the generator that generates power by the shaft output of the internal combustion engine.

In a sixth feature configuration of the compression heat pump system according to the present invention, in addition to any of the first to fourth feature configurations, the prime mover heats a thermoelectric generator that performs thermoelectric generation using the Seebeck effect. Consisting of a combustor,
The compressor is driven by the power generation output of the thermoelectric generator.

  According to the sixth characteristic configuration, when the combustor for heating the thermoelectric generator is provided as the prime mover, the compressor driving motor is operated by the power generation output of the thermoelectric generator. Can be driven.

An embodiment of a compression heat pump system according to the present invention will be described with reference to the drawings.
As is well known, the compression heat pump system shown in FIGS. 1, 2, and 3 includes a compressor 2 that compresses the refrigerant X by a refrigerant X that is carbon dioxide as a natural refrigerant, and a condenser that radiates and condenses the refrigerant X. 3, an expansion valve 4 that expands and depressurizes the refrigerant X, and an evaporator 5 that absorbs the refrigerant X to absorb heat and evaporate the refrigerant circuit 1.

  In such a compression heat pump system using carbon dioxide as the refrigerant X, the operating pressure of the compressor 2 (that is, the discharge pressure of the refrigerant X) is set to the supercritical pressure of the natural refrigerant, and the refrigerant X is in a gas phase state and a gas-liquid state. It operates in a supercritical heat pump cycle in which heat is forcibly transferred from the evaporator 5 to the condenser 3 side by utilizing heat absorption / radiation when changing the state between the two-phase states. Specifically, in the refrigerant circuit 1, the refrigerant X in a gas phase is compressed by the compressor 2 to high temperature and high pressure, and the high temperature and high pressure refrigerant X is cooled by dissipating heat in the condenser 3. The pressure is reduced by the expansion valve 4 to make a gas-liquid two-phase state, and the refrigerant X in the gas-liquid two-phase state is absorbed by the evaporator 5 to be heated to a gas phase state. As for this configuration, a configuration similar to a compression heat pump system that operates in a known supercritical heat pump cycle can be employed.

A prime mover 10 that outputs the driving force of the compressor 2 and an exhaust heat recovery unit 20 that recovers heat from the combustion exhaust gas E discharged from the prime mover 10 are provided. Therefore, in addition to heat radiation from the refrigerant X in the condenser 3, heat recovered from the combustion exhaust gas E is generated in the exhaust heat recovery unit 20.
The prime mover 10 will be described in detail later, but as shown in FIG. 1, a gas turbine engine 11 that is an internal combustion engine that generates shaft output by burning fuel G with air A (first embodiment). 2 or a reciprocating engine 12 (second embodiment) that is an internal combustion engine that generates shaft output by burning fuel G with air A as shown in FIG. 2, or fuel G as shown in FIG. A combustor 13 (a third embodiment) that heats the thermoelectric generator 13a by burning with air A is employed.
Further, the prime mover 10 is configured to generate power by a generator 16 or a thermoelectric generator 13a driven by a shaft output, and this generated output is supplied to the drive motor 2 ′ to be supplied to the refrigerant circuit 1. It can be used for driving the provided compressor 2.
When there is a sufficient power generation output, power other than that used by the drive motor 2 ′ may be used by another power consumption unit.

Further, the combustion exhaust gas E ′ having a temperature higher than that of the air discharged from the exhaust heat recovery unit 20 is supplied as a heat source of the evaporator 5.
That is, the combustion exhaust gas E discharged from the prime mover 10 is supplied to the exhaust heat recovery unit 20 to recover the high temperature side heat, and then supplied to the evaporator 5 of the refrigerant circuit 1 to recover the low temperature side heat. And then discharged from the chimney.

  The combustion exhaust gas E ′ after the high-temperature side heat is recovered in the exhaust heat recovery unit 20 contains more than 10% of the calorific value of the fuel G (total calorific value reference). Since 'is supplied to the evaporator 5 as a heat source, the evaporation temperature of the refrigerant X in the evaporator 5 is increased, the COP in the compression heat pump system is improved, and further, there is no need for defrosting in winter.

  In addition, the combustion exhaust gas E ′ discharged from the exhaust heat recovery unit 20 and supplied to the evaporator 5 as a heat source in this manner contains a large amount of water vapor generated by the combustion of the fuel G. Since the dew point of the refrigerant is higher than the boiling point of the refrigerant in the evaporator, when heat exchange is performed between the combustion exhaust gas E ′ and the relatively low-temperature refrigerant X in the evaporator 5, the sensible heat of the combustion exhaust gas E ′ In addition to this, the latent heat of condensation of water vapor is absorbed by the refrigerant X, which further improves COP and further improves the heat recovery efficiency with respect to the heat generation amount of the fuel G.

  Further, since the condensed water C generated by condensation of water vapor in the combustion exhaust gas E ′ in the evaporator 5 is acidic and corrosive, the evaporator 5 has a corrosion resistant material (for example, stainless steel (SUS316L, etc.), titanium, etc. ) Is desirable. When the amount of heat is insufficient with only the combustion exhaust gas E ′ as the heat source of the evaporator 5, for example, the evaporator 5 is divided into two parts and connected in series, and is connected to the upstream evaporator 5 in the flow direction of the refrigerant X. It is also possible to supply the atmosphere as a heat source and supply the combustion exhaust gas E ′ as a heat source to the evaporator 5 on the downstream side.

In this way, the exhaust heat recovery unit 20 and the evaporator 5 recover the heat of the combustion exhaust gas E discharged from the prime mover 10 in that order, so that the heat generation amount of the fuel G can be reduced to about 98% on the basis of the total heat generation amount. Can be recovered and energy saving can be achieved.
It is very high if the retained heat of the low-temperature combustion exhaust gas E ′ discharged from the exhaust heat recovery unit 20 is considered as valuable as the heat stored in the outside air because the combustion exhaust gas E ′ has been discarded in the past. COP (for example, 5 to 8) can be realized.

  Further, when the prime mover 10 is configured so that the fuel G is lean burned in an excess air state (for example, an air ratio of 1.4 or more) in order to achieve, for example, high thermal efficiency and low NOx, the prime mover 10 is discharged from the prime mover 10. The dew point of water vapor contained in the combustion exhaust gas E is relatively low (for example, about 40 ° C.). Therefore, it is difficult to recover the condensing latent heat of the water vapor in the exhaust heat recovery unit 20, but in the evaporator 5, the boiling point of the refrigerant X is lower than its dew point (the critical temperature is about 30 ° C.). The latent heat of condensation of the combustion exhaust gas E can be efficiently recovered by the low-temperature refrigerant X.

The exhaust heat recovery unit 20 is provided with a hot water heating heat exchanger 21 as a hot water heating unit that heats the hot water W by heat exchange with the combustion exhaust gas E, and the condenser 3 is connected to the refrigerant X. The hot water W supplied to the hot water heating heat exchanger 21 is heated by heat exchange.
That is, the hot water W is heated to a higher temperature by heat exchange with the hot combustion exhaust gas E in the hot water heating heat exchanger 21 after being heated in the condenser 3, and such hot hot water is stored in the hot water. Once stored in the tank 6, it can be effectively used for hot water supply and heating.

  The hot water storage tank 6 is configured to store hot water W in a state where temperature stratification is formed. That is, the hot water W taken out from below the hot water storage tank 6 by operating the circulation pump 7 in a state where the low temperature clean water W0 (tap water) is supplied below the hot water storage tank 6 is used for heating the condenser 3 and hot water. Heated by the heat exchanger 21 and supplied again above the hot water storage tank 6, and hot water is supplied by the circulation pump 7 so that the temperature of the hot water W supplied above the hot water storage tank 6 is about 80 ° C. to 90 ° C., for example. By controlling the circulating amount of W, the hot water storage tank 6 stores hot water W in a form that forms a so-called temperature stratification in which hot water W is present in the upper part and hot water W is present in the lower part. Become.

Further, the hot water W stored above the hot water storage tank 6 is mixed with the low temperature water W0 so as to be appropriately set by the mixing valve 8 and then supplied to the hot water supply section 9 for hot water supply. Used for
Although not shown in the drawing, the circulating water for bath reheating or heating is heated above the hot water storage tank 6 in such a form that it is heated by heat exchange with the hot water W stored in the hot water storage tank 6. The stored hot water W can be used for bathing and heating.

  Next, the first, second, and third embodiments that are mainly different in the detailed configuration of the prime mover 10 will be described.

[First Embodiment]
The compression heat pump system of the first embodiment shown in FIG. 1 includes a gas turbine engine 11 as a prime mover 10.
Such a gas turbine engine 11 compresses air A with an air compressor 11a driven by utilizing a part of shaft output, and uses the compressed air A with a combustor 11b to dilute fuel G in an excess air state. Combustion is performed, the expansion turbine 11c is driven by the combustion gas to generate a shaft output, and the generator 16 is driven by the shaft output to generate power.

  Further, the gas turbine engine 11 needs to suppress the inlet combustion gas temperature (TIT) of the expansion turbine 11c below the heat resistance temperature (about 900 ° C.) of the blades of the expansion turbine 11c. The combustion gas temperature is equal to or lower than the heat-resistant temperature by dilute combustion in an excess air state and diluting the combustion gas with air A supplied from the air compressor 11a to the cooling passage 11d formed around the combustor 11b. Is suppressed.

  Further, as the exhaust heat recovery unit 20 that recovers heat from the combustion exhaust gas E exhausted from the gas turbine engine 11, the combustion air A supplied to the combustor 11b of the engine 11 by pre-heat exchange with the combustion exhaust gas E is preheated. A regenerative heat exchanger 22 is provided as an air preheating unit that performs such heat regeneration, thereby improving the shaft output.

Therefore, the combustion exhaust gas E exhausted from the gas turbine engine 11 is first subjected to heat exchange with the combustion air A in the regenerative heat exchanger 22 as the exhaust heat recovery unit 20, thereby causing 300 ° C. to 400 ° C. It becomes about 150 ° C. by heat exchange with the hot water W in the hot water heating heat exchanger 21 as the exhaust heat recovery unit 20.
And even in the comparatively low-temperature combustion exhaust gas E ′ discharged from the regenerative heat exchanger 22 and the hot water heating heat exchanger 21 as the exhaust heat recovery unit 20, the combustion exhaust gas E ′ is used as a heat source for the evaporator 5. As a result, it is possible to efficiently recover the retained heat of the combustion exhaust gas E ′ and obtain a high overall efficiency (90% or more based on the total calorific value).

  As the gas turbine engine 11, in addition to the uncooled gas turbine as described above, MGT: micro gas turbine, UMGT: ultra micro gas turbine, or the like can be adopted.

[Second Embodiment]
The compression heat pump system of the second embodiment shown in FIG. 2 includes a reciprocating engine 12 as the prime mover 10.
Such a reciprocating engine 12 performs lean combustion of an air-fuel mixture of fuel G and air A in an excess air state in a combustion chamber, discharges combustion exhaust gas E generated by the combustion, and generates a shaft output from a crankshaft. The generator 16 is driven to generate power.

The engine 12 has a circulation pump 24 that circulates cooling water (jacket water) and heat exchange between the cooling water and the hot water W to cool the cooling water and heat the hot water W. A water heat dissipating heat exchanger 23 is provided.
Further, the cooling water radiating heat exchanger 23 is disposed so as to heat the hot water W discharged from the condenser 3 and flowing into the hot water heating heat exchanger 21. It is also possible to change depending on the take-out temperature.

[Third Embodiment]
The compression heat pump system of the third embodiment shown in FIG. 3 includes a combustor 13 that heats a thermoelectric generator 13a that performs thermoelectric generation using the Seebeck effect as a prime mover 10.
Similar to the second embodiment, the combustor 13 is configured to combust the fuel G with the air A preheated by the regenerative heat exchanger 22 and discharge the combustion exhaust gas E.

  Further, a cooler 13b for cooling the surface of the thermoelectric generator 13a opposite to the combustor 13 is provided. The cooler 13b is discharged from the condenser 3 and is a hot water heating heat exchanger 21. The thermoelectric generator 13a is cooled by exchanging heat with the hot water W flowing in.

  That is, the thermoelectric generator 13a faces one side of the combustor 13 and is heated by the combustion heat of the fuel G, and the other side is cooled by the cooler 13b, thereby generating a temperature difference and increasing the Seebeck effect. To generate electricity.

  Moreover, since the upper limit of the temperature on the high temperature side is determined from the temperature restriction of the material of the thermoelectric generator 13a, the combustor 13 causes the fuel G to perform lean combustion in an excess air state so that the temperature is lower than that temperature. It is configured.

The combustor 13 can also be configured to catalytically burn the fuel G.
Further, in the form in which the combustor 13 is combined with the regenerative heat exchanger 22, the flow path through which the mixture of the fuel G and the air A flows and the flow path through which the combustion exhaust gas E flow are adjacent to each other to heat each other. It may be configured as a so-called Swiss roll burner or the like that is arranged in a state in which the adjacent pair of flow paths swivel by functioning as a regenerative heat exchanger 22 by enabling exchange.

  The compression heat pump system according to the present invention can be used as a compression heat pump system that can suppress the occurrence of insufficient heat by generating sufficient heat, but can suppress the decrease in COP accompanying the decrease in the heat source temperature of the evaporator. It is.

Schematic block diagram of the compression heat pump system of the first embodiment Schematic configuration diagram of the compression heat pump system of the second embodiment Schematic configuration diagram of a compression heat pump system of a third embodiment

Explanation of symbols

1: Refrigerant circuit 2: Compressor 3: Condenser 4: Expansion valve 5: Evaporator 10: Motor 11: Gas turbine engine 12: Reciprocating engine 13: Combustor 13a: Thermoelectric generator 20: Waste heat recovery unit 21: Heat exchanger for hot water heating (hot water heating section)
22: Regenerative heat exchanger (air preheater)
C: Condensate E, E ′: Combustion exhaust gas G: Fuel X: Refrigerant

Claims (6)

A refrigerant circuit in which a refrigerant composed of carbon dioxide circulates in order of a compressor that compresses the refrigerant, a condenser that dissipates heat from the refrigerant, an expansion valve that expands the refrigerant, and an evaporator that absorbs heat from the refrigerant. A compression heat pump system comprising:
A prime mover that burns fuel and outputs the driving force of the compressor;
An exhaust heat recovery unit that recovers heat from the combustion exhaust gas discharged from the prime mover,
A compression heat pump system configured to supply combustion exhaust gas discharged from the exhaust heat recovery unit as a heat source of the evaporator.   The compression heat pump system according to claim 1, wherein the prime mover is configured to perform lean burn of fuel in an excess air state. As the exhaust heat recovery unit, a hot water heating unit for heating hot water by heat exchange with the combustion exhaust gas,
The compression heat pump system according to claim 1 or 2, wherein the condenser is configured to heat hot water supplied to the hot water heater by heat exchange with the refrigerant.   The compression heat pump system according to any one of claims 1 to 3, further comprising an air preheating unit that preheats combustion air supplied to the prime mover by heat exchange with the combustion exhaust gas as the exhaust heat recovery unit. . The prime mover comprises an internal combustion engine;
The compression heat pump system according to any one of claims 1 to 4, wherein the compressor is driven by a shaft output or a power generation output of the internal combustion engine. The prime mover comprises a combustor that heats a thermoelectric generator that performs thermoelectric generation using the Seebeck effect,
The compression heat pump system according to any one of claims 1 to 4, wherein the compressor is driven by a power generation output of the thermoelectric generator.

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