JP2004116930A - Gas heat pump type air conditioner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power of a gas engine for driving a compressor by driving a refrigerant pump for circulating a refrigerant. <P>SOLUTION: This gas heat pump type air conditioner 10 is so structured that a refrigeration cycle is composed by sequentially connecting the compressor 16, an outdoor heat exchanger 19, an outdoor expansion valve 24, and indoor heat exchangers 21A, 21B and 21C; and the compressor is driven by the gas engine 30. In exhaust heat recovery system piping 41 starting from the exit side in a heating operation of the indoor heat exchangers, bypassing the outdoor expansion valve, the outdoor heat exchanger and the compressor, and reaching the entrance side in the heating operation of the indoor heat exchangers, an overcooling heat exchanger 42 for bringing a liquid refrigerant into an overcooled state, the refrigerant pump 43 for circulating the liquid refrigerant, and an exhaust heat recovery heat exchanger 3 for recovering the exhaust heat of the gas engine to evaporate the liquid refrigerant by imparting the heat to it are sequentially installed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a gas heat pump type air conditioner using a pump that conveys a refrigerant in a liquid state.
[0002]
[Prior art]
In a refrigeration apparatus, when a refrigeration cycle is formed using a refrigerant such as Freon, a compressor 100 is generally used for circulation of the refrigerant, as shown in FIGS. 5 and 6. In this refrigeration cycle, the refrigerant is depressurized by a decompression device 102, heat is obtained from low-temperature air in an evaporator 103, adiabatically compressed by a compressor 100 to a high temperature and high pressure, and then condensed by a condenser 101. Heat the room. The refrigerant that has left the condenser 101 is temporarily stored in the liquid receiver 104.
[0003]
In this case, there is usually a temperature difference between the fluid (air) on the side where heat is drawn by heat exchange with the refrigerant and the fluid (air) on the side that discharges heat. The compressor serves to increase the temperature of the refrigerant responsible for heat transfer by adiabatically compressing the gas refrigerant, and at the same time, discharges heat from the low-temperature heat exchanger (evaporator) that draws heat from the high-temperature heat exchanger. (Condenser) Also serves as a drive pump for transporting the refrigerant to the (condenser).
[0004]
However, when another fluid (for example, engine cooling water) having a temperature equal to or higher than the temperature of the fluid to be heated (refrigerant) is present, if the same cycle as described above is to be established, the above-described compression is performed. The machine no longer performs its original compression function, but only functions as a fluid transport pump.
[0005]
In such a case, a cycle can be established even by using a pump instead of a compressor as a means for transporting the fluid (Patent Document 1). 7 and 8 show a refrigerating apparatus using a pump 105 instead of the compressor 100, and a pressure (P) -enthalpy (h) diagram of the refrigerating cycle, respectively.
[0006]
Typically, a pump is an accessory that imparts kinetic energy to the fluid. What is generally used with water or the like is a so-called volute pump, which discharges a fluid by rotating an impeller. When sending out water, a stable flow rate can be obtained unless a suction pipe having a resistance (such as a valve) is provided. However, when the liquid level is low or the water temperature is high, the liquid in the impeller evaporates, and a phenomenon called cavitation, which generates vibration and sound, may occur. This phenomenon occurs more frequently in the refrigerant than in the water.
[0007]
[Patent Document 1]
JP-A-3-105174
[Problems to be solved by the invention]
Cavitation generally occurs when the pressure of the fluid drawn into the pump falls below the saturated vapor pressure at that temperature. As shown in FIG. 9 (A), normally, in the case of water, the system is an open system in which an air pressure of 101.3 kPa is applied to a suction liquid level of a pump. To this atmospheric pressure, a height difference from the suction liquid level to the pump suction port is added as a position head (minus in the case of suction), the friction loss of the pipe from the suction liquid level to the pump suction port is subtracted, and the pump suction port is reduced. Of the fluid (net pushing pressure) is calculated. In the case of water, the saturated vapor pressure at 100 ° C. is 101.3 kPa, but it is 2.34 kPa at 20 ° C. Therefore, there is a margin of 99 kPa before the water generates cavitation. In other words, since water has a boiling point of 100 ° C., it is equivalent to a supercooled liquid of 80 ° C. at normal temperature of 20 ° C., and this degree of supercooling makes it difficult to evaporate water.
[0009]
However, refrigerants having a boiling point lower than room temperature (for example, 20 ° C.) such as chlorofluorocarbons are vaporized at room temperature. Therefore, in order to circulate the refrigerant in a liquid state, a closed system (pipe is cut off from the atmosphere) System). In this system, as shown in FIG. 9 (B), the pressure applied to the suction liquid level of the pump is the saturated vapor pressure of the refrigerant at that temperature, and this saturated vapor pressure is applied to the pressure from the suction liquid level to the pump suction port. The height difference is added as a position head, and the friction loss of the pipe from the suction liquid level to the pump suction port is subtracted to calculate the net pushing pressure. However, since the difference between the net pushing pressure and the saturated vapor pressure of the sucked liquid refrigerant is very small, cavitation is very likely to occur, and the pump may not be driven stably.
[0010]
SUMMARY OF THE INVENTION An object of the present invention is to provide a gas heat pump type air conditioner capable of stably driving a refrigerant pump for circulating a refrigerant. Another object of the present invention is to provide a gas heat pump type air conditioner that can reduce the power of a gas engine that drives a compressor by driving a refrigerant pump that circulates refrigerant.
[0011]
[Means for Solving the Problems]
The invention according to claim 1 is a gas heat pump type air conditioner in which a compressor, a condenser, a decompression device, and an evaporator are sequentially connected to form a refrigeration cycle, and the compressor is driven by a gas engine. A subcooler that makes the liquid refrigerant in a supercooled state, and circulates the liquid refrigerant to a pipe line that bypasses the decompression device, the evaporator, and the compressor from the outlet side of the condenser to the inlet side of the condenser. And a heat pump for recovering the heat exhausted from the gas engine, applying the liquid heat to the liquid refrigerant, and evaporating the liquid heat. The heat exchanger is arranged in order from the outlet side to the inlet side of the condenser. According to a second aspect of the present invention, in the first aspect of the invention, the subcooler is a plate-fin heat exchanger, and is configured to supercool the liquid refrigerant by outside air. Also characterized by According to a third aspect of the present invention, in the first aspect of the present invention, the subcooler has a double-pipe structure having an inner chamber and an outer chamber, and a part of the liquid refrigerant is other than the other. The refrigerant flows into one of the inner chamber and the outer chamber via a pressure reducing device, and is configured to supercool the liquid refrigerant flowing into the other of the inner chamber or the outer chamber by the latent heat of evaporation. .
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0013]
FIG. 1 is a circuit diagram showing an embodiment of a gas heat pump type air conditioner according to the present invention.
[0014]
As shown in FIG. 1, a gas heat pump type air conditioner 10 as a refrigerating apparatus includes an outdoor unit 11 and a plurality (for example, three) of indoor units 12A, 12B, and 12C. The refrigerant pipe 14 and the indoor refrigerant pipes 15A, 15B, 15C of the indoor units 12A, 12B, 12C are connected to form a refrigeration cycle.
[0015]
The outdoor unit 11 is installed outdoors, and a compressor 16 is disposed in the outdoor refrigerant pipe 14. An accumulator 17 is provided on the suction side of the compressor 16 and a four-way valve 18 is provided on the discharge side thereof via an oil separator 26. The outdoor heat exchanger 19, the outdoor expansion valve 24 as a pressure reducing device, and the liquid receiver 25 are sequentially arranged on the four-way valve 18 side. An outdoor fan 20 that blows air toward the outdoor heat exchanger 19 is disposed adjacent to the outdoor heat exchanger 19. The compressor 16 is connected to a gas engine 30 via a timing belt 27, and is driven by the gas engine 30.
[0016]
On the other hand, the indoor units 12A, 12B, and 12C are installed indoors, respectively, and the indoor heat exchangers 21A, 21B, and 21C are disposed in the indoor refrigerant pipes 15A, 15B, and 15C, respectively, and the indoor refrigerant pipes 15A, 15B, and In each of 15C, indoor expansion valves 22A, 22B, 22C as pressure reducing devices are arranged near the indoor heat exchangers 21A, 21B, 21C. Indoor fans 23A, 23B, and 23C that blow air to the indoor heat exchangers 21A, 21B, and 21C are arranged adjacent to the indoor heat exchangers 21A, 21B, and 21C.
[0017]
By switching the four-way valve 18, the gas heat pump air conditioner 10 is set to the cooling operation or the heating operation. That is, when the four-way valve 18 is switched to the cooling side, the refrigerant flows as indicated by the dashed arrow α, the outdoor heat exchanger 19 functions as a condenser, and the indoor heat exchangers 21A, 21B, and 21C function as evaporators, thereby performing a cooling operation. It becomes a state and each indoor heat exchanger 21A, 21B, 21C cools a room. When the four-way valve 18 is switched to the heating side, the refrigerant flows as indicated by the solid arrow β, and the indoor heat exchangers 21A, 21B, and 21C function as condensers, and the outdoor heat exchanger 19 functions as an evaporator to perform heating operation. It becomes a state and each indoor heat exchanger 21A, 21B, 21C heats a room.
[0018]
During the cooling operation, the respective opening degrees of the indoor expansion valves 22A, 22B, and 22C are adjusted according to the air conditioning load, and the outdoor expansion valve 24 is fully opened. During the heating operation, the respective valve openings of the outdoor expansion valve 24 and the indoor expansion valves 22A, 22B, 22C are adjusted according to the air conditioning load.
[0019]
On the other hand, the gas engine 30 is cooled by engine cooling water flowing through the engine cooling system 31. The engine cooling system 31 includes a first cooling system pipe 35 in which a gas engine 30, a cooling water three-way valve 32, an exhaust heat recovery heat exchanger 33, and a cooling water pump 34 are provided, and a radiator 37 is provided. One end of the two cooling system piping 36 is connected to the cooling water three-way valve 32, and the other end is connected to the suction side of the cooling water pump 34 in the first cooling system piping 35.
[0020]
During the cooling operation of the gas heat pump type air conditioner 10, the cooling water three-way valve 32 is opened to the radiator 37 side, and the operation of the cooling water pump 34 guides the engine cooling water to the radiator 37 to radiate heat. Is cooled. During the heating operation of the gas heat pump type air conditioner 10, the cooling water three-way valve 32 is opened to the exhaust heat recovery heat exchanger 33 side, and the operation of the cooling water pump 34 allows the engine cooling water to be removed from the exhaust heat recovery heat exchanger 33. And the heat is radiated by heat exchange with the liquid refrigerant as described later, and the gas engine 30 is cooled.
[0021]
Further, the outdoor unit 11 of the gas heat pump type air conditioner 10 is connected to the indoor heat exchangers 21A, 21B, 21C from the outlet side liquid receiver 25 during the heating operation of the indoor heat exchangers 21A, 21B, 21C. An exhaust heat recovery system 40 is provided in the outdoor refrigerant pipe 14 reaching the inlet side during the heating operation. The exhaust heat recovery system 40 is provided to bypass the outdoor expansion valve 24, the outdoor heat exchanger 19, and the compressor 16.
[0022]
That is, in the exhaust heat recovery system 40, one end of the exhaust heat recovery system pipe 41 is connected to the liquid receiver 25, and the other end is between the four-way valve 18 and the indoor heat exchangers 21A, 21B, and 21C in the outdoor refrigerant pipe 14. Connected to. A supercooling heat exchanger 42 serving as a subcooler, a refrigerant pump 43, a flow control valve 44, and the exhaust heat recovery heat exchanger 33 of the engine cooling system 31 are connected to the exhaust heat recovery system pipe 41 by a receiver 25. Are sequentially arranged from the side.
[0023]
The refrigerant pump 43 is a fixed-capacity type pump, and transfers the liquid refrigerant stored in the liquid receiver 25 between the exhaust heat recovery system pipe 41 and the outdoor refrigerant pipe 14 including the indoor heat exchangers 21A, 21B, and 21C. To circulate. Further, the exhaust heat recovery heat exchanger 33 exchanges heat between the high-temperature (about 70 to 85 ° C.) engine cooling water and the liquid refrigerant flowing in the exhaust heat recovery system piping 41 to evaporate the liquid refrigerant to overheat. Gas refrigerant. This superheated gas refrigerant is combined with the high-temperature and high-pressure gas refrigerant flowing from the compressor 16 to the indoor heat exchangers 21A, 21B, and 21C during the heating operation.
[0024]
Further, the flow control valve 44 is closed during the cooling operation of the gas heat pump air conditioner 10 and adjusts the flow rate of the liquid refrigerant flowing from the refrigerant pump 43 to the exhaust heat recovery heat exchanger 33 during the heating operation. Further, one end of a bypass pipe 46 having a bypass valve 45 is connected to the exhaust heat recovery system pipe 41 between the refrigerant pump 43 and the flow control valve 44, and the other end of the bypass pipe 46 is connected to the receiver 25. Connected to. This bypass valve 45 also adjusts the flow rate of the liquid refrigerant flowing from the refrigerant pump 43 to the exhaust heat recovery heat exchanger 33.
[0025]
The supercooling heat exchanger 42 is a plate fin type heat exchanger as shown in FIG. 2, and a path pipe 47 through which a liquid refrigerant flows is joined by a header 48 to reduce pressure loss. The temperature of the liquid refrigerant flowing through the path pipe 47 of the subcooling heat exchanger 42 is about 40 to 45 ° C., and the temperature of the air (outside air temperature) blown by the blower fan 49 to the subcooling heat exchanger 42 is about 8 Since the temperature is on the order of degrees Celsius, the liquid refrigerant is cooled by the supercooling heat exchanger 42 to a supercooled state. The degree of supercooling of the liquid refrigerant brought into a supercooled state by the supercooling heat exchanger 42 is about 5 ° C.
[0026]
The reason that the refrigerant sucked into the refrigerant pump 43 is supercooled by the subcooling heat exchanger 42 is to prevent cavitation in the refrigerant pump 43 and to drive the refrigerant pump 43 stably. That is, the condition for stably driving the refrigerant pump 43 is that the net suction head (NPSH) of the exhaust heat recovery system 40 including the refrigerant pump 43 is the minimum net suction head that does not generate cavitation in the exhaust heat recovery system 40. (NPSH) is about 30% higher.
[0027]
Here, the net suction head (NPSH) is defined by the following equation (1).
[0028]
NPSH = pressure of gas phase in contact with suction liquid level + pressure by position head−saturated vapor pressure of liquid−friction loss of pipe… Equation (1)
By setting the liquid refrigerant sucked into the refrigerant pump 43 to a supercooled state by the subcooling heat exchanger 42, the “saturated vapor pressure of the liquid (refrigerant)” in the above equation (1) decreases. As a result, the net suction head (NPSH) increases, cavitation can be prevented from occurring in the exhaust heat recovery system 40 including the refrigerant pump 43, and the refrigerant pump 43 can be driven stably.
[0029]
The engine cooling water flows to the exhaust heat recovery heat exchanger 33, and the exhaust heat recovery heat exchanger 33 heats and evaporates the refrigerant to be a superheated gas refrigerant during the heating operation of the gas heat pump air conditioner 10. It is. During the heating operation, the refrigerant (point B in FIG. 3) discharged from the compressor 16 passes through the oil separator 26 and the four-way valve 18 and then is heated by the exhaust heat recovery heat exchanger 33 (FIG. 3). (Point C in FIG. 3) and condensed in the indoor heat exchangers 21A, 21B, 21C (point D in FIG. 3) to heat the room.
[0030]
The liquid refrigerant condensed in the indoor heat exchangers 21A, 21B, 21C reaches the liquid receiver 25 (point E in FIG. 3), and a part of the liquid refrigerant flows to the exhaust heat recovery system 40. This part of the liquid refrigerant is supercooled in the supercooling heat exchanger 42 of the exhaust heat recovery system 40 (point F in FIG. 3), and is sucked into the refrigerant pump 43 to be boosted (point G in FIG. 3). The flow rate is adjusted by the flow rate adjusting valve 44 (point H in FIG. 3), and flows into the exhaust heat recovery heat exchanger 33. In the exhaust heat recovery heat exchanger 33, the refrigerant becomes a superheated gas refrigerant as described above (point I in FIG. 3), and merges with the refrigerant flowing toward the indoor heat exchangers 21A, 21B, and 21C.
[0031]
Most of the refrigerant that has reached the liquid receiver 25 is depressurized by the outdoor expansion valve 24 (point J in FIG. 3), and the outdoor heat exchanger 19 obtains heat from low-temperature outside air and evaporates (see FIG. 3). At point K), it passes through the four-way valve 18 (point A in FIG. 3) and returns to the compressor 16 via the accumulator 17.
[0032]
According to the above-described embodiment, the following effects (1) and (2) can be obtained.
[0033]
(1) Since the liquid refrigerant sucked into the refrigerant pump 43 is supercooled by the subcooling heat exchanger 42, the saturated vapor pressure of the refrigerant in the exhaust heat recovery system 40 can be reduced. The net suction head (NPSH) can be set higher. As a result, since cavitation can be prevented from occurring in the refrigerant pump 43, the refrigerant pump 43 for circulating the refrigerant can be driven stably. As described above, since the refrigerant pump 43 can be driven stably, the capacity of the refrigerant pump 43 can be maximized, and therefore, the power of the gas engine 30 for driving the compressor 16 can be improved. Can be reduced, and the energy efficiency during the heating operation can be improved.
[0034]
(2) As described above, since the power of the gas engine 30 is reduced, the amount of gas consumed by the gas engine 30 can be reduced. As a result, the amount of exhaust gas such as NOx discharged from the gas engine 30 into the atmosphere is reduced, and the degree of environmental pollution is reduced.
[0035]
As described above, the present invention has been described based on the above embodiment, but the present invention is not limited to this.
[0036]
For example, the subcooler may be a double tube heat exchanger 50 having a double tube structure as shown in FIG. This double tube heat exchanger 50 has an inner chamber 51 and an outer chamber 52, and most of the liquid refrigerant from the liquid receiver 25 flows through the inner chamber 51. A part of the liquid refrigerant from the liquid receiver 25 is decompressed by the capillary tube 53 as a decompression device to become a gas-liquid two phase, and flows in the outer chamber 52. The refrigerant in the outer chamber 52 removes latent heat for evaporation from the liquid refrigerant in the inner chamber 51 and cools the refrigerant in the inner chamber 51 to a supercooled state. According to the double tube heat exchanger 50 and the capillary tube 53, other fluid such as air (outside air) is not required for cooling the refrigerant.
[0037]
Further, by supercooling the refrigerant sucked into the refrigerant pump 43 by the subcooling heat exchanger 42 or the double tube heat exchanger 50, the refrigerant pump 43 can be operated stably. The present invention can be applied to a type air conditioner and heat transfer for utilizing surplus energy.
[0038]
【The invention's effect】
According to the gas heat pump type air conditioner according to the first to third aspects of the present invention, the refrigerant pump for circulating the refrigerant can be driven stably. Further, according to the gas heat pump type air conditioner of the present invention, the power of the gas engine that drives the compressor can be reduced by driving the refrigerant pump that circulates the refrigerant.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing one embodiment of a gas heat pump type air conditioner according to the present invention.
FIG. 2 is a perspective view showing a subcooling heat exchanger as the subcooler in FIG.
FIG. 3 is a graph showing a pressure (P) -enthalpy (h) diagram in the refrigeration cycle of FIG. 1;
FIG. 4 is a perspective view showing another embodiment of the supercooler.
FIG. 5 is a circuit diagram showing a conventional refrigeration apparatus (air conditioner).
FIG. 6 is a graph showing a pressure (P) -enthalpy (h) diagram in the refrigeration cycle of FIG. 5;
FIG. 7 is a circuit diagram showing another conventional refrigeration apparatus (air conditioner).
FIG. 8 is a graph showing a pressure (P) -enthalpy (h) diagram in the refrigeration cycle of FIG. 7;
FIG. 9 is a diagram showing a relationship between a pump position and NPSH, where (A) shows a case of water and (B) shows a case of a refrigerant.
[Explanation of symbols]
Reference Signs List 10 gas heat pump type air conditioner 16 compressor 19 outdoor heat exchangers 21A, 21B, 21C indoor heat exchanger 24 outdoor expansion valve (decompression device)
25 Liquid receiver 30 Gas engine 33 Exhaust heat recovery heat exchanger 40 Exhaust heat recovery system 41 Exhaust heat recovery system piping 42 Subcooling heat exchanger (supercooler)
43 Refrigerant pump

Claims (3)

In a gas heat pump type air conditioner in which a compressor, a condenser, a decompression device, and an evaporator are sequentially connected to form a refrigeration cycle, and the compressor is driven by a gas engine.
A subcooler that makes the liquid refrigerant in a supercooled state, and a pipe that extends from the outlet side of the condenser to the decompression device, the evaporator, and the inlet side of the condenser bypassing the compressor. A circulating refrigerant pump and an exhaust heat recovery heat exchanger that collects the exhaust heat of the gas engine, applies the liquid heat to the liquid refrigerant, and evaporates the liquid refrigerant are sequentially arranged from the outlet side to the inlet side of the condenser. A gas heat pump type air conditioner characterized by the following. The gas heat pump type air conditioner according to claim 1, wherein the subcooler is a plate fin type heat exchanger, and is configured to supercool the liquid refrigerant by outside air. The supercooler is configured in a double pipe structure having an inner chamber and an outer chamber, and a part of the liquid refrigerant flows into one of the inner chamber or the outer chamber via another decompression device, and the latent heat of evaporation causes The gas heat pump type air conditioner according to claim 1, wherein the liquid refrigerant flowing into the other of the inner chamber and the outer chamber is supercooled.

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