JP2004144378A - Heat pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat pump improving COP by improving the heat exchanging efficiency of a refrigerant and the heated fluid. <P>SOLUTION: This heat pump 20 is configurated by successively circularly connecting a decompression valve 21, an evaporator 22, a compressor 23 and a heat exchanger 24. The evaporator 22 stores the liquid refrigerant prepared by mixing a large amount of lubricant in liquid phase chlorofluorocarbon in an approximately full state. The compressor 23 sucks not only the evaporated chlorofluorocarbon (gas refrigerant) but also a large amount of liquid refrigerant. Whereby the dryness of the entire refrigerant is reduced in accompany with the compression. The countercurrent exchanger 24 transfers the sensible heat of the liquid refrigerant discharged from the compressor 23 to the heated fluid such as the water for hot-water supply. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compression heat pump in which a refrigerant is evaporated and then compressed to draw heat, and the heat heats a fluid to be heated such as hot water.
[0002]
[Prior art]
Generally, a compression heat pump is configured by sequentially connecting an expansion valve, an evaporator, a compressor, and a condenser in a ring shape (for example, see Patent Document 1). Freon or the like is used as the refrigerant. After the refrigerant is expanded and decompressed by the expansion valve, it evaporates in the evaporator to become gaseous. This gaseous refrigerant is sucked into the compressor and compressed. At this time, the refrigerant is almost completely dry, and is vaporized in the process of compression even if some liquid components are mixed. The gaseous refrigerant discharged from the compressor is condensed in the condenser, and the condensed heat heats the fluid to be heated such as hot-water supply water.
[0003]
[Patent Document 1]
JP-A-2002-162123 (page 2, FIG. 1)
[0004]
[Problems to be solved by the invention]
In the above-described conventional structure, the gaseous refrigerant may have an excessively high temperature inside the compressor to cause decomposition or chemical change. In order to prevent this, it is necessary to suppress the degree of compression. For example, when applied to a water heater, hot water could not be obtained. In addition, while the condensation temperature of the refrigerant in the condenser is constant, the temperature of the fluid to be heated changes as it flows along the condenser. A temperature difference was formed, entropy was increased and efficiency was reduced. Further, in the expansion valve, friction occurs between the vaporized refrigerant and the inner peripheral surface of the orifice (throttle passage) of the expansion valve, so that the entropy is increased and the efficiency is reduced. As a result, it was not easy to increase the COP (coefficient of performance).
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is a heat pump that pumps up heat using a refrigerant and gives it to the fluid to be heated, in which a decompression unit, an evaporation unit, a compression unit, and a heat exchange unit are sequentially connected in a ring shape, In the evaporating means, a liquid refrigerant after decompression by the decompression means is stored, and evaporation of the liquid refrigerant occurs.The compression means not only sucks and compresses the evaporated gaseous refrigerant, but also compresses the gaseous refrigerant. The liquid refrigerant is operated so as to also suck the liquid refrigerant, and the suction amount of the liquid refrigerant is large enough to reduce the dryness of the entire refrigerant due to the compression, whereby the entire refrigerant becomes substantially liquid and is discharged from the compression means, In the heat exchange means, the liquid refrigerant and the fluid to be heated flow in opposite directions, and the sensible heat of the liquid refrigerant is transferred to the fluid to be heated. According to this characteristic configuration, it is possible to condense the gaseous refrigerant in the compression means, transfer the enthalpy to the liquid refrigerant, prevent the gaseous refrigerant from being excessively heated, and heat the liquid refrigerant. it can. Then, the entire refrigerant can be almost liquidized and discharged from the compression means. The sensible heat of the liquid refrigerant is transferred to the fluid to be heated in the counterflow type heat exchange means, thereby suppressing an increase in entropy, and Efficiency can be increased. Furthermore, in the decompression means, the refrigerant can be kept in a substantially liquid state by reducing the vaporization rate of the refrigerant, thereby suppressing an increase in entropy and increasing the efficiency. As a result, the COP can be increased.
[0006]
The refrigerant includes a main refrigerant that can be evaporated and condensed such as chlorofluorocarbon, and a non-volatile liquid such as a lubricating oil for a compression unit, and the content ratio of the non-volatile liquid determines the dryness of the compression unit. It is desirable that it is large enough to be reduced by the ionic liquid alone. Thereby, the amount of the main refrigerant such as chlorofluorocarbon can be reduced, the influence on the environment can be reduced, and the cost can be reduced.
In the heat exchange means, it is desirable that the specific heat flow rate of the liquid refrigerant (a mixed liquid of the liquid phase main refrigerant and the non-volatile liquid) is equal to the specific heat flow rate of the fluid to be heated. Thereby, the heat exchange efficiency can be further increased.
[0007]
It is desirable that a non-condensable gas such as air is mixed in the refrigerant. Thereby, the compression of the liquid refrigerant in the compression means can be prevented, and the compression means can be protected. The amount of the non-condensable gas mixed is desirably such that it becomes substantially the same volume as the liquid refrigerant in the final stage of the compression step. As a result, the compression means can be reliably protected, and a decrease in efficiency can be prevented.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a hot water supply heat pump system S1 to which the present invention is applied. The system S1 includes a hot water storage tank 10 and a heat pump 20.
[0009]
A water supply channel (city water channel) 11 is connected to a lower end portion of the hot water storage tank 10. City water is supplied from the water supply channel 11 into the hot water storage tank 10 as hot water supply water and stored. The water on the lower side of the hot water storage tank 10 is at room temperature, and the water on the upper side is at a high temperature by a heating operation of the heat pump 20 described later. The high-temperature water is supplied to hot water supply equipment (hot water utilization equipment) such as a bathtub or a kitchen via a hot water supply path 12 extending from an upper end of the hot water storage tank 10.
[0010]
Next, the heat pump 20 will be described.
The heat pump 20 has a refrigerant circulation system in which a pressure reducing valve 21 (pressure reducing means), an evaporator 22 (evaporating means), a compressor 23 (compressing means), and a heat exchanger 24 (heat exchanging means) are sequentially connected in a ring shape. Have a road. The refrigerant of the heat pump 20 is configured by mixing a large amount of lubricating oil (nonvolatile liquid) for the compressor 23 with Freon (a main refrigerant that can be evaporated and condensed).
[0011]
Although not shown in detail, the pressure reducing valve 21 is configured to reduce the pressure of the refrigerant through an orifice-shaped throttle passage. Friction occurs between the refrigerant and the inner peripheral surface of the throttle passage.
[0012]
The evaporator 22 has a tank shape. The lower port of the evaporator 22 is connected to the secondary port of the pressure reducing valve 21, and the upper port is connected to the suction port of the compressor 23. Inside the evaporator 22, a liquid refrigerant composed of a mixed liquid of liquid fluorocarbon and lubricating oil is stored almost completely. Further, the evaporator 22 is thermally connected to a heat source 30 for increasing the vapor pressure of the liquid phase chlorofluorocarbon. That is, the radiator tube 31 is accommodated in the evaporator 22, and the heat medium is circulated between the radiator tube 31 and the heat source 30. In the figure, reference numeral 32 denotes a pump for circulating the heat medium. As the heat source 30, a fuel cell or a solar heat collector can be used.
[0013]
The compressor 23 sucks the refrigerant from the evaporator 22, compresses and pressurizes the refrigerant, and discharges the refrigerant to the heat exchanger 24.
[0014]
The heat exchanger 24 has a pair of heat transfer paths 24a and 24b. The upstream end of one heat transfer path 24 a is connected to the discharge port of the compressor 23, and the downstream end is connected to the primary port of the pressure reducing valve 21. Thereby, the refrigerant discharged from the compressor 23 is sent to the pressure reducing valve 21 after passing through the heat transfer path 24a. The upstream end of the other heat transfer path 24b is connected to the lower part of the hot water storage tank 10, and the downstream end is connected to the upper part of the hot water storage tank 10. In the drawing, reference numeral 13 denotes a water supply pump, and the water supply pump 13 sends hot water for water supply on the lower side of the hot water storage tank 10 to the upper side of the hot water storage tank 10 after passing through the heat transfer path 24b. The refrigerant in the heat transfer path 24a and the hot-water supply water in the heat transfer path 24b flow in opposite directions (opposing directions). Thus, a counter-flow heat exchanger is configured.
[0015]
Further, the system S1 is provided with a controller 25 (control means) for controlling the pressure reducing valve 21, the compressor 23, the pumps 13, 32, and the like.
[0016]
The operation of the hot water supply heat pump system S1 configured as described above will be described. The liquid refrigerant in the evaporator 22 (mixture of liquid phase Freon and lubricating oil) receives heat from the heat source 30 to increase the vapor pressure. Thereby, the evaporation of the liquid phase CFC is promoted. On the other hand, the lubricating oil maintains a liquid state without evaporating. As a result, most of the liquid refrigerant in the evaporator 22 is occupied by the lubricating oil. The controller 25 controls the liquid refrigerant in the evaporator 22 to be almost full by adjusting the opening of the pressure reducing valve 21 or adjusting the rotation speed of the compressor 23. Thus, the compressor 23 not only sucks the gaseous refrigerant (gas-phase fluorocarbon) but also sucks a large amount of the liquid refrigerant which is almost only lubricating oil.
[0017]
The compressor 23 compresses and pressurizes the gas-liquid mixed refrigerant. At this time, compression heat is generated from the gaseous refrigerant. This heat of compression can be sufficiently absorbed by a large amount of liquid refrigerant. Thereby, the gaseous refrigerant can be prevented from being excessively heated, and decomposition and chemical change can be prevented from occurring. Further, the gaseous refrigerant can be condensed during compression, and the dryness of the entire refrigerant can be reduced. Further, the liquid refrigerant can be heated by the heat of condensation of the gaseous refrigerant. In this way, the enthalpy of the gaseous refrigerant can be transferred to the liquid refrigerant.
[0018]
Then, the refrigerant, which is almost entirely in a high-temperature liquid state, is discharged from the compressor 23 and guided to the heat transfer path 24 a of the heat exchanger 24. In addition, the hot water supply water at the lower side of the hot water storage tank 10 is guided to the heat transfer path 24b by the water supply pump 13. Thus, the sensible heat of the liquid refrigerant is transferred to the hot water while the liquid refrigerant and the hot water supply flow in opposite directions. (The heat pumped by the heat pump 20 is passed to the hot water supply water.) Therefore, the liquid refrigerant is cooled as it flows through the heat transfer path 24a, and the hot water supply flows in the heat transfer path 24b in the opposite direction to the liquid refrigerant. Heated as it flows. As a result, the temperature difference between the liquid refrigerant and the hot-water supply water can be made substantially constant over the entire length of the heat transfer paths 24a and 24b. As a result, an increase in entropy can be suppressed, and the heat exchange efficiency can be improved.
[0019]
Further, by controlling the compressor 23 and the water pump 13 by the controller 25, the specific heat flow rate of the liquid refrigerant in the heat transfer path 24a is adjusted to be substantially equal to the specific heat flow rate of the hot water supply water in the heat transfer path 24b. Thereby, the heat exchange efficiency can be further improved. Thus, the hot-water supply water can be heated to a desired temperature, sent to the upper portion of the hot-water storage tank 10, and supplied to the hot-water supply.
When the refrigerant discharged from the compressor 23 contains gaseous fluorocarbon, it is condensed in the heat transfer path 24a, and the refrigerant becomes completely liquid.
[0020]
Thereafter, the liquid refrigerant is guided to the pressure reducing valve 21 and decompressed. Since this refrigerant contains a large amount of non-volatile lubricating oil, the vaporization rate accompanying the decompression of the entire refrigerant is much smaller than that in the case where only refrigerant is used. Thereby, even if friction occurs between the refrigerant and the inner peripheral surface of the throttle passage of the pressure reducing valve 21, the amount of increase in entropy can be extremely reduced.
As a result, the COP of the heat pump 20 can be greatly improved. In the present system S1, the efficiency can be increased in principle to the efficiency of the reversible process.
[0021]
According to the heat pump 20, by mixing a large amount of lubricating oil into Freon as a refrigerant, the amount of Freon itself can be reduced, and the effect on the environment can be minimized. In addition, the compressor 23 can be lubricated with the lubricating oil, and the leakage of CFCs from the compressor 23 can be prevented, and the effect on the environment can be prevented more reliably.
[0022]
The present invention is not limited to the above embodiment, but can adopt various modes.
For example, a non-condensable gas such as air may be further mixed into a mixed refrigerant of a main refrigerant such as Freon and a non-volatile liquid such as lubricating oil. When the non-condensable gas is sucked into the compressor 23 from the evaporator 22 together with the refrigerant, the compressor 23 can be prevented from trying to compress the liquid refrigerant, and the compressor 23 can be prevented from being damaged. . It is desirable that the mixed amount of the non-condensable gas be approximately the same as the volume of the liquid refrigerant in the final stage of the compression process by the compressor 23. This makes it possible to reliably prevent the compression means from being damaged and to prevent a decrease in efficiency.
Water may be used as the refrigerant, and not only water vapor (gas refrigerant) but also liquid water (liquid refrigerant) may be sucked into the compressor 23 from the evaporator 22.
The present invention can be applied not only to hot water supply but also to a heating system. In this case, the heat medium circulating between the heat pump and the heater becomes the fluid to be heated.
[0023]
【The invention's effect】
As described above, according to the present invention, the gaseous refrigerant can be condensed in the compression means, and its enthalpy can be transferred to the liquid refrigerant. Can be warmed. Then, the entire refrigerant can be almost liquidized and discharged from the compression means. The sensible heat of the liquid refrigerant is transferred to the fluid to be heated in the counterflow type heat exchange means, thereby suppressing an increase in entropy, and Efficiency can be increased. Further, in the decompression means, the refrigerant can be kept in a substantially liquid state by reducing the vaporization ratio of the refrigerant, and the increase in entropy can be suppressed and the efficiency can be increased. As a result, the COP can be increased.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a hot water supply heat pump system according to an embodiment of the present invention.
[Explanation of symbols]
S1 Hot water supply heat pump system 10 Hot water storage tank 20 Heat pump 21 Pressure reducing valve (pressure reducing means)
22 Evaporator (evaporation means)
23 Compressor (compression means)
24 heat exchanger (heat exchange means)
25 Controller (control means for decompression means and compression means)

Claims (3)

In a heat pump that pumps heat using a refrigerant and gives it to the fluid to be heated,
The decompression means, the evaporation means, the compression means, and the heat exchange means are sequentially connected in a ring,
In the evaporating means, a liquid refrigerant after decompression by the decompression means is stored, and evaporation of the liquid refrigerant occurs,
The compression means is operated not only to suck and compress the evaporated gaseous refrigerant, but also to suck the liquid refrigerant, and furthermore, the suction amount of the liquid refrigerant reduces the dryness of the entire refrigerant with the compression. As much as possible, whereby the entire refrigerant becomes substantially liquid and is discharged from the compression means,
In the heat pump, the liquid refrigerant and the fluid to be heated flow in opposite directions, and the sensible heat of the liquid refrigerant is transferred to the fluid to be heated. The refrigerant contains a main refrigerant that can be evaporated and condensed and a non-volatile liquid, and the content ratio of the non-volatile liquid is large enough to reduce the dryness of the compression means by the non-volatile liquid alone. The heat pump according to claim 1, wherein: The heat pump according to claim 1, wherein an uncondensable gas is mixed in the refrigerant.

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