JP2548962B2 - heat pump - Google Patents

Description

The present invention relates to a heat pump using carbon dioxide as a refrigerant. In addition, here, the heat pump is not limited to a heat pump in a narrow sense for producing a warm fluid,
It refers to a heat pump in a broad sense that includes a refrigerator that produces a cold fluid.

[Prior art]

In recent years, chlorine (Cl) contained in CFCs (chlorofluorocarbons) used as working refrigerants for compression heat pumps has been attempting to regulate the use of CFCs internationally because they destroy the ozone layer in the stratosphere of the atmosphere. Consideration is being made.

That is, in this ozone layer, of the light that illuminates the atmosphere,
It absorbs light of 290 to 320 nm, which is harmful to living things, and if the ozone is decomposed and destroyed, the harmful light reaches the surface of the earth.

By the way, if all halogenated chlorofluoroalkanes are regulated, the major refrigerants currently used in heat pumps such as CFC-13, CFC-11, CFC-114, CFC-12, CFC-22 are All will be regulated.

Therefore, the development of alternative refrigerants other than the CFC-based refrigerants currently used is urgently needed.

[Problems of conventional technology]

At the present time, carbon dioxide is considered to be the most promising refrigerant other than the chlorofluorocarbon-based refrigerant in view of nonflammability, safety, harmlessness, noncorrosion, and the like.

However, carbon dioxide has a very low critical temperature, and when it is operated under normal air conditioning conditions to form a heat pump cycle, the coefficient of performance is extremely poor and it is not economical.

The present invention has been made in view of the above points, and an object of the present invention is to provide a heat pump that uses carbon dioxide instead of a CFC-based refrigerant and that can save energy as compared with a conventional heat pump.

[Means for solving problems]

In order to solve the above problems, the present invention provides a heat pump, comprising a compressor, a cooler, a decompression mechanism, and an evaporator, and a heat pump that forms a refrigerant circulation flow path by connecting these devices with a refrigerant path. Carbon dioxide is used as the refrigerant, the refrigerant in the cooler is in the state of supercritical pressure fluid, and the cooler is configured as a countercurrent heat exchanger in which the flow of the refrigerant and the flow of the load fluid are opposed to each other.

The present invention also includes a heat pump, a compressor, a cooler, a decompression mechanism, and an evaporator, which uses carbon dioxide as a refrigerant in a heat pump in which these devices are connected by a refrigerant path to form a refrigerant circulation flow path. The refrigerant in the cooler is in a supercritical pressure fluid state, and the cooler is provided with a water spraying device for spraying water on the heat transfer surface thereof.

[Action]

Since the present invention has constituted the heat pump as described above, since carbon dioxide is used as the refrigerant, it is not necessary to use CFC containing chlorine in its molecule, and therefore the stratosphere is not destroyed.

Moreover, since the refrigerant in the cooler is in the state of supercritical pressure fluid, it is possible to provide a heat pump having a higher coefficient of performance than that of the conventionally used Freon-12.

Further, if the structure of the cooler is a counterflow type, the temperature change can be effectively utilized and the heat pump can save energy.

Further, if the cooler is provided with a water spraying device for spraying water on its heat transfer surface, the pressure of the refrigerant can be lowered, and it can be used for ordinary cooling, which is even more effective.

〔Example〕

Hereinafter, a first embodiment of a heat pump according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a configuration diagram showing the configuration of the heat pump according to this embodiment.

As shown in the figure, this heat pump comprises a compressor 1, a cooler 2, a pressure reducing mechanism 3 and an evaporator 4, and these devices are connected by refrigerant paths 5, 6, 7 and 8 to form a refrigerant circulation flow path. Is formed. Carbon dioxide is used as the refrigerant of this heat pump.

Next, the operation cycle of the heat pump shown in FIG. 1 will be described.

Note that FIG. 2 is a diagram showing an example of a cycle on the Mollier diagram of carbon dioxide, in which hot water supply and cooling can be performed at the same time, which will be described below also with reference to this diagram.

The conditions in FIG. 2 are that the evaporation temperature is 5 ° C.
It is assumed that the compressor is reversible adiabatic compression, the cooler / evaporator is isobaric pressure change, and the decompression mechanism is isenthalpic expansion.

 Here, this cycle is indicated by a dotted line A → B → C → D.

As shown in FIGS. 1 and 2, first, carbon dioxide gas which is a refrigerant is compressed by the compressor 1 to become a supercritical pressure fluid (B in FIG. 2), and passes through the refrigerant path 5 to cool the cooler. 2 where it is cooled (C in FIG. 2). In a normal heat pump, this portion serves as a condenser, but since the refrigerant in this embodiment is a supercritical pressure fluid, it does not condense and is cooled in the supercritical state by the load fluid sent through the pipe 10. The cooled supercritical fluid passes through the refrigerant path 6, is decompressed by the decompression mechanism 3 (D in FIG. 2), and enters the evaporator 4 through the refrigerant path 7. Since the refrigerant at this time is not in a supercritical state, the refrigerant is superheated by the heat source fluid sent through the pipe 9 like a normal heat pump, evaporates, and returns to the compressor 1 again, thereby forming the cycle. To be done.

In the above example, the inlet refrigerant temperature of the cooler 2 is 80 ° C and the outlet refrigerant temperature is 40 ° C (B → C in Fig. 2).

If the cooler 2 is configured by a countercurrent heat exchanger to effectively use the temperature change of the refrigerant in the cooler 2, the temperature distribution of the refrigerant and the load fluid in the cooler 2 can be improved. As shown in FIG.

That is, as shown in the figure, the refrigerant is cooled from 80 ° C to 40 ° C, and conversely, the load fluid is heated from 30 ° C to 70 ° C and supplied to the hot water supply load.

On the other hand, the cycle when CFC-12 conventionally used for hot water supply is applied to the same condition as the case of carbon dioxide is as follows: cycle a → b → on the Mollier diagram of CFC-12 shown in FIG. It becomes like c → d.

Here, in order to heat the load fluid from 40 ° C to 70 ° C, the condensation temperature of the refrigerant becomes 75 ° C.

The coefficient of performance COP under these conditions is calculated from Figs. 2 and 4, and COP = 4.4 and CFC-12 in the case of carbon dioxide.
In the case of COP = 3.7, compared to the conventional CFC-12,
The coefficient of performance is improved by about 20%. Thus, using carbon dioxide as a refrigerant, a heat pump that effectively utilizes its supercritical state, in particular, because the temperature difference between the inlet and outlet of the load fluid is large, the load fluid as hot water for hot water supply and air flow for drying,
It is most effective when used as a water heater or dryer.

Although this embodiment can be used as it is for ordinary cooling, the pressure of the refrigerant in the cooler 2 becomes high.

Therefore, a second embodiment in which the pressure of the refrigerant can be lowered will be described next.

FIG. 5 is a configuration diagram showing the configuration of the second embodiment.

The same parts as those in the first embodiment are designated by the same reference numerals.

As shown in the figure, in this embodiment, the carbon dioxide gas that is a refrigerant is compressed by the compressor 1 and sent to the cooler 2 through the refrigerant path 5. In this cooler 2,
The water sprayed from the sprinkler device 13 through the pump 12 and the pipe 11 is naturalized and cooled by the air ventilated by the fan 14, and the sprayed water cools the refrigerant. The refrigerant may be condensed depending on the temperature condition of the spray water.

The cooled refrigerant passes through the refrigerant path 6 and passes through the pressure reducing mechanism 3
The pressure is reduced by and enters the evaporator 4 through the refrigerant path 7. In the evaporator 4, the refrigerant is heated and evaporated by the cooling load fluid sent through the pipe 9, while the cooling load fluid is cooled and supplied to the load. After this, the refrigerant returns to the compressor 1 again to form a cycle.

As described above, according to this embodiment, the temperature condition of the refrigerant in the cooler 2 can be kept low because the heat of vaporization of water is used as compared with the conventional air-cooled cooler, and as a result, Since the pressure of the refrigerant can be lowered, it can be used for ordinary cooling and is more effective.

Although the present invention has been described above based on the embodiments, it is needless to say that the present invention is not limited to the above embodiments and various modifications can be made within the scope of the present invention.

〔The invention's effect〕

As described in detail above, according to the heat pump of the present invention, since carbon dioxide is used as the refrigerant, it is not necessary to use freon containing chlorine in its molecule, and therefore it is excellent in that it does not destroy the stratosphere. Have the effect.

Further, according to the heat pump of the present invention, by effectively utilizing the supercritical pressure state of carbon dioxide, it is possible to provide an excellent effect that it is possible to provide a heat pump with a higher coefficient of performance than the case of CFC-12 conventionally used. Have.

Further, if the structure of the cooler of the heat pump according to the present invention is a countercurrent type, the temperature change can be effectively used and energy can be saved.

Further, if the structure of the cooler of the heat pump according to the present invention is provided with a water spraying device for spraying water on its heat transfer surface, the pressure of the refrigerant can be lowered, and it can be used as a normal refrigerant. It becomes effective.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration of a heat pump according to a first embodiment of the present invention, and FIG. 2 is an example of a cycle provided with conditions for hot water supply / cooling at the same time on a Mollier diagram of carbon dioxide. The drawing and FIG. 3 are diagrams showing the temperature distributions of the refrigerant and the load fluid in the cooler 2 constituted by the countercurrent heat exchanger, and FIG. 4 is the Mollier diagram of Freon-12 showing the cycle FIG. 5 is a diagram showing an example, and FIG. 5 is a configuration diagram showing a configuration of a second embodiment of the present invention. In the figure, 1 ... Compressor, 2 ... Cooler, 4 ... Evaporator, 3
...... Pressure reduction mechanism, 5,6,7,8 …… Refrigerant path, 11 …… Piping, 12
...... Pump, 13 ... Sprinkler, 14 ... Fan.

Claims (4)

(57) [Claims] 1. A heat pump comprising a compressor, a cooler, a decompression mechanism and an evaporator, wherein these devices are connected by a refrigerant path to form a refrigerant circulation flow path, wherein carbon dioxide is used as a refrigerant and the cooling is performed. A heat pump, characterized in that the refrigerant in the container is in a supercritical pressure fluid state, and the cooler is a countercurrent heat exchanger in which the flow of the refrigerant and the flow of the load fluid are opposed to each other. 2. The heat pump according to claim 1, wherein the load fluid of the cooler is hot water for hot water supply. 3. The heat pump according to claim 1, wherein the load fluid of the cooler is an air flow for drying. 4. A heat pump comprising a compressor, a cooler, a decompression mechanism and an evaporator, wherein these devices are connected by a refrigerant path to form a refrigerant circulation channel, carbon dioxide is used as the refrigerant, and the cooling is performed. A heat pump characterized in that the refrigerant in the container is in a state of supercritical pressure fluid, and the cooling device is provided with a spraying device for spraying water on its heat transfer surface.