JPH01193561A - Heat pump - Google Patents

Abstract

PURPOSE:To save energy by a method wherein CO2 is used as cooling medium and employing a counterflow type heat exchanger for the cooling unit in which the cooling medium and the load fluid flow in the mutually opposite directions and the cooling medium is maintained in the state of a fluid at a super critical pressure. CONSTITUTION:CO2 gas is compressed by a compressor 1 to become a fluid at a super critical pressure, and is supplied to a cooling unit 2 via a cooling medium passage 5 where the gas is cooled. The cooling medium is cooled by the load fluid supplied through a piping 10, maintaining its super critical condition. The super critical pressure fluid so cooled passes through a cooling medium passage 6, goes through a pressure reduction by a reduction mechanism 3, and enters into an evaporator 4 via a cooling medium passage 7. Since the cooling medium is not in the super critical condition by now, the cooling medium is super heated and evaporated by the heating medium supplied through a piping 9 to be returned to the compressor 1 to complete the cycle. By employing a counterflow type heat exchanger for the cooling unit 2, the temperature change of the cooling medium in the cooling unit 2 can be effectively utilized, saving energy.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat pump that uses carbon dioxide as a refrigerant. In addition, here, what is a heat pump?
It refers not only to heat pumps in the narrow sense of producing hot fluids, but also to heat pumps in a broader sense, including refrigerators that produce cold fluids.

[Prior art]

In recent years, chlorine (
Because C1) destroys the ozone layer in the stratosphere of the atmosphere, consideration is being given to internationally regulating the use of CFCs.

In other words, the ozone layer absorbs 290 to 320 nm of light that is harmful to living things out of the light irradiated into the atmosphere, and if this ozone is decomposed and destroyed, the harmful light will reach the earth's surface. This is because it will be put away.

By the way, if all halogenated chlorofluoroalkanes were to be regulated, the main refrigerants currently used in heat pumps, Freon-113, Freon-11,
Freon-114, Freon-12, Freon-22, etc. will all be regulated.

Therefore, there is an urgent need to develop alternative refrigerants other than the currently used fluorocarbon-based refrigerants.

[Problems with conventional technology]

At present, carbon dioxide is considered to be the most promising refrigerant other than fluorocarbon-based refrigerants due to its nonflammability, safety, harmlessness, and noncorrosion.

However, this carbon dioxide has a very low critical temperature;
When operating under normal air conditioning conditions and using a heat pump cycle, there was a problem in that the coefficient of performance was extremely poor and it was 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 fluorocarbon-based refrigerant and that can save energy compared to conventional heat pumps.

[Means for solving problems]

In order to solve the above problems, the present invention uses a heat pump,
In a heat pump that is equipped with a compressor, a cooler, a pressure reduction mechanism, and an evaporator, and which connects these devices with a refrigerant path to form a refrigerant circulation flow path, carbon dioxide is used as the refrigerant, and the refrigerant in the cooler is The fluid was in a supercritical pressure state, and the cooler was configured as a counterflow type heat exchanger in which the flow of the refrigerant and the flow of the load fluid were opposed to each other.

The present invention also provides a heat pump that includes a compressor, a cooler, a pressure reduction mechanism, and an evaporator, and connects these devices with a refrigerant path to form a refrigerant circulation flow path.
Carbon dioxide is used as a refrigerant, the refrigerant in the cooler is in a supercritical pressure fluid state, and the cooler is equipped with a water sprinkler that sprays water onto its heat transfer surface.

[Effect]

Since the heat pump of the present invention is constructed as described above, carbon dioxide is used as the refrigerant, so there is no need to use fluorocarbons containing chlorine in the molecules thereof, and therefore the formation sphere is not destroyed.

In addition, since the refrigerant in the cooler is in a supercritical pressure fluid state,
It is possible to provide a heat pump with a high coefficient of performance compared to the conventionally used Freon-12(7).

Furthermore, if the structure of the cooler is made to be a countercurrent type, temperature changes can be effectively utilized, and the heat pump can be made energy efficient.

Furthermore, if the cooler is structured to include a water sprinkler that sprays water onto its heat transfer surface, the pressure of the refrigerant can be lowered, and the cooler can be used for normal cooling, making it even more effective.

〔Example〕

EMBODIMENT OF THE INVENTION Hereinafter, the first example of the heat pump according to the present invention will be described in detail based on the drawings.

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

As shown in the figure, this heat pump is equipped with 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, and 7.8 to form a refrigerant circulation flow path. It is composed of the following.

Furthermore, carbon dioxide is used as a refrigerant for this heat pump.

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

Note that FIG. 2 is a diagram depicting an example of a cycle with conditions that allow hot water supply and cooling to be performed simultaneously on a Mollier diagram of carbon dioxide, and the following description will be made with reference to this diagram as well.

The conditions in Figure 2 are that the evaporation temperature is 5°C,
The compressor uses reversible adiabatic compression, the cooler and evaporator use isobaric change, and the pressure reduction mechanism uses isenthalpic expansion.

Here, this cycle is indicated by dotted lines A-B4C4D.

As shown in Figs. 1 and 2, carbon dioxide gas, which is a refrigerant, is first compressed by the compressor 1 to become a supercritical pressure fluid (B in Fig. 2), and then passes through the refrigerant path 5 to the cooler. 2, where it is cooled (C in Figure 2). In a normal heat pump, this part functions as a condenser, but since the refrigerant in this embodiment is a supercritical pressure fluid, it does not condense, and can be cooled in a supercritical state by the load fluid sent through the piping 10. The cooled supercritical pressure fluid passes through the refrigerant path 6, is reduced in pressure by the pressure reducing 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, like in a normal heat pump, the refrigerant is overheated by the heat source fluid sent through the pipe 9, evaporates, and returns to the compressor 1 again, forming the cycle. be done.

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

If the cooler 2 is configured with a countercurrent heat exchanger and the temperature change of the refrigerant in the cooler 2 is effectively utilized, the temperature distribution of the refrigerant and the load fluid in the cooler 2 can be improved. Third
The result will be as shown in the figure.

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 to serve the hot water supply load.

On the other hand, when Freon-12, which is conventionally used for hot water supply, is applied to the same conditions as for carbon dioxide, the cycle is a4b4cm1-d on the Mollier diagram of Freon-12 shown in Figure 4. It becomes like this.

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

When calculating the coefficient of performance COP under these conditions from Figures 2 and 4, it is found that for carbon dioxide, C0P = 4.4, and for Freon-12, C0P = 3.7. Compared to Freon-12, the coefficient of performance is about 20% better. In this way, a heat pump that uses carbon dioxide as a refrigerant and effectively utilizes its supercritical state has a particularly large temperature difference between the inlet and outlet of the load fluid, so the heat pump uses hot water for hot water supply or air flow for drying as the load fluid. It is most effective to use it as a water heater or dryer.

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

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

FIG. 5 is a block diagram showing the structure of this second embodiment.

Note that the same parts as in the first embodiment are given the same reference numerals.

As shown in the figure, in this embodiment, carbon dioxide gas, which is a refrigerant, is compressed by a compressor 1 and a refrigerant path 5
is sent to the cooler 2. In the cooler 2, water sprayed from a water sprinkler 13 through a pump 12 and piping 11 is vaporized and cooled by air ventilated by a fan 14, and the refrigerant is cooled by the sprayed water. Note that the refrigerant may condense depending on the temperature conditions of the sprayed water.

This cooled refrigerant passes through a refrigerant path 6, is reduced in pressure by a pressure reducing mechanism 3, and enters an evaporator 4 through a refrigerant path 7.

In the evaporator 4, the refrigerant is heated and evaporated by the cooling load fluid sent through the pipe 9, and the - side cooling load fluid is cooled.
Subjected to 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 compared to the conventional air-cooled type cooler because the heat of vaporization of water is used. Since the pressure of the refrigerant can be lowered, it can be used for ordinary air conditioning, making it even more effective.

Although the present invention has been described above based on Examples, it goes without saying that the present invention is not limited to the above-mentioned Examples, and that various modifications can be made within the scope of the present invention.

〔Effect of the invention〕

As explained in detail above, the heat pump according to the present invention uses carbon dioxide as a refrigerant, so there is no need to use fluorocarbons containing chlorine in its molecules, and therefore the heat pump has the advantage of not destroying the stratosphere. It has a great effect.

Furthermore, according to the heat pump according to the present invention, by effectively utilizing the supercritical pressure state of carbon dioxide, it is possible to provide a heat pump with a higher coefficient of performance than in the case of conventionally used Freon-12. have

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

Furthermore, if the heat pump cooler according to the present invention is structured to include a water spraying device that sprays water on its heat transfer surface, the pressure of the refrigerant can be lowered, and it can be used for normal cooling. It becomes effective.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the structure of a heat pump according to the first embodiment of the present invention, and Fig. 2 shows an example of a cycle with conditions that allow hot water supply and cooling to be performed simultaneously on a Mollier diagram of carbon dioxide. Figure 3 is a diagram showing the temperature distribution of the refrigerant and load fluid in the cooler 2 configured with a countercurrent heat exchanger, Figure 4
The figure is a diagram depicting an example of a cycle on the Mollier diagram of Freon-12, and FIG. 5 is a configuration diagram showing the 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... Water sprinkler, 14... Fan. Applicant Ebara Research Institute Co., Ltd. Agent Patent Attorney Takashi Kumagai (1 other person) Figure 1 Figure 3 Figure 2

Claims (4)

[Claims] (1) Equipped with a compressor, cooler, pressure reduction mechanism and evaporator,
In a heat pump that connects these devices with a refrigerant path to form a refrigerant circulation flow path, carbon dioxide is used as the refrigerant, the refrigerant in the cooler is in a supercritical pressure fluid state, and the cooler is in a state of supercritical pressure fluid. A heat pump characterized in that it is a counterflow type heat exchanger in which the flow of the flow 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 a drying air flow. (4) Equipped with a compressor, cooler, pressure reduction mechanism and evaporator,
In a heat pump that connects these devices through a refrigerant path to form a refrigerant circulation flow path, carbon dioxide is used as the refrigerant, the refrigerant in the cooler is in a supercritical pressure fluid state, and the cooler is in a state of supercritical pressure fluid. A heat pump characterized in that it is configured to include a water sprinkler that sprays water onto a heated surface.