JPH0349018B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a heat pump for producing hot fluid such as hot water.

In addition, in this specification, "a plurality of compression stages" includes not only a multistage compressor but also one in which a plurality of compressors are connected in series.

(Prior Art) In recent years, a heat pump for producing hot water, which is one type of refrigeration equipment, has a plurality of condensers with different pressures and a plurality of compressors or multiple stages, as shown in Fig. 1. Energy-saving heat pumps are attracting attention, in which each condenser is connected to its corresponding compressor, and each discharged refrigerant is introduced separately. This heat pump will be explained using the flow sheet shown in FIG.

The liquid refrigerant in the evaporator 1 is heated and evaporated by the heat source water sent through the pipe 2, and is sucked into the first stage compressor 4 through the suction pipe 3. For example, about half of the gas compressed by the compressor 4 is discharged from the discharge pipe 5 to the condenser 6, and the remaining half is sucked into the second stage compressor 8 via the branch 7.
It is compressed and discharged to the condenser 9.

The cooling of each of the condensers 6, 9 is performed by a load fluid as a fluid to be heated, which is heated by the pump 10 while flowing successively through these two condensers in series. In this system, which has a plurality of condensers 6 and 9 with different pressures, a load fluid with a large temperature difference between the inlet and outlet is normally applied. The fluid is heated at a temperature of approximately 100°C at the load fluid outlet 12 and is then used for loading.

On the other hand, the refrigerant gas is condensed in the condenser 9,
It passes through a pipe 13, is depressurized by a pressure reducing device 14, and is sent to the next stage condenser 6. At this time, flash gas is generated due to the depressurization, but this gas is
Together with the refrigerant gas discharged from the first stage compressor 4 through the discharge pipe 5, the refrigerant gas is cooled by the load fluid in the condenser 6 and is condensed and liquefied. This condensate is pipe 15
After that, the pressure is reduced by a pressure reducing device 16, and the liquid returns to the evaporator 1.

Fig. 2 is a temperature diagram for the above case. If you design the impeller etc., the difference will be 45℃.
Similarly, the outlet temperature of hot water in condenser 6 is 60
It is also 5°C higher than the average temperature, so it has a sufficient condensing function. The same thing can be said about the other condensers 9 if the refrigerant gas temperature is set to 105°C.

In this way, the condensing temperature required by each condenser is
(The exit temperature of the hot water passing through each condenser + an appropriate temperature difference), this system requires less power than a conventional system with one condenser, and the second Energy is saved by the amount corresponding to the shaded area in the upper left of the figure. In this way, this heat pump system is effective when the temperature difference between the inlet and outlet of the load fluid is large, that is, when the refrigerant temperature at the outlet of the final stage compressor is high.

(Problems to be Solved by the Invention) When a conventionally used refrigerant, for example R/2, is used to obtain a high-temperature load fluid in this heat pump system, the final stage compressor outlet pressure is For example, at R/2 and 105℃, 37Kg/
cm ² (abs) (here (abs) is absolute pressure.)
Since the pressure is high, there is a drawback that conventional equipment such as compressors cannot be used as is.

In order to eliminate this drawback, it is necessary to use a high boiling point refrigerant with a saturation pressure of 15 kg/cm ² (abs) or less at a temperature of 100° C.

However, when such a high boiling point refrigerant is used, the condenser in this heat pump system is a shell and tube type condensing type,
That is, as shown in FIG.
A refrigerant is passed through the inside of the partition plate 10, and the outside thereof, that is, the partition plate 10
When water is passed through the shell 103 partitioned by tubes 2 and condensed on the inner surface of the tube 101, the flow rate of the refrigerant gas in the condenser 6 on the low pressure side is low pressure, so Since the volume is large, it becomes faster, which has the disadvantage of increasing pressure loss, and if the tube length is shortened and the number of tubes is increased in order to reduce pressure loss, it has the disadvantage of increasing costs.

In addition, as a condenser, an extra-tube condensing type is used, that is, as shown in FIG. If the tube 101 is configured to condense on the outer surface, the flow rate of the refrigerant gas in the condenser 9 on the high pressure side will be slow because the pressure is high and the specific volume is small.
Particularly in the case of a countercurrent type condenser, there was a drawback that the heat transfer performance within the condenser deteriorated. In addition, in commonly used shell-and-tube type condensers, if you compare the cross-sectional area of the passage inside the tube with the cross-sectional area of the passage on the shell side, the shell side is usually larger, and the pressure loss on the refrigerant side is smaller. Depending on the specific volume of the refrigerant used in the heat pump, taking into account heat transfer performance and heat transfer performance, if the specific volume is small, an inside-tube type is used, or if the specific volume is large, an outside-tube type is used.

In order to eliminate the above-mentioned drawbacks, the present invention provides an energy-saving heat pump system, particularly in the energy-saving heat pump system that uses a high-boiling refrigerant as a refrigerant to obtain a high-temperature load fluid, due to the pressure loss in the condenser. The objective is to prevent the increase in heat transfer performance and to improve heat transfer performance.

(Means for Solving the Problems) The present invention provides a heat pump system using a high boiling point refrigerant having a saturation pressure of 15 Kg/cm ² (abs) or less at a temperature of 100°C as a refrigerant. Among the condensers, at least the condenser where the refrigerant condenses at the highest temperature is a shell and tube type in-tube condensing type, and the condenser at the lowest temperature is an extra-tube condensing type.

(Function) In the present invention, by using the above-mentioned high boiling point refrigerant, neither the pressure in each condenser nor the pressure in the evaporator becomes high. In addition, when using a high boiling point refrigerant, the air volume of the refrigerant gas increases at low temperatures, so an extra-tube condensing type is used for the condenser that produces at least the minimum temperature, and the air volume decreases at high temperatures, so at least the maximum temperature An in-pipe condensation type is used for the condenser, and therefore the flow of refrigerant is appropriate in each condenser, and the heat transfer performance is good without increasing pressure loss, and the heat exchange effect is improved. is carried out efficiently.

(Example) Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is a flow sheet showing an embodiment of a heat pump to which the present invention is applied, and FIG. 2 is a temperature diagram thereof.

As the refrigerant used in the heat pump system shown in FIG. 1, in the present invention, a high boiling point refrigerant having a saturation pressure of 15 kg/cm ² (abs) or less at a temperature of 100° C. is used. As an example, the refrigerant used will be described as R11.

When using R11 above, as a result of theoretical calculation, the pressure in condenser 9 is 9.4Kg/cm ² (abs), the pressure in condenser 6 is 3.7Kg/cm 2 (abs), and the pressure in evaporator 1 is 9.4Kg/cm ² (abs). The pressure inside is 0.6Kg/cm ² (abs).

As can be seen from these pressure values, the pressure within the heat pump system is not so high that conventional equipment such as a compressor can be used as is.

Further, when a high boiling point refrigerant is used, the air volume of the refrigerant gas becomes large, so an extra-tube condensing type is used for the condenser 6 which has the (lowest) temperature in FIG. However, even with high boiling point refrigerants, when the temperature rises, the specific volume of the refrigerant gas, that is, the air volume, decreases, so a shell-and-tube type condensing type is used for the condenser 9, which has the highest temperature in Figure 1. ing.

As mentioned above, depending on the change in specific volume due to the temperature of the refrigerant gas, the form of the refrigerant flowing in the condenser is
By using either the in-tube condensation type or the out-of-tube condensation type, the flow of refrigerant inside each condenser is appropriate, preventing an increase in pressure loss, and improving heat transfer performance.
Heat exchange action is performed efficiently.

Furthermore, if a non-azeotropic mixed refrigerant (a mixed refrigerant with different boiling points) is used as the refrigerant, the temperature will change from the time when the mixed refrigerant gas begins to condense in the condenser until it ends, so the temperature diagram will be As shown in the figure, energy is saved by the amount corresponding to the shaded area compared to the case where a single refrigerant as described above is used.

Examples of the above non-azeotropic mixed refrigerant include R11,
The main component is a high boiling point refrigerant such as R21, R112, R113, R114, R114B2 (more than 50% in mole fraction), and in addition to the above high boiling point refrigerant, R12, R13, R13B1, R14, R22, R500,
Consider low boiling point refrigerants such as R502. These mixed refrigerants have a saturation temperature of 15 at a temperature of 100°C.
Refers to refrigerants of kg/cm ² (abs) or less.

For example, R11+R14, R11+R500, R11+R502,
R11+R114 R113+R14, R113+R500, R113+R502,
R113+R114 R114+R12, R114+R14, R114+R22, R114
+R500, R114+R502 R112+R12, R112+R22, R112+R11, R112,
R114 etc. (Note that the left side of the above-mentioned mixed refrigerant indicates the main component.) Also, it goes without saying that this non-azeotropic mixed refrigerant includes a mixture of three or more types of refrigerants that satisfy the above-mentioned conditions.

The above explanation has been made regarding the case of a two-stage compressor and a two-stage condenser, but it goes without saying that the same effect can be obtained with a larger number of stages.

Further, as a compressor, it is of course applicable to all screw type, centrifugal type, and reciprocating type compressors.

(Effects of the Invention) As explained above, the present invention includes a plurality of devices that constitute a part of a heat pump cycle and exchange heat with an external liquid, that is, a plurality of condensers with different pressures,
Each condenser and its corresponding compressor are communicated separately so that refrigerant at an optimal temperature flows through each condenser, and at least the refrigerant flows through the condenser where the condensation temperature of the refrigerant reaches the highest temperature. temperature
Since it uses a high boiling point refrigerant with a pressure of 15 kg/cm ² (abs) or less at 100°C, it is possible to reduce the compression work of each stage of the compressor and save energy consumption, and the pressure at the final stage is low. Therefore, conventional equipment can be used as is. Also,
Since the condenser that reaches the highest temperature is a shell-and-tube type in-tube condenser, it has the effect of requiring less refrigerant charge and improves heat transfer performance without increasing pressure loss compared to an outside-tube type condenser. It also has the effect of being good.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing an embodiment of a heat pump to which the present invention is applied, FIG. 2 is a temperature diagram thereof, and FIG. 3 is a temperature diagram when a non-azeotropic mixed refrigerant is used as the refrigerant. FIG. 4 is an explanatory diagram of an in-tube condensation type condenser, and FIG. 5 is an explanatory diagram of an extra-tube condensation type condenser. 1... Evaporator, 4, 8... Compressor, 6, 9...
Condenser, 14, 16...pressure reducing device.

Claims (1)

[Claims] 1. An evaporator, a plurality of condensers with different pressures, a plurality of compression stages that send compressed gas at corresponding pressures to these condensers, a plurality of pressure reducing devices, and piping for these devices. Connected to the refrigerant by the temperature
In a heat pump using a high boiling point refrigerant with a saturation pressure of 15Kg/cm ² (abs) or less at 100℃,
Among the multiple condensers, at least the condenser where the refrigerant condenses at the highest temperature is configured as a shell-and-tube type in-tube condensing type, and the condenser with the lowest temperature is configured as an extra-tube condensing type. heat pump. 2. The heat pump according to claim 1, wherein the refrigerant is a non-azeotropic mixed refrigerant that has the above-mentioned high-boiling refrigerant as a main component and has a saturation pressure of 15 Kg/cm ² (abs) or less at a temperature of 100°C.