JPH0514185B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for adjusting the composition ratio of a mixed refrigerant in a heat pump using a non-azeotropic refrigerant mixture.

(Prior Art) Conventionally, various refrigerants (dichlorodifluoromethane: R12, chlorodifluoromethane: R22, etc.) have been used in heat pumps, but all of these are single refrigerants made of one type of refrigerant. As is well known, this heat pump uses a condenser to condense (liquefy) high-pressure, high-temperature gaseous refrigerant to raise the temperature of an external heat source (high-temperature side), while an expansion valve and an evaporator raise the temperature of a low-pressure, low-temperature gas refrigerant. The external heat source (low temperature side) is cooled by evaporating (vaporizing) a liquid refrigerant. The heat exchange relationship in the condenser and evaporator (countercurrent type) of a heat pump using such a single refrigerant can be expressed as in the T-S diagram in FIG. 4. In other words, the temperature T is plotted in the vertical direction of this figure, and the entropy S is plotted in the horizontal direction.
The line segments ab and ef represent the state changes of the refrigerant and the high-temperature external heat source (e.g., water) in the condenser, and the line segments cd and gh represent the state of the refrigerant and the low-temperature external heat source (also water) in the evaporator. It shows change, and since it is a single refrigerant, it is a line segment.
The condensation temperature and evaporation temperature, indicated by ab and cd, remain constant. Further, the arrows in the figure correspond to the flow of the refrigerant or the external heat source, and Δt ₁ and Δt ₂ represent the temperature difference at the entrance and exit of the evaporator or condenser of the external heat source.

Therefore, in this heat pump, the required power for one cycle of the refrigerant is the area (area) of the part surrounded by points a, b, c, and d.
It's called abcd. (same below).

By the way, as heat pumps have become widespread in recent years, the need for heat pumps that contribute to energy conservation has increased, especially for applications in large-scale heat utilization systems, and the need for heat pumps that contribute to energy conservation has increased, with a good coefficient of performance COP (= evaporation capacity / power). There was a strong demand for the development of a heat pump.

Therefore, the present inventors developed high boiling point refrigerants (trichlorofluoromethane: R11, dichlorotetrafluoroethane: R114, etc.) and low boiling point refrigerants (R12, R22, etc.).
When combined with a non-azeotropic refrigerant (such as We conducted various studies on the application of mixed refrigerants (referred to as mixed refrigerants) to heat pumps, and obtained the following analytical results.

In Figure 4 above, the temperature difference (af, ch) between points a and c and the load side is constant, and the temperature difference between the load side and the refrigerant side is the minimum value that allows heat exchange (pinch temperature difference). ) or more, and the line segment ab,
If the slope of cd can be freely selected, if this slope is equal to the slope of line segments ef and gh, then the area
Since abcd can be minimized, the COP of the heat pump is the best. FIG. 5 shows this best condition, and is the same as FIG. 4 except for the slopes of the line segments ab and cd. That is, in Fig. 5, Δt ₁ = ΔTe, Δt ₂ = ΔTc, that is, line segment ab and line segment ef
Also, line segment cd and line segment gh are parallel to each other, and normally ΔTc = approximately Te, so Δt ₁ = approximately Δt ₂ .

However, as a temperature condition on the load side, it may not be possible to make Δt ₁ =approximately Δt ₂ as described above. For example, when using a condenser to raise the temperature of water, which is an external heat source, from room temperature to the hot water supply temperature (in this case, Δt ₂ = approximately 50
℃), the evaporator cannot cool the water, which is an external heat source on the low temperature side, with a temperature difference equal to this temperature difference. This is because if you cool the water too much, it will freeze.

In this way, when Δt ₁ and Δt ₂ are significantly different,
As shown in Fig. 6, as long as line segment ab and line segment cd are parallel, the gradient of both lines has to be small due to the restriction of minute Δt ₁ , and it is not possible to use a mixed refrigerant. However, the problem was that the benefits of improving COP were small.

(Object of the Invention) The present invention has been made in view of the above conventional problems, and its purpose is to solve the problem even when the temperature difference at the entrance and exit of the external heat source is large between the condenser and the evaporator.
An object of the present invention is to provide a method for adjusting the composition ratio of a mixed refrigerant in a heat pump, which makes it possible to improve COP.

(Structure of the Invention) In order to achieve the above object, the present invention includes a positive displacement compressor main body, a first condenser, a gas-liquid separator, an economizer following the liquid reservoir of the gas-liquid separator, and a main expansion valve. , a closed loop leading to the compressor body via the evaporator, and a gas space in the upper part of the gas-liquid separator branching from the closed loop, passing through the second condenser and intermediate expansion valve, and then flowing into the economizer. A suction port that passes through the economizer while being isolated from the refrigerant and capable of heat exchange, and sucks the refrigerant from the evaporator of the compressor main body, and a discharge port that sends the refrigerant to the first condenser. By circulating the non-azeotropic mixed refrigerant through the closed loop of the heat pump formed by providing a flow path leading to an intermediate pressure portion between the outlet and the flow path, the first and second condensers and the evaporator The composition ratio of the refrigerant passing through the inside is made to differ.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a heat pump to which the method for adjusting the composition ratio of mixed refrigerant according to the present invention is applied, and the compressor body (hereinafter referred to as the body) 1 is arranged in series in two stages, a first condenser 2, and a separator 3. , a second condenser 4, an intermediate expansion valve 5, an economizer 6, a main expansion valve 7 and an evaporator 8. 1st
Refrigerant liquid and gas partially condensed in condenser 2 are transferred to separator 3
The high-pressure liquid is led to the economizer 6, and the gas is condensed in the second condenser 4, then passed through the intermediate expansion valve 5 and led to the economizer 6, where the high-pressure liquid is cooled and becomes a gas at high pressure. It is guided to the main body 1 on the stage side. The high-pressure liquid cooled by the economizer 6 passes through the main expansion valve 7, becomes a gas in the evaporator 8, and is guided to the main body 1 on the low-pressure stage side.

Note that the first condenser 2 and the second condenser 4 each have a tube 9 through which hot water, which is an external heat source on the high temperature side, flows, and the evaporator 8 has a tube 10 through which low-temperature heat source water, which is an external heat source on the low temperature side, flows. It is provided so that heat can be exchanged with the refrigerant.

By using the above-mentioned mixed refrigerant as the refrigerant and changing its composition appropriately before and after the separator 3, the refrigerant in the first condenser 2, the second condenser 4, and the evaporator 8 is connected to the external heat source. The structure is designed to achieve the most efficient heat exchange between the two.

Next, a method for adjusting the composition ratio of a mixed refrigerant according to the present invention and a change in the conditions of the refrigerant and external heat source due to the method will be described as applied to the heat pump having the above configuration.

First of all, as shown in FIG. 1, the state of the refrigerant circulating in the heat pump is as follows: the discharge side of the main body 1 on the high-pressure stage side is the state, the state is the state at the start of condensation in the first condenser 2, and the state is the state of the refrigerant circulating in the heat pump. The state of the liquid outlet, the state of the outlet of the economizer 6, the state of the inlet and outlet of the evaporator 8, the state of the start of condensation of the second condenser 4, the state of the outlet of the second condenser 4,
The states of the economizer inlet and outlet are as follows, and each state when the composition ratio of the mixed refrigerant is constant is shown by attaching a dash to each of the above states.

Also, as above, while the temperature difference at the entrance and exit of the external heat source is Δt ₁ on the low temperature side and Δt ₂ on the high temperature side,
The temperature difference between the inlet and outlet of the refrigerant evaporator 8 is ΔTe, and the temperature difference between the inlet of the first condenser and the outlet of the second condenser is ΔTc. Points a, b, c, and d in FIG. 4 correspond to the above states.

Therefore, the refrigerant is in a high-temperature, high-pressure gas state in the state, a boundary region between a high-temperature, high-pressure gas and a high-temperature, high-pressure liquid in the state, a high-temperature, high-pressure liquid state in the state, a low-temperature, high-pressure liquid state in the state, and a low-temperature, low-pressure gas-liquid mixed state in the state. , state is a low-temperature, low-pressure gas state, state is a state in the boundary region between a high-temperature, high-pressure gas and a high-temperature, high-pressure liquid, state is a high-temperature, high-pressure liquid state, state is a low-temperature intermediate-pressure gas-liquid mixed state, and state is a low-temperature, intermediate-pressure gas state. .

By the way, the temperature difference ΔTe, ΔTc between the start and end of evaporation or condensation of the mixed refrigerant is determined by the composition ratio of the high boiling point refrigerant X and the low boiling point refrigerant Y, and the temperature itself during evaporation and condensation is dependent on the pressure. The temperature increases as the pressure increases. Therefore, as shown in the vapor-liquid equilibrium diagram in Figure 2, the vapor and liquidus lines of the mixed refrigerant are separate lines even if the pressure is constant, and because the pressures are different, that is, the condensation pressure (c), Intermediate pressure (m), evaporation pressure
(e) is a separate line (in the diagram, subscripts c, m, and e are attached to each pressure to distinguish it).

As an example, if the composition ratio of the mixed refrigerant up to the first condenser 2 is set to X ₁ , the liquid in the separator 3 separated by the first condenser 2 has a composition ratio of X with a large proportion of high boiling point refrigerant. ₂ , and the gas in the separator 3 has a composition ratio of X ₃ with a large proportion of low boiling point refrigerant. Second
From the figure, the composition ratios X ₂ and X ₃ are determined by the amount of condensation in the first condenser 2, so by adjusting the amount of refrigerant condensed in the first condenser 2 and the second condenser 4, the composition ratio can be adjusted. X ₂ and X ₃ are adjustable. Therefore, when the change in the state of the mixed refrigerant is represented on the vapor-liquid equilibrium diagram of FIG. 2, it changes in the order of the numbers on the polygonal line and the numbers on the polygonal line. Note that the numbers 1' to 6', 9', and 10' on the broken lines represent states corresponding to the above states 1 to 6, 9, and 10, assuming that the composition ratio is constant.

As is clear from the figure, when the composition ratio is constant, ΔTc′ = approximately ΔTe′, which is determined by the composition ratio of the mixed refrigerant in the liquid in the separator 3 and the mixture in the gas, as described above. By adjusting the composition ratio of the refrigerant, ΔTc＞
It can be ΔTe.

Figure 3 is a T-S similar to Figures 4 to 6 above.
The diagram shows the case where the example is applied, and there is a relationship such that Δt ₂ ≫ Δt ₁ as the temperature condition of the external heat source, and from the state of the composition ratio X ₁ shown by the broken line, the composition ratio X ₁ and By drawing a solid line ab in _the state of X ₃ and a solid line cd in the state of evaporation with a composition ratio of ΔTc′,
By ΔTe<ΔTe′), line segments a and b are transformed into line segments e and f
Then, the line segments c and d can be brought close to parallel to the line segments g and h, and the power loss corresponding to the areas A and B of the hatched portions is eliminated, and the COP of the heat pump can be improved. Further, in the above embodiment, the first and second
The amount of condensation in the condensers 2 and 4 is adjusted based on the temperature difference between the outlet of the second condenser 4 and the inlet of the high-temperature heat source tube 9. By adjusting the flow rate ratio of , it is possible to more accurately adjust the composition ratio.

(Effects of the Invention) As is clear from the above description, according to the present invention, the positive displacement compressor main body, the first condenser, the gas-liquid separator, the economizer following the liquid reservoir of the gas-liquid separator, and the main A closed loop that passes through an expansion valve and an evaporator to the compressor body, and a branch from the closed loop that branches from the gas space above the gas-liquid separator, passes through a second condenser and an intermediate expansion valve, and then connects to the economizer. The refrigerant is passed through the economizer in a state where it is isolated from the refrigerant inside and capable of heat exchange, and is sent to the suction port for sucking the refrigerant from the evaporator of the compressor main body, and to the first condenser. By circulating the non-azeotropic mixed refrigerant through the closed loop and the flow path of the heat pump, which is formed by providing a flow path leading to an intermediate pressure portion between the discharge port and the flow path, the first and second condensers and The composition ratio of the refrigerant passing through the evaporator is varied.

Therefore, even if the temperature difference at the entrance and exit of the external heat source is large between the condenser and the evaporator, it is possible to adjust the amount of refrigerant condensed in the first and second condensers, and the amount of refrigerant condensed in the first and second condensers can be adjusted. and the temperature difference during evaporation can be approximated to the temperature difference of the external heat source,
As a result, it has the effect of being able to obtain a high COP.

[Brief explanation of drawings]

Fig. 1 is an equipment configuration diagram of a heat pump to which the method according to the present invention is applied, Fig. 2 is a vapor-liquid equilibrium diagram showing the state of mixed refrigerant in the heat pump of Fig. 1, and Fig. 3
The figure is a T-S diagram corresponding to Figure 2, Figures 4 to 6.
The figure is a T-S diagram showing the relationship of heat exchange in a conventional heat pump. 1...Main body (compressor main body), 2...First condenser,
3...Separator, 4...Second condenser, 5...Intermediate expansion valve, 6...Economizer, 7...Main expansion valve, 8
……Evaporator.

Claims (1)

[Scope of Claims] 1. A positive displacement compressor main body, a first condenser, a gas-liquid separator, an economizer following the liquid reservoir of the gas-liquid separator, a main expansion valve, an evaporator, and then the compressor main body. The gas space at the top of the gas-liquid separator branches off from the closed loop, passes through a second condenser and an intermediate expansion valve, and is isolated from the refrigerant in the economizer, and heat is removed. A flow exchangeably passes through the economizer and reaches an intermediate pressure portion of the compressor body between an inlet for sucking refrigerant from the evaporator and an outlet for delivering refrigerant to the first condenser. By circulating a non-azeotropic mixed refrigerant through the closed loop and the flow path of the heat pump formed by providing a path, the composition ratio of the refrigerant passing through the first and second condensers and the evaporator is made different. A method for adjusting the composition ratio of a mixed refrigerant in a heat pump, characterized in that: 2. Mixing in the heat pump according to claim 1, wherein the amount of condensation of the refrigerant is adjusted by adjusting the flow rate ratio of the high temperature heat source flowing through the first and second condensers. Method for adjusting composition ratio of refrigerant.