JP2002364936A - Refrigeration unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refrigeration unit capable of maintaining or enhancing effects of the conventional arts, i.e., improvement of COP, by compactly constituting an integrated unit of a supercooler and an evaporator and employing an easy constitution. SOLUTION: The supercooler 5 includes a first internal passage 15a allowing a non-azeotropic mixture solution upstream of an expansion valve 16 to flow, and a second internal passage 15b branched from an internal passage 17a of the evaporator 17 provided downstream of the expansion valve 16. The non- azeotropic mixture solution is allowed to flow opposite to the first internal passage 15a to join the internal passage 17a of the evaporator 17, and is constituted integrally with the evaporator 17. The circulation flow rate of the non- azeotropic mixture solution flowing in the internal passage 17a, and the circulation flow rate of the non-azeotropic solution flowing in the second internal passage 15b of the supercooler 15, are determined on the basis of the ratio of their circulation flow rates.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention belongs to the technical field of a refrigerating apparatus using a non-azeotropic mixed refrigerant.

[0002]

2. Description of the Related Art In recent years, in order to protect the ozone layer surrounding the earth and prevent global warming, the use of a refrigerant widely used, for example, the refrigerant R22, has been internationally banned and replaced with the refrigerant R22. The development of refrigerants is urgently needed.
As an alternative refrigerant to the refrigerant R22, the refrigerant R4 is currently used.
07C and R410A are attracting attention. However,
Since these refrigerants R407C and R410A can obtain only a low coefficient of performance (COP: evaporation capacity / power) even when used alone as compared with refrigerant R22, they use a non-azeotropic mixed refrigerant composed of a plurality of refrigerants. Various proposals have been made to improve the coefficient of performance (hereinafter referred to as COP).

[0003] In the case of a refrigerating apparatus using a non-azeotropic mixed refrigerant, a refrigerating apparatus employing a form in which a heat exchanger exchanges heat of a fluid having a small temperature difference in a counterflow (counterflow heat exchange) is adopted. It is known that the coefficient of performance of the device is significantly improved. By the way, in the evaporator, if the refrigerant gas at the refrigerant outlet of the evaporator is in an excessively overheated state, the heat transfer coefficient of the evaporator is greatly reduced due to the influence of the refrigerant gas, so that heat exchange with a small temperature difference is performed. It is also known that you can no longer do. In order to prevent such inconveniences and to realize the counterflow heat exchange with the small temperature difference as described above, the refrigerant gas at the refrigerant outlet of the evaporator is set to an appropriate degree of superheat, and thus to an appropriate wet state. There is a need. Therefore, specifically, it has been proposed to employ a refrigerant heat exchanger (supercooler) that performs heat exchange between refrigerants.

It is very important that the supercooler is designed to minimize the pressure loss in order to prevent the heat exchange performance from deteriorating. For example, when a so-called shell-and-tube type is used as a subcooler, a considerable number of tubes are required to suppress the pressure loss, and the unvaporized portion of the refrigerant is evenly distributed to the tubes. Due to the extreme difficulty in distributing, after all, the evaporative heat transfer performance will be similar to that using a single gas. If high evaporative heat transfer performance is required in such a shell-and-tube type supercooler, there arises a problem that the supercooler must be excessively large in design.

For example, Japanese Patent Application Laid-Open No. 2000-18735 discloses that
A refrigeration system using a non-azeotropic mixture medium to make the superheater itself compact and capable of improving the COP is disclosed. In order to solve the above problem, the refrigeration apparatus according to this conventional example integrates a supercooler and an evaporator, and connects a refrigerant outlet of the evaporator and a refrigerant inlet of a lower part of the supercooler by piping. It was done.

[0006] The refrigeration apparatus according to this conventional example will be described below using the same names described in the publication.

[0007] The refrigeration apparatus according to the conventional example includes at least a compressor, a first heat exchanger for condensation (hereinafter, referred to as a condenser),
A closed circulation path for a non-azeotropic mixed refrigerant including a liquid receiver, a first expansion valve, and a second heat exchanger for evaporation (hereinafter, referred to as an evaporator).
(Corresponding to a closed circulation channel).
The high-pressure refrigerant before reaching the first expansion valve is allowed to flow and flow from top to bottom, and is allowed to flow from the lower portion toward the first expansion valve, while the low-pressure refrigerant flowing from the evaporator is allowed to flow and from below. A liquid subcooler (hereinafter, referred to as a supercooler), which is a vertical one-pass counterflow type heat exchanger that flows upward and gasifies and flows out toward the suction portion of the compressor, is provided. The evaporator is a vertical one-pass counter-flow type in which the refrigerant flowing through the first expansion valve flows from bottom to top while the water to be cooled flows from top to bottom, and the refrigerant containing the unevaporated component. Withstand pressure on both sides of a plate group consisting of a plurality of plates forming a fluid flow path of a plate heat exchanger, wherein each of the subcooler and the evaporator is discharged toward the subcooler. One of the end face plates made of members In addition to the omitted structure, the two sides of the single-sided plate were abutted against each other, opposed to the abutted side surface, and the high-pressure refrigerant outflow inlet and the low-pressure refrigerant outflow inlet of the supercooler were provided. A first opposite face plate made of a pressure-resistant member and a second end face plate made of a pressure-resistant member provided with a refrigerant outflow port and a cooled water outflow port of the evaporator, facing the contacted side surface; The subcooler and the evaporator are integrally formed by sandwiching each plate group of the evaporator.

[0008]

In the refrigerating apparatus according to the prior art, as described above, the supercooler and the evaporator are integrally formed, and the refrigerant outlet of the evaporator and the supercooler are connected. The refrigerant outlet at the lower part of the vessel is connected by piping. Therefore, in the refrigeration apparatus according to the conventional example, since the entire amount of the refrigerant liquid flows into the subcooler, a large number of plates are required to suppress the pressure loss of the refrigerant liquid flow. Therefore, there arises a problem that the integrally formed supercooler and evaporator are large and their structures are complicated.

Accordingly, an object of the present invention is to make the integrated subcooler and evaporator compact and have a simple structure, while maintaining or improving the effect of the conventional example of improving COP. An object of the present invention is to provide a refrigerating device for squeezing.

[0010]

Means for Solving the Problems The present invention has been made in view of the above-mentioned circumstances, and in order to solve the above-mentioned problems, means adopted by a refrigeration apparatus according to claim 1 of the present invention is as follows. In a refrigeration system having a closed circulation path for a non-azeotropic mixed refrigerant including at least a compressor, a condenser, an expansion valve, and an evaporator, the first non-azeotropic mixed refrigerant upstream of the expansion valve flows.
An internal flow path, a branch from an internal flow path of the evaporator downstream of the expansion valve, or a flow path between the expansion valve and the evaporator, and non-azeotropically opposed to the first internal flow path A subcooler in which the mixed refrigerant flows and further includes an internal flow path of the evaporator or a second internal flow path that merges with a flow path between the evaporator and the compressor is integrated with the evaporator. And the circulating flow rate of the non-azeotropic mixed refrigerant flowing through the internal flow path of the evaporator and the circulating flow rate of the non-azeotropic mixed refrigerant flowing through the second internal flow path of the supercooler It is characterized by being set based on the flow ratio.

The means employed by the refrigeration apparatus according to claim 2 of the present invention is the refrigeration apparatus according to claim 1,
The refrigerant circulation flow rate ratio is a weight x of the refrigerant gas in the non-azeotropic mixed refrigerant at the refrigerant outlet of the evaporator, and the quality x is a predetermined amount in which the unevaporated component remains in the non-azeotropic mixed refrigerant. Is set to be equal to or less than the first set value,
The superheat degree tsh of the non-azeotropic mixed refrigerant at the refrigerant outlet of the subcooler is set to be equal to or more than a second predetermined value, the specific heat of the non-azeotropic mixed refrigerant gas is Cpg, and Assuming that the latent heat of the azeotropic mixed refrigerant liquid is λ, the latent heat is determined so as to satisfy an expression of tsh × Cpg / {(1-x) × λ}.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a refrigeration apparatus according to an embodiment of the present invention will be described with reference to FIG. As is well understood from FIG. 1, the refrigeration apparatus converts a non-azeotropic mixed refrigerant including a plurality of refrigerants into a compressor 1.
1, condenser 12, liquid receiver 13, subcooler 15, expansion valve 1
6. A circulation closed flow path L that passes through the evaporator 17 and returns to the compressor 11 is provided.

The compressor 11 may be, for example, a single-stage compressor or a two-stage compressor in which low-stage and high-stage compressor bodies are arranged in series.
Any type of stage compressor may be used, and the type may be, for example, any of a screw type, a reciprocating type, and a turbo type. In the case of the two-stage compressor, an intermediate flow path (not shown) is located between the suction port S of the low-stage compressor main body and the outlet of the high-stage compressor main body, and is connected to both of the suction port S and the outlet T. It communicates with the portion of the closed circulation channel L that does not communicate.

The condenser 12 is of a plate type of a conventionally known vertical one-pass counterflow type. In the condenser 12, the refrigerant discharged from the outlet T of the compressor 11 flows in from the refrigerant inlet 21 provided in the upper part and flows from the upper part to the lower part, and flows out from the refrigerant outlet 22 provided in the lower part. The cooling water flows from the cooling water inlet 23 provided at the lower part to flow from the lower part to the upper part, and flows out from the cooling water outlet 24 provided at the upper part, so that the heat exchange between the refrigerant and the cooling water is performed. Is configured.

The liquid receiver 13 is disposed below the condenser 12. Therefore, the refrigerant liquid condensed in the condenser 12 immediately flows into the liquid receiver 13 without staying in the condenser 12. Thus, the receiver 13
Is disposed below the condenser 12, so that the condensed refrigerant liquid is immediately discharged to the outside of the condenser 12, so that good heat exchange is performed.

The supercooler 15 and the evaporator 17 are integrally formed. With such a configuration, in the evaporator 17, a state in which the refrigerant in the liquid state is contained as much as possible, that is, the weight ratio of the gas in the refrigerant (quality)
Is made as small as possible, and heat exchange is performed between the refrigerant and the liquid to be cooled, for example, cooling water, and the efficiency is improved as compared with the case of heat exchange between the gaseous refrigerant and the liquid to be cooled. Heat exchange is often performed. The supercooler 15 supercools the high-pressure refrigerant by using the heat of vaporization of the low-pressure medium in the liquid state from the evaporator 17. Since the temperature is reduced according to the temperature reduction phenomenon peculiar to the non-azeotropic refrigerant mixture, the heat exchange efficiency is improved and the COP is also improved.

Specifically, the high-pressure refrigerant flowing out of the liquid receiver 13 flows into the supercooler 15 from the high-pressure refrigerant inlet 25 provided at the upper part, and the first internal flow path 15 provided therein is provided.
a, and then a high-pressure refrigerant outlet 2 provided in the lower part
After flowing out of the expansion valve 16 once, it flows into the evaporator 17 downstream of the expansion valve 16 via the expansion valve 16. The high-pressure refrigerant in the liquid state is expanded by the expansion valve 16, and the refrigerant having a reduced pressure and temperature flows in the liquid state from the refrigerant inlet 35 below the evaporator 17, and branches in the evaporator 17. And one is the evaporator 17
And the other is connected to a second internal flow path 15b provided inside the subcooler 15. In the supercooler 15, the first internal flow path 15a and the second internal flow path 15b are configured to be opposed to each other. Since the refrigerant flows through these insides, heat exchange between the refrigerants is effective. Will be promoted.

The refrigerant flowing through the internal flow path 17a provided inside the evaporator 17 flows from the lower part to the upper part, and flows from the upper refrigerant outlet 36 to the second subcooler 15 of the liquid subcooler 15.
The refrigerant merges with the refrigerant flowing from the internal flow path 15b, and flows out in a state including an unevaporated component. Further, in the evaporator 17, the water to be cooled flows in from the upper liquid inlet 37, flows from the upper part to the lower part, and after the heat exchange with the refrigerant, flows out from the lower liquid outlet 38 in the lower part. It is made to let.

When the configuration of the refrigeration apparatus is used as a so-called chiller, cooling water cooled by a cooling tower is usually used as a cooling fluid flowing into the condenser 12. The temperature of the cooling water flowing into 23 is about 32 ° C. Accordingly, the temperature of the fluid to be cooled flowing into the evaporator 17 under the design conditions is, for example,
It will be around 12-7 ° C. Therefore, the liquid temperature of the cooling refrigerant condensed in the condenser 12 becomes about 35 ° C., and the evaporator 1
The evaporation temperature of the refrigerant at 7 is about 5 ° C. Therefore, in the subcooler 15, the degree of superheat on the side of the evaporator 17 can be up to about 20 ° C.

In the refrigerating apparatus having such a configuration,
Further, the refrigerant circulation flow ratio a / b between the circulation flow rate a of the refrigerant flowing through the internal flow path 17a of the evaporator 17 and the circulation flow rate b of the refrigerant flowing through the second internal flow path 15b of the subcooler 15 is a predetermined value. By maintaining the refrigeration system according to the conventional example of improving the COP with a compact integrated supercooler and evaporator, with a simple configuration, and maintaining or improving the efficiency. To realize a refrigeration apparatus that enables the above ".

The refrigerant circulation flow ratio a / b is determined by the evaporator 17
Unevaporated refrigerant liquid (unevaporated component) remains in the refrigerant at the refrigerant outlet 36 side of the refrigerant, and is predetermined to be equal to or less than the first predetermined value, the quality of the refrigerant being the weight ratio of gas in the refrigerant, It is determined by the degree of superheat of the refrigerant on the refrigerant outlet 26 side of the subcooler 15 which is predetermined so as to be equal to or more than a second predetermined value (superheat temperature). For example, it is preferable to determine the first predetermined value to be 1 and the second predetermined value to be 5 ° C. or more.

More specifically, the refrigerant quality at the refrigerant outlet 36 side of the evaporator 17 is x, the superheat degree (° C.) of the refrigerant at the refrigerant outlet of the subcooler 15 is tsh, and the refrigerant gas Has a specific heat (KJ / kg ° C.) of Cpg,
When the latent heat (KJ / kg) of the refrigerant liquid is λ, the refrigerant circulation flow rate ratio a / b is tsh × Cpg / {(1-x) × λ}.
Is determined so as to satisfy the following equation. The specific heat of the refrigerant gas is a fixed value determined by the type of the refrigerant (gas), and the latent heat of the refrigerant liquid is a fixed value determined by the type of the refrigerant (liquid).

Here, for example, assuming that the refrigerant circulation flow ratio a / b is 8/2 and the degree of superheat of the refrigerant is 20 ° C., the latent heat of the refrigerant liquid is about 200 KJ / kg, and the specific heat of the refrigerant gas is about Since it is 1.2 KJ / kg, the refrigerant at the refrigerant outlet 36 of the evaporator 17 is in a wet state with the quality x of 0.97, so that it is possible to exhibit excellent cooling performance.

That is, the quality x of the refrigerant at the refrigerant outlet 36 side of the evaporator 17 is equal to or less than a predetermined first predetermined value, and the degree of superheat of the refrigerant at the refrigerant outlet side of the subcooler 15 is set in advance. The refrigerant circulation flow rate ratio a / b is determined so as to be equal to or higher than a predetermined second predetermined value (predetermined temperature). Then, the refrigerant flowing from the refrigerant inlet 35 may be divided into the internal flow path 17a of the evaporator 17 and the second internal flow path 15b of the supercooler 15 so that the flow rate becomes the determined flow rate. . As a feature of the subcooler 15 using the non-azeotropic mixed refrigerant, the evaporation start temperature is reduced by an amount corresponding to the supercooling, so that the heat exchange efficiency in the evaporator 17 is improved.

It should be noted that the flow of refrigerant into the internal flow path 17a of the evaporator 17 and the second internal flow path 15b of the subcooler 15
When the same type of plate is used for the evaporator 17 and the subcooler 15, the supercooler having a higher ratio of the superheated gas has a larger refrigerant pressure loss at the same circulation flow rate. If the pressure loss difference is taken into consideration, it is simply determined by the ratio of the number of plates.

However, if it is determined simply from the relationship between the required heat exchange amount of the evaporator and the subcooler and the heat transfer area only by the circulation flow ratio, if the predetermined set conditions cannot be maintained, the evaporator 17 A method of changing the circulation flow ratio assuming that the types of plates of the and the supercooler 15 have different pressure losses at the same circulation flow, and a method of changing the circulation flow ratio by inserting an orifice at the boundary between the evaporator 17 and the supercooler 15 It is also possible to employ.

Further, according to the refrigeration apparatus of the present embodiment, the low-temperature and low-pressure refrigerant liquid flowing into the evaporator 17 is divided in the evaporator 17, and one of the refrigerant liquids is provided inside the evaporator 17. And the other flows through a second internal flow path 15b provided inside the subcooler 15, and the entire amount of the refrigerant liquid flows as in the refrigeration apparatus according to the conventional example. Since the configuration is not such that it flows into the cooler, the pressure loss can be suppressed without using many plates, and the structure can be simplified and the size can be reduced.

Incidentally, in the case of a refrigeration system having a large compression ratio, an economizer is used to improve the cooling performance. In this case, a high degree of superheat cannot be obtained because the high-pressure refrigerant liquid is supercooled by the economizer. However, if the supercooling temperature of the refrigerant by the economizer is properly selected, the above-mentioned effects are not hindered.

In the above, the refrigerant liquid which has been reduced in pressure and temperature by the expansion of the expansion valve 16 is branched in the evaporator 17, one of which is communicated with the internal flow path 17a provided inside the evaporator 17, and the other is filtered. The liquid subcooler is connected to the second internal flow path 15b provided inside the cooler 15 and flows through the internal flow path 17a provided inside the evaporator 17 to exchange heat with the liquid to be cooled. The case has been described as an example where the refrigerant flowing from the fifteen second internal flow paths 15b is combined and allowed to flow out of the refrigerant outlet 36 at the upper part of the evaporator 17.

However, the external pipe branched from the flow path between the expansion valve 16 and the evaporator 17 is connected to the lower part of the second internal flow path 15b of the subcooler 15, while the second internal flow path 15b The other end of the external pipe connected to the upper part of the evaporator 1
The same function can be achieved with a configuration that is connected to the flow path between the compressor 7 and the compressor 11, so that the configuration of the refrigeration apparatus is not limited to the above embodiment.

[0031]

The refrigeration apparatus according to claim 1 or 2 of the present invention has a first internal flow path through which a non-azeotropic mixed refrigerant flows upstream of an expansion valve of the refrigeration apparatus, and an evaporator downstream of the expansion valve. An internal flow path, or branches off from a flow path between the expansion valve and the evaporator, a non-azeotropic mixed refrigerant flows in opposition to the first internal flow path, and further an internal flow path of the evaporator, Alternatively, a subcooler that includes a second internal flow path that merges with a flow path between the evaporator and the compressor is formed integrally with the evaporator, and a non-cooling device that flows through the internal flow path of the evaporator is formed. The circulating flow rate of the boiling mixed refrigerant and the circulating flow rate of the non-azeotropic mixed refrigerant flowing through the second internal flow path of the supercooler are configured to be set based on the refrigerant circulating flow rate ratio.

Therefore, according to the refrigeration system of the present invention, the refrigerant circulation flow ratio is adjusted so that the quality of the refrigerant at the refrigerant outlet side of the evaporator is equal to or less than a predetermined value. Then, it is determined that the degree of superheat of the refrigerant at the refrigerant outlet side of the subcooler is equal to or greater than a predetermined value, and the low-pressure, low-temperature refrigerant liquid is reduced inside the evaporator by adiabatic expansion by the expansion valve. Sub-cooling is performed by diverting and flowing at an appropriate ratio into the flow path and the second internal flow path that causes the counterflow to flow to the first internal flow path of the supercooler through which the high-pressure refrigerant liquid to be supercooled flows. The high-pressure refrigerant liquid can be effectively cooled by the evaporator, and the quality of the refrigerant at the refrigerant outlet side of the evaporator can be reduced, so that the excellent effect that excellent cooling performance can be exhibited. is there.

Further, according to the refrigeration apparatus according to claim 1 or 2 of the present invention, unlike the refrigeration apparatus according to the conventional example, since it is not configured to allow the entire amount of the refrigerant liquid to flow into the subcooler, many plates are required. There is an excellent effect that the pressure loss can be suppressed even before use, the structure of the integrally formed supercooler and evaporator can be simplified, and the size can be reduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an entire configuration of a refrigeration apparatus according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Compressor, 12 ... Condenser, 13 ... Liquid receiver, 15 ... Supercooler, 15a ... First internal flow path, 15b ... Second internal flow path, 16 ... Expansion valve, 17 ... Evaporator, 17a ... Internal flow path 21: refrigerant inlet, 22: refrigerant outlet, 23: cooling water inlet, 24: cooling water outlet, 25: high-pressure refrigerant inlet, 2
6 high-pressure refrigerant outlet 35 refrigerant inlet 36 refrigerant outlet 37 liquid inlet to be cooled 38 liquid outlet to be cooled L closed circulation channel S suction inlet T outlet (Compressor)

Claims (2)

[Claims] 1. A refrigeration system having a closed circulation path for a non-azeotropic mixed refrigerant including at least a compressor, a condenser, an expansion valve, and an evaporator, wherein the non-azeotropic mixed refrigerant upstream of the expansion valve flows. A first internal flow path, a flow path branched from the internal flow path of the evaporator downstream of the expansion valve, or a flow path between the expansion valve and the evaporator; An azeotropic mixed refrigerant flows, and a subcooler that further includes an internal flow path of the evaporator, or a second internal flow path that merges with a flow path between the evaporator and the compressor, is a subcooler. The circulating flow rate of the non-azeotropic mixed refrigerant formed integrally and flowing through the internal flow path of the evaporator, and the circulating flow rate of the non-azeotropic mixed refrigerant flowing through the second internal flow path of the subcooler are those A refrigeration apparatus characterized by being set based on a refrigerant circulation flow ratio. 2. The refrigerant circulating flow rate ratio is a quality x which is a weight ratio of a refrigerant gas in a non-azeotropic mixed refrigerant at a refrigerant outlet of the evaporator, and an unevaporated component is contained in the non-azeotropic mixed refrigerant. It is set so as to be equal to or less than the remaining predetermined first set value, and the superheat degree tsh of the non-azeotropic mixed refrigerant at the refrigerant outlet of the supercooler is equal to or larger than the second predetermined set value. Assuming that the specific heat of the non-azeotropic mixed refrigerant gas is Cpg and the latent heat of the non-azeotropic mixed refrigerant liquid is λ, the expression tsh × Cpg / {(1-x) × λ} is satisfied. The refrigeration apparatus according to claim 1, wherein the refrigeration apparatus is determined to be operated.