US20140231049A1

US20140231049A1 - Vapor compression refrigeration system

Info

Publication number: US20140231049A1
Application number: US14/180,841
Authority: US
Inventors: Hiroaki Matsushita
Original assignee: Mac Inc Japan
Current assignee: MAC Co Ltd; Mac Inc Japan
Priority date: 2013-02-18
Filing date: 2014-02-14
Publication date: 2014-08-21
Also published as: KR101405759B1

Abstract

A vapor compression refrigeration system includes a subcooler provided between a condenser and an evaporator, which is formed by a heat exchanger integrally having a primary side and a secondary side into which a refrigerant which has passed through the primary side flows and in which the primary side and the secondary side have the same heat transfer area and capacity. An expansion valve is provided at a refrigerant entrance on the secondary side of the subcooler, and a primary expansion valve is provided at a refrigerant entrance on the primary side of the subcooler to which the refrigerant is introduced in a vapor compression refrigeration cycle having stages of compression, condensation, expansion and evaporation of the refrigerant. A bypass is provided in the primary expansion valve at the refrigerant entrance on the primary side.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a vapor compression refrigeration system incorporating a subcooler, and particularly relates to a vapor compression refrigeration system incorporating a subcooler capable of largely improving refrigeration performance and saving energy by feeding a refrigerant which is previously supercooled to an expansion valve performing expansion (reducing pressure and reducing temperature) as a previous stage of evaporation in the process of the refrigeration system.
2. Description of Related Art
It has been known from the past as shown in Patent Documents 1 to 7 that the subcooler including a heat exchanger is incorporated as a factor for improving the effect of cooling or heating in a refrigeration system using a refrigerant gas. In these Patent Documents 1 to 7, there is disclosed the heat exchanger in which a primary side and a secondary side are integrated, the refrigerant gas is introduced to the primary side, then, the refrigerant gas which has passed through the primary side is fed to the secondary side through an expansion valve, and mutual heat energies become heat sources of condensation and evaporation respectively on the primary side and the secondary side through a heat transfer plate. The heat energies increase respective functions by synergistic effect and the primary side and the secondary side become stable in operation by the change over time.
In Patent Document 8, a heat exchange mechanism provided with a capillary tube instead of the expansion valve is disclosed.
However, in the related art, in a refrigeration system incorporating the above-described heat exchanger, defrosting in an almost perfect state is limited, and excessive work and expenses are spent for the defrosting. Also in a heating apparatus, there is a limit for operating the apparatus efficiently and safely particularly in cold regions, and it is practical to rely on a heater using electricity in defrosting.

[Patent Documents]

[Patent Document 1] JP-A-2003-214731
[Patent Document 2] JP-A-2004-361033
[Patent Document 3] JP-A-2005-98817
[Patent Document 4] JP-A-2005-114267
[Patent Document 5] JP-A-2006-64331
[Patent Document 6] JP-A-2009-156563
[Patent Document 7] JP-A-2011-58652
[Patent Document 8] Microfilm in JP-UM-A-56-155277

SUMMARY OF THE INVENTION

A problem to be solved by the present invention is a point that there has been no apparatus or vapor compression refrigeration system capable of increasing and improving refrigeration performance as well as saving energy by feeding the refrigerant with a further lower temperature and lower pressure into the expansion process as the previous stage of the evaporation process, and thus capable of sufficiently exerting the effect of heating and defrosting in cold regions.
In order to solve the above problem, there is provided a vapor compression refrigeration system including a subcooler incorporated between a condenser and an evaporator, which is formed by a heat exchanger integrally having a primary side and a secondary side into which a refrigerant which has passed through the primary side flows and in which the primary side and the secondary side have the same heat transfer area and capacity, an expansion valve provided at a refrigerant entrance on the secondary side of the subcooler, and a primary expansion valve also provided at a refrigerant entrance on the primary side of the subcooler to which the refrigerant is introduced in a vapor compression refrigeration cycle having stages of compression, condensation, expansion and evaporation of the refrigerant, which includes a bypass in the primary expansion valve at the refrigerant entrance on the primary side. A rotating-permanent magnet induction heater (magnet heater) is interposed between the evaporator to which the refrigerant is introduced from a refrigerant exit on the secondary side of the subcooler and a compressor to which the refrigerant is returned. In the subcooler, the primary side is a supercooled liquid generating unit and the secondary side is low-temperature unit for cooling the primary side, and a temperature of the refrigerant which has passed through the primary side is lower than a temperature of the refrigerant which has passed through the primary side.
In the vapor compression refrigeration system according to the present invention, the subcooler has a structure in which an outer surface thereof is covered by a heat insulating material to prevent heat releasing and heat absorbing, and cellular material-type urethane foam is used as the heat insulating material.
Furthermore, in the vapor compression refrigeration system according to the present invention, a refrigerant circuit incorporating the two subcoolers is formed for cooling and refrigerating as well as heating and defrosting.
The subcooler and the vapor compression refrigeration system incorporating the subcooler according to the present invention are configured as described above. Accordingly, the pressure and temperature of the refrigerant which have been reduced in the condensation process are further reduced to be low in two stages by the subcooler before the refrigerant is introduced to the expansion process (expansion valve). Accordingly, three stages of reduction of pressure and temperature are performed together with the subsequent expansion valve, the refrigerant becomes in a supercooled state with a low temperature to a point on a saturation liquid line in a P-h diagram to thereby obtain the refrigeration performance which has not been attained in the past. It is also possible to skip the primary expansion valve by providing the bypass.
As the outer surface of the subcooler is heat insulated, the heat releasing and absorbing from the subcooler are suppressed to an extremely slight amount, and energy is transferred only between refrigerants on the primary side and the secondary side, therefore, the efficiency is extremely improved, and further, the latent heat of condensation is increased as well as the latent heat of evaporation is increased. Accordingly, the refrigeration efficiency can be improved by 20 to 30%, and can be improved by 50% in the optimal case as compared with the related art.
Furthermore, two subcoolers are arranged in the circuit to be switched between cooling/refrigerating and heating/defrosting, thereby drastically improving the cycle efficiency of respective cases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a subcooler in a two-stage pressure reduction system to which the present invention is applied;

FIG. 2 is a partial cross-sectional view;

FIG. 3 is a P-h diagram showing transition of latent heat in the two-stage pressure reduction subcooler;

FIG. 4 is a T-s diagram in a related-art refrigeration cycle;

FIG. 5 is a T-s diagram of a refrigeration cycle using the two-stage pressure reduction subcooler;

FIG. 6 is a circuit diagram showing an example in which a rotating-permanent magnet induction heater is incorporated;

FIG. 7 is a cycle circuit diagram at the time of cooling and refrigerating: and

FIG. 8 is a cycle circuit diagram at the time of heating and defrosting.

DESCRIPTION OF EMBODIMENTS

The present invention has been made as shown in the drawings and as explained in an embodiment.

Embodiment 1

Next, a preferred embodiment of the present invention will be explained with reference to the drawings. A numeral 1 in the drawings denotes a two-stage pressure reduction subcooler used in the present invention. The two-stage pressure reduction subcooler 1 is incorporated between a condensation process (condenser) and an expansion process (expansion valve) of the vapor compression refrigeration system on a cycle circuit.
The two-stage pressure reduction subcooler 1 is formed in an integral casing, in which a primary side 2 to which a refrigerant is introduced from the condenser and a secondary side 3 which the refrigerant which has passed through the primary side is introduced to and passes through are integrally included in a manner of being sectioned by a piece of heat transfer plate 4. Accordingly, the primary side 2 and the secondary side 3 have the same heat transfer area and the same capacity.
Moreover, a primary expansion valve 5 is provided in a refrigerant introducing port on the primary side 2 and a secondary expansion valve 6 is provided in an introducing port on the secondary side 3 for the refrigerant which has passed through the primary side 2, that is, the refrigerant fed from the condenser is allowed to pass in series, and the refrigerant which has passed through the secondary side 3 is fed to an expansion valve 7 arranged on a previous stage of an evaporation process (evaporator).
Furthermore, the outer surface of the subcooler 1 is covered by a heat insulating material 8 except portions of the refrigerant introducing ports and discharging ports to thereby control heat releasing and heat absorbing from the subcooler 1 so as to be minimum. In this case, cellular material-type urethane foam is used as the heat insulating material 8, which is configured to respond to the external shock.
Here, the operation of the two-stage pressure reduction subcooler 1 will be explained. The refrigerant which has passed through the condenser is in a vapor-liquid two phase uncondensed state (refrigerant temperature T3), which passes through the primary expansion valve 5 and is introduced to the primary side 2. At this time, the pressure of the refrigerant is reduced and the temperature is reduced after the refrigerant passes through the primary expansion valve 5 (refrigerant temperature T4). The refrigerant with the reduced pressure and low temperature is discharged from the primary side 2 (refrigerant temperature T5), passes through a second expansion valve 6 (refrigerant temperature T6) and is introduced to the secondary side 3. The pressure of the refrigerant is further reduced to be lower than in the state of the primary side 2 when the refrigerant is introduced to the secondary side 3, and the refrigerant is discharged at a further lower temperature (refrigerant temperature T7). In the two-stage pressure reduction subcooler 1, refrigerants in the primary side 2 and the secondary side 3 cool each other to thereby be supercooled liquid of a lower temperature.
Here, the temperature relationship of the refrigerant will be explained by using an inequality. The above T3 becomes the low temperature T4 after passing through the primary expansion valve 5, and the refrigerant is changed toward the lower temperature and lower pressure by evaporating a high-temperature condensed refrigerant liquid by the primary expansion valve 5. That is, T4 becomes lower in temperature than T3. The refrigerant in T4 is introduced to the primary side 2 to be Ta (T4=Ta). The evaporation does not occur in Ta as there is not a heat source of evaporation (heat source at a higher temperature than Ta). After the cycle proceeds, Ta becomes lower in temperature than T4 later. The refrigerant releases heat to the secondary side 3 at the time of passing through the primary side 2, and cooling and condensation proceed. At this time, the refrigerant on the secondary side 3 becomes Tb.
Heat exchange is performed between the refrigerant Ta on the primary side 2 and the refrigerant on the secondary side 3 by a piece of heat transfer plate 4. The refrigerant T5 discharged from the primary side 2 is a vapor-liquid two phase refrigerant having a lower temperature than the refrigerant T3 discharged from the condenser, that is, T5 is lower in temperature than T3. The refrigerant T5 passes through the secondary expansion valve 6 to be the refrigerant T6 having a further lower temperature, that is, T6 is lower in temperature than T5.
The refrigerant T6 is introduced to the secondary side 3 to be Tb. T6=Tb. As the cycle proceeds, the heat exchange is performed in a mutually complementary form while the refrigerant passes through the primary side 2 and the secondary side 3 in the two-stage pressure reduction subcooler 1 in which T6≧Tb, as a result, temperature change occurs. The refrigerant Ta on the primary side 2 obtains the heat source of condensation (low temperature) as the refrigerant Tb on the secondary side 3 is low in temperature. That is, Tb is lower than Ta.
The refrigerant Ta on the primary side 2 is not evaporated to be a condensed liquid as the refrigerant obtains the heat source of condensation (lower temperature than Ta) from the refrigerant Tb on the secondary side 3, which increases the latent heat of condensation and also increases the latent heat of evaporation in correlation with the increase in the latent heat of condensation. The refrigerant Ta on the primary side 2 is cooled to be a temperature lower than the refrigerant Tb on the secondary side 3, and the temperature of T5 is also reduced in correlation with the reduction of Ta. T6=Tb also becomes lower in temperature in correlation with the above, and Ta performing heat exchange with Tb becomes further lower in temperature, which allows the condensation liquefaction to further proceed.
In the above heat relationship, T7 is lower than Tb, Tb is lower than or equivalent to T6, T6 is lower than T5, T5 is lower than Ta, Ta is lower than T4 and T4 is lower than T3.
The refrigerant Tb on the secondary side 3 is in the state of the condensed liquid. Though the refrigerant Tb on the secondary side 3 is slightly evaporated, the refrigerant Tb maintains the supercooling as there is no latent heat of evaporation (heat in lower temperature than Tb) acquired from the refrigerant Ta on the primary side 2. The refrigerant T7 discharged after the refrigerant Tb on the secondary side 3 is evaporated becomes the lowest temperature due to the slightly remaining heat source of evaporation of the refrigerant Ta on the primary side 2.
In the secondary side 3, the refrigerant T5 which has been cooled and has become the condensed liquid on the primary side 2 is not evaporated as the heat source of evaporation is in short supply in the refrigerant Ta on the primary side 2 even after passing through the secondary expansion valve 6, promoting and maintaining the supercooling to be the supercooled liquid of 100% with the low temperature and low pressure, which increases the latent heat of evaporation and also increases the latent heat of condensation in correlation with the increase.
Moreover, as the outer surface of the two-stage pressure reduction subcooler 1 is covered by the heat insulating material 8 except portions of the introducing ports and the discharging ports of the refrigerant, the heat releasing from the two-stage pressure reduction subcooler 1 or the heat absorption from the outside are suppressed in an extremely slight amount of heat, and the energy is transferred only between the refrigerants on the primary side 2 and the secondary side 3.
The refrigerant passing through the primary side 2 increases the latent heat of condensation by the refrigerant on the secondary side 3 and increases the latent heat of evaporation at the same time in correlation with the increase in the latent heat of condensation, therefore, the primary side 2 can be regarded as a preparation chamber for reducing the temperature of the refrigerant liquid supplied to the secondary side 3.
As the refrigerants perform heat exchange to each other at the time of passing through the primary side 2 and the secondary side 3 and change over time, the refrigerant reduces the pressure in an analog manner while passing through the two-stage pressure reduction subcooler 1 to be the supercooled liquid in a low temperature to a point on a saturation liquid line in a P-h diagram (a hatched portion with chain lines in the P-h diagram), and the latent heat of condensation is increased at the same time and the latent heat of evaporation is also increased in correlation with the increase. In FIG. 3, 11 denotes a refrigerant absorbed by a compressor, 12 denotes a refrigerant introduced to the condenser, 13 denotes an introduction to the primary expansion valve 5, 14 denotes an introduction to the secondary expansion valve 6, 15 denotes an introduction to the expansion valve 7 and 16 denotes an introduction to the evaporator after passing through the expansion valve 7, and further, Δh1 denotes a latent heat of condensation which has become low temperature by reducing the pressure in one stage and has been increased after being cooled by the refrigerant on the secondary side, Δh2 denotes a latent heat of condensation which has become low temperature by reducing the pressure in two stages and has been increased after being cooled by the refrigerant on the primary side, Δh3 denotes a latent heat of evaporation and a latent heat of condensation which have been increased by the two-stage pressure reduction subcooler 1, Δhh denotes the overall latent heat increased by the two-stage pressure reduction subcooler 1 and Δhc denotes the overall latent heat of evaporation increased by the two-stage pressure reduction subcooler 1.
Next, a performance of a related-art circuit is compared with a performance of a circuit incorporating the two-stage pressure reduction subcooler 1 with reference to T-s diagrams (FIG. 4 and FIG. 5). In FIG. 4 which shows the related art, 21 denotes a refrigerant absorbed by a compressor, 22 denotes a state of the refrigerant discharged from the compressor, 23 denotes the refrigerant at a condenser exit, 24 denotes the refrigerant at an expansion valve entrance, 25 denotes the refrigerant at an evaporator entrance and 26 denotes the refrigerant at an evaporator exit.
FIG. 5 shows a refrigerant circuit incorporating the two-stage pressure reduction subcooler 1, which will be compared with FIG. 4. In FIG. 5, 31 denotes a refrigerant absorbed by a compressor, 32 denotes a state of the refrigerant discharged from the compressor, 33 denotes the refrigerant at the entrance of the primary expansion valve 5, 34 denotes the refrigerant at the entrance of the secondary expansion valve 6, 35 denotes the refrigerant at an entrance of the expansion valve 7 and 36 denotes the refrigerant at an entrance to the evaporator after passing through the expansion valve 7. In FIG. 5, ΔS3 denotes the latent heat of condensation and ΔS4 denotes the latent heat of evaporation, which indicate that both heats are apparently increased. 07 denotes the temperature of the discharged refrigerant, which indicates that the temperature is also increased.
Subsequently, circuits incorporating the two-stage pressure reduction subcooler 1 according to the present invention will be explained with reference to FIG. 7 and FIG. 8. FIG. 7 shows a specific circuit used at the time of refrigerating and cooling, in which a system shown by chain lines is a circuit used at the time of heating and defrosting. In the circuit, 40 denotes a compressor, and the refrigerant discharged from the compressor 40 is introduced to a condenser 41. The refrigerant in the uncondensed state which has passed through the condenser 41 passes through the subcooler 1 having the above structure and performing the above operation, passes through the expansion valve 7 and passes through a room apparatus 42 (a radiator as an evaporator) to perform operation of releasing cool air in the room, then, returns to the compressor 40. As the above circulation is performed, the pressure reducing operation of three stages in total is performed by passing through the primary expansion valve 5, the secondary expansion valve 6 and the expansion valve 7 in the circuit.
In FIG. 8, a system shown by solid lines is a circuit used at the time of heating and defrosting. In the case of the circuit, the flow path of the refrigerant discharged by the compressor 40 is switched by a switching valve and the refrigerant flows into a hot gas pipe 43. The refrigerant in high temperature and high pressure which has passed through the hot gas pipe 43 allows the room apparatus 42 to be operated as the condenser in this case to thereby release warm air in the room. The flow path of the refrigerant which has passed through the room apparatus 42 to return to the compressor 40 is switched by a switching valve, and the refrigerant is introduced to a second subcooler 1 a of a hot gas defrost unit 44. The second subcooler 1 a is also provided with a primary expansion valve 5 a and a secondary expansion valve 6 a respectively at introducing ports on a primary side 2 a and a secondary side 3 a. However, in this case, a bypass 45 may be provided in the primary expansion valve 5 a on the primary side 2 a to thereby skip the primary expansion valve 5 a, in which the equivalent advantages to the system of Japanese Patent No. 4398687 vested by the present applicant can be obtained.
The refrigerant which has passed through the second subcooler 1 a in the hot gas unit 44 passes through an expansion valve 7 a in the hot gas unit 44 and passes through an evaporator 42 a, then, returns to the compressor 40. The circulation is performed in this cycle.
In FIG. 6, a rotating-permanent magnet induction heater 51 is incorporated between the room apparatus 42 and the compressor 40 to which the refrigerant is returned. The rotating-permanent magnet induction heater 51 in FIG. 6 uses a motor 52 as a drive source.
The rotating-permanent magnet induction heater 51 is used for compensating for inefficiency in utilization of outside air heat particularly in cold regions to thereby generate perfect heating. Therefore, the rotating-permanent magnet induction heater 51 driven by the general-purpose motor 52 is built in the piping of the refrigerant in the stage after passing through the room apparatus 42 and before being absorbed to the compressor 40, thereby directly heating the refrigerant gas in low pressure.
In the rotating-permanent magnet induction heater 51, Joule heat is generated in an electric conductor due to the flow of electric current or at the time of changing an magnetic field near the electric conductor and the temperature is increased. When permanent magnets are attached so that S-pole and N-pole are alternated with each other on a rotary table rotated by the motor 52, and rotated in a state of being arranged in parallel to the electric conductor, the electric conductor functions as a heating element and the passing refrigerant can be heated, therefore, the refrigerant is not returned to the compressor 40 in the supercooled state.
As can be seen by the above explanation of respective circuits, the refrigeration system according to the present invention has a structure of circulating in five stages of compression, condensation, supercooling, expansion and evaporation. It is further easier to obtain low temperature as compared with the pressure reduction only by the expansion valve as in the related art, and the operation in the heating and defrosting circuit which is evaporated to the outside air allows the acquisition of the heat source of evaporation close to the outside temperature to be easy, therefore, the refrigeration system has excellent operation for low temperature in cold regions.

Claims

What is claimed is:

1. A vapor compression refrigeration system comprising a subcooler incorporated between a condenser and an evaporator, which is formed by a heat exchanger integrally having a primary side and a secondary side into which a refrigerant which has passed through the primary side flows and in which the primary side and the secondary side have the same heat transfer area and capacity, an expansion valve provided at a refrigerant entrance on the secondary side of the subcooler, and a primary expansion valve also provided at a refrigerant entrance on the primary side of the subcooler to which the refrigerant is introduced in a vapor compression refrigeration cycle having stages of compression, condensation, expansion and evaporation of the refrigerant, the system including;

a bypass in the primary expansion valve at the refrigerant entrance on the primary side.

2. The vapor compression refrigeration system according to claim 1,

wherein a rotating-permanent magnet induction heater (magnet heater) is interposed between an evaporator to which the refrigerant is introduced from a refrigerant exit on the secondary side of the subcooler and a compressor to which the refrigerant is returned.

3. The vapor compression refrigeration system according to claim 1,

wherein, in the subcooler, the primary side is a supercooled liquid generating unit and the secondary side is a low-temperature unit for cooling the primary side, and

a temperature of the refrigerant which has passed through the secondary side is lower than a temperature of the refrigerant which has passed through the primary side.

4. The vapor compression refrigeration system according to claim 1,

wherein the subcooler has a structure in which an outer surface thereof is covered by a heat insulating material to prevent heat releasing and heat absorbing.

5. The vapor compression refrigeration system according to claim 4,

wherein cellular material-type urethane foam is used as the heat insulating material.

6. The vapor compression refrigeration system according to claim 1,

wherein a refrigerant circuit incorporating the two subcoolers is formed for cooling and refrigerating as well as heating and defrosting.