JPH07190517A - Refrigeration cycle - Google Patents

Abstract

PURPOSE:To increase the amount of refrigerant circulation and ensure a required freezing capability by employing as a refrigerant an HFC refrigerant that has a higher boiling point than HCFC or has a greater gas ratio volume and setting standard operation frequency of a compressor to be 1, 1 to 2 times that upon the use of the HCFC. CONSTITUTION:Use of HFC, as a refrigerant, that has a higher boiling point or a greater gas ratio volume than HCFC(dichlorofluoromethane) or CFC (chlorofluorocarbon) ensures expansion of a standard operation frequency region of a compressor because of the temperature rise of the compressor being smaller. For this, HFC is used as a refrigerant to operate the compressor with its operation frequency set to be 1.1 to 2 times than upon the use of a conventional refrigerant(HCFC). Hereby, the identical freezing capability as the conventional one is ensured and the load to replace a refrigerant is reduced only with reduced alteration of the structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refrigeration cycle used for an air conditioner and the like, and more particularly to a refrigeration cycle using HFC refrigerant.

[0002]

2. Description of the Related Art Generally, in a refrigeration cycle used for an air conditioner or the like, a compressor, a condenser, an expansion valve and an evaporator are connected by pipes, and a refrigerant is circulated between these devices. Conventionally, CFC has been used as a refrigerant circulating in a refrigeration cycle.
(Chlorofluorocarbon) or HCFC (hydrochlorofluorocarbon) is used, which has been a cause of ozone layer depletion. Therefore, in recent years, replacement of HFC (hydrofluorocarbon) refrigerant has been promoted as a refrigerant that does not cause ozone layer destruction.

[0003]

[Problems to be Solved by the Invention] However, HFC
Since the refrigerant has a high boiling point or a large gas specific volume or a low boiling point or a gas specific volume smaller than that of the CFC or HCFC refrigerant, the refrigeration cycle of the CFC or HCFC refrigerant as it is results in a reduced refrigerating capacity. . In particular, with HFC refrigerants having a large gas specific volume, the pressure loss associated with evaporation in the evaporator increases and refrigerant circulation is hindered, so that the conventional level of refrigerating capacity cannot be maintained, and the gas specific volume is small. In the case of HFC refrigerant, if a compressor having the same excluded volume as the conventional one is used, the input loss becomes large and the efficiency is lowered, so that the refrigeration cycle becomes larger than necessary, leading to an increase in the size of the product and eventually an increase in the cost.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a refrigeration cycle capable of obtaining the same refrigerating capacity as when using a CFC or HCFC refrigerant even when using an HFC refrigerant. To do.

[0005]

In order to achieve the above object, the present invention provides a refrigeration cycle in which a compressor, a condenser, an expansion valve, an evaporator and the like are connected by piping to circulate a refrigerant.
An HFC refrigerant having a higher boiling point or a larger gas specific volume than CFC or HCFC is used as the refrigerant, and the standard operating frequency of the compressor is set to 1.1 to 2 times that of the CFC or HCFC.

Here, the operating frequency of the compressor may be the same as the conventional one, and the displacement of the compressor may be set in the range of 14 to 30 cc / rev.

When an HFC refrigerant having a lower boiling point or a smaller gas specific volume than CFC or HCFC is used as the refrigerant circulating in the refrigeration cycle, the displacement capacity of the compressor is set within the range of 5 to 20 cc / rev. It is preferable.

Further, according to the present invention, the diameter of the pipe constituting the refrigeration cycle is set to 1 of the required gas volume flow rate of the HFC refrigerant used.
It is set in the range of 2 to 8 times the square.

[0009]

[Function] As a refrigerant circulating in the refrigeration cycle, CFC
Alternatively, when an HFC refrigerant having a higher boiling point or a larger gas specific volume than HCFC is used, if the standard operating frequency of the compressor forming the refrigeration cycle is increased and the refrigerant circulation amount is increased, the gas specific volume is large and the latent heat amount is small. The required refrigerating capacity can be secured even by using. In particular, if the standard operating frequency of the compressor is 1.1 to 2 times higher than that when using CFC or HCFC, CFC or HCF
The same refrigerating capacity as when C is used can be obtained.
In this case, when the standard operating frequency of the compressor exceeds twice as high as when the CFC or HCFC is used, deterioration of lubricating oil and sliding parts in the compressor becomes severe. On the other hand, if it is less than 1.1 times, the refrigerant does not circulate well and it is not possible to secure the capacity.

Instead of increasing the operating frequency of the compressor as described above, the excluded capacity of the compressor is 1.1 to 2 times (14 to
By setting the flow rate to 30 cc / rev), the refrigerant circulation amount can be increased to obtain the required refrigerating capacity. In this case, since the compressor can be operated at the same operating frequency as the conventional one, that is, a highly efficient frequency, it is possible to suppress power consumption to a low level.

As a refrigerant in the refrigeration cycle, CF is used.
When an HFC refrigerant having a lower boiling point or a smaller gas specific volume than C or HCFC is used, conversely to the above, the required refrigerating capacity can be secured by making the displacement of the compressor lower than in the conventional case. In this case, the excluded capacity of the compressor is determined in consideration of the latent heat amount and the gas specific volume of the HFC refrigerant used, but in most cases, it may be set in the range of 5 to 30 cc / rev.

Further, the diameter of the piping that constitutes the refrigeration cycle is
2 to the power of 1/2 of the required gas volume flow rate of the HFC refrigerant used
If set in the range of up to 8 times, even if an HFC refrigerant having a large or small gas specific volume is used, the required minimum size is
The refrigeration capacity of the conventional level can be maintained.

[0013]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 5 is a diagram showing a refrigeration cycle used in an air conditioner. The refrigeration cycle 1 is configured by connecting a compressor 2, an outdoor heat exchanger 3, an expansion valve 4 and an indoor heat exchanger 5 in sequence with a pipe 6. 7 is a four-way valve for switching between cooling and heating operation. During the cooling operation, the refrigerant gas compressed by the compressor 2 passes through the four-way valve 7 and is guided to the outdoor heat exchanger 3, where it is condensed and releases latent heat. The refrigerant condensed in the outdoor heat exchanger 3 passes through the expansion valve 4 and is guided to the indoor heat exchanger 5, where the indoor heat is received and evaporated, and the heat is accumulated as latent heat. Then, the refrigerant that has undergone a gas phase change in the indoor heat exchanger 5 is returned to the suction side of the compressor 2 through the four-way valve 7.

By the way, the refrigeration cycle 1 as described above
In place of conventional CFCs or HCFCs as refrigerants, HFCs having a higher boiling point and a larger gas specific volume than these are used.
If a refrigerant is used, the refrigerating capacity of the refrigerating cycle 1 will be lower than the conventional level. Therefore, in this embodiment, the standard operating frequency of the compressor 2 is increased to increase the refrigerant circulation amount, and an air conditioner having the same capacity as when using a CFC or HCFC refrigerant is realized.

FIG. 1 is a graph showing the temperature change on the surface of the compressor 2 with respect to the standard operating frequency of the compressor 2.
Chlorodifluoromethane (HCFC) as a conventional refrigerant
Is used as the refrigerant of this embodiment, 1, 1, 1, 2
-Each characteristic when using tetrafluoroethane (HFC) is shown. As is clear from the graph, in chlorodifluoromethane (HCFC), the temperature rise with respect to the operating frequency UP of the compressor 2 is large due to the boiling point, and the deterioration of the lubricating oil and sliding parts inside the machine becomes severe. There is a limit to the rise. In the graph, the limit is 50 to 80 Hz during standard operation (in the optimum normal temperature range).
On the other hand, when 1,1,1,2-tetrafluoroethane is used as the new refrigerant, the standard operating frequency range of the compressor 2 can be expanded because the temperature rise of the compressor 2 is small. The graph shows that the operating frequency range can be expanded to 80 to 130 Hz during standard operation.

Therefore, 1,1,1,2-tetrafluoroethane is used as the refrigerant, and the operating frequency of the compressor 2 is about 1.6 times that of the conventional refrigerant (chlorodifluoromethane).
When operated at (50Hz → 80Hz), the same refrigeration capacity of 2.5 when using chlorodifluoromethane
It was possible to obtain the equivalent of kw. The excluded volume of the compressor 2 is the same as when using chlorodifluoromethane, which is 14 to 20.
cc / rev

As described above, according to this embodiment, by increasing the standard operating frequency of the compressor 2, the refrigerant circulation amount in the refrigeration cycle 1 can be increased, the latent heat amount is small, and the gas specific volume is large. Even in this case, it is possible to obtain the same refrigerating capacity as in the case of using the conventional CFC or HCFC refrigerant. Further, according to the present embodiment, since it is only necessary to increase the standard operating frequency of the compressor 2, it is possible to use the HFC refrigerant by making very few structural changes to the refrigeration cycle for the CFC or HCFC refrigerant. As a result, the load accompanying the replacement of the refrigerant can be reduced.

Next, a second embodiment of the present invention will be described.

In the above-described embodiment, the operating frequency of the compressor 2 is increased to increase the refrigerant circulation amount in the refrigeration cycle 1. However, in this embodiment, the displacement volume of the compressor 2 is increased and the refrigerant circulation is increased. The amount is increasing. That is, if chlorodifluoromethane (HCFC), which is a conventional refrigerant, is used, there is a limit to the increase in the excluded volume from the viewpoint of compressor efficiency, but if 1,1,1,2-tetrafluoroethane is used as the new refrigerant, Therefore, the excluded volume of the compressor 2 can be dramatically increased.

Therefore, 1,1,1,2-tetrafluoroethane is used as the refrigerant, and the displacement volume of the compressor 2 is about 1.6 times (3) that of the conventional refrigerant (chlorodifluoromethane).
0cc / rev), the operating frequency of the compressor 2 was the same, and the refrigerating capacity was 2.5kw, which is the same as when the conventional refrigerant was used.
And the power consumption could be obtained.

In this way, if the displacement volume of the compressor 2 is increased, the refrigerant circulation amount in the refrigeration cycle 1 can be increased,
Even with an HFC refrigerant having a small amount of latent heat and a large gas specific volume, it is possible to obtain the same refrigerating capacity as when using a conventional CFC or HCFC refrigerant. Moreover, if the compression mechanism portion of the compressor 2 is modified by increasing the volume of the cylinder and the motor portion is left as it is, as shown in FIG.
The compressor motor can be operated in a highly efficient frequency range, power consumption can be kept low, and high operation efficiency can be obtained.

Next, a third embodiment of the present invention will be described.

In the above embodiment, it was explained that an HFC refrigerant having a higher boiling point or a larger gas specific volume than that of chlorodifluoromethane which is a conventional refrigerant is used. However, in this embodiment, conversely, a low boiling point or a gas specific volume is used. A small HFC refrigerant, for example, a mixed refrigerant of difluoromethane and pentafluoroethane is used. When such a mixed refrigerant is used, contrary to the above, the excluded volume of the compressor 2 is reduced. The excluded volume of the compressor 2 at this time is determined based on the latent heat amount of the refrigerant to be used and the gas specific volume. When the mixed refrigerant is used, it is about 0.7 times as large as that of chlorodifluoromethane. To do.

Therefore, a mixed refrigerant of difluoromethane and pentafluoroethane is used as the refrigerant, and the displacement capacity of the compressor 2 is 0.7 times (5 times that when chlorodifluoromethane is used).
.About.20 cc / rev) and operating at the same operating frequency of the compressor 2, a refrigerating capacity equivalent to 2.5 kw and power consumption equivalent to those using chlorodifluoromethane could be obtained.

As described above, by setting the displacement volume of the compressor to be smaller than that when the conventional refrigerant is used, even if an HFC refrigerant having a gas specific volume smaller than that of the conventional refrigerant is used, the same refrigerating capacity as before can be obtained. it can. Moreover, if only the compression mechanism part of the compressor is modified to reduce the excluded volume and the motor part has the conventional structure, as shown in FIG. 2, the compressor motor can be operated in a highly efficient region and power consumption can be reduced. Keep it low,
High operating efficiency can also be obtained.

Next, a fourth embodiment of the present invention will be described.

Using 1,1,1,2-tetrafluoroethane as the HFC refrigerant, the refrigerating capacity of 2.5, which is equivalent to the conventional one, is used.
When realizing an air conditioner of kW, when the refrigerant having a large gas specific volume passes through the refrigeration cycle, particularly when passing through the evaporator,
Since the pressure loss on the gasified outlet side increases with the phase change, the refrigerant circulation is hindered and the refrigeration efficiency is significantly reduced. Further, when a mixture of difluoromethane and pentafluoroethane is used as an HFC refrigerant to realize an air conditioner with a refrigerating capacity of 2.5 kw, which is the conventional equivalent, the above-mentioned mixed refrigerant having a small gas specific volume is evaporated particularly in the refrigeration cycle. When passing through the refrigerator, the pressure loss on the outlet side gasified with the phase change decreases, so that the refrigeration cycle can be downsized.

That is, as shown in FIG.
Since the pressure loss difference between 1,2-tetrafluoroethane at the inlet and outlet of the evaporator is larger than the pressure loss difference at the inlet and outlet of chlorodifluoromethane, which is a conventional refrigerant, when trying to maintain refrigeration efficiency, The low pressure side pipe diameter between the outlet side and the suction side of the compressor must be increased.
On the other hand, the pressure loss difference at the evaporator inlet and outlet of the mixed refrigerant is
Since it is smaller than the pressure loss difference at the evaporator inlet / outlet of chlorodifluoromethane, it is possible to reduce the pipe diameter on the low pressure side.

Therefore, as a result of testing the HFC refrigerants having different physical properties, the inventors of the present invention have found that as shown in FIG. 4, the optimum pipe diameter range (the required gas volume flow rate of the refrigerant is 1
/ 2 to 8 times). Therefore, by setting the diameter of the pipe 6 constituting the refrigeration cycle 1 within the range of FIG. 4, it is possible to obtain the same capacity and efficiency as the conventional refrigeration cycle without increasing the refrigeration cycle 1 itself. .

[0031]

In summary, according to the present invention, the following excellent effects are exhibited.

(1) According to claim 1, CFC or H
Even if a refrigerant having a higher boiling point or a larger gas specific volume than the CFC refrigerant is used, the same refrigerating capacity as that of the conventional refrigerating cycle can be obtained.

(2) According to claim 2, CFC or H
Even if a refrigerant having a higher boiling point or a larger gas specific volume than that of the CFC refrigerant is used, the same refrigerating capacity as that of the conventional refrigerating cycle can be obtained, and high operating efficiency can be obtained.

(3) According to claim 3, CFC or H
Even if a refrigerant having a lower boiling point or a smaller gas specific volume than the CFC refrigerant is used, the same refrigerating capacity as that of the conventional refrigerating cycle can be obtained.

(4) According to claim 4, CFC or H
Even if various refrigerants having a gas specific volume larger or smaller than that of the CFC refrigerant are used, the required refrigerating capacity can be obtained with a structure of an appropriate size without increasing the size.

[Brief description of drawings]

FIG. 1 is a graph showing a temperature change on a compressor surface with respect to a compressor operating frequency.

FIG. 2 is a graph showing a change in compressor motor efficiency with respect to a compressor operating frequency.

FIG. 3 is a graph showing pressure loss at an evaporator inlet / outlet during a refrigeration cycle.

FIG. 4 is a diagram showing an optimum pipe diameter range for use with a refrigerant.

FIG. 5 is a diagram showing a configuration example of a refrigeration cycle.

[Explanation of symbols]

 1 Refrigeration cycle 2 Compressor 3 Outdoor heat exchanger 4 Expansion valve 5 Indoor heat exchanger 6 Piping

Claims (4)

[Claims] 1. A refrigeration cycle in which a compressor, a condenser, an expansion valve, an evaporator, and the like are connected by pipes to circulate a refrigerant, and an HFC refrigerant having a higher boiling point or a larger gas specific volume than CFC or HCFC is used as the refrigerant. , The standard operating frequency of the compressor is CFC or HC
A refrigeration cycle characterized by being set to 1.1 to 2 times that when using FC. 2. A refrigeration cycle in which a refrigerant is circulated by connecting a compressor, a condenser, an expansion valve, an evaporator and the like with piping, and an HFC refrigerant having a higher boiling point or a larger gas specific volume than CFC or HCFC is used as the refrigerant. A refrigeration cycle in which the displacement of the compressor is set in the range of 14 to 30 cc / rev. 3. A HFC refrigerant having a lower boiling point or a smaller gas specific volume than CFC or HCFC is used as the refrigerant in a refrigeration cycle in which a refrigerant is circulated by connecting a compressor, a condenser, an expansion valve, an evaporator and the like with pipes. In addition, a refrigeration cycle characterized in that the displacement capacity of the compressor is set in the range of 5 to 20 cc / rev. 4. A refrigeration cycle in which a refrigerant is circulated by connecting a compressor, a condenser, an expansion valve, an evaporator and the like with piping, and the diameter of the piping is 1/2 of the required gas volumetric flow rate of the refrigerant.
A refrigerating cycle characterized by being set in a range of 2 to 8 times the power of 2.