JP2005351590A - Cooling/warming system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling/warming system for minimizing the amount of hydrocarbon refrigerant to be used for particularly warming up to 50-100°C. <P>SOLUTION: The cooling/warming system for cooling or warming goods such as canned drinks uses a low pressure shell compressor 20, refrigerant R600a, and a mineral oil or ester oil as lubricating oil for the compressor which has lower cost, generally working results and a kinetic viscosity of 3-30 mm<SP>2</SP>/s at 40°C. The low pressure shell compressor 20 is encircled by a cover 21. When using a sensor 22 for measuring ambient temperature around the low pressure shell compressor 20, when its value is smaller than a preset value, a heater 23 is energized to keep the temperature of the lubricating oil to be 40-80°C during warming, thus minimizing the amount of the refrigerant to be used. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention uses a latent heat generated when a refrigerant compressed by a compressor condenses in a vending machine or a showcase that sells products such as canned beverages heated or cooled for cooling and heating. The present invention relates to a cooling and heating system to be performed.

  In recent years, there has been an increasing demand for reducing power consumption for refrigeration and warming equipment such as vending machines and showcases. As a means to reduce power consumption when heating by a heater, it is the same as for air conditioning and air conditioning systems. In addition, a cooling system that uses a heat pump for heating is proposed. In addition, when a hydrocarbon refrigerant, which is a natural refrigerant with a low global warming potential, is used, it is important to suppress the amount of refrigerant dissolved in the lubricating oil of the compressor in order to increase safety at the time of refrigerant leakage. In particular, when the cooling system is switched to a heat pump and used for heating, it is necessary to devise a method in which the amount of refrigerant dissolved in the lubricating oil of the compressor does not change greatly between cooling and heating. When the refrigerant dissolution amount changes greatly, it becomes necessary to always store the liquid refrigerant in order to maintain the optimum refrigerant quantity, resulting in an increase in the refrigerant usage.

  Conventionally, a configuration in which the temperature of the lubricating oil in the compressor is maintained at a certain level or higher by heating the compressor with a heater (see, for example, Patent Document 1) or a special lubricating oil in which the amount of dissolved hydrocarbon refrigerant is relatively small. A configuration to be used (for example, see Patent Document 2) has been proposed. Here, a general mineral oil-based lubricating oil is used in a refrigerator using a hydrocarbon refrigerant. However, since the low-pressure shell compressor is used only at a low evaporation temperature, the amount of refrigerant dissolved in the lubricating oil is small and does not cause a big problem. . The amount of refrigerant dissolved in the lubricating oil of the compressor becomes a problem in the case of a cooling system using a heat pump or a high-pressure shell type compressor having a relatively high evaporation temperature.

  Hereinafter, a conventional cooling and heating system will be described with reference to the drawings.

  FIG. 6 is a refrigerant circuit diagram of a conventional cooling and heating system.

  As shown in FIG. 6, the conventional cooling and heating system uses propane or isobutane which is a hydrocarbon refrigerant, and also includes a high-pressure shell compressor 1, a four-way valve 2, an accumulator 3, an outdoor heat exchanger 4, and an indoor heat exchanger. When the room is cooled, the refrigerant discharged from the high-pressure shell compressor 1 is switched by the four-way valve 2 and supplied from the outdoor heat exchanger 4 to the indoor heat exchanger 5, and again The refrigerant flows from the accumulator 3 to the high-pressure shell compressor 1 through the four-way valve 2, and when heating the room, the refrigerant discharged from the high-pressure shell compressor 1 is switched by the four-way valve 2 to exchange the heat in the room. The heat is supplied from the vessel 5 to the outdoor heat exchanger 4, and is returned to the high pressure shell type compressor 1 from the accumulator 3 through the four-way valve 2 again.

  Here, in general, the indoor heat exchanger 5 is installed in a heat insulating space (not shown, hereinafter referred to as a storage chamber) in which an object to be cooled and heated such as a can beverage is stored, and the high-pressure shell compressor 1, The four-way valve 2, the accumulator 3, and the outdoor heat exchanger 4 are disposed outside the heat insulating space.

  The piping connecting the outdoor heat exchanger 4 and the indoor heat exchanger 5 includes a heating capillary tube 6, a cooling check valve 7, a cooling capillary tube 8, a heating check valve 9 and a dryer 10. It is connected. Here, the heating capillary tube 6 and the cooling check valve 7, and the cooling capillary tube 8 and the heating check valve 9 are respectively connected in parallel, and the heating capillary tube 6 and the cooling capillary are connected. A dryer 10 is connected to a position sandwiched between the tubes 8. In general, the outdoor heat exchanger 4 and the indoor heat exchanger 5 are blown as necessary by independent blow fans (not shown), and air cooling and heat exchange are promoted.

  Here, the outlet pipe of the high-pressure shell compressor 1 has a sensor 11 for measuring the temperature of the discharge gas, the lower surface of the high-pressure shell compressor 1 has a heater 12 for heating the lower surface of the shell, and the high-pressure shell compressor. 1 is provided with a fan 13 for air cooling.

  The operation of the conventional cold / warm switching system configured as described above will be described below.

  When the storage chamber is cooled, the refrigerant discharged from the high-pressure shell compressor 1 is switched to a flow path by the four-way valve 2 and supplied to the outdoor heat exchanger 4 to be condensed and liquefied. The liquid refrigerant discharged from the outdoor heat exchanger 4 is supplied to the dryer 10 through the cooling check valve 7. The liquid refrigerant discharged from the dryer 10 is depressurized by the cooling capillary tube 8 and supplied to the indoor heat exchanger 5 to evaporate, and the gas refrigerant passes through the four-way valve 2 and again from the accumulator 3 to the high-pressure shell compressor 1. To reflux.

  When the storage chamber is heated, the refrigerant discharged from the high-pressure shell compressor 1 is switched to a flow path by the four-way valve 2 and supplied to the indoor heat exchanger 5 to be condensed and liquefied. The liquid refrigerant discharged from the indoor heat exchanger 5 is supplied to the dryer 10 through the heating check valve 9. The liquid refrigerant discharged from the dryer 10 is depressurized by the heating capillary tube 6 and supplied to the outdoor heat exchanger 4 to evaporate, and the gas refrigerant again passes from the accumulator 3 through the four-way valve 2 to the high pressure shell type compressor. Reflux to 1.

  Here, when the high-pressure shell type compressor 1 is used, the mineral oil-based lubricating oil stored inside the high-pressure shell type compressor 1 is exposed to the hydrocarbon refrigerant at the condensation pressure to dissolve the hydrocarbon refrigerant. Generally, it is known that a large amount of hydrocarbon refrigerant is dissolved when the temperature of the mineral oil-based lubricating oil is low. Therefore, the indication value of the sensor 11 is always monitored, and when it is lower than the predetermined value, the heater 12 is energized. And the temperature of the lubricating oil stored in the inside is kept substantially constant and high.

Thus, by using the heater 12 and the fan 13, the amount of refrigerant in the lubricating oil can be kept small and substantially constant by keeping the temperature of the high-pressure shell compressor 1 substantially constant and high, and the amount of refrigerant used can be reduced. Increase can be prevented.
JP 2000-283621 A JP 2001-234184 A

  However, the above conventional configuration assumes a relatively low condensation temperature of about 30 to 40 ° C. such as an air conditioner heat pump, and when a product such as a can beverage is heated to 50 to 100 ° C., the condensation pressure becomes high, In order to keep the dissolved amount of the hydrocarbon refrigerant low even at a high condensation pressure, the temperature of the mineral oil-based lubricating oil needs to be kept higher. As a result, the heater power necessary for maintaining the high-pressure shell compressor 1 at a high temperature increases, and the amount of heat leaked to the outside during heating increases, resulting in a significant reduction in efficiency. Also, if a higher viscosity lubricant is used to ensure the necessary viscosity for lubrication at a high temperature, the lubricant discharged to the system piping together with the refrigerant will abnormally increase in viscosity and stay in the heat exchanger at the evaporation temperature. However, the risk of secondary problems such as blockage of system piping and lack of lubricating oil in the compressor increases.

  On the other hand, a special lubricating oil with a small amount of dissolved hydrocarbon refrigerant is expensive and is generally difficult to apply because it does not have a sufficient track record.

  The present invention solves the conventional problems, and in particular, when heating a product such as a can beverage to a high temperature of 50 to 100 ° C., cooling heating that can keep the amount of refrigerant dissolved in the lubricating oil substantially constant. A system is proposed to improve efficiency and reliability while reducing the amount of hydrocarbon refrigerant used.

In order to solve the above-mentioned conventional problems, the cooling and heating system of the present invention uses a low-pressure shell compressor, uses R600a as a refrigerant, and is inexpensive and generally used as a lubricating oil for a compressor at 40 ° C. Mineral oil or ester oil having a kinematic viscosity of 3 to 30 mm ² / s is used.

Thus, by keeping the pressure inside the compressor at a low evaporation pressure, the amount of refrigerant dissolved in the lubricating oil can be kept low, and the amount of hydrocarbon refrigerant used can be reduced. At the same time, by using the hydrocarbon refrigerant R600a having a low condensation pressure even under a very high condensation temperature of 50 to 100 ° C., even a lubricating oil having a relatively low viscosity of 3 to 30 mm ² / s at a kinematic viscosity at 40 ° C. Since durability can be maintained, it is possible to eliminate reliability problems such as the retention of lubricating oil in the system path.

  In addition, another cooling and heating system of the present invention uses a low-pressure shell compressor, uses R600a as a refrigerant, surrounds the compressor with a heat insulating material, and keeps the lubricating oil temperature at 40 to 80 ° C. during heating. It is characterized by.

  As a result, the amount of refrigerant dissolved in the lubricating oil is kept low by keeping the pressure inside the compressor at a low evaporating pressure, and the compressor is surrounded by a heat insulating material at the time of heating when the evaporating temperature is higher than that during cooling. By maintaining the temperature at 40 to 80 ° C., it is possible to suppress the difference in the amount of refrigerant dissolved between cooling and heating while suppressing the amount of heat leaking to the outside. As a result, it is not necessary to always store the liquid refrigerant in order to maintain the optimum refrigerant amount, and the minimum refrigerant usage can be maintained.

  The cooling and heating system of the present invention minimizes the amount of refrigerant used, particularly when products such as can drinks are heated to a high temperature of 50 to 100 ° C. by suppressing the amount of refrigerant dissolved in the lubricating oil of the compressor. In addition, the difference in the amount of refrigerant dissolved between cooling and heating can be suppressed, and thus the efficiency and reliability can be improved while suppressing the amount of hydrocarbon refrigerant used.

The invention according to claim 1 of the present invention includes an indoor heat exchanger installed in a room for storing products, an outdoor heat exchanger installed outside a compartment for storing products, an expansion mechanism, and a compressor A cooling and heating system pipe that annularly connects the compressor, the expansion mechanism, the indoor heat exchanger, and the outdoor heat exchanger, and the refrigerant discharged from the compressor from the outdoor heat exchanger. Either circulating the mechanism and the indoor heat exchanger and returning to the compressor, or circulating from the indoor heat exchanger to the expansion mechanism and the outdoor heat exchanger and returning to the compressor The compressor is a low-pressure shell type compressor, R600a is used as a refrigerant, and mineral oil having a kinematic viscosity at 40 ° C. of 3 to 30 mm ² / s is used as the lubricating oil for the compressor. Cold, characterized by the use Because it is warming system, keeping the pressure inside the compressor to the low evaporation pressure suppressing the refrigerant dissolution amount of lubricating oil in, it is possible to reduce the amount of hydrocarbon refrigerant. At the same time, by using the hydrocarbon refrigerant R600a having a low condensation pressure even under a very high condensation temperature of 50 to 100 ° C., even a lubricating oil having a relatively low viscosity of 3 to 30 mm ² / s at a kinematic viscosity at 40 ° C. Since durability can be maintained, it is possible to eliminate reliability problems such as the retention of lubricating oil in the system path.

Invention of Claim 2 of this invention is the indoor heat exchanger installed in the room | chamber interior which accommodates goods, the outdoor heat exchanger installed outside the division which accommodates goods, an expansion mechanism, and a compressor A cooling and heating system pipe that annularly connects the compressor, the expansion mechanism, the indoor heat exchanger, and the outdoor heat exchanger, and the refrigerant discharged from the compressor from the outdoor heat exchanger. Either circulating the mechanism and the indoor heat exchanger and returning to the compressor, or circulating from the indoor heat exchanger to the expansion mechanism and the outdoor heat exchanger and returning to the compressor A four-way selector valve, the compressor being a low-pressure shell compressor, R600a being used as a refrigerant, and an ester oil having a kinematic viscosity at 40 ° C. of 3 to 30 mm ² / s as a lubricating oil for the compressor It is characterized by using Since in that the cooling and warming system, keeping the pressure inside the compressor to the low evaporation pressure suppressing the refrigerant dissolution amount of lubricating oil in, it is possible to reduce the amount of hydrocarbon refrigerant. At the same time, by using the hydrocarbon refrigerant R600a having a low condensation pressure even under a very high condensation temperature of 50 to 100 ° C., even a lubricating oil having a relatively low viscosity of 3 to 30 mm ² / s at a kinematic viscosity at 40 ° C. Since durability can be maintained, it is possible to eliminate reliability problems such as the retention of lubricating oil in the system path. Also, by using ester oil with a large amount of saturated water solubility, the risk of moisture chalk during cooling is eliminated, eliminating the drier in which liquid refrigerant accumulates, and as a result, further reducing the amount of refrigerant used Can do.

  The invention according to claim 3 of the present invention is characterized in that, in the invention according to claim 1 or 2, the compressor is surrounded by a heat insulating material, and the lubricating oil temperature during heating is kept at 40 to 80 ° C. Therefore, while maintaining the pressure inside the compressor at a low evaporating pressure, the amount of refrigerant dissolved in the lubricating oil is kept low, and at the time of heating when the evaporating temperature is higher than that during cooling, the compressor And the lubricating oil temperature is kept at 40 to 80 ° C., so that the difference in the amount of refrigerant dissolved between cooling and heating can be suppressed while suppressing the amount of heat leaking to the outside. As a result, it is not necessary to always store the liquid refrigerant in order to maintain the optimum refrigerant amount, and the minimum refrigerant usage can be maintained.

  The invention according to claim 4 of the present invention is the invention according to any one of claims 1 to 3, further comprising a heater for heating the compressor, wherein the temperature of the compressor is predetermined during heating. Since the cooling and heating system is characterized in that the heater is energized when the value is lower than the value, during the warming when the evaporation temperature is higher than during cooling, the compressor is started and the temperature still rises. By heating with a heater in the meantime, the liquid refrigerant dissolved in the compressor can be quickly supplied into the system to increase the condensation temperature and improve the startup characteristics of the system.

  The invention according to claim 5 of the present invention is the invention according to any one of claims 1 to 4, further comprising a fan for cooling the compressor, wherein the temperature of the compressor becomes a predetermined value during cooling. The cooling and heating system is characterized in that the fan is operated when the temperature exceeds the upper limit. Therefore, the efficiency of the compressor is improved by lowering the temperature of the compressor during cooling when the evaporation temperature is lower than that during heating. Can do.

  Embodiments of a vending machine according to the present invention will be described below with reference to the drawings. In addition, about the same structure as the past, the same code | symbol is attached | subjected and detailed description is abbreviate | omitted.

(Embodiment 1)
FIG. 1 is a refrigerant circuit diagram of the cooling and heating system of the first embodiment. FIG. 2 is a graph showing the characteristics of the amount of refrigerant dissolved in oil of mineral oil A according to the embodiment. FIG. 3 is a diagram showing the characteristics of the oil viscosity of the mineral oil A of the same embodiment. FIG. 4 is a graph showing the characteristics of the amount of refrigerant dissolved in oil of mineral oil B according to the embodiment. FIG. 5 is a diagram showing the characteristics of the oil viscosity of the mineral oil B of the same embodiment.

  As shown in FIG. 1, the cooling and heating system of the present invention uses isobutane, which is a hydrocarbon refrigerant, and also includes a low-pressure shell compressor 20, a four-way valve 2, an accumulator 3, an outdoor heat exchanger 4, and an indoor heat exchanger. When the room is cooled, the refrigerant discharged from the low-pressure shell compressor 20 is switched by the four-way valve 2 and supplied from the outdoor heat exchanger 4 to the indoor heat exchanger 5, and again The refrigerant flows from the accumulator 3 to the low-pressure shell compressor 20 through the four-way valve 2, and when the room is heated, the refrigerant discharged from the low-pressure shell compressor 20 is switched by the four-way valve 2 to exchange the heat in the room. The heat is supplied from the vessel 5 to the outdoor heat exchanger 4, and is returned to the low-pressure shell compressor 20 from the accumulator 3 through the four-way valve 2 again.

  Here, in general, the indoor heat exchanger 5 is installed in a storage room in which an object to be cooled and heated, such as a can drink, is stored, a low-pressure shell compressor 20, a four-way valve 2, an accumulator 3, an outdoor heat exchanger. 4 is arranged outside the storage room.

  The piping connecting the outdoor heat exchanger 4 and the indoor heat exchanger 5 includes a heating capillary tube 6, a cooling check valve 7, a cooling capillary tube 8, a heating check valve 9 and a dryer 10. It is connected. Here, the heating capillary tube 6 and the cooling check valve 7, and the cooling capillary tube 8 and the heating check valve 9 are respectively connected in parallel, and the heating capillary tube 6 and the cooling capillary are connected. A dryer 10 is connected to a position sandwiched between the tubes 8. In general, the outdoor heat exchanger 4 and the indoor heat exchanger 5 are blown as necessary by independent blow fans (not shown), and air cooling and heat exchange are promoted.

  Here, the low-pressure shell compressor 20 is surrounded by a cover 21 made of a heat insulating material, and includes a sensor 22 for measuring the temperature inside the cover 21, a heater 23 for heating the low-pressure shell compressor 20, and the cover 21. A fan 24 for taking in outside air is provided.

  The operation of the cooling and heating system of the present invention configured as described above will be described below.

  When cooling the storage chamber, the refrigerant discharged from the low-pressure shell compressor 20 switches the flow path by the four-way valve 2 and is supplied to the outdoor heat exchanger 4 to be condensed and liquefied. The liquid refrigerant discharged from the outdoor heat exchanger 4 is supplied to the dryer 10 through the cooling check valve 7. The liquid refrigerant discharged from the dryer 10 is depressurized by the cooling capillary tube 8 and supplied to the indoor heat exchanger 5 to evaporate, and the gas refrigerant again passes from the accumulator 3 through the four-way valve 2 to the low pressure shell compressor 20. To reflux.

  Further, when heating the storage chamber, the refrigerant discharged from the low-pressure shell compressor 20 is switched to the flow path by the four-way valve 2 and supplied to the indoor heat exchanger 5 to be condensed and liquefied. The liquid refrigerant discharged from the indoor heat exchanger 5 is supplied to the dryer 10 through the heating check valve 9. The liquid refrigerant discharged from the dryer 10 is depressurized by the heating capillary tube 6 and supplied to the outdoor heat exchanger 4 to evaporate, and the gas refrigerant passes through the four-way valve 2 and again from the accumulator 3 to the low-pressure shell compressor. Reflux to 20.

  Here, with reference to FIG. 2 and FIG. 3, the refrigerant dissolution amount characteristic and the oil viscosity characteristic of the mineral oil A which is the lubricating oil stored in the low pressure shell type compressor 20 will be described below.

  As shown in FIG. 2, the weight% of the refrigerant contained in the mixture of the mineral oil A and the refrigerant (hereinafter referred to as the amount of refrigerant dissolved in oil) represents the temperature of the mineral oil A (hereinafter referred to as the oil temperature) and the inside of the low-pressure shell compressor 20. The refrigerant pressure varies greatly depending on the refrigerant pressure (the value converted into the saturation temperature is hereinafter referred to as the refrigerant saturation temperature). In particular, when the difference between the saturation temperature of the refrigerant and the oil temperature decreases, the amount of refrigerant dissolved in oil tends to increase rapidly. In general, it is known that a combination of a hydrocarbon refrigerant and mineral oil shows a similar tendency. Further, from the viewpoint of suppressing the amount of hydrocarbon refrigerant used, the amount of refrigerant dissolved in oil is preferably 0 to 5% by weight.

As shown in FIG. 3, the kinematic viscosity (hereinafter referred to as oil viscosity) of the mixture of mineral oil A and the refrigerant also varies greatly depending on the oil temperature and the saturation temperature of the refrigerant. The reason why the oil viscosity rapidly decreases as the refrigerant saturation temperature increases at an oil temperature of 40 ° C. is that the amount of refrigerant dissolved in oil increases rapidly. In general, it is known that a combination of a hydrocarbon refrigerant and mineral oil shows a similar tendency. In addition, the oil viscosity is preferably 3 to 10 mm ² / s from the viewpoint of ensuring the durability of the compressor and reducing the loss due to the viscous resistance of the lubricating oil.

  In this embodiment, when the storage room is cooled, the condensation temperature of the outdoor heat exchanger 4 is 20 to 50 ° C., which is slightly higher than the outside air temperature, and the evaporation temperature of the indoor heat exchanger 5 is −30 to 30 when considering freezing to refrigeration. -10 ° C. On the other hand, when heating the storage room, the evaporating temperature of the outdoor heat exchanger 4 is −10 to 10 ° C. equivalent to that of a general heat pump air conditioner, and the condensing temperature of the indoor heat exchanger 5 is a product holding temperature 50 such as a can drink. Considering -60 ° C, the temperature is 50-70 ° C.

  As a result, when cooling the storage chamber, since the saturation temperature of the refrigerant is -30 to -10 ° C, the amount of refrigerant dissolved in oil and the oil viscosity are appropriate within the range where the oil temperature does not exceed 80 ° C. I understand that there is no. Therefore, if the R600a having a low refrigerant pressure is used, the discharge gas temperature can be kept low, so that the low-pressure shell compressor 20 and the oil temperature do not rise significantly, and the fan 24 is driven to the extent that the inside of the cover 21 is ventilated. That's fine.

  When the outside air temperature is low and the condensation temperature is low, the ambient temperature of the low-pressure shell compressor 20 is measured by the sensor 22 because the low-pressure shell compressor 20 and the oil temperature do not rise and there is no need to drive the fan 24. However, it is desirable to drive the fan 24 when the value exceeds a predetermined value.

  On the other hand, when heating the storage chamber, the saturation temperature of the refrigerant is −10 to + 10 ° C., so that the oil temperature needs to be kept at 40 to 80 ° C. or higher in order to appropriately suppress the amount of refrigerant dissolved in oil. I understand. Moreover, since oil viscosity will fall below an appropriate value when it exceeds 80 degreeC, it turns out that oil temperature must be controlled in a narrow range according to evaporation temperature. Therefore, the low-pressure shell compressor 20 is surrounded by a cover 21, and the ambient temperature of the low-pressure shell compressor 20 is measured by the sensor 22, and when the value falls below a predetermined value, the heater 23 is energized so that the low-pressure shell compressor 20 is energized. The oil temperature of the mold compressor 20 is kept at 40 to 80 ° C. or higher. In particular, since the oil temperature is low at the time of starting, it is desirable that the heater 23 is continuously energized to quickly raise the temperature.

  Note that the amount of heat generated by the low-pressure shell compressor 20 is proportional to the amount of work, so if the condensation temperature of the indoor heat exchanger 5 when heating the storage chamber is substantially fixed, the low-pressure shell compressor By simply enclosing 20 with a cover 21 made of a heat insulating material, the temperature of the lubricating oil decreases if the evaporation temperature −10 to + 10 ° C. of the outdoor heat exchanger 4 is low, and the temperature of the lubricating oil increases if it is high. It shows a tendency to keep the temperature almost right. Therefore, if the heat insulation characteristic of the cover 21 is appropriately adjusted, the energization of the heater 23 can be made substantially zero.

Here, refer to FIG. 4 and FIG. 5 for the influence of using mineral oil B having a kinematic viscosity at 40 ° C. of about 30 mm ² / s instead of mineral oil A having a kinematic viscosity at 40 ° C. of about 10 mm ² / s. However, it will be described below. Note that description of the same terms as those in FIGS. 2 and 3 is omitted.

  As shown in FIG. 4, the characteristics of the amount of refrigerant dissolved in the oil of the mineral oil B tend not to differ greatly from the mineral oil A shown in FIG. 2. Further, from the viewpoint of suppressing the amount of hydrocarbon refrigerant used, the amount of refrigerant dissolved in oil is preferably 0 to 5% by weight.

As shown in FIG. 5, the oil viscosity characteristic of the mineral oil B changes in the absolute value of the oil viscosity as compared with the mineral oil A shown in FIG. 3, but the change tendency is the same. As a result, in order to maintain the proper oil viscosity of 3 to 10 mm ² / s from the viewpoint of ensuring the durability of the compressor and reducing the loss due to the viscous resistance of the lubricating oil, the oil temperature is set lower than that of the mineral oil A. It is necessary to control it higher.

  In this embodiment, when mineral oil B is used instead of mineral oil A, when cooling the storage chamber, the saturation temperature of the refrigerant is −30 to −10 ° C., so that an appropriate oil viscosity is maintained. It turns out that it is necessary to keep oil temperature at 70-120 degreeC. Therefore, if the cover 21 made of a heat insulating material is thickened to improve the heat insulating performance, or if the low pressure shell type compressor 20 having a small outer surface area and a relatively high temperature is selected, an appropriate oil as in the present embodiment is selected. Medium refrigerant dissolution and oil viscosity can be achieved.

  Similarly, when the interior of the storage room is heated, it is understood that the oil temperature may be kept at 70 to 120 ° C. in order to maintain an appropriate oil viscosity. This is because even if the saturation temperature of the refrigerant is −10 to + 10 ° C., the amount of refrigerant dissolved in oil becomes appropriate if the oil temperature is kept at 40 to 80 ° C. or higher.

However, if the control target of the oil temperature when cooling and warming the storage chamber is too high, the oil temperature reaches the target value and is appropriate if the initial oil temperature is low, such as when the low-pressure shell compressor 20 is started. There is a problem that it takes a long time to drive. For example, since a large amount of power is consumed by energizing the heater 23 for a long time, the upper limit of the control target of the oil temperature is desirably about 80 ° C. Thus, the kinematic viscosity of the low-pressure shell type compressor 20 at 40 ° C. is 3 to 30 mm ² / s or so, preferably it is better to use a mineral oil of about 10 mm ² / s.

  In this embodiment, when the high-pressure shell compressor 1 is used instead of the low-pressure shell compressor 20, the saturation temperature of the refrigerant is 20 to 50 ° C. during cooling and 50 to 70 ° C. during heating. Therefore, as can be seen from FIGS. 2 and 4, a higher oil temperature above 120 ° C. is required. Further, as can be seen from FIGS. 3 and 5, in order to obtain an appropriate oil viscosity at a higher oil temperature exceeding 120 ° C., it is necessary to use a mineral oil having a higher viscosity, and from the heat exchanger that becomes the evaporation temperature. There is concern about the oil return. In particular, it is more difficult to suppress the amount of refrigerant used by maintaining the amount of refrigerant dissolved in oil at an appropriate value of 0 to 5% by weight corresponding to the saturation temperature of the refrigerant at the time of heating of 50 to 70 ° C. . Therefore, it is necessary to apply a special lubricating oil in which the amount of dissolved hydrocarbon refrigerant is small, and it is difficult to put it to practical use due to its price and lack of results.

In the present embodiment, instead of mineral oil A and mineral oil B, ester oil having a kinematic viscosity at 40 ° C. of about 3 to 30 mm ² / s can also be used. For example, ester oils composed of hindered esters using polyhydric alcohols such as pentaerythritol and neopentyl glycol, which are generally used as a lubricating oil for refrigerators using R134a, are relatively inexpensive and have a track record of use. It is practical. Such ester oils can be used in the same manner as mineral oil because they exhibit the same amount of dissolved hydrocarbon refrigerant as mineral oil. Furthermore, since such ester oil has a water dissolution amount several tens of times that of mineral oil, it has a feature that moisture chalk is hardly generated, and can be operated without a dryer. As a result, it is possible to reduce the amount of hydrocarbon refrigerant staying in the dryer.

As described above, the cooling and heating system according to the present invention uses a low-pressure shell compressor, uses R600a as a refrigerant, and has a kinematic viscosity of 40 ° C., which is inexpensive and generally used as a lubricating oil for compressors. By using mineral oil or ester oil of ˜30 mm ² / s, the amount of refrigerant dissolved in the lubricating oil can be kept substantially constant, especially when products such as can drinks are heated to a high temperature of 50 to 100 ° C. In a cooling and heating system that switches between cooling and heating, such as a showcase or a food storage, it can also be applied for the purpose of improving efficiency and reliability while suppressing the amount of hydrocarbon refrigerant used.

FIG. 1 is a refrigerant circuit diagram of a cooling and heating system according to Embodiment 1 of the present invention. The figure which shows the characteristic of the refrigerant | coolant dissolution amount in the oil of the mineral oil A by Embodiment 1 of this invention The figure which shows the characteristic of the oil viscosity of the mineral oil A by Embodiment 1 of this invention The figure which shows the characteristic of the refrigerant | coolant dissolution amount in the oil of the mineral oil B by Embodiment 1 of this invention The figure which shows the characteristic of the oil viscosity of the mineral oil B by Embodiment 1 of this invention Refrigerant circuit diagram of conventional cooling and heating system

Explanation of symbols

20 Low-pressure shell compressor 21 Cover 22 Sensor 23 Heater 24 Fan

Claims (5)

An indoor heat exchanger installed in a room for storing products, an outdoor heat exchanger installed outside a compartment for storing products, an expansion mechanism, a compressor, the compressor, the expansion mechanism, and the indoor heat A cooling and heating system pipe connecting the exchanger and the outdoor heat exchanger in an annular shape, and circulating the refrigerant discharged from the compressor from the outdoor heat exchanger to the expansion mechanism and the indoor heat exchanger A four-way switching valve for selecting whether to return to the compressor or to circulate the expansion mechanism and the outdoor heat exchanger from the indoor heat exchanger and return to the compressor. Is a low-pressure shell type compressor, R600a is used as a refrigerant, and mineral oil having a kinematic viscosity at 40 ° C. of 3 to 30 mm ² / s is used as lubricating oil for the compressor. An indoor heat exchanger installed in a room for storing products, an outdoor heat exchanger installed outside a compartment for storing products, an expansion mechanism, a compressor, the compressor, the expansion mechanism, and the indoor heat A cooling and heating system pipe connecting the exchanger and the outdoor heat exchanger in an annular shape, and circulating the refrigerant discharged from the compressor from the outdoor heat exchanger to the expansion mechanism and the indoor heat exchanger A four-way switching valve for selecting whether to return to the compressor or to circulate the expansion mechanism and the outdoor heat exchanger from the indoor heat exchanger and return to the compressor. Is a low-pressure shell compressor, R600a is used as a refrigerant, and ester oil having a kinematic viscosity of 3 to 30 mm ² / s at 40 ° C. is used as a lubricating oil for the compressor. .   The cooling and heating system according to claim 1 or 2, wherein the compressor is surrounded by a heat insulating material, and the temperature of the lubricating oil during heating is maintained at 40 to 80 ° C.   The cooling and heating system according to claim 1, further comprising a heater for heating the compressor, wherein the heater is energized when the temperature of the compressor falls below a predetermined value during heating.   The cooling and heating system according to claim 1, further comprising a fan for cooling the compressor, wherein the fan is operated when the temperature of the compressor exceeds a predetermined value during cooling.

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