JP2005283088A - Refrigerator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerator capable of precluding a treated object from contaminated with an oil mixed into a refrigerant gas, so as to maintain an excellent refrigeration capacity. <P>SOLUTION: This refrigerator 1 is provided with the first circulation circuit I including a main compressor 11, a cooler 12, the first heat exchanger 13, an expander 14 and the second heat exchanger 15, and arranged for the refrigerant gas returned to the main compressor 11 passed again through the first heat exchanger 13, after passing the main compressor 11, the cooler 12, the first heat exchanger 13, the expander 14 and the second heat exchanger 15, and the second circulation circuit II including the second heat exchanger 15 and a refrigeration processing chamber 16, and arranged for air of a cooling medium returned to the second heat exchanger 15 after passed through the second heat exchanger 15 and the refrigeration processing chamber 16. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a refrigerator for freezing a workpiece.

2. Description of the Related Art Conventionally, a refrigerator in which low temperature air is directly brought into contact with an object to be processed to freeze the object to be processed is known (for example, see Patent Document 1).
Japanese Patent No. 3111065 (paragraphs [0010] and [0015], FIG. 1)

  Patent Document 1 discloses a refrigerator in which refrigerant gas, for example, air is circulated through a closed flow path. In this refrigerator, when the moisture solidification component generated in the freezing treatment of the object to be processed in the freezing treatment chamber (cold heat consumption equipment 20) is mixed in the recovered refrigerant gas and directly flows into the cold recovery heat exchanger, The cold recovery heat exchanger is blocked by the moisture-solidifying component, and the refrigerator cannot be operated normally. For this reason, a filter is provided on the secondary side of the freezing treatment chamber as a dehumidifying means for removing the moisture-solidifying component. And the said moisture solidification component is removed with the said filter from the refrigerant | coolant air which goes to the said cold recovery heat exchanger, The obstruction | occlusion of the said cold recovery heat exchanger by the said moisture solidification component is prevented. The filter also collects dust in the recovered refrigerant air, and clean refrigerant air is guided to the compressor via the cold recovery heat exchanger.

  In the above-described air refrigerator, since the refrigerant gas comes into contact with the object to be processed in the refrigeration chamber, if oil leaks from the compressor bearing or the like and enters the refrigerant gas, the object to be processed There is a problem that this oil is contaminated in the refrigeration chamber.

  Further, since it is in contact with the atmosphere, the pressure in the refrigeration chamber, which is in a state of substantially atmospheric pressure, is equal to the suction pressure of the compressor, and this suction pressure is substantially equal to atmospheric pressure. On the other hand, in order to improve the refrigeration capacity in the refrigeration processing chamber of the air refrigerator, it is necessary to increase the flow rate of the circulating refrigerant gas. It is necessary to increase the size in response to. As a result, the air refrigerator becomes bulky, and the occupied space increases, and there is a problem that mechanical loss at the movable part increases with an increase in the size of a bearing such as a compressor or an expander.

  The present invention has been made in order to eliminate such a conventional problem, eliminates contamination of the object to be processed by oil mixed in the refrigerant gas, and does not cause an increase in mechanical loss in the occupied space or the movable portion. An object of the present invention is to provide a refrigerator that can maintain a good refrigeration capacity.

  In order to solve the above problems, the first invention includes at least a main compressor, a cooler, a first heat exchanger, an expander, and a second heat exchanger, and the main compressor, the cooler, and the first heat exchange. A first circulation flow path for refrigerant gas that passes through the first heat exchanger and then returns to the main compressor through the first heat exchanger, and at least the second heat exchanger and the refrigeration chamber. And a second circulation channel of a cooling medium that returns to the second heat exchanger through the second heat exchanger and the refrigeration chamber.

  In addition to the configuration of the first invention, the second invention includes a pressure detector provided in the first circulation channel so as to be capable of detecting pressure, and supply of the boosting refrigerant gas to the first circulation channel. On the secondary side of the second heat exchanger, at a position between the second heat exchanger and the main compressor, based on the pressure value that is formed and detected by the pressure detector. A pressure increasing unit that controls the supply of the pressure increasing refrigerant gas is provided so that the pressure of the first circulation channel is higher than a set pressure that is set higher than the atmospheric pressure.

  Furthermore, the third aspect of the invention has a configuration in which the pressurizing refrigerant gas is in a dry state in addition to the configuration of the second aspect of the invention.

  Furthermore, the fourth invention includes at least a main compressor, a cooler, a first heat exchanger, an expander, and a second heat exchanger. The main compressor, the cooler, the first heat exchanger, the expander, Including a first circulation passage of refrigerant gas that passes through the second heat exchanger and then returns to the main compressor through the first heat exchanger, at least the second heat exchanger, and a refrigeration treatment chamber. A heat exchanger, a second circulation channel for the cooling medium that returns to the second heat exchanger through the refrigeration chamber, and a pressure-increasing unit that is configured to be capable of supplying the pressure-reducing refrigerant gas to the first circulation channel And a step-down portion formed so that the refrigerant gas can be discharged from the first circulation flow path, and a temperature detector provided in the refrigeration processing chamber so as to be capable of detecting an indoor temperature, and detected by the temperature detector. If the detected temperature is higher than a predetermined allowable upper limit temperature, the first circulating flow path is cooled from the boosting unit. While to supply the gas, when the detected temperature is lower than the predetermined allowable lower limit temperature was configured for discharging the refrigerant gas from the first circulation passage in the step-down unit.

  According to the first invention, the second circulation channel of the cooling medium supplied to the refrigeration chamber is completely independent of the first circulation channel except for heat exchange in the second heat exchanger. Even if there is a situation where oil leaks from the bearing section in the main compressor and this oil is mixed into the dry air, it does not share the flow path. It is possible to prevent the object to be cooled from being contaminated with oil.

  Further, according to the second invention, in addition to the effect of the first invention, the pressure on the suction side of the main compressor is maintained in a state higher than the atmospheric pressure, and the inflow of outside air including moisture from the suction side is prevented. Thus, blockage of the flow path by the ice in the first circulation flow path, particularly in the first heat exchanger, can be avoided, and the suction side is boosted from the atmospheric pressure so that the occupied space of the entire refrigerator and the movable space can be moved. There is an effect that it is possible to improve the refrigerating capacity without increasing at least the mechanical loss.

  Furthermore, according to the third invention, in addition to the effects of the second invention, even if the refrigerant gas in the first circulation channel gradually leaks to the outside, the refrigerant is supplied from the booster to the first circulation channel. Since the pressurizing gas is dry, it is possible to prevent the occurrence of a clogging due to freezing of water in the heat exchanger, particularly the first heat exchanger.

  Furthermore, according to the fourth invention, in addition to the effects of the first invention, the expansion ratio in the expander can be kept constant, the efficiency of the refrigerator can be maintained substantially constant, the refrigeration capacity can be changed as appropriate, and the partial load Even in the operating state, there is an effect that it can be operated with an appropriate refrigerating capacity.

Next, an embodiment of the present invention will be described with reference to the drawings.
1 and 2 show a refrigerator 1 according to the present invention, which has undergone a main compressor 11, a cooler 12, a first heat exchanger 13, an expander 14, and a second heat exchanger 15. Thereafter, the refrigerant gas returns to the main compressor 11 through the first heat exchanger 13 again, and the cooling returns to the second heat exchanger 15 through the first circulation flow path I of the refrigerant gas, the second heat exchanger 15 and the refrigeration chamber 16. And a second circulation channel II of air as a medium. Further, in the portion between the first heat exchanger 13 and the main compressor 11 in the first circulation flow path I, a pressure increase gas flow path III extending from a pressure increase section 17A described later joins, and the gas in the pressure increase gas flow path III The flow rate is adjusted by a pressure detector 18 provided in a portion between the second heat exchanger 15 and the first heat exchanger 13 in the first circulation channel I. In the illustrated embodiment, the cooler 12 is not limited, but is a water-cooled type, and the main compressor 11 and the expander 14 share a motor 19 as a drive source.

  As shown in FIG. 2, the booster 17A includes a driving means 21, for example, an auxiliary compressor 22 driven by a motor, a suction passage 24 communicating with the atmosphere through the intake filter 23, and a dryer 25, for example, a membrane. In the example shown in the figure, dry air is supplied from the pressurization gas passage III to the first circulation passage I. ing.

In the refrigerator 1 having the above-described configuration, after the air sucked into the auxiliary compressor 22 through the intake filter 23 and the suction flow path 24 of the booster 17A is compressed, the boosted gas flow from the auxiliary compressor 22 is compressed. It is discharged to the path III, becomes dry air through the dryer 25, and is supplied to the first circulation flow path I as the refrigerant gas. In the first circulation channel I, the main compressor 11 sucks dry air as the refrigerant gas and compresses it, and cools it from the main compressor 11 in a state of pressure: about 8 kgf / cm ² and temperature: about 160 ° C. The liquid is discharged toward the container 12. The dry air that has been cooled by the cooler 12 and exits from the air passes through the first heat exchanger 13 under a pressure of about 8 kgf / cm ² and a temperature of about 40 ° C., and forms a counterflow described later. Heat exchange with air results in a pressure of about 8 kgf / cm ² and a temperature of about −30 ° C. and is sent to the expander 14. In the expander 14, the dry air is expanded to a pressure of about 2 kgf / cm ² and a temperature of about −100 ° C., and then reaches the second heat exchanger 15, where cooling is performed in a counterflow described later. Heat exchange with air as a medium results in a pressure of about 2 kgf / cm ² and a temperature of about −40 ° C., and is sent out toward the first heat exchanger 13. Further, in the first heat exchanger 13, the pressure: about 2 kgf / cm ² , the temperature: about −40 ° C. and the cooler 12 described above, the pressure: about 8 kgf / cm ² , the temperature: about 40 Heat is exchanged with the countercurrent dry air that has flowed in at a temperature of ° C. Specifically, heat is taken from the countercurrent dry air, pressure: about 2 kgf / cm ² , temperature: It returns to the main compressor 11 at about 30 ° C. Then, this dry air is again sucked into the main compressor 11 and is discharged after being compressed, and the circulation in the first circulation flow path I is repeated.

On the other hand, the second heat exchanger 15 is supplied with air as a cooling medium that is supplied to the refrigeration chamber 16 so as to be opposed to the dry air in the first circulation flow path I and circulated. Heat exchange is performed between the two and the air as the cooling medium is cooled by the dry air in the first circulation channel I. Specifically, the air flows into the second heat exchanger 15 in a state where the pressure is about 1.033 kgf / cm ² (atmospheric pressure) and the temperature is about −40 ° C., and is cooled by the dry air and the pressure: About 1.033 kgf / cm ² (atmospheric pressure), temperature: About −80 ° C., the temperature is extremely low, exits the second heat exchanger 15, and is supplied to the refrigeration chamber 16. The refrigeration chamber 16 is, for example, a refrigeration warehouse that freezes food. A freezing process is performed directly on the object to be processed such as food using the cryogenic air supplied after cooling, and the air is then pressurized. : About 1.033 kgf / cm ² (atmospheric pressure), temperature: about −40 ° C., and inserted in the second circulation channel II from the refrigeration chamber 16 toward the second heat exchanger 15. It is sent out by a fan or the like (not shown) and repeats circulation in the second circulation channel II.

  Incidentally, when the refrigerator 1 is in operation, the discharge pressure of the main compressor 11 rises compared to when it is stopped. Therefore, when the amount of air in the first circulation channel I is constant, the suction pressure of the main compressor 11 There is a possibility that air will flow in from the outside of the main compressor 11 through the shaft seal portion or the like. In that case, even if the inside of the first circulation flow path I is replaced with dry air having a dew point of 0 ° C. or less in advance, the expander 14 of the first heat exchanger 13 flows due to the flow of outside air containing water vapor. In some cases, the dew point at the outlet portion that continues to become higher than 0 ° C., and if the air is simply replaced with dry air, the first heat exchanger 13 may block the flow path due to ice.

  However, in the case of this refrigerator 1, the pressure | voltage rise part 17A and the pressure detector 18 are provided as mentioned above, and there is no possibility that the said flow path will be obstruct | occluded with ice. That is, in the refrigerator 1, more specifically, the first circulation flow path I has a pressure detection in a portion between the second heat exchanger 15 and the first heat exchanger 13 in the first circulation flow path I. A detector 18 is provided, and the detected pressure at this portion is compared with a set pressure determined to be higher than the atmospheric pressure. When the detected pressure is lower than this, auxiliary compression is performed by a control signal from the pressure detector 18 to the driving means 21. The machine 22 is operated, and dry air is supplied to the first circulation flow path I from the pressure increase gas flow path III of the pressure increase section 17A so that the detected pressure becomes higher than the set pressure. Therefore, the inflow of air from outside the machine through the shaft seal portion of the main compressor 11 is prevented.

  For the driving means 21 of the auxiliary compressor 22, a pressure signal indicating the detected pressure is input from the pressure detector 18 to a control means (not shown), and whether or not the detected pressure is lower than a set pressure higher than the atmospheric pressure. If yes, the control means may output a control signal to the drive means 21 to operate the auxiliary compressor 22 so that the pressure detected by the pressure detector 18 increases.

  As described above, in the refrigerator 1, the second circulation channel II of the cooling medium supplied to the refrigeration chamber 16 is the same as the first circulation channel I except for the heat exchange in the second heat exchanger 15. Are provided separately and independently, and do not share the flow path. As a matter of course, oil leaks from the bearing portion or the like in the main compressor 11 and this oil enters the dry air. However, the object to be cooled such as food in the freezing treatment chamber 16 is prevented from being contaminated by oil.

By the way, in the refrigerator 1, if the weight flow rate of the dry air which is the circulating refrigerant is made constant, the refrigerating capacity is maintained constant. For example, when the suction pressure of the main compressor 11 is atmospheric pressure and the flow rate is about 30 m ³ / min, if the suction pressure becomes three times the atmospheric pressure × 3, the flow rate is maintained to maintain the refrigeration capacity constant. What is necessary is just to set to about 10 m < ³ > / min of 1/3. That is, the main compressor 11 of the refrigerator 1 in which the suction pressure is higher than the atmospheric pressure under the condition that the refrigerating capacity is equivalent to the conventional air refrigerator in which the suction pressure of the main compressor is approximately atmospheric pressure. In comparison, the main compressor 11, the cooler 12, the first heat exchanger 13, the expander 14, and the second heat exchanger 15 interposed in the first circulation flow path I can be downsized. Even in consideration of the necessity of ancillary equipment such as the dry gas supply unit 17A in order to make the suction pressure higher than the atmospheric pressure, overall, the occupied space can be reduced, and the main compressor 11 can be reduced. And the merit that reduction of the mechanical loss in the movable part of the expander 14, etc. becomes possible is large.

  In order to increase the refrigerating capacity, it is necessary to increase the flow rate in the first circulation flow path I by increasing the size of the main compressor 11 and the expander 14, but the main compressor has a suction pressure of approximately atmospheric pressure. In the case of the refrigerator 1 using the main compressor 11 in which the suction pressure is higher than the atmospheric pressure, the size of the conventional air refrigerator does not need to be increased as compared with the conventional air refrigerator.

  Further, the dry air circulating in the first circulation flow path I may gradually leak out of the main compressor 11 and the movable part of the expander 14, etc., but the first circulation from the booster 17A. Since the pressurizing dry air is supplied to the flow path I, the pressure in the first circulation flow path I is not lowered by the leakage and is maintained higher than the set pressure. Since it is the dry air that is supplied to the first circulation flow path I from the booster 17 </ b> A, it is possible to prevent the heat exchanger, particularly the first heat exchanger 13, from being blocked by freezing of water.

In the embodiment described above, the booster 17A supplies dry air using the auxiliary compressor 22 and the dryer 25, but the present invention is not limited to this.
FIG. 3 shows a booster 17B instead of the booster 17A. A nitrogen gas supply source 31, for example, a nitrogen gas cylinder, one end of which is connected to the nitrogen gas supply source 31, a flow control valve 32 is interposed, and the booster 17A In the same manner as in this case, it is composed of a pressurized gas flow path III that merges with the first circulation flow path I. In the case of the refrigerator 1 using the pressure increasing unit 17B, the refrigerant gas is dry nitrogen gas instead of the above-described dry air. Then, the flow rate adjustment valve 32 is controlled based on the pressure detected by the pressure detector 18 in the same manner as described above, and the flow rate of the dry nitrogen gas supplied from the pressurization gas channel III to the first circulation channel I is adjusted. The pressure in one circulation channel I is maintained as described above.
If the refrigerant gas is nitrogen gas, a nitrogen gas cylinder can be adopted as the nitrogen gas supply source 31, and the structure can be simplified.

FIG. 4 shows a booster 17C that replaces the booster 17A or the booster 17B, and parts that are common to the booster 17A shown in FIG.
In the case of the refrigerator 1 using the pressurizing unit 17C, the refrigerant gas is dry nitrogen gas. In the pressurizing unit 17C, a pressure swing adsorption type nitrogen gas generating device 41, generally called a PSA type nitrogen gas generating device, is used as the auxiliary compressor 22. A pressure-increasing gas passage III that is also a discharge passage from is interposed.
This pressure swing adsorption type nitrogen gas generator 41 uses an adsorption tower with a built-in special adsorbent, and selects and removes only oxygen from the air by using the special adsorbent in the adsorption tower under pressure. Is a well-known device for generating In the adsorption tower, oxygen selectively adsorbed and removed by the special adsorbent under pressure is purged by reducing the pressure in the adsorption tower, and the adsorption tower is used repeatedly. Then, dried nitrogen gas is supplied from the auxiliary compressor 22 to the first circulation flow path I via the pressure swing adsorption type nitrogen gas generator 41, and the auxiliary compression is performed based on the pressure detected by the pressure detector 18 as described above. The flow rate of the compressed air discharged from the machine 22 is controlled, and the pressure in the first circulation channel I is maintained higher than the set pressure.

Note that the booster 17B or the booster 17C may be controlled by the pressure detector 18 to control the opening degree of the opening degree adjustment valve 32 and the driving means 21, as described above, via the control means (not shown). The opening degree of the opening degree adjusting valve 32 and the driving means 21 may be controlled.
Further, the position at which the drying gas is supplied from the boosting units 17A, 17B, and 17C to the first circulation channel I is not necessarily limited to the position in the above-described embodiment. The mounting position of the pressure detector 18 is not limited, and may be any position between the second heat exchanger 15 and the main compressor 11 on the secondary side of the second heat exchanger 15. .
Furthermore, the above-described pressure and temperature states in each part of the refrigerator 1 are merely examples for reference, and it goes without saying that the present invention is not limited to these pressure and temperature values.

  In the above-described embodiment, the cooling medium circulating in the second circulation channel II is air, and the cooling medium directly freezes food or the like. However, the present invention is limited to this. is not. In addition, a gas other than air, for example, dry nitrogen gas exemplified as the refrigerant gas may be used as the cooling medium. In this case, the air in the refrigeration chamber 16 does not flow into the second circulation channel II and the cooling medium in the second circulation channel II does not flow out into the refrigeration chamber 16. A part of the circulation channel II in the refrigeration chamber 16 is not opened in the refrigeration chamber 16, and is constituted by, for example, a pipe, and the second circulation channel II is formed in the refrigeration chamber 16 and the cooling medium in the second circulation channel II. It is good to make it the closed flow path which the inside air does not contact directly.

  Further, in the above-described embodiment, the pressure detector 18 is provided at a position between the second heat exchanger 15 and the first heat exchanger 13 in the first circulation flow path I. It is not limited to. Even if the pressure detector 18 is provided at another position of the first circulation flow path I, the second heat exchanger 15 is provided on the secondary side of the second heat exchanger 15 based on the pressure value detected there. Since the pressure of the first circulation flow path I at a position between the main compressor 11 and the main compressor 11 can be uniquely guided, the pressure detector 18 may be provided at any position of the first circulation flow path I. . However, the final data used for boosting in the first circulation channel I is on the secondary side of the second heat exchanger 15 and at a position between the second heat exchanger 15 and the main compressor 11. The pressure value of the first circulation channel I and the pressure value detected at that position is the most reliable, and the pressure detector 18 includes the second heat exchanger 15 and the first heat exchanger described above. Preferably, it is provided at a position between the first heat exchanger 13 and the main compressor 11.

FIG. 5 shows another refrigerator 2 according to the present invention. In FIG. 5, parts common to the refrigerator 1 shown in FIG.
In this refrigerator 2, a main compressor is configured by meshing a driving side gear 51 attached to the output shaft of the motor 19 with driven side gears 52 and 53 attached to the respective rotor shafts of the main compressor 11 and the expander 14. 11 and each of the expanders 14 are operated. However, each of the main compressor 11 and the expander 14 may be directly operated by the motor 19 as in FIG. In the refrigerator 2, a step-down unit 54 formed so that the refrigerant gas can be discharged from the first circulation flow path I, and a temperature detector 55 are provided in the refrigeration processing chamber 16 so that the room temperature can be detected. When the temperature detected by the temperature detector 55 is higher than a predetermined allowable upper limit temperature, that is, when the refrigerating capacity is too low, a control signal from the temperature detector 55 causes the first circulation channel from the booster 17A. When the refrigerant gas is supplied to I and the pressure drop unit 54 is closed, while the detected temperature is lower than a predetermined allowable lower limit temperature, the first circulation flow path is sent to the pressure drop unit 54 by a control signal from the temperature detector 55. The refrigerant gas is discharged from I, and the booster 17A is closed. It is desirable that the pressure-lowering unit 54 is provided so as to discharge the refrigerant gas at the inlet side of the expander 14 on the discharge side of the main compressor 11 in the first circulation flow path I. In the example shown in the figure, a step-down gas passage IV that branches from the portion of the first circulation passage I between the first heat exchanger 13 and the expander 14 and reaches the step-down unit 54 is provided. Since the refrigerant gas has a high pressure at the branch point of the path IV, the refrigerant gas can be easily discharged. In the refrigerator 2, the refrigerant in the first circulation flow path I and the cooling medium in the second circulation flow path II are opposed to each other in the second heat exchanger 15. A similar configuration may be used.

  With such a configuration, in the case of this refrigerator 2, the refrigerating capacity can be adjusted by the booster 17A and the depressurizer 54 while keeping the rotation speed of the motor 19 constant. For example, the refrigerating capacity is desired to be lowered. Even in this case, it is not necessary to decrease the rotation speed of the motor 19 and shift to the partial load operation. Therefore, the motor 19 in the refrigerator 2 does not have to be variable in rotation speed. Note that the temperature detector 55 detects the room temperature of the refrigeration chamber 16 and issues a control signal to control the pressure-up unit 17A and the pressure-down unit 54. Alternatively, a temperature signal indicating the room temperature of the refrigeration chamber 16 may be input from the temperature detector 55 to a control unit (not shown), and the boosting unit 17A and the stepping-down unit 54 may be controlled by this control unit.

  In the case of the refrigerators 1 and 2, the cooling capacity that is the ability to cool the object to be processed in the refrigeration chamber 16 is a cooling medium (eg, air) that circulates in the second circulation channel II through the refrigeration chamber 16. Depends on temperature and weight flow rate. Since this cooling medium exchanges heat with the refrigerant in the first circulation flow path I in the second heat exchanger 15, the cooling capacity eventually becomes the temperature and weight flow rate of the refrigerant circulating in the first circulation flow path I. It can be said that it depends. In the case of the refrigerator 1, if the refrigeration capacity is excessive, a partial load operation is required to reduce the refrigeration capacity and make it appropriate. In this case, for example, a partial load operation is performed in which the weight flow rate of the refrigerant is reduced by reducing the rotational speeds of the main compressor 11 and the expander 14. By the way, when the main compressor 11 is, for example, a screw compressor, the flow rate of the working gas is substantially proportional to the rotational speed, whereas when the expander 14 is, for example, an expansion turbine, the flow rate of the working gas is the above-described screw compression. Not as proportional as the machine. For this reason, in the case of the partial load operation described above, the inlet pressure of the expander 14 is reduced and the expansion ratio is reduced. On the other hand, in general, an expansion turbine is designed to have the highest efficiency when the rotational speed is at a maximum value. Therefore, when the expansion turbine is employed in the refrigerator 1, the efficiency of the expander 14 is reduced during the above-described partial load operation where the expansion ratio is small. However, as described above, in the refrigerator 2, the refrigeration capacity can be adjusted without changing the rotation speed of the motor 19, so that a situation in which the efficiency of the expander 14 decreases as described above is avoided. The

  More specifically, for example, when the main compressor 11 is a screw compressor, the volume flow rate is determined by the rotational speed of the rotor, and the motor 19 is rotated at a constant rotational speed as described above. The volume flow rate of the compressor 11 is constant. For example, when the expander 14 is an expansion turbine, the volume flow rate is constant if the expansion ratio is the same. If this expansion ratio is constant, the temperature level in the system through which the refrigerant circulates is the same. On the other hand, if refrigerant gas (dry air) is supplied or discharged as in the refrigerator 2, the pressure level in the system changes. Therefore, in the refrigerator 2, the conditions of “constant expansion ratio”, “constant volume flow”, “constant temperature level in the system”, and “change in pressure level in the system” are realized by supplying and discharging the refrigerant gas. Will be. By the way, since the cooling capacity depending on the amount of cooling heat is proportional to the weight flow rate (volume flow rate) and temperature of the refrigerant, in the case of the refrigerator 2 according to the present invention having a constant volume flow rate and a constant temperature level in the system, The refrigeration capacity can be changed by changing the pressure level. Further, since the expansion ratio of the expander 14 is constant, the efficiency of the expander 14 and thus the efficiency of the refrigerator 2 is maintained constant. That is, in the case of the refrigerator 2, while maintaining the efficiency constant, it is possible to appropriately change the refrigeration capacity and to operate with an appropriate refrigeration capacity. As described above, in general, expansion turbines are designed to have the highest efficiency at the maximum number of revolutions. If the constant number of revolutions is set to the maximum number of revolutions, the highest efficiency is always maintained. However, the refrigeration capacity can be changed appropriately.

  FIG. 6 (horizontal axis: refrigeration capacity (%), vertical axis: coefficient of performance (COP)) shows a result corresponding to the above efficiency when the maximum value of the refrigeration capacity is 100% and the refrigeration capacity is lowered from this state. A mode in which the coefficient (COP) changes is indicated by a solid line A for the refrigerator 2 and indicated by a one-dot chain line B for a refrigerator that is not provided with the step-down unit 54 and that is operated at a partial load by lowering the rotational speed of the motor. It is a thing. As shown in the figure, in the case of the refrigerator 2, a substantially constant coefficient of performance, that is, efficiency is maintained, whereas in the case of the other refrigerator, the coefficient of performance greatly decreases as the refrigeration capacity decreases. I understand that.

It is a block diagram which shows the whole structure of the refrigerator which concerns on this invention. It is a block diagram which shows the detail of the pressure | voltage rise part in the refrigerator shown in FIG. It is a block diagram which shows another pressure | voltage rise part used for the refrigerator shown in FIG. 1 instead of the pressure | voltage rise part shown in FIG. It is a block diagram which shows another pressure | voltage rise part used for the refrigerator shown in FIG. 1 instead of the pressure | voltage rise part shown in FIG. It is a block diagram which shows the whole structure of the other refrigerator based on this invention. It is the figure which showed the relationship between refrigeration capacity | capacitance and a coefficient of performance about the refrigerator which is not equipped with the refrigerator based on this invention, and another pressure | voltage reduction part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 Refrigerator 11 Main compressor 12 Cooler 13 1st heat exchanger 14 Expander 15 2nd heat exchanger 16 Refrigeration processing chamber 17A, 17B, 17C Booster 18 Pressure detector 19 Motor 21 Drive means 22 Auxiliary compression Machine 23 Intake filter 24 Suction passage 25 Dryer 31 Nitrogen gas supply source 32 Flow rate adjustment valve 41 Pressure swing adsorption type nitrogen gas generator 51 Drive side gears 52, 53 Drive side gear 54 Step-down gear 55 Temperature detector
I 1st circulation flow path
II Second circulation channel
III Pressurized gas flow path
IV Step-down gas flow path

Claims (4)

After including at least the main compressor, cooler, first heat exchanger, expander, and second heat exchanger, after passing through the main compressor, cooler, first heat exchanger, expander, and second heat exchanger A first circulation flow path of the refrigerant gas returning to the main compressor through the first heat exchanger again,
A cooling medium second circulation flow path including at least the second heat exchanger and the refrigeration chamber and returning to the second heat exchanger via the second heat exchanger and the refrigeration chamber. Refrigerator.   A pressure detector provided in the first circulation channel so as to be capable of detecting pressure, and a pressure value detected by the pressure detector formed so as to be capable of supplying the pressure-reducing refrigerant gas to the first circulation channel. On the secondary side of the second heat exchanger, the pressure of the first circulation channel at a position between the second heat exchanger and the main compressor is determined to be higher than the atmospheric pressure. The refrigerator according to claim 1, further comprising: a boosting unit that controls supply of the boosting refrigerant gas so as to be higher than the set pressure.   The refrigerator according to claim 2, wherein the pressurizing refrigerant gas is in a dry state. After including at least the main compressor, cooler, first heat exchanger, expander, and second heat exchanger, after passing through the main compressor, cooler, first heat exchanger, expander, and second heat exchanger A first circulation flow path of the refrigerant gas returning to the main compressor through the first heat exchanger again,
A second circulation channel of a cooling medium including at least the second heat exchanger and the refrigeration processing chamber, returning to the second heat exchanger through the second heat exchanger and the refrigeration processing chamber;
A pressurizing unit formed to be capable of supplying the refrigerant gas for pressurization to the first circulation channel;
A step-down portion formed such that the refrigerant gas can be discharged from the first circulation channel;
A temperature detector provided in the refrigeration chamber so as to be capable of detecting the indoor temperature;
When the detected temperature detected by the temperature detector is higher than a predetermined allowable upper limit temperature, the refrigerant gas is supplied from the booster to the first circulation flow path, while the detected temperature is a predetermined allowable lower limit. When the temperature is lower than the temperature, the step-down portion causes the refrigerant gas to be discharged from the first circulation flow path.

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