JP2012137218A - Method and apparatus for defrosting air refrigerant type refrigerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air refrigerant type refrigerator that enables a highly efficient energy-saving defrosting operation.SOLUTION: The air refrigerant type refrigerator includes: a pressure sensor 50 detecting suction pressure of a compressor 12; a temperature sensor 52 detecting an air refrigerant temperature on a compressor outlet side; a temperature sensor 54 detecting an air refrigerant temperature on an expander 18 outlet side; a first bypass passage 36 with a valve interposed therein, making an air refrigerant on the outlet side of a primary cooler 22 pass therethrough into an expander inlet side; and a second bypass passage 38 with a valve interposed therein, making an air refrigerant on the outlet side of the expander, bypass a chamber 32 to be cooled, and supplying the air refrigerant to the inlet side of a frosting trap 34. When the suction pressure of the compressor becomes a preset pressure Pcs or less, the defrosting operation is performed while flowing an air refrigerant through the first and second bypass passages 36 and 38, and the defrosting step is finished when an air refrigerant temperature in a frost formation area across an inlet of a heat recovery device from the outlet portion of the expander, becomes a preset value Tts of a melting finishing temperature in a plus temperature near "0°C", while the air refrigerant temperature on a compressor outlet side is maintained in a preset temperature Tcs not more than an allowance temperature.

Description

  The present invention relates to a defrost method and a defrost device that enable efficient defrost operation with energy saving in an air refrigerant refrigeration system using air as a refrigerant.

  Air refrigerant refrigeration system that uses air as refrigerant, high-pressure high-temperature air with a compressor, cools it with a cooler, and then low-pressure low-temperature with an expander does not use CFC-based refrigerants with a high global warming coefficient So there is an advantage that does not harm the environment. However, the cooling capacity is inferior to that of a phase change type refrigeration cycle in which evaporation and condensation are performed. However, the direct cooling method in which the refrigerant air is directly blown into the space for various uses to cool the space has a higher cooling effect than the indirect cooling method in which heat is exchanged with room air.

  The refrigeration cycle of an air refrigerant refrigeration apparatus constitutes a refrigeration cycle called a reverse Brayton cycle that operates counterclockwise, and is well known as an air conditioning refrigeration cycle for aircraft. The reverse Brayton cycle is a combination of an isentropic process (adiabatic compression process and adiabatic expansion process) and an isobaric process.

  FIG. 4 shows a configuration of a general air refrigerant refrigeration apparatus. In a general air refrigerant refrigeration apparatus 100, refrigeration cycle components are interposed in a refrigerant circulation path 102. The compressor 106 and the expander 108 are connected to a single output shaft 104a of the drive motor 104, and the compressor 106 and the expander 108 are driven simultaneously. The high-pressure and high-temperature air refrigerant discharged from the compressor 106 is primarily cooled by the primary cooler 112. A cooling water circulation path 110 is connected to the primary cooler 112. In the cooling water circulation path 110, a cooling water pump 116 and a water flow valve 118 capable of adjusting the flow rate are provided, and the cooling water is circulated by the cooling water pump 116 in the arrow direction. The cooling water is cooled by the cooling tower 114, and heat exchange with the air refrigerant is performed by the primary cooler 112 to cool the air refrigerant.

  The air refrigerant cooled by the primary cooler 112 is further cooled by the heat recovery unit 120 by exchanging heat with the air refrigerant returning from the chamber 122 to be cooled. The air refrigerant cooled by the heat recovery device 120 is expanded by the expander 108 to become low-pressure low-temperature air, and is supplied to the cooled chamber 122. The to-be-cooled chamber 122 is comprised, for example with a freezer or a freezer. The air refrigerant after the object to be cooled is cooled in the cooled chamber 122 includes fine ice carried from the cooled chamber 122, and a part of the fine ice is collected by the frost trap 124. The air refrigerant that has exited the frost trap 124 is heat-exchanged with the high-pressure and high-temperature air refrigerant that has exited the primary cooler 112 by the heat recovery device 120, cools the high-pressure and high-temperature air refrigerant, and then is sent to the compressor 106.

  The case where the refrigeration cycle (reverse Brayton cycle) of the air refrigerant refrigeration apparatus operates ideally will be described with reference to FIG. In FIG. 5, the positions of symbols a to f in the drawing are matched with the positions of symbols a to f in FIG. 4. The stroke (a → b) and the stroke (d → e) are isentropic strokes, the stroke (a → b) is an adiabatic compression stroke, and the stroke (d → e) is an adiabatic expansion stroke. The stroke (b → d) and the stroke (e → a) are isobaric strokes. The stroke (b → c) is a stroke when the air refrigerant is cooled by the primary cooler 112, and the stroke (e → f) is a cooling chamber 122 in which the air refrigerant cools the article to be cooled, This is the process for receiving the retained heat of the cooling product.

  The stroke (c → d) is a stroke when the air refrigerant that has exited the primary cooler 22 is heat-exchanged and cooled by the heat recovery device 120, and the stroke (f → a) is the air that has exited the frost trap 124. This is the process when the refrigerant exchanges heat with the heat recovery device 120 and absorbs heat. The entropy difference before and after both strokes is the same. Moreover, the temperature of the point a and the point c is the same, and the temperature of the point d and the point f is the same.

  In a normal refrigeration operation, the drive motor 104 is maintained at the rated rotational speed, and the water flow valve 115 provided in the cooling water circulation path 110 is always fully open (maximum water flow rate). The low temperature side isobaric heat exchange process (f → a) and the high temperature side isobaric heat exchange process (c → d) are processes of exchanging an equal amount of heat in an isobaric state, that is, a cold recycling process. .

  The biggest problem of such an air refrigerant type refrigeration apparatus is that it is transported from the cooled chamber 122 to the refrigerant circulation path from the outlet side of the cooled chamber 122 to the low temperature part inlet side of the heat recovery device 120 as the operation time elapses. The fine ice that accumulates gradually accumulates (frosts). With the progress of frost formation on the inlet side of the heat recovery device 120, the pressure loss of the low-temperature side refrigerant path increases, and finally the refrigerant path is closed. Moreover, the suction pressure of the compressor 106 decreases as frosting progresses, and the COP of the refrigeration cycle decreases. As a method for preventing frost formation, an attempt is made to provide a simple separator, that is, a defrost trap 124 in the outlet side refrigerant path of the chamber 122 to be cooled. The frost collected by the defrost trap 124 and the frost formation on the heat recovery device 120 and the low-temperature side refrigerant circulation path are melted and removed by performing a defrost operation.

  In Patent Documents 1 to 3, in the air refrigerant refrigeration apparatus, a defrost trap is provided in the low-temperature side refrigerant path, and air refrigerant at 0 ° C. or higher on the compressor discharge side is defrosted through the bypass path during the defrost operation. A technique for dissolving and removing frost accumulated in a defrost trap or the like through an area is disclosed.

In Patent Document 1 (FIG. 2), during the defrost operation, the high-pressure high-temperature air refrigerant on the compressor discharge side is reduced to low pressure and low temperature through the expander, and the low-pressure and low-temperature air refrigerant is supplied from the outlet side of the expander to the cooled chamber. A defrost method is disclosed in which it is bypassed and sent to the frosting area downstream of the room to be cooled.
Further, in Patent Document 1 (FIG. 1) and Patent Documents 2 and 3, the high-pressure and high-temperature air refrigerant on the compressor discharge side is bypassed from the expander and the cooled chamber during the defrost operation, and the downstream side of the cooled chamber is bypassed. A defrosting method for sending to a frosting zone is disclosed.

  Moreover, in patent document 4, after performing a defrost driving | operation in an air-refrigerant-type refrigeration apparatus, after a molten water discharge process and a molten water discharge process, it bypasses a to-be-cooled chamber and circulates an air refrigerant. It is disclosed that a precooling step for precooling the refrigerant circuit is provided.

Japanese Patent Laid-Open No. 11-132582 Japanese Unexamined Patent Publication No. 2003-287299 Japanese Unexamined Patent Publication No. 2006-118772 JP 2008-298322 A

FIG. 6 is a diagram showing an actual refrigeration cycle of the air refrigerant refrigeration apparatus. As shown in FIG. 6, in an actual refrigeration cycle, the compression stroke (a → b) of the compressor 106 and the expansion stroke (d → e) of the expander 108 are not isentropic strokes, but are Δi ₁ and Δi _{2, respectively.} Only the process of increasing the entropy, that is, the irreversible process.

  Therefore, as disclosed in Patent Documents 1 to 3, a defrost method in which high-pressure high-temperature air refrigerant on the discharge side of the compressor is bypassed the expander and flows to the frosting area on the downstream side of the chamber to be cooled during defrost operation. Then, as the air refrigerant is circulated, the air refrigerant temperature after the discharge from the compressor rises abnormally, making it difficult to control the temperature of the air refrigerant. As a result, it may be difficult to continue the defrost operation.

  Further, as disclosed in Patent Document 1 (FIG. 2), the defrost that circulates the high-pressure and high-temperature air refrigerant on the compressor discharge side through the expander to low-pressure and low-temperature and circulates in the frosting area on the downstream side of the chamber to be cooled. In this method, it is necessary to control the compressor capacity and the amount of cooling water in the cooling water circuit while monitoring the temperature of the refrigerant on the discharge side of the compressor and the temperature of the piping system in the frosting area. Good defrost operation is not possible.

  An object of the present invention is to enable efficient defrosting operation with reduced energy consumption in an air refrigerant refrigeration apparatus in view of the problems of the related art.

  In order to achieve this object, a defrosting method for an air refrigerant refrigeration apparatus according to the present invention includes a compressor and an expander connected to a single output shaft of a driving device, a cooler for cooling the compressor discharge side air refrigerant, and And a heat recovery unit that exchanges heat between the cooled air refrigerant and the return air refrigerant that has exited the cooled chamber, and the air refrigerant after the heat recovery is decompressed by an expander and is supplied to the cooled chamber. In the apparatus defrosting method, when the compressor suction pressure, the air refrigerant temperature at the compressor outlet, and the air refrigerant temperature in the frosting area on the expander outlet side are monitored, and when the compressor suction pressure falls below the set pressure The defrost operation is performed to bypass the air refrigerant from the cooler outlet side to the expander inlet side, and to bypass the air refrigerant from the expander outlet side to the cooled chamber outlet side, thereby interrupting the supply of the cooling medium to the cooler or By adjusting A defrosting step of melting frost in the frosting zone using enthalpy calorie corresponding to all or part of the loss power of the compressor and expander, and the air refrigerant temperature at the compressor outlet is below the allowable temperature The defrosting process is ended when the air refrigerant temperature in the frosting zone reaches a plus temperature frosting melting end temperature near 0 ° C. while maintaining the set temperature.

  In the method of the present invention, the air refrigerant is bypassed from the cooler outlet to the expander inlet and the air refrigerant is expanded while monitoring the compressor suction pressure, the air refrigerant temperature at the compressor outlet, and the air refrigerant temperature in the frosting area. Defrost operation is performed to bypass from the machine outlet side to the cooled chamber outlet side. At this time, by blocking or adjusting the supply of the cooling medium to the cooler, the air refrigerant temperature at the time of the defrost operation is not increased more than necessary, and all or part of the loss power of the compressor and the expander is reduced. Defrost operation using only the corresponding enthalpy calorie becomes possible.

  The “frosting area at the outlet side of the expander” refers to a region along the low temperature side refrigerant path that bypasses the cooled chamber from the vicinity of the impeller of the expander and the outlet pipe and reaches the low temperature side pipe of the heat recovery unit. .

  In addition, from past tests and experiences, the correlation between the air refrigerant temperature in the frosting area on the outlet side of the expander and the air refrigerant temperature at the end of frost melting is known. Then, when the air refrigerant temperature in the frosting area on the outlet side of the expander reaches the frosting and melting end temperature having a plus temperature in the vicinity of 0 ° C., the defrosting operation is ended. As a result, it is possible to realize energy-saving and efficient defrosting operation that does not consume extra power while maintaining the air refrigerant temperature at the compressor outlet below the allowable temperature. In addition, when measuring the air refrigerant temperature of the frosting area by the side of an expander, the optimal location is selected for the attachment position of a temperature sensor by a prior experiment. Further, “plus temperature near 0 ° C.” refers to a range of 2 to 7 ° C., for example.

  According to the method of the present invention, since the defrost process can be completed in a short time, the defrost process can be performed frequently. Therefore, it is not always necessary to provide a frost trap in the frosting area on the expander outlet side.

  In the method of the present invention, preferably, when the frost thawing end temperature is reached, supply of the cooling medium is started by the cooler, and when the air refrigerant temperature on the outlet side of the expander converges to a plus temperature near 0 ° C., defrosting is performed. It is preferable to end the process. As a result, the defrosting operation can be performed with the minimum amount of energy without causing an abnormally high temperature of the air refrigerant at the compressor outlet side and without consuming excess heat. In addition, by setting the air refrigerant temperature at the outlet side of the expander to a positive temperature near 0 ° C. and finishing the defrost operation, when returning to the normal refrigeration operation, the time and energy required for the return (power of the drive motor) are wasted. It will not be consumed.

  When performing the defrost operation by the method of the present invention, for example, when the air refrigerant temperature at the cooler outlet becomes higher just before the end of the defrost operation in summer, the air refrigerant temperature at the expander outlet is also a positive temperature near 0 ° C. It becomes considerably higher and wastes energy. Such a situation occurs when the cooling water temperature in summer is too high. In this case, the amount of cooling water supplied to the cooler is maximized to minimize waste. Further, when the air refrigerant temperature at the outlet side of the expander becomes equal to or lower than the positive temperature near 0 ° C., the amount of the cooling medium supplied to the cooler is decreased to increase the air refrigerant temperature to a positive temperature near 0 ° C. Like that.

  In the method of the present invention, even when the supply of the cooling medium to the cooler is maximized during the defrosting process, when the compressor outlet side air refrigerant temperature exceeds the allowable temperature, the compressor rotation speed is decreased to reduce the compressor outlet side air. The refrigerant temperature may be maintained at a set value that is equal to or lower than the allowable temperature. In this way, by using both the cooling medium supply to the cooler and the rotation speed control of the compressor, the compressor outlet side air refrigerant temperature is maintained below the allowable temperature even in a high temperature environment such as summer. be able to.

  In the method of the present invention, during the defrost process, when the air refrigerant temperature in the frosting area exceeds the set temperature due to the surrounding environment, supply of the cooling medium to the cooler is started, and the supply amount of the cooling medium is controlled. The expander outlet side air refrigerant temperature may be maintained at a set temperature. This enables efficient defrost operation with reduced energy consumption that does not consume extra power. For example, a positive temperature in the vicinity of 0 ° C. is employed as the set temperature.

  In the defrosting process, even if the expander outlet-side air refrigerant temperature is rising, there is a possibility that unmelted frost forms. In order to avoid this, it is necessary to move the installation location of the temperature sensor provided in the frosting area on the expander outlet side to the unmelted frosting part so that the final frosting part temperature can be measured. There is.

  The defroster of the air refrigerant refrigeration apparatus of the present invention that can be used directly for the implementation of the method of the present invention cools the compressor and the expander connected to the single output shaft of the drive unit, and the compressor discharge side air refrigerant. And a heat recovery unit that exchanges heat between the cooled air refrigerant and the return air refrigerant that has exited the cooled chamber, and the air refrigerant after the heat recovery is decompressed by an expander and supplied to the cooled chamber. In a defrost device of an air refrigerant refrigeration system, a pressure sensor that detects a compressor suction pressure, a first temperature sensor that detects an air refrigerant temperature on the compressor outlet side, and an air refrigerant temperature in a frosting area on the expander outlet side A second temperature sensor for detecting air, a first bypass passage having a valve for bypassing the air refrigerant on the cooler outlet side to the cooled chamber, and a valve for bypassing the air refrigerant on the expander outlet side to the cooled chamber outlet side Intervening second bypass and compressor suction When the pressure is lower than the set pressure, the air refrigerant is passed through the first bypass path and the second bypass path to perform the defrost operation, while maintaining the air refrigerant temperature at the compressor outlet at a set temperature lower than the allowable temperature, And a controller that terminates the defrost process when the air refrigerant temperature in the frosting zone reaches a melting end temperature of plus temperature in the vicinity of 0 ° C.

  In the device of the present invention, while monitoring the compressor suction pressure, the air refrigerant temperature at the compressor outlet, and the air refrigerant temperature in the frosting area on the expander outlet side, the air refrigerant is bypassed from the cooler outlet to the expander inlet. Then, defrost operation is performed to bypass the air refrigerant from the expander outlet to the cooled chamber outlet. This makes it possible to perform a defrost operation using only the enthalpy heat amount corresponding to the loss power of the compressor and the expander without increasing the air refrigerant temperature during the defrost operation more than necessary.

  Further, when the air refrigerant temperature in the frosting area on the expander outlet side reaches a frost thawing end temperature having a positive temperature near 0 ° C., the defrost operation is ended, so the air refrigerant temperature at the compressor outlet It is possible to realize an efficient defrosting operation that saves energy and does not consume extra power while maintaining the temperature below the allowable temperature.

  According to the device of the present invention, since the defrost operation can be completed in a short time, the defrost operation can be performed frequently. Therefore, it is not always necessary to provide a frost trap in the frosting area on the expander outlet side.

  In the device according to the present invention, when the air refrigerant temperature in the frosting area reaches the melting end temperature during the defrost operation, the controller starts supplying the cooling medium with the cooler, and the detected value of the second temperature sensor is It may be controlled so that the defrosting process is terminated when the temperature converges to a positive temperature in the vicinity of 0 ° C. As a result, the defrosting operation can be performed with the minimum amount of energy without causing an abnormally high temperature of the air refrigerant at the compressor outlet side and without consuming excess heat. In addition, by setting the air refrigerant temperature at the outlet side of the expander to a plus temperature near 0 ° C. and finishing the defrost operation, when returning to the normal refrigeration mode, the time and energy required for the return (power of the drive motor) are wasted. It will not be consumed.

  According to the method of the present invention, the compressor and the expander connected to the single output shaft of the driving device, the cooler that cools the compressor discharge side air refrigerant, and the cooled air refrigerant exits the cooled chamber. In the defrost method of the air refrigerant type refrigeration apparatus, which includes a heat recovery device that exchanges heat with the return air refrigerant, decompresses the air refrigerant after heat recovery with an expander, and supplies the air refrigerant to the cooled chamber. The process of monitoring the air refrigerant temperature at the outlet and the air refrigerant temperature in the frosting area on the expander outlet side, and when the compressor suction pressure falls below the set pressure, the air refrigerant is transferred from the cooler outlet side to the expander inlet side. And the defrost operation that bypasses the air refrigerant from the outlet side of the expander to the outlet side of the cooled chamber, and cuts or adjusts the supply of the cooling medium to the cooler, thereby reducing the loss power of the compressor and the expander. Enthalpy equivalent to A defrost process in which frost is melted using all or part of the quantity, and the air in the frost area on the expander outlet side is maintained while maintaining the air refrigerant temperature at the compressor outlet at a set temperature lower than the allowable temperature. Since the defrosting process is terminated when the refrigerant temperature reaches a positive frost thawing end temperature near 0 ° C., the air refrigerant during the defrost operation is maintained while maintaining the compressor discharge side temperature below the allowable temperature. It is possible to perform defrost operation using only the enthalpy calorific value corresponding to the loss power of the compressor and expander without raising the temperature more than necessary, and energy efficient and efficient defrost operation that does not consume extra power. Can be realized. Therefore, it is not always necessary to provide a frost trap in the frosting area on the expander outlet side.

  According to the device of the present invention, the compressor and the expander connected to the single output shaft of the drive device, the cooler for cooling the compressor discharge side air refrigerant, and the cooled air refrigerant from the chamber to be cooled. A pressure that detects a compressor suction pressure in an air refrigerant refrigeration system that includes a heat recovery unit that exchanges heat with the returned return air refrigerant, decompresses the air refrigerant after heat recovery with an expander, and supplies the decompressed air refrigerant to a chamber to be cooled A first temperature sensor for detecting an air refrigerant temperature on the compressor outlet side, a second temperature sensor for detecting an air refrigerant temperature in a frosting area on the expander outlet side, and an air refrigerant on the cooler outlet side A first bypass passage with a valve that bypasses the compressor inlet side, a second bypass passage with a valve bypass that bypasses the air refrigerant on the outlet side of the expander to the outlet side of the chamber to be cooled, and the compressor suction pressure is lower than the set pressure When the air refrigerant reaches the first bypass path and the second bypass The defrosting operation is performed through the flow path, and the air refrigerant temperature in the frosting area on the expander outlet side is melted to a positive temperature near 0 ° C while maintaining the air refrigerant temperature at the compressor outlet at a set temperature lower than the allowable temperature. And a controller that terminates the defrost process when the end temperature is reached. In addition to obtaining the same effects as the method of the present invention, the controller can automate the defrost operation.

1 is a system diagram of an air refrigerant refrigeration apparatus according to a first embodiment of the method and apparatus of the present invention. It is a block diagram of the control device of the first embodiment. It is a systematic diagram of the air refrigerant refrigeration apparatus which concerns on 2nd Embodiment of this invention method and apparatus. It is a systematic diagram of a conventional general air refrigerant refrigeration apparatus. It is a diagram which shows the ideal reverse Brayton cycle in an air refrigerant refrigeration apparatus. It is a diagram which shows the actual reverse Brayton cycle in an air refrigerant refrigeration apparatus.

  Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this embodiment are not intended to limit the scope of the present invention to that unless otherwise specified.

(Embodiment 1)
1st Embodiment of the method and apparatus of this invention is described based on FIG.1 and FIG.2. In FIG. 1, in the air refrigerant refrigeration apparatus 10 </ b> A of this embodiment, refrigeration cycle components are interposed in the refrigerant circulation path 12. A compressor 16 and an expander 18 are connected to a single output shaft 14a of the drive motor 14, and the compressor 16 and the expander 18 are driven coaxially. The high-pressure and high-temperature air refrigerant discharged from the compressor 16 is primarily cooled by the primary cooler 22. A cooling water circulation path 20 is connected to the primary cooler 22. In the cooling water circulation path 20, a cooling water pump 26 and a water flow valve 28 whose flow rate can be adjusted are provided, and the cooling water is circulated in the direction of the arrow by the cooling water pump 26. The cooling water is cooled in the cooling tower 24, and heat exchange with the air refrigerant is performed in the primary cooler 22 to cool the air refrigerant.

  The air refrigerant cooled by the primary cooler 22 is heat-exchanged by the heat recovery device 30 with the air refrigerant returning from the chamber to be cooled 32 and further cooled. The air refrigerant cooled by the heat recovery device 30 is expanded by the expander 18 to become low-pressure low-temperature air, and is supplied to the air outlet 320 in the chamber to be cooled 32. The to-be-cooled chamber 32 is configured by, for example, a freezer or a freezer. The air refrigerant after freezing the article to be cooled stored in the room 32 to be cooled is sucked from the air intake 322, and a part of fine ice contained in the air refrigerant is collected by the frost trap 34. The The air refrigerant that has exited the frost trap 34 is heat-exchanged with the outlet side air refrigerant of the primary cooler 22 by the heat recovery device 30, cools the outlet side air refrigerant, and then is sent to the compressor 16.

  Also, a first bypass path 36 that bypasses the heat recovery device 30 and connects the outlet side of the primary cooler 22 and the inlet side of the expander 18, and the outlet side of the expander 18 that bypasses the cooled chamber 32 A second bypass path 38 that connects the inlet side of the frost trap 34 is provided. A suction pressure adjustment valve 160 that adjusts the suction pressure is provided at the inlet of the compressor 16. A drain valve 300 is provided in the outlet side refrigerant circulation path 12 of the heat recovery unit 30, and drain valves 12 a and 12 b are provided in the inlet side and outlet side refrigerant circulation paths 12 of the expander 18, respectively. A drain valve 340 is provided below the frost trap 34. A stop valve 40, an inlet valve 42 and an outlet valve 44 are interposed in the refrigerant circulation path 12, a bypass valve 46 is interposed in the first bypass path 36, and a bypass valve 48 is interposed in the second bypass path 38. It is installed.

  In addition, a pressure sensor 50 that detects an outlet side refrigerant pressure of the compressor 16, a temperature sensor 52 that detects an outlet side refrigerant temperature of the compressor 16, and a temperature sensor 54 that detects an outlet side refrigerant temperature of the expander 18. Is provided. The temperature sensor 54 may be provided in the frost trap 34 instead of the expander outlet side. In other words, the temperature sensor 54 is preferably installed in a place where frost formation is likely to remain from the past operation result.

  Further, as shown in FIG. 2, a controller 56 for controlling the operation of the air refrigerant refrigeration apparatus 10A is provided. The controller 56 receives the detection values of the pressure sensor 50 and the temperature sensors 52 and 54, controls the rotational speeds of the drive motor 14 and the cooling water pump 26 based on these detection values, and allows the flow rate to be adjusted. The opening degree of the valve 28 is controlled, and the opening / closing operation of the opening / closing valves 40, 42, 44, 46 and 48 is controlled.

  In such a configuration, the compressor outlet refrigerant pressure is detected by the pressure sensor 50, and when the detected value decreases to the set value Pcs, the normal refrigeration operation is stopped and the defrost operation is started. In the defrost operation, first, the rotation speed of the drive motor 14 is controlled so that the compressor outlet refrigerant temperature becomes the set value Tcs. Next, the bypass valve 48 is fully opened, and the inlet valve 42 and the outlet valve 44 of the chamber to be cooled 32 are fully closed. Further, the bypass valve 46 is fully opened and the stop valve 40 is fully closed. Thereafter, the cooling water pump 26 is stopped and the water flow valve 28 is closed.

When the water flow valve 28 is closed, the refrigerant temperature at the outlet of the primary cooler 22 matches the refrigerant temperature at the outlet of the compressor 16. This uncooled high-temperature air refrigerant is directly introduced into the expander 18 through the first bypass passage 36. This expansion stroke is indicated by an expansion stroke (b → g ₂ ) in FIG. Air refrigerant of the expander 18 outlet is in a state _{g 2.} The hot air refrigerant at the outlet of the expander 18 is bypassed directly to the inlet side of the frost trap 34 through the second bypass passage 38. As a result, the melting of the frost in the vicinity of the impeller of the expander 18 and the outlet side piping, the frost trap 34, the low temperature side frosting region of the heat recovery unit 30, and the low temperature side refrigerant circulation path 12 in which these devices are provided progresses. To do.

In FIG. 6, the refrigerant temperature (compressor inlet temperature) at the low temperature side outlet a of the heat recovery unit 30 gradually increases as the defrost operation proceeds. That is, since the water flow through the cooling water circulation path 20 is cut off, the heat radiation to the outside of the refrigerant circulation path 12 is zero during the defrost operation. Therefore, the amount of heat corresponding to the constant enthalpy difference (ΔH = Hg ₂ −Ha) is always input from the drive motor 14 to the frosting area extending from the air refrigerant through the frost trap 34 through the frost trap 34 from the outlet of the expander 18. . Therefore, the refrigerant temperature at the compressor inlet gradually increases.

  If the refrigerant temperature at the compressor inlet rises, the refrigerant temperature at the compressor outlet b and the refrigerant temperature at the expander outlet e also rise. In other words, the entire refrigeration cycle during the defrost operation shifts to the high temperature side. It is necessary to suppress the refrigerant temperature at the compressor outlet to an allowable temperature or lower. Therefore, the compressor outlet refrigerant temperature set value Tcs that is set below the allowable temperature is set, and the air refrigerant is maintained by the controller 56 so that the outlet side air refrigerant temperature of the compressor 16 is maintained below the set value Tcs. The operation of the refrigeration system 10A is controlled.

  In this control method, first, the amount of cooling water supplied to the primary cooler 22 is controlled, and even when the amount of cooling water to the primary cooler 22 is maximized, if the compressor outlet refrigerant temperature set value Tcs is exceeded, the compressor 16 The number of revolutions is decreased, and the outlet refrigerant temperature of the compressor 16 is set to a set value Tcs or less. The adjustment of the cooling water amount is sufficient except during the summer, and the outlet refrigerant temperature of the compressor 16 is controlled below the set value Tcs by using the adjustment of the cooling water and the rotation speed control of the compressor 16 also in the summer. it can.

  In the defrosting method disclosed in Patent Documents 2 and 3, that is, the defrosting method in which the air refrigerant at the compressor outlet is introduced into the frosting area without passing through the expander, the refrigerant at the compressor outlet as the defrost operation proceeds. The temperature rises abnormally, making it difficult to control the temperature of the air refrigerant. As a result, it may be difficult to continue the defrost operation.

  By defrosting operation, the place and temperature at which all frost formation in the frost formation area is finally completely melted are set in advance based on knowledge obtained from past tests and the like. The temperature sensor 54 is preferably installed at this location. This melting end temperature set value Tts is a plus temperature in the vicinity of 0 ° C. Since the defrost load decreases as the defrost process proceeds, the compressor inlet side refrigerant temperature rises and the expander outlet side refrigerant temperature also rises. In order to make the detection value of the temperature sensor 54 reach the set value Tts, automatic control for gradually increasing the coolant flow rate of the primary cooler 22 is necessary. The time when the expander outlet-side refrigerant temperature reaches the set value Tts is determined as the end of melting of all frost.

Simultaneously with the completion of all frosting, the cooling water is started to flow into the primary cooler 22. Cooling water flow is started, and the flow rate is controlled so that the detected value of the temperature sensor 54 (expander outlet side refrigerant temperature) converges to the set value Tts. That is, the cycle (g ₂ → b → c → g → g ₂ ) in FIG. 6 is formed. Then, the convergence operation is continued so that the detection value of the temperature sensor 54 is stabilized at the set value Tts.

The compression / expansion cycle at the end of the defrost operation is (g → b ₁ → c → g) in FIG. Since the defrost load is zero, the compressor inlet point and the expander outlet point coincide at point g. That is, the refrigerant temperature at the compressor inlet point, the refrigerant temperature at the expander outlet point, and the temperature at the three points of the set value Tts are the same. Expander entry point b in the defrost operation start time, the processing proceeds to a point b ₁ in the defrosting operation end point. Similarly compressor inlet point a moves to the point g, the expander exit point g ₂ moves to the point g. In FIG. 6, an expansion stroke (c ₁ → g ₁ ) indicates an expansion stroke in which the expander outlet refrigerant temperature becomes 0 ° C.

  In this way, by performing the convergence operation, it is possible to prevent wasteful consumption of time and energy required for the return (power of the drive motor 14) when returning to the normal refrigeration operation. In summer, when the outlet refrigerant temperature of the primary cooler 22 becomes high and the expander outlet refrigerant temperature becomes considerably higher than 0 ° C., useless defrost energy is consumed. In this case, the amount of water flow to the primary cooler 22 is maximized to minimize waste.

  When the expander outlet refrigerant temperature is controlled in the vicinity of 0 ° C., the compressor outlet refrigerant temperature also decreases. When the compressor outlet refrigerant temperature falls below the set value Tcs, the controller 56 increases the compressor rotation speed so that the compressor outlet refrigerant temperature becomes the set value Tcs.

  Simultaneously with the completion of the defrost process, the drainage / drying process is started. In the drainage / drying process, first, the drain valves 12a, 12b, 300 and 340 are opened, the molten water is discharged out of the system, and after confirming the elimination of the molten water, all the drain valves are closed. Next, air refrigerant is circulated through the refrigerant circulation path 12 and the second bypass path 38 to dry the refrigerant circulation path 12. After drying is confirmed, the drainage / drying process is terminated. The method for confirming the end of drainage and the end of drying is determined by prior experiments. For example, a time limit method using preset drainage time and drying time may be used.

  When the drainage / drying process is completed, as a preparatory process for returning to the normal refrigeration operation, a refrigeration return process for precooling a portion where the temperature during the defrost process has increased is performed. If the refrigeration return process is omitted, the high-temperature refrigerant at the outlet of the expander is supplied to the cooled chamber 32. As with the defrost process, it is desirable to complete the refrigeration return process in as short a time as possible and quickly shift to the normal refrigeration operation.

  In the refrigeration return process, the stop valve 40 is fully opened, the bypass valve 46 is fully closed, and the bypass valve 48 is fully opened. The compressor speed is the rated speed, and the water flow valve 28 of the primary cooler 22 is fully open. The outlet refrigerant of the primary cooler 22 is introduced into the heat recovery unit 30 and then introduced into the expander 18. Next, the expander outlet refrigerant is passed through the second bypass passage 38 to bypass the cooled chamber 32. The expander outlet refrigerant temperature gradually decreases in the refrigeration return process, and the refrigeration return process ends when the detected value of the temperature sensor 54 reaches the rated temperature during the refrigeration operation.

  After the freezing return process, normal freezing operation is started. In the normal refrigeration operation, the bypass valves 46 and 48 are closed, and the stop valve 40, the inlet valve 42 and the outlet valve 44 are opened.

The defrost process of the present embodiment uses an enthalpy heat amount ΔH corresponding to the process (g ₂ → a) in the defrost process (a → b → g ₂ → a) in FIG. If the heat insulation efficiency and mechanical efficiency of the compressor 16 and the expander 18 are about 83%, about 30% of the compression power can be used for defrosting. Therefore, a sufficient amount of heat can be secured as compared with the conventional defrost method using an electric heater. Therefore, defrosting is possible using the power of the drive motor 14 without requiring special equipment such as an electric heater. Further, not only the defrost around the installation place like the electric heater, but also the entire frosting area of the low-temperature side refrigerant circulation path 12 can be defrosted all at once.

  Further, according to the present embodiment, the detected value of the pressure sensor 50 is monitored, and when the detected value falls below the set value, the controller 56 can automatically start the defrost operation. Moreover, at the time of defrost operation, the adjustment of the amount of cooling water to the primary cooler 22 and the rotation speed control of the compressor 16 are used in combination, so that the outlet refrigerant temperature of the compressor 16 does not exceed the set value Tcs below the allowable temperature. You can drive like that. Further, when the outlet refrigerant temperature of the expander 18 reaches the melting end temperature set value Tts of plus temperature near 0 ° C., the frost thawing is immediately terminated, and thereafter, the operation of converging to the melting end temperature is performed. Therefore, it is possible to quickly shift to the refrigeration return process in the next step without wasting energy and motor power in the defrost operation.

By passing the air refrigerant through the expander 18 during the defrost operation, the entire frosting area in the low temperature region of the refrigerant circulation path 12 including the vicinity of the impeller of the expander 18 and the outlet pipe can be thoroughly defrosted. Furthermore, since the refrigerant temperature at the outlet of the expander 18 is the same as the temperature of the room to be cooled at the time of shifting to the normal refrigeration operation, the refrigerant can be immediately supplied to the room to be cooled.
Further, according to the present embodiment, since the defrost operation time can be shortened, the frequency of the defrost operation can be increased, and in some cases, the frost trap 34 can be omitted.

(Embodiment 2)
Next, a second embodiment of the method and apparatus of the present invention will be described with reference to FIG. The air refrigerant refrigeration apparatus 10B of the present embodiment is an example in the case of using a brine cooling apparatus 60 as a room to be cooled. In the brine cooling device 60, a meandering brine passage 602 is disposed through the inside of the casing 600 of the brine cooling device 60 from the outside. A brine inlet valve 604 is provided at the inlet of the brine passage 602, and a brine outlet valve 606 is provided at the outlet of the brine passage 602. A drain valve 608 is provided in the refrigerant circulation path 12 at a position below the casing 600. The configuration other than the brine cooling device 60 is the same as that of the first embodiment, and the same reference numerals are assigned to the same devices or members.

  In such a configuration, the brine flowing through the brine passage 602 is cooled by exchanging heat with the air refrigerant inside the casing 600, and the cooled brine is sent to the use destination (the refrigeration load side). When the detection value of the pressure sensor 50 reaches the set value Pcs, the normal refrigeration operation ends and the defrost operation starts.

  During the defrost operation, the brine inlet valve 604 and the brine outlet valve 606 are first closed while the inlet valve 42 and the outlet valve 44 are fully opened. Next, the rotation speed of the compressor 16 is controlled so that the outlet refrigerant temperature of the compressor 16 is maintained at the set value Tcs. Next, after the bypass valve 46 is fully opened, the stop valve 40 is fully closed, then the cooling water pump 26 is stopped, and the water flow valve 28 is closed. The defrost operation is started when the bypass valve 46 is opened. Due to the defrosting operation, frost melting proceeds from the low temperature portion of the expander 18 to the low temperature side frost region of the heat recovery device 30 and the refrigerant circulation path 12 therebetween.

  When the detection value of the temperature sensor 54 reaches the melting end temperature, water flow through the cooling water circulation path 20 is started, and the detection value of the temperature sensor 54 causes the outlet refrigerant temperature of the expander 18 to converge to the set value Tcs. , Control the amount of cooling water flow. The defrost operation is terminated when the expander outlet refrigerant temperature converges to the set value Tcs.

  In the next drainage / drying step, the drain valves 12a, 300, 340 and 608 are opened to discharge the molten water to the outside. After the discharge is completed, a circulating operation of the air refrigerant is performed with these drain valves closed, and the low-temperature side cooling water circulation path 20 including the low-temperature side cooling water circulation path 20 and the brine path 602 in the casing 600 is interposed. Dry the molten water adhering to the equipment. This completes the drainage / drying process.

  In the next freezing return step, first, the water flow valve 28 is fully opened. Next, the stop valve 40 is fully opened, the bypass valve 46 is fully closed, and the rotational speed of the drive motor 14 is set to the rated rotational speed. In this state, the expander outlet refrigerant temperature gradually decreases, and when the expander outlet refrigerant temperature reaches the rated temperature of the normal refrigeration operation, the refrigeration return process is terminated.

  In the normal refrigeration operation, the normal refrigeration operation is started with the brine inlet valve 604 and the brine outlet valve 606 closed, and when the detected value of the temperature sensor 54 reaches the rated temperature, the brine inlet valve 604 and the brine outlet valve 606 is fully opened, and a brine pump (not shown) provided in the brine passage 602 is activated. The temperature sensor 54 may be provided on the outer wall of the brine passage 602 inside the casing 600.

  According to this embodiment, in addition to being able to obtain the same operational effects as in the first embodiment, defrosting of the brine passage 602 disposed inside the casing 600 of the brine cooling device 60 can be performed simultaneously, and the brine There is no need to provide a defrost process only for the passage 602.

  ADVANTAGE OF THE INVENTION According to this invention, in an air-refrigerant-type refrigeration apparatus, efficient defrost driving | operation with energy saving is enabled.

10A, 10B Air refrigerant refrigeration apparatus 12, 102 Refrigerant circulation path 12a, 12b Drain valve 14, 104 Drive motor 14a, 104a Output shaft 16, 106 Compressor 160 Suction pressure adjusting valve 18, 108 Expander 20, 110 Cooling water circulation path 22, 112 Primary cooler 24, 114 Cooling tower 26, 116 Cooling water pump 28, 118 Flow valve 30, 120 Heat recovery device 300 Drain valve 32, 122 Cooled chamber 320 Air outlet 322 Air inlet 34, 124 Frost Trap 340 Drain valve 36 First bypass path 38 Second bypass path 40 Stop valve 42 Inlet valve 44 Outlet valve 46, 48 Bypass valve 50 Pressure sensor 52, 54 Temperature sensor 56 Controller 60 Brine cooling device 600 Casing 602 Brine passage 604 Brine inlet Valve 6 6 brine outlet valve 608 drain valve Pcs compressor outlet refrigerant pressure set value Tcs compressor outlet refrigerant temperature setpoint Tts expander outlet side refrigerant temperature set point

Claims (6)

A compressor and an expander connected to a single output shaft of the drive device, a cooler for cooling the compressor discharge side air refrigerant, and heat exchange of the cooled air refrigerant with the return air refrigerant coming out of the chamber to be cooled. In the defrost method of the air refrigerant type refrigeration apparatus comprising a heat recovery device, decompressing the air refrigerant after heat recovery with an expander, and supplying the air refrigerant to the chamber to be cooled,
Monitoring the compressor suction pressure, the compressor outlet air refrigerant temperature, and the expander outlet frost area air refrigerant temperature;
When the compressor suction pressure falls below the set pressure, defrost operation is performed to bypass the air refrigerant from the cooler outlet side to the expander inlet side and to bypass the air refrigerant from the expander outlet side to the cooled chamber outlet side. The defrosting step of melting the frost in the frosting zone using the enthalpy calorific value corresponding to all or part of the loss power of the compressor and the expander by shutting off or adjusting the supply of the cooling medium to the cooler And consists of
The defrost process is terminated when the air refrigerant temperature in the frosting zone reaches a frost thawing end temperature that is a plus temperature near 0 ° C. while maintaining the compressor outlet side air refrigerant temperature at a set temperature lower than the allowable temperature. An air refrigerant refrigeration apparatus defrosting method.   When the air refrigerant temperature in the frost formation area reaches the frost thawing end temperature, supply of a cooling medium is started by a cooler, and when the air refrigerant temperature converges to the frost thawing end temperature, the defrost process is ended. The defrosting method for an air refrigerant refrigeration apparatus according to claim 1.   Even if the supply of the cooling medium to the cooler is maximized during the defrost process, if the compressor outlet side air refrigerant temperature exceeds the allowable temperature, the compressor rotation speed is decreased to allow the compressor outlet side air refrigerant temperature. The defrost method for an air refrigerant refrigeration apparatus according to claim 1 or 2, wherein the set value is maintained at a temperature or lower.   During the defrosting process, when the air refrigerant temperature in the frosting area exceeds a set temperature due to the surrounding environment, supply of the cooling medium to the cooler is started, and the supply amount of the cooling medium is controlled to expand the outlet side The defrost method for an air refrigerant refrigeration apparatus according to any one of claims 1 to 3, wherein the air refrigerant temperature is maintained at a set temperature. A compressor and an expander connected to a single output shaft of the drive device, a cooler for cooling the compressor discharge side air refrigerant, and heat exchange of the cooled air refrigerant with the return air refrigerant coming out of the chamber to be cooled. In the defrost device of the air refrigerant type refrigeration apparatus comprising a heat recovery device, depressurizing the air refrigerant after heat recovery with an expander, and supplying it to the cooled chamber,
A pressure sensor for detecting the compressor suction pressure;
A first temperature sensor for detecting an air refrigerant temperature on the compressor outlet side;
A second temperature sensor for detecting an air refrigerant temperature in the frosting area on the outlet side of the expander;
A first bypass passage with a valve interposed for bypassing the air refrigerant on the cooler outlet side to the expander inlet side;
A second bypass passage with a valve interposed for bypassing the air refrigerant on the outlet side of the expander to the outlet side of the cooled chamber;
When the compressor suction pressure falls below the set pressure, the air refrigerant is passed through the first bypass passage and the second bypass passage to perform defrost operation, and the air refrigerant temperature at the compressor outlet is maintained at a set temperature lower than the allowable temperature. And a controller that terminates the defrost process when the temperature of the air refrigerant in the frosting zone reaches a frost melting end temperature of plus temperature near 0 ° C. Equipment defrost device.   During the defrost operation, when the air refrigerant temperature in the frosting area reaches the frost melting end temperature, the controller starts supplying the cooling medium with the cooler, and the detected value of the second temperature sensor is the frost melting end. 6. The defrost apparatus for an air refrigerant refrigeration apparatus according to claim 5, wherein the defrost process is controlled to end when the temperature has converged.

Images