CN108369046B - Refrigeration cycle device - Google Patents
Refrigeration cycle device Download PDFInfo
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- CN108369046B CN108369046B CN201580085093.5A CN201580085093A CN108369046B CN 108369046 B CN108369046 B CN 108369046B CN 201580085093 A CN201580085093 A CN 201580085093A CN 108369046 B CN108369046 B CN 108369046B
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- refrigerant
- flow rate
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- refrigeration cycle
- defrosting
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B47/00—Arrangements for preventing or removing deposits or corrosion, not provided for in another subclass
- F25B47/02—Defrosting cycles
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- Air Conditioning Control Device (AREA)
Abstract
Provided is a refrigeration cycle device which has high reliability by reducing the amount of liquid returned to a compressor while shortening the hot-gas defrosting time. The refrigeration cycle device of the present invention includes a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in series by pipes. The refrigeration cycle device is provided with: a hot gas bypass pipe directly connecting the discharge side of the compressor to the evaporator; a flow rate regulator provided in the hot gas bypass pipe and regulating a flow rate of the refrigerant; a refrigerant state detection means for detecting a discharge superheat of the refrigerant discharged from the compressor and a suction pressure of the compressor; and a defrosting control means for closing the flow rate adjuster during the normal cooling operation, and increasing or decreasing the flow rate of the refrigerant by the flow rate adjuster during the defrosting operation based on the discharge superheat and the suction pressure detected by the refrigerant state detection means. The defrosting control means controls the flow rate adjuster to cause the refrigerant at a first refrigerant flow rate to flow through the hot-gas bypass pipe when a defrosting operation is started, and controls the flow rate adjuster to increase the amount of the refrigerant flowing through the hot-gas bypass pipe in comparison with the first refrigerant flow rate when the discharge superheat is higher than a set superheat and the suction pressure is lower than a set pressure during the defrosting operation.
Description
Technical Field
The present invention relates to a refrigeration cycle apparatus that performs hot-gas defrosting.
Background
In a refrigeration cycle apparatus, in order to remove frost generated in an evaporator, there is known a hot gas defrosting method in which frost is removed by flowing a high-temperature and high-pressure gas refrigerant discharged from a compressor into the evaporator. As a hot-air defrosting method, there is the following method: a hot gas bypass pipe is provided between the compressor and the evaporator, and during defrosting, a high-temperature and high-pressure gas refrigerant discharged from the compressor is caused to directly flow into the evaporator via the hot gas bypass pipe. Conventionally, in hot-gas defrosting, the compressor discharge superheat and the compressor discharge pressure are controlled as targets. For example, patent document 1 discloses control for detecting a compressor discharge superheat degree and a compressor discharge pressure and switching a hot gas circuit.
In addition, for example, in patent document 2, a control valve in which a two-way valve a and a two-way valve B connected in series to a capillary tube are connected in parallel is provided in a hot gas bypass path between a compressor and an evaporator. Then, the outdoor unit outlet pipe temperature is detected, the two-way valve B with the capillary tube is first opened, and then the other valves are opened after a predetermined time has elapsed.
Prior art documents
Patent document
Patent document 1: japanese patent laid-open No. 2014-119122
Patent document 2: japanese laid-open patent publication No. 62-94766
Disclosure of Invention
Problems to be solved by the invention
However, in patent document 1, control is not performed to detect the compressor suction pressure and switch the solenoid valve. Therefore, if the compressor discharge pressure does not rise even if the suction pressure of the compressor rises, the solenoid valve is not controlled to be switched to one system, and therefore, there is a problem that the amount of liquid returned during hot gas defrosting increases.
In patent document 2, the timing at which the other two-way valve a is opened is determined based on the elapsed time. After both valves are opened, the control is performed so that the valves are not closed even if the liquid is returned to the compressor. In addition, the compressor discharge superheat is not targeted for control. Therefore, when the liquid returning to the compressor occurs in a state where the two-way valves are opened, the liquid returning cannot be avoided. Therefore, there are problems as follows: in the defrosting operation, the amount of refrigerant flowing through the hot-gas bypass pipe is suppressed to a range where liquid return to the compressor does not occur, and the defrosting operation takes time.
The present invention has been made to solve the above problems, and an object of the present invention is to reduce the hot gas defrosting time, reduce the amount of liquid returned to the compressor during hot gas defrosting, and suppress an increase in suction pressure of the compressor, thereby improving the reliability of the refrigeration cycle apparatus.
Means for solving the problems
A refrigeration cycle apparatus according to the present invention includes a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in series by pipes, and includes: a hot gas bypass pipe directly connecting the discharge side of the compressor to the evaporator; a flow rate regulator connected to the hot-gas bypass pipe and configured to regulate a flow rate of the refrigerant flowing through the hot-gas bypass pipe; a refrigerant state detection unit that detects a discharge superheat of the refrigerant discharged from the compressor and a suction pressure of the compressor; and a defrosting control unit that closes the flow rate adjuster during a normal cooling operation, and increases or decreases the flow rate of the refrigerant flowing through the hot-gas bypass pipe by the flow rate adjuster during a defrosting operation based on the discharge superheat degree and the suction pressure detected by the refrigerant state detection unit, wherein the defrosting control unit controls the flow rate adjuster to cause the refrigerant at a first refrigerant flow rate to flow through the hot-gas bypass pipe at a start of a defrosting operation, and controls the flow rate adjuster to increase the amount of the refrigerant flowing through the hot-gas bypass pipe in comparison with the first refrigerant flow rate when the discharge superheat degree is greater than a set superheat degree and the suction pressure is lower than a set pressure during the defrosting operation.
ADVANTAGEOUS EFFECTS OF INVENTION
According to the refrigeration cycle apparatus of the present invention, the flow rate of the refrigerant flowing through the hot gas bypass pipe is increased or decreased by the flow rate regulator in accordance with the discharge superheat degree and the suction pressure of the compressor during the defrosting control, and the liquid return to the compressor during the defrosting control can be reliably prevented, and the defrosting time can be shortened.
Drawings
Fig. 1 is a refrigerant circuit diagram showing a refrigeration cycle apparatus according to embodiment 1 of the present invention.
Fig. 2 is a flowchart showing an operation example of the refrigeration cycle apparatus of fig. 1.
Fig. 3 is a graph showing the relationship of the defrosting time to the temperature of the evaporator.
Fig. 4 is a flowchart showing an operation example of the refrigeration cycle apparatus of fig. 1.
Fig. 5 is a refrigerant circuit diagram showing embodiment 3 of the refrigeration cycle apparatus of the present invention.
Fig. 6 is a refrigerant circuit diagram showing embodiment 4 of the refrigeration cycle apparatus of the present invention.
Fig. 7 is a refrigerant circuit diagram showing embodiment 6 of the refrigeration cycle apparatus of the present invention.
Detailed Description
Embodiments of the present invention will be described below with reference to the drawings. Fig. 1 is a refrigerant circuit diagram showing a refrigeration cycle apparatus according to embodiment 1 of the present invention. A circuit configuration of the refrigeration cycle apparatus 100 will be described with reference to fig. 1. The refrigeration cycle apparatus 100 performs a cooling operation by a refrigeration cycle (heat pump cycle) in which a refrigerant circulates. In the refrigeration cycle apparatus 100, a refrigerant circuit is configured by connecting the compressor 1, the condensers 4a, 4b, the expansion valve, and the evaporator 7 by pipes. The refrigerant circuit is not limited to the circuit of fig. 1. In fig. 1, a circuit from the condensers 4a and 4b to the evaporator 7 is omitted. The evaporator 7 is incorporated in a cooler housing, not shown.
< compressor 1 and oil separator 2>
The compressor 1 sucks a refrigerant and compresses the refrigerant to a high-temperature and high-pressure state, and has a configuration in which, for example, the rotational speed is controlled by an inverter to control the capacity. The oil separator 2 has the following functions: the refrigerator oil component is separated from the refrigerant gas in which the refrigerator oil is present in the refrigerant discharged from the compressor 1. The refrigerating machine oil separated in the oil separator 2 is returned to the compressor 1 from a capillary tube not shown connected to the compressor 1.
< condensers 4a, 4b and evaporator 7>
The condensers 4a and 4b exchange heat between the refrigerant and air supplied from, for example, the condenser fans 5a and 5b, evaporate and vaporize the refrigerant or condense and liquefy the refrigerant, and the condensers 4a and 4b are connected to the discharge side of the oil separator 2 via the check valve 3. Although the case where two condensers 4a and 4b are provided is exemplified, it is sufficient to provide one or more condensers. The evaporator 7 performs heat exchange between air and refrigerant, and evaporates and gasifies the refrigerant. The evaporator 7 has a structure for supplying air from the blower fan 7a and promoting heat exchange.
< reservoir 8>
The accumulator 8 stores the refrigerant flowing out of the evaporator 7 and is connected to the suction side of the compressor 1. The refrigerant stored in the accumulator 8 is sucked and compressed by the compressor 1. An oil return pipe 9 is connected to the bottom side of the accumulator 8, and an oil return regulator 10 is disposed in the oil return pipe 9. The oil and a small amount of liquid refrigerant are returned to the compressor 1 through the oil return pipe 9.
< Hot gas bypass Circuit >
The refrigeration cycle apparatus 100 includes a hot-gas bypass pipe 11, a flow rate adjuster 12, and a defrosting control unit 30. The hot-gas bypass pipe 11 is connected between the compressor 1 and the evaporator 7, and allows the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 to flow directly into the evaporator 7 without passing through the condensers 4a and 4b during hot-gas defrosting.
< flow rate regulator 12>
The flow rate regulator 12 adjusts the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11, and includes, for example, a first on-off valve 12a and a second on-off valve 12 b. The flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 is adjusted by a combination of opening and closing of the first opening/closing valve 12a and the second opening/closing valve 12 b. Specifically, the first opening/closing valve 12a is a valve having a larger capacity than the second opening/closing valve 12b, and when the first opening/closing valve 12a is opened and the second opening/closing valve 12b is closed, the refrigerant of the first refrigerant flow rate flows through the hot-gas bypass pipe 11. On the other hand, when both the first opening/closing valve 12a and the second opening/closing valve 12b are opened, the refrigerant of the second refrigerant flow rate, which is larger than the first refrigerant flow rate, flows through the hot-gas bypass pipe 11.
Note that, although fig. 1 illustrates the case where the flow rate regulator 12 is constituted by the first opening/closing valve 12a and the second opening/closing valve 12b, the configuration is not limited as long as the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 can be adjusted. For example, the flow rate adjuster 12 may be constituted by three or more opening/closing valves, and may be constituted by one or more electrically operated valves capable of adjusting the refrigerant flow rate in multiple stages, or may be constituted by one or more electrically operated valves capable of continuously adjusting the opening degree.
Further, a needle valve 13 is connected in series with the first opening/closing valve 12 a. The needle valve 13 is disposed on the evaporator 7 side with respect to the first opening/closing valve 12 a. The needle valve 13 adjusts the opening degree so as to prevent the refrigerant liquid from returning to the compressor 1, and manually sets a predetermined opening degree according to, for example, an installation position so as to flow a predetermined flow rate of refrigerant during the defrosting control. Thus, even when a difference in pipe length or the like occurs due to the installation position, the opening degree (refrigerant flow rate) can be adjusted to an optimum degree according to the field situation, and the defrosting time can be shortened. In fig. 1, the case where the needle valve 13 is provided only at the rear stage of the first opening/closing valve 12a is exemplified, but the needle valve 13 may be provided also at the rear stage of the second opening/closing valve 12 b. Further, the needle valve 13 may be provided only at the rear stage of the second opening/closing valve 12 b.
< defrost control unit 30>
The operation of the flow rate regulator 12 is controlled by the defrosting control unit 30, and during the normal cooling operation, both the first opening/closing valve 12a and the second opening/closing valve 12b are closed to prevent the refrigerant from flowing through the hot-gas bypass pipe 11. On the other hand, during the defrosting operation, the first on-off valve 12a is opened and the second on-off valve 12b is closed or both the first on-off valve 12a and the second on-off valve 12b are opened so that the refrigerant flows through the hot gas bypass pipe 11.
The defrosting control means 30 adjusts the flow rate adjuster 12 and adjusts the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 based on the discharge superheat SH of the compressor 1 and the suction pressure Pin of the compressor 1 detected by the refrigerant state detection means 20 during the hot-gas defrosting control.
< refrigerant State detection means 20>
The refrigerant state detection means 20 detects the discharge superheat SH of the refrigerant discharged from the compressor 1 and the suction pressure Pin of the compressor 1, and includes a discharge temperature sensor 20a, a suction pressure sensor 20b, and a high-pressure temperature sensor 20 c. The discharge temperature sensor 20a detects the discharge refrigerant temperature of the refrigerant discharged from the compressor 1, and the suction pressure sensor 20b detects the suction pressure Pin of the refrigerant sucked into the compressor 1. The high-pressure temperature sensor 20c detects the temperature of the refrigerant discharged from the oil separator 2. The defrosting control means 30 functions as a part of the refrigerant state detection means, detects a difference between the discharge refrigerant temperature detected by the discharge temperature sensor 20a and the high-pressure side temperature detected by the high-pressure temperature sensor 20c, and determines the difference as the discharge superheat SH.
< operation in Hot gas defrost >
Here, the flow of the refrigerant during hot-gas defrosting will be described with reference to fig. 1. First, the refrigerant flowing out of the compressor 1 is separated into the refrigerant and oil in the oil separator 2, and the gas refrigerant flowing out of the oil separator 2 is branched into the refrigerant flowing to the condensers 4a and 4b via the check valve 3 and the refrigerant flowing to the heat gas bypass pipe 11. During the normal cooling operation, the flow rate regulator 12 is closed, and the refrigerant does not flow through the hot-gas bypass pipe 11. During hot gas defrost, the flow regulator 12 is open. According to the control, at least one of the first opening/closing valve 12a and the second opening/closing valve 12b is opened. The details of the control will be described later.
Thereafter, the refrigerant flowing through the flow rate regulator 12 passes through the evaporator 7, and at this time, frost adhering to the inside of the evaporator 7 is melted. The refrigerant melted in the evaporator 7 is partially condensed, and is separated into gas and liquid in the accumulator 8. The gas refrigerant flowing out of the accumulator 8 is sucked into the compressor 1. By opening the oil return regulator 10, the liquid refrigerant accumulated in the accumulator 8 is slowly returned to the compressor 1.
Since the amount of refrigerant flowing in the evaporator 7 is larger, the amount of heat for defrosting is larger, and thus the time for melting the frost attached to the evaporator 7 becomes shorter. However, if the refrigerant flowing through the evaporator 7 is excessive, a large amount of refrigerant condensed from the gas refrigerant into the liquid refrigerant in the evaporator 7 flows into the accumulator 8. If the allowable amount of the liquid refrigerant that can be stored in the accumulator 8 is exceeded, the liquid refrigerant flows into the compressor 1, and causes a failure of the compressor 1.
< control during Hot gas defrost >
Next, fig. 2 is a flowchart showing an example of the hot-gas defrosting control in the defrosting control unit 30 of fig. 1, and the hot-gas defrosting control of the refrigeration cycle apparatus 100 will be described with reference to fig. 1 and 2.
First, when it is determined that the defrosting operation is necessary or when the defrosting operation is periodically performed, the normal cooling operation is ended (step ST 1). Then, the refrigerant remaining in the refrigerant circuit is blocked by the evacuation operation (japanese: ポンプダウン) and refrigerant recovery is performed for a predetermined time (step ST2), and after the completion of refrigerant recovery, the evacuation operation is stopped (step ST 3). After that, the defrosting operation is started (step ST 10).
When the defrosting operation is started, the first opening/closing valve 12a of the flow rate adjuster 12 is opened under the control of the defrosting control unit 30 (step ST11), and the refrigerant of the first refrigerant flow rate flows through the hot-gas bypass pipe 11. Here, the discharge superheat SH and the suction pressure Pin of the compressor 1 are detected in the refrigerant state detecting means 20 (step ST 12). The discharge superheat SH is detected from a difference between the discharge refrigerant temperature detected by the discharge temperature sensor 20a and the high-pressure side temperature detected by the high-pressure temperature sensor 20 c. In addition, the suction pressure Pin is detected by the suction pressure sensor 20 b.
Then, the defrosting control means 30 determines whether or not the period in which the discharge superheat SH is larger than the set superheat SHref and the suction pressure Pin is smaller than the set pressure Pref continues for a predetermined period t1 (step ST 13). The set superheat degree SHref and the set pressure Pref are stored in the defrosting control unit 30 in advance. In embodiment 1, the predetermined period t1 is set to 10 seconds, for example. The defrosting control unit 30 performs control so as to continue the defrosting operation in a state where the first opening/closing valve 12a side of the flow rate adjuster 12 is opened and the second opening/closing valve 12b is closed until the condition of step ST13 is satisfied.
If the condition of step ST13 is satisfied, that is, if yes at step ST13 in fig. 2, the second opening/closing valve 12b is opened by the defrosting control unit 30 (step ST 14). Accordingly, the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 is increased as compared with the case where only the first opening/closing valve 12a is opened. Therefore, the defrosting time can be shortened.
In the state of step ST14, the discharge superheat SH and the suction pressure Pin of the compressor 1 are detected (step ST 15). Then, the defrosting control means 30 determines whether or not the period in which the discharge superheat SH is equal to or less than the set superheat SHref or the period in which the suction pressure Pin is equal to or more than the set pressure Pref continues for a predetermined period t2 (step ST 16). In embodiment 1, the predetermined period t2 is set to, for example, 3 seconds. The defrosting operation is performed in a state where both the first opening/closing valve 12a and the second opening/closing valve 12b of the flow rate regulator 12 are opened until the condition of step ST16 is satisfied. That is, the flow is repeated by the route in the case of no at step ST 16.
On the other hand, when the condition of step ST16 is satisfied, that is, when step ST16 is yes, it is determined that there is a possibility of liquid return to the compressor 1, and the second opening/closing valve 12b is closed by the defrosting control unit 30 (step ST 17). That is, since a large amount of the refrigerant used for defrosting may flow into the accumulator 8 and return the liquid refrigerant to the compressor 1 beyond the allowable amount of the accumulator 8 that enables gas-liquid separation, the amount of the refrigerant used for defrosting may be reduced by closing the second opening/closing valve 12 b. Thereafter, the defrosting operation is performed in a state where the first opening/closing valve 12a is opened and the second opening/closing valve 12b is closed (steps ST12 and ST 13).
The defrosting operation is controlled by the defrosting control unit 30 in accordance with the flow from ST11 to ST17 described above, and this flow is repeated until the defrosting operation stop condition is reached. The defrosting operation stop condition is that the temperature of a predetermined portion rises to a predetermined temperature or higher. In embodiment 1, for example, the defrosting operation is stopped when the outlet temperature of the evaporator 7 is 25 ℃. The defrosting operation stop condition can be set as appropriate according to the specification of the refrigeration cycle apparatus 100.
By adjusting the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 in accordance with the discharge superheat SH and the suction pressure Pin in this manner, the liquid return to the compressor 1 can be reliably prevented while the period of the defrosting operation is shortened. That is, the amount of refrigerant flowing through the evaporator 7 increases and the refrigerant temperature increases, and therefore the amount of heat increases, and the time required to melt the frost adhering to the inside of the evaporator 7 also decreases. However, when the refrigerant flowing into the evaporator 7 is excessive, a large amount of the liquid refrigerant condensed from gas into liquid in the evaporator 7 enters the accumulator 8 and exceeds the allowable amount enabling gas-liquid separation in the accumulator 8, and a large amount of the liquid refrigerant returns to the compressor 1, which causes a failure in the compressor 1. When the flow rate regulator 12 is opened and the refrigerant flows through the hot-gas bypass pipe 11, the refrigerant circulation amount flowing through the refrigerant circuit increases, and therefore the refrigerant flow rate flowing through the evaporator 7 also increases.
In the case of the conventional refrigeration cycle apparatus, the pressure on the suction side of the compressor 1 is detected, not the pressure on the discharge side of the compressor 1, as in the case of the suction pressure sensor 20b shown in fig. 1. The defrosting control unit 30 controls the opening and closing of the first opening/closing valve 12a and the second opening/closing valve 12b, and controls the amount of hot gas flowing into the evaporator 7. In this case, if the discharge pressure Pout of the compressor 1 does not rise even if the suction pressure Pin of the compressor 1 rises, the state in which both the first on-off valve 12a and the second on-off valve 12b are opened is not switched to the state in which only the first on-off valve 12a is opened, and therefore, the amount of liquid returned to the compressor 1 during defrosting increases.
Here, in the refrigeration cycle apparatus 100 according to embodiment 1, when the amount of liquid returned to the compressor 1 is large, the suction pressure Pin of the compressor 1 increases and the discharge superheat SH decreases. Therefore, when a predetermined period of time has elapsed while the suction pressure Pin is equal to or higher than the set pressure Pref and the discharge superheat SH is equal to or lower than the set superheat SHref, the second opening/closing valve 12b is closed. By closing the second opening/closing valve 12b, the flow rate of the refrigerant in the hot-gas bypass pipe 11 is reduced, and the amount of liquid returned to the compressor 1 is reduced. This can prevent a failure or the like caused by the liquid returning to the compressor 1. The predetermined period is set to, for example, 3 seconds.
In addition, when the amount of liquid returned to the compressor 1 during defrosting is small, the suction pressure Pin of the compressor 1 decreases and the discharge superheat SH increases. When a predetermined period of time has elapsed during which the suction pressure Pin is lower than the set pressure Pref and the discharge superheat SH is higher than the set superheat SHref, it is considered that the liquid return to the compressor 1 does not occur even if the refrigerant circulation amount is increased, and the second on-off valve 12b is opened. Then, since the refrigerant circulation amount in the refrigerant circuit increases, the amount of refrigerant flowing to the evaporator 7 increases, and defrosting can be performed in a short time.
The reason why the amount of liquid returned to the compressor can be reduced by setting the suction pressure Pin of the compressor 1 lower than the set pressure Pref is as follows. The following three heat sources are used for condensation of the hot-gas refrigerant in the hot-gas defrosting.
i) Sensible heat of cooler housing (including field piping)
ii) sensible heat of frost formation
iii) latent heat of frost formation
By setting the set pressure Pref and maintaining the suction pressure saturation temperature of the compressor 1 at 0 ℃ or lower, only the heat exchange amount of heat exchange with the substance less than 0 ℃ is used for condensation of the hot gas refrigerant. Therefore, the above-mentioned i) to iii) can be further subdivided,
i) -1 sensible heat of the cooler frame (-40 ℃ C. to 0 ℃ C.)
i) -2 sensible heat of the cooler frame (0 ℃ - +20 ℃)
ii) -1 sensible heat of frosting (-40 ℃ to 0 ℃)
ii) -2 sensible heat of frosting (0 ℃ to +20 ℃)
iii) latent heat of frost formation
The above-described temperature is an example of a case where defrosting is started when the temperature in the storage room is-40 ℃ and defrosting is completed when the temperature of the housing is +20 ℃. In the above description, the amounts of heat used for the condensation of the hot gas are only i) -1 and ii) -1, and the other amounts of heat are not used for the condensation of the hot gas, so that the amount of condensation of the hot gas can be reduced as compared with the conventional art.
Fig. 3 is a graph showing the relationship of the defrosting time to the temperature of the evaporator. When a predetermined period has elapsed while the discharge superheat SH is equal to or less than the set superheat SHref or while the suction pressure Pin is equal to or greater than the set pressure Pref, the defrosting control means 30 determines that there is a possibility of liquid return to the compressor 1. Then, the second opening/closing valve 12b is closed again to restrict the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11, thereby reducing the refrigerant circulation amount in the refrigerant circuit. Thus, the defrosting operation is performed in a state where the liquid return to the compressor 1 is reliably prevented from occurring. Then, as shown by the solid line in fig. 3, the discharge temperature of the refrigerant discharged from the compressor 1 (the temperature of the refrigerant flowing into the evaporator 7) can be set high as the defrosting time elapses, and the defrosting time can be shortened.
As described above, by switching the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 in accordance with the discharge superheat SH of the compressor 1 and the suction pressure Pin of the compressor 1, the reliability of the liquid return from the evaporator 7 to the compressor 1 can be increased, and the refrigerant circulation amount can be increased as compared with the conventional one. Even if the liquid return to the compressor 1 occurs due to the increase in the refrigerant circulation amount as the second on-off valve 12b is opened, the protective function of closing the second on-off valve 12b again functions, and the liquid return to the compressor 1 can be prevented.
In embodiment 2, the operation frequency control of the compressor 1 is further increased as compared with embodiment 1. Hereinafter, a description will be given centering on modifications to embodiment 1.
Fig. 4 is a flowchart showing an operation example of the refrigeration cycle apparatus of fig. 1. A refrigerant circuit diagram showing embodiment 2 of the refrigeration cycle apparatus of the present invention is the same as that of fig. 1.
In embodiment 2, the defrosting control unit 30 also has a function of increasing or decreasing the operating frequency f during the defrosting operation. The defrosting control unit 30 opens only the first opening/closing valve 12a when the defrosting operation is started, and operates the compressor 1 at a preset initial operation frequency f 0. Then, the defrosting control means 30 increases or decreases the operating frequency f based on the discharge superheat SH and the suction pressure Pin while keeping the refrigerant flow rate in the hot-gas bypass pipe 11 constant.
< control during Hot gas defrost >
Next, an operation example in embodiment 2 of the refrigeration cycle apparatus 100 will be described with reference to fig. 1 and 4. In fig. 4, the steps up to the start of hot-gas defrosting in fig. 2 (steps ST1 to ST3) are the same steps, and therefore, the description thereof is omitted. When the hot-gas defrosting control is started, the first opening/closing valve 12a of the flow rate regulator 12 is opened (step ST21) and the refrigerant is caused to flow through the hot-gas bypass pipe 11. At this time, the discharge superheat SH and the suction pressure Pin of the compressor 1 are detected in the refrigerant state detecting means 20 (step ST 22).
The defrosting control means 30 determines whether or not the period during which the discharge superheat SH is equal to or less than the set superheat SHref or the suction pressure Pin is equal to or less than the set pressure Pref continues for a predetermined period t3 in the defrosting control means 30 (step ST 23). The set superheat degree SHref and the set pressure Pref are stored in the defrosting control unit 30 in advance. If the condition at step ST23 continues for the predetermined period t3 (if yes at step ST23), the compressor operating frequency is decreased (step ST 24). In embodiment 2, the predetermined period t3 is set to, for example, 3 seconds. Then, the defrosting control means 30 controls the defrosting operation to be continued in a state where the first opening/closing valve 12a side of the flow rate adjuster 12 is opened and the second opening/closing valve 12b is closed until the condition of step ST23 is satisfied.
Then, the defrosting control means 30 determines whether or not the period in which the discharge superheat SH is greater than the set superheat SHref and the suction pressure Pin is greater than the set pressure Pref continues for a predetermined period t4 (step ST 25). In embodiment 2, the predetermined period t4 is set to 10 seconds, for example. In the case where the condition of step ST25 is not satisfied, i.e., when no in step ST25, repetition is again made from step ST 21. In the case where the condition of step ST25 is satisfied, that is, in the case of yes in ST25, the defrosting control unit 30 compares the operating frequency f of the compressor 1 with the maximum operating frequency fmax of the compressor 1 (step ST26), and in the case where the operating frequency f of the compressor 1 can be increased, that is, in the case of yes in ST26, controls so as to increase the amount of the prescribed frequency (step ST 27). Then, the flow is repeated again from step ST 21. When the operating frequency f of the compressor 1 is increased, the suction pressure Pin of the compressor 1 decreases, and the discharge superheat SH also decreases. When the operating frequency f of the compressor 1 is the maximum operating frequency fmax (no at step ST26), the second opening/closing valve 12b is opened without being increased (step ST 28).
In this state, the discharge superheat SH and the suction pressure Pin of the compressor 1 are detected (step ST 29). Then, it is determined whether or not the period in which the discharge superheat SH is greater than the set superheat SHref and the suction pressure Pin is greater than the set pressure Pref continues for a predetermined period t5 (step ST 30). In embodiment 2, t5 is set to 10 seconds, for example. If the above condition is satisfied, that is, if yes in ST30, the operating frequency f of the compressor 1 is increased by a predetermined amount (step ST 31). When the operating frequency f of the compressor 1 is increased, the suction pressure Pin of the compressor 1 decreases, and the discharge superheat SH also decreases. After increasing the operating frequency f of the compressor 1, the flow from ST28 is repeated. When the maximum operating frequency fmax has been reached, the operation is continued in the state of the maximum operating frequency fmax, and the flow from ST28 is repeated.
If the condition of step ST30 is not satisfied, that is, if no in ST30, the defrosting control unit 30 determines whether or not the period in which the discharge superheat SH is equal to or less than the set superheat SHref or the suction pressure Pin is equal to or less than the set pressure Pref continues for a predetermined period t6 (step ST 32). In embodiment 2, the predetermined period t6 is set to, for example, 3 seconds. If no in step ST32, it is determined that liquid return to the compressor 1 has not occurred, and the flow from ST28 is repeated again. If yes in step ST32, it is determined whether the operating frequency f of the compressor 1 is the minimum (step ST 33). When the operating frequency f of the compressor 1 has not reached the minimum operating frequency fmin, the compressor operating frequency is decreased (step ST 34). Then, the flow from ST28 is repeated until the operating frequency f of the compressor 1 reaches the minimum operating frequency fmin. On the other hand, when the operating frequency f reaches the minimum operating frequency fmin, the second opening/closing valve 12b is closed (step ST 35).
That is, the control of the refrigerant circulation amount is performed by increasing or decreasing the operating frequency f of the compressor 1 in a state where both the first on-off valve 12a and the second on-off valve 12b are open (steps ST29 to ST35), and when there is a possibility of liquid return to the compressor 1, the second on-off valve 12b is closed, and the hot-gas defrosting control is performed again in a state where only the first on-off valve 12a is open (steps ST21 to ST 35).
The defrosting operation is controlled by the defrosting control unit 30 in accordance with the flow from ST21 to ST35 described above, and this flow is repeated until the defrosting operation stop condition is reached. The defrosting operation stop condition is that the temperature of a predetermined portion rises to a predetermined temperature or higher. In embodiment 2, similarly to embodiment 1, the defrosting operation is stopped when the outlet temperature of the evaporator 7 is 25 ℃. The defrosting operation stop condition can be set as appropriate according to the specification of the refrigeration cycle apparatus 100.
In this way, by performing both the control of the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 by the flow rate regulator 12 and the control of the amount of refrigerant sucked into the compressor 1 during the defrosting operation, hot-gas defrosting can be performed with the maximum capacity within a range in which the liquid returning state to the compressor 1 does not occur, and therefore, the liquid returning to the compressor 1 can be reliably prevented while the defrosting time is further shortened.
Fig. 5 is a refrigerant circuit diagram showing embodiment 3 of a refrigeration cycle apparatus 300 according to the present invention. In embodiment 3, a flowchart illustrating an operation example of the refrigeration cycle apparatus 300 is the same as that in fig. 2. The refrigeration cycle apparatus 300 is described with reference to fig. 2 and 5. In the refrigeration cycle apparatus 300 of fig. 5, the same reference numerals are given to portions having the same configurations as those of the refrigeration cycle apparatus 100 of fig. 1, and the description thereof is omitted. In embodiment 3, the following is changed from embodiment 1: an oil return opening/closing valve 310a and an oil return opening/closing valve 310b are provided in parallel in the oil return pipe 309, and control the amount of oil returned from the accumulator 8 to the suction side of the compressor 1.
The oil return pipe 309 in fig. 5 is used to adjust the amount of the refrigerating machine oil returned from the accumulator 8 to the compressor 1, and includes a plurality of oil return opening/ closing valves 310a and 310 b. The oil return on-off valves 310a and 310b are configured by on-off valves having different capacities, and are independently controlled to open and close by the defrosting control unit 330. During the normal cooling operation, the oil return opening/closing valve 310a having a large capacity is used. On the other hand, during hot-gas defrosting, the defrosting control unit 330 closes the oil return opening/closing valve 310a having a large capacity and opens the oil return opening/closing valve 310b having a small capacity simultaneously with step ST11 in fig. 2.
In this way, the flow rate of the refrigerant in the hot-gas bypass pipe 11 can be controlled during the defrosting operation, and the amount of oil returning from the accumulator 8 to the compressor 1 can be reduced as compared with the normal cooling operation. Thus, the amount of circulation of hot gas can be increased by reducing the liquid return, and the defrosting time can be shortened.
Embodiment 4.
Fig. 6 is a refrigerant circuit diagram showing embodiment 4 of a refrigeration cycle apparatus 400 according to the present invention. The flowchart showing the operation example of the refrigeration cycle apparatus 400 of fig. 6 is the same as that of fig. 2. The refrigeration cycle apparatus 400 is described with reference to fig. 2 and 6. In the refrigeration cycle apparatus 400 of fig. 6, the same reference numerals are given to portions having the same configurations as those of the refrigeration cycle apparatus 100 of fig. 1, and the description thereof is omitted. The refrigeration cycle apparatus 400 of fig. 6 differs from the refrigeration cycle apparatus 100 of fig. 1 in that: during the defrosting operation, the flow of the refrigerant to the condenser 4b, which is a part of the plurality of condensers 4a and 4b, is stopped.
In the refrigeration cycle apparatus 400 of fig. 6, a system shut valve 401 is disposed on the inflow side of the condenser 4b, and the circulation or the shutoff can be selected by opening or closing the system shut valve 401. In fig. 6, the case where the system shut-off valve 401 is provided only on a part of the condenser 4b side is illustrated, but the system shut-off valve 401 may be provided in all the condensers 4a and 4b, and the closed system shut-off valve 401 may be selected by the defrosting control unit 430.
During the normal cooling operation, the system shut valve 401 is opened to perform the cooling operation by the plurality of condensers 4a and 4b, and during the hot gas defrosting control, the defrosting control unit 430 closes the system shut valve 401 to shut off the flow of the refrigerant to the condenser 4 b. That is, the system shut valve 401 is closed simultaneously with step ST11 of fig. 2. In this way, by causing the refrigerant to flow through the heat-air bypass pipe 11 during the defrosting operation and blocking the flow of the refrigerant to a part of the condenser 4b, the condensing temperature can be made higher than that during the normal cooling operation, and the defrosting time can be shortened.
Embodiment 5.
Referring to fig. 1 and 2, a refrigeration cycle apparatus 100 is described. In embodiment 5, the refrigeration cycle apparatus 100 is different from the refrigeration cycle apparatus 100 in embodiment 1 in that: during the defrosting operation, the air supply to the condensers 4a and 4b is stopped.
In embodiment 5, the defrosting control unit 30 stops the blowing of air to the condensers 4a and 4b by the condenser fans 5a and 5b when the hot-gas defrosting is started. That is, the condenser fans 5a, 5b are stopped simultaneously with step ST11 of fig. 2. In the normal cooling operation, the condenser fan is controlled so that the condensation temperature is lowered. In this way, by stopping the condenser fans 5a and 5b during the defrosting operation to increase the condensing temperature compared to the normal cooling operation, the defrosting time can be shortened.
Embodiment 6.
Fig. 7 is a refrigerant circuit diagram showing embodiment 6 of a refrigeration cycle apparatus 600 of the present invention. The flowchart showing the operation example of the refrigeration cycle device 600 of fig. 7 is the same as that of fig. 2. The refrigeration cycle apparatus 600 is described with reference to fig. 2 and 7. In the refrigeration cycle apparatus 600 of fig. 7, the same reference numerals are given to portions having the same configurations as those of the refrigeration cycle apparatus 100 of fig. 1, and the description thereof is omitted. The refrigeration cycle apparatus 600 of fig. 7 differs from the refrigeration cycle apparatus 100 of fig. 1 in that: during the defrosting operation, the flow of the refrigerating machine oil to the oil cooler 651 that cools the refrigerating machine oil stored in the oil separator 2 is stopped.
In the refrigeration cycle apparatus 600 according to embodiment 6, the refrigerator oil separated from the gas refrigerant is stored in the oil separator 2 during the normal cooling operation. The stored refrigerating machine oil is supplied to the oil cooler 651 through an oil cooling pipe 653a provided at the bottom of the oil separator 2. At this time, oil cooling bypass valve 650 is closed. The refrigerating machine oil supplied to the oil cooler 651 exchanges heat with air sent to the oil cooler 651 by the oil cooling fan 652 and is cooled. The structure is as follows: the cooled refrigerating machine oil passes through the oil cooling pipe 653b and returns to the compressor 1.
The embodiments of the present invention are not limited to the above embodiments. For example, although the refrigerant circuit that performs the cooling operation is exemplified in each of embodiments 1 to 6, the present invention can also be applied to a refrigeration cycle device that can select the cooling operation and the heating operation. In this case, the following may be used: instead of providing the hot-gas bypass pipe 11 only on the side of the one heat exchanger (evaporator 7), bypass pipes are provided in both the condensers 4a and 4b and the evaporator 7, and the hot-gas bypass pipe used for the defrosting control is selected according to the switching of the operation.
In addition, in embodiments 1 to 6, the case where one evaporator is provided in the refrigeration cycle apparatus is exemplified, but the present invention can also be applied to the case where a plurality of evaporators 7 connected in parallel are provided. Further, embodiments 2 to 6 can be used in combination as appropriate.
< effects of the invention >
The refrigeration cycle apparatus 100, 300, 400, 600 of the present invention includes a refrigerant circuit in which a compressor 1, condensers 4a, 4b, an expansion valve 6, and an evaporator 7 are connected in series by pipes, and the refrigeration cycle apparatus 100, 300, 400, 600 includes: a hot gas bypass pipe 11 directly connecting the discharge side of the compressor 1 to the evaporator 7; a flow rate adjuster 12 connected to the hot-gas bypass pipe 11, the flow rate adjuster 12 adjusting a flow rate of the refrigerant flowing through the hot-gas bypass pipe 11; a refrigerant state detection means 20 for detecting a discharge superheat SH of the refrigerant discharged from the compressor 1 and a suction pressure Pin of the compressor 1; and a defrost control unit 30, 330, 430, 630, the defrost control unit 30, 330, 430, 630 turning off the flow regulator 12 during a normal cooling operation, the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 is increased or decreased by the flow rate adjuster 12 based on the discharge superheat SH and the suction pressure Pin detected by the refrigerant state detecting means 20 during the defrosting operation, and the defrosting control means 30, 330, 430, 630, at the start of the defrosting operation, the flow rate regulator 12 is controlled so that the refrigerant of the first refrigerant flow rate flows through the hot-gas bypass pipe 11, during the defrosting operation, in the case where the discharge superheat SH is larger than the set superheat SHref and the suction pressure Pin is lower than the set pressure Pref, the flow rate regulator 12 is controlled so that the amount of refrigerant flowing through the hot-gas bypass pipe 11 is increased as compared to the first refrigerant flow rate.
With this configuration, the refrigeration cycle apparatus 100, 300, 400, or 600 of the present invention can increase the refrigerant flow rate by determining that the refrigerant flow rate in the hot-gas bypass pipe 11 is in a range in which liquid return to the compressor 1 does not occur during the defrosting control. That is, the refrigerant flow rate can be increased in a range where the liquid returning to the compressor 1 does not occur, and the defrosting time can be shortened.
In the refrigeration cycle apparatus 100, 300, 400, 600 of the present invention, the defrosting control means 30, 330, 430, 630 controls the flow rate adjuster so as to reduce the amount of refrigerant flowing through the hot-gas bypass pipe 11 to the first refrigerant flow rate when the discharge superheat SH is equal to or less than the set superheat SHref and the suction pressure Pin is equal to or more than the set pressure Pref during the defrosting operation.
With this configuration, the refrigeration cycle apparatus 100, 300, 400, or 600 according to the present invention can reduce the refrigerant flow rate before the refrigerant flow rate in the hot-gas bypass pipe 11 increases and liquid return to the compressor 1 occurs during defrosting control. That is, the defrosting time can be shortened, and the liquid return can be reliably prevented by reducing the refrigerant flow rate when the liquid return to the compressor 1 is about to occur.
Further, the refrigeration cycle apparatus 100, 300, 400, 600 of the present invention includes a refrigerant circuit in which a compressor 1, condensers 4a, 4b, an expansion valve 6, and an evaporator 7 are connected in series by pipes, and the refrigeration cycle apparatus 100, 300, 400, 600 includes: a hot gas bypass pipe 11 directly connecting the discharge side of the compressor 1 to the evaporator 7; a flow rate adjuster 12 connected to the hot-gas bypass pipe 11, the flow rate adjuster 12 adjusting a flow rate of the refrigerant flowing through the hot-gas bypass pipe 11; a refrigerant state detection means 20 for detecting a discharge superheat SH of the refrigerant discharged from the compressor 1 and a suction pressure Pin of the compressor 1; and a defrosting control means 30, 330, 430, 630, wherein the defrosting control means 30, 330, 430, 630 closes the flow rate adjuster 12 during the normal cooling operation, increases or decreases the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 by the flow rate adjuster 12 based on the discharge superheat SH and the suction pressure Pin detected by the refrigerant state detection means 20 during the defrosting operation, and the defrosting control means 30, 330, 430, 630 controls the flow rate adjuster 12 to flow the refrigerant at the first refrigerant flow rate through the hot-gas bypass pipe 11 at the start of the defrosting operation, and controls the flow rate adjuster 12 to decrease the operating frequency f of the compressor 1 when the discharge superheat SH is equal to or less than the set superheat SHref or the suction pressure Pin is equal to or less than the set pressure Pref during the defrosting operation.
With this configuration, the refrigeration cycle apparatus 100, 300, 400, 600 according to the present invention can increase the discharge superheat SH by reducing the operating frequency of the compressor 1 during the defrosting control, thereby shortening the defrosting time.
In the refrigeration cycle apparatus 100, 300, 400, 600 of the present invention, the defrosting control means 30, 330, 430, 630 increases the operating frequency f of the compressor 1 when the discharge superheat SH is greater than the set superheat SHref and the suction pressure Pin is greater than the set pressure Pref during the defrosting operation. When the operating frequency f of the compressor 1 is the maximum operating frequency fmax, the flow rate adjuster 12 is controlled so as to increase the amount of the refrigerant flowing through the hot-gas bypass pipe 11 in comparison with the first refrigerant flow rate.
With this configuration, the refrigeration cycle apparatus 100, 300, 400, 600 of the present invention can increase the refrigerant flow rate when the operating frequency of the compressor 1 is maximized and it is determined that the liquid return to the compressor 1 does not occur. That is, the refrigerant flow rate can be increased in a range where the liquid returning to the compressor 1 does not occur, and the defrosting time can be shortened.
In the refrigeration cycle apparatus 100, 300, 400, 600 of the present invention, the defrosting control means 30, 330, 430, 630 increases the amount of refrigerant flowing through the hot-gas bypass pipe during the defrosting operation as compared to the first refrigerant flow rate, and then decreases the operating frequency f of the compressor 1 when the discharge superheat SH is equal to or less than the set superheat or the suction pressure Pin is equal to or less than the set pressure Pref, and controls the flow rate adjuster 12 to decrease the amount of refrigerant flowing through the hot-gas bypass pipe 11 to the first refrigerant flow rate when the operating frequency f of the compressor 1 is the minimum operating frequency fmin.
With this configuration, in the refrigeration cycle apparatus 100, 300, 400, or 600 according to the present invention, when both the first opening/closing valve 12a and the second opening/closing valve 12b are opened and the flow rate of the hot-gas bypass pipe 11 is increased, and when it is determined that the flow rate is in the range in which liquid return to the compressor 1 does not occur, the operating frequency f of the compressor 1 is further increased, and thus the defrosting time can be further shortened. The defrosting time can be shortened by increasing the refrigerant flow rate in the hot-gas bypass pipe 11 during the defrosting control, thereby further increasing the operating frequency f of the compressor 1 and increasing the amount of heat to be sent to the evaporator 7, but the refrigerant flow rate can be reduced before the liquid return to the compressor 1 occurs. That is, the defrosting time can be shortened, and the liquid return can be reliably prevented by reducing the refrigerant flow rate when the liquid return to the compressor 1 is about to occur.
In the refrigeration cycle apparatuses 100, 300, 400, and 600 according to the present invention, the flow rate regulator 12 is configured by a plurality of on-off valves connected in parallel with one another, and the defrosting control means 30, 330, 430, and 630 controls the flow rate of the refrigerant flowing through the hot-gas bypass pipe 11 in accordance with the number of open on-off valves.
The flow rate regulator 12 further includes: a first on-off valve 12a that opens the first on-off valve 12a to allow the refrigerant at a first refrigerant flow rate to flow through the hot-gas bypass pipe 11; and a second on-off valve 12b connected in parallel with the first on-off valve 12a, wherein the defrosting control means 30, 330, 430, and 630 opens the first on-off valve 12a and closes the second on-off valve 12b to allow the refrigerant at the first refrigerant flow rate to flow through the hot-gas bypass pipe 11, and opens the first on-off valve 12a and the second on-off valve 12b to increase the amount of the refrigerant flowing through the hot-gas bypass pipe 11 as compared to the first refrigerant flow rate.
With this configuration, the refrigeration cycle apparatus 100, 300, 400, or 600 of the present invention can be configured with a refrigerant circuit having a simple configuration, and control can be performed by opening and closing only two opening/closing valves. This can suppress the cost of the refrigeration cycle devices 100, 300, 400, and 600.
The refrigeration cycle apparatus 400 of the present invention further includes a system shut-off valve 401 that shuts off the refrigerant flowing through the condensers 4a and 4b, wherein a plurality of condensers 4a and 4b are provided in parallel in the refrigerant circuit, and the defrosting control units 430 and 630 close the system shut-off valve 401 during the defrosting operation.
The refrigeration cycle apparatuses 100, 300, 400, and 600 of the present invention further include condenser fans 5a and 5b that send air to the condensers 4a and 4b, and the defrosting control means 30, 330, 430, and 630 stops the condenser fans 5a and 5b when the defrosting operation is started.
With this configuration, the refrigeration cycle apparatus 100, 300, 400, and 600 according to the present invention can increase the amount of heat used for defrosting by operating the condenser with a reduced capacity during defrosting operation, and therefore can shorten the defrosting time as compared with a case where defrosting operation is performed without changing the capacity of the condenser.
Further, the refrigeration cycle device 300 of the present invention further includes: an accumulator 8, the accumulator 8 being provided on a suction side of the compressor 1; an oil return pipe 309, the oil return pipe 309 returning the refrigerating machine oil stored in the accumulator 8 to the compressor 1; and oil return regulators 310a and 310b, the oil return regulators 310a and 310b being provided in the oil return pipe 309 and controlling the flow rate of the refrigerating machine oil in the oil return pipe 309, and the defrosting control unit 330 controls the oil return regulators 310a and 310b so that the amount of the refrigerating machine oil returned to the compressor 1 is smaller than that in the normal cooling operation during the defrosting control.
With this configuration, the refrigeration cycle apparatus 300 of the present invention can suppress the amount of cooled refrigerating machine oil and liquid refrigerant having a small quantity of heat from returning to the compressor 1, and therefore the amount of hot gas supplied to the evaporator 7 increases accordingly, and thus the defrosting time can be shortened.
Further, the refrigeration cycle apparatus 600 of the present invention further includes: an oil separator 2, the oil separator 2 being provided on a discharge side of the compressor 1; an oil cooler 651 that is connected to oil cooling pipes 653a and 653b for returning the refrigerating machine oil from the oil separator 2 to the compressor 1, and cools the refrigerating machine oil; and an oil cooling bypass valve 650, the oil cooling bypass valve 650 being provided in a pipe connecting an oil cooling pipe 653a between the oil separator 2 and the oil cooler 651 and an oil cooling pipe 653b between the oil cooler 651 and the compressor 1, the defrosting control unit 630 opening the oil cooling bypass valve 650 at the start of the defrosting operation.
With this configuration, the refrigeration cycle apparatus 600 of the present invention can suppress the amount of cooled refrigerating machine oil and liquid refrigerant having a small quantity of heat from returning to the compressor 1, and therefore the amount of hot gas supplied to the evaporator 7 increases accordingly, and thus the defrosting time can be shortened.
In the refrigeration cycle apparatus 100, 300, 400, or 600 of the present invention, the flow rate regulator 12 includes a flow rate regulating valve connected in series to the first on-off valve 12a or the second on-off valve 12 b. In embodiments 1 to 6 of the present invention, the flow rate adjustment valve corresponds to the needle valve 13.
With this configuration, in the refrigeration cycle apparatuses 100, 300, 400, and 600 according to the present invention, even when there is a difference in the length of the pipe 11 or the like due to the installation position, the opening degree (refrigerant flow rate) can be adjusted to an optimum degree according to the field situation, and the defrosting time can be shortened.
In the refrigeration cycle apparatuses 100, 300, 400, and 600 according to the present invention, the flow rate adjuster 12 is constituted by an electrically operated valve capable of continuously adjusting the opening degree.
With this configuration, in the refrigeration cycle apparatuses 100, 300, 400, and 600 according to the present invention, the hot-gas defrosting operation can be performed by a single on-off valve without using a plurality of valves, and the refrigerant flow rate in the hot-gas bypass pipe 11 can be continuously changed, so that a more precise flow rate control can be performed.
Description of reference numerals
1 compressor, 2 oil separator, 3 check valve, 4a condenser, 4b condenser, 5a condenser fan, 5b condenser fan, 6 expansion valve, 7 evaporator, 7a blower fan, 8 reservoir, 9 oil return piping, 10 oil return regulator, 11 hot gas bypass piping, 12 flow regulator, 12a first on-off valve, 12b second on-off valve, 13 needle valve, 20 refrigerant state detection unit, 20a discharge temperature sensor, 20b suction pressure sensor, 20c high pressure temperature sensor, 30 defrost control unit, 100 refrigeration cycle apparatus, 300 refrigeration cycle apparatus, 309 oil return piping, 310a oil return on-off valve, 310b oil return on-off valve, 330 defrost control unit, 400 refrigeration cycle apparatus, 401 system shut-off valve, 430 defrost control unit, 600 refrigeration cycle apparatus, 630 defrost control unit, 650 oil cooling bypass valve, 651 device, 652 oil cooling fan, 653a oil cooling pipe, 653b oil cooling pipe, Pin suction pressure, Pout discharge pressure, Pref set pressure, SH discharge superheat, SHref set superheat, f operating frequency, f0 initial operating frequency, fmax maximum operating frequency, fmin minimum operating frequency, t1 predetermined period, t2 predetermined period, t3 predetermined period, t4 predetermined period, t5 predetermined period, t6 predetermined period.
Claims (13)
1. A refrigeration cycle device provided with a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in series by pipes, the refrigeration cycle device comprising:
a hot gas bypass pipe directly connecting the discharge side of the compressor to the evaporator;
a flow rate regulator connected to the hot-gas bypass pipe and configured to regulate a flow rate of the refrigerant flowing through the hot-gas bypass pipe;
a refrigerant state detection unit that detects a discharge superheat of the refrigerant discharged from the compressor and a suction pressure of the compressor; and
a defrosting control means for closing the flow rate adjuster during a normal cooling operation and increasing or decreasing the flow rate of the refrigerant flowing through the hot gas bypass pipe by the flow rate adjuster during a defrosting operation based on the discharge superheat and the suction pressure detected by the refrigerant state detection means,
the defrosting control means controls the flow rate adjuster to cause the refrigerant of a first refrigerant flow rate to flow through the hot gas bypass pipe when a defrosting operation is started,
the defrosting control means controls the flow rate adjuster to increase the amount of refrigerant flowing through the hot gas bypass pipe in comparison with the first refrigerant flow rate when the discharge superheat is larger than a set superheat and the suction pressure is lower than a set pressure during a defrosting operation.
2. The refrigeration cycle apparatus according to claim 1,
the defrosting control means controls the flow rate adjuster to reduce the amount of refrigerant flowing through the hot gas bypass pipe to the first refrigerant flow rate when the discharge superheat is equal to or less than the set superheat or the suction pressure is equal to or more than the set pressure during a defrosting operation.
3. A refrigeration cycle device provided with a refrigerant circuit in which a compressor, a condenser, an expansion valve, and an evaporator are connected in series by pipes, the refrigeration cycle device comprising:
a hot gas bypass pipe directly connecting the discharge side of the compressor to the evaporator;
a flow rate regulator that is provided in the hot-gas bypass pipe and that regulates a flow rate of the refrigerant flowing through the hot-gas bypass pipe;
a refrigerant state detection unit that detects a discharge superheat and a suction pressure of the refrigerant discharged from the compressor; and
a defrosting control means for closing the flow rate adjuster during a normal cooling operation and increasing or decreasing the flow rate of the refrigerant flowing through the hot gas bypass pipe by the flow rate adjuster during a defrosting operation based on the discharge superheat and the suction pressure detected by the refrigerant state detection means,
the defrosting control means controls the flow rate adjuster to cause the refrigerant of a first refrigerant flow rate to flow through the hot gas bypass pipe when a defrosting operation is started,
the defrosting control means reduces the operating frequency of the compressor when the discharge superheat is equal to or less than a set superheat or the suction pressure is equal to or less than a set pressure during the defrosting operation.
4. The refrigeration cycle apparatus according to claim 3, wherein,
the defrosting control unit increases an operating frequency of the compressor in a case where the discharge superheat is larger than a set superheat and the suction pressure is larger than a set pressure during the defrosting operation,
the defrosting control means controls the flow rate adjuster to increase the amount of the refrigerant flowing through the hot-gas bypass pipe in comparison with the first refrigerant flow rate when the operating frequency of the compressor reaches a maximum operating frequency.
5. The refrigeration cycle apparatus according to claim 4, wherein,
the defrosting control means increases the amount of refrigerant flowing through the hot-gas bypass pipe during the defrosting operation as compared to the first refrigerant flow rate, and then decreases the rotational frequency of the compressor when the discharge superheat is equal to or less than a set superheat or the suction pressure is equal to or less than a set pressure, and controls the flow rate adjuster to decrease the amount of refrigerant flowing through the hot-gas bypass pipe to the first refrigerant flow rate when the compressor operating frequency is a minimum operating frequency.
6. The refrigeration cycle device according to any one of claims 1 to 5, wherein,
the flow regulator is constituted by a plurality of opening and closing valves connected in parallel to each other,
the defrosting control unit controls a flow rate of the refrigerant flowing through the hot gas bypass pipe according to the number of the open/close valves that are opened.
7. The refrigeration cycle device according to any one of claims 1 to 5, wherein,
the flow rate adjuster is provided with:
a first on-off valve that opens to allow the refrigerant at the first refrigerant flow rate to flow through the hot-gas bypass pipe; and
a second on-off valve connected in parallel with the first on-off valve,
the defrosting control means opens the first on-off valve and closes the second on-off valve to cause the refrigerant of the first refrigerant flow rate to flow through the hot gas bypass pipe,
the amount of refrigerant flowing through the hot-gas bypass pipe is increased as compared to the first refrigerant flow rate by opening the first opening/closing valve and the second opening/closing valve.
8. The refrigeration cycle device according to any one of claims 1 to 5, wherein,
the refrigeration cycle device further includes a system shut-off valve that shuts off the refrigerant flowing to the condenser,
the condenser is provided in plurality in parallel in the refrigerant circuit,
the defrosting control unit closes the system shut-off valve during the defrosting operation.
9. The refrigeration cycle device according to any one of claims 1 to 5, wherein,
the refrigeration cycle device further includes a condenser fan for blowing air to the condenser,
the defrosting control unit stops the condenser fan when the defrosting operation is started.
10. The refrigeration cycle apparatus according to any one of claims 1 to 5, further comprising:
an accumulator disposed at a suction side of the compressor;
an oil return pipe that returns the refrigerating machine oil stored in the accumulator to the compressor; and
an oil return regulator provided on the oil return piping and controlling a flow rate of the refrigerating machine oil in the oil return piping,
the defrosting control means controls the oil return regulator so that the amount of the refrigerant oil returned to the compressor is smaller than that in the normal cooling operation during defrosting control.
11. The refrigeration cycle apparatus according to any one of claims 1 to 5, further comprising:
an oil separator provided on a discharge side of the compressor;
an oil cooler connected to an oil cooling pipe for returning the refrigerating machine oil from the oil separator to the compressor, and cooling the refrigerating machine oil; and
an oil cooling bypass valve provided in a pipe connecting the oil cooling pipe from the oil separator to the oil cooler and the oil cooling pipe from the oil cooler to the compressor,
the defrosting control unit opens the oil-cooling bypass valve at the start of defrosting operation.
12. The refrigeration cycle apparatus according to claim 7, wherein,
the flow rate regulator includes a flow rate regulating valve connected in series with the first opening/closing valve or the second opening/closing valve.
13. The refrigeration cycle device according to any one of claims 1 to 5, wherein,
the flow rate adjuster is constituted by an electrically operated valve capable of continuously adjusting the opening degree.
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| Application Number | Priority Date | Filing Date | Title |
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| PCT/JP2015/084855 WO2017098669A1 (en) | 2015-12-11 | 2015-12-11 | Refrigeration cycle device |
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| CN108369046B true CN108369046B (en) | 2020-07-28 |
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| CN110709649B (en) * | 2017-06-12 | 2021-08-10 | 三菱电机株式会社 | Refrigeration cycle device |
| CN109114749B (en) * | 2018-07-04 | 2021-05-28 | 青岛海尔空调器有限总公司 | Control method and device for air conditioning system |
| WO2020161834A1 (en) * | 2019-02-06 | 2020-08-13 | 三菱電機株式会社 | Refrigeration cycle device |
| SE545954C2 (en) | 2019-03-25 | 2024-03-26 | Mitsubishi Electric Corp | An air-conditioning apparatus comprising a plurality of parallel heat exchangers and configured to adjust the refrigerant flow rate to defrost one of said heat exchangers |
| JP6594599B1 (en) | 2019-04-11 | 2019-10-23 | 三菱電機株式会社 | Air conditioner |
| CN114729765B (en) * | 2019-11-15 | 2024-05-17 | 三菱电机株式会社 | Cold and heat source unit and refrigeration cycle device |
| CN111536722A (en) * | 2020-05-26 | 2020-08-14 | 广东省现代农业装备研究所 | Defrosting method and device for supercooling refrigerant of main path of refrigeration cycle |
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Also Published As
| Publication number | Publication date |
|---|---|
| CN108369046A (en) | 2018-08-03 |
| JP6403907B2 (en) | 2018-10-10 |
| JPWO2017098669A1 (en) | 2018-04-12 |
| WO2017098669A1 (en) | 2017-06-15 |
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