JPH0543945B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a refrigeration system, in particular, a refrigeration system that is equipped with a hot gas bypass path and that guides hot gas to an evaporator to lower the internal temperature of, for example, a container or a refrigerator to -5, for example.
From the freezing range below ℃~-6℃, -5℃~-6℃
The present invention relates to a refrigeration system that can be controlled to a higher temperature chilled region.

Conventionally, a hot gas bypass path has been provided in which hot gas discharged from a compressor bypasses a condenser and is bypassed to an evaporator, and the capacity is adjusted by controlling the amount of hot gas bypassed to the evaporator. A device in which the internal temperature is controlled in a chilled region has already been proposed, for example, as shown in US Pat. No. 3,692,100 and the drawings.

The outline of _this conventional device will be explained based on the schematic diagram of _FIG .
The condensers C ₁ and C ₂ are connected to a hot gas bypass path H that bypasses the liquid receiver R and the expansion valve EV, and this hot gas bypass path H is connected to the inlet side of the evaporator E. A hot gas valve HV is installed to control the amount of hot gas bypass.
By controlling the HV, the capacity of the evaporator E is adjusted, and the temperature of the discharged air and, by extension, the temperature inside the refrigerator are controlled to a chilled region.

By the way, in this conventional device, when the evaporator E is frosted, the defrost operation can be performed by circulating the entire amount of circulating refrigerant to the evaporator E using the hot gas valve HV, but as described above, In refrigeration operation in which hot gas is bypassed and the temperature of the blown air is controlled in the chilled region, the low pressure of the refrigerant increases in accordance with the blown air temperature, which increases the amount of refrigerant circulation. In refrigeration operation where the temperature of the blown air is controlled in the refrigeration range, the low pressure of the refrigerant is low and the amount of refrigerant circulated is also reduced, so when a defrost command is issued and the above-mentioned defrost operation using hot gas is performed, the refrigerant is circulated through the defrost circuit. The amount of refrigerant changes depending on the operating state immediately before starting the defrost operation, resulting in the following problems.

In other words, in a refrigeration operation where the blowing air temperature is controlled to a high temperature, when defrosting operation is performed in a state where the low pressure of the refrigerant is high and the amount of refrigerant circulation is increasing, the amount of refrigerant flowing into the defrost circuit also increases. Therefore, defrosting can be completed in a short time, but
On the other hand, since the air temperature around evaporator E increases when defrosting ends, when refrigerating operation is resumed, the refrigerant will be in an abnormally high pressure state and overcurrent will flow through the motor of compressor A, causing the operating range to decrease. If the temperature is exceeded, the high pressure switch or overcurrent relay will be activated, causing a problem that the operation will not be possible.Furthermore, in refrigeration operation where the temperature of the blown air is controlled at a constant temperature, the low pressure of the refrigerant will be low and the amount of refrigerant circulating will be low. When performing defrost operation, the amount of refrigerant flowing through the defrost circuit also decreases, resulting in a problem that the amount of defrost heat is small and the defrost time becomes longer.

In this way, when performing defrost operation by circulating hot gas to the evaporator E, the amount of hot gas circulating to the evaporator E changes depending on the operating condition immediately before starting the defrosting operation, so the operating condition and the outside temperature at that time vary. In some cases, proper defrost operation could not be performed.

An object of the present invention is to adjust the amount of refrigerant circulated through the defrost circuit during defrost operation to the optimum amount that allows proper defrost operation using a fixed amount outflow valve controlled by a timer, and to adjust the amount of refrigerant to be circulated through the defrost circuit to the optimum amount that enables proper defrost operation. The aim is to always perform optimal defrosting regardless of the condition.

The configuration of the present invention includes a hot gas bypass path that bypasses the condenser and bypasses the hot gas discharged from the compressor to the evaporator, and during frosting, the entire amount of circulating refrigerant is circulated to the evaporator. In a refrigeration system equipped with a hot gas valve that performs defrost operation, an on-off valve that closes upon a defrost operation start command is provided downstream of the condenser, and refrigerant is supplied to the liquid reservoir including the condenser by pump-down operation. At the same time, a communication passage is provided which bypasses the on-off valve and communicates the liquid reservoir with the suction side of the compressor, and this communication passage is opened for a certain period of time after the end of the pump-down operation, and the liquid reservoir is connected to the suction side of the compressor. When a fixed amount outflow valve is provided to allow a certain amount of the trapped refrigerant to flow out to the suction side of the compressor, and a defrost operation is performed in response to a defrost command, the fixed amount outflow valve is always operated regardless of the previous operating state. Through control, a preset constant amount of refrigerant is circulated through the defrost circuit, allowing optimal defrost to be performed.

Next, an embodiment of the present invention will be described based on FIG.

What is shown in Fig. 1 is a container refrigeration system, in which 1 is a compressor, 2 is an air-cooled condenser, 3 is a water-cooled condenser, 4 is an evaporator, and 5 is a temperature sensing part S.
1, each of these devices is a temperature-sensitive expansion valve with
They are connected by refrigerant pipes 6, forming a refrigeration cycle in which the evaporator 4 cools the air inside the refrigerator.

In FIG. 1, 7 is an accumulator-shaped liquid receiver, 7a is a liquid receiving part, 7b is an accumulator part, 8 is a dryer, 9 is a liquid indicator, 10 is a fan attached to the evaporator 4,
11 is a fan attached to the air-cooled condenser 2.

In the refrigeration cycle configured as described above, the high pressure gas pipe 6a connecting the discharge side of the compressor 1 and the inlet side of the air-cooled condenser 2 is connected to the compressor 1.
The hot gas discharged from each condenser 2,
3. Connect a hot gas bypass path 20 that bypasses the liquid receiving part 7a of the liquid receiver 7 and the temperature-sensitive expansion valve 5 to the evaporator 4, and connects this outlet side to the expansion valve 5 and the evaporator 4. connected to the low pressure liquid pipe 6b between the
A hot gas valve 21 is interposed at the connection portion of the hot gas bypass path 20 to the high pressure gas pipe 6a, and a refrigerating valve is installed downstream of the condenser 3, that is, downstream of the liquid indicator 9 in FIG. A liquid reservoir including the condensers 2 and 3 and the liquid receiving part 7a of the liquid receiver 7 is provided with an electromagnetic on-off valve 30 that closes upon a command to stop the operation or refrigeration operation and a command to start the defrost operation to enable pump-down operation. The opening/closing valve 3 is configured to confine the refrigerant in the
0 is bypassed, and a communication passage 40 is provided which communicates the liquid reservoir with the suction side of the compressor 1, and this communication passage 40
A pressure reducing device mainly consists of a quantitative outflow valve 41 that opens for a certain period of time after the end of the pump-down operation and allows a certain amount of refrigerant out of the refrigerant trapped in the liquid reservoir to flow out to the suction side of the compressor 1, and a capillary reach tube. A mechanism 42 is provided, and during defrost operation, the defrost circuit, that is, the compressor 1, the hot gas valve 21,
Hot gas bypass path 20, evaporator 4, liquid receiver 7
A fixed amount of refrigerant is circulated through the hot gas circuit consisting of the accumulator section 7b.

The hot gas valve 21 is mainly an electric three-way valve that can control the valve opening degree to the hot gas bypass passage 20 from 0% to 100% in proportion to the voltage, and controls the hot gas bypass passage to the evaporator 4. At the same time, the entire amount of refrigerant circulated during frosting is transferred to the hot gas bypass path 20.
This is done by using a proportional control valve designed to allow the air to flow through the air, and controlled by a controller 22 and an auxiliary relay 2DX of the defrost control circuit, which will be described later. Note that this hot gas valve 21 is PID controlled by a controller 22. This PID control (Proportional−plus−integral−plus−
The term "derivative con-trol" refers to control in which the control signal is proportional to the sum of the error signal, its integral, and its derivative.

Further, the on-off valve 30 is mainly connected to the high pressure liquid pipe 6c.
In addition to the condensers 2 and 3 and the liquid receiving part 7a of the liquid receiver 7, the high-pressure liquid pipe 6c is used as a liquid reservoir to store liquid refrigerant. One end of the communication passage 40 is connected to the liquid reservoir on the upstream side with respect to the interposed position where the on-off valve 30 is interposed, and the other end is connected to the Since it is necessary to bypass the on-off valve 30, it is connected downstream of the intervening position of the on-off valve 30, and preferably the evaporator 4 is connected to the bypassed low-pressure gas pipe 6d.

The opening/closing valve 30 may be installed in any route from the outlet of the condenser 3 to the inlet of the evaporator 4, and may be installed in the low-pressure liquid pipe 6b, for example.

In addition, the fixed amount outflow valve 41 closes the opening/closing valve 30 in response to a defrost operation start command, and a pump down operation is performed, and this pump down operation is ended by turning off the low pressure switch 63L as described later. Control is performed so that the closing operation is performed after a certain amount of the refrigerant trapped in the liquid reservoir has flowed out during the pump-down operation, and this closing operation control is performed by a timer 2D ₂ that starts after the pump-down operation is completed. is used.

This timer 2D ₂ is installed in a defrost control circuit in an electric circuit which will be explained later, and this timer 2D ₂ is connected to the low voltage switch 63.
The compressor 1 is stopped by the off operation of L to complete the pump down operation, and at the same time, the quantitative outflow valve 41 is opened,
When the refrigerant in the liquid reservoir is to be discharged, a count is started, and after a predetermined time elapses, an off operation is performed to close the fixed quantity discharge valve 41, and defrost is discharged from the communication passage 40 according to the time set by the timer _2D2 . The amount of refrigerant flowing into the circuit can be controlled to a constant amount.

As described above, the fixed amount outflow valve 41 is controlled by the timer _2D2 to allow a certain amount of refrigerant to flow out, and defrost operation is performed with the set amount of refrigerant.
This amount of refrigerant is such that regardless of the operating state immediately before the defrost operation, the steady operation performed after the defrost operation is always kept within the operable range, and
It is set to the optimum amount so that the defrost time does not become too long.

In FIG. 1, reference numeral 23 denotes an energized/closed electromagnetic valve that connects to the suction gas pipe 6e, and is connected in parallel with the capillary reach tube 24 and interposed in the suction gas pipe 6e.

This solenoid valve 23 supplies the suction gas refrigerant to the capillary reach tube 2 by closing the solenoid valve 23.
The refrigerant is returned to the compressor 1 through the refrigerant 4, and the amount of refrigerant circulated is reduced.The amount of refrigerant is reduced in this way when the outside temperature is high, when the pump starts steady operation after defrosting, or when the pump This is to prevent the high and low pressures of the refrigerant from increasing and overloading during downtime, and the reduction in the amount of circulation reduces the amount of work of the compressor 1, reducing the high pressure and the current value of the compressor motor. This allows the operating range to be expanded.

The electromagnetic valve 23 detects the suction temperature of the evaporator 4, closes to reduce the circulation amount when the suction temperature exceeds a certain value, and opens when the suction temperature exceeds a certain value. In addition, opening/closing control may be performed by detecting high pressure or low pressure, or by detecting the suction temperature of the air-cooled condenser 2, that is, the outside air temperature,
It may be configured so that it closes when the outside temperature is above a certain value and opens when it is lower than a certain value.

Further, in FIG. 1, reference numeral 25 bypasses a certain amount of hot gas regardless of the opening degree of the hot gas valve 21 during refrigeration operation, and prevents changes in control accuracy due to variations in the valve opening degree with respect to load fluctuations of the hot gas valve 21. This is an auxiliary bypass path to reduce the amount of water used, and a solenoid valve 26 is interposed in the middle of the path to close during freezing operation and open during refrigeration operation.

Also, in Fig. 1, 63H is a high pressure switch, 6
3L is a low pressure switch, 63CL is a high pressure control switch, 63QL is a hydraulic protection switch, and 63W is a water pressure switch.

Further, in the above configuration, the command to start the defrost operation mainly uses the air pressure switch APS and the defrost timer _2D1 whose set time is, for example, 12 hours. In this case, the air pressure switch APS is
This is done by giving priority to the defrost timer _2D1 and resetting the defrost timer _2D1 by operating the air pressure switch APS.

Furthermore, when the defrost operation is finished, for example, the low pressure gas pipe 6d on the outlet side of the evaporator 4 is
Two thermostats 23D ₁ with different set temperatures,
_23D2 is attached to detect the temperature of the low pressure gas pipe 6d.

Next, the electric circuits of the controller 22 for controlling the temperature of the blown air by controlling the hot gas valve 21 and the respective control devices for controlling the defrost operation will be explained based on FIG.

What is shown in FIG. ₂ is an electric circuit of the refrigeration system shown in FIG. MC, three indoor fan motors MF _1-1 , MF 1-2 , MF 1-3 corresponding to the three fans 10 attached to the evaporator 4, and three indoor fan motors MF 1-1 , MF _1-2 , MF _1-3 attached to the air-cooled condenser 2. Juan 11...
Three outdoor fan motors MF _2-1 compatible with
Equipped with MF _2-2 and MF _2-3 electrical equipment, the electrical circuits of these electrical equipment can be connected to one of the 200V or 220V low-voltage power plug P ₁ and the 380-415V or 440V high-voltage power plug P _2. is selected and connected to a power supply, and the controller 22 and the control circuits of the respective control devices are connected to the power supply circuit via a transformer Tr.

In FIG. 2, CB is a circuit breaker, OC is an overcurrent relay, 2X ₁ to 2X ₃ are auxiliary relays and their contacts, and 3-88 is an on/off switch. In the power supply circuit, unmarked contacts are switching contacts that can be switched by selecting the plugs P ₁ and P 2 , and Y ₂ , U ₁ , _{G 2 ,} and G ₁ are for refrigeration operation and refrigeration built in the controller 22. The operating switch, _Y1 , is also a short-circuit wire.

Although not shown, the controller 22 includes an input transformer, a power input device, a sensor input device, an operation input/output device, a central processing unit, and a relay output device. As shown, a return sensor RS is placed on the suction side of the evaporator 4 and detects the temperature of the return air from inside the refrigerator, that is, the suction air, and a supply sensor SS is connected to the outlet side of the evaporator 4 to detect the temperature of the blowing air. ,
Further, a set point selector PS and an output display DP are connected to the operation input/output device, and the hot gas valve 21 is connected to the relay output device.
motor 20M and each solenoid relay 2 of the solenoid valves 23 and 26 in the embodiment shown in FIG.
In addition to 0SS and 20BS, auxiliary relays 2X ₄ and 2X ₅ , and lamps AL and BL, the following relay circuits are connected.

(1) A series circuit (pump-down control circuit) with the solenoid relay _20LS1 of the on-off valve 30 for pump-down operation of the normally open contact of the auxiliary relay _2X4 .

(2) Air pressure switch APS that issues a command to start hot gas operation, defrost timer 2D ₁
A parallel circuit of each contact of manual defrost switch 3D and a normally open contact of defrost relay 2DX ₁ , a series circuit of thermostats 23D ₁ and 23D ₂ for detecting the end of defrost, and a compressor motor MC for defrost relay 2DX ₁ . The auxiliary relay 2DX ₂ is connected in parallel through a parallel circuit of the normally closed contact and the self-holding contact of the electromagnetic switch 88C, and the timer 2D ₂ is connected in parallel to the auxiliary relay 2DX ₂ . The solenoid relay _{2 of the quantitative outflow valve 41 is connected to a series circuit that connects in series each circuit of the parallel circuit with the timer 2D 2 that} controls the opening operation time of the quantitative outflow valve 41, and to a time limit contact of the timer 2D 2.
A series circuit (defrost control circuit) in which a parallel circuit of 0LS ₂ and auxiliary relay 2X ₇ is connected in series.

(3) Compressor protection thermometer 49, overcurrent relay OC,
High pressure switch 63H, low pressure switch 63L, hydraulic protection switch 63QL, auxiliary relay 2X ₇
A series circuit between the normally closed contact of DX and the electromagnetic switch 88C of the compressor motor (MC) (compressor motor MC start/stop control circuit) (4) Auxiliary relay ₂ The circuit of the delay timer 2F of the indoor fan motor MF _{1-1 .}
Electromagnetic switch 88F and defrost timer 2
A circuit in which a parallel circuit with D ₁ is connected in series, and a circuit in which two parallel circuits are connected in series. (Indoor fan motor control circuit) In Fig. 2, CPD is a contact protection diode, and GL and RL are lamps.
In addition, the electric part 20M of the hot gas valve 21 is formed with a direct connection circuit, separate from the control circuit of the controller 22, through which the normally open contact of the auxiliary relay 2DX ₂ is interposed, so that it can be switched to 100% opening. It's summery.

In the above configuration, the air temperature is adjusted by the set temperature set by the set point selector PS of the controller 22, and in the case of freezing operation where the set point temperature is lower than, for example, -5°C, the air temperature is adjusted by the return sensor RS on the suction side. Compressor 1 based on
In addition, in the case of refrigeration operation at 5°C or higher, the hot gas valve 21 is controlled to an opening of 0 to 100% based on the supply sensor SS on the blowout side, and the opening is controlled at this opening. This is done by bypassing the hot gas at an appropriate flow rate.

During such freezing or refrigeration operation, the evaporator 4 may become frosted and the air press switch APS may be activated, or
When the defrost timer _2D1 operates and a command to start the defrost operation is issued, the defrost operation is performed as follows.

This defrost operation will be explained according to the flowchart shown in FIG.

First, when a command to start defrost operation is issued as described above, defrost relay 2DX ₁ is energized,
The auxiliary relay _2X4 is demagnetized, the pump-down control circuit is opened, the solenoid relay _20LS1 of the on-off valve 30 is deenergized, the on-off valve 30 is closed, and pump-down operation begins.

In this pump-down operation, the liquid refrigerant is confined in the condensers 2 and 3, the liquid receiving part 7a of the liquid receiver 7, and the liquid pipe section 6c leading to the on-off valve 30, and the low pressure on the suction side of the compressor 1 decreases, and when the low pressure becomes lower than the set value of the low pressure switch 63L, the low pressure switch 63L
is turned off, the start/stop control circuit of the compressor motor MC is opened, and the electromagnetic switch 8 of the motor MC is turned off.
8C is demagnetized, the compressor 1 is stopped, and the pump-down operation is completed.

When the electromagnetic switch 88C is demagnetized, its normally closed contact closes, so the auxiliary relay 2DX ₂ in the defrost control circuit is energized, the electric part 20M of the hot gas valve 21 is operated, and the opening is switched to 100%. , and the indoor fan motor
MF _1-1 ... stops.

At the same time, the timer 2D ₂ starts operating, and its magnetic limiting contact closes to close the fixed amount outflow valve 41.
The solenoid relay _20LS2 is energized, the quantitative outflow valve 41 is opened, and the refrigerant trapped in the liquid reservoir is transferred to the compressor 1 due to the pump down operation.
It flows out to the suction side. Then, after the set time of the timer 2D ₂ has elapsed, for example, 5 seconds, the timer 2D ₂ ends its operation, opens the time contact, demagnetizes the solenoid relay 20LS ₂ , and closes the metered outflow valve 41. be. By opening and closing the quantitative outflow valve 41, a certain amount of refrigerant flows out into the defrost circuit that performs defrost operation.

Further, the opening operation of the time limit contact of the timer 2D ₂ also demagnetizes the auxiliary relay 2X ₇ and closes its normally closed contact. In this state, the low pressure increases due to the outflow of the refrigerant, and the low pressure switch is activated. 63L, the low pressure switch 63L is turned on, the compressor 1 is started, and the predetermined amount of refrigerant circulates through the defrost circuit and flows from the hot gas bypass path 20 to the evaporator 4. Defrosting is initiated by the hot gas flowing into the engine.

Note that the auxiliary relay 2X ₇ is not absolutely necessary, but
By using _the auxiliary relay ₂ Can be done more accurately.

Therefore, the defrost operation described above can be performed using a predetermined amount of refrigerant necessary for the defrost operation, which is set in advance by controlling the opening operation time of the quantitative outflow valve 41. Regardless, optimal defrost is always possible.

Incidentally, even if some of the liquid refrigerant is liquefied in the defrost operation magnet and the evaporator 4, the gas-liquid separation is performed in the accumulator section 7b, so that no liquid backflow to the compressor 1 occurs.

Then, when the defrost is finished as described above,
A thermostat 2 provided on the outlet side of the evaporator 4
Among thermostats 3D ₁ and 23D ₁ , thermostat 23D ₁ with a lower set temperature operates, so the defrost control circuit is opened and the defrost relay 2
When DX ₁ is demagnetized, the self-holding circuit of auxiliary relay 2DX ₂ is also released, the auxiliary relay 2X ₄ is demagnetized, and the solenoid relay 20LS ₁ connected in series with the normally open contact of auxiliary relay 2X ₄ is energized. Then, the on-off valve 30 opens to return to freezing operation, or during refrigeration operation, the hot gas valve 21 opens.
The controller 22 then controls the opening degree and returns to steady operation.

Furthermore, in the embodiment described above, when returning to steady operation after the end of defrost operation, the ambient temperature of the evaporator 4 is higher than that in steady operation, but the amount of refrigerant circulated during the defrost operation is controlled to a constant amount. As a result, steady operation can always be achieved without the high pressure becoming abnormally high and causing the high pressure switch 63H or overcurrent relay OC to operate. However, in cases such as when the outside temperature is abnormally high, Even though it is controlled to a constant level, the high pressure may become abnormally high. In this case, the setting of the amount of refrigerant may be reduced, but since this is a very rare case, in the embodiment shown in FIG. Interpose a parallel circuit with 24,
The solenoid valve 23 is configured to detect the temperature of the blown air, high pressure or low pressure, or outside air temperature and close it, thereby restricting the amount of refrigerant circulating through the capillary reach tube 24. The solenoid relay 20SS is connected in series through the normally closed contact of the defrost relay 2DX ₁ to the parallel circuit of the normally open contact of the auxiliary relay 2X ₅ and the sensor 23A ₂ that detects the temperature of the blown air. Therefore, under operating conditions where the outside temperature is abnormally high and the high pressure rises, the solenoid valve 23 is closed to enable operation with a reduced amount of refrigerant circulation, thereby expanding the range of possible operation. .

In the embodiment shown in FIG. 2, the electromagnetic switch 88F of the indoor fan motor MF _1-1 is connected in series with the normally closed contact of the auxiliary relay 2DX ₂ via the contact of the delay timer 2F. Because of this,
Even when the auxiliary relay 2DX ₂ is demagnetized and its normally closed contact is closed at the end of the defrost operation, the indoor fan motor MF _1-1 is not driven immediately but is driven after a predetermined time delay. It's summery.

In addition, as a method of delaying the indoor fan motor MF _1-1 . . . , other than using the delay timer 2F as described above, a high pressure switch or a low pressure switch with a different set pressure is provided separately from the high pressure switch 63H or low pressure switch 63L. , may be delayed by these switches.

In the embodiment described above, the hot gas valve 21
The opening degree of the refrigerant is controlled by using a supply sensor SS that detects the temperature of the blown air and comparing it with the set temperature, but a pressure sensor that detects the low or high pressure of the refrigerant may also be used. However, the determination may also be performed by detecting the difference between the intake air temperature and the blown air temperature.

Further, although an electric three-way valve is used as the hot gas valve 21, two two-way valves may be combined.

Further, although the above embodiments are applied to a container refrigeration system, the present invention can also be applied to other refrigerators.

Moreover, although the air-cooled condenser 2 and the water-cooled condenser 3 were used together as the condenser, a single condenser 2 or 3 may be used.

As described above, the present invention provides an on-off valve 3 located downstream of the condensers 2 and 3, which is closed in response to a defrost operation start command.
0 so that the refrigerant is confined in the liquid reservoir including the condensers 2 and 3 by pump-down operation, and the on-off valve 30 is bypassed, and the liquid reservoir is placed on the suction side of the compressor 1. Communication path 4
0, and in this communication passage 40 is provided a quantitative outflow valve 41 that opens for a certain period of time after the end of the pump-down operation and allows a certain amount of refrigerant out of the refrigerant confined in the liquid reservoir to flow out to the suction side of the compressor 1. Since the defrost operation is performed with a constant amount of refrigerant, the defrost operation can always be performed optimally regardless of the immediately preceding operating state.
That is, in the operating state immediately before the defrost operation, even if the amount of hot gas bypassed to the evaporator 4 is large, or even if it is small, including zero, during the defrost operation, the quantitative outflow valve 41 is opened for a certain period of time, Since a certain amount of refrigerant is made to flow out to the suction side of the compressor 1, the defrost operation can be performed by controlling the appropriate constant amount of refrigerant necessary for the defrost operation.Therefore, when the defrost operation is completed, The high pressure of the refrigerant will not rise above the limit or excessive current will flow through the motor of the compressor 1, which will prevent the compressor from becoming inoperable, and will always return to normal operation. This also solves the problem of too little defrost time resulting in a long defrost time.

Furthermore, since the optimal amount of refrigerant is used during defrost operation, there is no need to circulate a large amount of refrigerant unnecessarily, and the compressor input can be reduced accordingly, allowing defrost operation to be performed without wasting electricity. .

[Brief explanation of the drawing]

Fig. 1 is a refrigerant piping system diagram showing an embodiment of the refrigeration system of the present invention, Fig. 2 is an electric circuit diagram of the refrigeration system shown in Fig. 1, Fig. 3 is a flowchart of defrost operation, and Fig. 4 is It is a refrigerant piping system diagram showing a conventional example. 1... Compressor, 2, 3... Condenser, 4... Evaporator, 20... Hot gas bypass path, 30... Open/close valve, 40... Communication path, 41... Fixed amount outflow valve.

Claims (1)

[Claims] 1 (1) Hot gas discharged from compressor 1,
A hot gas valve 2 which is provided with a hot gas bypass passage 20 that bypasses the condensers 2 and 3 and bypasses the evaporator 4, and performs a defrost operation by circulating the entire amount of circulating refrigerant to the evaporator 4 during frosting.
1, the condenser 2,
An on-off valve 30 is provided on the downstream side of the on-off valve 3, which closes in response to a defrost operation start command, so that the refrigerant is confined in the liquid reservoir including the condensers 2 and 3 by pump-down operation.
0 is bypassed, and a communication passage 40 is provided which communicates the liquid reservoir with the suction side of the compressor 1, and the communication passage 40 is opened for a certain period of time after the end of the pump down operation, and the refrigerant trapped in the liquid reservoir is connected to the communication passage 40. The refrigeration system is characterized in that a quantitative outflow valve 41 is provided to cause a certain amount of refrigerant to flow out to the suction side of the compressor 1, so that defrost operation is performed with a certain amount of refrigerant.