JPH0156355B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a refrigeration system, more specifically, it is equipped with a hot gas bypass path, and guides hot gas to an evaporator to lower the internal temperature of a container or refrigerator, for example, to -5. ℃
This invention relates to a refrigeration system which controls the temperature to a chilled region higher than ~-6°C, performs defrost operation, and is equipped with a drain pan heater to heat frozen drain in the drain pan to prevent drain clogging.

(Prior Art) Conventionally, it has been possible to adjust the capacity of the evaporator and perform defrost operation by supplying part or all of the hot gas discharged from the compressor to the evaporator without supplying it to the condenser. A drain pan heater is installed in the gas bypass path to heat and liquefy frozen drain that falls from the evaporator into the drain pan during defrost operation, for example, as described in "Daikin Industries, Ltd., September 1981. , Daikin Marine Container Refrigeration System Service Guide, and
Published in July 1983, Daikin Marine Container Refrigeration System
PARTSLIST" is already known.

FIGS. 4 and 5 schematically show this conventional device.
To explain based on the diagram, as shown in Figure 4,
The condenser C and the expansion valve are installed in the middle of the high pressure gas pipe B connecting the discharge side of the compressor A and the inlet side of the condenser C.
Connect the hot gas bypass path H that bypasses the EV,
The outlet of this hot gas bypass path H is connected to the evaporator E.
At the same time, it is connected to the inlet side of the hot gas bypass path H and the high pressure gas pipe B to control the amount of hot gas bypass to the evaporator E to adjust the capacity. A hot gas valve HV is provided which circulates hot gas to the evaporator E to perform a defrost operation, and the hot gas valve HV directly supplies a part of the hot gas flowing in the high pressure gas pipe B to the evaporator E. The temperature of the air blown out of the evaporator and the internal temperature of the refrigerator are controlled to a chilled region, and the hot gas valve HV directly supplies the entire amount of the hot gas to the evaporator E to perform defrost operation, while the hot gas bypass path H A drain pan heater DH is interposed in the middle, and this drain pan heater DH is laid in a meandering manner on the drain pan D disposed below the evaporator E as shown in FIG. At this time, the frozen drain that has fallen into the drain pan D in a frozen state without being completely liquefied is thawed by the hot gas flowing through the drain pan heater DH, thereby preventing so-called drain clogging in which the frozen drain blocks the drain outlet of the drain pan. ing.

(Problem to be Solved by the Invention) However, in this conventional device, both when adjusting the capacity of the evaporator E and during defrost operation, the hot gas passes through the drain pan heater DH, so the evaporation When adjusting the capacity of the evaporator E, the air blown out from the evaporator fan F passes through the evaporator E, and then is divided into left and right sides along the drain pan D to be distributed from the bottom of both sides into the container warehouse. The air cooled by the drain pan heater DH is heated by the drain pan heater DH. As a result, when controlling the temperature inside the refrigerator to the optimum temperature for the objects to be cooled, it becomes necessary to set the cooling temperature by the evaporator E to a low value in consideration of the temperature corresponding to the reheating temperature by the drain pan heater DH. be.

However, when the cooling temperature by this evaporator E is lowered, the dehumidifying capacity of the evaporator E increases, so the moisture in the blown air decreases, and the objects to be cooled, such as vegetables, stored in the refrigerator. There is a problem that it causes loss of weight and quality deterioration.

The present invention aims to solve the problem of dehumidification caused by reheating of the drain pan heater when adjusting the capacity of the evaporator in conventional equipment. By installing a device to supply hot gas to the evaporator without flowing it to the drain pan heater when adjusting the capacity of the evaporator, reheating by the drain pan heater is eliminated when adjusting the capacity, and the weight of the cooled object due to dehumidification is reduced. This solution is designed to solve problems caused by poor quality and problems caused by deterioration in quality.

(Means for Solving the Problems) Therefore, as shown in FIGS. 1 to 3, the present invention bypasses the condenser 2 and directs the hot gas discharged from the compressor 1 to the evaporator 4. A hot gas bypass passage 10 to be bypassed, and a hot gas valve 11 that controls the amount of hot gas bypassed to the evaporator 4 to adjust the capacity, and circulates the hot gas to the evaporator 4 during frosting to perform a defrost operation. and a drain pan heater 12 interposed in the middle of the hot gas bypass path 10, and the drain pan heater 12 is located on the air blowing side of the evaporator 4. A short-circuit passage 14 is provided to bypass the drain pan heater 12, and a valve device 15 is provided in the hot gas bypass passage 10 to allow hot gas to flow through the drain pan heater 12 during defrost operation and to shut off the flow during capacity adjustment. .

The valve device 15 includes one using one two-way solenoid valve (Fig. 1), one using one three-way solenoid valve (Fig. 2), and one using two two-way solenoid valves (the third one).
(Figure).

(Function) When adjusting the capacity of the evaporator 4, the hot gas valve 11
while opening the valve device 15, controlling the valve device 15 so that hot gas does not flow to the drain pan heater 12;
Hot gas is supplied to the evaporator 4 from the bypass path 10 and the short circuit path 14 to prevent the air temperature from increasing due to the drain pan heater 12 and prevent moisture in the air from being dehumidified. Upon opening, the valve device 15
The hot gas is controlled to flow from the hot gas bypass passage 10 and the drain pan heater 12 to the evaporator 4 to heat and thaw the frozen drain in the drain pan.

(Example) Next, an example of the present invention will be described based on the drawings.

The first embodiment shown in FIG. 1 is a container refrigeration system, and in FIG. 1, 1 is a compressor;
2 is an air-cooled condenser, 3 is a water-cooled condenser, 4 is an evaporator,
5 is a temperature-sensitive expansion valve having a temperature-sensing portion 51; 6 is a liquid receiver in the form of a single accumulator; 7 is a dryer; and 8 is a liquid indicator; each of these devices is connected by a refrigerant pipe 9; Evaporator 4
This forms a refrigeration cycle that cools the air inside the refrigerator.

Further, the high pressure gas pipe 9a connecting the discharge side of the compressor 1 and the inlet side of the air condenser 2 is provided with the compressor 1.
The hot gas discharged from each condenser 2,
3. A hot gas bypass path 10 bypassing the liquid receiver 6 and the temperature-sensitive expansion valve 5 and leading to the evaporator 4 is connected, and its outlet is connected to the low-pressure liquid between the expansion valve 5 and the evaporator 4. A hot gas valve 11 is connected to the high pressure gas pipe 9a and connected to the high pressure gas pipe 9a, and a hot gas valve 11 is provided at the connection portion of the hot gas bypass path 10 to the high pressure gas pipe 9a. is supplied to the evaporator 4 via the hot gas bypass path 10 to adjust the capacity of the evaporator 4, and the hot gas in the high pressure gas pipe 9a is supplied to the evaporator 4 via the hot gas bypass path 10. While supplying the hot gas to the evaporator 4 and performing a defrost operation, a drain pan heater 12 is interposed in the middle of the hot gas bypass path 10,
During the defrost operation, the frozen drain that has fallen into the drain pan 13 in a frozen state without being completely liquefied is thawed by the drain pan heater 12.

The hot gas valve 11 is mainly an electric three-way valve that can control the valve opening degree to the hot gas bypass passage 10 from 0% to 100% in proportion to the voltage, and controls the hot gas bypass passage to the evaporator 4. In addition to controlling the amount of refrigerant to adjust the capacity, the entire amount of refrigerant circulating during frosting is transferred to the hot gas bypass path 10.
PID control is performed by the controller 110 using a proportional control valve designed to allow the air to flow through the air.

This PID control (Proportional−plus−integral
-plus-derivative control) refers to control in which the control signal is proportional to the sum of the deviation signal, its integral, and its function.

Thus, in this refrigeration system, the hot gas bypass path 10 is provided with a short circuit path 14 that bypasses the drain pan heater 12, while the hot gas bypass path 10 is configured to allow hot gas to flow through the drain pan heater 12 during defrost operation. A valve device 15 is provided to cut off the flow of hot gas to the drain pan heater 12 during capacity adjustment.

In the embodiment shown in FIG.
During defrost operation, the hot gas valve 11 and the valve device 15, which mainly consists of a two-way solenoid valve, are opened to direct the hot gas to the drain pan heater 1.
2 and is supplied to the evaporator 4 from this drain pan heater 12.

Further, when adjusting the capacity, the hot gas valve 11 is opened, while the two-way solenoid valve that is the valve device 15 is closed, and the hot gas is caused to flow through the short-circuit passage 14 and supplied to the evaporator 4 from this short-circuit passage 14. hand,
Hot gas is prevented from flowing through the drain pan heater 12.

In addition, the short-circuit passage 14 has a hot gas flow resistance larger than that of the drain pan heater 12, and specifically, the short-circuit passage 14 is formed to have an outer diameter of 9.5 m/m, and the drain pan heater The outer diameter of the drain pan heater 12 is formed to be 12.7 m/m so that a larger amount of hot gas flows into the drain pan heater 12 than through the short circuit path 14 during defrost operation, so that a sufficient heating amount of the drain pan heater 12 can be secured. There is.

Therefore, when adjusting the capacity, the hot gas can be supplied to the evaporator 4 from the hot gas bypass passage 10 and the short circuit passage 14 without flowing to the drain pan heater 12. The air that comes out is drain pan heater 12
As a result, it is not necessary to set the cooling temperature of the evaporator 4 lower than the optimal internal temperature for the objects to be cooled, as is the case with conventional methods. This prevents the objects to be cooled, such as vegetables, from becoming thinner or deteriorating in quality.

Further, in the second embodiment shown in FIG. 2, a three-way solenoid valve is used as the valve device 15, and this three-way solenoid valve is provided at the connection portion of the inlet of the short circuit passage 14 with the hot gas bypass passage 10. During the defrost operation, the flow of hot gas to the short-circuit passage 14 is cut off, and the hot gas is made to flow only to the drain pan heater 12. On the other hand, when adjusting the capacity,
This allows switching control to be performed in the opposite direction to that during defrost operation. In this case, during defrost operation, the entire amount of hot gas can be distributed to the drain pan heater 12, so the capacity of the drain pan heater 12 can be increased compared to the one shown in FIG. 1, and the time required to thaw the frozen drain in the drain pan can be shortened. It is possible. When adjusting the capacity, reheating of the air can be prevented as in the first embodiment.

Further, in the third embodiment shown in FIG. 3, two two-way solenoid valves are used as the valve device 15, and these two-way solenoid valves are installed at the inlet of the drain pan heater 12 in the hot gas bypass path 10 and at the inlet of the drain pan heater 12 and Short circuit path 1
During defrost operation, the solenoid valve on the drain pan heater 12 side is opened, and the solenoid valve on the short circuit passage 14 side is closed to block the flow of hot gas to the short circuit passage 14, and the drain pan heater This was done by allowing hot gas to flow only through 12. In this case as well, as in the case of FIG. 2, the time required to thaw the frozen drain can be shortened. When adjusting the capacity, as in the first and second embodiments,
Prevents air from reheating.

In the refrigeration system of the first embodiment shown in FIG. 1, a stop command for freezing operation or refrigeration operation and a command for defrosting operation are provided on the downstream side of the condenser 3, specifically, on the downstream side of the liquid indicator 8. An electromagnetic on-off valve 21 that closes upon a start command is provided to enable pump down operation, and the condensers 2 and 3 and the liquid receiver 6
The refrigerant is trapped in a liquid reservoir including a liquid receiving part, and a defrost circuit that defrosts a certain amount of the refrigerant trapped in the liquid reservoir, that is, the compressor 1 and the hot gas valve. 11, a fixed amount outflow mechanism 20 is provided for outflowing to a defrost circuit consisting of a hot gas bypass path 10, an evaporator 4, and an accumulator section of a liquid receiver 6.

This quantitative outflow mechanism 20 includes, for example, the on-off valve 2
1, an electromagnetic on-off valve 22 is installed at a position where a predetermined outflow amount can be obtained, with respect to the interposed position where the on-off valve 21 is installed, of the liquid reservoir part which performs a pump-down operation and confines the refrigerant when the refrigerant is closed. In FIG. 1, the on-off valve 21 is configured as follows.
The on-off valve 22 is installed on the inlet side of the expansion valve 5 in the high pressure liquid pipe 9c connecting the liquid indicator 8 and the expansion valve 5, and the on-off valve 22 is installed on the outlet side of the liquid indicator 8 in the high pressure liquid pipe 9c. A fixed amount of refrigerant is interposed between the on-off valves 21 and 22 of the high-pressure liquid pipe 9c and is made to flow out by closing the on-off valve 22 and opening the on-off valve 21. .

The amount of refrigerant set by the fixed amount outflow mechanism 20 is set to an optimum amount so that the steady operation performed after the defrost operation is always kept within the operable range regardless of the operating state, and the defrost time is not prolonged. .

Further, a solenoid valve 26 that is energized and closed and a capillary reach tube 27 are connected in parallel in the middle of the suction gas pipe 9d that connects the inlet side of the compressor 1 and the liquid receiver 6.

The solenoid valve 26 allows the suction gas refrigerant to flow into the capillary reach tube 2 by closing the solenoid valve 26.
The refrigerant is returned to the compressor 1 through the refrigerant 7, and the amount of refrigerant circulated is reduced.The amount of refrigerant is reduced in this way when the outside temperature is high, when steady operation starts after defrosting, or when pulling down. This is to prevent the high and low pressures of the refrigerant from increasing and overloading, and due to the reduction in the amount of circulation, the amount of work of the compressor 1 is reduced, and the high pressure and the current value of the compressor motor are reduced. This allows the operating range to be expanded.

The solenoid valve 26 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 falls below a certain value.

In the above configuration, the hot gas valve 11 is
The system is controlled by an output signal from the controller 110 and a command to start the defrost operation, and the opening/closing valve 21 is closed by the command to start the defrost operation, and a pump down operation is performed.
Furthermore, the end of the pump down operation and the start of the defrost operation are mainly controlled using the low pressure switch 63L.

The command to start the defrost operation mainly uses an air pressure switch and a defrost timer whose set time is, for example, 12 hours. In this case, the air pressure switch is
It takes priority over the defrost timer and operates the air pressure switch to reset the defrost timer.

The defrost operation is terminated by, for example, attaching two thermostats with different set temperatures to the low pressure gas pipe 9e on the outlet side of the evaporator 4 and detecting the temperature of the low pressure gas pipe 9e.

In addition, _F1 in the figure is a fan attached to the evaporator 4,
F ₂ is a fan attached to the air-cooled condenser 2, 63
H is a high pressure switch, 63CL is a high pressure control switch,
63QL is a hydraulic protection switch, and 63W is a water pressure switch.

Next, the effect when the quantitative outflow mechanism 20 is provided will be explained.

First, during freezing or refrigeration operation, when a defrost operation start command is issued, the on-off valve 21 closes and pump-down operation begins.

In this pump-down operation, the liquid refrigerant is transferred to the condensers 2 and 3, the liquid receiving part of the liquid receiver 6, and the on-off valve 2.
While being confined in the liquid pipe portion 9c leading to 1,
When the low pressure on the suction side of the compressor 1 decreases and the low pressure becomes lower than the set value of the low pressure switch 63L, the low pressure switch 63L is turned off, the compressor 1 is stopped, and the pump down operation is started. ends.

Then, the hot gas valve 11 is switched to 100% opening, the indoor fan motor MF ₁ is stopped, and at the same time the on-off valve 22 is closed and the on-off valve 21 is opened.

As described above, when the on-off valve 22 is closed and the on-off valve 21 is opened, there is a difference between high and low pressures, so a certain amount of liquid refrigerant trapped in the high-pressure liquid pipe 9c between these on-off valves 21 and 22 is converted into gas. This will lead to the leakage. The reason why this liquid refrigerant gasifies and flows out to the evaporator 4 side is that the volume of the defrost circuit is considerably larger than the volume of the refrigerant stored in the quantitative outflow mechanism 20, and that the pump-down operation causes the evaporator 4 to flow out. Since the outlet side refrigerant is in a superheated state, the expansion valve 5 is open;
Immediately after the opening/closing valve 21 is opened, the liquid refrigerant becomes normal due to the pressure drop, and therefore flows out to the evaporator 4 side in a liquid-gas mixed state. The amount of refrigerant stored in the outflow mechanism 20 is small, and the above-mentioned part of the liquid refrigerant can be sufficiently evaporated with the heat capacity possessed by the high-pressure liquid pipe 9c itself and the amount of heat taken up from the outside air temperature via the high-pressure liquid pipe 9c.

Due to this outflow, the low pressure increases and becomes higher than the set value of the low pressure switch 63L, so the low pressure switch 63L is turned on, the compressor 1 is started, and the above-mentioned fixed amount of refrigerant circulates through the defrost circuit. Defrosting can be performed by the hot gas flowing into the evaporator 4 from the hot gas bypass path 10.

This defrost operation is performed by the quantitative outflow mechanism 20.
Since the defrost is carried out using a fixed amount of refrigerant set by the above, optimal defrosting is always possible regardless of the operating state immediately before the defrosting operation.

During this defrosting operation, even if some of the refrigerant is liquefied in the evaporator 4, gas-liquid separation is performed in the accumulator section of the liquid receiver 6, so that no liquid backflow to the compressor 1 occurs.

Then, when the defrost is finished as described above,
Of the two thermostats installed on the outlet side of the evaporator 4, the thermostat with the lower set temperature operates, so the defrosting ends, the on-off valves 21 and 22 open, and the refrigeration operation returns or refrigeration begins. During operation, the opening of the hot gas valve 11 is controlled by the controller 110 and returns to normal operation.

Note that when the defrost operation returns to normal operation after the defrost operation, the ambient temperature of the evaporator 4 is higher than that of the normal operation, but since the refrigerant circulation amount during the defrost operation is controlled to a constant amount, Steady operation is always possible without the high pressure switch 63H or overcurrent relay being activated due to abnormally high high pressure.However, in cases such as when the outside temperature is abnormally high, it is necessary to control the amount of refrigerant to a constant level. The high pressure may become abnormally high even though the In this case, the setting of the refrigerant amount may be reduced, but
Since this is a very rare case, in the embodiment shown in FIG. It is configured to detect air temperature, high pressure, low pressure, or outside air temperature and close it, and throttle the refrigerant circulation amount through the capillary reach tube 27. Therefore, under operating conditions where outside air temperature is abnormally high and high pressure increases, Therefore, the electromagnetic valve 26 is closed to enable operation by reducing the amount of refrigerant circulated, thereby expanding the operable range.

The three embodiments described above are the hot gas valve 1
Although an electric three-way valve is used as the first valve, two two-way valves may be used in combination.

Furthermore, the above-described refrigeration system is applied to a container refrigeration system in which a drain pan 13 is provided on the air outlet side of the evaporator 4 as shown in FIG.
It 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.

(Effect of the invention) As described above, the present invention provides the drain pan heater 12
A short-circuit passage 14 is provided in the hot gas bypass passage 10 that bypasses the drain pan heater 12, while hot gas is allowed to flow through the drain pan heater 12 during defrost operation, and the flow is controlled during capacity adjustment. Valve device 1 to shut off
5, it is possible to reliably prevent the air exiting the evaporator 4 from being heated by the drain pan heater 12 when adjusting the capacity, and the cooling temperature of the evaporator 4 can be controlled by the temperature of the drain pan heater 12. There is no need to set the temperature high according to the amount of heat; in other words, the temperature can be set to the optimum temperature corresponding to the object to be cooled. Therefore, there is no need to adjust the cooling temperature of the evaporator 4 to be lower than the optimum temperature of the objects to be cooled housed in the refrigerator as in the conventional case, so it is possible to prevent the dehumidifying capacity from increasing and to prevent the objects to be cooled from becoming thinner. And quality deterioration can be prevented.

[Brief explanation of drawings]

FIG. 1 is a refrigerant piping system diagram showing the first embodiment of the refrigeration system of the present invention, FIGS. 2 and 3 are refrigerant piping system diagrams with some parts omitted, showing the second and third embodiments, and FIG.
The figure is a refrigerant piping system diagram of a conventional example, and FIG. 5 is a schematic configuration diagram of a conventional container. 1... Compressor, 2... Condenser, 4... Evaporator,
10... Hot gas bypass path, 11... Hot gas valve, 12... Drain pan heater, 14... Short circuit passage, 15... Valve device.

Claims (1)

[Claims] 1. A hot gas pipeline 10 that bypasses the condenser 2 and bypasses the hot gas discharged from the compressor 1 to the evaporator 4, and controls the amount of hot gas bypassed to the evaporator 4 to adjust the capacity; It also includes a hot gas valve 11 that circulates the hot gas to the evaporator 4 during frosting to perform a defrost operation, and a drain pan heater 12 interposed in the middle of the hot gas bypass path 10, so that the drain pan heater 12 is connected to the evaporator. 4, the hot gas bypass passage 10 is provided with a short circuit passage 14 that bypasses the drain pan heater 12, and the hot gas bypass passage 10 is provided with a short circuit passage 14 that bypasses the drain pan heater 12 during defrost operation. A refrigeration system characterized in that a valve device 15 is provided to allow hot gas to flow through the refrigeration system 12 and to shut off the flow during capacity adjustment.