JPH06201233A - Defrosting method in heat pump type air-conditioner - Google Patents

Abstract

PURPOSE:To shorten a defrosting time by reducing a thermal radiation loss during a defrosting operation. CONSTITUTION:At an initial stage of defrosting operation, an opening or closing valve 7 is opened, a part of discharged refrigerant gas of a compressor 1 is fed through a hot gas bypassing circuit 8 into an outdoor heat exchanger 5 so as to perform a positive cycle defrosting operation and then the opening or closing valve 7 is closed and in concurrent with this operation, a four-way changing-over valve 2 is changed over so as to perform a reverse cycle defrosting operation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defrosting method for a heat pump type air conditioner.

[0002]

2. Description of the Related Art One example of a conventional heat pump type air conditioner is shown in FIG. During the heating operation, the high-temperature and high-pressure gas refrigerant discharged from the compressor 1 enters the indoor heat exchanger 3 via the four-way switching valve 2 and heats the indoor air to condense into a liquid refrigerant. The liquid refrigerant is adiabatically expanded by being throttled by a throttling mechanism 4 such as an expansion valve, and then enters the outdoor heat exchanger 5, where it absorbs heat from the outside air to be evaporated and vaporized into a gas refrigerant. This gas refrigerant returns to the compressor 1 via the four-way switching valve 2.

During cooling operation, the four-way switching valve 2 is switched in the opposite manner. Thus, the refrigerant discharged from the compressor 1 returns to the compressor 1 via the four-way switching valve 2, the outdoor heat exchanger 5, the throttle mechanism 4, the indoor heat exchanger 3, and the four-way switching valve 2.

When the heating operation is performed at a low outside temperature, frost is attached to the surface of the outdoor heat exchanger 5, so that the defrost operation is performed regularly or by a command.

During this defrost operation, the on-off valve 7 provided in the hot gas bypass circuit 8 is opened. Then, one of the high temperature and high pressure gas refrigerant discharged from the compressor 1
Part is branched from the discharge pipe 6 and introduced into the outdoor heat exchanger 5 through the hot gas bypass circuit 8 and the on-off valve 7, and after melting the frost adhering to the outer surface in the process of flowing through the outdoor heat exchanger 5. , And returns to the compressor 1 via the four-way switching valve 2.

[0006]

In the above-mentioned conventional positive cycle defrost system, since the gas refrigerant has a large amount of heat near the lower portion of the outdoor heat exchanger 5 into which the discharged gas refrigerant is introduced, the melting speed of frost is high. . However, since the gas refrigerant releases most of the effective heat amount for defrost before reaching the upper part of the outdoor heat exchanger 5, the melting speed of frost becomes slow near the upper part of the outdoor heat exchanger 5. For this reason, in the latter half of the defrost operation, heat is radiated from the lower part of the outdoor heat exchanger 5 to the outside air, so that there is a problem that the heat loss increases and the time required for defrosting becomes long.

In order to deal with this, a reverse cycle defrost system has been proposed in which the four-way switching valve 2 is switched in the same way as during the cooling operation to circulate the refrigerant in the opposite direction to that during the heating operation. There were problems such as pressure fluctuation noise when switching the four-way switching valve and deterioration of indoor air conditioning feeling due to interruption of heating operation.

[0008]

SUMMARY OF THE INVENTION The present invention has been invented to solve the problems, and its gist is to include a compressor, a four-way switching valve, an outdoor heat exchanger, a throttle mechanism and an indoor heat. A heat pump type air conditioner having a heat pump cycle in which exchangers are connected in this order, and a hot gas bypass circuit that guides refrigerant gas discharged from the compressor to a refrigerant inlet side during heating of the outdoor heat exchanger through an on-off valve. In the initial stage of defrost operation, the on-off valve is opened and a part of the discharged refrigerant gas is introduced into the outdoor heat exchanger through the hot gas bypass circuit, while the remaining discharged refrigerant gas is discharged to the compressor and the four-way switching valve. , Indoor heat exchanger, throttling mechanism and outdoor heat exchanger are circulated in this order to perform normal cycle defrost, and then the on-off valve is closed and the four-way switching is performed at the same time. Defrost of the heat pump type air conditioner characterized by performing the reverse cycle defrost by circulating the discharged refrigerant gas in order of the compressor, the four-way switching valve, the outdoor heat exchanger, the throttling mechanism and the indoor heat exchanger by switching On the way.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT One embodiment of the present invention is shown in FIGS.
FIG. 1 is a flowchart and FIG. 2 is a system diagram. As shown in FIG. 2, a temperature sensor 9 is attached near the midpoint of the outdoor heat exchanger 5. The detected value of the temperature sensor 9 and the defrost start command 10 are input to the controller 11,
The output signal of the controller 11 is input to the four-way switching valve 2 and the opening / closing valve 7. Other configurations are similar to those of the conventional one shown in FIG. 3, and corresponding members are designated by the same reference numerals.

When the defrost start command 10 is input to the controller 11 during the heating operation, the defrost operation is started. Then, as shown in the flowchart of FIG. 1, the opening / closing valve 7 is opened in steps, and a part of the high temperature / high pressure refrigerant gas discharged from the compressor 1 is discharged into the discharge pipe 6, the hot gas bypass circuit 8, and the opening / closing valve 7. After being introduced into the outdoor heat exchanger 5, so-called normal cycle defrost operation is performed.

By this normal cycle defrost operation, the frost adhering to the outdoor heat exchanger 5 is melted upward from the lower part of the outdoor heat exchanger 5. If it is determined that the detected temperature t _h of the temperature sensor 9 which melting of the frost is provided near the middle point of the outdoor heat exchanger 5 in step proceeds exceeds the set value t _s1, closing valve 7 is closed in step Then, the four-way switching valve 2 is switched to the reverse cycle in step.

Thus, the refrigerant discharged from the compressor 1 circulates to the compressor 1 via the four-way switching valve 2, the outdoor heat exchanger 5, the throttle mechanism 4, the indoor heat exchanger 3 and the four-way switching valve 2, so-called reverse. Cycle defrost operation is performed.

By this reverse cycle defrost operation, high-temperature and high-pressure gas refrigerant is introduced from the upper part of the outdoor heat exchanger 5 and moves downward, and the frost adhering to the outdoor heat exchanger 5 moves downward from the upper part of the outdoor heat exchanger 5. Melting progresses toward.

In step, the temperature detected by the temperature sensor 9 is t _h
When it is determined that the temperature exceeds the set value t _s2 , the four-way switching valve 2 is switched to the heating cycle, that is, the positive cycle, and the defrost operation ends in step.

However, by the normal cycle defrost operation in the initial stage of the defrost operation, the discharged gas refrigerant flows in from the lower part of the outdoor heat exchanger 5 to melt the frost from the lower part of the outdoor heat exchanger 5 to the vicinity of the intermediate point, and then, In the reverse cycle defrost operation, the discharged refrigerant gas flows in from the upper part of the outdoor heat exchanger 5 and melts the frost from the upper part of the outdoor heat exchanger 5 to the vicinity of the intermediate point, so that the heat of the discharged refrigerant gas is transferred to the outdoor heat exchanger. Unnecessarily radiating heat to the outside from the lower part of 5 can be prevented, and therefore the defrost time can be shortened.

Further, during the normal cycle defrost operation, the difference between the discharge pressure and the suction pressure of the compressor is almost halved as compared with that during the heating operation, so that noise due to pressure fluctuation when switching to the reverse cycle defrost operation is reduced. You can.

[0017]

In the present invention, at the initial stage of the defrost operation, the on-off valve is opened and a part of the discharged refrigerant gas is introduced into the outdoor heat exchanger through the hot gas bypass circuit to perform the normal cycle defrost, and then, Since the on-off valve is closed and the four-way switching valve is switched at the same time to perform reverse cycle defrosting, the heat of the discharged refrigerant gas is prevented from being unnecessarily dissipated from the defrosted portion of the outdoor heat exchanger into the outside air, and Since it can be effectively used for melting, the defrost time can be shortened. Further, since the difference between the discharge pressure and the suction pressure of the compressor is small during the positive cycle defrost, the noise due to the pressure fluctuation when switching to the reverse cycle defrost is also small. Since the reverse cycle defrost time is short and sufficient, it is possible to prevent the heating feeling from deteriorating.

[Brief description of drawings]

FIG. 1 is a flowchart according to one embodiment of the present invention.

FIG. 2 is a system diagram of the above embodiment.

FIG. 3 is a system diagram of a conventional air conditioner.

[Explanation of symbols]

 1 Compressor 2 4-way switching valve 3 Indoor heat exchanger 4 Throttle mechanism 5 Outdoor heat exchanger 7 Open / close valve 8 Hot gas bypass circuit

Claims (1)

[Claims] 1. A heat pump cycle in which a compressor, a four-way switching valve, an outdoor heat exchanger, a throttle mechanism, and an indoor heat exchanger are connected in this order, and refrigerant discharged from the compressor is passed through an on-off valve to open the outdoor heat. In a heat pump type air conditioner having a hot gas bypass circuit leading to the refrigerant inlet side during heating of the exchanger, in the initial stage of defrost operation, the on-off valve is opened to partially discharge the discharged refrigerant gas through the hot gas bypass circuit. At the same time when the remaining refrigerant gas is introduced into the outdoor heat exchanger, the compressor, the four-way switching valve, the indoor heat exchanger,
Forward cycle defrost is performed by circulating the throttle mechanism and the outdoor heat exchanger in this order, and then the on-off valve is closed and the four-way switching valve is switched at the same time to switch the discharged refrigerant gas to the compressor, the four-way switching valve, and the outdoor heat exchange. A method for defrosting a heat pump type air conditioner, characterized in that reverse cycle defrosting is performed by sequentially circulating a heater, a throttle mechanism and an indoor heat exchanger.