JPS6123456B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a defrosting method for a heat pump type refrigerator, and its main purpose is to prevent the growth of an ice layer around an outdoor air heat exchanger that is a heat source during heat pump operation. .

Generally, heat pumps that use air as a heat source obtain heat for heating from low-temperature outside air using an air heat exchanger installed outdoors, so the temperature of the heat exchanger is 0°C.
There are many cases where frost formation occurs when the temperature is lower than that.

However, if frost adheres to the surface of the heat exchanger, the amount of heat pumped up from the air heat exchanger will decrease, so it is preferable to operate the heat pump in a frost-free state as much as possible. For this purpose, Utsukai Showa 51-154454
As shown by the dashed line in Figure 3, the publication states that when the outside air temperature is above a predetermined temperature (6°C), defrosting is started using only the evaporator temperature;
A defrost device is proposed which starts defrosting in relation to the outside air temperature and the evaporator temperature if the temperature is lower than 0.3 °C. However, when the outside air temperature is between 2°C and 6°C, which is slightly lower than 6°C, frost builds up unevenly on a part of the air heat exchanger, so the proposed defroster cannot defrost completely. However, the drawback that water droplets during defrosting remain as an ice layer without contacting the air heat exchanger and prevent heating heat from being pumped from the air heat exchanger cannot be solved.

The present invention, which was made in view of these points, will be explained below with reference to the drawings. Fig. 1 is a basic configuration diagram of an air heat source type heat pump, where 1 is a refrigerant compressor and 2 is an air heat exchanger installed outdoors. , 3 is a heat exchanger for indoor air conditioning and heating, and 4 is an expansion valve, and the refrigerant flow direction is indicated by the solid line arrow (during heat pump heating) or the dotted line arrow, depending on the operating status of cooling, heating, and defrosting. The air heat exchanger 2 is air-tightly connected via a four-way valve 5 that switches between two directions (during defrosting and cooling in the heat pump) to configure the refrigeration cycle of the air source heat pump. The indoor heating and cooling heat exchanger 3 works as a condenser, and during cooling, the air heat exchanger 2
is made to work as a condenser, and the indoor heat exchanger 3 works as an evaporator.

Further, a blower 6 and a sensor 7 for detecting the air heat exchanger temperature are attached to the air heat exchanger 2, and input from the sensor and a sensor 8 for detecting the outside air temperature at the location where the air heat exchanger 2 is installed are provided. The defrosting controller 9, which operates during heat pump operation, switches the four-way valve 5 based on the input from the four-way valve 5.

Fig. 2 shows an example of a circuit for implementing such a defrosting controller, and 7 and 8 are the heat exchanger temperature detection sensor and the outside temperature detection sensor shown in Fig. 1. A temperature-to-electrical quantity conversion element such as the above is used, and is connected to bus bars 10, 10' from a DC power source. 11 is bus line 1
It has input terminals 12 and 12' from 0 and 10', and based on the input from the midpoint T between the heat exchanger temperature detection sensor 7 and the outside air temperature detection sensor 8, A and 10' in FIG. The defrosting start switching circuit 13 which outputs the output with characteristics like B is also connected to the input terminal 1.
4, 14', and the midpoint T of the detection sensors 7, 8
15 is a defrosting release switching circuit that outputs an output with characteristics as shown in FIG. At times, the relay 18 is activated by the output of the switching circuit 11 for starting defrosting.
This is a thermostat that switches and connects the two output ends 19 and 19' to the relay 15 side.When the outside air temperature where the air heat exchanger 2 is installed is below 2℃, the output side is connected to the A19 side, and when the temperature is above 6℃ When output side B1
9', and between 2°C and 6°C, the relay 15 is activated as a differential for the thermostat 18 with an output as shown by the dotted line in FIG. Switching works.

The thermostat 18 may be a separate mechanical thermostat, but if the wiring length is long, an appropriate switching circuit is activated based on the input from the outside temperature detection sensor 8, and the terminals 19, 1
9' may also be switched.

Taking such a configuration as an example, in the defrosting method of the present invention having the defrosting operation characteristics as shown in FIG. 3, an air heat exchanger pumps heat for heating from outdoor air as an evaporator during heat pump operation. If frost or ice adheres to the container, if the outside air temperature where the air heat exchanger (evaporator) is installed is below 2 to 6 degrees Celsius, defrost it at a temperature below the evaporator temperature according to characteristic A. The four-way valve 5 is switched by the relay 15,
While the refrigerant flows as shown by the dotted line arrow in Figure 1,
When the outside air temperature is 2 to 6°C or higher, the four-way valve 5 is switched to perform defrosting at a temperature below the evaporator temperature according to characteristic B, and the defrosting start temperature and defrosting release are determined under each outside air temperature condition. The temperature difference D _A and D _B is 2 of the outside temperature for both characteristics A and B.
The temperature difference when the temperature is between 6°C and 6°C can be set to be smaller than the temperature difference when the outside air temperature is 2°C or lower or 6°C or higher.

Note that the characteristics A, B, and C may not necessarily be straight lines but may be curved lines.

In the defrosting method of the present invention, when the outside air temperature is 2°C or less, the temperature of the evaporator tends to drop rapidly due to frost adhering to the windward side of the evaporator, so the temperature difference D _A is Even if the temperature is set to be higher when the outside temperature is lower, there is no risk of malfunctioning when defrosting starts, and defrosting can be performed in the same way as conventional defrosting without frequent starting and canceling of defrosting.

Also, when the outside air temperature is 6℃ or higher, the temperature of the outside air passing through the evaporator will not drop below ~0℃, so there is no need for defrosting in theory, but during actual operation, defrosting is not necessary. Under such special conditions, the method of the present invention can generate ice in a portion of the air heat exchanger, which may throttle the expansion valve and cause the evaporator temperature to drop extremely. The temperature difference D _B is set large so that defrosting is started only when summer is detected, and defrosting is not normally performed, but once defrosting is started, it is ensured that the ice layer is This ensures that the defrost is removed and that defrosting is not started due to malfunction.

Furthermore, when the outside temperature is between 2°C and 6°C, defrosting can be performed more frequently than when the outside temperature is below 2°C or above 6°C by bringing the defrosting start temperature closer to the defrosting release temperature. This makes it possible to defrost the evaporator at the initial stage of frost formation.
As a result, frost formation on the evaporator is not just frost, but rather, the condensed water tends to grow as an ice layer.Insufficient defrosting under such outside temperature conditions, e.g. Conventionally, the ice layer simply detaches without contacting the heat pump, and the ice layer does not melt, making it difficult to remove the remaining ice layer that obstructs the flow of air to the outdoor heat exchanger that pumps heat from the heat pump. Solving the drawbacks of this type of defrosting method,
This enables efficient heat pump operation by performing defrosting that is appropriate for each outside temperature condition.

[Brief explanation of the drawing]

Fig. 1 is a basic circuit configuration diagram of an air source heat pump, Fig. 2 is an electric circuit diagram showing an example of a defrosting controller implementing the method of the present invention, and Fig. 3 is a characteristic of defrosting operation according to the method of the present invention. FIG. 3 is a diagram showing the characteristics of defrosting operation by a conventional device. 2... Air heat exchanger, 7... Heat exchanger temperature detection sensor, 8... Outside temperature detection sensor.

Claims (1)

[Claims] 1. In a heat pump type refrigerator in which the set temperature for starting defrosting and the set temperature for defrosting release on the air heat exchanger side are changed according to the outside temperature of the place where the air heat exchanger as a heat source is installed, When the outside air temperature is between 2℃ and 6℃, the temperature difference between the set temperature to start defrosting and the set temperature to release defrost is calculated as follows:
A defrosting method for a heat pump refrigerator that is set to be smaller than when the temperature is below ℃ or above 6℃.