JPH03230063A - Heat exchanger for heat pump type air conditioner - Google Patents

Abstract

PURPOSE:To keep the most appropriate number of passes during an evaporating operation and during a condensing operation and provide the most active application of a capability of a heat exchanger for a heat pump type air conditioner by a method wherein the number of passes in a coolant circuit during the condensing operation is lower than that in the coolant circuit during an evaporating operation through a changing-over of a four-way valve. CONSTITUTION:During an evaporating operation, a coolant is flowed from a coolant pipe 2'', passes through a coolant pipe 2c through a four-way valve 4, branched at a branch pipe 3a into two passes and then the coolant flows into a coolant pipe 2a constituting an upper heat exchanging core 1a and a coolant pipe 2b constituting a lower heat exchanging core 1b. During a condensing operation, in turn the coolant flows from a coolant pipe 2' and through a changing-over of the four-way valve 4, a circuit at the coolant pipe 2d is closed. The coolant passes through a branch pipe 3b and flows into the coolant pipe 2a constituting an upper heat exchanging core 1a. The coolant flows into the coolant pipe 2b constituting the lower heat exchanging core 1b through the branch pipe 3a. The coolant heat exchanges with air and the coolant is condensed, thereafter the coolant is flowed out of the coolant pipe 2''. A pressure loss of the coolant in the pipe is higher than that of the evaporating operation and the most appropriate number of passes is larger at the condensing operation than that at the evaporating operation. For example, the coolant circuit is changed over to two passes during an evaporating operation and in turn the coolant circuit changes over to one pass during a condensing operation so as to get a high capability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat exchanger used in a heat pump air conditioner for both cooling and heating, which exchanges heat between air and a refrigerant. It also serves as a condenser.

BACKGROUND OF THE INVENTION In recent years, heat exchangers for heat pump air conditioners have been required to be more compact in terms of equipment design.
The recent trend is to increase the number of buses in refrigerant circuits as the diameter of refrigerant pipes decreases, as shown in Japanese Utility Model Application No. 04952 and Japanese Utility Model Application No. 63-104956.

Hereinafter, a conventional heat exchanger for a heat pump air conditioner as described above will be explained with reference to the drawings.

FIG. 4 shows a refrigerant circuit of a conventional heat exchanger for a heat pump air conditioner. In FIG. 4, numeral 5 denotes a heat exchange core for exchanging heat between air and refrigerant, which is composed of refrigerant pipes 6 and has two circuits of refrigerant pipes 6a and 6b. 7 is a branch pipe,
Early refrigerant pipes 6a and 6bt-collected, refrigerant pipes 6 on the inflow and outflow side
' and 6°'.

The operation of the heat exchanger for a heat pump air conditioner configured as described above will be explained below using FIG. 5.

First, during evaporation operation, refrigerant flows in from the refrigerant pipe 6'', and the refrigerant is divided into two buses by the branch pipe 7a, and the refrigerant is used to form the upper heat exchange core 5a and the lower heat exchange core 5b, respectively. It flows into tube 6b.

Further, the refrigerant exchanges heat with air in the heat exchange cores 5a and 5b and evaporates, then joins again in the branch pipe 7b and flows out through the refrigerant pipe 6'. During condensing operation, the refrigerant flows in from the refrigerant pipe 6', and the refrigerant is divided into two buses at the branch pipe 7b, as in the case of evaporation operation. The refrigerant flows into the refrigerant pipe 6b that constitutes the exchange core 5b.

Further, the refrigerant exchanges heat with air in the heat exchange cores 5a and 5b, condenses, joins again in the branch pipe 7a, and flows out through the refrigerant pipe 6°.

At this time, as the number of passes in the refrigerant circuit decreases, the flow rate of the refrigerant increases, which improves the heat transfer coefficient inside the tube, but at the same time, the pressure loss inside the tube also increases, so there is an optimal number of passes to obtain the maximum capacity as a cycle. In addition, this optimal number of passes exists during evaporation operation and condensing operation, but the pressure loss inside the refrigerant tube is usually larger during evaporation operation than during condensation operation, and an increase in the inside pressure loss causes a decrease in capacity. Since the influence is also greater during evaporation operation, the optimal number of passes is larger during evaporation operation than during condensation operation.

Problem to be Solved by the Invention However, in the above configuration, the number of paths in the refrigerant circuit during evaporation operation and condensation operation is the same, so the optimal number of paths is configured for both evaporation operation and condensation operation. The problem was that the heat exchanger for heat pump air conditioners was not fully utilized.

In view of the above problems, the present invention makes the number of passes in the refrigerant circuit during condensing operation smaller than the number of passes in the refrigerant circuit during evaporative operation, and maintains the optimum number of passes during both evaporative operation and condensing operation, thereby providing a heat pump air conditioner. This maximizes the ability of the heat exchanger.

Means for Solving the Problems In order to solve the above problems, the heat exchanger for a heat pump air conditioner of the present invention includes a heat exchange core made up of a plurality of refrigerant pipes, a branch pipe that constitutes a refrigerant circuit together with the refrigerant pipes, and It is composed of a four-way valve, and has a configuration in which the number of passes in the refrigerant circuit during condensing operation is made smaller than the number of passes in the refrigerant circuit during evaporation operation by switching the four-way valve.

Effect: With the above-described configuration, the present invention makes the number of passes in the refrigerant circuit during condensing operation smaller than the number of passes in the refrigerant circuit during evaporating operation by switching the four-way valve, and maintains the optimal number of passes during both evaporating and condensing operations. This allows you to make the most of the heat exchanger's capabilities for heat pump air conditioners.

EXAMPLE Hereinafter, a heat exchanger for a heat pump air conditioner according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a refrigerant circuit of a heat exchanger for a heat pump air conditioner according to an embodiment of the present invention, FIG. 2 shows a refrigerant flow during evaporation operation, and FIG. 3 shows a refrigerant flow during condensation operation.

1 to 3, reference numeral 1 denotes a heat exchange core for exchanging heat between air and refrigerant, which is composed of refrigerant pipes 2 and has two circuits, refrigerant pipes 2& and 2b. 3 is a branch pipe, 4 is a four-way valve, and the combination of the branch pipe 3 and the four-way valve 4 collects the refrigerant pipes 2a and 2b, and connects the refrigerant pipes 6' and 6 on the inflow and outflow sides.
Connected to °°.

The operation of the heat exchanger for a heat pump air conditioner configured as described above will be described below with reference to FIGS. 2 and 3.

First, during evaporation operation, refrigerant flows in from the refrigerant pipe 2'', and is divided into two paths by the four-way valve 4 through the refrigerant pipe 2C and the branch pipe 3a. The refrigerant flows into the refrigerant pipes 2b that constitute the heat exchange core 1b. Furthermore, after the refrigerant exchanges heat with air in the heat exchange cores 1a and 1b and evaporates, the refrigerant on the refrigerant pipe 2a side flows into the branch pipe 3b.
The refrigerant on the refrigerant pipe 2b side flows from the four-way valve 4 into the branch pipe 3b via the refrigerant pipe 2d. Further, the refrigerant flows out from the refrigerant pipe 2' after merging at the branch pipe 3b.

Also, during condensing operation, refrigerant flows from the refrigerant pipe 2' and reaches the branch pipe 3b.
Since the circuit on the side of the refrigerant pipe 2d flowing into the refrigerant pipe 2d is closed, the refrigerant flows only into the refrigerant pipe 2a forming the upper heat exchange core 1a via the branch pipe 3b. Here, the refrigerant exchanges heat with the air and condenses, then flows into the branch pipe 8a, but since the refrigerant pipe 2C is also closed by switching the four-way valve 4, the refrigerant is combined with the refrigerant constituting the lower heat exchange core 1b. It flows into tube 2b. Here, the refrigerant exchanges heat with the air and is further condensed, after which it flows out through the four-way valve 4 into the refrigerant pipe 2'.

At this time, as the number of passes in the refrigerant circuit decreases, the flow rate of the refrigerant increases, which improves the heat transfer coefficient inside the tubes, but at the same time, the pressure loss inside the tubes also increases, so there is an optimal number of passes to obtain the maximum capacity as a cycle. In addition, this optimal number of buses exists during evaporation operation and condensing operation, but the pressure loss inside the refrigerant tube is usually larger during evaporation operation than during condensing operation, and an increase in the inside pressure loss causes a decrease in capacity. Since the influence is also greater during evaporative operation, the optimal number of buses is larger during evaporative operation than during condensing operation.

Corresponding to this, the refrigerant circuit of the heat exchanger for a heat pump air conditioner shown in the example can be switched to 2 buses during evaporative operation and 1 bus during condensing operation. Higher capacity than air conditioner heat exchangers can be obtained.

As described above, according to this embodiment, the heat exchange core 1 is composed of a plurality of refrigerant pipes 2, the branch pipes 3 and the four-way valve 4, which together with the refrigerant pipes 2 constitute a refrigerant circuit, the four-way valve 4 By switching between 2 buses during evaporation operation and 1 bus during condensing operation, the number of passes in the refrigerant circuit during condensing operation is smaller than the number of passes in the refrigerant circuit during evaporation operation. By setting an almost optimal number of passes both during operation and condensing operation, it is possible to obtain higher heat exchange capacity than conventional heat exchangers for heat pump air conditioners.

In this example, 2 buses are used during evaporation operation and 1 bus is used during condensation operation.
However, depending on the size of the heat exchanger, the number of passes may need to be increased, so by using multiple similar refrigerant circuits, it can be set to 6 passes during evaporative operation and 3 buses during condensing operation. It is also possible to easily apply this method.

Effects of the Invention As described above, the present invention consists of a heat exchange core composed of a plurality of refrigerant pipes, a branch pipe and a four-way valve that together with the refrigerant pipes constitute a refrigerant circuit, and the four-way valve can be switched during evaporation operation. By making the number of passes in the refrigerant circuit during condensing operation smaller than the number of passes in the refrigerant circuit in Heat exchange ability can be obtained.

[Brief explanation of drawings]

Fig. 1 is a refrigerant circuit diagram showing the shape of a heat exchanger for a heat pump air conditioner in an embodiment of the present invention, Fig. 2 is a refrigerant circuit diagram showing the refrigerant flow during evaporation operation in Fig.
Figure 4 is a refrigerant circuit diagram showing the refrigerant flow during condensing operation, Figure 4 is a refrigerant circuit diagram showing the shape of a conventional heat exchanger for a heat pump air conditioner, and Figure 5 is during evaporation operation and condensing operation as shown in Figure 4. It is a refrigerant circuit diagram showing refrigerant flow. 1... Heat exchange core, 2... Refrigerant pipe, 3... Branch pipe, 4... Four-way valve.

Claims (1)

[Claims] Consisting of a heat exchange core composed of a plurality of refrigerant pipes, and a branch pipe and a four-way valve that constitute a refrigerant circuit together with the refrigerant pipes,
A heat exchanger for a heat pump air conditioner, characterized in that the number of passes in the refrigerant circuit during condensing operation is smaller than the number of passes in the refrigerant circuit during evaporation operation by switching a four-way valve.