JPS62142990A - heat exchange equipment - Google Patents

Abstract

PURPOSE:To make it possible to prolong the operational time at the time of frosting of a heat exchanger by independently providing heat transfer pipe groups in an air flow direction, making successively larger the diameters of heat transfer pipe groups from air inlet side to the outlet side, and making successively larger the coolant weight speed within heat transfer pipes from the air inlet side to the outlet side. CONSTITUTION:An evaporator 10 is constituted of heat transfer pipe groups 13a, 13b, 13c and 13d arranged on a checkerboard shape in parallel to an air current direc tion 12 and a fin group 14. The dimensions of the pipes of the heat transfer pipe group are set to Da<Db<Dc<Dd. Since a liquid coolant of a high temperature and a high pressure which has left a condenser 7 is controlled so that a coolant weight speed is successively made larger from the air inlet side to the air outlet side by a flow quantity adjustor 8, the coolant within the heat transfer pipe 13a is evaporated in a short period of time. On the front surface at the air inlet side of an evaporator 10, the growth of a frosted layer becomes slow, a vent path is secured for a long period of time, and fresh air flows into the evaporator and is subjected to heat exchange. A similar phenomenon occurs in heat transfer pipes 13b, 13c and 13d, and a time until the frosted layer blocks spaces formed by fin groups 14 becomes clogged is remarkably prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a heat exchange device used in air conditioners, refrigerators, and the like.

Conventional technology During heating operation of a heat pump type air conditioner using air as a heat source, the air-to-air heat exchanger functions as an evaporator, and when the ambient air temperature drops, the evaporation temperature drops below 0"C and the water vapor in the air turns into frost. Defrosting is necessary because this frost layer reduces the amount of air passing through and acts as an insulator, resulting in a significant decrease in the amount of heat exchange.

As shown in Figures 3 and 4, a conventional outdoor heat exchanger consists of a group of heat transfer tubes 1 of the same diameter, which are installed horizontally and through which refrigerant flows.
A fin group 3 was also constructed which was inserted into the heat transfer tube group 1 at regular intervals in the vertical direction and through which air flowed in the two directions of the arrows. 4 is a fin collar.

Problems to be Solved by the Invention In general, the absolute humidity difference between the incoming air and the saturated humid air corresponding to the temperature of the heat transfer surface of the heat exchanger is the greatest, and the frost layer 6 is likely to be formed on the air inflow side heat transfer surface, and the air outflow Almost no frost layer 6 is formed on the side heat transfer surface. If operation continues under frost conditions during frost formation, the passing air volume will decrease with frost formation, and the bypass factor will become smaller.Moreover, the evaporation temperature will decrease and the frost layer surface temperature will not rise, so the frost layer 6 will increase the heat transfer on the air inlet side. It begins to grow only on the surface.

As mentioned above, since the frost layer distribution on the heat transfer surface of the heat exchanger is unevenly distributed, the disadvantage is that the time until the space between the fin groups 3 is blocked by the frost layer and the evaporator no longer functions is extremely short. had. Furthermore, since the frost layer distribution is unevenly distributed, a considerable portion of the heat for melting the frost during defrosting is used only to warm the surrounding air, resulting in a drawback of extremely poor thermal efficiency.

The present invention solves the above-mentioned drawbacks of the prior art and provides a heat exchange device that can extend the operating time during frosting.

Means for Solving the Problems The heat exchange device of the present invention has a group of heat transfer tubes through which a refrigerant flows, and a group of fins inserted into the group of heat transfer tubes and between which air flows. is independent for each row in the air flow direction, the diameter of the heat transfer tubes in each row is increased sequentially from the air inflow side to the air outflow side, and the refrigerant weight velocity in the heat transfer tubes in each row (unit cross-sectional area of heat transfer tube It is equipped with a flow rate regulator that sequentially increases the air velocity (weight velocity per unit) from the air inflow side to the air outflow side.

For production The effect of this technical means is as follows.

Generally, in heat pump air conditioners, the refrigerant has a dryness x
It flows into the evaporator in a state of about +0.2. The air flows through independent heat transfer tubes in each row, exchanges heat with the air flowing between the fin groups, and evaporates.

The heat flux q has the largest enthalpy difference between the incoming air and the saturated humid air corresponding to the temperature of the heat transfer surface of the heat exchanger, and is largest at the air inflow side heat transfer surface. Further, the in-pipe evaporative heat transfer coefficient αR is generally a function of the heat flux q, and is expressed as αR·qm. Therefore, in the first row of heat transfer tubes on the air inflow side, the refrigerant actively exchanges heat with the incoming air and evaporates.

In addition, since the flow rate regulator controls the refrigerant weight velocity in each row of heat transfer tubes to increase sequentially from the air inflow side to the air outflow side, the refrigerant in the first row of heat transfer tubes evaporates in a short time and becomes gas. . After that, the refrigerant undergoes sensible heat exchange, so the temperature of the refrigerant (gas) gradually increases. Since the temperature of the refrigerant approaches that of the incoming air, a frost layer is less likely to form on the air inflow side heat transfer surface, and fresh air exchanges heat with the air outflow side heat transfer surface. A similar phenomenon occurs in the second column.
This also occurs in the third row, thus resulting in the formation of a uniform layer of frost over the entire heat exchanger heat transfer surface.

Therefore, the time until the space between the heat transfer surfaces becomes clogged with a layer of frost and the device no longer functions as an evaporator can be significantly extended.

Example Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a refrigerant circuit diagram, and FIG. 2 is a detailed view of the fins.

The heat pump type air conditioner shown in Fig. 1 has a compressor 6, a condenser 7.
It is constructed by connecting a flow rate regulator 8, a throttle 9, an evaporator 10, etc. attached to each pipe branched into four paths in an annular shape. Further, the pipes branched into four paths are each independent up to the outlet of the evaporator 1o, and are provided with a sensor 11 for detecting the refrigerant weight velocity. In response to this signal, the flow rate controller 11' outputs a signal to the flow rate regulator 8 so that the refrigerant weight velocity becomes a predetermined value. As shown in FIG. 2, the evaporator 10 includes a group of heat transfer tubes 13a, 13b, 13c, and 13d and a group of fins 14, which are arranged in a grid pattern parallel to the airflow direction 12. Pipe diameters Da, D1. of the heat exchanger tube group. D.C., D.
Da chestnut, chestnut. It is Dd. 15.16 in Figure 1
are fans for the condenser 7 and evaporator 1°, respectively, and 17 is a fin collar.

Next, the effect will be explained.

When the operation is started, the high-temperature, high-pressure liquid refrigerant exiting the condenser 7 is branched and adjusted by the flow rate regulator 8 to a predetermined refrigerant weight velocity. The air is then depressurized by the throttle 9, flows into the evaporator 1o, flows through the heat transfer tubes of each row, exchanges heat with the air flowing between the fin groups 14, and evaporates. The heat flux q has an enthalpy difference between the incoming air and the saturated humid air corresponding to the temperature of the heat transfer surface of the heat exchanger, and is expressed as αR·qm. Therefore, in the air inlet side heat exchanger tube, that is, the heat exchanger tube 13a, the refrigerant actively exchanges heat with the incoming air and evaporates. Furthermore, the flow rate regulator 8
Since the refrigerant weight velocity (weight velocity per unit cross-sectional area of the tube) in each row of heat exchanger tubes is controlled to increase sequentially from the air inlet side to the air outlet side, the refrigerant in the heat exchanger tubes 13a evaporates in a short time. When it finishes, it turns into gas. Thereafter, the refrigerant undergoes sensible heat exchange, so the refrigerant temperature approaches the incoming air temperature. Then, the absolute humidity difference between the incoming air and the saturated humid air corresponding to the refrigerant temperature becomes small, and the frost layer does not develop much. That is, the growth of the frost layer is slowed down in most of the front surface of the air inflow side of the evaporator 1o, and a ventilation path is secured for a long time. The fresh air then flows into the evaporator 10 and exchanges heat. A similar phenomenon occurs in the heat exchanger tubes 13b and 13C213d, and in the gas region, the internal temperature of the heat exchanger tubes is distributed from the highest heat exchanger tube 13a to the lowest heat exchanger tube 13d. Therefore, the absolute humidity difference between the incoming air and the saturated humid air corresponding to the heat exchanger heat transfer surface temperature, which greatly affects the shape of the frost layer, is made uniform over the air flow direction, and a uniform frost layer 18 is formed. Therefore, the operating time until the space between the fin groups 14 is blocked by a layer of frost can be significantly extended.

Also, during defrosting, the heat for melting the frost is effectively used anywhere on the heat transfer surface and is not used to warm the surrounding air, improving thermal efficiency.

Furthermore, since the gap between the heat exchanger tubes in the air flow direction is large on the air inflow side, a large amount of water droplets generated by defrosting in the air inflow part do not stay and fall smoothly, and do not freeze when restarting operation. Also, when used as a condenser,
Since the diameter of the front heat transfer tubes is small, the rear heat transfer tubes do not completely enter the dead area of the front heat transfer tubes, increasing the effective heat transfer area and improving heat transfer performance.

Effects of the Invention As described above, the heat exchange device of the present invention can realize a uniformly shaped frost layer even under conditions where frost formation occurs, so the operating time until the heat transfer surfaces are closed can be significantly extended. can.

[Brief explanation of drawings]

FIG. 1 is a refrigerant circuit diagram of a heat pump air conditioner using a heat exchange device according to an embodiment of the present invention, and FIG. 2 is a plan view and a side view of a main part of a fin of a heat exchange device according to an embodiment of the present invention. figure,
FIG. 3 is a perspective view of a conventional heat exchanger, and FIG. 4 is a plan view and a side view of a main part of a fin of a conventional heat exchanger. 6... Compressor, 7... Condenser, 8...
...Flow rate regulator, 9...Aperture, 10...
...Evaporator, 11...Sensor, 11'...
...Flow rate controller, 13a, 13b, 13c. 13d...Heat transfer tube, 14...Fin group, 16.16...Fan, 17...Fin color. Name of agent: Patent attorney Toshio Nakao and 1 other person8-
Flow rate recitation/11-11 Yanbu f5. /6---Fuan Figure 1 l7---Hunn pler Figure 2 18-591 shi) Figure 3 Figure 4? (b) “=hi44-shishizuku〆ichi

Claims (1)

[Claims] It has a heat transfer tube group through which a refrigerant flows, and a fin group inserted into the heat transfer tube group and through which air flows, and the heat transfer tube group is made independent in each row in the air flow direction, and each row is A heat exchanger equipped with a flow rate regulator that sequentially increases the diameter of the heat transfer tubes from the air inflow side to the air outflow side, and sequentially increases the refrigerant weight velocity in the heat transfer tubes in each row from the air inflow side to the air outflow side.