JPS62245090A - Heat exchanger with fins - Google Patents

Abstract

PURPOSE:To extend an operating time when frost is adhered by a method wherein a group of thermal conducting pipes is made independent for each of rows with respect to an air flow direction, a pipe pitch in each of rows is decreased in sequence from an air inlet side to an air outlet side, and a diameter of thermal conducting pipe in each of the rows is gradually increased from the air inlet side to the air outlet side. CONSTITUTION:A heat exchanger is comprised of a group of thermal conducting pipes 7a, 7b, 7c and 7d arranged in a grid pattern in parallel with an air flow direction 6 and a group of fins 8, and a pipe diameter of each of the group of thermal conducting pipes 7a, 7b, 7c and 7d is Da, Db, Dc and Dd, resulting in that the pipe diameters Da, Db, Dc and Dd are set at a relation of Da<Db<Dc<Dd and a pitch of each of the pipe pitches in the row S1, S2 and S3 is set to have a relation of S1<S2<S3. Therefore, fin temperatures t10, t11, t12 are set to have a relation of t10<t11<t12. Due to this fact, an absolute humidity difference between flowing air influencing a frost forming shape and a saturated wet air corresponding to a thermal conducting temperature of the heat exchanger is made uniform over an air flowing direction to form a uniform frost layer 13. Therefore, a thicker frost layer is not locally present at the air inlet thermal conducting surface, resulting in that the long air passage is assured and then an operating time can be remarkably extended.

Description

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

2. Description of the Related Art As shown in FIGS. 3 and 4, a conventional outdoor heat exchanger consists of a group of heat transfer tubes 1 of the same diameter that are installed horizontally and through which refrigerant flows, and a group of heat transfer tubes 1 that are installed vertically to the group of heat transfer tubes 1. It consisted of a group of fins 3 inserted at regular intervals through which air flows in the two directions of the arrows. Note that 4 is a fin collar.

Problems to be Solved by the Invention Generally, in heating operation of a heat pump type air conditioner using air as a heat source, the outdoor heat exchanger functions as an evaporator, and when the ambient air temperature decreases, the evaporation temperature drops below o'C and the air The water vapor inside adheres as frost and forms a frost layer. and,
Defrosting is necessary because the amount of heat exchange is significantly reduced due to the reduction in the amount of air passing through the frost layer and the insulation effect.

A frost layer 6 is likely to form on the air inflow side heat transfer surface, where the absolute humidity difference between the inflow air and the saturated humid air corresponding to the heat exchanger heat transfer surface temperature is greatest, and almost no frost layer is formed on the air outflow side heat transfer surface. Layer 6 is not formed. If operation continues under frost conditions, 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, there is a drawback that the time until the space between the fin groups 3 is blocked by the frost layer and the function as an evaporator is no longer fulfilled is extremely short. Was. 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 finned heat exchanger that can extend the operating time during frosting.

Means for Solving the Problems Therefore, the finned heat exchanger of the present invention has a heat exchanger tube group through which a refrigerant flows and a fin group inserted into the heat exchanger tube group and through which air flows. were made independent for each row in the air flow direction, the tube pitch of each row was made smaller sequentially from the air inlet side to the air outlet side, and the heat transfer tube diameter of each row was made sequentially larger from the air inlet side to the air outlet side. It is something.

action 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 y0.2. 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 is greatest at the air inflow side heat transfer surface where the enthalpy difference between the inflow air and saturated humid air corresponding to the heat exchanger heat transfer surface temperature is largest. 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. Also, since the diameter of each row of heat transfer tubes increases from the air inflow side to the outflow side, the circulation amount of each row is reduced by the air inflow side due to the resistance of the heat transfer tubes.
The number of heat transfer tubes in the first row is the least, and as a result, the refrigerant in the heat transfer tubes in the first row evaporates in a short time and becomes gas. After that, the refrigerant exchanges sensible heat, so the temperature of the refrigerant (gas) gradually rises.Therefore, in the gas region, the temperature of the heat transfer tubes in each row increases sequentially from the air inflow side to the air outflow side. Further, the tube pitch in each row is gradually smaller from the air inflow side to the outflow side, and as described above, the diameter of each row of heat transfer tubes is smaller on the air inflow side, so the fin temperature between the heat transfer tubes is higher on the air inflow side than on the air outflow side. Therefore, 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, which greatly influences the shape of the frost layer, is made uniform over the air flow direction, and a uniform frost layer is formed.

Therefore, the time until the space between the heat transfer surfaces is blocked by a layer of frost and the evaporator no longer functions as an evaporator can be significantly extended.

EXAMPLE An example of the present invention will be described below with reference to FIGS. 1 and 2. As shown in the figure, heat exchanger tube groups 7&, 7b, 70.7 are arranged in a grid pattern parallel to the airflow direction 6.
+1 and fin group 8. Heat exchanger tube group 71&, 7
The pipe diameters of b, To, and Ten are DiL+ Dtz, respectively.
”If O+Dd, the pipe diameter is n&, Db,
Da r Dd is Da < Db < DC < D (1. Also, the pitch of each row of tubes in the heat exchanger tube group S1 * Sl * S
3 is Sl>82>Ss. 9 is a fin collar.

1 Next, I will explain the current situation.

I., j, The air flowing into the heat exchanger of this embodiment exchanges heat with the refrigerant flowing in the heat exchanger tubes of each row. The heat flux q is greatest at the air inflow side heat transfer surface where the enthalpy difference between the inflow air and saturated humid air corresponding to the heat exchanger heat transfer surface temperature is largest. Therefore, in the air inlet side heat exchanger tube, that is, the heat exchanger tube 71L, the refrigerant actively exchanges heat with the incoming air and evaporates. Furthermore, the diameter of each row of heat transfer tubes is 1) a<Db
Since <Da<Dd, the amount of circulation of each row of heat exchanger tubes is the smallest in the heat exchanger tube 71L due to the resistance of the heat exchanger tubes. As a result, the refrigerant in the heat exchanger tube 7a 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. Each row heat exchanger tube group 71L, 7
m), the temperature inside the tube at 70 and 7d, respectively, is ia + ? b
+ ta s td, the temperature inside each heat transfer tube group in the gas region is tIL * tb * tO *
At t6, ta > tl) > tc > t4.

Furthermore, the tube pitch in each row is Sl>Sl>Ss and the diameter of the heat transfer tubes in each row is Da<Db<Dc<1) (l), so the fin temperature t10 w between the heat transfer tubes 10, 11.12
tll + tl2 is too > t++ > t, 2
becomes. Therefore, 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, which greatly affects the shape of the frost layer, is equalized in the air flow direction, and a uniform frost layer 13 is formed. . Therefore, a ventilation path is maintained for a long time without unevenly distributing a frost layer on the heat transfer surface on the air inflow side, and the operating time can be significantly extended.

Furthermore, even during defrosting, the heat exchange rate improves because the heat for melting the frost is effectively used anywhere on the heat transfer surface and is not used to warm the surrounding air.

Furthermore, when used as a condenser, since the diameter of the front heat exchanger tubes is small, the rear heat exchanger tubes do not completely enter the dead area of the front heat exchanger tubes, increasing the effective heat transfer area and improving heat transfer performance.

Although the case where the tube arrangement is parallel to the airflow has been described as an embodiment of the present invention, it goes without saying that the same effect can be obtained even if the tube arrangement is inclined with respect to the airflow.

Effects of the Invention As described above, the finned heat exchanger of the present invention can realize a frost layer with a uniform shape even under conditions where frost formation occurs, so the operating time until the heat transfer surfaces become clogged can be significantly extended. It is possible.

[Brief explanation of drawings]

FIGS. 1a and 1b are front and side views of a finned heat exchanger according to one embodiment of the present invention, and FIGS. 2a and 2b are side sectional views of a finned heat exchanger according to another embodiment of the present invention. and plan sectional views, FIGS. 3 and 4a. b is an overall perspective view, a side sectional view, and a plan sectional view of a conventional finned heat exchanger. 7&, 7b, To, 7 (1... Heat exchanger tube group, 8.
·····fin. Name of agent: Patent attorney Toshio Nakao and one other person
7b, 7c, 7tL - bald canal group Fig. 1
8-Fin (Yu 2 δ Fig. 2 7tt, 7b, 7C, 7t-Ijin 8) ---Fin Fig. 3 Fig. 4

Claims (1)

[Claims] It has a heat exchanger tube group through which a refrigerant flows, and a fin group inserted into the heat exchanger tube group through which air flows, and the heat exchanger tube group is made independent in each row in the air flow direction, and each row is A heat exchanger with fins in which the tube pitch is gradually decreased from the air inlet side to the air outlet side, and the heat transfer tube diameter of each row is gradually increased from the air inlet side to the air outlet side.