JPS58182091A - Corrugated fin type evaporator - Google Patents

Abstract

PURPOSE:To obtain a corrugated fin type evaporator, which is highly resisting to freezing and has large cooling capacity, by a structure wherein the joining lines between fins and flattened tubes are inclined with a rising gradient from the horizontal plane along the direction of air flow so as to lead the condensate to the air inlet side, at which the air temperature is higher than that at the air outlet side. CONSTITUTION:The flattened tube 1, in which heat transfer medium flows and at both ends of which headers 2 and 3 are jointed, is formed in zigzag and fins 4 folded in zigzag are jointed by brazing or the like between the parallel parts of the tube 1. Each fin 4 has ridgelines 6 and also has a large number of louver 7 at its fin part. Said ridgeline 6 is inclined with a rising gradient along the direction of air flow 5 and the air temperature becomes gradually lower toward the direction of air flow 5. A large part of the condensate adhered to the fin surface is led toward the air inlet side. Because the relation between the speed of air flow (u)m/sec and the critical acclivity angle thetamm. (degree), at which the condensate can return to the air inlet side, is thetamm.=arc sin(0.05Xu), the angle of inclination of acclivity theta, which is larger than the critical acclivity angle thetamm., is employed so as to lead the condensate to the air inlet side, at which the air temperature is higher than that at the air outlet side, in order to make the amount of the condensate at the air outlet side, at which the freezing is apt to occur, as small as possible, resulting in obtaining an evaporator, which is highly resisting to freezing.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a corrugated fin type evaporator in which the fins have a large number of inclined louvers in the fin direction and are all bent in a zigzag shape and the ridge line is joined to the side surface of a flat tube. The present invention relates to a corrugated fin type evaporator suitable for use in air conditioners and room air conditioners.

Conventional evaporators of this type have a flat tube and a zigzag-shaped fin that is tilted downward in the air flow, taking into consideration whether the joint #i with the flat tube is horizontal or draining. It is true that when the fin is tilted downward like this, the condensed water crosses the entire joint line, and a large amount of condensed water is discharged from the front end of the fin, that is, the windward side area, and from the rear end of the fin, that is, the leeward side.

However, the temperature of the air flowing between the fins gradually decreases in the direction of flow, and is the lowest at the air outlet end, so if the refrigerant temperature is low and freezing is unlikely to occur,
A large amount of condensed water at the air outlet end freezes, making the heat exchanger extremely susceptible to freezing. Conventional corrugated fin heat exchangers have the disadvantage that they freeze more easily than other types of evaporators, such as cross-fin evaporators.

An object of the present invention is to provide a corrugated fin type evaporator that is resistant to freezing by guiding condensed water generated during the process of cooling the air to the high temperature air inlet side.

In the corrugated fin type evaporator of the present invention, in order to guide the condensed water to the whole air population side, the fins are arranged so that the joining line between the corrugated fin and the flat conductor slopes upward from the horizontal direction to follow the air flow. The characteristic is that the force of the condensed water overcomes the frictional force caused by the viscosity of the air.

An embodiment of the evaporator of the present invention will be explained below with reference to FIGS. 1 to 3.

A flat tube 1 through which a heat medium flows is formed in a meandering shape, and headers 2.3 are connected to both ends thereof.

A zigzag-shaped fin 4 is joined between the parallel portions of the flat tube 1 by brazing or the like. 5 shows the air flow.

The fin 4 bent in a zigzag shape has a ridgeline 6 (flat tube 1
and fin 4), and there are many roots (Δ7) in the fin part.

As shown in FIG. 3, this ridgeline 6 is sloped upward from the horizontal in the direction 5 of the air flow, and in this embodiment, it is sloped upward by 110 degrees from the horizontal. There is. As shown in FIG. 4, the temperature change of the air at this time occurs in the direction of air flow and gradually decreases. When the distribution of condensed water adhering to the fin surface was experimentally measured, it was as shown in FIG. 5, and most of the condensed water was guided toward the air inlet side. The wind speed at this time was approximately 2.5 m/s. It has been experimentally confirmed that the following relational expression holds between the air flow velocity kl (m/sec) and the critical upward slope angle θ (degrees) for condensed water to return to the air inlet side. . That is, the inclination angle of the fin wall surface is set to 0. Projected area of condensed water A, + liquid film thickness! 1. When the density of water is ρ7, the force Ff pulled by shudder and the force FW pulled back by gravity are Ff - τOA.

FW=ρ7・θ, A・yφ5111v.

becomes.

However, τG is the shear stress on the wall surface, and the fin pitch is 2 f
, the viscosity coefficient of air is tμ, and the wind speed is 1u, then To is ±.

From the above formula, p Ff = FW, the maximum wind speed of car coolers, etc. is generally u = 2.577
Z/S, and the critical inclination angle θ when u −2.5 m/s is 7.2 degrees from the above calculation formula, and if it is not more than this, the condensed water will scatter backwards.

Therefore, the following relational expression holds between the wind speed U and the limit inclination angle OM.

°(4) Ow = arCsin (0,05X u )
--- (1) In this way, the slope angle of the uphill slope V〉θ
-'Th condensed water by adding? By guiding the air to the high-temperature air inlet side, the amount of condensed water at the air outlet end, where freezing occurs, is reduced, making it possible to obtain an evaporator that is resistant to freezing.

Figure 6 shows the limit value of the thermostat attached to the fin to prevent freezing. This is what is shown. The horizontal axis is the OFF value of the thermostat, and the i-axis is the DIFF value of the thermostat, where region A is a frozen region and region B is a non-frozen region.

The limit value of corrugated fins in conventional evaporators, where the ridgeline of the fins bent in a zigzag shape (junction with the flat tube) is inclined downward in the horizontal case or in the direction of air flow, is line a. n, and the limit value of the corrugated fin in the evaporator of the present invention is shown by the line.With the present invention, the limit value is lower and the thermostat can be set at a lower temperature than ever before. It became possible to obtain low-temperature air.As a result, the cooling capacity was significantly improved.

When the fin ridgeline (joint H) is arranged on an upward slope, if a normal louver fin is used, air will blow out upward along the fin ridgeline (joint line). Is the fin ridgeline (joint line) of the entire evaporator metal part? When tilting the evaporator, if the entire evaporator cannot be tilted completely vertically, there will be areas at the top and bottom corners of the evaporator where air will stagnate. As a solution to this problem, it is preferable to create a certain relationship between the fin inclination angle θ and the louver inclination angle γ. Next, the relationship between the slope angle θ around the fin 1, the slope 0 around the root (-1), and the louver slope angle is made to completely satisfy the following relationship.

1 2sirBI sin 2γ−2C1+δ*) (b −7J “””
(2) Here, t Niru-par plate thickness (m) 7) * Removal thickness of rear end of Niru bar 1.72B; (copying) b
Nir-bar length (m) Reb Reynolds number of nil-bar 31-l Nir-par spacing (m) U: Air flow velocity (m/sec) C: Kinematic viscosity coefficient of air (T'/5ec) Fin Inclination angle V
When and the louver inclination angle γ satisfy the relationship of equation (2),
Regardless of the fin inclination angle θ, the air flows straight forward without changing the air inflow direction.

In this way, in an evaporator in which condensed water adheres to the fins, it is necessary to drain all of the condensed water on the air inlet side to prevent freezing. Therefore, the above equation (1) and equation (2
), an optimal fin structure can be obtained.

FIGS. 8 and 9 are diagrams showing the characteristics of the fin structure with these two restrictions added. In Figures 8 and 9, horizontal 1
lII is the fin inclination angle (θ0), and the vertical axis is the louver inclination angle (γ0). If O is negative, there is a downward slope with respect to the inlet air flow, and if γ is negative, it is sloped upward. Further, area A11-1 indicates an area to be frozen, and area B indicates an area to be frozen.

qt -0,15th, 1) -2,3m, l=2.3
mm.

u -2.5m/s, sea 1.38 x 10-
'm''/s, Reb -417, δ*=
0.194mm Equations (1) and (2) can be transformed as follows.

= 0.308 (1-2 sin θ)−・・・・・−−
(8) θ ≧7.18° ・・・・・・・
・・・・・・・・・・・・(4) Figure 8 shows the above equation (8
), The relationship in (4) is shown by gold lines c and d. For heat exchanger fins to which condensed water does not adhere, the condition of equation (3) alone is sufficient, but for evaporator fins to which condensed water adheres, the condition of equation (4) in addition to equation (3) is sufficient. In addition, the range of application of the fin inclination angle θ and the louver inclination angle γ becomes narrower in the thick line portion on line C.

Moreover, FIG. 9 shows that under the above conditions, the wind speed u2u=2.
This is a case where the speed is changed from 5 m/s to 1.0771/S.

L to replace u=2 Rebil: Reb= 167
, δ1 becomes δ”-0,3061 nM. In this case, equations (1) and (2) become as follows.

5in2γ-0,405(1-2sinθ)・・・・・・
・・・・・・・・・・・・・・・・・・(5) θ ≧2.8
7° ・・・・・・・・・・・・・・・・・・・・・
・・・・・・・・・・・・・・・・・・(6) Formula in the figure (5
) and (6) are shown by lines e and f.

・(8)・ As explained above, according to the present invention, the joining line between the fin and the flat tube is oriented in the direction of air flow and is inclined upwardly from the horizontal plane, so that condensed water flows toward the air inlet side. A corrugated fin-shaped evaporator that is resistant to corrugated and freezing can be provided. As a result, the set value of the anti-freeze thermostat can be lowered, resulting in a greater cooling capacity than in the past.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an example of the corrugated fin type evaporator of the present invention, FIG. 2 is a perspective view of the corrugated fin in FIG. 1, and FIG. 3 is a diagram showing an example of the ridgeline of the corrugated fin in FIG. 1. Figure 4 shows changes in air flow direction and air temperature? Figure 5 is a diagram showing the distribution of condensed water on the fins of the evaporator of the present invention, Figure 6 is a diagram showing the limit value of the thermostat for anti-freezing, and Figure 7 is a diagram showing the distribution of condensed water on the fins of the evaporator of the present invention. The diagrams illustrating the relationship between the fin inclination angle and the inclination louver inclination angle, FIGS. 8 and 9, are diagrams completely explaining the relationship between the fin inclination angle and the inclination louver inclination angle. 1... flat tube, 4... fin, tail... air flow, 6
...Ridge line, 7...Slanted louver.・ Drunkenness ・ Sai 1 country 23 maps Oto country 5th country Omniner'f-X77) OFF I direct ('C) 17 (2
) ya δ eye fille god now beef θ Q lol no

Claims (1)

[Scope of Claims] 1. In a corrugated fin type evaporator in which a fin having a large number of inclined louvers on the fin surface is bent in a zigzag shape and its ridgeline is joined to the side surface of a flat tube, the fins and the flat tube are connected to each other. A corrugated fin type evaporator, characterized in that it is inclined upwardly so that the angle θ between the joining line and the horizontal plane along the air flow direction satisfies the following relationship. θ≧arc Sin (0.05 A corrugated fin type evaporator according to claim 1. 5in2γ-2(1+δ*)(-!1--2sinθ)
bI! θ≧arc sin (0,05X u) but l
Plate thickness of nil bar (m) u (n δ exclusion thickness at rear end of cell par min 1.72 Note b length of nil bar m) -b 1 (eb Reynolds number of nil bar 3 □ν L-bar spacing <m) U: Air flow velocity (m/sec) C: Kinematic viscosity coefficient of air (tt?/5ec)