HEAT EXCHANGER

Abstract

A heat exchanger has tubes arranged in parallel at regular distances so they extend in the same direction as the ventilation direction of heat exchange medium flowing through the tube. The heat exchange medium is introduced and distributed to the plural tubes via an inlet tank. A fin interposed between the tubes increases the contact surface area of air passing between the tubes. The heat exchange medium flowing through the tubes is collected and then discharged by an outlet tank. The dimensions of the cross-sectional area Stube of the tube and the sectional area Stank of the inlet tank or the outlet tank satisfy the following formula: 0.04 < sectional   area   of   tube   ( S tube ) sectional   area   of   tank   ( S tank ) < 0.06

Description

TECHNICAL FIELD

The present invention relates to a heat exchanger, more particularly, to a heat exchanger which improves shapes and sizes of a tube and a tank so as to increase a heat radiation performance.

BACKGROUND ART

FIG. 1 is a view showing a general cooling and heating system of a vehicle. In a vehicle engine 1, high temperature and high pressure gas is ignited and burned. Therefore, if leaving the vehicle engine 1 as it is, it will be overheated and a metallic material used in constructing the engine 1 is melted and thus a cylinder, a piston and the like may be damaged seriously. To prevent such damage, as shown in FIG. 1, a water jacket (not shown) in which cooling water is stored is formed around the cylinder of the vehicle engine 1 and the cooling water is circulated through a radiator 2 or a heater core 3 by a water pump 5 so as to cool the engine 1. The cooling water may be not passed through the heater core 3, but directly returned to the water jacket through a bypass circuit 6 according to the purpose of heating and cooling. At this time, a thermostat 4 is provided in a passage for the cooling water so as to function as a control device for preventing the overheating of the engine 1 by controlling an opening/closing degree of the passage on the basis of a temperature of the cooling water.

The radiator 2 is a kind of heat exchanger for radiating heat of the cooling water which is heated by heat of the engine 1 while being circulated in the engine 1. The radiator 2 is disposed in an engine room of the vehicle and provided with a cooling fan at a center portion thereof so as to cool a radiator core. Further, the heater core 3 is a part of an air conditioner of the vehicle and also functions as the kind of heat exchanger for supplying warm air to an inside of the vehicle using the high temperature cooling water which absorbs the heat generated from the engine 1 while being circulated in the engine 1. In the heater core 3, the high temperature cooling water which is heated by the heat of the engine 1 is passed through a fin and a tube of the heater core 3 so as to transfer the heat to air supplied from the outside, thereby providing the warm air to the inside of the vehicle.

In order to properly heat the inside of the vehicle, a heat exchange performance of the heater core should be increased. therefore, in order for the heat exchange to be generated more smoothly, many efforts have been made by varying dimensions and shapes of the tube and tank constructing the heat exchanger using a basic principle that a contact surface for the heat exchange should be increased so that the heat exchange is performed smoothly, thereby increasing the heat exchange performance. In addition, the heat exchanger is made of a material having a high heat conductivity which can rapidly transfer the heat between the heat exchange medium in the heat exchanger and an outer medium passing the outside of the heat exchanger, thereby increasing the heat exchange performance. The varying of the dimensions, shapes and materials of each part is to basically increase a heat exchange coefficient which is directly associated with the heat exchange performance. As described above, if the surface area of each part is increased, the heat exchange performance is also increased. However, since there is a limitation on a space for installing the heat exchanger, it is very difficult to largely increase the surface area in the limited volume. Furthermore, in case of increasing the contact surface area for the heat exchange as described above, particularly, in case of the tube in which the heat exchange medium is accommodated, a sectional area of a passage for the heat exchange medium becomes reduced. If the sectional area of the passage is reduced, a flow rate of the heat exchange medium is increased and a pressure thereof is dropped, and thus the heat exchange coefficient is increased. However, if the sectional area of the passage is reduced excessively, the pressure is also dropped excessively and thus the heat exchange coefficient is reduced. Therefore, it is difficult to optimize the heat exchange performance only by reducing the sectional area of the passage.

DISCLOSURE

Technical Problem

An object of the present invention is to provide a heat exchanger which deduces a relationship between the varying of dimensions relevant to fluid flowing in the header tank and heat exchange tube and the heat exchange performance according to the change of distributed fluid flowing and thus improves the dimensions and shapes of the tank and tube, thereby optimizing the heat exchange performance.

Technical Solution

In order to achieve the above objects, there is provided a heat exchanger comprising heat exchanger 100 comprising a plurality of tubes 20 which are arranged in parallel at regular distances to be parallel with a ventilation direction and through which a heat exchange medium is flowed; an inlet tank 11 in which the heat exchange medium is introduced and then distributed to the plurality of tubes 20; a fin 30 which is interposed between the tubes 13 so as to increase a contact surface with air passing between the tubes 20; and an outlet tank 12 in which the heat exchange medium flowed through the tubes 20 is collected and then discharged, wherein dimensions of the sectional area S_tube of the tube 20 and the sectional area S_tank of the inlet tank 11 or the outlet tank 12 satisfy a following formula:

$0.04<\frac{\mathrm{sectional}\mathrm{area}\mathrm{of}\mathrm{tube}\left(S_{\mathrm{tube}}\right)}{\mathrm{sectional}\mathrm{area}\mathrm{of}\mathrm{tank}\left(S_{\mathrm{tank}}\right)}<0.06$

Preferably, a volume V_tank of the inlet tank 11 or the outlet tank 12 and a total sectional area A_tube of the tubes 20 calculated by multiplying the sectional area of the tube 20 and the number of tubes 20 satisfy a following formula:

$150<\frac{\mathrm{volume}\mathrm{of}\mathrm{inlet}\mathrm{tank}\mathrm{or}\mathrm{outlet}\mathrm{tank}\left(V_{\mathrm{tank}}\right)}{\mathrm{total}\mathrm{sectional}\mathrm{area}\mathrm{of}\mathrm{tubes}\left(A_{\mathrm{tube}}\right)}<230$

ADVANTAGEOUS EFFECTS

According to a heat exchanger of the present invention, it is possible to deduce a relationship between the varying of dimensions relevant to fluid flowing in the header tank and heat exchange tube and the heat exchange performance according to the change of distributed fluid flowing and thus improves the dimensions and shapes of the tank and tube, thereby optimizing the heat exchange performance. Furthermore, it is possible to easily design the heat exchanger having the optimal heat exchange performance, thereby saving labor, cost, time and the like.

DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:

FIG. 1 is a view showing a general cooling and heating system of a vehicle.

FIG. 2 is a perspective view of a heat exchanger.

FIG. 3 is a cross-sectional view of a tank of the heat exchanger.

FIG. 4 is a cross-sectional view of a tube of the heat exchanger.

FIG. 5 is a view showing a length of the tank and an effective area in the heat exchanger.

FIG. 6 is a graph showing a heat exchange performance per effective area with respect to each factor.

[Detailed Description of Main Elements]
100: heat exchanger 10: tank
11: inlet tank      12: outlet tank
20: tube            30: fin

BEST MODE

Hereinafter, the embodiments of the present invention will be described in detail with reference to accompanying drawings.

FIG. 2 is a perspective view of a heat exchanger 100. A heat exchange medium is flown in the heat exchanger 100, and the heat exchanger 100 includes a plurality of tubes 20 which are arranged in parallel at regular distances to be parallel with a ventilation direction, and tanks 10 which are respectively coupled to both ends of the tubes 20. The tanks 10 are divided into an inlet tank 11 in which the heat exchange medium is introduced and then distributed to the plurality of tubes 20 and an outlet tank 12 in which the heat exchange medium moved through the tubes 20 is collected and then discharged. Fins 30 are provided between the tubes 20 so as to increase a contact surface area with air flowing between the tubes 20. As described above, the heat exchange medium is introduced through an inlet port of the inlet tank 11, collected in the outlet tank 12 through the tubes 20 and then discharged through an outlet port of the outlet tank 12. While the heat exchange medium is flowed through the tubes 20, heat exchange is occurred between the heat exchange medium received in the tubes 20 and the external air through the tubes 20 and the fins 30 interposed between the tubes 20. In other words, the heat exchange is occurred at the tubes 20 and fins 30s, particularly, at an area where the tubes 20 is contacted with the air. Thus, the shapes and dimensions of the heat exchanger 100 greatly exert an influence on the entire heat exchange performance.

As described in the conventional heat exchanger, although the optimal dimension and shape of each tank 10 and tube 20 are obtained, the heat exchange performance of the heat exchanger 100 which is formed by coupling of each tank 10 and tube 20 is not optimized. As described above, since the heat exchange medium is introduced into the tank 10 and then flowed through the tube 20, each dimension and shape of the tanks 10 and tubes 20 has the specific relationship.

Hereinafter, the heat exchange phenomenon occurred in the heat exchanger will be described briefly. First of all, the heat exchange is occurred by convection between the heat exchange medium in the tubes 20 and inner surfaces of the tubes 20, and the heat is transferred from the inner surfaces of the tubes 20 to outer surfaces of the tubes 20 and the fins 30. Finally, the heat exchange is occurred between the outer surfaces of the tubes 20 and the fins 30 and the external air by the convection. As described above, the heat exchange phenomenon occurred in the heat exchanger depends on the convective heat exchange, and a heat exchange amount also depends on the contact surface area and flow rate. In the aspect of the contact surface area, the larger the surface area of the tube 20 and fin 30 contacted with the external air becomes, the better. And in the aspect of the flow rate, the larger the flow rate of the heat exchange medium flowing into the tube 20 becomes, the better.

FIGS. 3 and 4 are views showing each factor having an influence on the heat exchange, wherein S_tank is a surface area of FIG. 3, i.e., a sectional area of a passage in the tank 10, and S_tube is a surface area of FIG. 4, i.e., a sectional area of a passage of the tube 20. As shown in FIGS. 3 and 4, the S_tube is typically smaller than the sectional area of the passage in the tank 10, and due to the reduction of the sectional area of the passage, the flow rate is increased while the heat exchange medium is flowed from the tank 10 to the tube 20. Since the flow rate is directly related with a pressure upon the flowing of the fluid, an amount of pressure drop is also increased according as a difference between the sectional areas of passages of the tank 10 and the tube 20 is increased. In other words, it will be understood that, as the difference between the sectional areas of passages of the tank 10 and the tube 20 is increased, the flow rate is increased, and thus the heat exchange performance is increased. However, in case that the difference between the sectional areas is increased excessively, the heat exchange medium can not be flowed smoothly. And as the amount of pressure drop is increased excessively, the heat exchange performance is deteriorated.

In the heat exchanger 100, the factors of the tank 10 and tube 20, which directly exert an influence on the heat exchange performance per effective surface area and show a specific correlation with each other, is expressed as follows:

$\begin{array}{cc}\frac{S_{\mathrm{tube}}}{S_{\mathrm{tank}}},\frac{V_{\mathrm{tank}}}{A_{\mathrm{tube}}}& \left[\mathrm{Formula}1\right]\end{array}$

In the formula 1, S_tank is the sectional area of the passage of the tank 10 shown in FIG. 3, S_tube is the sectional area of the passage of the tube 20 shown in FIG. 4, V_tank is a volume of the tank 10, and A_tube is a total sectional area of the tubes 20. Further, the volume V_tank can be obtained by multiplying a length l_tank of the tank 10 by the sectional area S_tank of the passage of the tank 10, and the total sectional area A_tube can be obtained by multiplying each sectional area S_tank of the passage of the tube 20 by the number N of tubes. A formula 2 to be expressed blow shows a relationship between the factors.

V_tank=l_tank×S_tank

A_tube=N×>S_tube  [Formula 2]

Since the actual heat exchange is performed between the heat exchange medium in the tube 20 and the external air while the external air passes between the tubes 20, the heat exchange is substantially performed at the surface area of the tube 20 and the fin 30 perpendicular to a flowing direction of the external air. This surface area is the effective surface area S_eff as shown in FIG. 5. In order to express the heat exchange performance regardless of a size of the heat exchanger, a valuation of the heat exchange performance is obtained by only the effective surface area S_eff. Assuming that the heat exchange amount which is substantially generated is Q, the heat exchange amount Q_Ae per effective surface area is expressed as follows:

$\begin{array}{cc}{Q}_{\mathrm{Ae}}=\frac{Q}{S_{\mathrm{eff}}}& \left[\mathrm{Formula}3\right]\end{array}$

Since the present invention provides a dimension relationship between the tank 10 and the tube 20 capable of maximizing the heat exchange performance per effective surface area, the heat exchange performance per effective surface area is estimated on the basis of the heat exchange amount Q₀ per effective surface area which is a requirement in a vehicle. The heat exchange performance η per effective surface area is expressed as follows:

$\begin{array}{cc}\eta =\frac{Q_{\mathrm{Ae}}}{Q_0}& \left[\mathrm{Formula}4\right]\end{array}$

FIG. 6 is a graph showing the heat exchange performance η per effective area with respect to each factor, wherein FIG. 6a shows a change of η with respect to S_tube/S_tank and FIG. 6b shows a change of η with respect to V_tank/A_tube, wherein an area unit is cm², a volume unit is cm³ and a thermal unit is kcal/hr. As shown in the drawing, the heat exchange performance η is gradually increased and then reduced from a peak point. In other words, the heat exchange coefficient is increased, according as the difference between the sectional areas of passages is increased, and then the heat exchange coefficient is reduced due to the increase in the amount of pressure drop after the difference between the sectional areas of passages a certain point. Referring to the graph of FIG. 6a, when the value of S_tube/S_tank is 0.04˜0.06, the heat exchange performance η per effective surface area is optimized. Therefore, from this it is possible to deduce the relationship between the dimensions of the single tube and tank so as to optimize the heat exchange performance η per effective surface area.

Further, as shown in FIG. 6b, with respect to V_tank/A_tube, the heat exchange performance η is also increased gradually and then reduced from a peak point. In other words, as shown in FIG. 6b, when the value of V_tank/A_tube is 150˜230, the heat exchange performance η per effective surface area is optimized. The graph of FIG. 6a shows the relationship between the dimensions of each tube and tank, and the graph of FIG. 6b shows the relationship between the dimensions of the entire tubes and tanks. Thus, it is possible to deduce the relationship between the dimensions in the entire heat exchanger referring to the graphs.

Those skilled in the art will appreciate that the conceptions and specific embodiments disclosed in the foregoing description may be readily utilized as a basis for modifying or designing other embodiments for carrying out the same purposes of the present invention. Those skilled in the art will also appreciate that such equivalent embodiments do not depart from the spirit and scope of the invention as set forth in the appended claims.

INDUSTRIAL APPLICABILITY

According to a heat exchanger of the present invention, it is possible to deduce a relationship between the varying of dimensions relevant to fluid flowing in the header tank and heat exchange tube and the heat exchange performance according to the change of distributed fluid flowing and thus improves the dimensions and shapes of the tank and tube, thereby optimizing the heat exchange performance. Furthermore, it is possible to easily design the heat exchanger having the optimal heat exchange performance, thereby saving labor, cost, time and the like.

Claims

1. A heat exchanger, comprising: 0.04 < sectional   area   of   tube   ( S tube ) sectional   area   of   tank   ( S tank ) < 0.06

a plurality of tubes arranged (a) in parallel at regular distances to be extend in a ventilation directions and (b) so a heat exchange medium is adapted to flow through them;

an inlet tank into which the heat exchange medium is adapted to be introduced and then distributed to the plurality of tubes;

a fin interposed between the tubes for increasing the contact surface of the tubes with air passing between the tubes; and

an outlet tank for collecting and then discharging the heat exchange medium which is adapted to flow through the tube

wherein dimensions of the cross-sectional area Stube of the tube and the cross-sectional area Stank of the inlet tank or the outlet tank are in accordance with:

2. The heat exchanger according to claim 1, wherein the volume Vtank of the inlet tank or the outlet tank and the total cross-sectional area Atube of the tubes calculated by multiplying the sectional area of the tube and the number of tubes are in accordance with: 150 < volume   of   inlet   tank   or   outlet   tank   ( V tank )  total   sectional   area   of   tubes   ( A tube ) < 230