WO2003050467A1

WO2003050467A1 - Pin tube type heat exchanger and air conditioner and refrigerator using the same

Info

Publication number: WO2003050467A1
Application number: PCT/KR2002/001075
Authority: WO
Inventors: Kwan Ho Im
Original assignee: Fin Tube Technology Co., Ltd.
Priority date: 2001-12-08
Filing date: 2002-06-05
Publication date: 2003-06-19
Also published as: AU2002306139A1

Abstract

A heat exchanger using tubes (2) having novel fins, and an air conditioning system and a freezer each having a condenser and an evaporator using this heat exchanger. Inner fins (5) are formed at the inner periphery of a tube (2) to divide the tube (2) into a plurality of sub-channels, sub-fins are formed at both lateral portions in each of the inner fins (5), and wave-shaped outer fins are formed along an angle of circumference at the outer periphery of the tube to improve the heat transfer capacity of the heat exchanger. Since the heat exchanger is improved in heat transfer capacity, the air conditioner or the freezer has same cooling capacity even though compression performed by a compressor is reduced, and thus power consumption can be remarkably saved.

Description

PIN TUBE TYPE HEAT EXCHANGER AND AIR CONDITIONER AND REFRIGERATOR USING THE SAME

TECHNICAL FIELD The present invention relates to a fin-tube heat exchanger and an air conditioner and a freezer using the same. In particular, the invention relates to an improved structure of fin-tube heat exchanger in use for both a condenser and an evaporator of an air conditioner and a freezer, in which inner fins are formed at the inner periphery of a tube to divide the tube into a plurality of sub-channels, sub-fins are formed at both lateral portions in each of the inner fins, and wave-shaped outer fins are formed along an angle of circumference at the inner periphery of the tube so that the heat exchanger can be improved in its heat transfer capacity.

BACKGROUND ART As desires for pleasant lives are greatly increasing along with rise in income level, more air conditioners are being consumed in summer.

Conventional air conditioning systems were developed several decades ago. These air conditioning systems have not achieved any remarkable improvement in cooling efficiency up to the present except that electronic control devices have been developed. For the purpose of enhancing the cooling efficiency of the air conditioning systems, it is necessary to improve the performance of a compressor, a condenser and an evaporator. The compressor has been improved in its efficiency up to a considerable degree, whereas the efficiency of the condenser and the evaporator still has much room for improvement. Fig. 9 is a perspective view of a conventional plate type heat exchanger. A conventional air conditioning system has used a condenser and an evaporator each made of a continuous plate fin and tube type heat exchanger in which copper tubes 102 are inserted into holes of aluminum fins 101 as shown in Fig. 9. This heat exchanger exhibits very large heat resistance in heat transfer between the copper tubes 102 and the aluminum fins 101 since they are not closely contacted each other. Experimental values show that the above heat resistance is about 18 to 33% of entire heat resistance. In order to solve this problem, the distance between the aluminum fins 101 was shortened to increase the number of the aluminum fins 101. However, this arrangement has showed little improvement. Cooling efficiency should enhance to reduce power consumption of an air conditioning system. To this end, it is necessary to reduce the work of a compressor while enhancing the cooling efficiency per 1kg of refrigerant. The work of the compressor can be reduced by decreasing the ratio between discharging and sucking pressures. When this ratio is decreased, however, a saturation pressure in the condenser and thus a saturation temperature are lowered to decrease a difference between the saturation temperature and the temperature of air causing difficulty in completely condensing refrigerant. Then, the work of the compressor is not decreased unless the air conditioning system has a high performance condenser and thus power consumption is not reduced.

DISCLOSURE OF INVENTION The present invention has been made in view of the foregoing problems and it is therefore an object of the present invention to provide a heat exchanger improved in heat transfer capacity and an air conditioning system and a freezer having the above heat exchanger, in which inner fins are formed at the inner periphery of a tube to divide the tube into a plurality of sub-channels, sub-fins are formed at both lateral portions in each of the inner fins, and wave-shaped outer fins are formed along an angle of circumference at the outer periphery of the tube so that power consumption can remarkably be reduced while same cooling capacity is provided.

According to an aspect of the invention for realizing the foregoing objects, there is provided a fin-tube heat exchanger comprising a tube, wherein the tube includes: a plurality of inner fins formed at the inner periphery thereof; and a plurality of outer fins formed at the outer periphery thereof. It is preferred that the inner fins may be radially extended from a central axis of the tube to the inner periphery of the tube.

It is also preferred that the inner fins may be helically formed along the central axis of the tube.

It is preferred that each of the inner fins may have a plurality of semi-global sub-fins projected from a surface thereof.

It is preferred that the outer fins may be annular sheets formed along the outer periphery of the tube to a designated height.

It is also preferred that each of the outer fins may be wave-shaped having projections and depressions which are alternately formed along a periphery of the tube. It is preferred that each of the projections of the each outer fin may be diverged from an adjacent one of the depressions of the each outer fin as the projections and the depressions are radially extended.

Also, it is preferred that the outer fins may form an angle of about 60 to 120 deg. from the outer periphery of the tube. According to another aspect of the invention for realizing the foregoing objects, there is also provided a fm-tube heat exchanger comprising: an inner tube having a plurality of inner fins formed at the inner periphery thereof; and an outer tube having a plurality of outer fins formed at the outer periphery thereof, wherein the im er tube is pressed into the inner periphery of the outer tube. According to further another aspect of the invention for realizing the foregoing objects, there is also provided an air conditioning system comprising: a condenser including a first heat exchanger having first tubes, wherein each of the tubes includes a plurality of first inner fins formed at the inner periphery thereof and a plurality of first outer fins formed at the outer periphery thereof; and an evaporator including a second heat exchanger having second tubes, wherein each of the second tubes includes a plurality of second inner fins formed at the inner periphery thereof and a plurality of second outer fins formed at the outer periphery thereof.

It is preferred that the first tubes of the condenser may be arrayed into a box-shaped or cylindrical configuration. It is also preferred that the evaporator further may include: an inlet manifold connected to the second tubes in a first portion of the evaporator; an outlet manifold connected to the second tubes in a second portion of the evaporator; and U-tubes coupled respectively to ends of the second tubes for connecting each of the second tubes arrayed in a row to a corresponding one of the tubes arrayed in an adjacent row. Also, it is preferred that the first or second tubes may be arranged vertical.

According to further another aspect of the invention for realizing the foregoing objects, there is also provided a freezer comprising a heat exchanger having a tube, wherein the tube includes: a plurality of inner fins formed at the inner periphery thereof; and a plurality of outer fins formed at the outer periphery thereof. The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a front elevation view of a fin-tube heat exchanger according to a preferred embodiment of the invention;

Fig. 2 is a partial sectional view of the fm-tube heat exchanger according to the preferred embodiment of the invention;

Fig. 3 is a side elevation view of inner fins of the fm-tube heat exchanger according to the first preferred embodiment of the invention;

Fig. 4 is a side elevation view of the fin-tube heat exchanger according to the first preferred embodiment of the invention;

Fig. 5 is a front elevation view of a fin-tube heat exchanger according to an alternative embodiment of the invention; Fig. 6 is a perspective view of a condenser in an air conditioning system of the invention;

Fig. 6A is a magnification of A part in Fig. 6;

Fig. 7 is a perspective view of an evaporator in an air conditioning system of the invention; Fig. 7 A is a magnification of B part in Fig. 7;

Fig. 8 is a side elevation view of the air conditioning system of the invention; and

Fig. 9 is a perspective view of a conventional plate type heat exchanger. BEST MODE FOR CARRYING OUT THE INVENTION The following detailed description will present constructions of fin-tube heat exchangers according to preferred embodiments of the invention in reference to the accompanying drawings. Fig. 1 is a front elevation view of a fm-tube heat exchanger according to a preferred embodiment of the invention, Fig. 2 is a partial sectional view of the fm-tube heat exchanger according to the preferred embodiment of the invention. As shown in Figs. 1 and 2, five imier fins 5 are radially formed inside a tube 2, extending from a central axis of the tube 2 to an inner peripheral surface of the tube 2. The five inner fins 5 divide an inner space of the tube 2 into five sub-channels.

Semi-global sub-fins 7 are formed across entire surfaces of the inner fins 5 in both lateral portions thereof at a radius of approximately 0.4mm in order to increase heat transfer area.

Outer fins 10 are annular sheets having a height of approximately 12mm, formed along an outer peripheral surface of the tube 2. Each of the outer fins 10 is wave-shaped having projections 11 and depressions 12 alternatingly formed along an outer periphery of the tube 2 in order to increase heat transfer area while improving heat transfer efficiency based upon fluid flow characteristics. The projections 11 and the depressions 12 are formed smoothly along the outer peripheral direction so that surfaces of the outer fins 10 are slowly streamlined without sudden irregularities.

The projections 11 and the depressions 12 are formed across the whole surface of the outer fins 10 from a portion of the tube 2 coupled with the outer fins 10 to an end ofthe tube 2.

Fig. 4 is a side elevation view of the fm-tube heat exchanger according to the preferred embodiment of the invention. As shown in Fig. 4, the outer fins 10 are formed perpendicular from the outer peripheral surface of the tube and radially extended therefrom. The projections 11 and the depressions 12 are alternatively formed in radial directions corresponding to directions of fluid flowing around the tube 2. Each of the outer fins 10 is spaced from any adjacent one to an interval of about 2.54mm. The outer fins 10 and the outer peripheral surface of the tube 2 preferably have an included angle of about 60 to 120 deg., and more preferably, about 90 deg. At an angle under 60 or over 120 deg., the resistance of fluid passing through the tube 2 is increased, thereby producing vibration and noise. Also, the pressure loss of fluid is increased by large quantities, thereby creating unnecessary power consumption of a blower (not shown). As the angle between the outer peripheral surface of the tube 2 and the outer fins 10 is reduced, the flow rate of fluid passing through the tube 2 is also decreased, thereby dropping the cooling ability of fluid.

Fig. 3 is a side elevation view partially illustrating the inner fins of the fm-tube heat exchanger according to the preferred embodiment of the invention. As shown in Fig. 3, the inner fins 5 within the tube 2 are helically extended along a central axis of the tube 2 at a designated angle of rotation per unit length as teeth in a helical gear. The inner fins 5 form sub-channels which are also helically formed along the central axis of the tube 2.

Fig. 5 is a front elevation view of a fm-tube heat exchanger according to an alternative embodiment of the invention. As shown in Fig. 5, the heat exchanger includes an inner tube 15 and an outer tube 14 wrapping the outside of the inner tube 15.

The inner fins 5 are formed at the inner periphery of the inner tube 15, and helically extended along a central axis of the inner tube 15 at a designated angle of rotation per unit length as teeth of a helical gear. Semi-global sub-fins 7 are formed across entire surfaces of the inner fins 5 in both lateral portions thereof at a radius of about 0.4mm in order to increase heat transfer area.

The inner tube 15 is inserted into the outer tube 14, and an outer peripheral surface of the inner tube 15 is pressed against an inner peripheral surface of the outer tube 14. The outer fins 10 are shaped as annular sheets and projected from the outer peripheral surface of the outer tube 14 with a height of about 12mm. Each of the outer fins 10 are wave-shaped having projections 11 and depressions 12 alternatingly formed along an outer periphery of the tube 2.

The tube 2, the outer fins 10 and the inner fins 5 are preferably made of metal, and in particular, copper in the invention.

Fig. 6 is a perspective view of a condenser in an air conditioning system of the invention, and Fig. 6A is a magnification of A part in Fig. 6. As shown in Figs. 6 and

6 A, annular guide sections 33 for U-tubes are arranged in upper and lower portions of a condenser 30. The guide sections 33 have a plurality of first U-tube guide holes 34 for receiving a plurality of tubes 2 each having the plurality of inner fins 5 in the imier peripheral surface and the plurality of outer fins 10 in the outer peripheral surface.

The tubes 2 are vertically arranged along the first guide holes 34 in the U-tube guide sections 33 forming the upper and lower portion of the condenser 30 so as to constitute the condenser 30 in the shape of a round fence. Two tubes 2 are exposed through two guide holes 34. One ends of the tubes 2 are connected to two inlets 35, which are rectangularly bent, so that refrigerant 25 from a compressor (not shown) can be introduced into the tubes 2.

The other ends of the tubes 2 of the condenser 30 are opposed to the ends of the tubes 2 connected to the inlets 35. The other ends of the tubes 2, which are exposed through two guide halls 34, are connected respectively to two outlets 37, which are rectangularly bent, for discharging refrigerant from the condenser.

In the upper portion of the condenser 30, the upper end of any tube 2 projected through a pertinent guide hole 34 is connected to the upper end of a next tube 2 projected through a next guide hole 34 via a U-tube 36. In the lower portion of the condenser 30, the lower ends of the connected tubes 2 are connected respectively to the lower ends of other adjacent tubes 2 via U-tubes.

That is, the plurality of tubes 2 are com ected together alternatively in the upper and lower portions of the condenser 30 from the inlets 35 to the outlets 37 in such a fashion that a first tube 2 is connected to a second tube 2 in the upper portion of the condenser 2 and the second tube 2 is connected to a third tube 2 in the lower portion of the condenser 30. Since the condenser 30 has the two inlets 35 and the two outlets 37, half of the whole tubes 2 are connected together from one inlet 35 to one outlet 37 clockwise of the U-tube guide sections 33 and the other tubes 2 are comiected together from the other inlet 35 to the other outlet 37 counterclockwise of the U-tube guide sections 33.

Fig. 7 is a perspective view of an evaporator in an air conditioning system of the invention, and Fig. 7A is a magnification of B part in Fig. 7, and Fig. 8 is a side elevation view of the air conditioning system of the invention. As shown in Figs. 7 and 7A, an evaporator 40 has U-tube guide plates 43 in upper and lower portions thereof. Second U-tube guide holes 44 for guiding the tubes 2 are formed in three rows in the U-tube guide plates 43.

The tubes 2 of the fm-tube heat exchanger of the invention are inserted into the second U-tube guide holes 44. The tubes 2 in the first row from the front of the evaporator 40 are connected to an inlet manifold 42, which is installed under the evaporator 40 and functions as a path of refrigerant flowing from the condenser to the evaporator 40. The inlet manifold 42 includes an inlet manifold entrance 45 for receiving refrigerant from the condenser and a plurality of inlet manifold exits 46 for flowing refrigerant to the evaporator 40.

As shown in Fig. 8, three tubes 2 in the longitudinal position of the upper or lower guide plate 43 are connected together via U-tubes 36. The tubes 2 in the third row are comiected via an outlet manifold 41 which is placed over the evaporator 40. The tubes 2 in the third row are connected respectively to a plurality of entrances 48 of the outlet manifold 41. The outlet manifold 41 has an outlet manifold exit 49 for discharging refrigerant. Hereinafter description will be made about the operation of the fin-tube heat exchanger of the invention.

Since the direction of fluid passing through the heat exchanger is uniform, fluid flowing through any of the sub-channels in a specific position may have heat exchange by a larger or smaller quantity than fluid flowing through other one of the sub-channels according to an angle of circumference of the each tube 2. Therefore, the inner fins 5 of the fin-tube heat exchanger are helically formed around a central axis of the tube 2 and thus form the helical sub-channels in order to overcome the above phenomenon as well as level the quantity of heat exchange. Further, the helical inner fins 5 advantageously have larger heat transfer areas over linear ones. The semi-global sub-fins 7 are formed at both sides of the inner fins 5 to raise the heat transfer coefficient of the heat exchanger. The helical inner fins 5 increase the heat transfer area of the fin-tube heat exchanger up to about 300% compared to a conventional heat exchanger, and the semi-global sub-fins 7 in the inner fins 5 increase the heat transfer coefficient in vaporization or condensation for about 70%. h order to utilize the improvement of heat transfer inside the tube 2, the outer fins 10 are formed to increase the heat transfer area of the outer peripheral surface of the tube 2. Alternatively, the heat transfer area of the outer peripheral surface of the tube 2 may be increased in a hydrodynamic fashion. The outer fins 10 are wave-shaped having the projections 11 and the depressions 12 so that fluid colliding against the projections 11 increases the flow rate of fluid contacting with the projections and vortex occurring in the depressions 12 increases the flow rate of fluid contacting with the depressions 12. As a result, this greatly enhances the heat transfer efficiency of the fin-tube heat exchanger.

Hereinafter description will be made about the operation of the air conditioning system including the fin- tube heat exchanger of the invention.

The condenser 30 and the evaporator 40 will be primarily described. As shown in Fig. 6, in operation of the blower (not shown) over the condenser 30 , air 20 surrounding the condenser 30 performs heat exchange via the fin-tube heat exchanger and then is exhausted through the upper portion of the condenser 30. As shown in Fig. 8, the evaporator 40 has the tubes 2 arrayed in three rows, in which refrigerant introduced through the inlet manifold 42 performs heat exchange with surrounding air 21 while air 21 passes through the three tubes 2 by the rear blower (not shown). Then, refrigerant is discharged again to the compressor (not shown) via the outlet manifold 41. Table 1 and Table 2 respectively report specifications of the condenser 30 and the evaporator 40 used in the air conditioning system. Table 1

Table 2

The temperatures of air in the specifications are set in reference to the temperate zones such as Korea having a mean summer temperature of about 40 ^°C .

Hereinafter description will be made about an operating cycle of the air conditioning system using the condenser and the evaporator. R-22 is used as refrigerant. Where refrigerant passes through the compressor, the condenser and the evaporator, the compressor (not shown) abiabatically compresses gaseous refrigerant raising its pressure from about 645kpa up to 1612kpa so that refrigerant changes into overheated vapor of about 81 ^°C . This overheated vapor is transported into the condenser where it is cooled down to a saturation temperature of about 42.5 ^°C and then completely condensed. Condensed refrigerant is overcooled for about 2^°C and then transported to an expansion value where it is abiabatically expanded to have a pressure of about 654.9kpa. 19.6% of refrigerant is evaporated in this abiabatic expansion, and remaining 80.4% of refrigerant is evaporated in the evaporator. Refrigerant has a saturation temperature of about 10^°C, which is higher for about 3 ^°C than that in a general air conditioning system using a conventional tube type heat exchanger. When gaseous refrigerant evaporated in the evaporator is transported to the compressor, an operating cycle is completed.

The operating cycle of the invention has operating conditions more excellent than those of a conventional operating cycle using the conventional tube-type heat exchanger, i.e., the invention has a condensing temperature in the condenser which is lower for about 8 ^°C than that of the conventional cycle and an evaporating temperature in the evaporator which is higher for about 3 ^°C than that of the conventional cycle. As a result, the performance factor of the operating cycle of the invention is raised for about 41%. The invention can obtain such a high efficient operating cycle because the tubes 2 used in the condenser and the evaporator have a large amount of heat transfer capacity enabling the condenser to have the condensing temperature of 42.5 ^°C .

Although the outer fins 10 of the tubes 2 are wave-shaped having the projections and the depressions in the preferred embodiment of the invention, the present invention is not restricted to this configuration. Rather the invention can adopt planar outer fins.

The condenser is cylindrically shaped in the preferred embodiment of the invention, whereas the invention is not restricted to this but can provide the condenser in the form of a triangular, quadrangular, pentagonal, hexagonal or octagonal column.

Further, the freezer of the invention is widely applicable to apparatuses having a freezing function such as a refrigerator and a refrigerated truck.

Although the fm-tube heat exchanger is applied to the air conditioning system and the freezer according the preferred embodiment of the invention, the invention is not restricted to this but can be applied to other apparatus such as a boiler which adopts a heat exchanger. Further, although the tubes, the outer fins and the inner fins are made of copper in the preferred embodiment of the invention, they are illustrative purposes only. Rather, the tubes, outer fins and the inner fins can be made of other metal such as stainless and brass.

INDUSTRIAL APPLICABILITY As described above, the fin-tube heat exchanger of the invention can be applied to various apparatuses such as home and industrial air conditioning systems, freezers and refrigerated trucks. The fin-tube heat exchanger can realize same cooling capacity while consuming less power thereby saving energy and protecting environment.

While the present invention has been described with reference to the particular illustrative embodiments, it is not to be restricted by the embodiments but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiments without departing from the scope and spirit of the present invention.

Claims

Claims:

1. A fin-tube heat exchanger comprising a tube (2), wherein the tube (2) comprises: a plurality of inner fins (5) fonned at the inner periphery thereof; and a plurality of outer fins (10) formed at the outer periphery thereof.

2. A fin-tube heat exchanger as set forth in claim 1, wherein the inner fins (5) are radially extended from a central axis of the tube (2) to the inner periphery of the tube (2).

3. A fin-tube heat exchanger as set forth in claim 2, wherein the inner fins (5) are helically formed along the central axis of the tube (2).

4. A fm-tube heat exchanger as set forth in any one of preceding claims 1 to 3, wherein each of the inner fins (5) has a plurality of semi-global sub-fins (7) projected from a surface thereof.

5. A fm-tube heat exchanger as set forth in claim 1, wherein the outer fins (10) are annular sheets formed along the outer periphery of the tube (2) to a designated height.

6. A fm-tube heat exchanger as set forth in claim 1 or 5, wherein each of the outer fins (10) is wave-shaped having projections 11 and depressions (12) which are alternately formed along a periphery of the tube (2).

7. A fm-tube heat exchanger as set forth in claim 6, wherein each of the projections (11) of the each outer fin (10) is diverged from an adjacent one of the depressions (12) of the each outer fin (10) as the projections (11) and the depressions (12) are radially extended.

8. A fm-tube heat exchanger as set forth in claim 6, wherein the outer fins (10) form an angle of about 60 to 120 deg. from the outer periphery of the tube (2).

9. A fin-tube heat exchanger comprising: an inner tube (15) having a plurality of inner fins (5) formed at the inner periphery thereof; and an outer tube (14) having a plurality of outer fins (10) formed at the outer periphery thereof, wherein the inner tube (15) is pressed into the inner periphery of the outer tube (14).

10. An air conditioning system comprising: a condenser (30) including a first heat exchanger having first tubes (2), wherein each of the tubes (2) includes a plurality of first inner fins (5) formed at the inner periphery thereof and a plurality of first outer fins (10) formed at the outer periphery thereof; and an evaporator (40) including a second heat exchanger having second tubes (2), wherein each of the second tubes (2) includes a plurality of second inner fins (5) formed at the inner periphery thereof and a plurality of second outer fins (10) formed at the outer periphery thereof.

11. An air conditioning system as set forth in claim 12, wherein the first tubes 2 of the condenser (30) are arrayed into a box-shaped or cylindrical configuration.

12. An air conditioning system as set forth in claim 13, wherein the evaporator (40) further includes: an inlet manifold (42) connected to the second tubes (2) in a first portion of the evaporator (40); an outlet manifold (41) connected to the second tubes (2) in a second portion of the evaporator (40); and

U-tubes (36) coupled respectively to ends of the second tubes (2) for connecting each of the second tubes (2) arrayed in a row to a corresponding one of the tubes (2) arrayed in an adjacent row.

13. An air conditioning system as set forth in claim 12, wherein the first or second tubes (2) are arranged vertical.

14. A freezer with a heat exchanger having a tube (2), wherein the tube (2) comprises: a plurality of inner fins (5) formed at the inner periphery thereof; and a plurality of outer fins (10) formed at the outer periphery thereof.