Boiler comprising heat shield structure

Technical field

The present invention relates to a boiler comprising a heat shield structure.

Background and object of the invention

Generally speaking, heat loss of boiler due to exhaust gas is in the range of 5 to 12%, thus taking a great portion of the overall heat loss. It is therefore of great significance to reduce heat loss caused by exhaust gas.

To reduce heat loss caused by exhaust gas during the operation of boiler, the temperature of exhaust gas discharged into the air through an exhaust gas container and then an exhaust gas duct should be reduced.

If the temperature of exhaust gas is lowered too much by way of increasing an area of heat-transfer surface, the water vapor contained in exhaust gas is condensed and reacts with nitric oxide and sulfuric oxide contained in exhaust gas to produce acid, thus corroding metallic part, e.g., heat-transfer surface.

Because of above-mentioned reasons, in the prior arts, the temperature of exhaust gas is set to 120-160 °C for power-generating boilers and 180-250 °C for small and medium-sized industrial or domestic boilers, respectively.

The object of the present invention is to provide a boiler comprising a heat-shield structure with less cost and material consumption, which can help reduce the temperature of exhaust gas to be lower than the threshold of the prior art and simultaneously prevent formation of dew point by overcoming the problems identified in the prior art.

Description of the invention

It is clear that the more heat amount generated from combustion of fuel is transferred to heat-transfer medium through heat-transfer surface, the more heat efficiency of boiler is improved.

One of the solutions to improve heat efficiency of boiler is to lower the temperature of exhaust gas by improving heat transfer characteristic, thus lowering heat loss due to exhaust gas.

In Ae present invention, for the purpose of improving heat efficiency of boiler, in particular, heat transfer characteristic of boiler, a boiler comprising a heat shield structure is provided, which can help reduce the temperature of exhaust gas to be lower than the threshold of the prior art and simultaneously prevent formation of dew point.

The boiler according to the present invention is a smoke-tube boiler or a water-tube boiler which is used for producing steam or hot water, mainly comprising: a boiler shell comprising a fire chamber, smoke-tubes or water-tubes, a heat-transfer-surface-of-exhaust-gas-container, a heat shield structure, and an exhaust gas container; a boiler proper cover; an exhaust gas outlet; and an exhaust gas duct.

The major part of heat amount of combustion gas originated from combustion of fuel in the fire chamber is transferred to heat-transfer medium through heat transfer surface by way of heat radiation, heat convection and heat conduction while combustion gas is passing along the inside of smoke-tubes or the outside of water-tubes and then finally is discharged through exhaust gas container and then through exhaust gas duct.

The boiler according to the present invention comprises a heat shield structure, which can help lower the temperature of exhaust gas and simultaneously prevent formation of dew point, installed to face a heat-transfer-surface-of-exhaust-gas-container inside the exhaust gas container.

The heat-transfer-surface-of-exhaust-gas-container means an upper tube-plate in the case of a smoke-tube boiler, or a virtual plane which touches the uppermost row of water-tubes that are farthest away from the fire chamber in the case of a water-tube boiler.

In the present invention, a cross-sectional area of the heat shield structure of the boiler equals to a cross-sectional area of the exhaust gas container minus 20 to 30% of a cross-sectional area of the fire chamber.

A lateral area of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure onto the heat-transfer-surface-of-exhaust-gas-container, is in the range of 10 to 24% of the cross-sectional area of the fire chamber.

The heat shield structure comprises a heat shield which can reflect residual heat of exhaust gas back to the heat-transfer-surface-of-exhaust-gas-container.

The heat shield structure of the boiler according to the present invention further comprises a thermal insulation layer on a side of the heat shield, which is not facing the heat-transfer-surface-of-exhaust-gas-container.

The heat shield structure of the boiler according to the present invention further comprises a fixing element which secures the heat shield structure to the inside of the exhaust gas container while adjusting a gap between the heat shield structure and the heat-transfer-surface-of-exhaust-gas-container. The heat shield structure of the boiler of the invention may be integrated with the boiler proper cover.

The boiler according to the present invention has a merit of improved heat transfer characteristic and prolonged service life compared to boilers of the prior art as it can help reduce the temperature of exhaust gas to be lower than the threshold of the prior art and simultaneously prevent formation of dew point with less cost and material consumption.

Description of drawings

Fig. 1 shows a three-dimensional diagram of a slanted smoke-tube boiler which comprises a heat shield structure installed inside an exhaust gas container according to an embodiment of the present invention.

Fig. 2 shows a schematic diagram of a slanted smoke-tube boiler which comprises a heat shield structure installed inside an exhaust gas container according to an embodiment of the present invention.

Fig. 3 shows a schematic diagram of a vertical smoke-tube boiler which comprises a heat shield structure installed inside an exhaust gas container according to an embodiment of the present invention.

Fig. 4 shows a three-dimensional diagram of a horizontal water-tube boiler which comprises a heat shield structure installed inside an exhaust gas container according to an embodiment of the present invention.

Fig. 5 shows a schematic diagram of a horizontal water-tube boiler which comprises a heat shield structure installed inside an exhaust gas container according to an embodiment of the present invention.

Fig 6 shows a schematic diagram of a slanted smoke-tube boiler wherein a heat shield structure is integrated with a boiler proper cover according to an embodiment of the present invention.

Fig 7 shows a schematic diagram of a horizontal water-tube boiler wherein a heat shield structure is integrated with a boiler proper cover according to an embodiment of the present invention.

Fig 8 shows a part drawing of a heat shield structure according to an embodiment of the present invention. Fig 9 shows a schematic diagram of a slanted smoke-tube boiler wherein a heat shield structure is integrated with a boiler proper cover according to another embodiment of the present invention.

Fig 10 shows a schematic diagram for indicating a lateral area of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure onto the heat-transfer-surface-of-exhaust-gas-container in smoke-tube boiler according to an embodiment of the present invention.

1: fire chamber; 2: heat transfer medium; 3: heat-transfer-surface-of-exhaust-gas-container (in the case of smoke-tube boiler, it means an upper tube-plate, while in the case of water-tube boiler, it means a virtual plane which touches the uppermost row of water-tubes that are farthest away from the fire chamber); 31 : inlet for heat transfer medium; 32: outlet for heat transfer medium; 4: heat shield structure; 40: fixing element which secures the heat shield structure to the inside of the exhaust gas container; 41 : heat shield; 42: thermal insulation layer; 43: sand; 44: hand grip of heat shield structure; 5: smoke-tube; 6: exhaust gas container; 7: exhaust gas outlet; 71 : inspection/cleaning hole for ash or soot accumulated on the heat-transfer-surface-of-exhaust-gas-container; 72: cleaning hole for ash or soot accumulated on the exhaust gas duct; 8: boiler proper cover; 9: exhaust gas duct; 10: water-tube; 11: boiler shell; 12: lateral area of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure onto the heat-transfer-surface-of-exhaust-gas-container

Preferred embodiment

In order to clearly understand technical solutions to accomplish the purpose of the invention, detailed embodiments of the present invention are described with reference to the drawings.

The heat shield structure and the slanted smoke-tube boiler, vertical smoke-tube boiler, horizontal water-tube boiler comprising the same described in examples and figures are merely specific examples which are in the range of protection of the present invention and it is not recognized as restriction to the range of protection of the present invention.

The cross-sectional area of the fire chamber of the boilers according to the embodiments of the present invention is 0.0346m ² and the cross-sectional area of exhaust gas duct equals to 8% of the cross-sectional area of the fire chamber.

In the embodiments of the present invention, propane gas is used as fuel and water as heat-transfer medium.

The temperature of exhaust gas in the embodiments of the invention is measured in the space where exhaust gas outlet 7 is ended and exhaust gas duct 9 is started.

Example 1:

As shown in Figs.l to 3, a smoke-tube boiler with a heat shield structure according to embodiments of the invention mainly comprises: a boiler shell 11 comprising a fire chamber 1, heat-transfer medium 2 surrounding the fire chamber 1, smoke tubes 5 and an upper tube-plate 3 which are heat transfer surfaces through which heat is transferred to heat-transfer medium 2, a heat shield structure 4, and an exhaust gas container 6; a boiler proper cover 8; an exhaust gas outlet 7; and an exhaust gas duct 9.

The exhaust gas container 6 is a space up to entrance of exhaust gas outlet 7 which is surrounded by the boiler proper cover 8 and the upper tube-plate 3.

The heat-transfer-surface-of-exhaust-gas-container means the upper tube plate3. Thus, the reference number of “3” is equally applied to the heat-transfer-surface-of-exhaust-gas-container.

The heat shield structure 4 is installed to face the heat-transfer-surface-of-exhaust-gas-container 3 inside the exhaust gas container 6.

There are inlet 31 at the bottom and outlet 32 at the top in the boiler shell 11 . Heat-transfer medium 2 flows in through the inlet 31 and out through the outlet 32.

There are an inspection/cleaning hole 71 for ash or soot accumulated on the heat-transfer-surface-of-exhaust-gas-container 3 and a cleaning hole 72 for ash or soot accumulated on the exhaust gas duct 9 at the exhaust gas outlet 7.

In an embodiment of the invention, the cross-sectional area of the heat shield structure 4 is the same with the cross-sectional area of the heat shield 41 and equals to the cross-sectional area of the exhaust gas container 6 minus 20 to 30% of the cross-sectional area of the fire chamber. And in an embodiment of the invention, the lateral area 12 of a virtual polyhedron as shown in Fig 10, which is obtained when vertically projecting the heat shield structure 4 onto the heat-transfer-surface-of-exhaust-gas-container 3, is in the range of 10 to 24% of the cross-sectional area of the fire chamber. The geometric centre of the cross-section of the heat shield structure 4 is identical with that of boiler.

As shown in Fig. 8, the heat shield structure 4 according to an embodiment of the present invention comprises: the heat shield 41 ; fixing element 40 which secures the heat shield structure 4 to the inside of the exhaust gas container, i.e. to the upper tube plate 3 or to the boiler proper cover 8, while adjusting the gap between the heat shield structure 4 and the heat-transfer-surface-of-exhaust-gas-container 3; and the thermal insulation layer 42 on a side of the heat shield 41 which is not facing the heat-transfer-surface-of-exhaust-gas-container 3.

In the embodiments of the present invention, the heat shield 41 of the heat shield structure 4 not only reflects a part of radiant energy of exhaust gas, which passes through the inside of smoke-tubes 5 and then flows out into the exhaust gas container 6, to the heat-transfer-surface-of-exhaust-gas-container 3, but intensifies convective heat transfer process during which the exhaust gas passes through in high speed along a narrow space between the heat shield 41 and the heat-transfer-surface-of-exhaust-gas-container 3.

In this way, the passageway for exhaust gas is lengthened to prolong the stay of exhaust gas at the inside of boiler and a dead zone where heat transfer is undergone inefficiently, thus heat transfer characteristic is improved.

In the embodiments of the present invention, stainless steel, or carbon steel, etc. may be used as a material for heat shield 41 .

In an embodiment of the invention, stainless steel 1Cr18Ni9 is used.

Heat-resistant glass fiber, vermiculite or coal ash may be used as a material for thermal insulation layer 42, and in an embodiment of the present invention, coal ash is used.

In the embodiments of the invention, the thermal insulation layer 42 of the heat shield structure 4 intensifies more the heat insulation effect of heat shield 41 .

The fixing elements may be secured to the heat-transfer-surface-of-exhaust-gas-container or boiler proper cover by using conventional means previously known in the art.

In an embodiment of the invention, 4 fixing elements 40, each of which comprises a pair of bolt and nut, are secured to the heat-transfer-surface-of-exhaust-gas-container 3 or the boiler proper cover 8 by welding for the purpose of adjusting the gap between the heat shield structure 4 and the heat-transfer-surface-of-exhaust-gas-container 3.

As shown in Fig. 6 and Fig.9, a slanted smoke-tube boiler comprises a heat shield structure 4 which is integrated with a boiler proper cover according to another embodiment of the invention.

In order to conduct analysis for comparing the heat transfer characteristic among the smoke-tube boilers in relation to the cross-sectional areas of the heat shield structure 4, i.e., to the cross-sectional areas of the heat shield 41 according to the embodiments of the invention, tests were conducted under the same combustion condition.

The heat shield structure 4 was installed with a gap of 10mm from the heat-transfer-surface-of-exhaust-gas-container.

Steam produced in miniature slanted smoke-tube boilers and in miniature vertical smoke-tube boilers were collected respectively in a vessel containing 4L of water through outlet 32.

In the case of the slanted smoke-tube boiler, the diameter of boiler shell was 210mm, the height of boiler shell 210mm and the total heat transfer area 0.325m ² .

In the case of the vertical smoke-tube boiler, the diameter of boiler shell was 210mm, the height of boiler shell 230mm and the total heat transfer area 0.336m ² .

The initial water temperature was 16°C and the duration of test was 6 minutes from the starting time when steam is produced, respectively.

After that, water in vessels was mixed and the final temperature of water was measured.

In the case of a slanted smoke-tube boiler and a vertical smoke tube boiler without heat shield structures, the temperatures of exhaust gas were 230 °C and 260 °C, respectively.

The table 1 shows the test results for slanted smoke tube boiler and the table 2 for vertical smoke-tube boiler.

Table!. Comparison of heat transfer characteristics among miniature slanted smoke-tube boilers

St A: the difference of the cross-sectional area of exhaust gas container minus the cross-sectional area of heat shield structure

G: the cross-sectional area of the fire chamber

Table2. Comparison of heat transfer characteristics among miniature vertical smoke-tube boilers

As can be seen in the table 1 and the table 2, when the cross-sectional area of the heat shield structure, i.e., the cross-sectional area of the heat shield, gets increased too much, incomplete combustion of fuel occurs, while it gets decreased too much, there is no certain effect of installing the heat shield structure, in terms of the heat transfer characteristic.

The test results show that the heat-transfer characteristic was improved and fuel burned sufficiently when the cross-sectional area of heat shield structure, i.e., the cross-sectional area of heat shield, equals to the cross-sectional area of the exhaust gas container minus 20-30% of the cross-sectional area of the fire chamber.

In another embodiment of the invention, the tests were conducted in order to compare the heat transfer characteristic between the slanted smoke-tube boilers or vertical smoke-tube boilers according to lateral areas 12 of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure 4 onto the heat-transfer-surface-of-exhaust-gas-container 3 under the same combustion conditions. Steam produced in miniature slanted smoke-tube boilers and in miniature vertical smoke-tube boilers were collected respectively in a vessel containing 4L of water through outlet 32.

In the case of the slanted smoke-tube boiler, the diameter of boiler shell was 210mm, the height of boiler shell 210mm and the total heat transfer area 0.325m ² .

In the case of the vertical smoke-tube boiler, the diameter of boiler shell was 210mm, the height of boiler shell 230mm and the total heat transfer area 0.336m ² .

The initial water temperature was 16 °C and the duration of test was 6 minutes from the starting time when steam is produced, respectively.

After that, water in vessels was mixed and the final temperature of water was measured.

The diameter of the heat shield structure 4, i.e. the diameter of the heat shield 41 is 180mm and the cross-sectional area of the heat shield structure 4 is equals to the cross-sectional area of exhaust gas container 6 minus 26% of the cross-sectional area of the fire chamber.

The test results are shown in the table 3 and the table 4.

Table3. Comparison of heat transfer characteristics among miniature slanted smoke-tube boilers according to lateral areas of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure onto the heat-transfer-surface-of-exhaust-gas-container

Table4. Comparison of beat transfer characteristics of miniature vertical smoke-tube boilers according to lateral areas of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure onto the heat-transfer-surface-of-exhaust-gas-container

X< d: the gap between the heat shield surface of the heat shield structure, which comprises the heat shield and thermal insulation layer, and the heat-transfer-surface-of-exhaust-gas-container; where oo means that there is no heat shield structure installed.

X? *: the gap between the heal shield of the heat shield structure without the thermal insulation layer and the heat-transfer-surface-of-exhausl-gas-container

As can be seen in the table 3 and table 4, when the lateral area of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure 4 onto the heat-transfer-surface-of-exhaust-gas-container 3, gets decreased too much, incomplete combustion of fuel occurs, while it gets increased too much, there is no certain effect of installing the heat shield structure, in terms of the heat transfer characteristic.

The test results show that the heat-transfer characteristic was improved and fuel burned sufficiently when the lateral area of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure onto the heat-transfer-surface-of-exhaust-gas-container, is in the range of 10 to 24% of the cross-sectional area of the fire chamber.

Example 2:

As can be seen in Figs. 4, 5 and 7, a water-tube boiler with a heat shield structure according to embodiments of the invention mainly comprises: a boiler shell 11 comprising a fire chamber 1 , heat-transfer medium 2, water-tubes 10 surrounding heat-transfer medium 2 which are heat transfer surfaces through which heat is transferred to heat-transfer medium 2, a heat-shield structure 4, and an exhaust gas container 6; a boiler proper cover 8; an exhaust gas outlet 7; and an exhaust gas duct 9.

The exhaust gas container 6 is a space up to entrance of exhaust gas outlet 7 which is surrounded by the boiler proper cover 8 and a virtual plane which touches the uppermost row of water-tubes that are farthest away from the fire chamber 1.

The heat-transfer-surface-of-exhaust-gas-container 3 means the virtual plane which touches the uppermost row of water-tubes that are farthest away from the fire chamber 1.

The heat shield structure 4 is installed to face the heat-transfer-surface-of-exhaust-gas-container 3 inside the exhaust gas container 6.

There are inlet 31 at the bottom and outlet 32 at the top in the boiler shell 11. Heat-transfer medium 2 flows in through the inlet 31 and out through the outlet 32.

There are an inspection/cleaning hole 71 for ash or soot accumulated on the heat-transfer-surface-of-exhaust-gas-container 3 and a cleaning hole 72 for ash or soot accumulated on the exhaust gas duct 9 at the exhaust gas outlet 7.

Tn an embodiment of the invention, the cross-sectional area of the heat shield structure 4 is the same with the cross-sectional area of the heat shield 41 and equals to the cross-sectional area of the exhaust gas container 6 minus 20 to 30% of the cross-sectional area of the fire chamber. And in an embodiment of the invention, the lateral area 12 of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure 4 onto the heat-transfer-surface-of-exhaust-gas-container 3, is in the range of 10 to 24% of the cross-sectional area of the fire chamber.

The geometric centre of the cross-section of the heat shield structure 4 is identical with that of boiler.

As shown in Fig. 8, the heat shield structure 4 according to an embodiment of the present invention comprises: the heat shield 41; fixing element 40 which secures the heat shield structure 4 to the inside of the exhaust gas container, i.e. to the boiler proper cover 8, while adjusting the gap between the heat shield structure 4 and the heat-transfer-surface-of-exhaust-gas-container 3; and the thermal insulation layer 42 on a side of the heat shield 41 which is not facing the heat-transfer-surface-of-exhaust-gas-container 3.

In the embodiments of the present invention, the heat shield 41 of the heat shield structure 4 intensifies not only thermal radiation process of exhaust gas, which passes through outer surface of water-tubes and then flows out into the exhaust gas container 6, to the heat-transfer-surface-of-exhaust-gas-container 3, but also convective heat transfer process during which the exhaust gas passes through in high speed along a narrow space between the heat shield 41 and the heat-transfer-surface-of-exhaust-gas-container 3.

In this way, the passageway for exhaust gas is lengthened to prolong the stay of exhaust 'gas at the inside of boiler and to let exhaust gas flow evenly along heat transfer surfaces, thus heat transfer characteristic is improved.

In the embodiments of the present invention, stainless steel, or carbon steel, etc. may be used as a material for heat shield 41 .

In an embodiment of the invention, stainless steel 1Cr18Ni9 is used.

Heat-resistant glass fiber, vermiculite or coal ash may be used as a material for thermal insulation layer 42, and in an embodiment of the present invention, coal ash is used.

In the embodiments of the invention, the thermal insulation layer 42 of the heat shield structure 4 intensifies more the heat insulation effect of heat shield 41.

The fixing elements may be secured to the heat-transfer-surface of-exhaust-gas-container or boiler proper cover by using conventional means previously known in the art.

In an embodiment of the invention, 4 fixing elements 40, each of which comprises a pair of bolt and nut, are secured to the boiler proper cover 8 by welding for the purpose of adjusting the gap between the heat shield structure 4 and the heat-transfer-surface-of-exhaust-gas-container 3.

As shown in Fig. 7, a horizontal water-tube boiler comprises a heat shield structure 4 which is integrated with a boiler proper cover according to another embodiment of the invention.

In order to conduct analysis for comparing the heat transfer characteristic among horizontal water-tube boilers in relation to the cross-sectional areas of the heat shield structure 4, i.e., to the cross-sectional areas of heat shield 41 according to the embodiments of the invention, tests were conducted under the same combustion condition. The heat shield structure 4 was installed with the gap of 10mm from the heat-transfer-surface-of-exhaust-gas-container.

Steam produced in miniature horizontal water-tube boilers were collected respectively in a vessel containing 4L of water through outlet 32.

In the case of the horizontal water-tube boiler, the diameter of boiler shell was 210mm, the height of boiler shell 210mm and the total heat transfer area 0.379m ² .

The initial water temperature was 16°C and the duration of test was 6 minutes from the starting time when steam is produced, respectively.

After that, water in vessels was mixed and the final temperature of water was measured.

In the case of a horizontal water-tube boiler without heat shield structure, the temperature of exhaust gas was 170 °C.

The test results are shown in the table 5.

Table 5 Comparison of heat transfer characteristics among miniature horizontal water-tube boilers

As can be seen in the table 5, when the cross-sectional area of the heat shield structure, i.e., the cross-sectional area of the heat shield, gets increased too much, incomplete combustion of fuel occurs, while it gets decreased too much, there is no certain effect of installing the heat shield structure, in terms of the heat transfer characteristic.

The test results show that the heat-transfer characteristic was improved and fuel burned sufficiently when the cross-sectional area of heat shield structure, i.e., the cross-sectional area of heat shield, equals to the cross-sectional area of the exhaust gas container minus 20-30% of the cross-sectional area of the fire chamber.

In another embodiment of the invention, the tests were conducted in order to compare the heat transfer characteristic between the horizontal water-tube boilers according to lateral areas 12 of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure 4 onto the heat-transfer-surface-of-exhaust-gas-container 3 under the same combustion conditions.

Steam produced in miniature horizontal water-tube boilers were collected respectively in a vessel containing 4L of water through outlet 32.

In the case of the horizontal water-tube boiler, the diameter of boiler shell was 210mm, the height of boiler jhell 210mm and the total heat transfer area 0.379m ² .

The initial water temperature was 16“C and the duration of test was 6 minutes from the starting time when steam is produced, respectively.

After that, water in vessels was mixed and the final temperature of water was measured.

The diameter of the heat shield structure 4, i.e. the diameter of the heat shield 41 is 180mm and the cross-sectional area of the heat shield structure 4 is equal to the cross-sectional area of exhaust gas container 6 minus 26% of the cross-sectional area of the fire chamber.

The test results are shown in the table 6. Table6. Comparison of heat transfer characteristics among miniature horizontal water-tube boilers according to lateral areas of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure onto the heat-transfer-surface-of-exhau st-gas-container

As can be seen in the table 6, when the lateral area of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure 4 onto the heat-transfer-surface-of-exhaust-gas-container 3, gets decreased too much, incomplete combustion of fuel occurs, while it gets increased too much, there is no certain effect of installing the heat shield structure, in terms of the heat transfer characteristic.

The test results show that the heat-transfer characteristic was improved and fuel burned sufficiently when the lateral area of a virtual polyhedron, which is obtained when vertically projecting the heat shield structure onto the heat-transfer-surface-of-exhaust-gas-container, is in the range of 10 to 24% of the cross-sectional area of the fire chamber.

Thus, under the same combustion conditions, when the heat transfer areas of boilers of the invention where heat shield structure is installed in a rational manner are equal to the heat transfer areas of boilers of prior art, the convective heat transfer characteristic and the radiative heat transfer characteristic of the boilers according to the present invention are improved, thus resulting in higher heat transfer amount, lower exhaust gas temperature, and improved heat transfer characteristic.

The technical solutions according to the present invention can be used in all kinds of thermal exchange apparatus where heat radiation and heat convection exist.

The claimed range of protection of the present invention is not restricted to the embodiments of the invention and it is believed that the change, modification and/or replacement to the embodiments of the invention remains consistent to the person skilled in the art unless it is not beyond the idea of the invention.