WO2011135333A2

WO2011135333A2 - Heat exchanger

Info

Publication number: WO2011135333A2
Application number: PCT/GB2011/050773
Authority: WO
Inventors: Dumitru Fetcu
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-04-26
Filing date: 2011-04-19
Publication date: 2011-11-03
Anticipated expiration: 2012-10-26
Also published as: WO2011135333A3; GB201006862D0; GB2479866A

Abstract

A heat exchanger for cooling a gas from a first temperature to a second temperature is disclosed. The exchanger comprises a first heat exchanging chamber, a second heat exchanging chamber and an array of heat pipes which are arranged to extend from within the first heat exchanging chamber to within the second heat exchanging chamber. The first heat exchanging chamber comprises an inlet for receiving a coolant into the chamber and an outlet through which the coolant can exit the first chamber, the coolant being arranged to pass over the portion of the heat pipes which extend within the first chamber. The second heat exchanging chamber comprises an inlet for receiving the gas at a first temperature into the chamber and an outlet through which the gas can exit the second chamber at a second temperature, the gas being arranged to pass over the portion of the heat pipes which extend within the second chamber. The first and second chambers further comprise at least one baffle which is arranged to deflect the flow coolant and the gas, respectively, as the coolant and the gas pass from the inlet to the outlet of the respective chamber.

Description

Heat Exchanger

The present invention relates to a heat exchanger and particularly, but not exclusively to a heat exchanger comprising heat pipes.

A heat pipe is a hermetically sealed evacuated tube typically comprising a mesh or sintered powder wick and a working fluid in both the liquid and vapour phase. When one end of the tube is heated the liquid turns to vapour upon absorbing the latent heat of vaporization. The hot vapour subsequently passes to the cooler end of the tube where it condenses and gives out the latent heat to the tube. The condensed liquid then flows back to the hot end of the tube and the vaporization-condensation cycle repeats. Since the latent heat of vaporization is usually very large, considerable quantities of heat can be transported along the tube and a substantially uniform temperature distribution can be achieved along the heat pipe.

It is known to utilize a heat exchanger comprising separated chambers and a plurality of heat pipes which extend between the chambers, such that heat can become transferred from one chamber to the other. In this respect, by passing a heated fluid through one chamber, the heat pipes can transfer the heat absorbed from the heated fluid to the other chamber wherein a cooled fluid may pass to subsequently absorb the heat from the heat pipes.

However, when passing a heated or cooled fluid through the respective chamber, the fluid is found to travel from an inlet to an outlet of the respective chamber along the path of least resistance, which is typically along the path comprising a low density of heat pipes, namely the periphery of the chamber. Accordingly, it can be difficult to obtain an efficient transfer of heat between a fluid and a heat pipe as it passes from the inlet to the outlet of the respective chamber. We have now devised an improved heat exchanger which alleviates the above problem.

In accordance with the present invention, there is provided a heat exchanger for cooling a gas from a first temperature to a second temperature, the exchanger comprising a first heat exchanging chamber, a second heat exchanging chamber and an array of heat pipes which are arranged to extend from within the first heat exchanging chamber to within the second heat exchanging chamber;

the first heat exchanging chamber comprising an inlet for receiving a coolant into the chamber and an outlet through which the coolant can exit the first chamber, the coolant being arranged to pass over the portion of the heat pipes which extend within the first chamber;

the second heat exchanging chamber comprising an inlet for receiving the gas at a first temperature into the chamber and an outlet through which the gas can exit the second chamber at a second temperature, the gas being arranged to pass over the portion of the heat pipes which extend within the second chamber;

wherein the first and second chambers further comprise at least one baffle which are arranged to deflect the flow coolant and the gas respectively, as the coolant and the gas pass from the inlet to the outlet of the respective chamber. The baffles ensure that the coolant and the gas pass over the heat pipes and thus provide for an efficient exchange of heat between the coolant and the gas, and the heat pipes, rather than passing from the inlet to the outlet of the respective chamber around a peripheral position within the respective chamber without encountering the heat pipes. Preferably, the at least one baffle within the first chamber extends from a wall of the first chamber to a position disposed within the first chamber.

Preferably, the at least one baffle within the second chamber extends from a wall of the second chamber to a position disposed within the second chamber.

Preferably, the first and second chamber comprise a plurality of baffles.

The plurality of baffles preferably extend in a substantially parallel configuration. Preferably, the baffles separately extend to different positions within the respective chamber.

The coolant and the gas preferably pass from the inlet to the outlet of the respective chamber in a direction which is substantially transverse to a longitudinal axis of the heat pipes. The at least one or each baffle preferably extends along the length of the respective chamber. An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1 a is a side view of a heat exchanger according to a first embodiment of the present invention;

Figure 1 b is a plan view of the heat exchanger illustrated in figure 1 ;

Figure 1 c is front view of the heat exchanger illustrated in figure 1 ; Figure 2 is a longitudinal sectional view of the heat exchanger illustrated in figure 1 a;

Figure 3 is a transverse sectional view of the first chamber of the heat exchanger illustrated in figure 1 a; Figure 4 is a transverse sectional view of the second chamber of a heat exchanger illustrated in figure 1 a; and,

Figure 5a is a longitudinal sectional view of a heat exchanger according to a second embodiment of the present invention;

Figure 5b is a transverse sectional view of the first chamber of the heat exchanger illustrated in figure 5a; and,

Figure 5c is a transverse sectional view of the second chamber of the heat exchanger illustrated in figure 5a.

Referring to the figure 1 of the drawings, there is illustrated a heat exchanger 10 according to a first embodiment of the present invention. The heat exchanger 10 comprises a first heat exchanging chamber 1 1 and a second heat exchanging chamber 12. Each chamber 1 1 , 12 comprises a housing 13, 14, which are mounted one on top of the other such that a longitudinal axis of the first chamber 1 1 extends in a substantially collinear relationship with a longitudinal axis of the second chamber 12 and thus the heat exchanger 10.

The first chamber 1 1 of the heat exchanger 10 is disposed above the second chamber 12 and comprises an inlet 15 and an outlet 16 which are disposed within an upper end wall 17 of the housing 13, and which are arranged to enable a coolant such as water, to pass into and out from the chamber 1 1 , respectively. The lower region of the first chamber is secured to a separation plate 18, which separates the first chamber 1 1 from the second chamber 12 and which comprises a plurality of apertures 19 disposed therein, in a substantially hexagonal arrangement disposed around a central portion thereof. The second chamber 12 is secured to the underside of the separation plate 18 and thus the first chamber 1 1 , and comprises an inlet 20 and an outlet 21 disposed in a side wall of the housing 14, at substantially diametrically opposed positions of the chamber 12, such that a gas to be cooled, for example can pass into and out from the chamber 12.

The heat exchanger 10 further comprises a plurality of substantially linear heat pipes 22 which extend from within the first chamber 1 1 , through the array of apertures 19 disposed within the plate 18, and terminate in the second chamber 12 so as to enable heat to be transferred between the chambers 1 1 , 12. The heat pipes 22 are supported within the heat exchanger 10 by the separation plate 18 by a series of collars 23 which separately extend within each of the apertures 19 and which further serve to seal the heat pipes 22 to the separation plate 18 such that the interior of the first and second chambers 1 1 , 12 remain isolated from each other.

The heat pipes 22 are further coupled at a lower longitudinal end thereof to a support plate 24 which is coupled to, but spaced from a lower end wall 25 of the second chamber 12. The support plate 24 serves to minimize any flexing of the heat pipes 22 under force of the gas flow between the inlet 20 and the outlet 21 of the second chamber 12. The upper longitudinal ends of the heat pipes 22 are spaced from the upper end wall 17 of the first chamber 1 1 such that the heat pipes 22 are free to expand and contract and thus relieve any thermal stresses which would otherwise develop during use of the heat exchanger 10.

Referring to figure 3 of the drawings, the first chamber 1 1 further comprises a plurality of baffles 26, which extend along the length of the first chamber 1 1 between the separation plate 18 and the upper wall 17 thereof, and which extend from the housing 13 to a position within the first chamber. The baffles 26 separately comprise a substantially planar wall which are arranged in a substantially parallel configuration and substantially parallel to the longitudinal axis of the first chamber 1 1 . In moving from the inlet 15 to the outlet 16, alternate baffles 26 are arranged to extend from opposite sides of the housing

13 such that the flow of coolant between the inlet 15 and the outlet 16 is caused to make repeated passes back and forth across the heat pipes 22 to ensure that the water extracts the heat from the portion of the heat pipes 22 within the first chamber 1 1 . Referring to figure 4 of the drawings, the second chamber 12 further comprises a plurality of baffles 27 which extend along the length of the second chamber 12 between the lower wall 25 thereof and the separation plate 18 and which extend from the housing

14 to a position within the second chamber 12. The baffles 27 separately comprise a substantially planar wall, which are arranged in a substantially parallel configuration and substantially parallel to the longitudinal axis of the second chamber 12. In contrast with the baffles 26 disposed within the first chamber 1 1 , the baffles 27 disposed within the second chamber 12 extend from the housing 14 and terminate at a position which is proximate to the periphery of the array of heat pipes 22. The baffles 27 are orientated substantially perpendicular to the direction which extends between the inlet 20 and the outlet 21 and the extent to which the baffles 27 extend into the housing 14 decreases in a direction which is from the inlet 20 to a central portion of the second chamber 12 and subsequently increases from the central portion to the outlet 21 . The baffles 27 prevent the gas which passes from the inlet 20 to the outlet 21 from passing close to the periphery of the housing 14 and thus effectively around the heat pipes 22, without passing through the array of heat pipes 22. This similarly ensures that the gas gives up the heat associated therewith to the portion of the heat pipes 22 within the second chamber 12. In use, the heat exchanger 10 according to the above-described embodiment may be used to extract heat from the gas which may be produced from an industrial process, or the air from an air conditioning system (not shown), for example. The hot gas is passed from the inlet 20 to the outlet 21 of the second chamber 12 and a coolant, for example water, is passed from the inlet 15 to the outlet 16 of the first chamber 1 1 . As the hot gas passes across the portion of the heat pipes 22 in the second chamber 12, the heat associated therewith becomes absorbed by the heat pipes 22 and transferred to the portion of the heat pipes 22 within the first chamber 1 1 . The coolant within the first chamber subsequently removes the heat from the heat pipes 22, thereby cooling the heat pipes 22 such that the portion of the heat pipes 22 within the second chamber 12 can cool further hot gas. The baffles 26, 27 in the first and second chamber 1 1 , 12 provide an efficient exchange of heat between that the coolant and hot gas passes, and the heat pipes 22 as the coolant/gas passes from the inlet to the outlet of the respective chamber 1 1 , 12, by ensuring that the coolant/gas pass across the heat pipes 22 of the array, rather than around the array.

Referring to figure 5 of the drawings, there is illustrated a heat exchanger 1 10 according to a second embodiment of the present invention. The heat exchanger 1 10 of the second embodiment is substantially the same as the heat exchanger 10 of the first embodiment and so like features have been referenced using the same numerals but increased by 100.

The heat exchanger 1 10 of the second embodiment however, further comprises support braces 128 which extend within the first chamber 1 1 1 , between the separation plate 1 18 and the upper end wall 1 17 of the housing 1 13 in order to minimise any deformation of the first chamber 1 1 1 due to the pressure of the coolant flowing therein. The support braces 128 are orientated substantially parallel to the heat pipes 122, and are coupled to the separation plate 1 18 and the upper end wall 1 17 of the housing 1 13, to hold the first chamber 1 1 1 in a rigid configuration.

The heat exchanger 1 10 of the second embodiment further comprises removable panels 129 disposed within the walls 1 14 of the second chamber 1 12, so that the panels 129 can be removed to provide access to the heat pipes 122 for cleaning, for example. The panels 129 are illustrated as being removably coupled to the housing wall 1 14 using a plurality of nut and bolt type fasteners; however, it is to be appreciated that other fastening arrangements could be used to provide the same effect. To further facilitate access within the second chamber, access routes are provided into the array of heat pipes 122, for cleaning tools (not shown) and the like. The access routes 130 comprise regions of the array in which rows of heat pipes 122 have been removed, as compared with the array of heat pipes 22 of the heat exchanger 10 of the first embodiment. The access routes 130 extend across the array between the removable panels 114, are enable cleaning tools and the like to reach to the centre of the array and thus the second chamber 1 12.

From the foregoing therefore, it is evident that the heat exchanger of the present invention provides for a more efficient exchange of heat between heat pipes and a gas, and provide for an improved cleaning of the heat pipes when arranged in situ within the chambers of the heat exchanger.

Claims

1 . A heat exchanger for cooling a gas from a first temperature to a second temperature, the exchanger comprising a first heat exchanging chamber, a second heat exchanging chamber and an array of heat pipes which are arranged to extend from within the first heat exchanging chamber to within the second heat exchanging chamber; the first heat exchanging chamber comprising an inlet for receiving a coolant into the chamber and an outlet through which the coolant can exit the first chamber, the coolant being arranged to pass over the portion of the heat pipes which extend within the first chamber;

wherein the first and second chambers further comprise at least one baffle which are arranged to deflect the flow coolant and the gas respectively, as the coolant and the gas pass from the inlet to the outlet of the respective chamber.

2. A heat exchanger according to claim 1 , wherein the at least one baffle within the first chamber extends from a wall of the first chamber to a position disposed within the first chamber.

3. A heat exchanger according to claim 1 or 2, wherein the at least one baffle within the second chamber extends from a wall of the second chamber to a position disposed within the second chamber.

4. A heat exchanger according to any preceding claim, wherein the first and second chamber comprise a plurality of baffles. 5. A heat exchanger according to any preceding claim, wherein the plurality of baffles extend in a substantially parallel configuration.

6. A heat exchanger according to any preceding claim, wherein the baffles separately extend to different positions within the respective chamber.

9. A heat exchanger according to any preceding claim, wherein the coolant and the gas pass from the inlet to the outlet of the respective chamber in a direction which is substantially transverse to a longitudinal axis of the heat pipes.

10. A heat exchanger according to any preceding claim, wherein the at least one or each baffle extends along the length of the respective chamber.