GB1600404A - Rotary heat exchangers - Google Patents

Description

(54) IMPROVEMENTS RELATING TO ROTARY HEAT EXCHANGERS (71) We, CURWEN & NEWBERY LI MITED, of Westcroft House, Alfred Street, Westbury, Wiltshire, a British Company, do hereby declare the invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement: This invention relates to heat exchangers of the type incorporating one or more "heat pipes". For present purposes a "heat pipe" may be defined as a closed tube containing a fluid whose boiling point is so selected and related to the pressure and temperature conditions experienced in the tube that the fluid will condense into the liquid state at the relatively cold temperatures at one end of the tube, and will evaporate at the higher temperatures experienced at the other end of the tube.There may be a return flow of liquid condensate along the length of the tube, which may be encouraged by gravity, or by wick or capillary action or by vibration of the tube. In the result the movement of liquid combined with the condensation and evaporation effects create an effective means of heat transfer from one end to the other of the tube.

To provide transfer of heat from one zone to another a bank of such heat pipes may be provided, and the same transfer system can be applied to a heat regenerator for transferring heat between two moving fluid systems. The present invention provides an improved heat exchanger or regenerator operating on this basic principle.

Broadly stated the invention consists in a heat exchanger for exchanging heat between two fluid systems, comprising a rotary unit disposed in a casing, each fluid system having an aligned inlet and an outlet to the casing, and including an array of a plurality of heat pipes arranged around an axis, each pipe containing a thermal transfer fluid, and means for rotating the unit about the ais with the respective two end sections of each pipe of the unit spaced along the axis and exposed respectively one to each of the two fluid systems, that dimension to each inlet which extends orthogonal to the axis of rotation and transverse to the axis of the inlet being substantially greater than half the transverse dimension of the array.

Preferably the apparatus includes a rotary drive means for turning the unit at a controlled, and preferably variable speed, about its axis, and there may be at least one rotary fluid seal surrounding the unit between the ends thereof to prevent or limit movement of fluid between the two streams.

The invention is to be distinguished from a rotary regenerator of the type including a large mass of fluid permeable thermal exchange material, which is arranged to rotate about an axis parallel with and between a pair of fluid ducts. Particular sections of the mass thus travel in sequence across first one duct and then the other, and in this way physically transfer or convey heat from the fluid in one duct to the other, without intermingling of the fluids. In the present invention there is no such physical or bodily movement of the unit between one duct and the other, the transfer of heat being achieved along the length of each heat pipe.

The invention may be performed in various ways and specific embodiments will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 is a diagrammatic perspective view of a rotary heat pipe regenerator unit according to the invention, Figure 2 is a diagrammatic side elevation partly in section illustrating the unit in position across two gas ducts, Figure 3 is an end view of the construction of Figure 2, Figure 4 is a diagrammatic side elevation of an alternative embodiment of a rotary heat pipe regenerator unit, and Figure 5 is an end view of the unit of Figure 3.

In this example the rotary unit comprises an array of large number of closed individual heat tubes or pipes 10, mounted parallel with one another as a unit for rotation on a common shaft 11. For this purpose the tubes may be mounted for example in a number of rings or plates 12, 13 and in particular it is desirable that there should be at least four spaced parallel rings or plates 12 which also act as sealing plates as will be described below. In addition there may be further rings or plates 13 acting as heat exchange fins.

Each of the heat tubes 10 is a completely closed self-contained unit, and is filled with a suitable liquid or vapour selected to have a boiling point under the pressure and temperature conditions, which will cause condensation at the cold end and evaporation at the hot end. An internal wick or capillary element or other transfer device encourages flow of the liquid along the length of each tube, and to encourage these movements the unit may be mounted with the axis of the unit positioned on an incline or vertically so that gravity will encourage return flow of the liquid condensate. In this example the rotor unit is mounted within a rectangular case 20 which has main gas ducts 21, 22, extending across the case at opposite ends.

The diameter of the ducts is substantially greater than the radius of the array of pipes and may, for example, be at least as great as the diameter of that array. The relatively hot and cold gas flows pass in countercurrent along these ducts and in doing so pass over the heat tubes and transmit or receive heat accordingly. The case 20 is provided with internal annular seals as indicated at 23 to co-operate with the rings or flanges 12 and so prevent the gas excaping from the casing or passing across from one duct to the other. In addition the casing 20 is provided with internal wiper seals 24 which are disposed to engage or lie in close contact with external pipes of the rotary unit during rotation of the unit, and thus prevent the gas flowing around the unit without passing over and around the individual heat tubes.

In addition the casing 20 may be provided with trays 25 to remove any liquid condensate which collects in the casing, and removable inspection covers 26 may be fitted to allow for inspection, repair or replacement, or for in-situ cleaning of the heat tube unit, preferably by high pressure water, steam or compressed air jets.

The rotary unit is mounted for rotation on the shaft 11 which is carried in bearings 27 at opposite ends of the casing. One end of the shaft is provided with a pulley or gear 28 by which the unit can be driven at a controlled speed, preferably by a variable speed electric motor or through a variable speed gear.

By varying the rotational speed the capacity of the unit can be changed to suit requirements.

In the examples described the several individual heat pipes are mounted in parallel in apertures in the plates or fins 12 and 13. As an alternative each heat pipe may be provided with its own individual series or spiral of cooling fins.

In the further example illustrated in Figures 4 and 5, the rotary unit comprises a central driven shaft 11 similar to that of the previous examples, and carrying a pair of end plates or frames 12, which support a multiple bank of heat tubes 30. In this case, however, each heat tube is provided with its own individual circular heat transfer fins 31 which are not in direct contact with other heat tubes in the bank. For clarity control central rings or flanges 12 have been omitted from Figures 4 and 5 although in practice they would normally be present.

WHAT WE CLAIM IS: 1. A heat exchanger for exchanging heat between two fluid systems, comprising a rotary unit disposed in a casing, each fluid system having an aligned inlet and an outlet to the casing, and including an array of a plurality of heat pipes arranged around an axis, each pipe containing a thermal transfer fluid, and means for rotating the unit about the axis with the respective two end sections of each pipe of the unit spaced along the axis and exposed respectively one to each of the two fluid systems, that dimensions of each inlet which extends orthogonal to the axis of rotation and transverse to the axis of the inlet being substantially greater than half the transverse dimension of the array.

2. Apparatus according to claim 1, including a rotary drive means for turning the unit, at a controlled speed about its axis.

3. Apparatus according to claim 2, in which the drive means is adjustable to provide variable speeds.

4. Apparatus according to claim 1 or claim 2 or claim 3, including at least one fluid seal surrounding the unit between the ends thereof to prevent or limit movement of fluid between the two streams, whilst allowing rotation of the rotary unit.

5. Apparatus according to any of the preceding claims, including a pair of wiper seals on diametrically opposite sides of the rotary unit, in way of each fluid system, to prevent or minimise escape of fluid around the edges of the unit.

6. Apparatus according to any of the preceding claims in which the or each heat pipe is provided with external heat exchange fins at both ends.

7. Apparatus according to any of the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. heat pipe regenerator unit, and Figure 5 is an end view of the unit of Figure 3. In this example the rotary unit comprises an array of large number of closed individual heat tubes or pipes 10, mounted parallel with one another as a unit for rotation on a common shaft 11. For this purpose the tubes may be mounted for example in a number of rings or plates 12, 13 and in particular it is desirable that there should be at least four spaced parallel rings or plates 12 which also act as sealing plates as will be described below. In addition there may be further rings or plates 13 acting as heat exchange fins. Each of the heat tubes 10 is a completely closed self-contained unit, and is filled with a suitable liquid or vapour selected to have a boiling point under the pressure and temperature conditions, which will cause condensation at the cold end and evaporation at the hot end. An internal wick or capillary element or other transfer device encourages flow of the liquid along the length of each tube, and to encourage these movements the unit may be mounted with the axis of the unit positioned on an incline or vertically so that gravity will encourage return flow of the liquid condensate. In this example the rotor unit is mounted within a rectangular case 20 which has main gas ducts 21, 22, extending across the case at opposite ends. The diameter of the ducts is substantially greater than the radius of the array of pipes and may, for example, be at least as great as the diameter of that array. The relatively hot and cold gas flows pass in countercurrent along these ducts and in doing so pass over the heat tubes and transmit or receive heat accordingly. The case 20 is provided with internal annular seals as indicated at 23 to co-operate with the rings or flanges 12 and so prevent the gas excaping from the casing or passing across from one duct to the other. In addition the casing 20 is provided with internal wiper seals 24 which are disposed to engage or lie in close contact with external pipes of the rotary unit during rotation of the unit, and thus prevent the gas flowing around the unit without passing over and around the individual heat tubes. In addition the casing 20 may be provided with trays 25 to remove any liquid condensate which collects in the casing, and removable inspection covers 26 may be fitted to allow for inspection, repair or replacement, or for in-situ cleaning of the heat tube unit, preferably by high pressure water, steam or compressed air jets. The rotary unit is mounted for rotation on the shaft 11 which is carried in bearings 27 at opposite ends of the casing. One end of the shaft is provided with a pulley or gear 28 by which the unit can be driven at a controlled speed, preferably by a variable speed electric motor or through a variable speed gear. By varying the rotational speed the capacity of the unit can be changed to suit requirements. In the examples described the several individual heat pipes are mounted in parallel in apertures in the plates or fins 12 and 13. As an alternative each heat pipe may be provided with its own individual series or spiral of cooling fins. In the further example illustrated in Figures 4 and 5, the rotary unit comprises a central driven shaft 11 similar to that of the previous examples, and carrying a pair of end plates or frames 12, which support a multiple bank of heat tubes 30. In this case, however, each heat tube is provided with its own individual circular heat transfer fins 31 which are not in direct contact with other heat tubes in the bank. For clarity control central rings or flanges 12 have been omitted from Figures 4 and 5 although in practice they would normally be present. WHAT WE CLAIM IS:

1. A heat exchanger for exchanging heat between two fluid systems, comprising a rotary unit disposed in a casing, each fluid system having an aligned inlet and an outlet to the casing, and including an array of a plurality of heat pipes arranged around an axis, each pipe containing a thermal transfer fluid, and means for rotating the unit about the axis with the respective two end sections of each pipe of the unit spaced along the axis and exposed respectively one to each of the two fluid systems, that dimensions of each inlet which extends orthogonal to the axis of rotation and transverse to the axis of the inlet being substantially greater than half the transverse dimension of the array.

2. Apparatus according to claim 1, including a rotary drive means for turning the unit, at a controlled speed about its axis.

3. Apparatus according to claim 2, in which the drive means is adjustable to provide variable speeds.

4. Apparatus according to claim 1 or claim 2 or claim 3, including at least one fluid seal surrounding the unit between the ends thereof to prevent or limit movement of fluid between the two streams, whilst allowing rotation of the rotary unit.

5. Apparatus according to any of the preceding claims, including a pair of wiper seals on diametrically opposite sides of the rotary unit, in way of each fluid system, to prevent or minimise escape of fluid around the edges of the unit.

6. Apparatus according to any of the preceding claims in which the or each heat pipe is provided with external heat exchange fins at both ends.

7. Apparatus according to any of the

preceding claims in which the rotary unit includes a number of spaced generally radial rings or plates which act as supports for the heat pipes and/or heat exchange plates.

8. A heat exchanger substantially as described with reference to the accompanying drawings.