GB2027531A - Finned heat exchanger element - Google Patents

Abstract

A heat exchange element comprises a hollow tube of heat-conductive material, and a helical coil of heat- conductive wire disposed in a helical path around the outside of the tube and bonded thereto. The turns of the coil are inclined at an angle alpha to the longitudinal axis of the tube. The angle alpha may either be constant or increase radially outwardly in each turn. <IMAGE>

Description

SPECIFICATION Heat Exchanger Element This invention relates to a heat exchanger element.

A known form of heat exchanger element is shown in Figures 1A and 1 B of the attached drawings.

Figure 1A is a side elevation, and Figure 1 B is an end elevation. The heat exchange element comprises a hollow metal tube 1, to the exterior of which is secured a metal wire 2. The wire 2 is in the form of a continuous helix which is itself helically wound around the exterior of the tube 1. In the cse of the element shown in Figures 1A and 1 B each loop of the wire has a length L extending substantially radially from the tube which is considerably greater than the width W thereof.

In use of the heat exchanger element shown in Figures 1A and 1 B heat exchange takes place between a first fluid flowing through the tube 1 and a second fluid flowing around the outside of the tube and directed substantially at right angles to the axes of the tube. The wire 2 serves to increase very greatly the rate at which heat is transferred between the two fluids, as compared to the rate at which transfer would take place if the wire were not present. It should be noted that the wire 2 is soldered onto the outside of the tube 1 by a binding wire which runs helically inside the loops of wire adjacent the outside surface of the tube.

It has been discovered by the inventor of the present invention that the efficiency of heat transfer depends in a particular way on the spacing s between adjacent sections of the wire coil, and the width wofthewire coil. In partiuclar, it has been found that the heat transfer is at its most efficient for a given pressure drop in the fluid flowing past the exterior of the tube, when wand s are equal to one another. It is an object of the invention to provide a heat transfer element which as improved efficiency for a given pressure drop.

According to the present invention there is provided a heat transfer element comprising a hollow tube of heat-conductive material, and a helical coil of heat conductive wire disposed in a helical path around the outside of the tube and bonded thereto, wherein the turns of the coil are inclined at an acute angle to the longitudinal axis of the tube. An embodiment of a heat exchanger element according to the invention is shown in Figures 2A and 2B of the attached drawings, which are views corresponding to Figures 1A and 1 B.

In will be observed that the turns of the coil are inclined at an acute angle a to the longitudinal axis of the tube. Although this is not entirely apparent in the perspective view of Figure 2A it will be appreciated from Figure 2B that all the turns of the coil are so inclined. In the particular embodiment illustrated the inclination of each turn increases from zero at the region where the turn is bonded to the tube to the illustrated value a at the region of the turn furthest from the tube. An element having this configuration can readily be made by first producing an element of the type shown in Figures 1A and 1B and then twisting the turns of wire through an angle a by appropriate mechanical means.Alternatively, the turns of wire could be so attached to the tube that their angle of inclination to the axis of the tube is substantially constant from top to bottom, this being achieved by bonding the turns of wire to the tube at an angle to the axis of the tube.

It has been found that the tube constructed according to the invention provides a substantially lower pressure drop for a given value of w plus s than is the case with the tube shown in Figures 1A and 1 B. Put another way, the same pressure drop will be achieved using the configurtion according to the invention for a smaller value of w plus s. Thus, one can use a heat exchanger element of the present invention in place of the known form of heat exchanger element either to increase the heat transfer efficiency for a given pressure drop or to reduce the pressure drop for a given value of heat transfer efficiency.

The angle a may have any desired value up to as near as 90" as is permitted by the physical strength imposed by the thickness of the wire and the interference between adjacent turns of the wire.

However, it is preferred that the value of the angle a should be at least 45".

1. A heat transfer element comprising a hollow tube of heat-conductive material, and a helical coil of heat conductive wire disposed in a helical path around the outside of the tube and bonded thereto, wherein the turns of the coil are inclined at an acute angle to the longitudinal axis of the tube.

2. An element as claimed in claim 1, wherein the said acute angle is at least 45D for at least part of each turn.

3. An element as claimed in claim 1 or 2, wherein the said acute angle increases radially outwardly in each turn.

4. An element as claimed in claim 1 or 2, wherein the said acute angle is constant radially outwardly in each turn.

5. An element as claimed in any preceding claim, wherein the axial spacing between adjacent sections of the coil is substantially equal to the axial width of each section.

6. A heat transfer element substantially as herein described with reference to Figures 2A and 2B of the accompanying drawings.

New claims or amendments to claims filed on 23.10.79 Superseded claims 1 to 6 New or amended claims: 1. A heat transfer element comprising a hollow tube of heat-conductive material, and a helical coil of heat-conductive wire disposed in a helical path around the outside of the tube and bonded thereto, wherein the turns of the coil are inclined at an acute angle to the longitudinal axis of the tube and are at an angle which differs from 90" with respect to the said helical path.

2. An element as claimed in claim 1, wherein the first mentioned angle is at least 450 for at least part of

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

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Heat Exchanger Element This invention relates to a heat exchanger element. A known form of heat exchanger element is shown in Figures 1A and 1 B of the attached drawings. Figure 1A is a side elevation, and Figure 1 B is an end elevation. The heat exchange element comprises a hollow metal tube 1, to the exterior of which is secured a metal wire 2. The wire 2 is in the form of a continuous helix which is itself helically wound around the exterior of the tube 1. In the cse of the element shown in Figures 1A and 1 B each loop of the wire has a length L extending substantially radially from the tube which is considerably greater than the width W thereof. In use of the heat exchanger element shown in Figures 1A and 1 B heat exchange takes place between a first fluid flowing through the tube 1 and a second fluid flowing around the outside of the tube and directed substantially at right angles to the axes of the tube. The wire 2 serves to increase very greatly the rate at which heat is transferred between the two fluids, as compared to the rate at which transfer would take place if the wire were not present. It should be noted that the wire 2 is soldered onto the outside of the tube 1 by a binding wire which runs helically inside the loops of wire adjacent the outside surface of the tube. It has been discovered by the inventor of the present invention that the efficiency of heat transfer depends in a particular way on the spacing s between adjacent sections of the wire coil, and the width wofthewire coil. In partiuclar, it has been found that the heat transfer is at its most efficient for a given pressure drop in the fluid flowing past the exterior of the tube, when wand s are equal to one another. It is an object of the invention to provide a heat transfer element which as improved efficiency for a given pressure drop. According to the present invention there is provided a heat transfer element comprising a hollow tube of heat-conductive material, and a helical coil of heat conductive wire disposed in a helical path around the outside of the tube and bonded thereto, wherein the turns of the coil are inclined at an acute angle to the longitudinal axis of the tube. An embodiment of a heat exchanger element according to the invention is shown in Figures 2A and 2B of the attached drawings, which are views corresponding to Figures 1A and 1 B. In will be observed that the turns of the coil are inclined at an acute angle a to the longitudinal axis of the tube. Although this is not entirely apparent in the perspective view of Figure 2A it will be appreciated from Figure 2B that all the turns of the coil are so inclined. In the particular embodiment illustrated the inclination of each turn increases from zero at the region where the turn is bonded to the tube to the illustrated value a at the region of the turn furthest from the tube. An element having this configuration can readily be made by first producing an element of the type shown in Figures 1A and 1B and then twisting the turns of wire through an angle a by appropriate mechanical means.Alternatively, the turns of wire could be so attached to the tube that their angle of inclination to the axis of the tube is substantially constant from top to bottom, this being achieved by bonding the turns of wire to the tube at an angle to the axis of the tube. It has been found that the tube constructed according to the invention provides a substantially lower pressure drop for a given value of w plus s than is the case with the tube shown in Figures 1A and 1 B. Put another way, the same pressure drop will be achieved using the configurtion according to the invention for a smaller value of w plus s. Thus, one can use a heat exchanger element of the present invention in place of the known form of heat exchanger element either to increase the heat transfer efficiency for a given pressure drop or to reduce the pressure drop for a given value of heat transfer efficiency. The angle a may have any desired value up to as near as 90" as is permitted by the physical strength imposed by the thickness of the wire and the interference between adjacent turns of the wire. However, it is preferred that the value of the angle a should be at least 45". CLAIMS

1. A heat transfer element comprising a hollow tube of heat-conductive material, and a helical coil of heat conductive wire disposed in a helical path around the outside of the tube and bonded thereto, wherein the turns of the coil are inclined at an acute angle to the longitudinal axis of the tube.

2. An element as claimed in claim 1, wherein the said acute angle is at least 45D for at least part of each turn.

3. An element as claimed in claim 1 or 2, wherein the said acute angle increases radially outwardly in each turn.

4. An element as claimed in claim 1 or 2, wherein the said acute angle is constant radially outwardly in each turn.

5. An element as claimed in any preceding claim, wherein the axial spacing between adjacent sections of the coil is substantially equal to the axial width of each section.

6. A heat transfer element substantially as herein described with reference to Figures 2A and 2B of the accompanying drawings.

6. A heat transfer element substantially as herein described with reference to Figures 2A and 2B of the accompanying drawings.

New claims or amendments to claims filed on 23.10.79 Superseded claims 1 to 6 New or amended claims:

1. A heat transfer element comprising a hollow tube of heat-conductive material, and a helical coil of heat-conductive wire disposed in a helical path around the outside of the tube and bonded thereto, wherein the turns of the coil are inclined at an acute angle to the longitudinal axis of the tube and are at an angle which differs from 90" with respect to the said helical path.

2. An element as claimed in claim 1, wherein the first mentioned angle is at least 450 for at least part of each turn.

3. An element as claimed in claim 1 or 2, wherein the first mentioned angle increases radially outwardly in each turn.

4. An element as claimed in claim 1 or 2, wherein the first mentioned angle is constant radially outwardly in each turn.

5. An element as claimed in any preceding claim, wherein the axial spacing between adjacent sections of the coil is substantially equal to the axial width of each section.