GB2628113A

GB2628113A - Heat exchange pipes use bobbins to enhance external heat transfer

Info

Publication number: GB2628113A
Application number: GB2303683.3A
Authority: GB
Inventors: Garvey Seamus; Simpson Michael; Julian Harris Paul; Andrews Matthew
Original assignee: Cheesecake Energy Ltd
Current assignee: Cheesecake Energy Ltd
Priority date: 2023-03-13
Filing date: 2023-03-13
Publication date: 2024-09-18
Also published as: GB202303683D0

Abstract

A heat exchanger device comprising one or more pipes 1 suitable for containing a pressurised fluid and arranged to exchange heat between the pressurised fluid in the pipe and a surrounding external medium such as a further fluid or a thermal store. The one or more pipes are fitted with external components 2, 3 that are used to facilitate heat exchange between the pressurised fluid and the external medium, and may take the form of bobbins used to hold a spooled wire or thread. The pipe(s) is/are arranged to engage with the external components through plastic yielding and radial expansion of the pipe(s) caused by the pressurised fluid flowing through the pipe(s). The heat exchanger is arranged to exchange heat with a thermal store, and the thermal store may be in the form of a solid mass or a packed bed of granular material.

Description

Heat Exchange Pipes use Bobbins to Enhance External Heat Transfer Field of the invention: This invention relates to heat exchangers that may or may not have integral thermal storage wherein at least one fluid is under significant pressure.

Background:

Heat exchangers come in different formats but one common format used where at least one stream of fluid must be retained at high pressure involves containing that pressurised fluid within pipes and having the heat transfer occur across the walls of the pipes. This invention relates specifically to such cases.

The heat transfer may be from the pressurised fluid outward through the pipe walls or it may be inward through the pipe walls into the pressurised fluid. In many cases, the same unit serves for providing heat transfer in both directions. This is especially the case in the context of energy storage. Energy storage is the primary motivation for the present invention although the same central concept can clearly serve other applications also. For clarity and brevity of presentation in most of the remainder of this description, we refer to heat transfer only in the inward direction towards the pressurised fluid. It should be understood that the converse heat exchange is also enhanced by this invention and the scope of relevance for this invention certainly includes instances where heat flows outward from the pressurised fluid during some (or all) periods of operation of the device.

External to the pipes, there may be a solid medium acting as a thermal store or there may simply be a lower-pressure fluid circulating outside of the pipes that could be either a gas or a liquid. The present invention was conceived in the context where there would be a solid medium acting as a thermal store. For this invention, the pressurised fluid passing within the pipes may also be either a gas or a liquid or it may even change phase between gas and liquid within the pipes as a result of the heat transfer.

In the design of such arrangements, account is taken of how to enhance heat transfer between the inner walls of the pipe and the pressurised fluid, how to pass heat effectively through the pipe walls themselves and finally how to exchange heat between the medium external to the pipe outer walls and those outer walls. This invention pertains mainly to the latter point.

Various arrangements are known whereby good heat transfer between the inner pipe surfaces and the pressurised fluid can be encouraged. The use of roughened inner surfaces and the deployment of internally-fitted turbulators are well-known to those skilled in the art. Most, and perhaps all, of such strategies for enhancing heat transfer between the inner pipe surfaces and the pressurised fluid can be implemented also in conjunction with the present invention.

Heat transfer between the outer wall of the pipes and the inner wall is very often of low concern since the thermal resistance associated with this heat transfer is normally comparatively small. This happens naturally because the pipe walls are normally metal for the purposes of having the strength to contain the pressurised fluid without rupturing. Metals generally have relatively high values of thermal conductivity compared with other materials as a consequence of having free-electrons -the same phenomenon that causes them to be electrically conductive. This fact pertains to the present invention just as it does to many other arrangements where heat must be exchanged with a pressurised fluid.

The present invention relates primarily to enhancing the transfer of heat between the outer wall of the pipes and the external medium -where that medium may be a stationary solid medium or it may be another fluid. There are already numerous concepts in use for enhancing heat transfer between the outer walls of pipes containing pressurised fluid and an external medium. In some cases, discrete pins are welded on to the outer surface of the pipe to increase surface area and (when there is an external fluid) to promote the kind of turbulence that assists heat transfer. In other cases, discrete annular fins are attached to the outside of the pipe for the same purposes. In other cases still, a continuous helical fin is attached to the outside of the pipe. The present concept falls within the set of solutions that involve being the outside wall of the pipe into close thermal contact with some additional metalwork.

A summary of this invention.

This invention is founded on the recognition that in pipes containing a pressurised fluid, the average hoop stress in the pipe wall is always larger than the average axial stress. For thin-walled pipes, the hoop stresses carried within the pipe walls are approximately twice as large as the axial stresses and both types of stress vary only slightly through the wall thickness. For thicker-walled pipes that have not been caused to yield, the hoop stress is higher at the inside than at the outside and the same applies to axial stresses but if the pressure within the pipe becomes sufficiently high that plastic yielding begins to occur, that yielding always begins in the hoop direction.

In shorter form, a uniform pipe made from ductile material that is subjected to an internal pressure high enough to initiate yielding in the pipe will always undergo radial growth before it experiences axial growth. The core concept of this invention is that this radial growth can bring the outer wall of the pipe into close thermal contact with the inner cylindrical wall of one or more other components encircling the pipe.

The invention, in summary, is that components can be manufactured separately from the main pipes serving to implement heat exchange with a pressurised fluid, slid loosely over these main pipes and then they will automatically come into close thermal contact when the pipes yield slightly in the plane normal to their axis. The external components then provide the reinforcement necessary to ensure that no further yielding happens in this plane.

In one embodiment foreseen, these external components are shaped like "bobbins" -such as might be used to hold long rolls of thread, cable or wire.

Description of the drawings.

Only one Figure is provided. Figure 1 shows a pipe (1) that can contain a pressurised fluid passing within it. This figure depicts an axi-symmetric arrangement -at least locally to the centreline. Further away from the centreline, the axi-symmetry does not obtain.

External components (2) that resemble bobbins surround the pipe (1) over most of its active length. These external components sandwich plates (3) that can collect (or distribute) heat over a relatively large distance from the centre of the pipe (1).

Claims

Heat Exchange Pipes use Bobbins to Enhance External Heat Transfer CLAIMS: (1) A device for either supplying heat into a pressurised fluid or drawing heat from a pressurised fluid or both comprises a set of one or more pipes within which said pressurised fluid passes and surrounding said pipe(s) are fitted external components to facilitate the exchange of heat with the external medium where good thermal contact between the outer surface of the pipe(s) and the external components is achieved through plastic yielding of the pipe(s).(2) A device for either supplying heat into a pressurised fluid or drawing heat from a pressurised fluid or both such as that described in claim 1 wherein the external thermal medium is a fluid in which case the device is a heat-exchanger between the pressurised fluid and the external fluid which is at lower pressure (3) A device for either supplying heat into a pressurised fluid or drawing heat from a pressurised fluid or both such as that described in claim 1 wherein the external thermal medium is a solid mass or a packed bed of granular material in which case the device is a combination of a heat-exchanger and a thermal store.