GB2428780A

GB2428780A - Perforated plate heat exchanger

Info

Publication number: GB2428780A
Application number: GB0515407A
Authority: GB
Inventors: John Rhys Jones
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-07-27
Filing date: 2005-07-27
Publication date: 2007-02-07
Also published as: GB0515407D0

Abstract

A perforated plate heat exchanger comprises a plurality of stacked plates 3, 4, and each plate having perforations 2 which overlap with perforations in an adjacent plate 4 whereby a fluid passes though the perforations 2 in the plates 3, 4. The perforations 2 may communicate with manifolds 1, 5 and they may penetrate the edge of the plates 3, 4 permitting fluid to enter at the sides of the plate stack. The plates 3, 4 may be manufactures from metal, plastics or ceramic and may be bonded, welded, or brazed together. A second fluid may pass though alternative perforations (6, fig 2) and absorbs heat given off from the first fluid. The number, size and spacing of perforations 2, (6) may be varied for desired flow distribution. Additional identical plates rotated by one hundred and eighty degrees can be placed on top of the stack so that the plate sequence repeats itself every four plates.

Description

PERFORATED FLAT PLATE HEAT EXCHANGER

The invention relates to the transfer of heat from one fluid to another fluid through a system of solid separating walls commonly referred to as a Heat Exchanger.

A number of design concepts are known, but each has associated disadvantages: One fluid can flow in tubes, surrounded by the other. However, such shell and tube designs suffer a number of shortcomings, for example: The shell can provide a significant manufacturing challenge and tubes become prone to flow- induced fretting as fluid pressure gradients are increased, so that power density is limited.

Plate heat exchangers are an alternative. A stack of corrugated plates are commonly separated and sealed by gaskets. These designs achieve high power density, but the gasket material and the contact between successive plates limits their operating parameters.

Some designs are know which avoid the need for gaskets by stacking successive flat plates, but it is then necessary to construct passages in which the coolant flows. Etching passages in the surface of the plates is possible, but this limits the dimensions of the channels formed, making them vulnerable to fouling.

The object of this invention is to provide a novel and improved solution to the problem of creating a flow passage within the stack of flat plates that constitutes a plate heat exchanger. The invention allows designers to overcome the constraints of their existing designs, for example limits of power density, flow rate, or ease of manufacture.

This Invention provides a series of perforating the plates held together in a stack so as to prevent fluid leaking between the plates. The seal can be achieved by brazing, welding, or externally applied pressure.

The holes in successive plates overlap so that the arrangement of plates creates complex flow passages.

Fluid flowing within the bounds of each perforation exchanges heat with the edges of the perforation, but mostly with the surfaces of the adjacent plates. Since the fluid is exposed only to a relatively short length of continuous surface, the development of a thermal boundary layer within the fluid adjacent to the surfaces is limited and high rates of heat transfer from the fluid are achieved. Vorticity induced by the regular changes in flow direction also aids heat transfer.

The perforations within the plates can readily be manufactured by stamping, laser cutting or other techniques suitable for mass production at a reasonable cost.

The ability of the system to withstand a pressure difference between fluids can be optimised by varying the size and spacing of holes or the thickness of plates, giving the designer three degrees of freedom.

The size, number and spacing of perforations can be varied to provide the desired distribution of flow area. This allows designs to compensate for changes in fluid density and to enhance flow dynamic stability.

An embodiment of the invention is now described with reference to the accompanying drawings in which: FIGURE 1 shows a plan view of two plates with manifolds and perforated passageways visible; FIGURE 2 shows a section through a passageway including a manifold.

As shown in FIGURE 1, each successive plate obscures and closes entirely the passageways containing one fluid (excepting the manifolds, which perforate all plates). Additionally each plate only partly closes the part-complete alternative flow passage and itself provides the remainder of the passages necessary to link the perforations and provide a continuous path for the second fluid between appropriate manifolds.

As shown in FIGURE 2, fluid enters and leaves the heat exchanger through manifolds 1 that penetrate all of the perforated plates from which the stack is constructed.

Typically, one in every four plates contains perforations 2 that penetrate the edge of a particular manifold. As shown in FIGURE 1, fluid can enter the plate through these perforations 2 and flows through the passageways constructed in this plate 3 and the adjacent plate 4. Finally, the flow leaves through a different manifold at a remote part of the plate 5. In the process of flowing through the passage thus formed, one fluid gives up heat to a second fluid travelling through alternative perforations. (, In an alternative design (not illustrated) the perforations penetrate the plate edge and permit fluid to enter the heat exchanger from the adjacent environment.

The stacking of the plates can benefit from symmetry should it be present. An additional identical plate can be placed on the top of the stack shown in FIGURE 1 if rotated one hundred and eighty degrees in the plane of the paper relative to the top plate shown. This plate can then be covered in a similar manor to that shown in FIGURE 1. The sequence repeats itself every four plates.

Claims

1. A heat exchanger constructed of perforated plates with perforations suitably arranged to overlap and provide a passage for fluid.

2. A heat exchanger claimed in 1 where perforations form manifolds for fluid to enter the heat exchanger.

3. A heat exchanger claimed in 1 where perforations penetrate the edge of the plates and permit fluid to enter from the immediate neighbourhood.

4. A heat exchanger claimed in I manufactured in metal, plastic or ceramic material.

5. A heat exchanger claimed in 1 where plates are welded, brazed, or bonded together by a

suitable process.

6. A heat exchanger claimed in I where plates are held together by the application of external pressure.