| In this thesis, an experimental investigation of fluid flow and heat transfer through open cell porous wire mesh and laser-sintered heat exchangers is presented. The thesis consists of two main sections that describe how to create a compact heat exchanger that uses open-cell porous structures.;In the first part of the thesis a new method of building compact heat exchangers using direct metal laser sintering (DMLS), a technology which enables heat exchangers with a predetermined, fully controlled internal geometry to be built was investigated. Laser-sintering was used to fabricate stainless steel heat exchanger channels filled with struts arranged to form either cubic, round-strut tetradecahedral or thin-strut tetradecahedral cells. The objective was to demonstrate that the effect of adding internal struts is not simply to increase surface area, but that cell geometry has a significant effect on both heat transfer and fluid flow. This section also describes the importance of the connection between the porous structures, which is used to improve the performance of the heat exchanger, to the main body of the heat exchanger. It was possible to design internal geometries that maximize heat transfer while minimizing weight and frictional losses.;In the second part of the thesis, a simple method of increasing the heat transfer surface area has been developed by using a twin wire-arc thermal spray system to generate a dense, high strength coating that bonds porous structures, like wire mesh and perforated sheets, to the plain tube heat exchanger's outside surfaces. The porous structure and the main body of the heat exchanger must be well bonded together to minimize thermal resistance. The extended surfaces of the wire mesh and perforated sheet enhanced the heat transfer performance of the tube heat exchangers. Finding the right balance between pore density and number of screens of the porous structures is crucial for maximizing the heat transfer performance of the heat exchangers. |
