Experimental Investigation of the performance of a five layered gas-to-gas heat exchanger with a porous medium”,

Abstract

The process of heat exchange between two fluids that are at different temperatures occurs in many engineering applications. The device used to implement this exchange is termed a heat exchanger. In some cases, a solid wall may separate the fluids and prevent them from mixing. In other designs, the fluids may be in direct contact with each other. In the most efficient heat exchangers, the surface area of the wall between the fluids is maximized while simultaneously minimizing the fluid flow resistance. Fins or corrugations are sometimes used with the wall in order to increase the surface area and to induce turbulence. Heat exchangers are essential elements in a wide range of systems, including the human body, automobiles, computers, power plants, and comfort heating/cooling equipment. Specific applications may be found in space heating and air-conditioning, power production, waste heat recovery, and chemical processing. Heat Exchangers are used in a wide variety of specific applications as in the process, power, industries space heating and airconditioning, refrigeration, cryogenics, waste heat recovery, and manufacturing and chemical processing. In the power industry, various kinds of fossil boilers, nuclear steam generators, steam condensers, regenerators, and cooling towers are used. In process industry, two-phase flow heat exchangers are used for vaporizing, condensing, freezing in crystallization, and as fluidized beds with catalytic reactions. The air conditioning and refrigeration industries need large amount of condensers and evaporators. Heat Exchangers are typically classified according to flow arrangement and type of construction. 2 There are three primary flow arrangements with heat exchangers: counter-flow, parallel-flow, and cross-flow. In the counter-flow exchanger, the fluids enter the exchanger from opposite sides. This is the most efficient design because it transfers the greatest amount of heat. In the parallel-flow version, the fluids come in from the same end and move parallel to each other as they flow to the other side. The cross-flow heat exchanger moves the fluids in a perpendicular fashion. There are also four different designs of heat exchangers: shell and tube, plate, regenerative, and intermediate fluid or solid. The most typical type is the shell and tube design. This has multiple finned tubes. One of the fluids runs through the tubes while the other fluid runs over them, causing it to be heated or cooled. In the plate heat exchanger, the fluid flows through baffles. This causes the fluids to be separated by plates with a large surface area. This type of exchanger is typically more efficient than the shell and tube design. The regenerative heat exchanger takes advantage of the heat from a specific process in order to heat the fluid used in the same process. These can be made with the shell and tube design or the plate design. The intermediate fluid or solid heat exchanger uses the fluids or solids within it to hold heat and move it to the other side in order to be released. This method is commonly used to cool gases while removing impurities at the same time.