Fluid Flow Analysis of Parallel Flow Heat Exchanger by Varying Inlet Flow Velocities

A heat exchanger is a device that is used to transfer thermal energy (enthalpy) between two or more ?uids, between a solid surface and a ?uid, or between solid particulates and a ?uid, at different temperatures and in thermal contact. In heat exchangers, there are usually no external heat and work interactions. Typical applications involve heating or cooling of a ?uid stream of concern and evaporation or condensation of single-or multi component ?uid streams. In other applications, the objective may be to recover or reject heat, or sterilize, pasteurize, fractionate, distill, concentrate, crystallize, or con?trol a process ?uid. In a few heat exchangers, the ?uids exchanging heat are in direct contact. In most heat exchangers, heat transfer between ?uids takes place through a separating wall or into and out of a wall in a transient manner. In many heat exchangers, the ?uids are separated by a heat transfer surface, and ideally they do not mix or leak. Such exchangers are referred to as direct transfer type, or simply recuperate. In con-trast, exchangers in which there is intermittent heat exchange between the hot and cold ?uids?via thermal energy storage and release through the exchanger surface or matrix? are referred to as indirect transfer type, or simply regenerators. Such exchangers usually have ?uid leakage from one ?uid stream to the other, due to pressure divergences and matrixrotation/valve switching. Common examples of heat exchangers are shell-and-tube exchangers, automobile radiators, condensers, evaporators, air preheaters, and cooling towers.