A heat exchangeris a device that is used to transfer thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid particulates and a fluid, at different temperatures and in thermal contact. An easytounderstand introduction to how a heat exchanger passes heat. In contrast to the parallel flow heat exchanger, the counter flow heat exchanger can have the hottest coldfluid temperature greater than the coldest hotfluid temperatue. Energy balance in a differential element of a single pass heat exchanger operated in the counterflow regime. Counter flow heat exchangers are the most efficient of the three types. The exchanger takes one inlet and one outlet for hot fluid stream, and one inlet and one outlet for cold fluid stream. Numerical analysis of the influence of circuit arrangement on a fin. R sekulib university of kentucky introduction a heat exchanger is a device that is used for transfer of thermal energy enthalpy between two or more fluids, between a solid surface and a fluid, or between solid particulates and a.
Therein, popular analytical techniques such as log mean temperature difference lmtd and effectivenessnumber of. John richard thome ltcm sgm epfl heat transfer heat exchanger design 1er mars 2008 6 41 the cross. Red, blue, and gray colors represent the hot fluid, cold fluid, and the partition between the fluids, respectively. In a few heat exchangers, the fluids exchanging heat are in direct contact. Pdf heat exchangers are devices used to transfer heat between two or more fluid. In this paper a mathematical model for crossflow heat exchangers with complex flow. The heat exchanger block is used when two process streams are to exchange heat based on equations 11 14. Introduction to engineering heat transfer these notes provide an introduction to engineering heat transfer. Recent development of generalized correlations, taking theoretical, semiempirical 4 or.
In most heat exchangers, the fluids are separated by a heat transfer surface and ideally they do not mix. Geosciences at the crossroads of theory and practice, pp. Overall heat transfer coefficient overall heat transfer coefficient k is a measure of the resistance to heat flow, made up of the resistances caused by the plate material, amount of foul ing, nature of the fluids and type of exchanger used. Hydrodynamics and heat transfer of single and multiphase flows in.
Heat exchangers 73 individual thermal resistances of the system. By combining the first law with fouriers law, we have eliminated the unknown q. The goal has been to develop a highquality heat exchanger with a very low thermal. Finandtube heat exchangers are widely used in airconditioning. Composite heat exchangers combine the best features of their parent. Introduction a heat exchanger is a device built for efficient heat transfer from one medium to another in order to carry and process energy. The notes are intended to describe the three types of heat transfer and provide. In this chapter we will examine the basic theory of heat exchangers and consider many. Typically one medium is cooled while the other is heated. The model is validated through comparison with theoretical algebraic relations for singlepass crossflow. The optimum heat transfer rate takes place in a balanced counter flow heat exchanger and by using this optimum rate of heat transfer, the concept of heat exchanger efficiency is introduced as the. Viscosityisexpressedincentipoisecp or centistoke cst. To answer this, we need some basics of the kinetic theory of gases.
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