A general review of the wilson plot method and its modifications to determine convection coefficients in heat exchange devices.Applied Thermal Engineering, Elsevier, 2007, 27 (17-18) ACCEPTED MANUSCRIPTPage 1 equations. This paper is to present an overview of the Wilson plot method along with numerous modifications introduced by researches throughout the years to improve its accuracy and to extend its use to a multitude of convective heat transfer problems. Undoubtedly, this information will be useful to thermal design engineers. A GENERAL REVIEW OF THE WILSON PLOT METHOD AND ITS MODIFICATIONS TO DETERMINE CONVECTION COEFFICIENTS IN HEAT EXCHANGE DEVICES

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As a result of environmental problems related to global warming and depletion of the ozone layer caused by the use of synthetic refrigerants (CFC's, HCFC's and HFC's) experienced over the last decades, the return to the use of natural substances for refrigeration purposes, appears to be the best long-term alternative. In this paper a cascade refrigeration system with CO 2 and NH 3 as working fluids in the low and high temperature stages respectively, has been analyzed. Results of COP and exergetic efficiency versus operating and design parameters have been obtained. In addition, an optimization study based on the optimum CO 2 condensing temperature has been done. Results show that following both method's exergy analysis and energy optimization, an optimum value of condensing CO 2 temperature is obtained. The compressor isentropic efficiency influence on the optimum system COP has been demonstrated. A methodology to obtain relevant diagrams and correlations to serve as a guideline for design and optimization of this type of systems has been developed and it is presented in the paper.

The Wilson plot is a technique to estimate the film coefficients in several types of heat transfer processes and to obtain general heat transfer correlations. This method is an outstanding tool in practical applications and in laboratory research activities that involve analysis of heat exchangers. Moreover, the application of this method is simple enough to be taught in laboratory practices for students at university and doctoral level of physics and engineering. Therefore, an experimental apparatus has been designed and built in our laboratory that allows the students to carry out experiments based on the application of the Wilson plot method. In this note, the principles of the method are explained, the experimental apparatus is described and representative results of the experimental data taken from the apparatus and the application of the Wilson plot method are shown.

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