An experimental analysis of heat transfer in coiled tubes

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Virginia Polytechnic Institute and State University

The axial temperature distribution and average heat transfer coefficients were measured for a coiled tube heat exchanger. Water was heated inside the tube under turbulent flow conditions by low pressure steam condensing on the outside. Inside and outside film coefficients were determined at relatively high Reynolds numbers. Consequently, inside convection coefficients were of the same order of magnitude as the outside condensation coefficients. The inside coefficients were found to be in agreement with recent analytical solutions. Even with large variations in fluid transport properties, the axial temperature distribution was essentially linear and therefore may be represented by previous analytical solutions.

Initial measurement of convective dispersion in coiled tubes was attempted using magnetic flowmeters. This approach was not successful and yielded only preliminary qualitative information as a result of an unexpected experimental problem. Recommendations are presented for an improved flowmeter design that could be used for future dispersion measurements.