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ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

International Heat Transfer Conference 13
August, 13-18, 2006, Sydney, Australia

LOCAL HEAT TRANSFER COEFFICIENTS IN PLATE HEAT EXCHANGERS MEASURED WITH TEMPERATURE OSCILLATION IR THERMOGRAPHY

Get access (open in a dialog) DOI: 10.1615/IHTC13.p18.370
12 pages

Abstract

A method for the measurement of local convective heat transfer coefficients from the outside of a heat-transferring wall has been developed. This method is contact-free and fluid independent, employing radiant heating by laser or halogen spotlights and an IR camera for surface temperature measurements; it allows for the rapid evaluation of the heat transfer coefficient distribution of sizable heat exchanger areas. The technique relies first on experimental data of the phase-lag of the outer surface temperature response to periodic heating, and second on a 3-D numerical model of the heat exchanger wall to compute the local heat transfer coefficients from the processed data. The IR temperature data processing includes an algorithm for temperature drift compensation, phase synchronization between the periodic heat flux and the measured temperatures, and Single Frequency Discrete Fourier Transformations. The ill-posed inverse heat conduction problem of deriving a surface map of heat transfer coefficients from the phase-lag data is solved with a complex number finite-difference method. The sensitivity of the calculated heat transfer coefficients to the measured phase-lag as well as the optimum frequency and expected errors are discussed. The first results from the application of this method to plate heat exchangers are presented, along with measurements conducted on pipe flow for validation. The results show high-resolution surface maps of the heat transfer coefficients for a chevron-type plate for three turbulent Reynolds numbers. The area-integrated values agree well with literature data. The experiments also include a promising approach of visualizing the flow field of the entire plate.