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ISSN Online: 2377-424X
ISBN Print: 978-1-56700-421-2
International Heat Transfer Conference 15
Heat Transfer and Pressure Drop Characteristics in the Annuli of Tube-in-Tube Heat Exchangers (Horizontal Lay-Out)
Resumo
This paper reports on experimental research conducted on heat transfer and pressure drop phenomena in concentric annuli in tube-in-tube heat exchangers at different annular Reynolds numbers, annular diameter ratios, and inlet fluid temperatures using water. Turbulent flow with Reynolds numbers ranging from 10 000 to 50 000, based on the average bulk fluid temperature was considered at annular ratios of 0.327, 0.483 and 0.409. Both heated and cooled annuli were investigated by conducting tests at a range of inlet temperatures (10ºC - 30ºC for heating and 30ºC – 50ºC for cooling). The main focus of the experiment was to improve temperature measurement, especially local wall temperature measurements of the inner tube, with minimized convective effects on measurement stations. Using in-situ calibration of the thermocouples enabled continuous verification of accuracy and re-evaluation of readings. It was found that existing smooth annular heat transfer correlations were able to predict the heat transfer to within 10 - 35%. Furthermore, it has been shown that there was a difference in heat transfer coefficient between cooling and heating conditions of the annuli which are not suitably described by existing correlations. Friction factors were found to vary according to annular ratio, and are not suitably covered by existing correlations.
Palavras-chave:
Convection, Heat exchanger, Measurement and instrumentation, Annuli, Nusselt number, Friction factor