Heat Transfer Characteristics in a Heat Exchanger for Turbulent Pulsating Water Flow with Different Amplitudes

The effect of pulsation on the heat transfer rates, for turbulent water stream with upstream pulsation of different amplitudes, in a double-pipe heat exchanger for both parallel and counter flows, with cold water on the shell side, was investigated. Pulsation frequencies, with using a reciprocating device, ranged up to 260 cycles per minute (up to 4.3 Hz) and 5 different displacement amplitudes were used, (Stroke length of the reciprocating piston was varied from 60 to 185 mm), at different Reynolds numbers 3855-11570. The experimental results indicate that the heat exchanger with a reciprocating piston inserting upstream the flow provides a considerable improvement of the heat transfer rate. The heat transfer coefficient was found to increase with pulsation, with the highest enhancement observed in the transition flow regime. The convective heat transfer coefficient for the turbulent flow was found to increase with pulsation for all pulsation frequencies and amplitudes with the highest enhancement of about 10 times. The maximum enhancement in Nusselt number for the parallel flow was about 8 times while it was about 10 times for the counter one. The improvement in Nusselt number was peaked with the amplitude for both parallel and counter flows. [A. E. Zohir, Heat Transfer Characteristics in a Heat Exchanger for Turbulent Pulsating Water Flow with Different Amplitudes. Journal of American Science 2012;8(2):241-250]. (ISSN: 1545-1003). http://www.americanscience.org..