Heat transfer of reciprocating helical tube fitted with full circumferential ribs

This paper describes a detailed experimental investigation of heat transfer in a reciprocating helical tube fitted with full circumferential ribs with particular reference to the design of a piston for a marine propulsive die sel engine. The parametric test matrix involves Reynolds, Dean, pulsating a nd buoyancy numbers, respectively, in the ranges 4500-7000, 1050-1600, 0.13 5-0.458 and 0.000325-0.00943 with five different reciprocating frequencies tested, namely 0, 0.83, 1.25, 1.67 and 2 Hz. The manner in which the pulsat ing force and reciprocating buoyancy interactively affect the local heat tr ansfer along the inner and outer edges of the coils is illustrated using a number of experimentally based observations. The experimental data reconfir m the presence of Dean vortices with attendant relative increase in local h eat transfer on the outer surface, even with the agitated flow field caused by ribs under a reciprocating environment. The pulsating force and recipro cating buoyancy have a considerable influence on the heat transfer present due to the modified vortex flow structures in the ribbed coils. An empirica l correlation, which is physically consistent, was developed that permits t he individual and interactive effects of pulsating force and reciprocating buoyancy on heat transfer in the ribbed coils to be evaluated. (C) 2001 Els evier Science Ltd. All rights reserved.