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 diesel engine. The parametric test matrix involves Reynolds, Dean, pulsating and buoyancy numbers, respectively, in the ranges 4500-7000, 1050-1600, 0.135-0.458 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 pulsating force and reciprocating buoyancy interactively affect the local heat transfer along the inner and outer edges of the coils is illustrated using a number of experimentally based observations. The experimental data reconfirm the presence of Dean vortices with attendant relative increase in local heat transfer on the outer surface, even with the agitated flow field caused by ribs under a reciprocating environment. The pulsating force and reciprocating buoyancy have a considerable influence on the heat transfer present due to the modified vortex flow structures in the ribbed coils. An empirical correlation, which is physically consistent, was developed that permits the individual and interactive effects of pulsating force and reciprocating buoyancy on heat transfer in the ribbed coils to be evaluated. (C) 2001 Elsevier Science Ltd. All rights reserved.