HEAT TRANSFER IN HELICALLY-COILED TUBES WITH LAMINAR FLOW.

Experimental measurements of local heat transfer coefficients for laminar flow inside a helical coil were made. The various heat transfer mechanisms that occur with laminar flow in a helically coiled tube were investigated in the entrance region, where oscillatory behavior is expected. Three fluids, ethylene glycol, distilled water and normal butyl alcohol, were heated using a helical coil with a coil diameter to inside tube diameter ratio of 20. 2. Local outer surface temperatures were measured circumferentially and axially along the length of the coil. The effect of natural convection was found to be very significant at low Reynolds numbers. The study covered the fluid flow range extending from a Reynolds number of 30 to 5500 and a Prandtl number of 2 to 113.