ENHANCEMENT OF COOLANT SIDE HEAT TRANSFER IN WATER COOLED ENGINES BY USING FINNED CYLINDER HEADS

摘要

An experimental investigation has been carried out for almost the first time to examine the heat transfer by forced convection and subcooled boiling from a finned water-cooled engine cylinder head using steady state technique. Cast iron and cast steel specimens with and without fins have been used in the present work. The effects of flow velocity, coolant bulk temperature, fin length, fin number and fin material have been examined. It has been found that the use of finned cylinder head surface greatly improves the forced convection heat transfer coefficient and subcooled boiling heat flux as the fin length and number influenced the heat transfer process. The cast iron specimen exhibited better heat transfer characteristics over the cast steel one. The effects of bulk flow velocity and temperature for flat and finned specimens have been evaluated for forced convection and subcooled boiling. A correlation has been developed to relate the Nusselt number with Reynolds' number, Prandtl number, viscosity ratio and fin length ratio, for forced convection from the cast iron specimen, which read: Nu = 0.023 Re~(0.697) Pr~(0.33) μ_r~(0.14) (1+A)~(0.623).