An experimental investigation is carried out on friction and heat transfer characteristics of four spirally corrugated tubes with various geometrical parameters for the turbulent flow of single - phase water and oil. The correlations of momentum transfer roughness function ( R - function) and heat transfer roughness function ( G - function) are developed on the basis of momentum and heat transfer analogy from the present data and are compared with the results of previous investigators. A modified procedure is proposed to evaluate the performance of enhanced heat transfer concerning the large variation of oil Pr with temperature

and it is used for the performance evaluation of tube 1 and 2. Tne investigation results can be applied to heat exchanger design and optimization of geometrical parameters of spirally corrugated tubes.