In the paper presented has been a modified semi empirical correlation of Mikielewicz  enabling calculations of heat transfer coefficient in flow boiling in small diameter channels. The changes were of qualitative character as the entirely new data bank of experimental data points has been collected to devise a new form of correlation applicable to small diameter channels. The fluids considered were: R141b, R12 and R11 and the total number of experimental point considered amounted to over 210. The correction incorporates the surface tension effects into the two-phase flow multiplier as well as the convective number was amended. The use of correlation is very simple on account of its analytical form, which is its fundamental advantage. It is of general character, and its coefficients do not depend on the type of fluid. Comparisons with experimental data show good agreement.