Under a promotion of energy conservation and emission reduction

efforts on research and development of the technologies related to boiling heat transfer enhancement of outer tube have been conducted extensively. In this article

a testing system for boiling heat transfer outside the horizontal double-side enhanced tubes was established. Using R134a as a cyclic working medium

the effect of evaporation temperature on the characteristics of boiling heat transfer in three-dimensional ribbed and embossing finned tube under conditions of varied heat flux was investigated

on basis of which theoretical descriptive method was discussed. It showed that

the curve slope of evaporation heat transfer coefficient as a function of evaporation temperature is non-linearly related to the heat flux. At the same evaporation temperature

it shows a monotonic increase in the heat transfer coefficient on tube surface with the heat flux

of which the slope gradually decreases with the heat flux. By means of regression analysis

an unified formula for the heat transfer coefficient on ribbed and embossing finned tube surface as a function of evaporation temperature under conditions of varied heat flux was achieved. Under operation condition of the same heat flux

the factor of heat transfer enhancement approaches 1

exceeds 2

and reaches the maximum 2.588 at 5

10 and 20 kW·m-2 of heat flux

respectively. The mechanism and theoretic description of the heat transfer coefficient on ribbed and embossing finned tube surface as functions of evaporation temperature and heat flux

need to be further studied.