HEAT TRANSFER AND PRESSURE DROP IN SINGLE PHASE TURBULENT FLOW INSIDE INTERNALLY HELICAL-GROOVED HORIZONTAL SMALL-DIAMETER TUBES

An experimental study of pressure drop and heat transfer in single-phase turbulent flow inside internally helical-grooved small-diameter tube were carried out using ten different kinds of tubes and a smooth small-diameter tube with 4.00 mm outer diameter. The ranges of geometric parameters of test tube were number of grooves (40 to 50), helix angle (0 to 25deg.) and fin height (0.10 to 0.20 mm). In the experiments, the water was used as a test fluid; its inlet temperature was kept at a constant 20 degrees C and the mass flow rate was varied from 0.016 to 0.048 kg/s. For these experiments, the electric heating capacity was adjusted in accordance with the same heat flux conditions as in the experiment conducted on a grooved tube with an outer diameter of 6.35 mm, and in a low mass flow rate region, the electric heating capacity was adjusted within a range where the difference between inlet and outlet temperatures in the experimental heat transfer section did not exceed 6 K. The effect of groove shape of an internally grooved small-diameter tube upon the pressure drop and heat transfer in the turbulent region was made clear, and those results were compared with the results of a grooved tube with an outer diameter of 6.35 mm.