HEAT TRANSFER AND PRESSURE DROP CHARACTERISTICS OF R410A-OIL MIXTURE FLOW BOILING IN A HORIZONTAL STRAIGHT SMOOTH TUBE

摘要

Experimental studies of local heat transfer coefficients and pressure drops of R410A-oil mixture flow boiling in a horizontal straight smooth tube are performed. The inside and outside diameters of the test tube are 7.0 mm and 6.34 mm, respectively. Experimental parameters include evaporating temperature of 5°C, mass flux from 200 to 400 kg/(m2s), heat flux from 7.56 to 15.1 kW/m2, inlet vapor quality from 0.2 to 0.7, nominal inlet oil concentration from 0 to 5%. The flow patterns are observed through the sight glasses at the entrance and exit of the test section, and the effect of oil on flow patterns is discussed. The effects of oil on heat transfer and pressure drop characteristics are analyzed. New correlations for predicting local heat transfer coefficients and frictional pressure drops of R410A-oil mixture flow boiling inside the horizontal straight smooth tube are developed based on the mixture properties and the experimental data. These correlations can agree with the experiment data well.