Evaporation Heat Transfer and Pressure Drop in Horizontal Tubes With Strip-Type Inserts Using Refrigerant 600a

摘要

Results of a study on saturated boiling heat transfer of refrigerant R-600a in horizontal tubes (ID=10.6 mm) with strip-type inserts (longitudinal strip LS with/without perforated holes and cross- strip CS inserts) are reported. Local heat transfer coefficients are measured for a range of heat flux (9.1～31.2 kW/m~2), mass ve- locity (8.23～603.3 kg/m~2s), and equilibrium mass quality (≤0.8) and the influences were studied. The data were compared with the performance of the corresponding smooth tubes. En- hancement factors are presented and discussed. Pressure drop measurement was also conducted and it is found that both single- phase and two-phase pressure drops increase with increasing heat flux levels and mass velocities.