Boiling heat transfer and pressure drop of a refrigerant flowing vertically upward in small rectangular and triangular tubes

In the present study, experiments were performed to examine the characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically upward in small copper rectangular and triangular tubes with hydraulic diameters of 1.04 and 0.88 mm, respectively, for the development of a high-performance heat exchanger using small tubes or minichannels for air-conditioning systems. Their characteristics were clarified by comparing the previous experimental data of the small circular tube (1.00 mm internal diameter). In the rectangular and triangular tubes, the pressure drop was found to be slightly lower and the heat transfer was much better than in the circular tube.