The boiling heat transfer coefficients of R410A are investigated in a single horizontal stainless steel microchannel with 2 mm inner diameter. The experiments are conducted by varying the mass flux from 200 to 600 kg/(m2?s)

heat flux from 5 to 15 kW/m2

quality from 0.1 to 0.8

while maintaining the saturation temperature at 0 ℃ and 5 ℃. The results show that the boiling heat transfer coefficients rise sharply with the increase of the heat flux when the quality is higher than 0.5

and the average increase amplitudes are 4.6% and 7.7%. The influence of the heat flux on heat transfer coefficients is negligible when the quality is lower than 0.5. The heat transfer coefficients rise slightly with the increase of the mass flux

and the average increase amplitudes are 1.1% and 2%. But the saturation temperature almost has no influence on heat transfer coefficients. After that

the possible mechanisms are discussed. At last

the results are also compared with the results of Choi et al and Ebisu et al

whose inner diameters are 1.5 mm

3 mm and 6.4 mm. It shows that the heat transfer coefficients will increase with the decrease of the inner diameter when the quality is lower than 0.5

and the average increase amplitudes are 18.4%

23.6% and 19.5% respectively.