The condensation heat transfer, frictional pressure drop and refrigerant charge characteristics of R290 in minichannels with different diameters

•A numerical model of R290 condensation in minichannels was proposed and verified.•The effect of diameter on heat transfer and frictional pressure drop was analyzed.•The refrigerant charge of R290 in different pipe diameters was analyzed.•Reducing the diameter can reduce the refrigerant charge of R290 by 94.8%•Wall effects have a remarkable influence on HTC in small diameter and mass flux.