By comparing the heat transfer characteristics of dropwise condensation of natural refrigerant R290 and conventional refrigerant R22

following conclusions are obtained.The effect of surface subcooling degree on the smallest radius and the critical radius of droplet is much larger than that of the saturation temperature

and larger surface subcooling degree makes the smallest radius and the critical radius of droplet smaller.The smallest radius and the critical radius of R290 show little difference from those of R22.The heat transfer capacity through the single droplet of R290 or R22 increases first and then decreases with the increase of contact angle

suggesting the existence of the maximum heat transfer capacity.The heat transfer capacity through the single droplet increases with the increase of surface subcooling degree and decreases with the increase of the saturation temperature.The heat transfer capacity through the single droplet of R290 is obviously larger than that of R22.The dropwise condensation heat flux of R290 or R22 through the heat transfer surface has maximum value at the optimum contact angle.The dropwise condensation heat flux of R290 is obviously higher than that of R22.