Flow Frictional And Boiling Characteristics Of Refrigerant R134-a In Horizontal Microchannels

Experiments were conducted to investigate the friction and boiling characteristics of subcooled liquid of RI 34a flowing through five different microchannels. The results indicate that the nonabsorbent gas has an influence on the friction characteristic of single-phase liquid of RI 34a. The relations between frictional factor and Reynolds number of the five test sections have been derived. The heat transfer in microchannels is enhanced and the heat transfer coefficient of microchannels is higher than that of normally sized channels. The heat transfer coefficient is affected by the velocity, the shape of michannels and the equivalent diameter. The heat transfer coefficient increases while one of the following conditions meets: 1. increasing velocity; 2. using square channels to replace triangle channels;3.decreasing the diameter.