An Investigation on Flow Boiling Heat Transfer Inside Horizontal Tubes with Superhydrophobic and Superhydrophilic Wire Coil Insets

Contact angle of surface is an influencing factor in heat transfer, especially for two phase flows. Therefore, in this research, the heat transfer coefficient (HTC) of boiling will be investigated for R۱۳۴a flow as refrigerant in horizontal tube with uncoated, superhydrophilic and superhydrophobic wire-coils inserted. In this experimental research, a copper tube with inner diameter of ۱۱.۳ mm and wire-coils made of aluminum ۶۰۶۱ with thicknesses of ۱ and ۱.۵ mm and pitch of ۱۱.۳ mm have been used. The mass velocities are ۶۰ and ۸۰ kg/m۲s, and the experiments were performed under a constant heat flux of ۴.۱ kW/m۲. First, the tests were performed on uncoated wire-coils insert tube and then on tube with superhydrophilic and superhydrophobic wire-coils, and the results were compared. The effects of superhydrophilic and superhydrophobic wire-coils on the HTC depended on the quality of vapor. In low qualities, both of them don’t have significant effects on HTC But in the higher qualities, compare to uncoated wire-coil the heat transfer coefficient for superhydrophilic wire-coils decreases by ۵% and superhydrophobic wire-coils enhance HTC up to ۸%.

کلیدواژه ها:

Heat transfer ، Boiling flow ، wire-coils ، superhydrophobic ، superhydrophilic