Abstract: It is not clear whether Nano-refrigerant can enhance boiling heat transfer in tubes．It investigates experimentally nano—refrigerant boiling heat transfer in a horizontal smooth tube(8．1 2 mmlD)，a tube uniformly heated by electric wire．The nano-refrigerant was HCFC141 b mixed with CNT and its volume concentration was 0．1 g／L．The experimental tests were carried out under the following conditions：(i)the refrigerant mass fluxes within the range 95．7～382．9 k (m ·s)；(ii)the heat fluxes within the range 5～20 kW／m ；(iii)the inlet vapor qualities from 0．1 to 0．8．The effects on measured heat transfer coeficient of mass flux，imposed heat flux and inlet vapor
quality were examined in detail．The experimental results show that the nano—refrigerant will enhance boiling heat transfer within small mass fluxes(95．7 kg／(m ·s))．However，its effect will be weakened or it will even reduce heat transfer coeficient as the mass fluxes and vapor qualities increase．