Numerical study on falling-film heat transfer of nanofluid outside a single horizontal tube

Falling-film evaporation is an advanced heat transfer technology, but its heat transfer performance depends on the thermal conductivity of the working fluid. The thermal conductivity of the existing working fluid is low, which is not conducive to the further enhancement of heat transfer on the liquid film side. Based on the research results that adding nanoparticles to liquid can greatly improve its thermal conductivity and heat transfer performance, a method for enhancing falling-film heat transfer using nanofluid technology is proposed. Falling-film heat transfer properties of a horizontal single-tube outer nanofluid are investigated by numerical simulation. The results show that the concentration of nanoparticles has little effect on the thickness of the liquid film. With the increase of the circumferential angle, the surface heat transfer coefficient can be divided into four different regions including the stagnation region, the agitation region, the heat development region and the detachment region. Within a certain circumferential angle range, the local surface heat transfer coefficient increases with the increase of the nanoparticle concentration and the increase of the nanoparticle concentration leads to an increase in the surface heat transfer coefficient of the falling-film flow.