Abstract:The roughness influence on flow boiling heat transfer characteristics of nanofluid refrigerant in direct metal laser sintering (DMLS) micro heat exchangers was analyzed through changing the roughness of different DMLS micro heat exchanger channels surface by using chemical polishing technology and preparing 0.01% Al2O3/R141b as working medium under the conditions of different heat fluxes 9.4 ~29.4kW/m2 and mass flow rates 184.3~432.2kg/(m2·s) in order to research the roughness of DMLS micro heat exchanger channels surface impact on flow boiling heat transfer characteristics of nanofluid refrigerant. The research results showed that roughness had a significant impact on flow boiling heat transfer of Al2O3/R141b in DMLS micro heat exchangers and heat transfer performance was weakened with the decrease of roughness, which was found that heat transfer coefficient was weakened by 22.5% when roughness was decreased by 80.4%. And the average heat transfer coefficient which the surface roughness of DMLS micro heat exchanger channels were 5.8μm, 3.2μm and 1.7μm were weakened by 7.1%, 14.1% and 22.5% compared with the surface roughness of DMLS micro heat exchanger channels was 8.7μm under the same conditions, respectively. It was also found that nanofluid refrigerant had much more contact area with the channel surface per unit length channels which degree of concave and convex surface was greater on the DMLS micro heat exchanger larger roughness surface so that it made refrigerant have more nucleate gasification density in per unit area and nucleation starting point in advance and another thing was that superheating degree was much lower, which were conducive to strengthening heat transfer effect. It verified the validity of the mathematical model and the reliability of the experimental results as the value of MAE was 9.88%, which was relative deviation between experimental results and revised LAZAREK heat transfer model.
