不锈钢三维强化管内的换热和压降特性

采用实验方法对比制冷剂R410A在3根强化管和1根光滑管内的换热和压降特性。所有的三维双侧强化管均通过高压分层轧制制成，其立体化内表面结构分别是旋涡状凸起和船型凹坑与花瓣纹背景图案的叠加。通过热平衡分析，实验热损失小于5%。保持制冷剂侧流量不变的情况下，改变水侧的质量流率，可以通过Wilson图解法计算每个管型的水侧传热系数。经热阻模型计算，1EHT-1的管内单相换热性能最佳，3EHT次之，1EHT-2最弱。3根强化管的蒸发和冷凝换热实验结果差距较大，不锈钢的低热导率对凸起/凹坑区域的温度分布影响是主要原因。

Heat transfer and pressure drop characteristics inside stainless steel three-dimensional enhanced tubes

Heat transfer and pressure drop characteristics of refrigerant R410A inside three horizontal enhanced tubes (EHT) and one smooth tube were investigated experimentally. All stainless steel two-side enhanced tubes were fabricated using a multiple high-pressured extruding process. These three-dimensional two-layer surface structures are composed of staggered dimpled protrusions or boat-shaped cavities and petal-shaped background patterns in a grid-like arrangement. According to the single-phase heat balance analysis, the proportion of heat loss in total heat is no more than 5% for the entire test range. Changing the water flow rate in the case where the refrigerant mass flow rate was maintained at a fixed value, the water-side heat transfer coefficients for each tube tested were obtained by the Wilson plot method. On basis of the thermal resistance model, it was found that 1EHT-1 exhibits the best single-phase heat transfer performance, followed by the 3EHT and 1EHT-2. A large difference between the experimental results of these evaporation and condensation tests was observed in the three enhanced tubes. It can be attributed to the effect of low thermal conductivity of stainless steel on the temperature distribution in the region of protrusions/cavities.