Enhanced pool boiling heat transfer of the porous structure is critical to the thermal management technology.In this paper,pool boiling heat transfer experiments are performed on copper foam welded surfaces in de-ioni...Enhanced pool boiling heat transfer of the porous structure is critical to the thermal management technology.In this paper,pool boiling heat transfer experiments are performed on copper foam welded surfaces in de-ionized water to investigate the effects of basic parameters of copper foam on heat transfer enhancement.Boiling phenomenon is observed to facilitate the understanding of enhancement mechanism.The results show that copper foam welded surfaces can significantly enhance the pool boiling heat transfer performance,reduce the boiling incipience temperature by 7-9℃,and reach two times heat transfer coefficient compared with smooth plain surfaces due to numerous nucleation sites,extended surface areas,and enhanced turbulent effect.Pore density and thickness of foam have two side effects on heat transfer.展开更多
In the present study, pool boiling heat transfer performance and bubble behaviors of hybrid structures with metal foam and square column are investigated by lattice Boltzmann method. By using the vapor-liquid phase ch...In the present study, pool boiling heat transfer performance and bubble behaviors of hybrid structures with metal foam and square column are investigated by lattice Boltzmann method. By using the vapor-liquid phase change model of Gong-Cheng and Peng-Robinson equation of state, the effects of structural parameters, including metal foam thickness, porosity, column height and ratio of column width(W) to gap spacing(D) are investigated in details. The results show that hybrid structure performs better than pure columnar structure in pool boiling heat transfer. The hybrid structure accelerates bubble growth by fluid disturbance while metal skeletons prevent the bubble escaping. The optimum ratio of column width to gap spacing decreases with the increase of heat flux and HTC(heat transfer coefficient) can achieve an increase up to 25% when W/D change from 5/3 to 1/3. The increase of column height enhances heat transfer by expanding surface area and providing space for bubble motion. The metal foam thickness and porosity have a little influence on pool boiling heat transfer performance, but they have an important effect on bubble motion in the regime.展开更多
基金supported by the National Natural Science Foundation of China(No.52075249)the Foundation of Jiangsu Key Laboratory of Bionic Functional Materials(No.NJ2020026)
文摘Enhanced pool boiling heat transfer of the porous structure is critical to the thermal management technology.In this paper,pool boiling heat transfer experiments are performed on copper foam welded surfaces in de-ionized water to investigate the effects of basic parameters of copper foam on heat transfer enhancement.Boiling phenomenon is observed to facilitate the understanding of enhancement mechanism.The results show that copper foam welded surfaces can significantly enhance the pool boiling heat transfer performance,reduce the boiling incipience temperature by 7-9℃,and reach two times heat transfer coefficient compared with smooth plain surfaces due to numerous nucleation sites,extended surface areas,and enhanced turbulent effect.Pore density and thickness of foam have two side effects on heat transfer.
基金supported by the National Natural Science Foundation of China(Grant No.52276075)。
文摘In the present study, pool boiling heat transfer performance and bubble behaviors of hybrid structures with metal foam and square column are investigated by lattice Boltzmann method. By using the vapor-liquid phase change model of Gong-Cheng and Peng-Robinson equation of state, the effects of structural parameters, including metal foam thickness, porosity, column height and ratio of column width(W) to gap spacing(D) are investigated in details. The results show that hybrid structure performs better than pure columnar structure in pool boiling heat transfer. The hybrid structure accelerates bubble growth by fluid disturbance while metal skeletons prevent the bubble escaping. The optimum ratio of column width to gap spacing decreases with the increase of heat flux and HTC(heat transfer coefficient) can achieve an increase up to 25% when W/D change from 5/3 to 1/3. The increase of column height enhances heat transfer by expanding surface area and providing space for bubble motion. The metal foam thickness and porosity have a little influence on pool boiling heat transfer performance, but they have an important effect on bubble motion in the regime.
文摘泡沫金属具有超大比表面积和高热导率,将其填充于换热管内可用于制冷空调系统的强化传热。研究了R1234ze(E)在泡沫金属管内的流动沸腾换热和压降特性。实验工况为:干度0.1~0.9,质流密度90~180 kg·m^(-2)·s^(-1),热通量12.4~18.6 k W·m^(-2)。测试样件为泡沫铜填充管,孔密度为10~40 PPI、孔隙率为90%~95%。实验结果表明,R1234ze(E)比R410A的传热系数低2%~10%,两相压降低30%~42%;当干度大于0.8时,低质流密度下泡沫金属管内传热系数随干度的增加增幅更大;泡沫金属在强化流动沸腾换热的同时,造成压降显著增加,换热影响因子的范围为1.23~2.90,压降影响因子的范围为6~45。开发了适用于R1234ze(E)的泡沫金属管内流动沸腾换热和压降关联式,传热系数和两相压降的预测值与95%的实验值误差分别在±15%和±25%以内。
