The thermal resistances distribution in different wet-bulb temperatures, air velocities and spraying water densities were achieved by the experimental test. The fluctuation of the water film convection and the water-a...The thermal resistances distribution in different wet-bulb temperatures, air velocities and spraying water densities were achieved by the experimental test. The fluctuation of the water film convection and the water-air interfacial thermal resistance were reviewed especially. In the distribution of thermal resistance, the rank of the thermal resistance proportion （from max to min） is air flow heat transfer resistance, heat transfer resistance between refrigerant and wall, water film convection resistance and wall heat transfer resistance. When the heat flux is constant, the total resistance lowers nearly along with the increasing of air flow and water spray density. But there are a best air flow value of 2.98 m/s and a best spray water density of 0.064 kg/（m ·s） respectively, if continue to increase them, condensation performance is not significantly improved any more. The test results are available to improve the evaporative condenser performance and the designing lever.展开更多
For improving the properties of SiC-mullite composite ceramics used for solar sensible thermal storage, MnO2 was introduced as sintering additive when preparing. The composite ceramics were synthesized by using SiC, a...For improving the properties of SiC-mullite composite ceramics used for solar sensible thermal storage, MnO2 was introduced as sintering additive when preparing. The composite ceramics were synthesized by using SiC, andalusite, a-Al2O3 as the starting materials with non-contact graphite-buried sintering method. Phase composition and microstructure of the composites were investigated by XRD and SEM, and the effect of MnOz on the properties of SiC composites was studied. Results indicated that samples SM1 with 0.2 wt% MnO2 addition achieved the optimum properties： bending strength of 70.96 MPa, heat capacity of 1.02 J.（g.K）-1, thermal conductivity of 9.05 W-（m.K）-1. Proper addition of MnO2 was found to weaken the volume effect of the composites and improve the thermal shock resistance with an increased rate of 27.84% for bending strength after 30 cycles of thermal shock （air cooling from 1 100 ℃ to RT）. Key words： SiC-mullite composite ceramics; MnO2; solar sensible thermal storage; non-contact graphite-buried sintering; thermal shock resistance展开更多
文摘The thermal resistances distribution in different wet-bulb temperatures, air velocities and spraying water densities were achieved by the experimental test. The fluctuation of the water film convection and the water-air interfacial thermal resistance were reviewed especially. In the distribution of thermal resistance, the rank of the thermal resistance proportion （from max to min） is air flow heat transfer resistance, heat transfer resistance between refrigerant and wall, water film convection resistance and wall heat transfer resistance. When the heat flux is constant, the total resistance lowers nearly along with the increasing of air flow and water spray density. But there are a best air flow value of 2.98 m/s and a best spray water density of 0.064 kg/（m ·s） respectively, if continue to increase them, condensation performance is not significantly improved any more. The test results are available to improve the evaporative condenser performance and the designing lever.
基金Funded by the Major State Basic Research Development Program of China(973 Program)(No.2010CB227105)
文摘For improving the properties of SiC-mullite composite ceramics used for solar sensible thermal storage, MnO2 was introduced as sintering additive when preparing. The composite ceramics were synthesized by using SiC, andalusite, a-Al2O3 as the starting materials with non-contact graphite-buried sintering method. Phase composition and microstructure of the composites were investigated by XRD and SEM, and the effect of MnOz on the properties of SiC composites was studied. Results indicated that samples SM1 with 0.2 wt% MnO2 addition achieved the optimum properties： bending strength of 70.96 MPa, heat capacity of 1.02 J.（g.K）-1, thermal conductivity of 9.05 W-（m.K）-1. Proper addition of MnO2 was found to weaken the volume effect of the composites and improve the thermal shock resistance with an increased rate of 27.84% for bending strength after 30 cycles of thermal shock （air cooling from 1 100 ℃ to RT）. Key words： SiC-mullite composite ceramics; MnO2; solar sensible thermal storage; non-contact graphite-buried sintering; thermal shock resistance
