Performance improvement of existing 200 litres capacity natural convection type domestic solar hot water system is attempted.A two-stage centrifugal pump driven by a vertical axis windmill having Savonius type rotor i...Performance improvement of existing 200 litres capacity natural convection type domestic solar hot water system is attempted.A two-stage centrifugal pump driven by a vertical axis windmill having Savonius type rotor is added to the fluid loop.The windmill driven pump circulates the water through the collector.The system with necessary instrumentation is tested over a day.Tests on Natural Circulation System(NCS)mode and Wind Assisted System(WAS)mode are carried out during January,April,July and October,2009.Test results of a clear day are reported.Daily average efficiency of 25-28% during NCS mode and 33-37% during WAS mode are obtained.With higher wind velocities,higher collector flow rates and hence higher efficiencies are obtained.In general,WAS mode provides improvements in efficiency when compared to NCS mode.展开更多
Boiling heat transfer condition has significance for pool-type research reactors cooled by natural circulation.It has important effect on the fuel element safety of reactor.On the basis of heat transfer characteristic...Boiling heat transfer condition has significance for pool-type research reactors cooled by natural circulation.It has important effect on the fuel element safety of reactor.On the basis of heat transfer characteristics of the Xi'an pulsed reactor(XAPR),fuel conduction,single-phase convection and boiling heat transfer,and void fraction models of the core are constructed.To validate the correctness of the physical models presented in the paper,numerical calculation based on a subchannel analysis method of XAPR is carried out,and the temperature fields are measured in some reactor coolant channels.The comparison between the calculated and experimental results verifies the effectiveness of the models.These physical models are used to calculate the thermal-hydraulic parameters of XAPR at the rated power(for XAPR the rated power is 2.0 MW in steady-state operation).The results indicate that subcooled boiling occurs in the XAPR core but it exhibits a subcooling degree which is considerably higher than that of saturation boiling.Subcooled boiling improves the efficiency of heat transfer between the fuel element surface and coolant,as well as effectively protects fuel elements.This research is also a beneficial reference in thermal-hydraulic analysis for other natural circulation reactors.展开更多
文摘Performance improvement of existing 200 litres capacity natural convection type domestic solar hot water system is attempted.A two-stage centrifugal pump driven by a vertical axis windmill having Savonius type rotor is added to the fluid loop.The windmill driven pump circulates the water through the collector.The system with necessary instrumentation is tested over a day.Tests on Natural Circulation System(NCS)mode and Wind Assisted System(WAS)mode are carried out during January,April,July and October,2009.Test results of a clear day are reported.Daily average efficiency of 25-28% during NCS mode and 33-37% during WAS mode are obtained.With higher wind velocities,higher collector flow rates and hence higher efficiencies are obtained.In general,WAS mode provides improvements in efficiency when compared to NCS mode.
文摘Boiling heat transfer condition has significance for pool-type research reactors cooled by natural circulation.It has important effect on the fuel element safety of reactor.On the basis of heat transfer characteristics of the Xi'an pulsed reactor(XAPR),fuel conduction,single-phase convection and boiling heat transfer,and void fraction models of the core are constructed.To validate the correctness of the physical models presented in the paper,numerical calculation based on a subchannel analysis method of XAPR is carried out,and the temperature fields are measured in some reactor coolant channels.The comparison between the calculated and experimental results verifies the effectiveness of the models.These physical models are used to calculate the thermal-hydraulic parameters of XAPR at the rated power(for XAPR the rated power is 2.0 MW in steady-state operation).The results indicate that subcooled boiling occurs in the XAPR core but it exhibits a subcooling degree which is considerably higher than that of saturation boiling.Subcooled boiling improves the efficiency of heat transfer between the fuel element surface and coolant,as well as effectively protects fuel elements.This research is also a beneficial reference in thermal-hydraulic analysis for other natural circulation reactors.