For calculating the thermal storage time for an annular tube with phase change material （PCM）, a novel method is proposed. The method is suitable for either low-temperature PCM or high-temperature PCM whose initial ...For calculating the thermal storage time for an annular tube with phase change material （PCM）, a novel method is proposed. The method is suitable for either low-temperature PCM or high-temperature PCM whose initial temperature is near the melting point. The deviation fit is smaller than 8% when the time is below 2x104 s. Comparison between the predictions and the reported experimental data of thermal storage time at same conditions is investigated and good agreements have been got. Based on this method, the performance of the thermal storage unit and the role of natural convection are also investigated. Results show a linear relation between the maximum amount of stored heat and thermal storage time, and their ratio increases with the height of the thermal storage unit. As the thickness of the cavity increases, natural convection plays an increasingly important role in promoting the melting behavior of paraffin. When the thickness of the cavity is small, natural convection restrains the melting behavior of paraffin.展开更多
Natural convection heat transfer in eccentric annuli made of two isothermal horizontal circular cylinders is numerically investigated. Bipolar coordinates are used for the eccentric annuli. The governingequations are ...Natural convection heat transfer in eccentric annuli made of two isothermal horizontal circular cylinders is numerically investigated. Bipolar coordinates are used for the eccentric annuli. The governingequations are transformed into finite difference equations (FDE) by the central difference approach.Heat transfer and flow convection pattern results are simulated for 5.0≤RaL≤1.0×105, withPr = 0.3 - 100, Do/Di = 1.25 - 5.0, andε= 0.01-0.95. The axis of the inner cylinder lies onan inclined plane with θp= 0°- 180°.A Mach-Zehnder interferometer is used for the experimentalstudy. The range is for RaL = 5.3×102-2.41×104, with Do/Di = 2.0, 2.5 and 3.125,ε= 0.0-0.85,and θp= 0°-180°.Air is used as the medium. Comparison of the numerical results with the experimental data shows good agreement.展开更多
The thermal performance of a rectangular loop with a horizontal heating segment and a partly cooling vertical leg is studied. By one-dimensional approach, traditional friction factor and empirical correlation, a modif...The thermal performance of a rectangular loop with a horizontal heating segment and a partly cooling vertical leg is studied. By one-dimensional approach, traditional friction factor and empirical correlation, a modified Grashof number Gr* which turns out to be very important in the description of circulation flow is introduced. A new correlation for Nusselt number of the horizontal heater is obtained and the comparison with experimental raines shows good agreement.展开更多
基金Projects(51666006,51406071,51174105,51366005)supported by the National Natural Science Foundation of ChinaProject(2014CB460605)supported by the National Basic Research Program of China
文摘For calculating the thermal storage time for an annular tube with phase change material （PCM）, a novel method is proposed. The method is suitable for either low-temperature PCM or high-temperature PCM whose initial temperature is near the melting point. The deviation fit is smaller than 8% when the time is below 2x104 s. Comparison between the predictions and the reported experimental data of thermal storage time at same conditions is investigated and good agreements have been got. Based on this method, the performance of the thermal storage unit and the role of natural convection are also investigated. Results show a linear relation between the maximum amount of stored heat and thermal storage time, and their ratio increases with the height of the thermal storage unit. As the thickness of the cavity increases, natural convection plays an increasingly important role in promoting the melting behavior of paraffin. When the thickness of the cavity is small, natural convection restrains the melting behavior of paraffin.
文摘Natural convection heat transfer in eccentric annuli made of two isothermal horizontal circular cylinders is numerically investigated. Bipolar coordinates are used for the eccentric annuli. The governingequations are transformed into finite difference equations (FDE) by the central difference approach.Heat transfer and flow convection pattern results are simulated for 5.0≤RaL≤1.0×105, withPr = 0.3 - 100, Do/Di = 1.25 - 5.0, andε= 0.01-0.95. The axis of the inner cylinder lies onan inclined plane with θp= 0°- 180°.A Mach-Zehnder interferometer is used for the experimentalstudy. The range is for RaL = 5.3×102-2.41×104, with Do/Di = 2.0, 2.5 and 3.125,ε= 0.0-0.85,and θp= 0°-180°.Air is used as the medium. Comparison of the numerical results with the experimental data shows good agreement.
文摘The thermal performance of a rectangular loop with a horizontal heating segment and a partly cooling vertical leg is studied. By one-dimensional approach, traditional friction factor and empirical correlation, a modified Grashof number Gr* which turns out to be very important in the description of circulation flow is introduced. A new correlation for Nusselt number of the horizontal heater is obtained and the comparison with experimental raines shows good agreement.
