Numerical investigation of the unsteady two-dimensional slot jet impingement cooling of a horizontal heat source is carried out in the present article. The jet velocity is assumed to be in the laminar flow regime and ...Numerical investigation of the unsteady two-dimensional slot jet impingement cooling of a horizontal heat source is carried out in the present article. The jet velocity is assumed to be in the laminar flow regime and it has a periodic variation with the flow time. The solution is started with zero initial velocity components and constant initial temperature, which is same as the jet temperature. After few periods of oscillation the flow and heat transfer process become periodic. The performance of the jet impingement cooling is evaluated by calculation of friction coefficient and Nusselt number. Parametric study is carried out and the results are presented to show the effects of the periodic jet velocity on the heat and fluid flow. The results indicate that the average Nusselt number and the average friction coefficient are oscillating following the jet velocity oscillation with a small phase shift at small periods. The simulation results show that the combination of Re =200 with the period of the jet velocity between 1.5 sec and 2.0 sec and high amplitude (0.25 m/s to 0.3 m/s) gives average friction coefficient and Nusselt number higher than the respective steady-state values.展开更多
Parametric study is carried out in the present article to investigate the unsteady performance of solar energy gain and heat retention of two different integrated-collector-storage systems. The systems are the convent...Parametric study is carried out in the present article to investigate the unsteady performance of solar energy gain and heat retention of two different integrated-collector-storage systems. The systems are the conventional rectangular-shaped storage tank and the modified tank shaped as rectangular cuboid with one semi -circular top. The two systems have the same absorber surface area and volume for water. The heat and fluid flow is assumed to be unsteady, two-dimensional, laminar and incompressible. The performances of the two systems are evaluated based on the maximum temperature in the system during daytime heating period and nighttime cooling period. For comprehensive study, 24 hours simulations for 3 cases with different wall boundary condition impose on the absorber plate are investigated. The simulation results show that the modified system has better heat retain than the conventional system. Periodic variations of both systems are investigated, and it is found that both systems show consistent results on different days. The modified system is able to store most of the thermal energy in the semi-circular top region with higher temperature than that of the conventional system.展开更多
文摘Numerical investigation of the unsteady two-dimensional slot jet impingement cooling of a horizontal heat source is carried out in the present article. The jet velocity is assumed to be in the laminar flow regime and it has a periodic variation with the flow time. The solution is started with zero initial velocity components and constant initial temperature, which is same as the jet temperature. After few periods of oscillation the flow and heat transfer process become periodic. The performance of the jet impingement cooling is evaluated by calculation of friction coefficient and Nusselt number. Parametric study is carried out and the results are presented to show the effects of the periodic jet velocity on the heat and fluid flow. The results indicate that the average Nusselt number and the average friction coefficient are oscillating following the jet velocity oscillation with a small phase shift at small periods. The simulation results show that the combination of Re =200 with the period of the jet velocity between 1.5 sec and 2.0 sec and high amplitude (0.25 m/s to 0.3 m/s) gives average friction coefficient and Nusselt number higher than the respective steady-state values.
文摘Parametric study is carried out in the present article to investigate the unsteady performance of solar energy gain and heat retention of two different integrated-collector-storage systems. The systems are the conventional rectangular-shaped storage tank and the modified tank shaped as rectangular cuboid with one semi -circular top. The two systems have the same absorber surface area and volume for water. The heat and fluid flow is assumed to be unsteady, two-dimensional, laminar and incompressible. The performances of the two systems are evaluated based on the maximum temperature in the system during daytime heating period and nighttime cooling period. For comprehensive study, 24 hours simulations for 3 cases with different wall boundary condition impose on the absorber plate are investigated. The simulation results show that the modified system has better heat retain than the conventional system. Periodic variations of both systems are investigated, and it is found that both systems show consistent results on different days. The modified system is able to store most of the thermal energy in the semi-circular top region with higher temperature than that of the conventional system.
