A numerical simulation on confined impinging circular jet working with a mixture of water and Al2O3 nanoparticles is investigated. The flow is turbulent and a constant heat flux is applied on the heated plate. A two-p...A numerical simulation on confined impinging circular jet working with a mixture of water and Al2O3 nanoparticles is investigated. The flow is turbulent and a constant heat flux is applied on the heated plate. A two-phase mixture model approach has been adopted. Different nozzle-to-plate distance, nanoparticle volume concentrations and Reynolds number have been considered to study the thermal performances of the system in terms of local, average and stagnation point Nusselt number. The local Nusselt number profiles show that the highest values within the stagnation point region, and the lowest at the end of the heated plate. It is observed that the average Nusselt number increases for increasing nanoparticle concentrations, moreover, the highest values are observed for H/D=5, and a maximum increase of 10% is obtained at a concentration equal to 5%.展开更多
This paper presents the two-dimensional analysis for the efficiency of continuous plate fin-tube heat exchangers in staggered and in-lined arrangements under the dry, partially wet, and fully wet conditions for differ...This paper presents the two-dimensional analysis for the efficiency of continuous plate fin-tube heat exchangers in staggered and in-lined arrangements under the dry, partially wet, and fully wet conditions for different heat transfer coefficient (h = 20 W/m2K to h = 80 W/m2K) and air relative humidity over the full range from φ= 0 % to φ= 100%. It is shown that the fin efficiencies of the staggered arrangement are higher than those for the in-lined arrangement, and the fully wet fin efficiency is 10~20% lower than that for a dry fin. The conventional 1-D sector method underestimates the fin efficiency up to 4 % as compared to the 2-D analysis.展开更多
In this study an incompressible flow with non-Newtonian fluids in the reverse roll coating process was investigated.Non-Newtonian behavior of the coating fluid was accounted by using power law model with power index,n...In this study an incompressible flow with non-Newtonian fluids in the reverse roll coating process was investigated.Non-Newtonian behavior of the coating fluid was accounted by using power law model with power index,n,ranging from 0.8 to 1.2.Effect of roll speed ratio(V2/V1)of the panel roll to the applicator roll and gap distance on the coating film thickness were also investigated.Numerical results were in good agreement with those of experimental data within 15%-20%.Results indicated that the film thickness ratios are function of power-law index,roll speed ration and ratio of roll radius to gap distance.The equations for film thickness ratio were obtained from numerical results as shown below:■,where t1,t2 and t3 are inlet film,transferred film and leakage film thickness,respectively,n is power-law index,V1 and V2 are roll speed of applicator roll and panel roll,Rm is average radius of two rolls and H0 is gap distance.The correlations are accurate within 10%for 0.8≤n≤1.2,0.5≤V_(2)/V_(1)≤2,and 7.7×10^(−5)≤H_(0)/R_(m)≤1.54×10^(−4).展开更多
文摘A numerical simulation on confined impinging circular jet working with a mixture of water and Al2O3 nanoparticles is investigated. The flow is turbulent and a constant heat flux is applied on the heated plate. A two-phase mixture model approach has been adopted. Different nozzle-to-plate distance, nanoparticle volume concentrations and Reynolds number have been considered to study the thermal performances of the system in terms of local, average and stagnation point Nusselt number. The local Nusselt number profiles show that the highest values within the stagnation point region, and the lowest at the end of the heated plate. It is observed that the average Nusselt number increases for increasing nanoparticle concentrations, moreover, the highest values are observed for H/D=5, and a maximum increase of 10% is obtained at a concentration equal to 5%.
基金Financial support for this work was provided by the "National Science Council of Taiwan", under contract NSC 90-2212-E006-125.
文摘This paper presents the two-dimensional analysis for the efficiency of continuous plate fin-tube heat exchangers in staggered and in-lined arrangements under the dry, partially wet, and fully wet conditions for different heat transfer coefficient (h = 20 W/m2K to h = 80 W/m2K) and air relative humidity over the full range from φ= 0 % to φ= 100%. It is shown that the fin efficiencies of the staggered arrangement are higher than those for the in-lined arrangement, and the fully wet fin efficiency is 10~20% lower than that for a dry fin. The conventional 1-D sector method underestimates the fin efficiency up to 4 % as compared to the 2-D analysis.
文摘In this study an incompressible flow with non-Newtonian fluids in the reverse roll coating process was investigated.Non-Newtonian behavior of the coating fluid was accounted by using power law model with power index,n,ranging from 0.8 to 1.2.Effect of roll speed ratio(V2/V1)of the panel roll to the applicator roll and gap distance on the coating film thickness were also investigated.Numerical results were in good agreement with those of experimental data within 15%-20%.Results indicated that the film thickness ratios are function of power-law index,roll speed ration and ratio of roll radius to gap distance.The equations for film thickness ratio were obtained from numerical results as shown below:■,where t1,t2 and t3 are inlet film,transferred film and leakage film thickness,respectively,n is power-law index,V1 and V2 are roll speed of applicator roll and panel roll,Rm is average radius of two rolls and H0 is gap distance.The correlations are accurate within 10%for 0.8≤n≤1.2,0.5≤V_(2)/V_(1)≤2,and 7.7×10^(−5)≤H_(0)/R_(m)≤1.54×10^(−4).
