Effect of copper nanoparticles on thermal behavior of two-phase argon-copper nanofluid flow in rough nanochannels with focusing on the interface properties and heat transfer using molecular dynamics simulation

A comparison between the efficacy of surface boundary structure and presence of nanoparticles on the condensation two-phase flow inside rough nanochannels has been accomplished by applying molecular dynamics procedure to evaluate the thermal conductivity and flow characteristics.Simulation is performed in a computational region with two copper walls containing rectangular rough elements under different saturated temperatures.The main properties of liquid–vapor interface including density and the number of liquid atoms,are obtained.It is observed that the density profile is more affected by nanoparticles than the roughness.Also,compared to the condensation of nanofluid in a smooth nanochannel,the rough wall causes a greater drop in the temperature at the early time steps and by development of liquid films,effects of the wall roughness reduce.At the first of the condensation process,adding nanoparticle causes that transferring argon particles to the liquid phase increases with a steeper slope.Furthermore,heat current autocorrelation function(HCACF)for nanofluid condensation flow over considered correlation time is analyzed and following that the thermal conductivity for different saturated conditions is calculated.It has been represented that at lower temperatures the roughness makes more significant influence on the heat transfer of two-phase flow,while at higher temperatures the importance of nanoparticles prevails.

Experimental and Numerical Investigation of Impingement Heat Transfer on Target Plate with Streamlined Roughness Element at Maximum Crossflow Condition

A combined experimental and numerical investigation of the heat transfer and flow characteristics of the roughened target plate has been conducted.All the data are compared with the flat plate.Three novel streamlined roughness elements are proposed:similar round protuberance,similar trapezoidal straight rib,and similar trapezoidal curved rib.The experiments are carried out in a perspex model using the transient thermochromic liquid crystal method.The effect of jet Reynolds number,rib height,and rib shape on the Nusselt number and flow discharge coefficient has been investigated.Higher ribs provide higher heat transfer enhancement.The curved ribs provide better heat transfer performance.Within the experimental scope,combined straight rib plate and combined curved rib plate increase the area averaged Nusselt number by 11.5%and 13.8%respectively.The experiment is complemented by a numerical part,which can provide flow field analysis and the Nusselt number on the surface of the small size roughness element.The numerical results show the protuberance can shorten the nozzle to plate distance and make the shifting point move forward.The ribs have a guidance effect on crossflow and reduce the transverse interference to the downstream jet.The transferred heat flux caused by the side surface of the roughness element is very obvious.The heat flux contributed by the side surface of the protuberance and ribs can reach 26%and 10%respectively.