n-Hexane isomerization over copper oxide-promoted sulfated zirconia supported on mesoporous silica

Copper oxide-promoted sulfated zirconia (CuSZ) was supported on MCM-41 by the direct impregnation method. n-Hexane isomerization was investigated over the CuSZ/MCM-41 catalysts. 2-MP, 3-MP and 2,3-DMB are the major isomerization products, besides a small amount of 2,2-DMB. The product distribution is comparable to that reported for Pt based catalysts. The optimal CuO loading in these catalysts calcined at 700 °C is around 3.2 wt% and only leads to the formation of catalytic active metastable tetragonal ZrO₂. The improved performance of CuO-promoted SZ/MCM-41 is a trade-off between the sulfur amount and the content of tetragonal ZrO₂ phase.     

A semi-empirical correlation for adiabatic interfacial friction factor in horizontal air-water countercurrent stratified flow

A semi-empirical correlation for an adiabatic interfacial friction factor(f_ia) in a stratified wavy flow, based on the simultaneous measurements of the main flow parameters in air-water countercurrent stratified flows and the concept of surface roughness in a wavy flow, has been developed. The functional form for f_ia, in particular, has been obtained by making an analogy between the effect of surface roughness on the gas-to-wall friction factor(f_g) in a pipe flow and the effect of gas-water interface roughness on the air-water interface friction factor (f_ia) in a wavy flow. A total of 186 data points from the present countercurrent flow test and 15 from the concurrent pipe flow reported by others have been used in the present analysis. Comparisons between the data and the predictions of the present correlation shows that the agreement is within ±30%.     

Temperature distributions along the absorber of the axicon solar fluid heater

Mathematical formulae are derived to express the fluid and the absorber-wall temperatures as functions of the position along the absorber reckoned from the inlet. The expressions are put in a general form in terms of a limited number of dimensionless groups. Two types of flow arrangements are identified, namely counter flow and parallel flow. The counter-flow heater is always superior to the parallet-flow one because it yields a higher output temperature under all conditions. The effects of the various parameters on the fluid temperature at the exit from the heater are investigated. Consequently, different methods of elevating the output temperature are proposed.     

Evaluation of Shell and Tube Heat Exchanger Performance by Using ZnO/Water Nanofluids

To examine and investigate the impact of nanofluid on heat exchanger performance, including the total heat transfer, the effect of friction factor, the average Nusselt number, and the thermal efficiency, the output heat transfers of a shell and tube heat exchanger using ZnO nanoparticles suspended in water has been conducted numerically. The governing equations were solved using finite volume techniques and CFD simulations with ANSYS/FLUENT Solver 2021. The nanoparticles volume fractions adopted...