V. W. Bhatkar^a,*, Anirban Sur^b,*

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-5, 2021, DOI:10.5098/hmt.17.12

Abstract A jet pump or an ejector uses primary fluid flow as motive fluid to entrained secondary fluid. In this paper, the main intention is to find suction flow rate, primary flow rate, secondary flow rate, loss factors and ejector efficiency for an applied pressure. The values of the different loss factors estimated are primary nozzle loss factor (Kp)=0.06, suction loss factor (Ks)=0.04-0.1, mixing loss factor (Km)=0.07-0.1 and diffuser loss factor (Kd)=0.0289. It is found that with the increase in pressure across the ejector, efficiency increases with increase in flow ratio and decrease in pressure ratio. More >

Wei Lin^a, Yongbin Zhang^b,*

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-4, 2022, DOI:10.5098/hmt.18.48

Abstract The cellular membrane of animal has the thickness normally between 5nm and 10nm and has the filtration nanopores with the diameters normally between 0.4nm and 1.2nm. The pressure drop and the critical power loss on the single nanopore for starting the wall slippage have been obtained. The wall slippage is sensitively raised with the pore radius reduction and has a linear dependence on the power loss on the pore. Without wall slippage, the water flow in the pore is much slower than the classical theory calculation; However it is far faster than the classical theory calculation for the wall slippage… More >

Ali Chitsazan^a , Georg Klepp^a, Mohammad Esmaeil Chitsazan^b, Birgit Glasmacher^c

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-6, 2022, DOI:10.5098/hmt.18.17

Abstract For the optimization of the impinging round jet, the pressure force coefficient and drying energy consumption on the moving curved surface are set as the objective functions to be minimized simultaneously. SHERPA search algorithm is used to search for the optimal point from multiple objective tradeoff study (Pareto Front) method. It is found that the pressure force coefficient on the impingement surface is highly dependent on the jet to surface distance and jet angle, while the drying energy consumption is highly dependent on the jet to jet spacing. Generally, the best design study during the multi-objective optimization is found at… More >

Ali Chitsazan^a, Georg Klepp^a, Birgit Glasmacher^b

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-9, 2022, DOI:10.5098/hmt.18.16

Abstract The effect of jet Reynolds number, jet exit angle, the nozzle to surface distance, jet to jet spacing on the heat transfer, and pressure force performance from multiple impinging round jets on a moving curved surface have been numerically evaluated. Two correlations are developed and validated for the average Nu number and the pressure force coefficient and the agreement between the CFD and correlations was reasonable. The surface motion effect becomes more pronounced on the Nu number distribution for low jet Re number, high jet to jet spacing, large jet to surface distance, and angled jets. The pressure force coefficient… More >

Ali Chitsazan^a , Georg Klepp^a, Birgit Glasmacher^b

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-7, 2022, DOI:10.5098/hmt.18.15

Abstract The effect of surface curvature, number of jets, number of jet rows, jet arrangement, crossflow, and surface motion on the heat transfer and pressure force performance from multiple impinging round jets on the moving flat and curved surface have been numerically evaluated. The more number of jets (more than three jets) has no significant effect on the average heat transfer rate. The more number of jet rows increases the strength of wall jets interference and crossflow effects and degrade the average heat transfer rates. There is a minor difference between inline and staggered arrangements on both moving flat and curved… More >

Amnart Boonloi^a, Withada Jedsadaratanachai^b,*

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-13, 2022, DOI:10.5098/hmt.18.2

Abstract This study numerically investigates pressure loss, heat transfer and thermal efficiency in round tube heat exchangers attached with various types of Vrings. A typical type A V-ring is compared with two types of modified V-rings (type B and C). The impacts of blockage ratios, b/D = 0.05, 0.10, 0.15 and 0.20 for all V-ring types in the turbulent region are discussed (Re = 3000 – 20,000). Flow directions in the round pipe attached with the V-rings are varied. The V-apex setting downstream is referred to as “V-Downstream, while the V-apex setting upstream is referred to as “V-Upstream”. The flow and… More >

Ali Chitsazan^a,*, Georg Klepp^a, Birgit Glasmacher^b

Frontiers in Heat and Mass Transfer, Vol.19, pp. 1-8, 2022, DOI:10.5098/hmt.19.35

Abstract The objective of the present research is the prediction of large arrays of impingement jets using a computational model. The heat transfer and the force coefficient from single and multiple jet rows (1, 2, 4, 8, and infinity rows) for two different nozzle shapes as either orifice or straight pipe on a fixed flat surface were numerically investigated for drying applications to understand the physical mechanisms which affect the uniformity of the local heat transfer and pressure force coefficient as well as average heat transfer coefficient. The pipe has always a higher averaged Nu and pressure force coefficient compared to… More >

Wadhah Hussein Al doori^*

Frontiers in Heat and Mass Transfer, Vol.19, pp. 1-9, 2022, DOI:10.5098/hmt.19.8

Abstract Perforated fin forced convection heat transfer is the primary focus of this investigation. The purpose of this research is to see if perforated pin fins can help with heat transmission in the devices. Each pin's perforation diameter and number of holes are rigorously examined. The Nusselt numbers for perforated pins are 47 percent higher than those for solid pins, according to the study, and this number raises as the number of holes increases. The pressure drop is reduced by 19% when perforated pins are used instead of solid pins. Heat transmission in a round-holed pin fin was studied using forced… More >

Mohamed Shaimi^* , Rabha Khatyr, Jaafar Khalid Naciri

Frontiers in Heat and Mass Transfer, Vol.20, pp. 1-14, 2023, DOI:10.5098/hmt.20.23

Abstract This paper presents an exact analytical solution to the extended Graetz problem in microchannels and microtubes, including axial heat conduction, viscous dissipation, and rarefaction effects for an imposed constant wall temperature. The flow in the microchannel or microtube is assumed to be hydrodynamically fully developed. At the same time, the first-order slip-velocity and temperature jump models represent the wall boundary conditions. The energy equation is solved analytically, and the solution is obtained in terms of Kummer functions with expansion constants directly determined from explicit expressions. The local and fully developed Nusselt numbers are calculated in terms of the Péclet number,… More >

Ameer Abed Jaddoa^* , Karema Assi Hamad, Arshad Abdul Jaleil Hameed

Frontiers in Heat and Mass Transfer, Vol.20, pp. 1-9, 2023, DOI:10.5098/hmt.20.18

Abstract In the Heat Transfer process, many innovations were introduced aiming to obtain the most optimum behavior of the cooling process using nanofluids as coolant liquids. These nanofluids have gained much attention in cooling systems due to their special rheological and thermal performance. In this work, an experimental evaluation is conducted for nanofluids Al₂O₃, SiO₂, CuO, ZnO, and TiO₂ nanoparticles applied to a mini-channel. The nanofluid particles were entirely spread out in purified water (size of 15 nm) before being passed to the heat sink through a confined inflow channel. The obtained results showed that the achieved improvement rates are 25%,20%,… More >