Obed Y.W. Abotsi, John P. Kizito^*

Frontiers in Heat and Mass Transfer, Vol.14, pp. 1-6, 2020, DOI:10.5098/hmt.14.24

Abstract In this paper, turbulent water flow and heat transfer are studied numerically in a pipe which is rotating about its longitudinal axis. Computations were conducted for axial Reynolds numbers ranging from 10000 to 30000 at different rotation rates. Rotation rate (N) is the ratio of the rotational Reynolds number to the axial Reynolds number. Predictions showed that the Nusselt number (Nu) of the stationary pipe (N=0) was augmented by 50-58% at N=5, 105-132% at N=10, 150-201% at N=15, 208-265% at N=20, and 320-373% at N=30. Improvements in the heat transfer rate was linked to the introduction of tangential velocity components… More >

Hao Guo^a , Xianbing Ji^a,b,1 , Jinliang Xu^a,b

Frontiers in Heat and Mass Transfer, Vol.14, pp. 1-16, 2020, DOI:10.5098/hmt.14.14

Abstract With fast development of electronic devices, novel strategies of thermal management have been received great attention to dissipate high heat fluxes. As an efficient heat transfer device, loop heat pipe (LHP) provides ideal solution for such purpose. Even though LHP was invented nearly half-century ago, challenges still exist on its design, fabrication and operation. The objective of this paper is to present a thorough review on LHPs, paying more attention on the working principle, advantage and configuration. The review is performed in three aspects. First, the macroscopic operation characteristics such as start-up, temperature fluctuations and anti-gravity operation are described. Second,… More >

Wenlei Lian, Zijian Sun, Taoyi Han, Yimin Xuan^*

Frontiers in Heat and Mass Transfer, Vol.14, pp. 1-6, 2020, DOI:10.5098/hmt.14.10

Abstract An experimental facility is developed to investigate the characteristics of the nucleate boiling heat transfer in a rotating water film. The High speed photography technique is used to visualize the flow field of the rotating water film. Along with the bubble photographs, the centrifugal acceleration, heat flux into the film, and the heat transfer coefficient are calculated to learn the heat transfer characteristics of the water film. It is found that the boiling heat transfer coefficient decreases with the increment of heat flux. The heat transfer coefficient increases with acceleration increasing from 20g to 60g, but show no obvious increase… More >

S. Anand^a, S. Suresh^a, R. Dhanuskodi^b, D. Santhosh Kumar^b,*

Frontiers in Heat and Mass Transfer, Vol.14, pp. 1-9, 2020, DOI:10.5098/hmt.14.8

Abstract The present work investigates the wall temperature prediction at supercritical pressure of water by CFD and compares the prediction of CFD and that of 11 empirical correlations available in literature. Supercritical-water heat transfer experimental data, covering a mass flux range of 400-1500 kg/m²s, heat flux range of 150-1000 kW/m², at pressure 241 bar and diameter 10 mm tube, were obtained from literature. CFD simulations have been carried out for those operating conditions and compared with experimental data. Around 362 experimental wall temperature data of both heat transfer enhancement and heat transfer deterioration region have been taken for comparison. A visual… More >

Zijie Chen^a , Sanat Modak^a, Massoud Kaviany^a,* , Richard Bonner^b

Frontiers in Heat and Mass Transfer, Vol.14, pp. 1-11, 2020, DOI:10.5098/hmt.14.1

Abstract In dropwise condensation on vertical surface, droplets grow at nucleation sites, coalesce and reach the departing diameter. In biphilic surfaces, when the hydrophobic domain is small, the maximum droplet diameter is controlled by the shortest dimension where the droplets merge at the boundary. Through direct numerical simulations this size-effect heat transfer coefficient enhancement is calculated. Then the 1-D biphilic surface is optimized considering the size-dependent hydrophilic domain partial flooding (directly simulated as a liquid rivulet and using the capillary limit), the subcooling (heat flux) and condenser length effects. The predicted performance is in good agreement with the available experiments. More >

Firas Aziz Ali^a,*, Adnan M. Alsaffawi^b , Karam Hashim Mohammed^a

Frontiers in Heat and Mass Transfer, Vol.15, pp. 1-7, 2020, DOI:10.5098/hmt.15.21

Abstract The augmentation of the heat transfer in heat exchangers is one of the methods to increase efficiency of the system. The double tube heat exchanger is selected to many suitable techniques of heat transfer enhancement. In this study; the friction factor and heat transfer coefficient of double tube is evaluated experimentally. The Al₂O₃ nanoparticles dispersed in ethylene glycol (EG) with a diameter 50 nm and the weight concentration (0.1%, 0.3%, 0.5%, 0.7%, 1%) has been utilized. Then the effect of parallel current and counter current with different ranges of Reynolds number (10,000 to 30,000) on the friction factor and heat… More >

N. Govindaraj, A. K. Singh, Pankaj Shukla

Frontiers in Heat and Mass Transfer, Vol.15, pp. 1-8, 2020, DOI:10.5098/hmt.15.20

Abstract A numerical study of fluid flow over stretching sheet with temperature dependent properties has been performed induced by mixed convection. The significant variation of the Prandtl number and viscosity in the temperature is observed [see table 1]. Viscosity and Prandtl number are vary in inverse of the linear function. The physical problem modeled in the mathematical equations in dimension form, which is converted to the non-dimensional equations by applying similarity transformations and suitable boundary conditions. The mathematical modelling problem is transformed PDE’s are numerically solved using Quasilinearization technique and FDM. The current numerical data has been presented in terms of… More >

Wakana Hiratsuka^a , Takashi Fukue^b,*, Hidemi Shirakawa^c, Katsuyuki Nakayama^d, Yasushi Koito^e

Frontiers in Heat and Mass Transfer, Vol.15, pp. 1-8, 2020, DOI:10.5098/hmt.15.16

Abstract This paper describes a possibility of heat transfer enhancement in a mm-scale flow channel by using a combination of some projections and pulsating flow. The objective of this research is to develop a novel heat exchanger for miniaturized productions such as high-density packaging electronic equipment by applying pulsating flow to enhance heat transfer while inhibiting an increase of pressure drop. In order to evaluate the possibility of applying pulsating flow to miniature water channels, a three-dimensional flow and heat transfer analysis was performed. Heat transfer performance of a combination of pulsating water flow and a projection was investigated. The mechanism… More >

Teng Huang^a,* , Xuefang Li ^a,† , Lin Cheng^b,‡

Frontiers in Heat and Mass Transfer, Vol.15, pp. 1-8, 2020, DOI:10.5098/hmt.15.15

Abstract As a non-flammable, non-toxic refrigerant, supercritical CO₂ (ScCO₂) has been increasingly used for heat transfer applications. In this study, the ScCO₂ flow and heat transfer in a set of full-size three-dimensional serpentine tubes were modeled with different inner diameters and tube pitches. The standard k-epsilon model was used for the turbulence modeling. The results show the effect of the different tube inner diameters and tube pitches on the flow and heat transfer of ScCO₂ for a given flow flux or inlet Reynolds number. The heat transfer coefficient decreases as both the tube pitch and the inner diameter increase for a… More >

Muhammad Nazim Tufail^a , Musharafa Saleem^a,b,*, Qasim Ali Chaudhry^b,†

Frontiers in Heat and Mass Transfer, Vol.15, pp. 1-10, 2020, DOI:10.5098/hmt.15.14

Abstract This methodology presented the unsteady three-dimensional laminar flow since Hall effects inducing the cross flow in z-axis. The boundary layer and the low magnetic Reynolds number approximations are used to simplify the system of equations derived from the constitutive laws. The upper-convected Maxwell (UCM) fluid model used for Hall effects with unsteady heat transfer, which passed through the infinite stretching sheet. This flow model has intensified with the effects of magnetohydrodynamic (MHD), thermal radiation and heat generation-absorption. Here, we selected the two-parameter Lie scaling transformations to convert the highly non-linear partial differential equations (PDEs) to the ordinary differential equations (ODEs)… More >