Ammar Hassan Soheel, Omar Mahmood Jumaah, Ahmed Mustaffa Saleem^*

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-7, 2021, DOI:10.5098/hmt.17.21

Abstract This paper presents a simulation and investigation of the heat transfer coefficient, pressure drop, and thermal conductivity of two - phase flow. The simulation was performed of mixtures (Al₂O₃ nanoparticles with R134a refrigerant). The size of nanoparticles (Al₂O₃) which is used in this study is 30 nm and volume concentrations are 0.015 and 0.03. The two – phase flowing through a horizontal circular microchannel of (diameter 100 µm, and length 20 mm) under constant heat flux (3000 W/m²) and constant wall temperature (330 K), also in this study used the inlet temperature at -20 oC and mass flow rates are… More >

Marwa M. Ibrahim^a,*, Mohamed Mahran Kasem^b,c

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-11, 2021, DOI:10.5098/hmt.17.20

Abstract Currently electricity generation technologies by thermal energy conversions become strong demand. The objective of this paper is to present a novel thermal study of absorber/receiver circular pipe of parabolic trough solar collector system for laminar and turbulent (k-ɛ model) fluids flow as well as two-dimensional numerical simulation is performed using CFD ANSYS FLUENT software. Significant improvements in heat transfer and velocity were discovered; the pattern of temperature distribution over the pipe absorber was displayed, and velocity vectors, pressure contours, and temperature contours were studied. The impact of increasing the heat flux towards the pipe wall is discussed. Heat transfer coefficient… More >

Emad D. Aboud¹ , Qusay Rasheed Al-Amir², Hameed K. Hamzah², Ammar Abdulkadhim³, Mustafa M. Gabir³, Salwan Obaid Waheed Khafaji², Farooq H. Ali^2,*

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-17, 2021, DOI:10.5098/hmt.17.19

Abstract The natural convection of nanofluid flow, which occurs between a sinusoidal-corrugated enclosure and a concentric inner cylinder has been numerically investigated. The two horizontal walls of this enclosure are considered adiabatic and two vertical corrugated walls are held at a constant value of the cold temperature while the inner concentric cylinder is heated isothermally. Different cylinder geometries (i.e, circular, square, rhombus, and triangular) located inside the enclosure are examined to find the best shape for optimum heat transfer. The physical and geometrical parameters influencing heat transfer are Rayleigh number (Ra=10³ -10⁶), undulation numbers (N=0,1 and 2), aspect ratios (AR=5, 2.5… More >

Shuang Cao^a,*, Hui Yang^a, Luxing Zhao^a, Tao Wang^a, Jian Xie^b,†

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-16, 2021, DOI:10.5098/hmt.17.17

Abstract Flow boiling heat transfer is an effective way to fulfill the energy transfer. The wettability of boiling surface influences the liquid spreading ability and the growth, departure, and release frequency of bubbles, which determines the heat transfer performance. According to the wettability and combination forms, boiling surface are classified into weak wetting surface, strong wetting surface, and heterogeneous wetting surface. Fabricating by physical, chemical method or coating the original surface with a layer of low surface energy, the weak wetting surface has more effective activation point and nucleation center density to improve heat transfer performance at low heat flux. The… More >

Jingquan Zhang^a,b, Kun Zhang^a,b,*

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-6, 2021, DOI:10.5098/hmt.17.14

Abstract Detailed numerical analysis is presented for flow and heat transfer in sinusoidal-corrugated parallel channel with six discrete heat sources placed under the bottom surface. Three dimensional numerical model are applied for simulating the flow and heat transfer process and the Colburn j factor is applied to evaluate the overall performance of the corrugated liquid cooled channel. The results show that the maximum temperature in the middle section decreases and the pressure loss increases as the wavelength of sinusoidal surface on the bottom decreases, while the increasing wave amplitude of corrugated surface can enhance the heat transfer rate in the ranges… More >

Olanrewaju M. Oyewola^a,b,*, Samuel I. Afolabi^b , Olawale S. Ismail^b

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-8, 2021, DOI:10.5098/hmt.17.11

Abstract The problem of natural convection in rectangular cavities with different aspect ratios has been numerically analyzed in this study. Cavities considered have their right vertical walls heated and cooled at the opposite with constant temperatures, while horizontal walls are kept adiabatic. The objective of this study is to ascertain the significant effects of Rayleigh numbers (Ra), Nusselt numbers (Nu) and aspect ratios (AR) on flow and heat transfer in rectangular cavities. The equations of Navier-Stokes and energy are solved by applying Galerkin weighted residual Finite Element Method. Parametric calculations are performed for Rayleigh numbers (Ra) ranging from 104 to 108… More >

Zhiyun Wang^*, Ziqing Wang, Mo Yang

Frontiers in Heat and Mass Transfer, Vol.17, pp. 1-7, 2021, DOI:10.5098/hmt.17.10

Abstract This paper presents a two-dimensional fluid-structure interaction numerical simulation of fluid flow over two horizontal heat exchange cylinders affected by a flapping reed in a domain. The reed is a thin flexible sheet made of elastic material with one end fixed on the trailing edge of the upstream cylinder. The effects of the reed length and the cylinder spacing on the periodic oscillations of the reed, the flow field and the heat transfer of the downstream cylinder. The results show that the oscillation of the reed in this paper is a single-period oscillate model. Compared to the case of cylinder… More >

Husam Abdulrasool Hasan^a,*, Jenan S. Sherza^a, Lammiaa Abdulrudah Abd^a, Kayser Aziz Ameen^a, Azher M. Abed^b, Ali Arif hatem^a, Kamaruzzaman Sopian^c

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-8, 2022, DOI:10.5098/hmt.18.45

Abstract In a Fresnel-based Concentrated Photovoltaic system, multi junction solar cells suffer from increased PV temperature, resulting in a decrease its electrical efficiency. This study design to investigate the influence of using Water/Al₂O₃ Nanofluid as cooling fluid on heat transfer enhancement and top surface temperature for multi-junction solar cell in the Fresnel-based Concentrated Photovoltaic thermal CPVt System. The CFD simulation was conducted on mini-channel under the concentrated multi-junction solar cell with using water/Al₂O₃ Nanofluid and pure water as coolant fluids. The Reynolds number is in the range of 15000-30000 were examined. The average Nusselt numbers augmented through increasing Reynolds numbers. The… More >

E. Flilihi^a,† , E. H. Sebbar^a, D. Achemlal^a, T. EL Rhafiki^a, M. Sriti^b, E. Chaabelasri^c

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-6, 2022, DOI:10.5098/hmt.18.39

Abstract In this paper, we made a numerical simulation of convective heat transfer in a rectangular section pipe of a air flat plate solar collector using three forms of the absorber plate namely, simple shape, rectangular-shape, and half circle-shape. The flow is considered laminar and stationary, where the heat exchange between the absorber plate and the fluid takes place in useful area. The computer code in fluid dynamics, the fluent, is applied to integrate the governing equations on each control volume. A detailed description of the fluid flow and heat transfer in the rectangular channel was made. Several simulation were carried… More >

Scott Wahlquist^a, Amir Ali^a,b,*, Su-Jong Yoon^c, Piyush Sabharwall^c

Frontiers in Heat and Mass Transfer, Vol.18, pp. 1-8, 2022, DOI:10.5098/hmt.18.35

Abstract The heat transfer performance of a novel tube configuration that combines the swirling velocity induced by oval-twisting and secondary flow generated by a helical geometrical flow path is presented. The Nusselt number (Nu) and friction factor (f) are compared for the laminar flow regime (Re = 250- 2000) under isothermal wall conditions. Under the same flow and boundary conditions, the oval-twisted helical tube increased the Nu and slightly increased the f over the circular helical tube. The best performance with the highest Nuand lowest f occurs at the coil curvature ratio (d_h/D) of 0.17. The quantified enhancement performance factor (h)… More >