Yuming Zhao¹, Jing Wang¹, Bin Sun², Zhenshang Wang¹, Huashan Li², Jiongcong Chen^2,*

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 1171-1188, 2024, DOI:10.32604/fhmt.2024.054594

Abstract Data centers (DCs) are highly energy-intensive facilities, where about 30%–50% of the power consumed is attributable to the cooling of information technology equipment. This makes liquid cooling, especially in two-phase mode, as an alternative to air cooling for the microprocessors in servers of interest. The need to meet the increased power density of server racks in high-performance DCs, along with the push towards lower global warming potential (GWP) refrigerants due to environmental concerns, has motivated research on the selection of two-phase heat transfer fluids for cooling servers while simultaneously recovering waste heat. With this regard,… More >

Haowei Hu^1,2,*, Qi Wang¹, Xinnuo Chen¹, Qin Li³, Mu Du⁴, Dong Niu^5,*

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 1245-1259, 2024, DOI:10.32604/fhmt.2024.054223

Abstract To investigate the microscopic mechanism underlying the influence of surface-chemical gradient on heat and mass recovery, a molecular dynamics model including droplet condensation and transport process has been developed to examine heat and mass recovery performance. This work aimed at identify optimal conditions for enhancing heat and mass recovery through the combination of wettability gradient and nanopore transport. For comprehensive analysis, the structure in the simulation was categorized into three distinct groups: a homogeneous structure, a small wettability gradient, and a large wettability gradient. The homogeneous surface demonstrated low efficiency in heat and mass transfer, More >

Haowei Hu^1,2,*, Xinnuo Chen¹, Qi Wang¹, Qin Li³, Dong Niu⁴, Mu Du^5,*

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 1071-1085, 2024, DOI:10.32604/fhmt.2024.054218

Abstract The self-driven behavior of droplets on a functionalized surface, coupled with wetting gradient and wedge patterns, is systematically investigated using molecular dynamics (MD) simulations. The effects of key factors, including wedge angle, wettability, and wetting gradient, on the droplet self-driving effect is revealed from the nanoscale. Results indicate that the maximum velocity of droplets on hydrophobic wedge-shaped surfaces increases with the wedge angle, accompanied by a rapid attenuation of driving force; however, the average velocity decreases with the increased wedge angle. Conversely, droplet movement on hydrophilic wedge-shaped surfaces follows the opposite trend, particularly in terms… More >

Zhenzhen Liu, Hua Zhang^*, Zilong Wang, Yugang Zhao

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 1087-1105, 2024, DOI:10.32604/fhmt.2024.053851

Abstract The exploration of performance and prediction of environmentally friendly refrigerant physical properties represents a critical endeavor. Equilibrium molecular dynamics simulations were employed to investigate the density and transport properties of propane and ethane at ultra-low temperatures under evaporative pressure conditions. The results of the density simulation of the evaporation conditions of the blends proved the validity of the simulation method. Under identical temperature and pressure conditions, increasing the proportion of R170 in the refrigerant blends leads to a density decrease while the temperature range in which the gas-liquid phase transition occurs is lower. The analysis More >

Ahmed Mustaffa Saleem, Abdullah A. Badr, Bahjat Hassan Alyas, Omar Rafae Alomar^*

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 1231-1244, 2024, DOI:10.32604/fhmt.2024.053770

Abstract This study numerically involves the performance of thermal insulation of different types of composite walls and roofs to demonstrate the best model that can be used for energy-efficient building construction in Iraq. The mathematical model is solved by building its code using the Transmission Matrix Method in MATLAB software. The weather data of 21st July 2022 in Baghdad City/Iraq is selected as a test day. The wall types are selected: the first type consists of cement mortar, brick, and gypsum, the second type consists of cement mortar, brick, gypsum, and plaster and the third type… More >

Zhisheng Xu¹, Juan Wang¹, Zihan Yu¹, Jiaming Zhao^2,*

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 1129-1151, 2024, DOI:10.32604/fhmt.2024.053695

Abstract Called island-crossing tunnels, some specific underwater tunneling projects face constraints imposed by geological and water conditions, necessitating their passage through artificial or natural islands. The longitudinal of the tunnel follows a W-shaped distribution. The congestion situation does not allow for immediate longitudinal smoke exhaust at the early stage of the fire, and the natural spread of smoke is complicated. An exhaustive investigation was carried out to analyze the smoke behaviors during a fire incident, employing the fire dynamics software FDS, considering five slopes and four fire locations. The simulation results reveal that the layer of… More >

Liang Yi, Zhiqiang Lei, Zhisheng Xu, Yaolong Yin, Houlin Ying^*

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 977-996, 2024, DOI:10.32604/fhmt.2024.053688

Abstract This paper explores the smoke flow characteristics in tunnel fires, giving a particular emphasis on the effects of different distances between the smoke outlets and the fire source. It examines the smoke behavior under different conditions, including variations in heat release rates, exhaust volumetric flow rates, spacing between smoke outlets, and the longitudinal fire source positions. Results indicate that altering the fire source positions and the smoke outlets in the tunnel leads to variations in the properties of smoke flow both the fire source upstream and downstream; the distance between fire source and smoke outlet… More > Graphic Abstract

Bo Zhang¹, Yunxie Huang², Peilin Cui², Zhiguo Wang¹, Duo Ding¹, Zhenhai Pan³, Zhenyu Liu^2,*

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 997-1016, 2024, DOI:10.32604/fhmt.2024.053592

Abstract The high surface area of porous media enhances its efficacy for evaporative cooling, however, the evaporation of pure substances often encounters issues including local overheating and unstable heat transfer. To address these challenges, a volume of fluid (VOF) model integrated with a species transport model was developed to predict the evaporation processes of ternary mixtures (water, glycerol, and 1,2-propylene glycol) in porous ceramics in this study. It reveals that the synergistic effects of thermal conduction and convective heat transfer significantly influence the mixtures evaporation, causing the fluctuations in evaporation rates. The obtained result shows a More >

Jawad Raza¹, F. Mebarek-Oudina^2,*, Haider Ali¹, I. E. Sarris³

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 1017-1041, 2024, DOI:10.32604/fhmt.2024.052749

Abstract The current study is dedicated to presenting the Casson nanofluid over a stretching surface with activation energy. In order to make the problem more realistic, we employed magnetic field and slip effects on fluid flow. The governing partial differential equations (PDEs) were converted to ordinary differential equations (ODEs) by similarity variables and then solved numerically. The MATLAB built-in command ‘bvp4c’ is utilized to solve the system of ODEs. Central composite factorial design based response surface methodology (RSM) is also employed for optimization. For this, quadratic regression is used for data analysis. The results are concluded More > Graphic Abstract

Yangyiming Rong¹, Weitao Su¹, Shuai Wang², Bowen Du¹, Jianjian Wei², Shaozhi Zhang^2,*

Frontiers in Heat and Mass Transfer, Vol.22, No.4, pp. 1209-1229, 2024, DOI:10.32604/fhmt.2024.052415

Abstract Finned-tube heat exchanger (FTHE) is often used as an evaporator in commercial products of separated heat pipe (SHP). The working conditions of FTHE in gravity-assisted SHP are significantly different from those working in refrigerators and air conditioners. Although FTHE is widely used in commercial products of SHP, previous research on its characteristics is very limited. In this paper, a mathematical model for a SHP with FTHE as the evaporator and plate heat exchanger as the condenser is established and verified with experiments. Parametric analyses are carried out to investigate the influences of evaporator design parameters:… More >