Article
Thermodynamics
Ahmet Umit Tepe
Summary: This study investigated the effect of a newly proposed punched triangular ramp vortex generator on heat transfer performance for a fin-tube heat exchanger through numerical simulations. The results showed that the ramp angle had a more significant influence on thermo-hydraulic performance compared to ramp height.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2021)
Article
Thermodynamics
Nuthvipa Jayranaiwachira, Pongjet Promvonge, Chinaruk Thianpong, Pitak Promthaisong, Sompol Skullong
Summary: The study investigates the enhancement of convection in a tube heat exchanger using louvered curved-baffle vortex generator (VG). The results show that the LCB-inserted tube has larger Nu and f values compared to a plain tube, with Nu and f increasing as PR and theta decrease. The LCB increases Nu and f by approximately 2.59-4.66 and 3.8-39.37 times, respectively. Empirical correlations for Nu and f fit the measured data well, with discrepancies of +/- 9% and +/- 10%, respectively.
CASE STUDIES IN THERMAL ENGINEERING
(2023)
Article
Chemistry, Physical
Wei Luo, Zirong Yang, Kui Jiao, Yanyi Zhang, Qing Du
Summary: Heat management is crucial to the stable and high-efficiency operation of proton exchange membrane fuel cell (PEMFC) system. Traditional fin-tube heat exchangers require further optimizations to be applicable to PEMFC vehicles. Novel structural designs using wavy-louvred fin and vortex generators have been investigated, showing different effects on heat transfer coefficient and pressure drop, as well as enhancement mechanisms revealed through temperature, velocity, and pressure distribution analysis.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Thermodynamics
Soheil Asaadi, Hamid Abdi
Summary: The heat transfer enhancement in plate-fin heat exchangers using vortex generators with different nanoparticle volume fractions was numerically simulated. Results showed that using nanofluid can increase heat transfer coefficient by 20% and pressure drop by 18% compared to pure water. Among the vortex generator types, MDWP2 exhibited the highest heat transfer performance but also led to the highest pressure drop in the studied range of Reynolds number.
JOURNAL OF THERMAL ANALYSIS AND CALORIMETRY
(2021)
Article
Thermodynamics
Weihao Ling, Jingtao Wu, Xuan Li, Jianjun Ma, Yu Ding, Bingcheng Li, Min Zeng
Summary: A three-dimensional frost growth model of microchannel louvered fins is established and verified using OpenFOAM software to study the growth and distribution of frost layer on the surface of MHX. The effects of boundary conditions, such as moist air inlet velocity, humidity ratio, and cold-wall surface temperature, on the thickness of the local frost layer, pressure drop, and outlet temperature of the microchannel louvered fins are explored. This study provides guidance for predicting local frosting of MHXs under moist conditions.
Article
Thermodynamics
Zhenfei Feng, Ping Jiang, Siyao Zheng, Qingyuan Zhang, Zhen Chen, Fangwen Guo, Jinxin Zhang
Summary: A new insertion-type longitudinal vortex generator (ITLVG) is designed to enhance heat transfer in micro/mini-channel thermal systems. The effects of ITLVG length and arrangement on flow and heat transfer characteristics in a square minichannel are explored using experimental and numerical methods. Results show that ITLVG generates vortex flow and reduces thermal boundary layer, leading to significant improvement in heat transfer. The ITLVG arrangement has a significant effect on flow and heat transfer, while the ITLVG length has a slight effect. The ITLVG with a length of 20 mm and arranged simultaneously in upstream, midstream, and downstream shows the highest performance evaluation criterion (PEC) values.
Article
Energy & Fuels
Junjie Zhao, Bin Zhang, Xiaoli Fu, Shenglin Yan
Summary: This study focuses on the impact and optimization of vortex generators in radiators on the ends of motor coils, concluding that a 45-degree attack angle generator is most effective. Results show that FD with a longitudinal distance of 4 h performs well at Reynolds numbers below 4000, while FU-4 h-0.5 h is more prominent at higher Reynolds numbers.
Article
Thermodynamics
Jinglong Zhang, Xingjun Hu, Yufei Luo, Zheng Hui, Jingyu Wang, Tianming Yu
Summary: In this study, a novel composite heat transfer enhancement technique combining louvered fins and rectangular wing vortex generators (RWVGs) is proposed to improve the thermal-hydraulic performance of louvered fin and flat tube heat exchangers (LFHEs). Experimental and numerical methods are used to investigate the effects of RWVG parameters on the LFHE performance. The results show that the thermal-hydraulic performance of the LFHE is significantly improved with the optimal RWVG parameters.
JOURNAL OF THERMAL SCIENCE
(2023)
Article
Thermodynamics
Chunhua Min, Haizhu Li, Xiaomeng Gao, Kun Wang, Liyao Xie
Summary: This paper proposed a novel method to improve heat exchanger thermal performance by combining vortex generators and twisted belts, with numerical studies on circular tube thermo-hydraulic characteristics to determine optimal parameters. The results showed that using a combination of staggered arrangement, optimal twist ratio of 4, attack angle of 75 degrees, and pitch of 1.5D can significantly enhance the heat exchanger performance.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2021)
Article
Energy & Fuels
Pongjet Promvonge, Pitak Promthaisong, Sompol Skullong
Summary: A vortex generator was tested and investigated in this study to improve the thermal performance of a solar heat exchanger duct. Experimental and numerical methods were used to understand its flow and thermal patterns, and optimal configurations were determined.
Article
Thermodynamics
Zhongjie Lu, Mingjie Li, Chenlong Yang, Xiangqiang Cheng, Jianfei Zhang
Summary: This study investigates the application of longitudinal vortex generators (LVGs) in 3D stacked chip micro gaps to enhance heat transfer. Experimental and numerical tests are conducted to examine the performance of 3D stacked chip with and without LVGs, and the flow and heat transfer performance under different mass flow rates, heating powers, and LVG spacings are investigated. The results indicate that the LVGs array effectively improves the cooling performance of the chip, reducing the wall temperature by 14.49 degrees C compared to a smooth channel. Reducing the spacing of the longitudinal vortex array enhances the cooling performance but also increases pressure drop. The comprehensive heat transfer performance comparison suggests that the LVGs enhanced chip is more suitable for higher heating powers, while chips with smaller spacing are more suitable for lower flow rates of cooling water.
CASE STUDIES IN THERMAL ENGINEERING
(2023)
Article
Thermodynamics
Pongjet Promvonge, Pitak Promthaisong, Sompol Skullong
Summary: The article investigates the effect of insertion of louvered V-winglet (LVW) vortex generators on convection heat transfer and pressure loss in a tubular heat exchanger. The experimental result shows that among the LVWs, the case of R-P=0.5, theta=10 degrees provides the largest friction factor and Nusselt number.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2022)
Article
Thermodynamics
Lijun Wang, Bingyu Chen, Yuncong Jiang, Xiaokang Yan
Summary: The study compared the heat transfer capacity of concave VG, convex VG, and trapezoidal VG, with concave VG found to have a more reasonable heat transfer capacity, enhancing heat transfer efficiency and reducing resistance loss. Nusselt number (Nu) has a strong correlation with volume averaged turbulent dissipation rate and wall shear stress, with a correlation coefficient of 0.935.
INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER
(2021)
Article
Green & Sustainable Science & Technology
Yahya Sheikhnejad, Seyed Abdolreza Gandjalikhan Nassab
Summary: The study aims to enhance the performance of planar solar chimneys by using vortex generation technique to convert more solar radiation into air enthalpy, with a passive vortex generator employed for heat transfer enhancement. Numerical results show that the natural vibration of elastic vortex generator induces moving vortices into the flow field, leading to improved natural convection heat transfer and significantly enhancing the performance of the air heater.
Article
Thermodynamics
Pongjet Promvonge, Smith Eiamsa-ard, Sompol Skullong, Naoki Maruyama, Masafumi Hirota
Summary: An experiment was conducted to investigate the effectiveness of inserting a louver-punched trapezoidal-winglet into a heat-fluxed tube to create a longitudinal vortex generator. The study aimed to optimize thermal performance and reduce heat exchanger sizes. The experimental results showed significant improvements in friction factor and Nusselt number compared to a plain tube.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2023)
Article
Thermodynamics
Mahsa Taghavi, Swapnil Sharma, Vemuri Balakotaiah
Summary: This study investigates the natural convection effects in the insulation layers of spherical storage tanks and their impact on the tanks' performance. The permeability and Rayleigh number of the insulation material are considered as key factors. The results show that as the Rayleigh number increases, new convective cells emerge and cause the cold boundary to approach the external hot boundary. In the case of large temperature differences, multiple solutions may coexist.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Jinyang Xu, Fangjun Hong, Chaoyang Zhang
Summary: This study introduces a self-induced jet impingement device for enhancing pool boiling performance in high power electronic cooling. Through visualization and parametric investigations, the effects of this device on pool boiling performance are studied, revealing the promotion of additional liquid supply and vapor exhausting. The flow rate of the liquid jet is found to positively impact boiling performance.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Wenchao Ke, Yuan Liu, Fissha Biruke Teshome, Zhi Zeng
Summary: Underwater wet laser welding (UWLW) is a promising and labor-saving repair technique. A thermal multi-phase flow model was developed to study the heat transfer, fluid dynamics, and phase transitions during UWLW. The results show that UWLW creates a water keyhole, making the welding environment similar to in air laser welding.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Xingrong Lian, Lin Tian, Zengyao Li, Xinpeng Zhao
Summary: This study investigates the heat transfer mechanisms in natural fiber-derived porous structures and finds that thermal radiation has a significant impact on the thermal conductivity in low-density regions, while natural convection rarely occurs. Insulation materials derived from micron-sized natural fibers can achieve minimum thermal conductivity at specific densities. Strategies to lower the thermal conductivity include increasing porosity and incorporating nanoscale pores using nanosize fibers.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Yasir A. Malik, Kilian Koebschall, Stephan Bansmer, Cameron Tropea, Jeanette Hussong, Philippe Villedieu
Summary: Ice crystal icing is a significant hazard in aviation, and accurate modeling of sticking efficiency is essential. In this study, icing wind tunnel experiments were conducted to quantify the volumetric liquid water fraction, sticking efficiency, and maximum thickness of ice layers. Two measurement techniques, calorimetry and capacitive measurements, were used to measure the liquid water content and distribution in the ice layers. The experiments showed that increasing wet bulb temperatures and substrate heat flux significantly increased sticking efficiency and maximum ice layer thickness.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Jinqi Hu, Tongtong Geng, Kun Wang, Yuanhong Fan, Chunhua Min, Hsien Chin Su
Summary: This study experimentally examined the heat dissipation of vibrating fans and demonstrated its inherent mechanism through numerical simulation. The results showed that the flow fields induced by the vibrating blades exhibited pulsating features and formed large-scale and small-scale vortical structures, significantly improving heat dissipation. The study also identified the impacts of different blade structures and developed a trapezoidal-folding blade, which effectively reduced the maximum temperature of the heat source and alleviated high-temperature failure crisis.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Dan-Dan Su, Xiao-Bin Li, Hong-Na Zhang, Feng-Chen Li
Summary: The boiling heat transfer of low-boiling-point working fluid is a common heat dissipation technology in electronic equipment cooling. This study analyzed the interfacial boiling behavior of R134a under different conditions and found that factors such as the initial thickness of the liquid film, solid-liquid interaction force, and initial temperature significantly affect the boiling mode and thermal resistance.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Jinyi Wu, Dongke Sun, Wei Chen, Zhenhua Chai
Summary: A unified lattice Boltzmann-phase field scheme is proposed to simulate dendrite growth of binary alloys in the presence of melt convection. The effects of various factors on the growth are investigated numerically, and the model is validated through comparisons and examinations.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Shaokun Ge, Ya Ni, Fubao Zhou, Wangzhaonan Shen, Jia Li, Fengqi Guo, Bobo Shi
Summary: This study investigated the temperature distribution of main cables in a suspension bridge during fire scenarios and proposed a prediction model for the maximum temperature of cables in different lane fires. The results showed that vehicle fires in the emergency lane posed a greater thermal threat to the cables.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Shuang-Ying Wu, Shi-Yao Zhou, Lan Xiao, Jia Luo
Summary: This paper investigates the two-phase flow and heat transfer characteristics of low-velocity jet impacting on a cylindrical surface. The study reveals that the heat transfer regimes are non-phase transition and nucleate boiling with the increase of heat transfer rate. The effects of jet impact height and outlet velocity on local surface temperatures are pronounced at the non-phase transition stage. The growth rates of heat transfer rate and liquid loss rate increase significantly from the non-phase transition to nucleate boiling stage.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Emad Hasani Malekshah, Wlodzimierz Wlodzimierz, Miros law Majkut
Summary: Cavitation has significant practical importance and can be controlled by air injection. This study investigates the natural to ventilated cavitation process around a hydrofoil through numerical and experimental methods. The results show that the location and rate of air injection have a meaningful impact on the characteristics of cavitation.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Feriel Yahiat, Pascale Bouvier, Antoine Beauvillier, Serge Russeil, Christophe Andre, Daniel Bougeard
Summary: This study explores the enhancement of mixing performance in laminar flow equipment by investigating the generation of chaotic advection using wall deformations in annular geometries. The findings demonstrate that the combined geometry can achieve perfect mixing at various Reynolds numbers.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Hui He, Ning Lyu, Caihua Liang, Feng Wang, Xiaosong Zhang
Summary: This study investigates the condensation, frosting, and defrosting processes on superhydrophobic surfaces with millimeter-scale structures. The results reveal that the structures can influence the growth and removal of frost crystals, with the bottom grooves creating a frost-free zone and conical edges promoting higher frost crystal heights. Two effective methods for defrosting are observed: hand-lifting the groove and airfoil retraction contraction on protruding structures. This research provides valuable insights into frost formation and defrosting on millimeter-structured superhydrophobic surfaces, with potential applications in anti-frost engineering.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Thiwanka Arepolage, Christophe Verdy, Thibaut Sylvestre, Aymeric Leray, Sebastien Euphrasie
Summary: This study developed two thermal concentrators, one with a 2D design of uniform thickness and another with a 3D design, using the coordinate transformation technique and metamaterials. By structuring the thermal conductor, the desired local density-heat capacity product and anisotropic thermal conductivities were achieved. The homogenized thermal conductivities were obtained from finite element simulations and cylindrical symmetry consideration. A 3D concentrator was fabricated using 3D metal printing and characterized using a thermal camera. Compared to devices that solely consider anisotropic conductivities, the time evolution characteristics of the metadevice designed with coordinate transformation were closer to those of an ideal concentrator.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)
Article
Thermodynamics
Liangyuan Cheng, Qingyang Wang, Jinliang Xu
Summary: In this study, we investigated the supercritical heat transfer of CO2 in a horizontal tube with a diameter of 10.0 mm, covering a wide range of pressures, mass fluxes, and heat fluxes. The study revealed a non-monotonic increase in wall temperatures along the flow direction and observed both positive and negative wall temperature differences between the bottom and top tube. The findings were explained by the thermal conduction in the solid wall interacting with the stratified-wavy flow in the tube.
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER
(2024)