Pub Date : 2024-01-01DOI: 10.1615/heattransres.2024051529
Xuancong Zhang, Jinwang Li, Qi Chen
Ultra-thin flat plate heat pipes must provide a degree of flexibility to meet foldable electronics heat dissipation requirements. In this paper, a new flexible ultra-thin flat plate heat pipe with a thickness of 0.75 mm has been designed and fabricated. Compared with the traditional flexible ultra-thin flat heat pipe, the innovation lies in the flexible insulation section formed by epoxy resin pouring of the shell. The design of the shell ensures that the flexible ultra-thin plate heat pipe can respond quickly to the external temperature change, and also has good flexibility, which provides a new choice for the material and structure design of the flexible ultra-thin plate heat pipe shell. The gas-liquid coplanar type mesh is used as the capillary wick to reduce the flow resistance of steam inside the heat pipe, and the wick is hydrophilically modified to improve its capillary pumping performance; a sandwich support structure is used to prevent the steam chamber from collapsing. The thermal performance of the three liquid filling ratios of 0.3, 0.4 and 0.5 was tested at different tilt angles and bending angles. The results show that: in the cases of filling ratios of 0.3, 0.4 and 0.5, the ultra-thin flexible flat plate heat pipe with the liquid filling ratio of 0.3 has the best heat transfer performance under different working conditions; the tilt angle has different effects on the heat transfer performance and starting speed of the ultra-thin flexible flat plate heat pipe with different filling ratios, and the bending angle changes the steam condensation position inside the ultra-thin flexible flat plate heat pipe and increases the thermal resistance.
{"title":"Preparation method and thermal performance of a new ultra-thin flexible flat plate heat pipe","authors":"Xuancong Zhang, Jinwang Li, Qi Chen","doi":"10.1615/heattransres.2024051529","DOIUrl":"https://doi.org/10.1615/heattransres.2024051529","url":null,"abstract":"Ultra-thin flat plate heat pipes must provide a degree of flexibility to meet foldable electronics heat dissipation requirements. In this paper, a new flexible ultra-thin flat plate heat pipe with a thickness of 0.75 mm has been designed and fabricated. Compared with the traditional flexible ultra-thin flat heat pipe, the innovation lies in the flexible insulation section formed by epoxy resin pouring of the shell. The design of the shell ensures that the flexible ultra-thin plate heat pipe can respond quickly to the external temperature change, and also has good flexibility, which provides a new choice for the material and structure design of the flexible ultra-thin plate heat pipe shell. The gas-liquid coplanar type mesh is used as the capillary wick to reduce the flow resistance of steam inside the heat pipe, and the wick is hydrophilically modified to improve its capillary pumping performance; a sandwich support structure is used to prevent the steam chamber from collapsing. The thermal performance of the three liquid filling ratios of 0.3, 0.4 and 0.5 was tested at different tilt angles and bending angles. The results show that: in the cases of filling ratios of 0.3, 0.4 and 0.5, the ultra-thin flexible flat plate heat pipe with the liquid filling ratio of 0.3 has the best heat transfer performance under different working conditions; the tilt angle has different effects on the heat transfer performance and starting speed of the ultra-thin flexible flat plate heat pipe with different filling ratios, and the bending angle changes the steam condensation position inside the ultra-thin flexible flat plate heat pipe and increases the thermal resistance.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"132 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2024-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139551694","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1615/heattransres.2023051462
Emine Yağız Gürbüz, Haytem Moussaoui, Barış Kusun, Azim Dogus Tuncer
Passive thermal management of photovoltaic (PV) panels is an effective and low-cost method for reducing the surface temperature and improving the power output of these systems. In the current study, it is aimed to upgrade the efficiency of a PV system using a latent heat storage system with metallic mesh layers and multi-metal spinel oxide nanoparticles. The experimental part of this work contains two stages. In the first stage, three PV systems including an unmodified PV, LHSS (only paraffin)-integrated PV system and a LHSS-integrated PV system that modified with metallic mesh layers. As a result of the initial test, the PV system with mesh layers added LHSS gave the best performance results. In the second experiment, the mesh integrated LHSS of the PV system has been modified with MgOAl2O3 nanoparticles for enhanced thermal conductivity and compared with the PV system with mesh layer integrated LHSS containing only paraffin. According to the experimental results of this work, applying different types of LHSS configurations significantly reduced the surface temperature of the PV panel. The overall outcomes of the present work showed that using a LHSS with MgOAl2O3 nanoparticles-doped paraffin and metallic mesh layers upgraded the normalized power output efficiency and performance ratio of the unmodified system as 17.43% and 15.72%, respectively.
{"title":"Passive thermal management of photovoltaic modules using latent heat storage system with metallic mesh layers and multi-metal spinel oxide nanoparticles","authors":"Emine Yağız Gürbüz, Haytem Moussaoui, Barış Kusun, Azim Dogus Tuncer","doi":"10.1615/heattransres.2023051462","DOIUrl":"https://doi.org/10.1615/heattransres.2023051462","url":null,"abstract":"Passive thermal management of photovoltaic (PV) panels is an effective and low-cost method for reducing the surface temperature and improving the power output of these systems. In the current study, it is aimed to upgrade the efficiency of a PV system using a latent heat storage system with metallic mesh layers and multi-metal spinel oxide nanoparticles. The experimental part of this work contains two stages. In the first stage, three PV systems including an unmodified PV, LHSS (only paraffin)-integrated PV system and a LHSS-integrated PV system that modified with metallic mesh layers. As a result of the initial test, the PV system with mesh layers added LHSS gave the best performance results. In the second experiment, the mesh integrated LHSS of the PV system has been modified with MgOAl2O3 nanoparticles for enhanced thermal conductivity and compared with the PV system with mesh layer integrated LHSS containing only paraffin. According to the experimental results of this work, applying different types of LHSS configurations significantly reduced the surface temperature of the PV panel. The overall outcomes of the present work showed that using a LHSS with MgOAl2O3 nanoparticles-doped paraffin and metallic mesh layers upgraded the normalized power output efficiency and performance ratio of the unmodified system as 17.43% and 15.72%, respectively.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"37 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138744817","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1615/heattransres.2023051028
Xin Gu, Yiwen Zhu, Xin Liu, Hao Sun, yongqing wang
As a novel variation of shell-and-tube heat exchanger, torsional flow heat exchanger has a promising application prospect, while drop-shaped tube can enhance fluid flow velocity, distribution, and overall heat transfer performance. A torsional flow heat exchanger with orthogonal drop-shaped tubes in the shell side is presented to obtain the benefits of both designs. Three numerical models about torsional flow heat exchangers are established, having the same structure but different in the axial ratio of the heat transfer tubes. The characteristics of fluid flow and heat transfer in the shell side of heat exchangers are analyzed numerically. Response surface method is utilized to optimize the shell-side structure. The results show that compared with the torsional flow heat exchanger with common round tubes, torsional flow heat exchangers with orthogonal drop-shaped tubes of three axial ratios at the Reynolds number range from 5000 to 13000, pressure drop reduces by 9.26%-14.49%, heat transfer coefficient increases by 0.65%-11.57%, and comprehensive performance improves by 14.18%-27.23%. The optimum structure of the torsional flow heat exchanger with orthogonal drop-shaped tubes is predicted by using Minitab and compared to the initial structure, resulting in 17.19% improvement in heat transfer coefficient and 18.63% improvement in comprehensive performance. The study provides a reference for the structural exploration and improvement of torsional flow heat exchangers with enhanced tubes.
{"title":"Performance and structure optimization of torsional flow heat exchanger with orthogonal drop-shaped tube","authors":"Xin Gu, Yiwen Zhu, Xin Liu, Hao Sun, yongqing wang","doi":"10.1615/heattransres.2023051028","DOIUrl":"https://doi.org/10.1615/heattransres.2023051028","url":null,"abstract":"As a novel variation of shell-and-tube heat exchanger, torsional flow heat exchanger has a promising application prospect, while drop-shaped tube can enhance fluid flow velocity, distribution, and overall heat transfer performance. A torsional flow heat exchanger with orthogonal drop-shaped tubes in the shell side is presented to obtain the benefits of both designs. Three numerical models about torsional flow heat exchangers are established, having the same structure but different in the axial ratio of the heat transfer tubes. The characteristics of fluid flow and heat transfer in the shell side of heat exchangers are analyzed numerically. Response surface method is utilized to optimize the shell-side structure. The results show that compared with the torsional flow heat exchanger with common round tubes, torsional flow heat exchangers with orthogonal drop-shaped tubes of three axial ratios at the Reynolds number range from 5000 to 13000, pressure drop reduces by 9.26%-14.49%, heat transfer coefficient increases by 0.65%-11.57%, and comprehensive performance improves by 14.18%-27.23%. The optimum structure of the torsional flow heat exchanger with orthogonal drop-shaped tubes is predicted by using Minitab and compared to the initial structure, resulting in 17.19% improvement in heat transfer coefficient and 18.63% improvement in comprehensive performance. The study provides a reference for the structural exploration and improvement of torsional flow heat exchangers with enhanced tubes.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"18 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138536156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1615/heattransres.2023050322
Oussama Benhizia, Mohamed Bouzit
This paper reports a numerical study of the laminar free convection of dilatant fluid between two concentric cylinders. The simulations have been performed for the two dimensional steady state and the ANSYS CFX 16.2 was used for that objective. The governing problem parameters are taken as 1≤n≤1.6, 10≤Pr≤103, 103≤Ra≤105 and different number of grooves added to the inner cylinder (4, 8, 12, 16). We give detailed explanations on the effects of the precedent coefficients on the streamlines, isotherms, velocity and dimensionless temperature. The Rayleigh number strengthens the convective flow which refers by increasing in the Nusselt number at the same set of the other parameters; Also, the important phenomenon here (effects of the grooves) will have a large part from the discussion section. When the grooves accomplished a given number and n is high, the fluid is stiff and the heat transfer mode is purely by conduction.
本文报告了对两个同心圆柱体之间稀释流体层流自由对流的数值研究。模拟是针对二维稳态进行的，为此使用了 ANSYS CFX 16.2。支配问题的参数取为 1≤n≤1.6、10≤Pr≤103、103≤Ra≤105，内圆柱体上添加了不同数量的凹槽（4、8、12、16）。我们详细解释了先例系数对流线、等温线、速度和无量纲温度的影响。雷利数增强了对流，在其他参数设置不变的情况下，对流的对流通过增加努塞尔特数来实现；此外，这里的重要现象（凹槽的影响）将在讨论部分占很大比重。当凹槽达到一定数量且 n 较高时，流体会变得僵硬，热量传递模式将纯粹依靠传导。
{"title":"NATURAL CONVECTION OF NON NEWTONIAN DILATANT FLUID IN THE GAP BETWEEN AN OUTER CYLINDER AND INNER CYLINDER WITH GROOVES","authors":"Oussama Benhizia, Mohamed Bouzit","doi":"10.1615/heattransres.2023050322","DOIUrl":"https://doi.org/10.1615/heattransres.2023050322","url":null,"abstract":"This paper reports a numerical study of the laminar free convection of dilatant fluid between two concentric cylinders. The simulations have been performed for the two dimensional steady state and the ANSYS CFX 16.2 was used for that objective. The governing problem parameters are taken as 1≤n≤1.6, 10≤Pr≤103, 103≤Ra≤105 and different number of grooves added to the inner cylinder (4, 8, 12, 16). We give detailed explanations on the effects of the precedent coefficients on the streamlines, isotherms, velocity and dimensionless temperature. The Rayleigh number strengthens the convective flow which refers by increasing in the Nusselt number at the same set of the other parameters; Also, the important phenomenon here (effects of the grooves) will have a large part from the discussion section. When the grooves accomplished a given number and n is high, the fluid is stiff and the heat transfer mode is purely by conduction.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"20 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138552651","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The article presents the results of a computational and experimental study of the acoustic intensification of methane oxidation processes in high-enthalpy oxygen-containing flow of hydrogen combustion products. The studies were conducted by using tube with constant cross-section and finite length. Initial specific enthalpy of the oxygen-containing flow is varied from 1600 kJ/kg to 2400 kJ/kg. The patterns of total enthalpy influence of the oxygen-containing flow of hydrogen combustion products and acoustic effect on the efficiency (completeness of chemical reactions) of methane oxidation were obtained. The dependence of acoustic frequency influence on completeness coefficient of physics-chemical processes has been found. The values of fuel equivalence ratio were determined for various total enthalpies of the oxygen-containing flow, corresponding to diffusion and kinetic regimes of methane oxidation. Stability of methane oxidation process and influence of forced acoustic oscillations on the spectral characteristics of static pressure pulsations in the flow were analyzed.
{"title":"STUDY OF FORCED ACOUSTIC OSCILLATIONS INFLUENCE ON METHANE OXIDATION PROCESS IN OXYGEN-CONTAINING FLOW OF HYDROGEN COMBUSTION PRODUCTS","authors":"Anastasiya Krikunova, Konstantin Arefyev, Ilya Grishin, Maxim Abramov, Vladislav Ligostaev, Evgeniy Slivinskii, Vitaliy Krivets","doi":"10.1615/heattransres.2023051433","DOIUrl":"https://doi.org/10.1615/heattransres.2023051433","url":null,"abstract":"The article presents the results of a computational and experimental study of the acoustic intensification of methane oxidation processes in high-enthalpy oxygen-containing flow of hydrogen combustion products. The studies were conducted by using tube with constant cross-section and finite length. Initial specific enthalpy of the oxygen-containing flow is varied from 1600 kJ/kg to 2400 kJ/kg. The patterns of total enthalpy influence of the oxygen-containing flow of hydrogen combustion products and acoustic effect on the efficiency (completeness of chemical reactions) of methane oxidation were obtained. The dependence of acoustic frequency influence on completeness coefficient of physics-chemical processes has been found. The values of fuel equivalence ratio were determined for various total enthalpies of the oxygen-containing flow, corresponding to diffusion and kinetic regimes of methane oxidation. Stability of methane oxidation process and influence of forced acoustic oscillations on the spectral characteristics of static pressure pulsations in the flow were analyzed.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"45 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138580809","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-12-01DOI: 10.1615/heattransres.2023051581
Tengqing Liu, Xuehao He, Yaokang Zhang, Shuangfeng Wang
For cooling the electronics in limited space, this study proposes UTFHP with two working modes, i.e., short UTFHP with single-end heating and single-end cooling (SHSC) and long UTFHP with middle heating and dual-end cooling (MHDC). The effects of input head load and cooling temperature on the thermal performance of the short UTFHP with SHSC and long UTFHP with MHDC have been studied for the performance comparison. The input head load ranges from 0-38 W and the cooling temperature ranges from 15 ℃ to 65 ℃. The results show that the two layers wrapped 200 in-1 screen mesh can provide adequate capillary pressure, hence, both of the two UTFHP working modes show good temperature uniformity. The short UTFHP with SHSC shows better thermal performance compared to the performance of long UTFHP with MHDC. In addition, the thermal resistances of both UTFHPs decrease with the increase of the input heat load and the decrease of the cooling temperature under the ranges of operating conditions.
{"title":"Experimental investigation on thermal performance of ultra-thin flattened heat pipe with middle heating for electronics cooling","authors":"Tengqing Liu, Xuehao He, Yaokang Zhang, Shuangfeng Wang","doi":"10.1615/heattransres.2023051581","DOIUrl":"https://doi.org/10.1615/heattransres.2023051581","url":null,"abstract":"For cooling the electronics in limited space, this study proposes UTFHP with two working modes, i.e., short UTFHP with single-end heating and single-end cooling (SHSC) and long UTFHP with middle heating and dual-end cooling (MHDC). The effects of input head load and cooling temperature on the thermal performance of the short UTFHP with SHSC and long UTFHP with MHDC have been studied for the performance comparison. The input head load ranges from 0-38 W and the cooling temperature ranges from 15 ℃ to 65 ℃. The results show that the two layers wrapped 200 in-1 screen mesh can provide adequate capillary pressure, hence, both of the two UTFHP working modes show good temperature uniformity. The short UTFHP with SHSC shows better thermal performance compared to the performance of long UTFHP with MHDC. In addition, the thermal resistances of both UTFHPs decrease with the increase of the input heat load and the decrease of the cooling temperature under the ranges of operating conditions.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"18 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139055970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This work presents a CFD investigation of a Solar Air Heater that features alternating upper and bottom absorber plates to evaluate its thermal behavior and turbulent flow characteristics. Generally, the SAH exhibits low heat transfer characteristics and poor thermal efficiency in turbulent flow. The use of alternating upper and bottom absorber plates facing the turbulent flow would improve heat transfer by producing recirculation zones mainly over these heated plates. The Computational Fluid Dynamics software program, Ansys Fluent 15.0, along with the RNG k-ε turbulence model, was utilized in this analysis to solve the transport equations for turbulent kinetic energy and dissipation rate. The analysis encompassed several geometric and operating parameters, including the range of relative absorber plate length (lp/h) from 4.375 to 140, relative absorber plate height (h/H) ranging from 0.03 to 0.12, and Reynolds numbers varying between 3800 and 18000. The impact of these parameters on heat transfer improvement factors, including the Heat Transfer Amelioration Factor (HTAR), Friction Loss Amelioration Factor (FLAR), and Thermo-Hydraulic Efficiency Factor (THEF), was studied. The optimum computed THEF value was found to be 2.18 for (Lp/h) = 4.375, (h/H) = 0.12, and Re = 3,800
{"title":"Parametric CFD study of Solar Air Heater having alternated upper and bottom absorber plates in turbulent flow","authors":"Djemel Hassene, Benmabrouk Amine, Hammami Moez, Baccar Mounir","doi":"10.1615/heattransres.2023049434","DOIUrl":"https://doi.org/10.1615/heattransres.2023049434","url":null,"abstract":"This work presents a CFD investigation of a Solar Air Heater that features alternating upper and bottom absorber plates to evaluate its thermal behavior and turbulent flow characteristics. Generally, the SAH exhibits low heat transfer characteristics and poor thermal efficiency in turbulent flow. The use of alternating upper and bottom absorber plates facing the turbulent flow would improve heat transfer by producing recirculation zones mainly over these heated plates. The Computational Fluid Dynamics software program, Ansys Fluent 15.0, along with the RNG k-ε turbulence model, was utilized in this analysis to solve the transport equations for turbulent kinetic energy and dissipation rate. The analysis encompassed several geometric and operating parameters, including the range of relative absorber plate length (lp/h) from 4.375 to 140, relative absorber plate height (h/H) ranging from 0.03 to 0.12, and Reynolds numbers varying between 3800 and 18000. The impact of these parameters on heat transfer improvement factors, including the Heat Transfer Amelioration Factor (HTAR), Friction Loss Amelioration Factor (FLAR), and Thermo-Hydraulic Efficiency Factor (THEF), was studied. The optimum computed THEF value was found to be 2.18 for (Lp/h) = 4.375, (h/H) = 0.12, and Re = 3,800","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"5 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138543356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2023-11-01DOI: 10.1615/heattransres.2023051072
Vladimir Ryndin, Amangeldy Karmanov, Akmaral Kinzhibekova, Rizagul Dyussova, Gulnara Abdullina
Classical thermodynamics traditionally overlooks the role of quantities dependent on spatial coordinates and time, especially in the context of unsteady flows. This research introduces the first law of thermodynamics (FLT) tailored for non-stationary flow, distinguishing itself with the inclusion of terms bearing partial derivatives of pressure, p(x, t), concerning coordinates and time (–υ(∂р/∂х)dx; –υ(∂р/∂t)dt). By employing this novel approach, the derived equations are validated using a centred compression wave as a representative non-stationary flow case study. A methodology is also presented for experimentally quantifying hydrodynamic energy losses in the intake and exhaust systems of internal combustion engines. Central to the exploration is the calculation of pressure forces' work –υ(∂р/∂х)dx and –υ(∂р/∂t)dt) in the FLT equation for non-stationary flows, particularly their applicability to a centred compression wave. Moreover, a distinct procedure for discerning friction work in non-stationary flow is delineated. The research methods encompass both analytical derivation and numerical simulations leveraging Mathcad software. The bespoke Mathcad program crafted for this study can graphically represent multiple flow parameters as functions of time, proving invaluable for comprehending compression wave dynamics and evaluating friction work in diverse non-steady flows. Ultimately, the incorporation of energy equations tailored for non-stationary flows into classical thermodynamics paves the way for a more comprehensive understanding and application of thermodynamics to intricate flow scenarios.
{"title":"Validating the First Law of Thermodynamics for Unsteady Flow in a Compression Wave Using Mathcad","authors":"Vladimir Ryndin, Amangeldy Karmanov, Akmaral Kinzhibekova, Rizagul Dyussova, Gulnara Abdullina","doi":"10.1615/heattransres.2023051072","DOIUrl":"https://doi.org/10.1615/heattransres.2023051072","url":null,"abstract":"Classical thermodynamics traditionally overlooks the role of quantities dependent on spatial coordinates and time, especially in the context of unsteady flows. This research introduces the first law of thermodynamics (FLT) tailored for non-stationary flow, distinguishing itself with the inclusion of terms bearing partial derivatives of pressure, p(x, t), concerning coordinates and time (–υ(∂р/∂х)dx; –υ(∂р/∂t)dt). By employing this novel approach, the derived equations are validated using a centred compression wave as a representative non-stationary flow case study. A methodology is also presented for experimentally quantifying hydrodynamic energy losses in the intake and exhaust systems of internal combustion engines. Central to the exploration is the calculation of pressure forces' work –υ(∂р/∂х)dx and –υ(∂р/∂t)dt) in the FLT equation for non-stationary flows, particularly their applicability to a centred compression wave. Moreover, a distinct procedure for discerning friction work in non-stationary flow is delineated. The research methods encompass both analytical derivation and numerical simulations leveraging Mathcad software. The bespoke Mathcad program crafted for this study can graphically represent multiple flow parameters as functions of time, proving invaluable for comprehending compression wave dynamics and evaluating friction work in diverse non-steady flows. Ultimately, the incorporation of energy equations tailored for non-stationary flows into classical thermodynamics paves the way for a more comprehensive understanding and application of thermodynamics to intricate flow scenarios.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"7 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138536144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An incompressible, electrically conducting, and viscous fluid flowing steadily and freely across a uniformly porous media that is partially constrained by an infinitely long vertical porous plate is studied in the present article. Additionally, chemical reaction and radiation absorption effects are seen. Here, a magnetic field of uniform strength is applied transversely to the plate, a normal suction velocity is imposed on the fluid, and the heat flux is considered to be constant. The non‐dimensional momentum and energy equations are solved using the method of perturbation. The problem has been analytically resolved, and several parameters, including the Hartmann number, porosity parameter, thermal Grashof number, mass Grashof number, and transport properties like the Sherwood number, skin friction, and plate temperature, are graphically represented. The current study reveals a spike in the radiation absorption effect causes skin friction to drop, but on the other hand, a contrary effect is observed for plate temperature. One of the notable findings of this investigation is that the Sherwood number increases as chemical reaction parameter influence increases.
{"title":"Effect of radiation absorption and chemical reaction on MHD‐free convective flow through a porous medium past an infinite vertical porous plate in the presence of constant heat flux","authors":"N. Ahmed, Richa Deb Dowerah","doi":"10.1002/htj.22936","DOIUrl":"https://doi.org/10.1002/htj.22936","url":null,"abstract":"An incompressible, electrically conducting, and viscous fluid flowing steadily and freely across a uniformly porous media that is partially constrained by an infinitely long vertical porous plate is studied in the present article. Additionally, chemical reaction and radiation absorption effects are seen. Here, a magnetic field of uniform strength is applied transversely to the plate, a normal suction velocity is imposed on the fluid, and the heat flux is considered to be constant. The non‐dimensional momentum and energy equations are solved using the method of perturbation. The problem has been analytically resolved, and several parameters, including the Hartmann number, porosity parameter, thermal Grashof number, mass Grashof number, and transport properties like the Sherwood number, skin friction, and plate temperature, are graphically represented. The current study reveals a spike in the radiation absorption effect causes skin friction to drop, but on the other hand, a contrary effect is observed for plate temperature. One of the notable findings of this investigation is that the Sherwood number increases as chemical reaction parameter influence increases.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"160 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74154423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This article explains the heat and mass transfer of electrically conducting Newtonian fluid in double‐diffusive magnetoconvective flow. We have considered two infinite horizontal plates at a constant distance apart under the concentration‐modulated boundary condition. A constant magnetic field is considered in vertically upward directions, which generates an induced magnetic field. We have used the weakly nonlinear analysis to obtain the heat and mass transfer rate using the Ginzburg–Landau equation. The software MATHEMATICA is used to determine the solution of the Ginzburg–Landau equation by inbuilt function. The effects of physical parameters that occurred in the study on the Nusselt number and Sherwood number have been examined graphically. Modulation has a negligible effect on the threshold value of the thermal Rayleigh number, that is, on stationary convection. Moreover, it was found that the Chandrasekhar number, magnetic‐Prandtl number, amplitude of modulation, and frequency of modulation are proportional to the heat and mass transports.
{"title":"Study of weakly nonlinear double‐diffusive magnetoconvection under concentration modulation","authors":"Atul Jakhar, Anand Kumar, Vinod K. Gupta","doi":"10.1002/htj.22939","DOIUrl":"https://doi.org/10.1002/htj.22939","url":null,"abstract":"This article explains the heat and mass transfer of electrically conducting Newtonian fluid in double‐diffusive magnetoconvective flow. We have considered two infinite horizontal plates at a constant distance apart under the concentration‐modulated boundary condition. A constant magnetic field is considered in vertically upward directions, which generates an induced magnetic field. We have used the weakly nonlinear analysis to obtain the heat and mass transfer rate using the Ginzburg–Landau equation. The software MATHEMATICA is used to determine the solution of the Ginzburg–Landau equation by inbuilt function. The effects of physical parameters that occurred in the study on the Nusselt number and Sherwood number have been examined graphically. Modulation has a negligible effect on the threshold value of the thermal Rayleigh number, that is, on stationary convection. Moreover, it was found that the Chandrasekhar number, magnetic‐Prandtl number, amplitude of modulation, and frequency of modulation are proportional to the heat and mass transports.","PeriodicalId":50408,"journal":{"name":"Heat Transfer Research","volume":"36 1","pages":""},"PeriodicalIF":1.7,"publicationDate":"2023-08-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82028310","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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