International Journal of Thermofluids最新文献

Compressibility effects in microchannel flows between two-parallel plates at low reynolds and mach numbers: Numerical analysis 低雷诺数和低马赫数下两平行板间微通道流动的可压缩性效应：数值分析

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-20 DOI: 10.1016/j.ijft.2024.100921

Mohammed E. Elgack , Khaled Al-Souqi , Mohammad O. Hamdan , Mohamed Abdelgawad

Under certain circumstances, flow in microchannels can exhibit compressibility effects even at Reynolds numbers (Re) around (below 2,300) and low Mach numbers (below 0.3). This is particularly true for gases, especially when the flow undergoes significant pressure changes or acceleration within the microchannel. This study investigates the compressibility effects encountered in two-parallel plates microchannels at these low Reynolds and Mach numbers, due to the high-pressure drop associated with the small scale of the microchannels. This uncommon flow is characterized by an exceptionally small channel diameter-to-length aspect ratio (∼10^–3), resulting in a friction coefficient that deviates from the typical value for laminar flow between parallel plates (f = 96/Re). Both steady and transient effects on the flow field are examined under low Re subsonic flow, assuming continuum behavior. The ideal gas equation is used to model gas density, while the isothermal Tait-Murnaghan equation models liquid density. For gases, compressibility effects are observed primarily when the inlet pressure ratio exceeds 0.1. The results show that these effects are less pronounced for liquids, even at elevated inlet pressure ratios. Additionally, a flow delay across the channel exhibits a first-order transient response. For liquid flow, this effect depends on the channel resistance, the total fluid volume within the channel, and the liquid's bulk properties, rather than the inlet pressure ratio.

在某些情况下，即使雷诺数（Re）在 2300 左右（低于 2300）和低马赫数（低于 0.3），微通道中的流动也会表现出可压缩性效应。对于气体来说尤其如此，特别是当微小通道内的流动经历了显著的压力变化或加速度时。本研究探讨了双平行板微通道在低雷诺数和低马赫数条件下遇到的可压缩性效应，这是由于微通道尺度较小而产生的高压降所致。这种不常见流动的特点是通道直径与长度的长宽比特别小（∼10-3），导致摩擦系数偏离平行板间层流的典型值（f = 96/Re）。在假设连续行为的情况下，研究了低 Re 亚音速流动对流场的稳定和瞬态影响。理想气体方程用于模拟气体密度，而等温 Tait-Murnaghan 方程则用于模拟液体密度。对于气体，主要在入口压力比超过 0.1 时观察到可压缩性效应。结果表明，即使在入口压力比升高的情况下，这些影响对于液体也不那么明显。此外，流经通道的流动延迟会产生一阶瞬态响应。对于液体流动，这种效应取决于通道阻力、通道内的总流体体积和液体的体积特性，而不是入口压力比。

{"title":"Compressibility effects in microchannel flows between two-parallel plates at low reynolds and mach numbers: Numerical analysis","authors":"Mohammed E. Elgack , Khaled Al-Souqi , Mohammad O. Hamdan , Mohamed Abdelgawad","doi":"10.1016/j.ijft.2024.100921","DOIUrl":"10.1016/j.ijft.2024.100921","url":null,"abstract":"<div><div>Under certain circumstances, flow in microchannels can exhibit compressibility effects even at Reynolds numbers (<em>Re</em>) around (below 2,300) and low Mach numbers (below 0.3). This is particularly true for gases, especially when the flow undergoes significant pressure changes or acceleration within the microchannel. This study investigates the compressibility effects encountered in two-parallel plates microchannels at these low Reynolds and Mach numbers, due to the high-pressure drop associated with the small scale of the microchannels. This uncommon flow is characterized by an exceptionally small channel diameter-to-length aspect ratio (∼10<sup>–3</sup>), resulting in a friction coefficient that deviates from the typical value for laminar flow between parallel plates (<em>f</em> = 96/<em>Re</em>). Both steady and transient effects on the flow field are examined under low <em>Re</em> subsonic flow, assuming continuum behavior. The ideal gas equation is used to model gas density, while the isothermal Tait-Murnaghan equation models liquid density. For gases, compressibility effects are observed primarily when the inlet pressure ratio exceeds 0.1. The results show that these effects are less pronounced for liquids, even at elevated inlet pressure ratios. Additionally, a flow delay across the channel exhibits a first-order transient response. For liquid flow, this effect depends on the channel resistance, the total fluid volume within the channel, and the liquid's bulk properties, rather than the inlet pressure ratio.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100921"},"PeriodicalIF":0.0,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Renewable energy as an auxiliary to heat pumps: Performance evaluation of hybrid solar-geothermal-systems 可再生能源作为热泵的辅助能源：太阳能-地热混合系统的性能评估

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-20 DOI: 10.1016/j.ijft.2024.100922

Rabih Murr , Jalal Faraj , Hicham El Hage , Mahmoud Khaled

The aim of this study is to combine renewable energy sources with heat pumps so that the usage of electricity needed to operate heat pumps is minimized along with associated fuel combustion. The aforementioned objective leads to reduce the energy consumption, the operational cost and the environmental impact of the heat pump. To minimize the usage of electricity, it is proposed that the heat pump (HP) system is combined by two renewable energy systems, a Solar Air Heater (SAH) and a Geothermal Well Water (G). To enrich this study, five prospective combinations of Heat Pump (HP), Solar Air Heater (SAH) placed Upstream (U) and Downstream (D) of the condenser, and Geothermal Water Well (G) were investigated. Hereafter, these five combinations are referred as HP-G, HP-S-U, HP-S-D, HP-G-S-U and HP-G-S-D. The thermal modeling of the aforementioned combinations in addition to baseline HP were developed and examined using an in-house computational code. To ensure that the input data used in the computational code are reliable, experiments were conducted to validate that the geothermal water temperature is higher than the ambient temperature in winter, in addition to confirming the analytical thermal modeling of the solar air heater. Numerical analyses and associated parametric studies revealed that the combination of Solar Air Heater (SAH) and a Geothermal Well Water (G) can efficiently increase the performance of the system by reducing the power needed to operate the compressor of HP. The gain in COP was found to be 48, 43, 81, 105 and 191 % for HP-G, HP-S-U, HP-S-D, HP-G-S-U and HP-G-S-D respectively. In addition, results revealed that the most efficient system is the (HP-G-S-D) for all simulated conditions and assumptions with a gain in COP that can reach up to 191 % in comparison to the baseline heat pump system.

这项研究的目的是将可再生能源与热泵结合起来，从而最大限度地减少热泵运行所需的电力和相关燃料的燃烧。上述目标可降低热泵的能耗、运行成本和对环境的影响。为了最大限度地减少用电量，建议将热泵（HP）系统与太阳能空气加热器（SAH）和地热井水（G）这两个可再生能源系统结合起来。为了丰富这项研究，研究了热泵（HP）、置于冷凝器上游（U）和下游（D）的太阳能空气加热器（SAH）以及地热水井（G）的五种组合。以下将这五种组合称为 HP-G、HP-S-U、HP-S-D、HP-G-S-U 和 HP-G-S-D。除基准 HP 外，上述组合的热建模均采用内部计算代码进行开发和检验。为确保计算代码中使用的输入数据可靠，除了确认太阳能空气加热器的分析热建模外，还进行了实验，以验证冬季地热水温度高于环境温度。数值分析和相关参数研究表明，太阳能空气加热器（SAH）和地热井水（G）的组合可以通过降低运行 HP 压缩机所需的功率来有效提高系统性能。研究发现，HP-G、HP-S-U、HP-S-D、HP-G-S-U 和 HP-G-S-D 的 COP 增益分别为 48%、43%、81%、105% 和 191%。此外，结果显示，在所有模拟条件和假设下，效率最高的系统是（HP-G-S-D），与基准热泵系统相比，其 COP 增益可达 191%。

{"title":"Renewable energy as an auxiliary to heat pumps: Performance evaluation of hybrid solar-geothermal-systems","authors":"Rabih Murr , Jalal Faraj , Hicham El Hage , Mahmoud Khaled","doi":"10.1016/j.ijft.2024.100922","DOIUrl":"10.1016/j.ijft.2024.100922","url":null,"abstract":"<div><div>The aim of this study is to combine renewable energy sources with heat pumps so that the usage of electricity needed to operate heat pumps is minimized along with associated fuel combustion. The aforementioned objective leads to reduce the energy consumption, the operational cost and the environmental impact of the heat pump. To minimize the usage of electricity, it is proposed that the heat pump (HP) system is combined by two renewable energy systems, a Solar Air Heater (SAH) and a Geothermal Well Water (G). To enrich this study, five prospective combinations of Heat Pump (HP), Solar Air Heater (SAH) placed Upstream (U) and Downstream (D) of the condenser, and Geothermal Water Well (G) were investigated. Hereafter, these five combinations are referred as HP-G, HP-S-U, HP-S-D, HP-G-S-U and HP-G-S-D. The thermal modeling of the aforementioned combinations in addition to baseline HP were developed and examined using an in-house computational code. To ensure that the input data used in the computational code are reliable, experiments were conducted to validate that the geothermal water temperature is higher than the ambient temperature in winter, in addition to confirming the analytical thermal modeling of the solar air heater. Numerical analyses and associated parametric studies revealed that the combination of Solar Air Heater (SAH) and a Geothermal Well Water (G) can efficiently increase the performance of the system by reducing the power needed to operate the compressor of HP. The gain in COP was found to be 48, 43, 81, 105 and 191 % for HP-G, HP-S-U, HP-S-D, HP-G-S-U and HP-G-S-D respectively. In addition, results revealed that the most efficient system is the (HP-G-S-D) for all simulated conditions and assumptions with a gain in COP that can reach up to 191 % in comparison to the baseline heat pump system.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100922"},"PeriodicalIF":0.0,"publicationDate":"2024-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537752","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of external force on the dispersion of particles and permeability of substances via carbon nanotubes in reverse electrodialysis using molecular dynamics simulation 利用分子动力学模拟反向电渗析中外力对碳纳米管颗粒分散和物质渗透性的影响

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-18 DOI: 10.1016/j.ijft.2024.100915

Dheyaa J. Jasim , Ali B.M. Ali , Abdulrahman A. Almehizia , Amer Alhaj Zen , Soheil Salahshour , Sh. Esmaeili

Background

Using novel technologies and solutions is crucial for producing clean water. There are different ways to remove dissolved salts from water.

Methods

This study aimed to analyze the effect of an external force (EF) on the morphology of channels, the dispersion of particles, and the permeability of substances via carbon nanotubes in reverse electrodialysis. It was done using a computer simulation that studied the movement of molecules. This research aimed to study the effect of EF on the dispersion of particles and permeability of substances via carbon nanotubes using a reverse electrodialysis approach. The results show that increasing the EF from 0.0001 to 0.0005 eV/Å increased the electric current and fluid flow intensity from 5.31 e/ns and 211.31 atom/ns to 5.62 e/ns and 263.01 atom/ns. Moreover, the density decreased from 4.83 to 4.66 atom/nm³. Furthermore, the number of broken hydrogen bonds increased from 116 to 166.

Significant findings

By understanding the effect of EF on particle movement and material passage through carbon nanotubes, researchers can optimize the design of reverse electrodialysis systems to enhance their performance. This can lead to more effective and cost-efficient water treatment solutions, crucial for producing clean water.

背景采用新型技术和解决方案对生产清洁水至关重要。本研究旨在分析外力（EF）对反向电渗析中碳纳米管通道形态、颗粒分散和物质渗透性的影响。这项研究是通过研究分子运动的计算机模拟完成的。这项研究旨在利用反向电渗析方法研究 EF 对颗粒分散和物质通过碳纳米管的渗透性的影响。结果表明，EF 值从 0.0001 到 0.0005 eV/Å，电流和流体流动强度从 5.31 e/ns 和 211.31 atom/ns 增加到 5.62 e/ns 和 263.01 atom/ns。此外，密度从 4.83 原子/纳米3 下降到 4.66 原子/纳米3。通过了解 EF 对颗粒运动和材料通过碳纳米管的影响，研究人员可以优化反向电渗析系统的设计，从而提高其性能。这将带来更有效、更具成本效益的水处理解决方案，对生产清洁水至关重要。

{"title":"Effect of external force on the dispersion of particles and permeability of substances via carbon nanotubes in reverse electrodialysis using molecular dynamics simulation","authors":"Dheyaa J. Jasim , Ali B.M. Ali , Abdulrahman A. Almehizia , Amer Alhaj Zen , Soheil Salahshour , Sh. Esmaeili","doi":"10.1016/j.ijft.2024.100915","DOIUrl":"10.1016/j.ijft.2024.100915","url":null,"abstract":"<div><h3>Background</h3><div>Using novel technologies and solutions is crucial for producing clean water. There are different ways to remove dissolved salts from water.</div></div><div><h3>Methods</h3><div>This study aimed to analyze the effect of an external force (EF) on the morphology of channels, the dispersion of particles, and the permeability of substances via carbon nanotubes in reverse electrodialysis. It was done using a computer simulation that studied the movement of molecules. This research aimed to study the effect of EF on the dispersion of particles and permeability of substances via carbon nanotubes using a reverse electrodialysis approach. The results show that increasing the EF from 0.0001 to 0.0005 eV/Å increased the electric current and fluid flow intensity from 5.31 e/ns and 211.31 atom/ns to 5.62 e/ns and 263.01 atom/ns. Moreover, the density decreased from 4.83 to 4.66 atom/nm<sup>3</sup>. Furthermore, the number of broken hydrogen bonds increased from 116 to 166.</div></div><div><h3>Significant findings</h3><div>By understanding the effect of EF on particle movement and material passage through carbon nanotubes, researchers can optimize the design of reverse electrodialysis systems to enhance their performance. This can lead to more effective and cost-efficient water treatment solutions, crucial for producing clean water.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100915"},"PeriodicalIF":0.0,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537751","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Effect of pin fins on heat transfer during condensation in minichannel heat exchanger 针翅片对微型通道热交换器冷凝过程中传热的影响

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-16 DOI: 10.1016/j.ijft.2024.100917

Fadi Alnaimat , Mohamed Daadoua , Bobby Mathew

In this study, condensation heat transfer of water vapor in a minichannel heat exchanger on smooth and pin fins surfaces was investigated experimentally. The experimental study was carried out to evaluate heat transfer coefficient, overall heat transfer coefficient, and Nusselt number over different ranges of vapor mass flux from 0.0064 to 0.0368 kg m⁻² s⁻¹ and cold-water flow rate range between 0.0013 kg s⁻¹ to 0.0057 kg s⁻¹. The minichannel has a rectangular shape with a hydraulic diameter of 1.3 mm. The experimental testing is carried out on aluminum surface with a channel that has a length of 270, width of 30 mm, and height of 1.3 mm. The pin fins surface is on the bottom of the condensing channel and the fins are circular and have diameter, height, and spacing of 1 mm, and are in-inline arrangement. It is found that condensation heat transfer coefficient on pin fins surface is about 15 % higher than that on smooth surface. It is found that the condensation heat transfer coefficient increases significantly with increasing the vapor mass flux. In addition, the effect of increasing the cold fluid flow rate is lower than that of the hot vapor flow rate, but it becomes more significant for higher vapor flux.

本研究通过实验研究了水蒸气在光滑翅片和针形翅片表面的微型通道热交换器中的冷凝传热。实验研究评估了水蒸气质量通量在 0.0064 至 0.0368 kg m-2 s-1 和冷水流速在 0.0013 kg s-1 至 0.0057 kg s-1 之间不同范围内的传热系数、总传热系数和努塞尔特数。微型通道为矩形，水力直径为 1.3 毫米。实验测试在铝表面进行，通道长 270、宽 30 毫米、高 1.3 毫米。针翅片表面位于冷凝通道的底部，翅片呈圆形，直径、高度和间距均为 1 毫米，采用内嵌式布置。研究发现，针翅片表面的冷凝传热系数比光滑表面高出约 15%。研究发现，冷凝传热系数随着蒸汽质量通量的增加而显著提高。此外，增加冷流体流速的影响低于增加热蒸汽流速的影响，但在蒸汽通量较高时，冷凝传热系数会变得更加显著。

{"title":"Effect of pin fins on heat transfer during condensation in minichannel heat exchanger","authors":"Fadi Alnaimat , Mohamed Daadoua , Bobby Mathew","doi":"10.1016/j.ijft.2024.100917","DOIUrl":"10.1016/j.ijft.2024.100917","url":null,"abstract":"<div><div>In this study, condensation heat transfer of water vapor in a minichannel heat exchanger on smooth and pin fins surfaces was investigated experimentally. The experimental study was carried out to evaluate heat transfer coefficient, overall heat transfer coefficient, and Nusselt number over different ranges of vapor mass flux from 0.0064 to 0.0368 kg m<sup>−2</sup> s<sup>−1</sup> and cold-water flow rate range between 0.0013 kg s<sup>−1</sup> to 0.0057 kg s<sup>−1</sup>. The minichannel has a rectangular shape with a hydraulic diameter of 1.3 mm. The experimental testing is carried out on aluminum surface with a channel that has a length of 270, width of 30 mm, and height of 1.3 mm. The pin fins surface is on the bottom of the condensing channel and the fins are circular and have diameter, height, and spacing of 1 mm, and are in-inline arrangement. It is found that condensation heat transfer coefficient on pin fins surface is about 15 % higher than that on smooth surface. It is found that the condensation heat transfer coefficient increases significantly with increasing the vapor mass flux. In addition, the effect of increasing the cold fluid flow rate is lower than that of the hot vapor flow rate, but it becomes more significant for higher vapor flux.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100917"},"PeriodicalIF":0.0,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Numerical investigation of the flow characteristics inside a supersonic vapor ejector 超音速蒸汽喷射器内部流动特性的数值研究

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-15 DOI: 10.1016/j.ijft.2024.100912

Hamza K. Mukhtar, Ahmed Fadlalla, Rania Ibrahim, Saud Ghani

Integrating a vapor ejector with an air-cooled absorption cooling system (ACS) requires understanding how the ejector responds to varying condenser conditions and how the geometrical parameters affect the system's performance. This study provides a numerical investigation of the flow characteristics inside supersonic vapor ejectors. The primary objectives were identifying the best nozzle design for ACS and explaining how the secondary flow responds to different back pressures. The developed model was validated against experimental data and a one-dimensional model. Despite exhibiting increased flow fluctuations, the convex nozzle achieved an entrainment ratio of 0.4. This value was 4.9 % and 7 % higher than the values obtained by the straight and the concave nozzles, respectively. In contrast, the concave nozzle exhibits better flow stability and pressure recovery, which are considered appealing for the air-cooled ACS. The straight nozzle emerged as a balanced alternative, offering moderate entrainment alongside favorable flow stability. Moreover, secondary flow behavior at different operating modes was elaborated. Secondary flow choked at back pressures between 60–70 kPa, indicating optimal entrainment. However, at 75–80 kPa, while the secondary flow was entrained, it failed to reach sonic speed due to high-pressure waves, resulting in the sub-critical condition. Further increases in back pressure to 85–90 kPa induced back-flow due to elevated local static pressure. Mach number profiles at the mixing tube entrance remained consistent under critical operation but deviated post-critical back pressure, reflecting altered flow characteristics downstream of the mixing tube. Such elaboration of flow dynamics within ejectors paves the way for innovative designs of vapor ejectors, potentially developing ACS.

要将蒸汽喷射器与空气冷却吸收冷却系统（ACS）集成在一起，就必须了解喷射器如何应对冷凝器的不同条件，以及几何参数如何影响系统的性能。本研究对超音速蒸汽喷射器内部的流动特性进行了数值研究。主要目标是确定 ACS 的最佳喷嘴设计，并解释二次流如何对不同的背压做出响应。所开发的模型与实验数据和一维模型进行了验证。尽管凸形喷嘴表现出更大的流量波动，但其夹带率达到了 0.4。这一数值分别比直喷嘴和凹喷嘴的数值高出 4.9% 和 7%。相比之下，凹面喷嘴具有更好的流动稳定性和压力恢复能力，这对于空气冷却式气冷式空调系统来说很有吸引力。直喷嘴作为一种平衡的替代方案，在提供适度夹带的同时，还具有良好的流动稳定性。此外，还阐述了不同运行模式下的二次流行为。二次流在背压为 60-70 kPa 时窒息，这表明夹带效果最佳。然而，在 75-80 kPa 时，虽然二次流被夹带，但由于高压波的影响，二次流无法达到声速，从而导致亚临界状态。背压进一步升高到 85-90 千帕时，由于局部静压升高而产生回流。混合管入口处的马赫数剖面在临界状态下保持一致，但在临界背压后出现偏差，反映出混合管下游的流动特性发生了改变。对喷射器内流动动力学的这种阐述为蒸汽喷射器的创新设计铺平了道路，并有可能发展出 ACS。

{"title":"Numerical investigation of the flow characteristics inside a supersonic vapor ejector","authors":"Hamza K. Mukhtar, Ahmed Fadlalla, Rania Ibrahim, Saud Ghani","doi":"10.1016/j.ijft.2024.100912","DOIUrl":"10.1016/j.ijft.2024.100912","url":null,"abstract":"<div><div>Integrating a vapor ejector with an air-cooled absorption cooling system (ACS) requires understanding how the ejector responds to varying condenser conditions and how the geometrical parameters affect the system's performance. This study provides a numerical investigation of the flow characteristics inside supersonic vapor ejectors. The primary objectives were identifying the best nozzle design for ACS and explaining how the secondary flow responds to different back pressures. The developed model was validated against experimental data and a one-dimensional model. Despite exhibiting increased flow fluctuations, the convex nozzle achieved an entrainment ratio of 0.4. This value was 4.9 % and 7 % higher than the values obtained by the straight and the concave nozzles, respectively. In contrast, the concave nozzle exhibits better flow stability and pressure recovery, which are considered appealing for the air-cooled ACS. The straight nozzle emerged as a balanced alternative, offering moderate entrainment alongside favorable flow stability. Moreover, secondary flow behavior at different operating modes was elaborated. Secondary flow choked at back pressures between 60–70 kPa, indicating optimal entrainment. However, at 75–80 kPa, while the secondary flow was entrained, it failed to reach sonic speed due to high-pressure waves, resulting in the sub-critical condition. Further increases in back pressure to 85–90 kPa induced back-flow due to elevated local static pressure. Mach number profiles at the mixing tube entrance remained consistent under critical operation but deviated post-critical back pressure, reflecting altered flow characteristics downstream of the mixing tube. Such elaboration of flow dynamics within ejectors paves the way for innovative designs of vapor ejectors, potentially developing ACS.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100912"},"PeriodicalIF":0.0,"publicationDate":"2024-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142537749","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Optimized thermal pretreatment for lignocellulosic biomass of pigeon pea stalks to augment quality and quantity of biogas production 优化豌豆秆木质纤维素生物质的热预处理，提高沼气生产的质量和数量

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-11 DOI: 10.1016/j.ijft.2024.100911

T. Sathish , K. Muthukumar , R. Saravanan , Jayant Giri

By applying heat to the feedstock during the thermal treatment of biomass for the production of biogas, the organic material's biodegradability can be greatly increased. Biogas production is a huge research area for alternate energy production technology. Increased biodegradability, improved methane yield, pathogen, and weed seed destruction, and overall process efficiency are all benefits of this type of pretreatment. It is a useful pretreatment technique for maximizing the production of biogas because it can decrease inhibitory compounds, and increase the digestibility of biomass. This work focused on increasing the efficiency of biogas production from lignocellulosic biomass of pigeon pea stalks by a novel thermal pretreatment. The pigeon pea stalk is initially imposed to physical pretreatment (PT) by an automatic hammer mill which is considered as a base for comparing performance. Thermal pretreatment was carried out for one hour, and two hours durations at different temperatures like 100 °C, 125 °C, 150 °C, 175 °C, and 200 °C. Compared to physically pretreated pigeon pea stalks, 200ᴼC thermal pretreated pigeon pea stalks for two hours have produced 88.41 % higher biogas, 16.14 % increase of cellulose, 19.9 % higher volatile solid removal, and 3.94 % lesser lignin. The enhanced chemical characteristics were ensured by analyzing the chemical composition variations through the FTIR, XRD, and SEM images. So, this is recommended for enhanced biogas production.

在对生物质进行热处理以生产沼气的过程中，通过对原料加热，可以大大提高有机材料的生物降解性。沼气生产是替代能源生产技术的一个巨大研究领域。提高生物降解性、改善甲烷产量、消灭病原体和杂草种子以及提高整体工艺效率都是这种预处理的好处。它是一种有用的预处理技术，可以减少抑制性化合物，提高生物质的消化率，从而最大限度地提高沼气产量。这项工作的重点是通过新型热预处理提高鸽子豆茎秆木质纤维素生物质的沼气生产效率。豌豆茎最初由自动锤式粉碎机进行物理预处理（PT），作为比较性能的基础。热预处理在 100 ℃、125 ℃、150 ℃、175 ℃ 和 200 ℃ 等不同温度下分别进行了一小时和两小时。与物理预处理的豌豆秆相比，200ᴼC 热预处理两小时的豌豆秆产生的沼气增加了 88.41%，纤维素增加了 16.14%，挥发性固体去除率增加了 19.9%，木质素减少了 3.94%。通过傅立叶变换红外光谱、X 射线衍射和扫描电镜图像分析化学成分的变化，确保了化学特性的增强。因此，建议采用这种方法来提高沼气产量。

{"title":"Optimized thermal pretreatment for lignocellulosic biomass of pigeon pea stalks to augment quality and quantity of biogas production","authors":"T. Sathish , K. Muthukumar , R. Saravanan , Jayant Giri","doi":"10.1016/j.ijft.2024.100911","DOIUrl":"10.1016/j.ijft.2024.100911","url":null,"abstract":"<div><div>By applying heat to the feedstock during the thermal treatment of biomass for the production of biogas, the organic material's biodegradability can be greatly increased. Biogas production is a huge research area for alternate energy production technology. Increased biodegradability, improved methane yield, pathogen, and weed seed destruction, and overall process efficiency are all benefits of this type of pretreatment. It is a useful pretreatment technique for maximizing the production of biogas because it can decrease inhibitory compounds, and increase the digestibility of biomass. This work focused on increasing the efficiency of biogas production from lignocellulosic biomass of pigeon pea stalks by a novel thermal pretreatment. The pigeon pea stalk is initially imposed to physical pretreatment (PT) by an automatic hammer mill which is considered as a base for comparing performance. Thermal pretreatment was carried out for one hour, and two hours durations at different temperatures like 100 °C, 125 °C, 150 °C, 175 °C, and 200 °C. Compared to physically pretreated pigeon pea stalks, 200ᴼC thermal pretreated pigeon pea stalks for two hours have produced 88.41 % higher biogas, 16.14 % increase of cellulose, 19.9 % higher volatile solid removal, and 3.94 % lesser lignin. The enhanced chemical characteristics were ensured by analyzing the chemical composition variations through the FTIR, XRD, and SEM images. So, this is recommended for enhanced biogas production.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100911"},"PeriodicalIF":0.0,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446428","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Comparative numerical study on the effect of fin orientation on the photovoltaic/thermal (PV/T) system performance 鳍片朝向对光伏/热（PV/T）系统性能影响的数值对比研究

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-11 DOI: 10.1016/j.ijft.2024.100909

Hussain Madhi , Sattar Aljabair , Ahmed Abdulnabi Imran

The thermal performance of a photovoltaic (PV) system is highly influenced by cooling its surface temperature. In this study, a series of cooling modules are developed, including fin turbulators within a serpentine channel placed on the rear side of a photovoltaic/thermal (PV/T) system. These modules are designed to effectively cool the PV/T system, ensuring uniform temperature distribution and enhancing the system efficiency. The study examines fins at four different angles within the serpentine channel, namely 30°, 45°, 60°, and 90° The water was employed as a cooling fluid in the study, operated under laminar flow conditions, with five Reynolds number values, ranging from 250 to 1250 with 250 increment. Every PV/T system has 108 fins with an area of 600 mm2 for each. Numerical simulations were conducted to predict the flow fields resulting from each fin configuration in the serpentine channel. The electrical and thermal efficiency of the PV/T collector was evaluated for the fin configuration with better thermal performance. Results showed that fins oriented with 30° provided the best thermal performance, while fins at 90° orientation achieved maximum heat transfer coefficient. Moreover, the electrical efficiency of the proposed PV/T system could be improved by 0.8 % to 1.5 % compared to a standard PV/T system. In addition, the PV/T system demonstrated a remarkable thermal efficiency of up to 59 % at 90° fin orientation.

光伏（PV）系统的热性能在很大程度上受到冷却其表面温度的影响。本研究开发了一系列冷却模块，包括置于光伏/热系统（PV/T）后侧蛇形通道内的鳍式涡轮。这些模块旨在有效冷却光伏/热系统，确保温度分布均匀，提高系统效率。研究采用水作为冷却流体，在层流条件下运行，有五个雷诺数值，从 250 到 1250，以 250 为增量。每个 PV/T 系统有 108 片鳍片，每片面积为 600 mm2。我们进行了数值模拟，以预测蛇形通道中每种翅片配置所产生的流场。针对热性能较好的翅片配置，对光伏/T 集热器的电气和热效率进行了评估。结果表明，取向 30° 的鳍片具有最佳的热性能，而取向 90° 的鳍片则实现了最大的传热系数。此外，与标准 PV/T 系统相比，拟议 PV/T 系统的电效率可提高 0.8 % 至 1.5 %。此外，PV/T 系统在 90° 散热片方向上的热效率高达 59%。

{"title":"Comparative numerical study on the effect of fin orientation on the photovoltaic/thermal (PV/T) system performance","authors":"Hussain Madhi , Sattar Aljabair , Ahmed Abdulnabi Imran","doi":"10.1016/j.ijft.2024.100909","DOIUrl":"10.1016/j.ijft.2024.100909","url":null,"abstract":"<div><div>The thermal performance of a photovoltaic (PV) system is highly influenced by cooling its surface temperature. In this study, a series of cooling modules are developed, including fin turbulators within a serpentine channel placed on the rear side of a photovoltaic/thermal (PV/T) system. These modules are designed to effectively cool the PV/T system, ensuring uniform temperature distribution and enhancing the system efficiency. The study examines fins at four different angles within the serpentine channel, namely 30°, 45°, 60°, and 90° The water was employed as a cooling fluid in the study, operated under laminar flow conditions, with five Reynolds number values, ranging from 250 to 1250 with 250 increment. Every PV/T system has 108 fins with an area of 600 mm2 for each. Numerical simulations were conducted to predict the flow fields resulting from each fin configuration in the serpentine channel. The electrical and thermal efficiency of the PV/T collector was evaluated for the fin configuration with better thermal performance. Results showed that fins oriented with 30° provided the best thermal performance, while fins at 90° orientation achieved maximum heat transfer coefficient. Moreover, the electrical efficiency of the proposed PV/T system could be improved by 0.8 % to 1.5 % compared to a standard PV/T system. In addition, the PV/T system demonstrated a remarkable thermal efficiency of up to 59 % at 90° fin orientation.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100909"},"PeriodicalIF":0.0,"publicationDate":"2024-10-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142446429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Simulation of flow dynamics and heat transfer behavior of nanofluid in microchannel with rough surfaces 带粗糙表面微通道中纳米流体的流动动力学和传热行为模拟

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-10 DOI: 10.1016/j.ijft.2024.100901

Ali Kashani , Rassol Hamed Rasheed , Muntadher Abed Hussein , Omid Ali Akbari , Hadeel Kareem Abdul-Redha , Gholamreza Ahmadi , Soheil Salahshour , Rozbeh Sabetvand

Microchannels containing cooling fluid are among the most widely used equipment in the cooling of microscale devices, such as heat sinks in the electronics industry. In this numerical research, the flow of water/magnesium-oxide nanofluid in a 3D rectangular microchannel is simulated and investigated. The flow field and heat transfer are analyzed for the laminar flow with Reynold number (Re)= 100, 300, 700, and 1000 and nanoparticle volume fraction (φ) =0, 0.02, and 0.04. The rough surfaces include rectangular cubic ribs arranged in three one in each row along the length with 2, 3, 4, and 5 rows. The ribbed surface is under a constant heat flux. The results include examining changes in Nusselt number (Nu), pressure drop, pumping power, friction factor, and total flow entropy generation. Moreover, the contours of the temperature, pressure, and velocity distribution fields will be discussed. The results reveal that the heat transfer and physics of flow are highly dependent on hydrodynamic behavior. Increasing the number of ribs on the hot surfaces increases the pressure drop, pumping power, and heat transfer. Increasing φ also greatly affects the heat transfer rate. In the case of using 5 ribs and with φ=0.04, in Re=1000 and 700, the microchannel has the highest average Nu, pressure drop, and pumping power.

含有冷却流体的微通道是电子工业中散热器等微型设备冷却过程中最广泛使用的设备之一。在这项数值研究中，模拟并研究了水/氧化镁纳米流体在三维矩形微通道中的流动。分析了雷诺数 (Re) = 100、300、700 和 1000 以及纳米粒子体积分数 (φ) = 0、0.02 和 0.04 时的层流流场和传热情况。粗糙表面包括矩形立方肋条，沿长度方向每行三根，分别为 2、3、4 和 5 行。肋条表面处于恒定热通量下。研究结果包括努塞尔特数（Nu）、压降、泵功率、摩擦因数和总流动熵的变化。此外，还将讨论温度、压力和速度分布场的轮廓。结果表明，热传导和流动的物理特性高度依赖于流体力学行为。增加热表面的肋片数量可增加压降、泵功率和传热。增加 φ 也会极大地影响传热率。在 Re=1000 和 700 条件下，使用 5 个肋条且 φ=0.04 的微通道具有最高的平均 Nu 值、压降和泵功率。

{"title":"Simulation of flow dynamics and heat transfer behavior of nanofluid in microchannel with rough surfaces","authors":"Ali Kashani , Rassol Hamed Rasheed , Muntadher Abed Hussein , Omid Ali Akbari , Hadeel Kareem Abdul-Redha , Gholamreza Ahmadi , Soheil Salahshour , Rozbeh Sabetvand","doi":"10.1016/j.ijft.2024.100901","DOIUrl":"10.1016/j.ijft.2024.100901","url":null,"abstract":"<div><div>Microchannels containing cooling fluid are among the most widely used equipment in the cooling of microscale devices, such as heat sinks in the electronics industry. In this numerical research, the flow of water/magnesium-oxide nanofluid in a 3D rectangular microchannel is simulated and investigated. The flow field and heat transfer are analyzed for the laminar flow with Reynold number (<em>Re</em>)= 100, 300, 700, and 1000 and nanoparticle volume fraction (<em>φ</em>) =0, 0.02, and 0.04. The rough surfaces include rectangular cubic ribs arranged in three one in each row along the length with 2, 3, 4, and 5 rows. The ribbed surface is under a constant heat flux. The results include examining changes in Nusselt number (<em>Nu)</em>, pressure drop, pumping power, friction factor, and total flow entropy generation. Moreover, the contours of the temperature, pressure, and velocity distribution fields will be discussed. The results reveal that the heat transfer and physics of flow are highly dependent on hydrodynamic behavior. Increasing the number of ribs on the hot surfaces increases the pressure drop, pumping power, and heat transfer. Increasing <em>φ</em> also greatly affects the heat transfer rate. In the case of using 5 ribs and with <em>φ</em>=0.04, in <em>Re</em>=1000 and 700, the microchannel has the highest average <em>Nu</em>, pressure drop, and pumping power.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100901"},"PeriodicalIF":0.0,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441185","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Thermodynamic and environmental comparative analysis of a dual loop ORC and Kalina as bottoming cycle of a solar Brayton sCO2 将双回路 ORC 和卡利纳作为太阳能布雷顿 sCO2 底部循环的热力学和环境比较分析

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-10 DOI: 10.1016/j.ijft.2024.100895

José Manuel Tovar , Guillermo Valencia Ochoa , Daniel Mendoza Casseres

Solar energy as a thermal source has become a viable and thermo-sustainable option to generate heat, for the energy production through power cycle configurations. In this article, the balances and application of life cycle analysis (LCA) allowed to proposed thermodynamic models in order to conduct a comparative study of the energy, exergy and environmental performance of two hybrid power generation systems using a supercritical carbon dioxide Brayton with recompression, intercooling and reheating (sCO₂) as the main cycle coupled to two waste heat recovery technologies: dual loop Rankine organic cycle (DORC) and Kalina cycle (KC). The results showed that the Brayton sCO₂/DORC configuration presented better exergetic performance using Toluene (23.98%), Cyclohexane (24.01%), and Acetone (24.06%) as working fluids concerning the Brayton sCO₂/KC configuration with a 23.82%. In addition, the solar field was the component with the highest irreversibility rate (∼61.6%) when the system operated at 100% solar energy. In terms of environmental impact, the results indicate that the concentrating solar power (CSP) tower is the device that generates the most emissions in the systems studied (∼90%). Acetone was found to be 36% more polluting than the working fluid used in the sCO₂/KC system (Ammonia). In addition, aluminum as a construction material emits 5.26 % more kg CO₂-equi than steel in both systems. Also, the construction phase is the LCA stage that has the greatest impact, representing approximately 95.4% of the total emissions, followed by the decommissioning phase (4.5%) and operation (0.05%). These results show good thermo-sustainable performances that in conjunction with thermo-economic optimizations could achieve solutions applicable to the local industrial sector.

太阳能作为一种热源，已成为通过动力循环配置进行能源生产的一种可行的、热可持续的制热选择。在这篇文章中，通过平衡和应用生命周期分析（LCA），提出了热力学模型，以便对两种混合发电系统的能量、放能和环境性能进行比较研究，这两种系统使用超临界二氧化碳布雷顿再压缩、中冷和再加热（sCO2）作为主循环，并结合两种废热回收技术：双循环朗肯有机循环（DORC）和卡利纳循环（KC）。结果表明，使用甲苯（23.98%）、环己烷（24.01%）和丙酮（24.06%）作为工作流体的布雷顿 sCO2/DORC 配置具有更好的能效表现，而布雷顿 sCO2/KC 配置的能效表现为 23.82%。此外，当系统在 100% 太阳能条件下运行时，太阳能场是不可逆率最高的组成部分（61.6%）。在环境影响方面，研究结果表明，在所研究的系统中，聚光太阳能（CSP）塔是产生最多排放物的设备（∼90%）。丙酮的污染程度比 sCO2/KC 系统使用的工作液（氨）高 36%。此外，在这两种系统中，铝作为建筑材料比钢多排放 5.26 % kg CO2-equi。此外，施工阶段是影响最大的生命周期评估阶段，约占总排放量的 95.4%，其次是退役阶段（4.5%）和运行阶段（0.05%）。这些结果表明，热可持续性表现良好，结合热经济优化，可实现适用于当地工业部门的解决方案。

{"title":"Thermodynamic and environmental comparative analysis of a dual loop ORC and Kalina as bottoming cycle of a solar Brayton sCO2","authors":"José Manuel Tovar , Guillermo Valencia Ochoa , Daniel Mendoza Casseres","doi":"10.1016/j.ijft.2024.100895","DOIUrl":"10.1016/j.ijft.2024.100895","url":null,"abstract":"<div><div>Solar energy as a thermal source has become a viable and thermo-sustainable option to generate heat, for the energy production through power cycle configurations. In this article, the balances and application of life cycle analysis (LCA) allowed to proposed thermodynamic models in order to conduct a comparative study of the energy, exergy and environmental performance of two hybrid power generation systems using a supercritical carbon dioxide Brayton with recompression, intercooling and reheating (sCO<sub>2</sub>) as the main cycle coupled to two waste heat recovery technologies: dual loop Rankine organic cycle (DORC) and Kalina cycle (KC). The results showed that the Brayton sCO<sub>2</sub>/DORC configuration presented better exergetic performance using Toluene (23.98%), Cyclohexane (24.01%), and Acetone (24.06%) as working fluids concerning the Brayton sCO<sub>2</sub>/KC configuration with a 23.82%. In addition, the solar field was the component with the highest irreversibility rate (∼61.6%) when the system operated at 100% solar energy. In terms of environmental impact, the results indicate that the concentrating solar power (CSP) tower is the device that generates the most emissions in the systems studied (∼90%). Acetone was found to be 36% more polluting than the working fluid used in the sCO<sub>2</sub>/KC system (Ammonia). In addition, aluminum as a construction material emits 5.26 % more kg CO<sub>2</sub>-equi than steel in both systems. Also, the construction phase is the LCA stage that has the greatest impact, representing approximately 95.4% of the total emissions, followed by the decommissioning phase (4.5%) and operation (0.05%). These results show good thermo-sustainable performances that in conjunction with thermo-economic optimizations could achieve solutions applicable to the local industrial sector.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100895"},"PeriodicalIF":0.0,"publicationDate":"2024-10-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142432317","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Thermo-hydraulic performance of concentric tube heat exchangers with turbulent flow: Predictive correlations and iterative methods for pumping power and heat transfer 湍流同心管热交换器的热液性能：泵功率和热传递的预测相关性和迭代法

Q1 Chemical Engineering

International Journal of Thermofluids

Pub Date : 2024-10-09 DOI: 10.1016/j.ijft.2024.100898

Samer Ali , Chadi Nohra , Jalal Faraj , Talib Dbouk , Mahmoud Khaled

This research addresses the problem of predicting the thermo-hydraulic performance of concentric tube heat exchangers (CTHE) under turbulent flow conditions, a critical aspect in energy-efficient industrial systems such as HVAC, power generation, and chemical processing. Existing studies often lack accurate predictive methods for balancing heat transfer performance with pumping power requirements. To tackle this issue, novel correlations and an iterative Newton–Raphson method were developed for predicting pumping power and heat transfer rates. Three-dimensional CFD simulations of a water-to-water counter-flow CTHE were conducted, with Reynolds numbers ranging from 4000 to 8000 for both the hot and cold fluids. The simulations employed the Reynolds-Averaged Navier–Stokes (RANS) equations with the

k - ω

SST turbulence model. The results demonstrated that increasing the Reynolds number enhances both heat transfer rates and pumping power, with the cold fluid requiring consistently higher pumping power. New correlations were developed to predict pumping power, capturing the impact of both entry and fully developed flow regions. These correlations showed an average error of less than 2.33% when compared with the CFD data. The iterative Newton–Raphson method for predicting heat transfer rates demonstrated high accuracy, with an average error of 0.66% for heat transfer rate, 0.03% for hot fluid outlet temperature, and 0.01% for cold fluid outlet temperature. Additionally, we identified optimal operating conditions for efficient cooling and heating based on the heat capacity ratio (

C_{r}

). The novelty of this work lies in the development of new, highly accurate predictive correlations and iterative methods for optimizing CTHE performance, going beyond existing literature by providing comprehensive insights into the relationship between pumping power, heat transfer efficiency, and flow conditions.

这项研究旨在解决湍流条件下同心管热交换器（CTHE）的热液压性能预测问题，这是暖通空调、发电和化学处理等高能效工业系统的一个关键方面。现有研究往往缺乏精确的预测方法，无法平衡传热性能与泵功率要求。为解决这一问题，我们开发了新的相关性和迭代牛顿-拉斐森方法，用于预测泵功率和热传递率。对水-水逆流 CTHE 进行了三维 CFD 模拟，冷热流体的雷诺数范围为 4000 到 8000。模拟采用了雷诺平均纳维-斯托克斯（RANS）方程和 k-ω SST 湍流模型。结果表明，增加雷诺数可提高传热率和泵送功率，冷流体需要的泵送功率一直较高。为预测泵送功率开发了新的相关性，以捕捉进入和充分发展流动区域的影响。与 CFD 数据相比，这些相关系数的平均误差小于 2.33%。用于预测传热率的迭代牛顿-拉斐森方法具有很高的准确性，传热率的平均误差为 0.66%，热流体出口温度的平均误差为 0.03%，冷流体出口温度的平均误差为 0.01%。此外，我们还根据热容比（Cr）确定了高效冷却和加热的最佳运行条件。这项工作的新颖之处在于开发了新的、高度精确的预测相关性和迭代方法，用于优化 CTHE 性能，超越了现有文献的范围，对泵功率、传热效率和流动条件之间的关系提供了全面的见解。

{"title":"Thermo-hydraulic performance of concentric tube heat exchangers with turbulent flow: Predictive correlations and iterative methods for pumping power and heat transfer","authors":"Samer Ali , Chadi Nohra , Jalal Faraj , Talib Dbouk , Mahmoud Khaled","doi":"10.1016/j.ijft.2024.100898","DOIUrl":"10.1016/j.ijft.2024.100898","url":null,"abstract":"<div><div>This research addresses the problem of predicting the thermo-hydraulic performance of concentric tube heat exchangers (CTHE) under turbulent flow conditions, a critical aspect in energy-efficient industrial systems such as HVAC, power generation, and chemical processing. Existing studies often lack accurate predictive methods for balancing heat transfer performance with pumping power requirements. To tackle this issue, novel correlations and an iterative Newton–Raphson method were developed for predicting pumping power and heat transfer rates. Three-dimensional CFD simulations of a water-to-water counter-flow CTHE were conducted, with Reynolds numbers ranging from 4000 to 8000 for both the hot and cold fluids. The simulations employed the Reynolds-Averaged Navier–Stokes (RANS) equations with the <span><math><mrow><mi>k</mi><mo>−</mo><mi>ω</mi></mrow></math></span> SST turbulence model. The results demonstrated that increasing the Reynolds number enhances both heat transfer rates and pumping power, with the cold fluid requiring consistently higher pumping power. New correlations were developed to predict pumping power, capturing the impact of both entry and fully developed flow regions. These correlations showed an average error of less than 2.33% when compared with the CFD data. The iterative Newton–Raphson method for predicting heat transfer rates demonstrated high accuracy, with an average error of 0.66% for heat transfer rate, 0.03% for hot fluid outlet temperature, and 0.01% for cold fluid outlet temperature. Additionally, we identified optimal operating conditions for efficient cooling and heating based on the heat capacity ratio (<span><math><msub><mrow><mi>C</mi></mrow><mrow><mi>r</mi></mrow></msub></math></span>). The novelty of this work lies in the development of new, highly accurate predictive correlations and iterative methods for optimizing CTHE performance, going beyond existing literature by providing comprehensive insights into the relationship between pumping power, heat transfer efficiency, and flow conditions.</div></div>","PeriodicalId":36341,"journal":{"name":"International Journal of Thermofluids","volume":"24 ","pages":"Article 100898"},"PeriodicalIF":0.0,"publicationDate":"2024-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142416975","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0