Enhancement of heat transfer using elliptical twisted inner pipe with convergent conical ring turbulator for turbulent flow in double pipe heat exchanger

IF 4.9 2区工程技术 Q1 ENGINEERING, MECHANICAL

International Journal of Thermal Sciences Pub Date : 2024-11-20 DOI:10.1016/j.ijthermalsci.2024.109558

Rizvi Arefin Rinik, Arafat Ahmed Bhuiyan, Md. Rezwanul Karim

{"title":"Enhancement of heat transfer using elliptical twisted inner pipe with convergent conical ring turbulator for turbulent flow in double pipe heat exchanger","authors":"Rizvi Arefin Rinik, Arafat Ahmed Bhuiyan, Md. Rezwanul Karim","doi":"10.1016/j.ijthermalsci.2024.109558","DOIUrl":null,"url":null,"abstract":"<div><div>This study focuses on evaluating the impact of a fully twisted inner pipe along with conical rings turbulator by conducting a numerical analysis of the double-pipe heat exchanger (DPHE), considering both parallel and counterflow configurations for heat transfer. As modification, a straight elliptical pipe compared with two other pipes with three twists and full twists along their lengths is also investigated to compute the heat transfer rate, pressure drop, and turbulence characteristics. Modelling has been performed using ANSYS Fluent, considering the RNG k-ε turbulence model. The regime of turbulent flow is studied within the range of Reynolds numbers from 5,000 to 26,000. Validation has been conducted comparing with the experimental studies, and reasonable agreement has been observed. The full twists effect generates a swirling motion, and conical rings are inserted inside the outer pipe as a passive turbulator to guide the flow towards the inner pipe, where the hot fluid passes. Comparing the results, the inner twisted pipe with the conical ring exhibits a significant improvement in the Nusselt number (<span><math><mrow><mi>N</mi><mi>u</mi></mrow></math></span>), reaching 445 in the counterflow direction with the six rings. The evaluation of entropy generation is described as a function of frictional and thermal contributions. According to the findings, turbulators slightly increase entropy development. Analysis of total entropy generation shows that, because of the high viscosity, frictional entropy generation is dominant. Also, when the vortex flow becomes stronger, the total entropy creation rate decreases down. The Performance Evaluation Criteria (PEC) is also greater than 1 for both parallel and counterflow flow, indicating that enhancement of the rate of heat transfer, outweighs the decrease in pressure drop. Particularly in counterflow directions the PEC is 2.3 which is impressive. Overall, full twists along the pipe lengths enhance the heat exchanger's performance, and full twists with six conical rings fortify most in both flow directions.</div></div>","PeriodicalId":341,"journal":{"name":"International Journal of Thermal Sciences","volume":"210 ","pages":"Article 109558"},"PeriodicalIF":4.9000,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"International Journal of Thermal Sciences","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S129007292400680X","RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, MECHANICAL","Score":null,"Total":0}

引用次数: 0

Abstract

This study focuses on evaluating the impact of a fully twisted inner pipe along with conical rings turbulator by conducting a numerical analysis of the double-pipe heat exchanger (DPHE), considering both parallel and counterflow configurations for heat transfer. As modification, a straight elliptical pipe compared with two other pipes with three twists and full twists along their lengths is also investigated to compute the heat transfer rate, pressure drop, and turbulence characteristics. Modelling has been performed using ANSYS Fluent, considering the RNG k-ε turbulence model. The regime of turbulent flow is studied within the range of Reynolds numbers from 5,000 to 26,000. Validation has been conducted comparing with the experimental studies, and reasonable agreement has been observed. The full twists effect generates a swirling motion, and conical rings are inserted inside the outer pipe as a passive turbulator to guide the flow towards the inner pipe, where the hot fluid passes. Comparing the results, the inner twisted pipe with the conical ring exhibits a significant improvement in the Nusselt number (

N u

), reaching 445 in the counterflow direction with the six rings. The evaluation of entropy generation is described as a function of frictional and thermal contributions. According to the findings, turbulators slightly increase entropy development. Analysis of total entropy generation shows that, because of the high viscosity, frictional entropy generation is dominant. Also, when the vortex flow becomes stronger, the total entropy creation rate decreases down. The Performance Evaluation Criteria (PEC) is also greater than 1 for both parallel and counterflow flow, indicating that enhancement of the rate of heat transfer, outweighs the decrease in pressure drop. Particularly in counterflow directions the PEC is 2.3 which is impressive. Overall, full twists along the pipe lengths enhance the heat exchanger's performance, and full twists with six conical rings fortify most in both flow directions.

查看原文本刊更多论文

在双管热交换器中使用带有会聚锥形环涡轮器的椭圆扭曲内管增强湍流传热

本研究的重点是通过对双管热交换器（DPHE）进行数值分析，评估完全扭曲的内管和锥形环形湍流器的影响，同时考虑平行和逆流两种传热配置。作为修改，还研究了直椭圆管与另外两根管子的比较，这两根管子沿其长度方向分别有三次扭曲和完全扭曲，以计算传热速率、压降和湍流特性。使用 ANSYS Fluent 进行了建模，并考虑了 RNG k-ε 湍流模型。在雷诺数 5,000 到 26,000 的范围内研究了湍流机制。与实验研究进行了比较验证，结果显示两者吻合。全扭曲效应产生漩涡运动，锥形环作为被动湍流器插入外管内部，引导流体流向热流体通过的内管。比较结果发现，带有锥形环的内扭曲管道的努塞尔特数（Nu）显著提高，在逆流方向上，六个环的努塞尔特数达到 445。熵产生的评估被描述为摩擦和热贡献的函数。研究结果表明，涡轮略微增加了熵的产生。对总熵生成的分析表明，由于粘度较高，摩擦熵生成占主导地位。此外，当涡流变得更强时，总熵产生率会下降。平行流和逆流的性能评价标准（PEC）也都大于 1，这表明传热速率的提高大于压降的降低。特别是在逆流方向，PEC 值为 2.3，令人印象深刻。总体而言，沿管道长度方向的全扭转提高了热交换器的性能，而带有六个锥形环的全扭转则在两个流向上都增强了热交换器的性能。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

求助全文

约1分钟内获得全文求助全文

来源期刊

International Journal of Thermal Sciences 工程技术-工程：机械

CiteScore

8.10

自引率

11.10%

发文量

531

审稿时长

55 days

期刊介绍： The International Journal of Thermal Sciences is a journal devoted to the publication of fundamental studies on the physics of transfer processes in general, with an emphasis on thermal aspects and also applied research on various processes, energy systems and the environment. Articles are published in English and French, and are subject to peer review. The fundamental subjects considered within the scope of the journal are: * Heat and relevant mass transfer at all scales (nano, micro and macro) and in all types of material (heterogeneous, composites, biological,...) and fluid flow * Forced, natural or mixed convection in reactive or non-reactive media * Single or multi–phase fluid flow with or without phase change * Near–and far–field radiative heat transfer * Combined modes of heat transfer in complex systems (for example, plasmas, biological, geological,...) * Multiscale modelling The applied research topics include: * Heat exchangers, heat pipes, cooling processes * Transport phenomena taking place in industrial processes (chemical, food and agricultural, metallurgical, space and aeronautical, automobile industries) * Nano–and micro–technology for energy, space, biosystems and devices * Heat transport analysis in advanced systems * Impact of energy–related processes on environment, and emerging energy systems The study of thermophysical properties of materials and fluids, thermal measurement techniques, inverse methods, and the developments of experimental methods are within the scope of the International Journal of Thermal Sciences which also covers the modelling, and numerical methods applied to thermal transfer.