Numerical Analysis of Heat Transfer and Pressure Drop in Helically Micro-Finned Tubes

Muhammad Ammar Ali,Emad Uddin,Muhammad Sajid,Niaz Bahadur,Zaib Ali

doi:10.3390/pr9050754

Muhammad Ammar Ali, Emad Uddin + Show 3 more

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https://doi.org/10.3390/pr9050754

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Journal: Processes	Publication Date: Apr 24, 2021
Citations: 6	License type: CC BY 4.0

Affiliation: National University of Sciences and Technology

Abstract

In this study, the pressure drop and heat transfer characteristics of smooth tube and internal helically micro-finned tubes with two different fin-to-fin height ratios i.e., equal fin height and alternating fin height, are computationally analysed. The tube with alternating fin height is analysed for proof of concept of pressure drop reduction. A single phase steady turbulent flow model is used with a Reynolds number ranging from 12,000 to 54,000. Water is used as working fluid with inlet temperature of 55 °C and constant wall temperature of 20 °C is applied. Friction factor, heat transfer coefficient, Nusselt number, and Thermal Performance Index are evaluated and analysed. The numerical results are validated by comparison with the experimental and numerical data from literature. The results showed that the thermal performance is enhanced due to helically finned tube for a range of Reynolds numbers, but at the expense of increased pressure drop as compared to a smooth tube. The helically finned tube with alternating fin heights showed a 5% decrease in friction factor and <1% decrease in heat transfer coefficient when compared with the equal fin heights tube, making it a suitable choice for heat transfer applications.

Highlights

Heat transfer enhancement techniques for heat exchanger applications can result in size reduction, high heat transfer coefficient, and lower operating cost
Micro-finned tubes with equal fin heights are common in heat exchanger applications
Keeping in view that the temperature drop for both helically finned tubes was almost similar. Both of these results indicate that a fin-to-fin height ratio of 1:2 has relatively better performance in terms of the pumping power required to obtain the heat transfer enhancement

Summary

Introduction

Heat transfer enhancement techniques for heat exchanger applications can result in size reduction, high heat transfer coefficient, and lower operating cost. The increase in enhanced heat transfer can reach up to six times as compared to the unenhanced one [1]. A variety of heat transfer enhancement techniques are being used extensively in heat exchanger applications. There are two main types of heat transfer enhancement techniques: active and passive. Active methods require external energy input in addition to the pumping power required. Active methods are not so common in applications because of extra energy requirements. Passive methods require no additional energy and are built in to the system as its integral part. Passive methods increase the heat transfer by introducing turbulence and/or increase in surface area [2]

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