Heat Transfer Enhancement by Perforated and Louvred Fin Heat Exchangers

Miftah Altwieb,Aliyu M Aliyu,Krzysztof J Kubiak,Rakesh Mishra

doi:10.3390/en15020400

Miftah Altwieb, Aliyu M Aliyu + Show 2 more

Open Access

https://doi.org/10.3390/en15020400

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Journal: Energies	Publication Date: Jan 6, 2022
Citations: 5	License type: CC BY 4.0

Affiliation: University of Huddersfield, University of Leeds

Abstract

Multi-tube multi-fin heat exchangers are extensively used in various industries. In the current work, detailed experimental investigations were carried out to establish the flow/heat transfer characteristics in three distinct heat exchanger geometries. A novel perforated plain fin design was developed, and its performance was evaluated against standard plain and louvred fins designs. Experimental setups were designed, and the tests were carefully carried out which enabled quantification of the heat transfer and pressure drop characteristics. In the experiments the average velocity of air was varied in the range of 0.7 m/s to 4 m/s corresponding to Reynolds numbers of 600 to 2650. The water side flow rates in the tubes were kept at 0.12, 0.18, 0.24, 0.3, and 0.36 m3/h corresponding to Reynolds numbers between 6000 and 30,000. It was found that the louvred fins produced the highest heat transfer rate due to the availability of higher surface area, but it also produced the highest pressure drops. Conversely, while the new perforated design produced a slightly higher pressure drop than the plain fin design, it gave a higher value of heat transfer rate than the plain fin especially at the lower liquid flow rates. Specifically, the louvred fin gave consistently high pressure drops, up to 3 to 4 times more than the plain and perforated models at 4 m/s air flow, however, the heat transfer enhancement was only about 11% and 13% over the perforated and plain fin models, respectively. The mean heat transfer rate and pressure drops were used to calculate the Colburn and Fanning friction factors. Two novel semiempirical relationships were derived for the heat exchanger’s Fanning and Colburn factors as functions of the non-dimensional fin surface area and the Reynolds number. It was demonstrated that the Colburn and Fanning factors were predicted by the new correlations to within ±15% of the experiments.

Highlights

IntroductionHeat exchanging devices are used to transfer thermal energy between two or more mediums, which could be fluid–fluid or fluid–gas systems
Introduction published maps and institutional affilHeat exchanging devices are used to transfer thermal energy between two or more mediums, which could be fluid–fluid or fluid–gas systems
With respect to the average air velocity corresponding to the three heat exchangers over a range of water flow rates namely 0.12, 0.18, 0.24, 0.3 and 0.36 m3/h

Summary

Introduction

Heat exchanging devices are used to transfer thermal energy between two or more mediums, which could be fluid–fluid or fluid–gas systems. The heat transfer process is carefully considered in the design of heat exchangers, which may involve various modes of heat transfer. Heat exchangers are used widely in a wide range of industries where there may be a need for controlled heating or cooling of flow streams, controlled evaporation, or controlled condensation, such as ventilation and air conditioning systems (HVAC), power generation industries, process industries, and manufacturing plants [1,2]. There are specific guidelines and procedures for designing and predicting performance of the heat exchangers. The performance of heat exchangers depends on geometric, flow, and fluid variables. Appropriate selection of these variables is very important for the optimum performance of the heat exchanger iations

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