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Journal of Enhanced Heat Transfer
IF: 1.406 5-Year IF: 1.075 SJR: 0.287 SNIP: 0.653 CiteScore™: 1.2

ISSN Print: 1065-5131
ISSN Online: 1563-5074

Journal of Enhanced Heat Transfer

DOI: 10.1615/JEnhHeatTransf.2018024886
pages 239-282

A REVIEW OF THE ROLE OF PASSIVE TECHNIQUES ON HEAT TRANSFER ENHANCEMENT OF HORIZONTAL TUBE FALLING FILM AND FLOODED EVAPORATORS

Dilli Balaji
Department of Ocean Structures, National Institute of Ocean Technology, Chennai 600100, Tamil Nadu, India
Ramalingam Velraj
Institute of Energy Studies, Anna University, Chennai 600024, Tamil Nadu, India
Published more than 100 papers and having a h�index of 19 . more than 20 Ph.D. research scholars completed under my supervision. In addtion served as Director, Institute for CAD/CAM etc.
M. V. Ramana Murthy
Department of Ocean Structures, National Institute of Ocean Technology, Chennai 600100, Tamil Nadu, India

ABSTRACT

In recent years, passive techniques have played a major role in the enhancement of heat transfer in engineering equipment such as air conditioners, refrigeration systems, evaporators, etc. The primary objective of the present work is to highlight the significant impact of these techniques on the heat transfer enhancement of the evaporators with enhancement factors. Passive techniques such as porous coating, reentrant cavities, microchannels, grooved surfaces, and integral fins were reviewed and the mechanism responsible for augmentation of heat transfer in each technique was presented. Different research works have been reviewed in this paper and it has been found that porous coating offers the highest heat transfer enhancement, up to 21 times the value of a plain surface, followed by reentrant cavities with 20 times and a grooved surface with 6 times in flooded evaporators. Improvement in enhancement of up to 12 times was observed in a few works where combined passive techniques were employed in falling film evaporators. This paper also discusses the effect of nanofluids on heat transfer augmentation but found only limited information from the literature, especially with respect to mechanisms that trigger augmentation in convective heat transfer. This emphasizes the need for more focus on research in this area. From review it was observed that nanofluids were capable of enhancing heat transfer up to 3.5 times, which requires further investigation, and some of these are discussed in this paper. Moreover, the influence of a liquid feeder nozzle arrangement and tube bundle layout on the augmentation of heat transfer in a falling film evaporator was also analyzed, and it was observed that the clearance available for free falling of liquid between adjacent tubes influenced the heat transfer enhancement.


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