Abstract

Boiling heat transfer can play a vital role in the two-phase flow applications. The analysis of the boiling hat transfer enhancement is of importance in such applications and the enhancement can be mostly conducted by using various active and passive techniques. One type of passive techniques is the enhancement of heat transfer by nanofluids. This article presents an extensive review on the effect of different nanofluids on the enhancement of heat transfer coefficient (HTC) and critical heat flux (CHF) for both pool as well as flow boiling. Nanoparticles addition to a working fluid is done arbitrarily to improve the thermophysical properties which in turn improves heat transfer rate. Numerous works have been done in the studies on nanofluid boiling. Among various nanoparticles, the most frequently used nanoparticles are Al2O3 and TiO2. In the case of binary nanoparticles, the most commonly used combination is Al2O3 and TiO2. After reviewing the relevant literatures, it is found that for pool boiling, the maximum HTC is increased to 138% for TiO2 nanoparticles and the maximum CHF is increased to 274.2% for MWCNTs. Conversely, in flow boiling the maximum HTC is increased to 126% for ZnO nanoparticles and the maximum CHF increased to as 100% for GO nanoparticles. In addition, when two or more nanoparticles in succession or binary nanofluids are used the CHF in pool boiling increased up to 100% for Al2O3 and TiO2 as well as the CHF in flow boiling increased up to 100% for Al2O3, ZnO, and Diamond. Though the information of the coefficient of heat transfer and the critical heat flux varied for different nanofluids and vary from experiment to experiment for each of the nanofluids. This variation happens because the coefficient of heat transfer and the critical heat flux in boiling is dependent upon several factors.

Highlights

  • Attention will be paid to the accumulation of nanofluids to the base fluid to boost the transfer of boiling heat

  • After reviewing several articles on nanofluids boiling heat transfer, it has seen that the heat transfer coefficient and critical heat flux could be increased by using nanofluids in the boiling heat transfer

  • The authors have tried to show the progress of research on the boiling heat transfer of nanofluids

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Summary

PREPARATIONS OF NANOFLUID

The nanofluid generation to alter the rate of heat transfer of traditional fluids is the most significant step in the use of Nano phase particles. Nanofluids consist primarily of carbides, oxides, metals and carbon nanotubes which, with the addition of stabilizing agents, can be circulated into heat transfer fluids, like as hydrocarbons, water and ethylene glycol. 4.1 Single-Step Method A single-step method has been developed to decrease the synthesis of nanoparticles. Using this process, there are many ways to prepare nanofluids, including direct condensation of evaporation, condensation of chemical vapour and chemical synthesis in one step [9]. The single-step process, known as the direct evaporation condensation method, consists of following main stages. Several advanced nanofluid production technologies (including the one-step process) have been developed due to the complexity of preparing stable nanofluids using the two-step method [8]

NANOFLUIDS ENHANCEMENT ON BOILING
RECOMMENDATION AND FUTURE DIRECTION
Findings
CONCLUSIONS
Full Text
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