Boiling Heat Transfer and Critical Heat Flux Enhancement Using Electrophoretic Deposition of SiO2 Nanofluid

Aref Rahimian,Azam Akhavan,Hosein Kazeminejad,Seyed Mohammad Mirvakili,Hosein Khalafi

doi:10.1155/2019/1272156

Abstract

The electrophoretic deposition (EPD) technique was used to create a uniform SiO2 thin film coating on boiling plates, 4 mm in width and 9 mm in length. Significant enhancement in critical heat flux (CHF), for the hydrophilic surfaces generated by this anodic EPD method, has been observed. In order to increase the coating strength, the plates were sintered at various temperatures. To find the thickness and uniformity of the coatings, the SEM images were captured. The captured images showed that the coating thickness uniformly increased up to 90 nm for 0.5% nanofluid percentage by the EPD method. The results show that the hydrophilic and super-hydrophilic surfaces have different boiling heat transfer (BHT) coefficients and CHF behaviors. Also, the results showed an increase of 160% in the CHF value by sintering compared to a bare surface. However, because of the setup simplicity, the shape independency, the particle-coating uniformity, and thickness controllability, the EPD technique can be an appropriate option for modification of the surface and coating on the nuclear fuel cladding.

Highlights

One of the efficient heat transfer mood in the nuclear power plants is the nucleate boiling. In this heat transfer regime, the high heat flux can be transferred with smaller wall superheat than other heat transfer regimes. e nucleate boiling regime in the heat transfer systems is limited by the onset of nucleate boiling (ONB) and critical heat flux (CHF). e CHF phenomenon is a transition from the nucleate boiling with a high heat transfer to the film boiling by which heat is removed from the surface by vapor, whereby the heat transfer coefficient is rapidly decreased and the surface temperature is sharply increased with system failure. erefore, the physical phenomenon of the CHF and its enhancement is an important part in the development of the nuclear thermal hydraulics
CHF and boiling heat transfer coefficient have been investigated in the nanofluids boiling heat transfer studies [2,3,4], whereby these phenomena have changed with the dilute nanofluids
Contact Angle Measurements. e contact angle is usually measured, where a solid surface contacts with a liquid droplet, to determine the wettability of that surface. e relative molecular interaction strength between vapor, liquid, and solid is reflected by the equilibrium contact angle. e Young [15] equation determines the contact angle for the perfectly flat surface: cSG − cSL − cLG cos θC 0

Summary

Introduction

One of the efficient heat transfer mood in the nuclear power plants is the nucleate boiling. In this heat transfer regime, the high heat flux can be transferred with smaller wall superheat than other heat transfer regimes. Further studies have shown that these changes in the nanofluid boiling phenomenon and CHF are not due to the intrinsic nature of the nanofluids but are due to the deposition of the nanoparticles on the heating surfaces and change of surface texture and morphology [5,6,7,8]. To reduce these microstructure disadvantages of the surfaces as well as to impose an effective control over the surface roughness and porosity, the nanoscale modifications have been recommended

Methods

Results

Conclusion