Experimental Investigation of Critical Heat Flux on Different Surfaces at Low Pressure and Low Flow

Ladislav Suk,Taron Petrosyan,Kamil Stevanka,Daniel Vlcek,Pavel Gejdos

doi:10.3390/en13195205

Ladislav Suk, Taron Petrosyan + Show 3 more

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https://doi.org/10.3390/en13195205

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Abstract

Steady state flow boiling experiments were carried out on several heated tubes with outer diameter 9.14 mm at outlet pressures 120, 200 and 300 kPa, inlet temperatures 64, 78 and 91 °C and approximately 400, 500, 600 and 800 kg/(m2·s) mass flux entering the vertically aligned test annulus until critical heat flux (CHF) was reached. The tubes were made of Inconel 625 with a length of 400 mm. The Inconel tubes were tested in three different modifications as smooth, abraded with 150 grit sandpaper and bead blasted. Multiple experiments were repeated on the same specimen to investigate the effect of surface characteristic changes (i.e., wettability, roughness and oxide layer morphology) on the occurrence of CHF. Despite the changes in initial wettability, the CHF dependency was not clearly observed, however, the changes in roughness led to an increase in CHF. The total number of 115 experimental runs were collected and the results were also compared with other literature experimental data.

Highlights

The critical heat flux (CHF) causes a fast reduction of heat transfer coefficient with a rapid increase of cladding temperature, which may lead to physical failure of the heated material
The results indicated that CHF of nanofluid flow boiling is enhanced compared with base fluid
The critical heat flux experiments were performed on the Inconel 625

Summary

Introduction

The critical heat flux (CHF) causes a fast reduction of heat transfer coefficient with a rapid increase of cladding temperature, which may lead to physical failure of the heated material. As a departure from nucleate boiling would damage the fuel claddings, a safety margin from CHF has to be kept during reactor operation, leading to a limitation on the reactor power. A lot of pool boiling CHF were measured with the main goal of comparing a variety of materials with different surface characteristics (i.e., wettability, roughness, porosity and oxide layer morphology). Pool boiling studies showed a strong agreement on the impact of surface morphology on CHF. It can be seen in the work of O’Hanley et al [1], Seo et al [2], Son et al [3], Ali et al [4], Kam et al [5] and Liang et al [6]

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