Influence of Fuel Cladding Material Surface Condition on Heat Transfer Coefficient in ETRR-2 Research Reactor

Abstract

In this work both the effects of surface conditions and type ofboiling fluid on the pool boiling heat transfer coefficient from upward aluminum alloy 6061 heating surfaces are investigated. For this purpose, a test apparatus has been designed and constructed to achieve heat transfer measurements from seven horizontal aluminum alloy 6061 plates. The first four plates are treated mechanically usmg different grained emery papers, while the remaining three plates are treated chemically by HCI acid .Demineralized water and acetone are used as the boiling fluids. Experiments are canied out under the condition of saturated pool boiling, under constant boiling pressure of 0.7 bar for both demineralized water and acetone, which conesponds to boiling temperature 90 °C and 46 °C respectively. I A detailed analysis of the experimental results ensures that the influence of the different surface conditions achieved, either mechanically by different grained emery papers or chemically by HCL acid, on the absolute value of the heat transfer coefficient (h) can not be con•elated by one of the roughness parameters used in literature within the whole range of heat flux. A three parametric distribution functions N (r) for the size of the stable vapor bubble in active nucleation sites are obtained for the seven tested plates using the heat transfer measurements. An attempt has been made to find the relationship between the distribution functions constants and the surface roughness parameter (Rp) measured directly by a profilometer.