HEAT TRANSFER CHARACTERISTICS OF PROPYLENE GLYCOL/WATER BASED MAGNESIUM OXIDE NANOFLUID FLOWING THROUGH STRAIGHT TUBES an‎d HELICAL COILS

Forced convective heat transfer studies on glycol based magnesium oxide nanofluids flowing through straight tubes and helical coils under laminar flow and constant wall temperature conditions have been conducted. Propylene glycol – water mixture (60:40 by wt.%) was used as the base fluid and nanofluids with MgO nanoparticle volume concentration of 0.66% and 0.3% were used as the working fluids. Results showed that the convective heat transfer coefficient of nanofluid was higher than that of the base fluid for both straight tubes and helical coils. In straight tube, Nusselt number enhancement was 20% w.r.t. base fluid and it increased to 29% with increase in Peclet number from 44000 to 111400 for nanofluid having volume concentration of 0.66%.While in helical coils, maximum enhancement in experimental Nusselt number was found to be 19.5% and 23% at volume concentration of 0.3% and 0.66 % respectively for a curvature ratio of 0.0727 corresponding to a Dean number of 490.Two new correlations have been proposed to predict the heat transfer coefficient of magnesium oxide nanofluid flowing under laminar conditions through straight tube and helical coils.