NUCLEATE POOL BOILING OF BINARY MIXTURE

Abstract

This investigation contains experimentation on nucleate pool boiling of acetone, distilled water and their binary mixture over a copper heating tube surface coated with 43 thicknesses of copper at atmospheric and sub-atmospheric pressures. The effect of operating parameters — heat flux and pressure of coating on boiling heat transfer coefficient of various liquids on coated tube surfaces have been evaluated. The experimentation includes saturated boiling of liquids of widely varying physico-thermal properties from an electrically heated horizontal copper tube of 18 mm I.D., 31.94 mm. 0. D. and 150 mm effective length. It has been coated with copper by means of electroplating technique. Liquid bulk temperature have been measured by placing thermocouple probes outside superheated boundary layer surrounding the heating tube corresponding to surface thermocouples' positions. e.m.f. of thermocouples are measured by digital multimeter. Adequate precautions have been taken to ensure radial flow of heat from heating surfaces to liquid pool and to minimize heat loss to surrounding. Standard operating procedure followed to conduct experiments. The operating parameters include heat flux ranging from 240 W to 640 W and pressure from 44.20 kN/m2 to 97.95 kN/m2. Analysis of experimental data on plain heating tube clearly show that surface temperature increases from bottom to side to top position for a given value of heat flux at atmospheric and sub-atmospheric pressures. However, liquid temperature remains uniformly constant at all values of heat flux for a given pressure. Average value of heat transfer coefficient of plain heating tube related with heat flux by the power law relationship h a q° and thereby corroborates findings of earlier investigators [ 4 ,18 ,19 ,33 ,34 ,39 ,56 ,62, 83, 92, 105, 149, 150 ]. Further various dimensionless correlations given by different investigators [ 4 ,8 ,16 ,33 ,34 ,39 , 105, 106,148 , 149 ] have been tested against data of present investigation. On the basis of above, it has been concluded that boiling heat transfer correlation developed for a set of liquid surface combination by an investigator can not be used to correlate experimental data of other investigators due to the presence of surface-liquid combination factor.