This paper presents an investigation related to enhanced boiling of saturated liquids from plain and a 26 (mu)m thick copper coated mild steel heating tube at atmospheric and subatmospheric pressures. Data analysis has shown surface temperature to increase from bottom to side to top position of a plain heating tube for a given value of heat flux at atmospheric and subatmospheric pressures. However, liquid temperature remains uniformly constant irrespective of heat flux at a given pressure. Heat transfer coefficient of a plain heating tube has been found to be related with heat flux by the relationship, h (propor. to) q~(0.7). A dimensional equation for the boiling of all the liquids: h velence C_(1) q~(0.7)p~(0.32) has been developed by the method of least squares. Experimental data on a 26 (mu)m thick copper coated mild steel heating tube for saturated boiling of water, methanol and isopropanol at atmospheric and subatmospheric pressures have been analysed and found to govern by the relationship, h (propor. to) q~(n) where n depends upon boiling liquid. In fact, its value is less than 0.7 for all the liquids. A dimensional correlation has been obtained in the form: h velence C_(2) q~(x)p~(y). The thermal performance, xi of a coated heating tube surface has been related to heat flux and pressure by dimensional equation, xi velence c_(3) q~(alpha)p~(beta). Based upon the logic of xi > 1 for the suitability of a surface, a criterion q~(-alpha)p~(-beta) < C_(3) has been established for enhanced boiling of a liquid on a mild steel heating tube surface coated with copper. This criterion can be used to determine the range of heat flux for enhanced boiling of liquids on a copper coated tube surface at a given pressure.
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