ABSTRACT
Pool boiling heat transfer at a single horizontal tube with large diameter (88.4mm) and superimposed convective flow of bubbles and liquid from below has been investigated experimentally simulating the convective effects caused by bubbles and liquid streaming upwards within a shell-and-tube evaporator. The boiling liquids are Propane, n-Butane, i-Butane and binary mixtures of these.
The additional convection of the vapour bubbles significantly increases the heat transfer coefficients at low heat fluxes, above all for the mixtures. The well known deterioration of heat transfer with mixtures below the molar average of the heat transfer coefficients of the pure components may entirely be compensated at low heat fluxes, where heat transfer is dominated by convective effects.
The data for this domain can be represented by a calculation method taken from the literature and having been modified. Local measurements of the circumferential variation of the wall superheat and calculations of the local heat transfer coefficients show, however, that some of the assumptions of the calculation should be revised.
