Enhancement of Heat Transfer Due to Decay of Unstable State of Solution

The article elucidates characteristic features of heat transfer during rapid transfer of single-phase solution beyond the liquid-liquid spinodal. It also investigates particularities of the thermal response accompanying decay of unstable state. The objects of the study were aqueous solutions of polypropylene glycols and ethylene glycol monobutyl ether. Controlled pulsed heating of probe was applied, based on the thermal mode of probe temperature stabilization at a given temperature T ^st. The temperature stabilization stage lasted for 20 to 100 ms; the temperature T ^st was increased step by step from the initial value T ⁰ up to 673–773 K. The values of the instantaneous coefficient of heat transfer to pure components and their solutions were calculated from the primary data. At a certain degree of superheating, a temperature-threshold effect of heat transfer enhancement up to 2–3 times was found, which is associated with the decay of unstable state of the solution. The fundamental possibility was revealed for determination of approximation for the lateral and upper spinodal branches, reconstructed on the basis of the characteristic change in the response signals. The concentration of the solution was changed step by step in the zone of compositions lying under the liquid-liquid equilibrium line.