Free convection experiments in water and deuterated mixtures at temperatures including the density maxima

An apparatus designed to perform free convection experiments in cylindrical liquid samples under strictly controlled boundary conditions is described. Convection experiments are carried out by measuring at the centre of the sample temperature vs time, as monitored by a thermocouple and a computer on-line device. The system water-deuterated water has been investigated in temperature ranges including the density maxima of the samples and compared, only in the case of pure water, with theory. Previously observed anomalies of the convective behaviour in this range are confirmed in the form of typical 'plateaux' and thoroughly examined to provide new information about the density maximum of isotopic mixtures. A new effect of a faster cooling appears, near the maximum density, when the boundary temperature is brusquely increased. © 1990.SCOPUS: ar.j