THERMAL INSTABILITY OF A HORIZONTAL LAYER OF LIQUID WITH MAXIMUM DENSITY

An investigation is carried out to determine the onset of convection of a horizontal layer of liquid subject to temperature of T1 and T2 at lower and upper surfaces, respectively. The liquid is assumed to possess a maximum density value at Tmax with Tmax between T1 and T2. The temperature‐density relationship within the temperature range |T1 — T2| can be expressed as ρ = ρmax [1 — γ1 (T — Tmax)2 — γ2 (T — Tmax)3]. Both rigid‐rigid and rigid‐free surface conditions were considered. The critical Rayleigh number defined in Equations (20) and (24) is found to be dependent upon two parameters. Experimental observations on the onset of convection were made and compared with the theoretical results. The experimental work consists of the measurement of the melting rate of a block of ice with melting from both below and above. In all cases, excellent agreement between experimental and theoretical results were obtained. Copyright © 1969 American Institute of Chemical Engineers