The construction of a large Mach-Zehnder interferometer and its application to the study of gas liquid transfer processes

A Mach-Zehnder interferometer with 200 mm. mirrors has been designed and constructed for the study of refractive index fields. The instrument can accommodate large test-sections and is mounted on a sprung cradle to isolate it from any external vibration. Transient heat transfer phenomena occuring during evaporation and condensation in liquid vapour systems were studied, using : the inferometer to measure the temperature gradients existing adjacent to the surface. From these results values of the condensation coefficient were calculated for propyl alcohol, pure water and water with involatile contaminants. For all systems studied the calculated values of the coefficient were found to decrease as the rate of condensation increases and it was considered that this effect cannot wholly be attributed to the small quantities of air sometimes present near the liquid surface. Coefficients obtained for water during condensation were of the same order as those measured by other workers studying evaporation. Traces of sodium lauryl sulphate, a surface active agent, reduced the coefficient by a factor of about 3; a similar reduction was found for a normal solution of sodium chloride. Coefficients for propyl alcohol were less than those for water by a factor of 20. Evaporation and condensation yielded similar coefficients for all systems.