Abstract
This study determined the heat of evaporation of 1,4-dioxane aqueous solution, which is necessary to plan the absorption-type refrigeration cycle using the working medium developed by the authors and to establish a method of estimating it based on the existing forms of both components of 1,4-dioxane aqueous solution. Heat of evaporation at constant pressure (101.35kPa) and molar fraction dependency were measured and calculated during both the evaporation process in which the vapor-liquid composition remained constant and the process in which the composition changed, in consideration of the liquid structure of 1,4-dioxane aqueous solution. The measurements and calculation results were compared with existing heat of evaporation data and led to the following results: (1) The mean difference in heat of evaporation was 2.07% between the value calculated using calculation software (UNIFAC method) that simulated a certain amount of evaporation in vapor-liquid equilibrium at low pressure and the value determined by experiments. (2) The mean difference in heat of evaporation was 3.35% between the value determined from total evaporation using TG-DSC and the value calculated from the approximate expression of the relation between cumulative heat of evaporation of partial heat of evaporation and cumulative sample evaporation. (3) The mean difference in heat of evaporation between the value calculated as molar fraction means of both components of the simple mixture model and (1) or (2) was 2.55% and 3.41%, respectively. In conclusion, the heat of evaporation of 1,4-dioxane aqueous solution can be estimated as molar fraction means of both components of the simple mixture model as an ideal mixture of normal liquid.
