Calorimetry based temperature and specific enthalpy measurements associated with ice-water phase change in saline systems for freeze desalination

Abstract

Ice based Freeze Desalination (FD) offers a potential alternative to recover fresh water from seawater. However, ice-water phase change data in saline water in the range of practical interest and of importance in FD process design is limited. In this study, reliable and accurate measurements related to ice–water phase change temperatures and specific enthalpies have been carried out using a Micro–Differential Scanning Calorimeter (μ–DSC). The runs were carried out using pure water, synthetic salt water (0.5 to 5 wt% NaCl) and seawater. The NaCl concentrations covered a range of values of practical interest in FD. In the case of pure water, the specific enthalpy value was found to be in excellent agreement to within ± 0.51% of the value reported in literature, i.e. 333 J/g which validated the experimental protocols adopted in this study. Phase change temperature and specific enthalpy values for salt water were found to decrease with an increase in salt concentration. Test runs conducted subsequently using seawater were consistent with the results obtained from the synthetic salt water test runs. The experimental protocol adopted and data presented in this study can be used in design of an ice based FD process.

Keywords

• Desalination
• Specific enthalpy
• Temperature
• Phase change
• Differential scanning calorimetry (DSC)