Heat transfer and pressure drop of ice slurries in plate heat exchangers

Ice slurries can be used both for cold storage in place of chilled water or ice and as a secondary refrigerant since, up to certain concentrations, they can be pumped directly through distribution pipeworks and heat exchangers. For ice slurries to become more widely accepted, however, more engineering information is required on fluid flow and heat transfer characteristics. This paper reports on the results of experimental investigations into the melting heat transfer and pressure drop of 5% propylene/water ice slurry flowing in a commercial plate heat exchanger. Measurements were obtained for ice fractions between 0% and 25% by weight, and flow rates between 1.0 and 3.7 m3/h. In this flow range, increasing the ice fractions from 0% to 20% caused around a 15% increase in the pressure drop over the flow range tested. The overall heat transfer coefficient, based on the logarithmic mean temperature difference, was found to remain fairly constant as the ice fraction increased from 5% to 20%. The heat transfer capacity of the heat exchanger was found to increase by more than 30% with melting ice slurry flow compared to chilled water flow. In a practical application, for a given thermal load this would lead to greater than 60% reduction in flow rate and pressure drop compared to chilled water cooling systems.