I Chaer

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.

Combined heating refrigeration and power system in food industry

AbstractThe paper describes an analysis of the application of a combined heating, refrigeration and power (CHRP) system to the chilled food industry from the perspective of energy, economic and environmental factors. It is based on theoretical and practical findings from a CHRP research project at Brunel University. The CHRP test facility employs an 80 kWe modular microgas turbine producing electrical and thermal energy for process and site use with excess heat converted into refrigeration via a 12 kWc thermally driven low temperature absorption refrigeration unit.A 1000 kg h–1 chilled dairy product plant has been considered for the analysis. The plant has energy demand of 52˙5 kWe for electrical power, 36 kWth for process heating and 55 kWc for process cooling. For the plant selected, the use of the CHRP system can provide annual primary energy savings of 27%, payback time of 3˙7 years and CO2 emission savings of 76 t per annum based on utilisation of one unit of microgas turbine and five units of absorp...