Effect of brine concentration on freezing time and energy consumption of an outdoor-AC-based ice-making system

Abstract

This study investigates the effect of brine concentration on the freezing performance of an ice-making machine based on a modified outdoor air-conditioning (AC) unit. The experimental system employed a parallel copper-tube evaporator immersed in a brine solution to extract heat from 10 kg of freshwater packaged in 500 g portions. Three brine concentrations—10%, 20%, and 30%—were evaluated under comparable initial conditions. The study's contribution is an integrated experimental assessment of freezing time and total heat-transfer rate across different brine concentrations in an outdoor-AC-based ice-making configuration. The results showed that freezing time decreased from approximately 6 h at 10% concentration to 3.5 h at 20% and 3 h at 30%, corresponding to a 50% reduction between the lowest and highest concentrations. In the representative first trial, the calculated total heat-transfer rate increased from 303.59 W at 10% to 503.63 W at 20% and 615.67 W at 30%. Recorded electricity consumption also decreased from 1.86 to 1.37 and 1.03 kWh per batch, respectively. These findings indicate that, within the tested operating conditions, the 30% brine solution provided the shortest freezing time, the highest calculated heat-transfer rate, and the lowest recorded electricity consumption. The results demonstrate the potential of brine concentration adjustment to improve the operational performance of outdoor-AC-based ice-making systems. Further validation using all experimental repetitions and statistical analysis is required to establish the reliability of the observed differences.