SYNOPSIS In the dairy industry, ice bank tanks are used for chilling water to 1°C. The chilled water is then used for cooling milk from its arrival temperature of between 5°C to 12°C down to a temperature of 4°C and also for cooling during the pasteurisation process. An ammonia based vapour compression system is used to chill the water. The load on the plant is not constant throughout the day since the arriving milk temperature and quantity are not fixed. Hence, during part load conditions, ice builds up considerably in the ice bank tank. This results in reduced heat transfer rates and other flow problems. However, the ice build-up to a certain level is beneficial, as it helps to meet sudden demands from the load side. Beyond this level, though, problems occur as more ice is accumulated. In the present work, the load from the chiller, pasteuriser and thermal resistance due to ice build up on the evaporator coil is calculated for a week. This has been undertaken to determine the additional energy spent in storing cold in the form of ice blocks. An ice flake thickness of 50 mm is considered to be the optimum. Further build-up can be controlled by operating the compressor for the time needed according to the load. This paper brings out a method to prevent the ice layer thickness exceeding 50 mm by running the compressor according to load fluctuation, thereby achieving a power saving.
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Kumar et al. (2001) studied this question.