The design and operation of hydrocoolers: a Smart Water funded project

Horticultural produce begins to deteriorate as soon as it is harvested. It begins to lose its flavour and texture, and it is susceptible to infection by pathogens. An effective method of slowing the loss in quality is to cool the produce as soon as possible after harvest. Many crops, such as pome fruits, asparagus, broccoli, peas and beans can be cooled within half an hour or so by drenching them with chilled water in a device known as a hydrocooler. The project described in this report was initiated by Mr Nick Christou of Christou Logistical Services. He was using a water chilling unit to cool water which he sprayed onto vegetables after which the water was discharged. This procedure was a waste of water and energy. He required a hydrocooler capable of cooling up to 6 tonnes per hour of produce, and that is transportable from growing region to growing region, and which is water-efficient. The Smart Water Fund grant enabled a hydrocooler that incorporated water recirculation to be developed and built jointly by Victoria University and Wobelea Pty Ltd. The strategy of recirculating water has reduced the water consumption from a required 60,000 litres per tonne of broccoli cooled to about 75 litres per tonne. When round fruit such as apples are cooled the water consumption is estimated to be about 35 litres per tonne. Measurements show that broccoli cools by 80% of its possible cooling range, i.e. from 30ºC when sprayed with water at 0ºC, in about 35 minutes. The total electricity consumption is 20 kWh and 16 kWh when the throughputs are 4 tonnes per hour and 6 tonnes per hours respectively. If the water were not recirculated the electricity consumption would be about 300kWh per tonne. Outcomes of the project include: The design and operation of a recirculating hydrocooling system. A demonstration that the new system cools horticultural produce to temperatures that will maintain the shelf life and quality of the produce. A demonstration that the hydrocooler is capabale of eliminating contaminants from the recirculated water over brief periods of time. The identification of improvements that can be made to the design of the system. The hydrocooler is now being successfully operated in Wesley Vale near Devonport Tasmania in conjunction with Riverside Australia, Werribee