Localised air delivery to reduce energy use in the food industry

Abstract

The concept of localised air delivery (LAD) is considered in which cold air is supplied close to foods to maintain their low temperature and higher temperatures are allowed elsewhere in the production area. The concept offers improved working conditions and food safety but this paper is concerned with the potential reduction in energy use. Three metre long LAD sections were produced consisting of air supply ducts located on each side of a conveyor. Cold air passed from the supply ducts through slots. The air flow and temperature were adjusted to provide an average temperature between the ducts of 5 °C when operating in a room at 16 °C. Depths of the test sections were 100 or 200 mm and widths were 300, 500 or 670 mm. With air flow rates between 0.17 and 0.51 m 3 s −1, air supply temperatures between 0 and 4 °C, depending on the flow and geometry, were needed to achieve 5 °C between the ducts. Energy savings compared to conventional production areas operated at 5 or 10 °C (with subsequent product cooling) were estimated based on the air flow rates and temperatures measured in the experiments. Savings were up to 26% and 32% when compared to operating the production area at 5 and 10 °C, respectively. There exists the potential for greater savings through reducing the air flow rate, some redesign of the slots in the ducts, and by using LAD in areas such as transfer zones between production areas.