Application of Engine-Driven Heat Pumps to Grain Drying with Refrigerated Storage: Final Report

摘要

An engine driven heat-pump unit was built and used in a barley drying/storage system. Chilled air was used to prolong the storage life of undried grain, while air heated by the engine and heat-pump was used to dry the grain. When the unit was not chilling grain, exhaust air from the dryer was recycled over the evaporator to the inlet of the heating section to give higher drying temperatures and improved drying efficiency. In this way it was proposed to defray the increased capital cost of a heat-pump dryer over a longer season than with conventional dryers. Temperatures, pressures and fuel and refrigerant flows were recorded using micro-computer-based data logging system. Specific energy consumption was 4.7 to 5.1 MJ kg sup -1 of water evaporated in open-cycle drying. This was improved to 4.0 MJ kg sup -1 under full recirculation. Primary Energy Ratios of 1.1 to 1.2 and refrigerant cycle COP's of 4.1 to 4.6 were observed. The low PER's arose from using a petrol engine with a low thermal efficiency. The existing rig gave energy savings of 10 to 15% over conventional drying systems; with an efficient diesel-engine drive this could be raised to 47 to 55%. This would make the unit a viable economic alternative to conventional drying, especially if its size were increased. 23 refs., 24 figs., 34 tabs. (ERA citation 13:009003)