APPLICATION OF ENGINE DRIVEN HEAT PUMPS TO GRAIN DRYING WITH REFRIGERATED STORAGE
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 dryer temperatures and improve 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 the conventional dryers. Two types of dryer were used - a batch type in 1982 - 1983 and a continous flow one in 1983 - 1984. Temperatures, pressures and fuel and refrigerant flows were recorded using microcomputer-based data logging system. Specific energy consumption was 4.7 to 5.1 MJ kg**-1 of water evaporated in open cycle drying. This was improved to 4.0 MJ kg**-1 under full recirculation. Primary Energy Ratios of 1.1 to 1.2 and refrigerant cycle COPs of 4.1 to 4.6 were observed. The low PERs arose from using a petrol engine with a low thermal efficiency. High moisture grain (21.5% wet basis) remained free from penetration by storage fungi for 3 weeks at approximately 50 degrees C, but it was still suitable for animal feed after 13 weeks. The existing rig gave energy savings of 10-15% over conventional drying systems; with an efficient diesel engine drive this could be raised to 47-55%. This would make the unit a viable economic alternative to conventional drying, especially if its size were increased.
Bibliographic Reference: EUR 10303 EN (1985) MF, 146 P., BFR 300, BLOW-UP COPY BFR 730, EUROFFICE, LUXEMBOURG, POB 1003
Availability: Can be ordered online
Record Number: 1989124082400 / Last updated on: 1987-01-01
Available languages: en