Studies on Hay Dryers with Heated Air (II)

Design, Construction and Performance Tests of a Simple Heat Exchanger for a Hay Dryer with Heated Air

Abstract

In the previous report (Studies on Hay Dryers with Heated Air, (I)) the fuel cost was about 1.65yen per kilogram of dried hay, whereas the depreciation cost was 1.50 yen, in case field cured hay with 35-40% moisture content (wet basis) was used and about 10tons of hay were prepared annually. Recirculation of exhaust gas is one of the methods to increase the overall thermal efficiency and reduce the operation cost. The LP gas dryer which showed a better thermal efficiency in the previous report, however, maintained its exhaust moisture content at nearly 100% for 1/2-2/3 of the operating time which was about one hour and the high moisture content seemed adverse to a recirculation system. A simple plate type heat exchanger consisting of 23 zinc-coated roofing iron sheets was designed and tested with the LP gas dryer without any change in the heater and blower unit. About 20% of heat saving was obtained with it. Since there is a possibility of making the exchanger a compact unit for saving construction material and installation space, further improvement and experiments are intended in the future.