Improving the efficiency of low cost dehydrator using ventilation waste heat recovery unit.

摘要

Drying is the process of removing moisture from a product with the idea of preservation and to protect the quality and to lower the weights. Different types of drying techniques are followed among which use of dehydrators is most common method. A low-cost dehydrator was built considering the lethality step in the processing of drying meat. This study concentrates on determining the energy efficiency and heat energy recovery from the exhaust stream of a low-cost dehydrator. Two different conditions(C-II and C-III) of operations, one without air recycle (C-II) and one with air recycle (C-III) were tested for heat recovery using a house hold heat recovery ventilator (HRV). The products used in the whole drying process in different conditions of operation were the Oklahoma grown spices cilantro and basil. The study also focuses on the best condition for drying basil and cilantro in the process of retaining volatile compounds.;Efficiency of the low-cost dehydrator was determined at C-I and was found to be 51, 57.3 and 52% at 60, 70 and 75oC respectively. Effectiveness of using a HRV to recover the waste heat from the exhaust stream of a dehydrator was studied. By using C-III, the efficiency was higher at each operation temperature and was 66, 71 and 64% at 60, 70 and 75oC respectively. In case of C-II, there was a decrease in efficiency compared to C-I due to increase in flow rates as high amount of heat is wasted in exhaust stream. At 75oC, C-III operating temperature, high amounts of volatile compounds were retained in cilantro which is preferable. In the case of basil, low temperature and less flow rates were good. 60oC, C-I was found to be the best operating condition to dry basil where the high amounts of volatile compounds were retained.