Development of passive evaporative cooling systems for tomatoes Part II: performance evaluation

Abstract

Six evaporative coolers were developed for tomatoes using Laterite-Sawdust (LS), Cement-Sawdust (CS), Cement-Eggshell Ash-Sawdust (CES), Laterite (LL), Metal-Laterite (ML) and Concrete (CR) as construction materials. The cooling efficiencies of the units were evaluated with and without being loaded with tomatoes. The result of a 7-day zero loading test showed that the cooling efficiencies of the coolers were in the order of 98.0, 92.3, 81.4, 78.0, 76.6 and 61.2% for LS, LL, CS, ML, CES and CR respectively. The 30-day loading test showed that the coolers were able to extend the shelf life of tomato beyond the 14 days recorded for ambient storage at average temperature and relative humidity of 32^oC and 42.3% respectively. Shelf lives of 26, 30,20,20,26 and 23 days were recorded for LL, LS, ML, CR, CS and CES coolers respectively at average temperatures of 24.4,24.1, 25.1, 27.7, 25.2 and 25.6^oC and corresponding RH of 93.7, 95, 93, 88.3, 92.8 and 91.8% respectively. The laterite- sawdust cooler provided the best, while the concrete cooler provided the least acceptable cooling conditions.

Keywords: Agro-forestry residues, tomato storage, composite materials, evaporative cooler