Design and manufacturing of a vacuum solar dryer for fish and study its efficiency


A vacuum solar dryer was manufactured and tested in the fish drying. Its consist of a black cylindrical drying chamber provided with hooks used to hanging fish in the cylinder was placed in the wood box having insulate, glass was putted on the top surface of wood box. Drying chamber, also provided with vacuum pump and temperature gauge and solar cell to production electricity energy to operate vacuum pump and temperature gauge. Intensity of solar radiation, temperature, air relative humidity, a practical and theoretical moisture content, moisture diffusion, drying rate and constant, The study was carried out on February 2012 in Agriculture College, Basrah University was by drying, fresh fish ( Cypriuns carpio) which were purchased from local market, A part of fish was salted with 2% and the other part without salt. Result showed the Inten sity of solar radiation was increased with increasing hours day and arrived to maximum value at midday and then reduced .Intensity of solar radiation mean was 765.8w/m2. Mean of temperature in the vacuum solar dryer was between 48±1.5 - 50±1.2 C° the drying in maximum heat load period from 10 am to 2.00 pm ,due to glass covering by 65% in the summer and 40% in the winter . Moisture content for salted and unsalted was significantly reduced(p<0.05) with increasing drying period, theory results was closed to practical for all drying methods. Drying rate was significantly reduced with reducing moisture content for all drying methods in the salted and unsalted fish. Water activity was significantly increased (p<0.05) with increasing moisture content for all drying methods in the salted and unsalted fish. The differences between drying method were not significant. Maximum moisture diffusion was in the salted and unsalted fish which dried by vacuum solar dryer , then vacuum electrical dryer, the differences between salted and unsalted were not significant. Drying constant in the vacuum solar drying was higher than vacuum electrical drying, than natural sun drying. Normalized daily drying efficiency was significantly reduced with increasing drying time. Vacuum solar dryer has higher efficiency in the drying of salted fish. Lewis model was fitted with moisture ratio the vacuum solar dryer, where's Modified Page and Midilli models were fitted to the vacuum electrical dryer and natural sun drying.