Fish drying : simulated natural convection drying

Abstract

A dryer prototype was built based on commercial natural convection dryers using agricultural waste as the energy source. In addition, a pre-conditioning plenum was built to control the humidity and temperature of input air. The plenum used salt solutions to provide an artificially humidified air with relatively constant properties. The effects of multiple trays per batch, drying temperature and resistance to air flow, on fish drying rates were studied. These studies were limited to the constant drying rate period only. The results of the study on the effect of multiple trays showed that for a two tray arrangement, the means of the drying rates corresponding to tray 1 and tray 2 show borderline significant difference at the 95 percent, confidence level. For the three tray drying arrangement, the mean drying rate for tray 1 was significantly different from the mean drying rate for tray 2 and tray 3 for all drying temperatures studied. Similarly, the mean drying rate for tray 2 was significantly the same as the mean drying rate for tray 3. The results of the drying temperature study showed that the mean fish drying rate at 50°C was higher than that at 40°C. Similarly, the mean drying rate at 40°C was higher than that at 30°C. The results of the resistance to flow study showed that the mean air velocities for 20 percent and 40 percent void spaces were significantly different at all temperatures. Means for 40 percent, and 60 percent void spaces were significantly different only at 30°C. Means for 20 percent and 60 percent void spaces were significantly different at 40 and 50°C. A fish drying model was derived based on the method by (Brooker et al., 1978) for grain drying. An empirical approach to explain the thin layer drying of fish fillets (of about 0.728 to 0.879 cm thickness) was proposed.