ASABE Technical Library - Abstract

Abstract. Specialty crop fruit and vegetable pomaces are a common byproduct of the food processing and juicing industries. These pomaces can have high nutritional value, but are currently underutilized or treated as waste. Drum drying is one method that could be adopted to dry and stabilize fruit and vegetable pomaces for long term storage and use. Current drum drying methods utilize conventional heating mechanisms such as gas fired steam generation. However, this heating can be generated just as effectively with solar thermal power, potentially reducing operational cost for the agriculture and food processing industries. In this work a 305 by 305 mm stainless steel flat plate was used to simulate the surface of a single drum dryer. Controlled inlet temperatures (105oC to 145oC) with varying load conditions on the flat plate represent typical operating conditions seen in a drum dryer. The heating power required to operate the flat plate within the desired temperature range was calculated to be 494 W to 835 W respectively. These results were incorporated into and compared to a heat transfer model of a 4.5 m2 External Compound Parabolic Concentrator (XCPC) solar thermal collector designed to produce approximately 2 kW of heating power. Our simulations modeled the flat plate in series with the solar collector, predicting the temperature rise and power supplied to the flat plate. The XCPC collector operating at a fixed flow rate (100 g s-1) with global solar irradiance of 900 W m-2, produces a temperature rise to the system of 5oC to 8oC. Modeling the heat loss from the flat plate predicts a temperature drop of 2oC to 4oC, which agrees with experimental measurements. Analysis of the model with experimental results suggests that a single solar thermal collector can provide an adequate temperature rise to heat the solar thermal-powered flat plate system. An additional cooling power of 1.8kW is needed to maintain operating temperature once the system stabilizes. The results of this work will inform the design of a solar thermal-powered drum dryer for use in drying specialty crop purees and pomaces.