Utilization of Greenhouse (Lean-to Structural Frame) as a Solar Dryer for Drying Lemon Fruits Part I: Drying Process under High Air Temperature.

Abstract

A solar lean-to greenhouse dryer was designed, constructed and tested for drying lemon fruits at the experiments and researches field, Faculty of Agriculture, MansouraUniversity (latitude and longitude angles, respectively, are 31.04ᵒN and 31.35ᵒE, and 6.72 m mean altitude above the sea level). In this study a new concept has been taken into consideration to maximize the greenhouse effect (thermal trapping) by using architectural form of lean-to greenhouse structural frame. The experimental work was carried out from 21st to 26th of August 2016. The obtained results showed that, using the northern wall reflector caused in increasing both the intensity of solar radiation inside the dryer and the indoor air temperature by 36.30% and 60.90%, respectively. The daily average solar radiation incident outside and inside the solar dryer were 5.188 and 3.383 kWh, respectively with effective transmittance of 65.21%. Using the northern reflector wall increased the daily average indoor solar radiation by 36.12%. The daily average outdoor and indoor air temperatures were 30.1 and 48.4oC, respectively. Accordingly, the solar dryer increased the indoor air temperature over the outdoor by 60.80%. These conditions of solar dryer caused in decreasing the daily average air relative humidity from 67.31 to 28.38% with reduction percentage of 38.93%. Three different shapes of lemon fruits (slices, half and whole lemon) was dried from initial moisture content of 87.04% (w.b.) to the final moisture of 17.30, 17.38 and 17.69% (w.b) within 3, 5, and 6 days, respectively.