FORCED CONVECTION GREENHOUSE GROUNDNUT DRYING: AN EXPERIMENTAL STUDY

In this study, the convective and evaporative heat transf er coefficients of groundnut were evaluated in a forced convection greenhouse drying (FCGI ID) mode. The groundnuts were dried in the roof-type even span greenhouse with a floor area of 1.20 x 0.8 m(2) in a forced mode in the climatic conditions of Rohtak, India (28 degrees 54 '0 '' N 76 degrees 34'0 '' E). Three different wire mesh trays of 0.75 x 0.25 m(2) (Sample 1), 0.25 x 0.40 m(2) (Sample 2), and 0.35 x 0.60 m(2) (Sample 3) sizes were used to accommodate a thin layer of groundnuts. Groundnuts were dried in the FCGHD mode till an optimum safe moisture storage level of 8-10% was reached. The hourly experimental data were used to determine the values of experimental constants C and n in the Nusselt number expression by simple linear regression analysis and, consequently, the convective heat transfer coefficients (CHTC) were calculated. The value of CHTC was found to decrease with increase in the tray size. The average value of the greenhouse efficiency was found to be 38.56%, 26.95%, and 31.99% for drying groundnut Samples 1, 2, and 3, respectively. The energy and energy efficiencies were also evaluated and their values were observed to be 54.45%, 77.92%, and 65% and 2.57%, 1.01%, and 0.95% for drying groundnut Samples 1, 2, and 3 in the FCGHD mode, respectively. The experimental errors in terms of percent uncertainty were also evaluated. They were found to vary from 19.62% to 64.10%. The error bars for CHTC and evaporative heat transfer coefficient (El ITC) are also shown for groundnut drying under FCGHD conditions.