The groundnuts were dried inside an even span roof type free convection greenhouse dryer with a useful floor area of 1.2×0.8 m2 in the environmental conditions of Rohtak, India (28o54′-N 76o34′E). Wire mesh sieves of sizes 0.15×0.25 m2, 0.25×0.4 m2, and 0.35×0.6 m2 were used to accommodate thin layer samples of groundnuts. The groundnuts were dried till the optimum safe moisture storage level (8%-10%) was attained. Based on experimental (hourly) observations the values of constants (C and n) in the equation of Nusselt number were evaluated. The values of convective and evaporative heat transfer coefficients were calculated which were observed to decrease with the increase in the sieve size. The overall average greenhouse thermal, energy, and exergy efficiencies were evaluated as 8.83%, 22.67%, and 2.75% respectively. The overall average experimental error in terms of % uncertainty for groundnuts drying was evaluated as 37.94%. © 2019, Int. Comm. of Agricultural and Biosystems Engineering. All rights reserved.