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ThesisItem Open Access Thermal modeling of asymmetric overlap roof greenhouse for year round microclimate control(Punjab Agricultural University, Ludhiana, 2017) Amanpreet Singh; Sethi, V. P.In this study global solar radiation availability and thermal model for newly developed asymmetric overlap roof shape of greenhouse was developed. A mathematical model for global solar radiation availability was utilized to compute monthly average daily solar radiation, hourly solar radiation and instantaneous solar radiation; the computed values of solar radiation were utilized in dynamic thermal model to ascertain hourly plant and inside air temperature. Newly developed shape was also compared with previously developed two best shapes of greenhouse viz. even-span and modified arch in terms of solar radiation capture and for inside plant and air temperature buildup. Experimental validation of both the models is carried out for the measured instantaneous solar radiation, plant and inside air temperature for an east-west orientation, asymmetric overlap roof greenhouse (for a typical day in summer) at Ludhiana (310N and 770E) Punjab, India. The per cent difference between predicted inside air temperature and the average of measured values ranged from 0.49 to 24.58 with root mean square error of 5.69. The difference between the measured and predicted values of plant temperature varies from 3.96 to 26.99 per cent with root mean square error of 3.7. During the experimentation, tomato crop is grown inside the greenhouse and modified fan-fogger evaporative cooling system was installed and operated in sequence with different combinations of back side screen net (40×40 mesh size) and assorted sequential timings of on/off operations of fan-fogger. In this study, three different combinations of back side screen net with operational timings of fan-foggers combinations were employed and in order to optimize the operation time of fans and foggers, different combinations of operational time at fixed back side screen opening were also tested. By using modified fan-fogger evaporative cooling system, inside air temperature (Tai) drop was 120 C in twelve minutes during peak hours of solar load. During summer months of May and June, modified fan-fogger evaporative cooling system extracts heat at the rate of 9-10 kW to maintain inside air temperature lower by 8-90 C as compared to ambient air. Optimum value of cooling efficiency of modified fan-fogger evaporative cooling system comes out to be at 6 feet back side screen net slot and at 25 seconds of total operational time of MFFECS.ThesisItem Open Access Performance Evaluation and Thermal Modelling of Box Type Multi-Shelf Inclined Solar-Cooker-cum-Dryer(Punjab Agricultural University, Ludhiana, 2017) Manpreet SinghIn this study, a multi-shelf box type inclined solar cooker-cum-dryer (ISCCD) was developed and experimentally tested. The global solar radiation availability as well as thermal model has been developed for selected latitudes. For calculating monthly average daily solar insolation, hourly solar insolation and instantaneous solar intensity captured by ISCCD, a mathematical program using FREEMAT was developed. The model validation was carried out for different ISCCD parameters such as; upper and lower glass cover temperature, chamber air temperature, absorber plate temperature and temperature of water in the cooking vessel. The heat transfer analysis of parallelepiped cooking vessel was also performed. The top, side and bottom loss coefficients of ISCCD were calculated to find out overall heat loss coefficient which further used in evaluation of thermal efficiency. The cooking performance of ISCCD was tested as per BIS standards (IS Code – 14329) and observed that F1, F2 and tboil were 0.13, 0.45 and 194 minutes respectively. It was also concluded that inclined surface of ISCCD captures maximum incident solar radiation as compared to horizontal surface. Drying performance of ISCCD was evaluated by drying amla (gooseberry) with natural and forced convection drying (with medium (1.8 m s-1) and high speed (3.6 m s-1) of fan). For each case, the experiment was carried out with and without using north facing booster mirror to calculate moisture content, drying rate and drying time. Forced convection with medium speed of fan (1.8 m s-1) using booster mirror took less time (10.5 hrs) to reach equilibrium moisture content (1.66 % db). The Logarithmic model was found best by obtaining the determination of coefficient (R2) and standard error estimate (SEE).ThesisItem Open Access Computational Fluid Dynamics Analysis on Heat and Fluid Flow of Square Wave Profile Transverse Rib Roughened Solar Air Heater Duct(Punjab Agricultural University, Ludhiana, 2017) Inderjeet Singh; Sukhmeet SinghIn this investigation, the thermal and hydraulic performance of solar air heater duct roughened with non-uniform cross-section square wave profiled transverse rib is carried out using Computational Fluid Dynamics software ANSYS Academic Research CFD 15.0. The 3-D investigation considered parameters as relative roughness pitch from 4-30, relative roughness width from 10-310, relative roughness height from 0.015-0.043 and Reynolds number from 3000-15000. The turbulence model RNG k-ε with enhanced wall treatment and one periodic length was selected for analysis. The CFD methodology has been validated with the experimental results available in literature. The maximum enhancement in Nusselt number and friction factor over smooth duct was found to be 2.22 times and 3.40 times respectively at relative roughness pitch of 10, relative roughness width of 85, relative roughness height of 0.043 and Reynolds number of 15000. The maximum thermohydraulic performance parameter was found to be 1.49 at relative roughness pitch of 10, relative roughness width from 85, relative roughness height from 0.043 and Reynolds number of 12000.