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ThesisItem Open Access Thermal modeling and performance evaluation of north wall reflective multi-tray cabinet solar dryer(Punjab Agricultural University, Ludhiana, 2019) Spall, Saloni; Sethi, V.P.In this study, an innovative design of front loaded multi-rack tray (MRT) solar cabinet dryer with north wall reflector (NWR) having two shelves and four trays (of 125 × 75 cm each) is presented for efficient drying operation at domestic and small scale commercial level. The total drying area of the polycarbonate sheet covered MRT solar cabinet dryer is 3.75 m2. Aluminized reflector sheet is used on the north wall of the dryer to enhance the solar radiation capture by utilizing the reflective component of the beam radiation particularly in winter conditions when conventional solar dryers are not able to perform the drying operation due to smaller solar radiation availability at latitudes of 30°N and above. The modified global solar radiation was developed to determine the effect of NWR onto the solar radiation capture by the dryer. A thermal model was also developed by writing energy balance equations for dryer chamber air (Tch) and crop surface temperature (Tc). Mathematical equations were solved using Modified Euler’s method by writing a computer program on FREEMAT software. The experiments were conducted under natural convection as well as under forced convection mode with and without using the NWR during winter and summer conditions in order to ascertain the effect of NWR on the performance of dryer. The validation of predicted results were performed using the experimental data generated in winter and summer conditions at Ludhiana climate (30.56°N latitude), India. Performance parameters such as; total heat loss coefficient, useful heat gain and thermal efficiency of the MRT solar cabinet dryer were also computed and compared with that of conventional dryer without using the NWR during winter as well as in summer. The results obtained showed that by using NWR, 37.5% solar radiation capture is enhanced in January month (at 30.56°N latitude) resulting in 4-7°C and 2-5°C higher chamber air temperature under natural and forced convection modes respectively. The total reduction in drying time for carrot drying was observed as 17.8% and 14.3% under natural and forced convection modes respectively by using NWR. The predicted and experimental values for crop surface and chamber air temperature were successfully validated with RMSE and 2 values ranging between 1.6 to 4.9. The Wang & Singh and Logarithmic drying models showed best adequacy of fit due to maximum value of R2 (0.991 to 0.999) and least value of SEE (0.002 to 0.004).ThesisItem Restricted Performance evaluation and analysis of forced draft paddy straw bale combustor for heating applications(Punjab Agricultural University, Ludhiana, 2018) Biswajeet Singh; Sethi, V.P.In this study, performance evaluation and analysis of predesigned forced draft paddy straw bale combustor (FDPSBC) furnace with intermittent pilot fuel injection system (PFIS) and embedded heat exchanger for generating high temperature flue gas for water heating and utilizing heat of generated flue gas and hot water to heat the greenhouse through the predesigned flue gas heat sink pipe network (FGHSPN) and hot water heat sink pipe network (HWHSPHN) is presented. Complete combustion of compressed bale of 20kg is achieved with the use of PFIS which delivered 1.5ml of diesel after every 3 min to maintain the flame sustainability.Stainless steel heat-exchanger has 62L water holding capacity circulating at the rate of 36 litre per min using the heat of flue gas and has the capacity to heat 1000L of water within three hours. Heat of combustion (>90% combustion efficiency)was utilized to generate flue gas at 350°C and hot water above 65°C applied to 100 m2area greenhouse heating located at Punjab Agricultural University, Ludhiana (30.56°N), Punjab, India by the predesigned two heat sink pipe networks; FGHSPN andHWHSPN laid inside the greenhouse for transfer of heat by radiation and free convection modes. Heat transfer models were developed to carry out the heat transfer analysis of combustor furnace, FGHSPN and HWHSPN. Developed mathematical models showed that insulation provided inside the combustor furnace reduced the heat loss by 91.7% through the combustor furnace wall whereasFGHSPN performed much better as compared to HWHSPN and was able to transfer 9.6 kW (74%) whereas HWHSPN could transfer 3.38 kW (26%) of heat respectively out of the total heat (12.98 kW) generated by both the networks to maintain the greenhouse air temperature 10°C higher than the ambient air temperature after sunset hours as validated by experimental trials conducted on 29 of November,2017 with a RMSE of 3.44.ThesisItem Restricted Computational Fluid Dynamics of Solar Air Heater Duct Roughened with Multiple Arc Rib having Gap and Staggered Rib Piece(Punjab Agricultural University, Ludhiana, 2018) Amanpreet Kaur; Hans, V.S.Artificial roughening of solar air heater duct wall is the effective method which leads to significant enhancement in heat transfer as well comparable rise in friction losses. The different investigations have been performed by various authors to study the heat transfer rate and friction factor characteristics. In this present study, a numerical investigation is carried out using Computational Fluid Dynamics software ANSYS Academic Research CFD 15.0 to determine the heat transfer rate and thermo-hydraulic performance of rectangular solar air heater duct roughened with multiple arc rib having gap and staggered rib piece. The parameters considered were relative roughness pitch of 8, relative roughness height of 0.043, relative roughness width of 5, relative gap width of 1, arc angle of 60° and relative staggered rib size of 4. The investigation encompassed for the Reynolds number and relative staggered rib pitch range from 2000 to 18000 and 0.2 to 0.8 (4values) respectively. The maximum enhancement in Nusselt number and friction factor was observed to be 3.38 and 6.2 times as compared to smooth duct at relative staggered rib pitch of 0.4. The maximum thermo-hydraulic performance found to be 1.83 for relative staggered rib pitch of 0.4 at Reynolds number of 12000.ThesisItem Open Access Development of a thermal model and performance evaluation of twin-chamber community solar cooker(Punjab Agricultural University, Ludhiana, 2017) Sekhon, Mandeep Singh; Sethi, V.P.In this study, a twin-chamber community solar cooker is experimentally evaluated and global solar radiation availability and thermal model has been developed for selected latitudes and different seasons of the year. A mathematical program was developed and utilized to compute monthly average daily solar insolation, hourly solar insolation and instantaneous solar intensity captured by the solar cooker for use in the developed thermal model. The computed values of solar radiation were validated for 300N latitude (Ludhiana) and were found to be in close proximity with the predicted values. The solar radiation captured was utilized in developed thermal model by solving energy balance equations and validating them for chamber air and absorber plate temperature. The cooker was tested as per BIS standards (IS Code – 14329) for calculation of first figure of merit (F1), second figure of merit (F2) and standard boiling time (τ). It was observed that F1, F2 and τ were 0.128, 0.41 and 181 minutes respectively which shows that the designed cooker is ‘A’ grade cooker. Economic analysis was performed to compute the payback period and net present value and it was observed that the cooker can save 47 cylinders or 668 kg of LPG in one year. Environmental impact analysis was also performed to compute the carbon credits earned by using the designed solar cooker in substitution of conventional cooking fuels. It was observed that carbon credits earned in a year in substitution of fuels like cow dung cake, wood and LPG were 5.9, 4.1 and 2.0 respectively.