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Articles by G.N. Tiwari
Total Records ( 6 ) for G.N. Tiwari
  Anil Kumar and G.N. Tiwari
  In this present study an open sun and greenhouse drying of onion flakes has been performed to study the effect of mass on convective heat transfer coefficient. Three sets of experiments with total quantity of onion as 300, 600 and 900 g were done. The onion was continuously dried for 33 h both in open sun and in the roof type even span greenhouse with floor area of 1.2 x 0.78 m2. Experiments were carried out during the months of October to December 2003 at IIT Delhi (28°35`N 72°12`E). Experiments were started at 8 am. The data obtained from experimentation under open sun and greenhouse conditions have been used to determine values of the constant `C` and exponent `n` by regression analysis and consequently, convective heat transfer coefficient. It is observed that there is a significant effect of mass on convective heat transfer coefficient for open as well as greenhouse drying. It is also observed that the rate of moisture evaporation in case of greenhouse drying is more than that in open sun drying during the off sunshine hours due to the stored energy inside the greenhouse. The experimental observations were analyzed in terms of percentage uncertainty also.
  Anil Kumar and G.N. Tiwari
  This communication presents the thermal modeling for the greenhouse drying of jaggery under forced convection mode to predict the jaggery temperature, the greenhouse air temperature and the moisture evaporation (jaggery mass during drying). The parametric study has also been performed to find the effects of various parameters namely number of air changes/h, relative humidity and mass of the jaggery. The jaggery cubes (total mass of 2.0 kg) having dimensions of 0.03 x 0.03 x 0.03 m3 has been dried in the roof type even span greenhouse with floor area of 1.20 x 0.78 m2 during the month of March, 2004 at IIT Delhi (28°35`N 72°12`E) from 10 am to 5 pm. The jaggery temperature, the greenhouse air temperature and the moisture evaporation have been calculated theoretically in terms of design and climatic parameters by using the MATLAB software. The theoretical results have been experimentally validated and a fair agreement has been observed between the theoretical and experimental results.
  Anil Kumar , G.N. Tiwari , Subodh Kumar and Mukesh Pandey
  The present study is concerned with the scope of greenhouse technology in agricultural engineering (cultivation, drying and space heating). The greenhouse can provide control environment for high value crops like medicinal plants, flowers etc. crops grown inside a greenhouse are healthy and give better results. The design of a greenhouse depends upon the latitude of the place and the requirement of crop. The main criteria for selection of greenhouse can be its value of solar fraction, which have been discussed in detail in the article. Depending upon the requirement of crops, different heating and cooling arrangements can be made in inside the greenhouse. Drying is a widely used practice in food preservation. Drying of crop/fruit/medicinal plants inside a greenhouse is also very useful technique for reducing postharvest losses, due to undesirable moisture contents. The study also highlights the application of greenhouse for drying under natural as well as forced mode.
  Nisha Kumari , G.N. Tiwari and M.S. Sodha
  This study presents thermal modelling of rock bed with water for heating agricultural greenhouse. Numerical computations have been carried out for an east-west oriented even span greenhouse for New Delhi (28.5° latitude), India. Effect of void bed fraction, area of collectors on plant, room air, water and rock bed temperatures have been studied in detail. On the basis of numerical results, it is inferred that the plant, room air and water temperatures of the greenhouse increases significantly with the increase of collector area and decreases with the increase of void bed fraction, while rock bed temperature increases with the increase of void bed fraction.
  Tribeni Das , G.N. Tiwari and Bikash Sarkar
  This study describes thermal modeling and its validation of greenhouse fishpond system connected with and without Flat Plate Collector (FPC). Numerical computation has been performed for a typical winter day in the month of December, 2005. The energy balance equations have been written considering the effects of conduction, convection,radiation, evaporation and ventilation and these equations are numerically solved with MATLAB 7.0 software to predict the room and water temperature. A parametric study has also been performed to find the effects of water mass and number of collectors. There is significant effect on water temperature at different water depths due to change in the number of collectors. The results showed that a rise of 4.13-6.92°C water temperature can be achieved for greenhouse pond connected with two number collectors and in case of without collector it was 3.12-5.64°C. Fish production in greenhouse is also significantly higher as compared to open pond. In both the cases, with and without collector predicted and experimental values of water temperature exhibited fair agreement with coefficient of correlation r = 0.96 and 0.95 and root mean square percent deviation e = 1.64 and 1.83%, respectively.
  Ashish Shukla , G.N. Tiwari and M.S. Sodha
  In this study a thermal model has been developed to see the effect of inner thermal curtain on the thermal performance of an even span greenhouse for Srinagar (34.08° N), India. The analysis incorporates the study of thermal performance of three types of greenhouses (I) single zone greenhouse (without curtain) (ii) two zone greenhouse (with one curtain) and (iii) three zone greenhouse (with two curtain). The thermal performance of a greenhouse having one and two thermal curtain has been compared with greenhouse without thermal curtain. It is seen that the fluctuations in temperature in the vicinity of plants are more in greenhouse without any curtain in comparison to other two greenhouses; whereas temperature during night time in first zone of three zone greenhouse is significantly more with comparison to greenhouse without curtain and greenhouse with one curtain.
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