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Articles by G.N. Tiwari
Total Records ( 9 ) for G.N. Tiwari
  Sujata Nayak and G.N. Tiwari
  In this paper, a study is carried out to evaluate the annual thermal and exergy performance of a photovoltaic/thermal (PV/T) and earth air heat exchanger (EAHE) system, integrated with a greenhouse, located at IIT Delhi, India, for different climatic conditions of Srinagar, Mumbai, Jodhpur, New Delhi and Bangalore. A comparison is made of various energy metrics, such as energy payback time (EPBT), electricity production factor (EPF) and life cycle conversion efficiency (LCCE) of the system by considering four weather conditions (ad type) for five climatic zones. The embodied energy and annual energy outputs have been used for evaluation of the energy metrics. The annual overall thermal energy, annual electrical energy savings and annual exergy was found to be best for the climatic condition of Jodhpur at 29,156.8 kWh, 1185 kWh and 1366.4 kWh, respectively when compared with other weather stations covered in the study, due to higher solar intensity I and sunshine hours, and is lowest for Srinagar station. The results also showed that energy payback time for Jodhpur station is lowest at 16.7 years and highest for Srinagar station at 21.6 years. Electricity production factor (EPF) is highest for Jodhpur, i.e. 2.04 and Life cycle conversion efficiency (LCCE) is highest for Srinagar station. It is also observed that LCCE increases with increase in life cycle.
  Arvind Chel , G.N. Tiwari and H.N. Singh
  The daylight factor model given by Charted Institute of Building Services Engineers (CIBSE) was modified in this paper to incorporate time variations with respect to zenith angle (θz) and vertical height (h) of working surface above ground surface which was normalized with central height (H) of skylight dome. The modified model contains constant exponents which are determined using linear regression analysis based on hourly experimental data of inside and outside illuminance for each month of the year 2007–2008. The prediction of modified model is found in good agreement with experimental observed inside illuminance data on the basis of values of root mean square percentage error (e) and correlation coefficient (r). The annual average daylight factor values for big and small dome skylight rooms are determined as 2.3% and 4.4% respectively. The energy saving potential of skylight rooms for selected climatic locations in India is also presented in this paper.
  Bikash Sarkar , B.C. Mohapatra , S.K. Singh , Dukhia Majhi , N. Sarangi and G.N. Tiwari
  An experiment was conducted to examine the energy use pattern in open and greenhouse fish ponds. The energy consumption was around 584.99 and 1027.22 MJ/50 m2 for open and greenhouse pond, respectively. The energy input-output, specific energy and energy productivity were found to be 0.070, 71.55 MJ kg-1 and 0.014 kg MJ-1 for open pond and 0.079, 63.60 MJ kg-1 and 0.015 kg MJ-1 for greenhouse pond, respectively. The energy ratio was higher in the greenhouse due to lower inputs and the specific energy was recorded low due to the higher yield.
  Lopa Ghosh , G.N. Tiwari , Tribeni Das and Bikash Sarkar
  An analytical model is presented to study the effectiveness of a low cost arch shape greenhouse used for heating the fishpond during extreme winter. The model was solved for the climatic conditions of New Delhi (Latitude-28° 35/ N, Longitude-77° 12/ E and an altitude of 216 m above mean sea level). Parametric studies involved the effects of different greenhouse fishpond related parameters including depth of pond water, transmissivity of greenhouse cover and number of air changes in the greenhouse on water heating in the fishpond. The thermal performance of fishpond was assessed in terms of thermal load leveling. A 4.76-5.83°C rise in water temperature could be achieved as compared to open pond of the day. The maximum heat gain and loss are around 14:00 to 17:00 and 1:00 to 7:00 h of the day, respectively. From production point of view greenhouse fish pond showed better performance compared to open pond.
  Tribeni Das and G.N. Tiwari
  In this communication, a study of convective heat transfer coefficient during greenhouse fish drying for prawn (Macrobrachium lamarrei) under forced convection mode has been performed. The experiment has been performed during July 2006 for the composite climate of New Delhi. The hourly data for the rate of moisture evaporation, wind velocity, fish temperature and relative humidity inside greenhouse have been recorded for complete drying of fish under both natural and forced convection mode. These data were used for determination of the coefficients of convective heat transfer. Convective heat transfer coefficients are higher for forced convection than natural convection drying. Also the drying time required for forced convection is lesser than natural convection drying. It is mainly dependent on the rate of moisture transfer under the drying process. The curve fitting was carried out for different available model out of various observations. A quadratic curve exhibited best relation between convective heat transfer coefficient and drying time. This model gives the maximum coefficient of determination.
  Lopa Ghosh and G.N. Tiwari
  This study presents modeling of dissolved oxygen performance in a greenhouse fishpond. A short-term Disolved Oxygen (DO) fluctuation of a fishpond was developed by using various simple equations and continuous measurement of DO, temperature and solar intensity. Numerical computation has been performed for a typical winter day at the month of January, 2007. Components considered in the DO model include the production of DO by phytoplankton and consumption of oxygen by phytoplankton, fish, water column and sediment. Numerical equations were solved with Excel soft ware to predict DO in the pond. Initial slope (α) and Pmax were calculated from DO production Vs. solar radiation curve. The amount and distribution of oxygen production in the water column depend on solar intensity and penetration as well as phytoplankton concentration. A parametric study has been performed to represent the effects of pond depth, SDD, extinction coefficient, water temperature and fish yield changes on DO regimes in fish pond. Dissolved oxygen concentrations in the pond varied with both pond depth and SDD. By increasing the depth of the pond and of the SDD and maintaining phytoplankton chlorophyll-a concentration at 232 μg L-1, the overall oxygen production was increased. The low DO values in the shallow pond (0.5 m) with a high SDD (0.5 m) when compared to other ponds with SDD equal to their pond depths, was the result of low overall oxygen production relative to the demand by sediment and fish which were same for all depths of pond. Predicted and experimental DO concentrations exhibited fair agreement with correlation coefficient of R = 0.99 and root mean square percent deviation e = 3.73%. Such correlation between predicted and experimental data indicates that the assumption inherent in the computer model of the processes is valid for the DO production and consumption in the pond.
  Anil Kumar and G.N. Tiwari
  G.N. Tiwari and Bikash Sarkar
  A greenhouse experiment was carried out to investigate the energy output-input relation and their specific growth yield relationship for production of rohu fish (Labeo rohita). The results revealed that the yield was found 5.01 and 10.38 kg in open and greenhouse pond, respectively. The operational energy and energy source requirement were found to be 505.26 and 325.27 MJ/18 m3 in case of open and 542.22 and 580.23 MJ/18 m3 for greenhouse fish production. The energy ratio, specific energy and energy productivity were calculated 0.078, 12.88 MJ/18 m3 and 0.0154 MJ/18 m3 for open condition, where as 0.090, 11.09 and 0.0178 MJ/18 m3 for greenhouse, respectively. Fish yield increased as a function of energy inputs. Mathematical relations were fitted to the growth yield and energy input. The best data fitting was obtained between specific growth yield and energy input in open and greenhouse are Nelder`s curve (R2 = 82.66%) and Gupta and Nigam (R2 = 66.16%), where as between specific growth yield and feed energy was found to be best suited in the form of Quadratic for both the condition, as it gave the maximum coefficient of determination.
  V.K. Dwivedi and G.N. Tiwari
  In this study, the life cycle cost analysis of single and double slope passive solar still for composite climate of New Delhi has been carried out. The analysis is based on annual performance of energy and exergy of both solar stills. It has been observed that water produced by proposed double slope solar still is cheaper (Rs. 0.28 L-1) than proposed single slope solar still (Rs. 0.33 L-1; Rs. stands for Rupees, an Indian currency). The Energy Pay Back Time (EPBT) for proposed single and double slope solar stills are 1.64 and 1.60 years, respectively.
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