N. L. Panwar

Exergetic Analysis of a vapour compression refrigeration system with R134a, R143a, R152a, R404A, R407C, R410A, R502 and R507A.

This communication deals with the exergetic analysis of a vapour compression refrigeration system with selected refrigerants. The various parameters computed are COP and exergetic efficiency in the system. Effects of degree of condenser temperature, evaporator temperature and sub-cooling of condenser outlet, supper-heating of evaporator out let and effectiveness of vapour liquid heat exchanger are also computed and discussed. In this study, it was found that R134a has the better performance in all respect, whereas R407C refrigerant has poor performance.

Experimental investigation of energy and exergy efficiencies of domestic size parabolic dish solar cooker

This paper deals with an energy and exergy analysis of a domestic size parabolic solar cooker in actual use. The experimental time period was from 10:00 to 13:30 solar time. During the experiment, it was found that the maximum temperature of water was 368 K. The energy out of the cooker varied between 46.67 and 653.33 W, whereas its exergy output was in the range, 7.37-46.46 W. Maximum energy and exergy efficiencies of the cooker were experimentally evaluated, and it was about 46.82% and 32.97%, respectively. Over the time, both efficiencies were decreased because of the optical and thermal losses from the reflector and pot. By using properly insulated cooking pot, the considerable amount of conventional energy can be saved. Regular use of a solar cooker helps in CO2 mitigation and provides clean and safe cooking.

Design and performance evaluation of biogas stove for community cooking application

Matured biogas production technology has led to the development of a number of biogas appliances for lighting, power generation, and cooking. The most promising among them is the biogas stove, to meet the energy requirement for cooking application at domestic as well as at the community level. In this paper, an attempt has been made to design and develop a community biogas stove for baking chapatti (bread) or other food items on a hotplate for canteen or community purposes. The performance of the stove was evaluated by using a 25 m3 floating type biogas plant at Asha Dham Asharm, Udaipur, India. The gas consumption rating of the developed stove was 1 m3 (19 MJ/h) and the cooking efficiency of the stove was recorded to be about 43.96%.

Effects of thermal conductivity and geometry of materials on the temperature variation in packed bed solar air heater

The efficiency of energy collection of a flat plate type of solar air heater is low because of the large thermal losses and low heat transfer coefficient between the absorber plate and the air flowing in the duct. Packed beds have been successfully employed for the enhancement of the heat transfer coefficients in solar air heaters and such air heaters can be used for drying agricultural produce and space heating as well. This article deals with the theoretical investigation on the effects of thermal conductivity of material and geometry of a screen on the temperature variation in woven wire screen packed bed solar air heater. Theoretical results have been compared with the experimental results reported earlier by other researchers and found to match reasonably well with them. It has been found that the thermal performance depends upon a little on the thermal conductivity of screen material. Instead, it depends more on the geometry and an extinction coefficients of the matrix. A low value of extinction coefficient is desirable for maximum absorption of solar radiations and minimum thermal losses. The numerical method of analysis used here is based on finite difference approximation. The finite difference equations have been solved through a computer program in C++.

Experimental investigation of energy and exergy efficiency of masonry-type solar cooker for animal feed

The performance of a masonry animal feed solar cooker was evaluated in terms of energy and exergy. It is a low-cost cooker made of cement, bricks, glass covers and a mild steel absorber plate. The energy and exergy efficiencies of the animal feed solar cooker were experimentally evaluated. The energy output of this cooker ranges from 1.89 to 49.4 kJ, whereas the exergy output ranges from 0.11 to 2.72 kJ during the same time interval. The energy efficiency of the cooker varies between 1.12% and 29.78%, while the exergy efficiency varies between 0.07% and 1.52 % during the same period.

Thermodynamic evaluation of heat recovery through a Canopus heat exchanger for vapor compression refrigeration (VCR) system

This communication deals with the waste heat recovery from the industrial refrigeration and air-conditioning system by introducing Canopus heat exchanger. There is a considerable amount of low-grade heat available in large-capacity systems. To recover this low-grade heat, a Canopus heat exchanger is introduced between compressor and condenser components. The system feasibility is studied with various operating parameters and its effect on heat recovery factor and overall COP of the system. The parametric results obtained for different eco-friendly working fluids, such as R-134a and R-507a, have been presented. It is found that, in general, overall COP of the system is improved without affecting the actual performance of the system. The potential of low-grade heat availability is increased with increasing cooling capacity.

The emission characteristics of a compression ignition engine operating on castor oil methyl ester

Diesel vehicles are a major form of transportation, especially in developing countries. Recent concerns over the environment, increasing fuel prices and the scarcity of its supply have promoted interest in the development of alternative sources of petroleum fuels. In this investigation, castor oil methyl ester was prepared by transesterification using potassium hydroxide (KOH) as a catalyst and tested in a four-stroke, single-cylinder compression ignition engine. The test was carried out at a constant speed of 1500 rpm at different loads. The results show that with an increasing biodiesel percentage, the carbon monoxide (CO) emission level decreases. The reduction of the CO in B05, B10 and B20 averaged 13.75%, 25.02% and 28.79%, respectively, compared to diesel (B0). The emission results of the comparative test indicated that CO, oxygen (O2) and smoke density emissions are found to be lower when the engine is fuelled with B05, B10 and B20 as compared to B0, while carbon dioxide (CO2) and nitrogen oxide (NOx) with B05, B10 and B20 are found to increase marginally.

Thermal modeling, energy and exergy analysis of animal feed solar cooker

This study deals with thermal modeling and experimental validation of animal feed solar cooker. The experiment was conducted for 9 months and found that a theoretical temperature is 2 to 3 °C higher than experimentally recorded. The value of correlation (r) coefficient for all months was 0.999, indicating that the developed model is capable of predicting the water temperature close to experimental values. Energy and exergy assessment of the cooker was also carried out. The experimental energy and exergy efficiency varied in the range of 23.19% to 28.25% and 1. 79% to 2.47%, respectively. The corresponding theoretical efficiency varies in the range of 24.22% to 28.33% and 1.97% to 2.88%, respectively.

Energetic and exergetic analysis of three different solar cookers

This article deals with the energetic and exergetic analyses, which provides an alternative means of evaluating and comparing the performance of solar cookers. In this experimental setup, three different types of solar cookers have been studied during the typical day from November to January under Indian climatic conditions. The experimental time period was from 09:00 to 14:00 solar time. It was found that the animal feed cooker (AFC), hot box cooker (HBC), and parabolic dish type cooker (PDC) showed maximum energy and exergy efficiencies during the month of November compared to December and January. The energy efficiency of these cookers in November was about 36.74%, 60.94% and 14.45%, respectively, whereas exergy efficiency was 3.62%, 8.71%, 1.41%, respectively. The average energy output of AFC, HBC, and PDC during November was 247.80, 327.60, and 260.40 kJ/day, respectively, whereas the exergy output was 19.02, 33.32, and 21.34 kJ/day, respectively.

Performance evaluation of exhaust air recirculation system of mixed mode solar dryer for drying of onion flakes

This paper deals with the performance of mixed mode type solar dryer for drying onion flakes. During the experiments, no load and full load test were conducted to find out the effectiveness to the system with or without recirculation of exhaust air. The drying and thermal efficiencies and heat utilisation factors were recorded as 21%, 74% and 31% respectively, more compared to recirculation of exhaust air test. The quality of dried onion flakes without recirculation of exhaust air test was superior. The recirculation of exhaust air was founded feasible only with use of desiccant material.