No abstract

A twodimensional axisymmetric model, which is computationally inexpensive, has been proposed to predict the property changes that occur in a seasonal rock‐pit energy storage (RPES) system. The geometry of the rock‐pit has been simplified into a shape that can be extended for any seasonal storage system with a three‐dimensional conical geometry. The computational domain has been solved using both linear thermal equilibrium (LTE) and linear thermal non‐equilibrium (LTNE) models, and the former has been found to be computationally quick and accurate. The model has predicted a 95% energy saving at the highest flow conditions required in the mine. Further analysis has suggested that the increase in storage capacity by decreasing the porosity of rocks in the rock‐pit is insignificant compared to the corresponding increase in fan power. Furthermore, the investigation done on natural rocks has indicated an increased ability to store heat in the rock‐pit when rocks with higher thermal mass have been used. The use of RPES has shown a significant potential to reduce the carbon footprint. Finally, an economic analysis done on the system has shown a return on investment of just under 12 years.

In this study, Cotton seed oil ethyl ester was produced by transesterification process. The performance of diesel engine was experimentally investigated by using cotton seed oil ethyl ester as fuel. For the study cotton seed oil ethyl ester was mixed with diesel fuel and B20 blend was prepared. Also Diethyl Carbonate was added as an additive in 4, 8 and 10% proportion. Fuels were tested on a single cylinder, four-stroke, direct injection, water cooled diesel engine. The effects of cotton seed oil ethyl ester diesel blend on engine performance were examined at constant speed and varying loading conditions. The effect of B20 and its blends with diethyl carbonate on engine power, brake specific fuel consumption, brake thermal efficiency and exhaust gas temperature were clarified by the performance tests. The experimental results showed that the use of B20 with 10% diethyl carbonate increases the brake thermal efficiency, decreases fuel consumption; decreases brake specific fuel consumption and also the exhaust gas temperature. However, there were no significant differences in performance values of diesel, B20 and B20 with diethyl carbonate. The experimental results showed that the lower contents of cotton seed oil ethyl ester in the blends can partially be substituted for the diesel fuel without any modifications in diesel engines.

A low capacity twin‐bed adsorption refrigeration system has been built with R134a as a refrigerant and activated carbon as the adsorbent. Simple tube‐in‐tube heat exchangers have been fabricated and have been used as the adsorber beds. Activated carbon (granular type) has been filled in the annular space of the inner tube and outer tube. A plate heat exchanger has been used as the condenser and the temperature of cooling water has been maintained between 25°C and 30°C, also the evaporator has been custom designed as per requirements. A mathematical model has also been developed and the results obtained have been found to be comparable. While operating the system in the single‐bed mode a cooling power of 250.4 W has been obtained with a coefficient of performance (COP) of 0.38 with an average evaporator temperature of 18.4°C against a predicted value of 263.7 W with a COP of 0.41. While operating in the twin‐bed mode a cooling power of 281.3 W with a COP of 0.47 with an average evaporator temperature of 17.6°C has been obtained against a predicted value of 294.5 W with a COP of 0.52.