Study of solar absorption cooling systems
Solar energy is a vast and inexhaustible source of energy. However, solar radiation approaching the earth's surface is variable. Efficient use of this radiation is complicated by this variable nature. The work described in this thesis deals mainly with the use of solar energy for absorption cooling systems. Basic cooling and heat pump systems are described in brief. A literature survey of the absorption cooling systems is given and the scope for research work in this area is discussed. The effect of variations of the parameters in the closed cycle and open cycle absorption cooling systems has been analysed in order to optimise the performance of the systems. Experimental verification of the above analysis for a closed cycle system using water-lithium bromide as a working pair is presented along with some typical characteristic performance data for certain conditions. These conditions are lower generator temperatures, which lead to more efficient solar energy collection systems and higher absorber/condenser temperatures providing the feasibility of air cooling. Computer programs for the above analyses are given. A closed cycle absorption system using water-lithium bromide has also been theoretically analysed for simultaneous cooling and heating. A computer program developed for the above analysis is presented. A modification in the practical cycle to achieve high temperature lifts for simultaneous heating and cooling appears to be very attractive. An expression for coefficient of performance of an ideal absorption cycle system, when condensing temperature is not equal to absorber temperature, has been derived. Experimental verification of the above concept in a single stage cycle is also reported. An experimental unit to generate design data for a solar generator, of an open cycle absorption cooling system has been designed and installed. This unit is described in detail. Solar simulation has been done in two ways. The first way is by a radiation source consisting of CSI lamps and the second way is by providing an equivalent electrical heat flux. The relationship between the two is discussed. Based on the experimental data obtained, correlations in conventional forms for heat and mass transfer operations in the generator are presented. A mathematical model of the solar generator incorporating the above correlations is discussed. A computer program for the prediction of the performance of the generator is presented. The experimental results are compared with the predicted results and optimum conditions for various situations are discussed.