An experimental study of heat driven absorption cooling systems
The great need for cooling combined with Mexico's large availability of low enthalpy energy from non conventional energy resources such as geothermal energy, solar heat and waste heat from industrial processes, makes it very attractive to utilize these resources for cooling using heat driven absorption systems. The main purpose of the work described in this thesis is to obtain experimental and theoretical data on heat driven absorption cooling systems for the design of large scale systems. Thermodynamic design data have been theoretically derived for heat driven absorption heat pumps and heat transformers using the working pairs ammonia-water and ammonia-lithium nitrate for cooling, heating and simultaneous heating and cooling. The interaction between the operating parameters has been illustrated graphically. A computer model of the steady state thermodynamics of a heat driven ammonia-water system and an ammonia-lithium nitrate system has been developed. A comparison of both systems is made by assessing the effect of operating temperatures and heat exchanger effectiveness on the coefficient of performance for cooling and the heat transfer rates within the system. An experimental study on the performance of the absorber of an absorption cooling system operating on water-lithium bromide has been made. The experimental study of the adiabatic absorber was concerned with the determination of the effect of the evaporator heat load and the absorber reflux on the performance of the absorber. An experimental study of the operating characteristics of an experimental. absorption cooler using water-lithium bromide-lithium iodide and waterlithium bromide-zinc bromide as ternary systems has been made in order to achieve higher coefficients of performance and a lower risk of crystallization. Experimental studies with a small heat driven absorption cooling system operating on ammonia-water using a falling film generator were made. Low generator temperatures were achieved which will'enable the use of non focussing solar collectors as a heat source for the system. An ammonia-water absorption cooler operating on low enthalpy geothermal energy was installed and operated at two geothermal fields. The system was used to cool a small cold storage facility below freezing temperatures. The experimental and theoretical results on absorption cooling systems will provide a basis for the design of heat pump systems for industrial and commercial applications.