V.H. Gómez

Evaluation of the Thermal Performance of a Solar Water Heating Thermosyphon Versus a Two-Phase Closed Thermosyphon Using Different Working Fluids

A water heating closed two-phase thermosyphon solar system was designed and built. The system consists of a flat plate solar collector coupled to a thermotank by a continuous copper tubing in which the working fluid circulates. The working fluid evaporates in the collector and condensates in the thermotank transferring its latent heat to the water through a coil heat exchanger. The tested fluids are acetone and R134a. The thermal performance of the proposed systems is compared with a conventional solar water thermosyphon under the same operating conditions. Advantages of a two-phase system include the elimination of freezing, fouling, scaling and corrosion. Geometry and construction materials are the same except for the closed circuit presented in the two-phase system. Data were collected from temperature and pressure sensors throughout the two systems. Early results suggest that R134a may provide a better performance than acetone for this kind of systems.

Thermal Model of a Gas Fired Generator for an Absorption GAX Cooling System

A numerical model of a direct fired generator is presented. The objective is to provide a baseline for designing the prototype of a gas fired generator, aimed to drive a GAX absorption cooling system. The model was carried out using Fortran 90. The gas fired generator will be part of the hybrid 10.5 kW GAX cooling system, which is being designed to operate with solar energy and direct fired by LPG combustion. The prototype is designed in two sections. In the first section, the “U” form combustion chamber is flooded with ammonia-water solution, the heat radiation from the flame and the hot combustion gases are absorbed by the tube walls and transferred to the solution. In the second section (the convection zone), the combustion gases are used to increase the concentration of the ammonia refrigerant. Thermal design results in the radiation, boiling and convection zones are presented and discussed, while the manufacturing strategies are being analyzed to produce a compact and efficient prototype.Copyright