Análise experimental dos limites operacionais de um termossifão para aplicações em coletores solares

Abstract

The thermosyphons, also known as heat pipes assisted by gravity action, are the simplest kind of heat pipes which have various applications in industrial heat recovery. These devices are also a suitable alternative to solar collectors due to their relative simplicity of construction and pumping the working fluid accomplished by gravity due to their inclination of the collector surface. The operation of the thermosyphon has limitations which are: viscous limit, boiling limit, sonic limit and drag limit. A mathematical model is here developed to calculate these operational limits, taking into account the influence of the diameter, evaporator length, condenser length and working fluid selection. After that, a termosyphon is built and experimental tests were runned out so that their results are compared with the results obtained with the mathematical model. The thermosyphon was constructed with a copper tube and its working fluid was deionized water. Experimental tests were performed in order to evaluate the thermal behavior of the thermosyphon in relation to operational limits. The thermosyphon operated satisfactorily under heat loads ranging from 5 to 80 W. The theoretical results when compared with experimental results were in good agreement showing that the mathematical model can be used as a tool for developing thermosyphon design that can be applied to solar collectors.