Determinação numérica e experimental da eficiência de um circuito de sifão térmico de aquecimento solar

Abstract

This work has as objective the numeric and experimental determination of the mass flow rate of circulation and of the efficiency heat of a thermosiphon solar circuit for heating of a refrigeration system by absorption. Two considerations have been done at the numeric determination of the mass flow rate of circulation on the circuit. At the first, the outflow was laminar because of the flows of heat by solar radiation responsible for the movement of the fluid on the circuit. At the second, the pressure resultant of the difference between the densities of the hot and the cold sides of the circuit was equilibrated by the loss of pressure by friction on the outflow of work's fluid at the circuit. At the experimental determination, the circuit has copper tubing isolated with gutters with the thickness of 2 cm. The fluid used was a synthetic thermal oil with heating capacity up to 400°C. The absorber was made by stainless steel and instaled over the flat solar collector. The experimental measurements included the values of the temperature in various positions of the circuit, of the global solar radiation on inclined plane of the collector and of the mass flow rate of circulation. An external sensor that operates with sound waves was selected for not to interfere with the pressure loss in the circuit, and consequently with the mass flow that will be measured. The results show that for radiation fluxes of 800 W/m², the mass flow reaches values around 16 g/s.