Estudio experimental del rendimiento térmico de un colector solar de tubos evacuados para calentar aire de secado

A solar collector with evacuated tubes was developed to heat air from room temperature until it has the capacity to be used in drying processes. The instantaneous and global thermal efficiency of the equipment was studied, as well as the behavior of the outlet temperature at different air flows. Measurements of inlet and outlet air temperatures, irradiance were taken, and mass flow were determined. The amount of heat absorbed by the air was calculated and, in relation to the irradiance, instantaneous efficiency was obtained to later determine the overall efficiency. The device consists of a polypropylene tube where 5 evacuated tubes were placed. Air was flowed into each of them with an arrangement of a stainless-steel conduit with thin-walled tubing. For various air flows, thermal behavior curves were obtained, where increases in air temperature between 30°C and 50°C were observed, reaching outlet temperatures of up to 90°C. Efficiencies were calculated from 40% to 60%, for high and low operating temperatures, respectively. The increase in temperature resulted in a linear trend, facilitating the design of instrumented dryers and their control.