Correction of collector efficiency depending on fluid type, flow rate and collector tiltIEA-SHC TECH SHEET 45.A.1
February 2015 - PDF 0.82MB
In its basic form, a solar thermal collector is designed to intercept solar radiation, absorb that radiation to convert it into heat energy, and then deliver that heat to a heat transfer fluid. Therefore, the performance of a solar thermal collector is influenced by all variables that affect either the optical or the thermal properties of the collector. For example, the incidence angle of solar radiation onto the solar collector can affect the optical performance of the collector. While typically not a strong factor for solar thermal collectors, the changing spectral quality of sunlight with changing atmospheric conditions can influence the fraction of the incoming solar radiation that gets transmitted and absorbed by the collector. Tilt angle, especially for glazed flat plate collectors, affects internal and external convective heat transfer coefficients, and thus influences collector thermal performance. Heat transfer fluid flow rate and fluid thermal properties influence the heat transfer coefficient inside the fluid passages of the collector, and thus influence the collector efficiency.