Calculating solar radiation received by tubular collectors

Tubular absorbers installed inside evacuated tubes represent an increasingly common design for low-temperature solar col lectors. Much work has been done on the subject of solar radiation received by flat-plate collectors; much less has been done for tubular collectors. In this paper we present nn algorithm to estimate irradiance impinging on tubular arrays. Key examples are provided to illustrate the difference of energy collected between par-plate and tubular collectors.