M.R ROOMINA - Graduate Research Assistants Department of Mechanical Engineering University of Tehran Tehran, IRAN
R GHAFOURI-AZAR - Graduate Research Assistants Department of Mechanical Engineering University of Tehran Tehran, IRAN
MEHDI ASHJAEE - , Assistant Professor Department of Mechanical Engineering University of Tehran Tehran, IRAN

Two computational methods for calculating hourly, daily and monthly average values of direct, diffuse and total solar radiation on horizontal collectors have been presented in this paper for location with different latitude, altitude and atmospheric conditions in IRAN. Comparison of calculated monthly average total solar radiation using the two models Tehran and Isfahan with measured data from Iranian Meteorological Organization (IMO) has indicated a good agreement between them. Then these developed methods were extended to another location (city of Bandar-Abbas) where measured data are not available. But the work of Daneshyar [۲] predicts its monthly total radiation. The maximum discrepancy of ۷% between the developed models and the work of Daneshyar [۲] was observed.