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Mini Project # 1: Solar Radiation MECH 473 Group #8 Procedure Dry Bulb Temperature To determine the design day dry bulb temperatures, the formula is used: DBoa,h=DBoa,design-zhDRThe input outdoor air design dry bulb temperature (DBoa, design) is found in the ASHRAE design conditions table in the Mean Coincident Dry Bulb Temperature section for 1% in July. The values for zh are found in table 4 of Handout 2 in the generating design day data section. The daily range (DR) is found in the ASHRAE design condition sheet in the Monthly Mean Daily Temperature Range section for July. The output of this formula is the hourly outdoor air dry bulb temperature (DBoa.h). Solar Angles To determine the solar altitude (β), the following formula is used: sinβ=cosLcosδcosH+sinLsinδ. The latitude (L) is given in the mini project handout. The solar declination angle (δ) is determined based on the time of year (n): δ=23.45sin{360284+n365}, which is given in the project handout on July 21st. The hour angle (H) varies hourly based on the local solar time (LST): H=15(LST-12). Once the solar altitude is known the solar azimuth angle (ϕ) can be determined from: cosφ=sinβsinL-sinδcosβcosLIt must be noted here that when determining ϕ, the arccosine of cosϕ is taken. The result of this will give ±ϕ. The angle is measured from South and is given as 90° at West, and -90° at East. Since the sun rises in the East, ϕ will be negative in the morning, zero at noon and positive in the afternoon. The surface-solar azimuth (γ) is found from the formula: γ=φ-ψThe azimuth angle (ψ) is the angle from south normal to the calculated surface in the horizontal plane.
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