Card 6u - DIURNAL4 Solar Heating Modeling Request

This optional card defines the solar flux calculation options for the diurnal solar heating modeling request.


Parameter	Value	Description
`DIURNAL4`	DIURNAL4 (or 64)	Mnemonic
`ID`	Integer	Request ID number
`FLUXOPT`	NOATT	No atmospheric attenuation
	ATT	Atmospheric attenuation occurs and is evaluated with the atmospheric extinction coefficient method
	TABLE	`VAL1` is a solar flux table number
	TURB	Atmospheric attenuation occurs and is evaluated with the altitude and turbidity method
`VAL1`	Real	Apparent solar radiation value if `FLUXOPT=ATT`, and the solar flux value for `FLUXOPT=TURB`
`VAL1`	Integer	Solar flux table number if `FLUXOPT = TABLE`
`VAL2`	Real value	Atmospheric extinction coefficient if `FLUXOPT=ATT` and turbidity factor for `FLUXOPT=TURB`. Otherwise, it is unused
`VAL3`	Real value	Clearness factor if `FLUXOPT=ATT` and clearness index if `FLUXOPT=ATT` or `FLUXOPT=TURB`. Otherwise, it is unused
`VAL4`	Real value	Diffuse sky radiation factor if `FLUXOPT=ATT`. Otherwise, it is unused
`VAL5`	Real value	Albedo value if `FLUXOPT=ATT` or `FLUXOPT=TURB`. Otherwise, it is unused
`VAL6`	FACTOR	Controls the overcast conditions method. `VAL3` is a clearness factor
	INDEX	Controls the overcast conditions method. `VAL3` is a clearness index
	0 or blank	If `FLUXOPT=NOATT` or `FLUXOPT=TABLE`

FLUXOPT

FLUXOPT specifies the type of solar flux calculation option.

VAL1

VAL1 can be:

The value of the solar flux outside the atmosphere if FLUXOPT=NOATT or FLUXOPT=TURB.
The table number of the time-dependent solar flux value defined in Card 9 TABTYPE Card for FLUXOPT=TABLE.
The “apparent solar flux” defined in the ASHRAE Fundamentals Handbook, Edition 1997, pp. 29.17 for FLUXOPT=ATT.

If a table-dependent solar flux is defined, the dependent parameter in the TABTYPE Card must be QNODE, and the independent parameter must be TIME.

VAL2

VAL2 is the atmospheric extinction coefficient value if FLUXOPT = ATT. The direct normal irradiation at the Earth’s surface of a plate normal to the sun is defined to be:

where β is the angle between the horizon and the sun vector is found in the table of ASHRAE Handbook, HVAC Applications 1995, SI edition, p. 30.2.

VAL2 is the Linke turbidity factor if FLUXOPT = TURB. The direct normal irradiation, at the Earth’s surface of a plate normal to the sun, is defined as:

where:

m is the relative optical air mass.
δ_R(m) is the Rayleigh optical thickness at air mass m is found in Suri, Marcel, and Jaroslav Hofierk, Transactions in GIS 8.2, 2004, p. 175-190.

VAL3

VAL3 is the clearness factor value if FLUXOPT = FACTOR, otherwise it is blank or 0.

The clearness factor is the ratio between the actual clear day direction radiation intensity at a specific location, and the intensity calculated for the standard atmosphere at the same location and date. The reference for clearness factor is found in ASHRAE Handbook, 1995, HVAC Applications, pp. 30.5. Clearness values > 1 indicate a very dry and clear sky, for example, a sky at high altitudes. Conversely, clearness values < 1 indicate very hazy and humid conditions.

VAL3 is the clearness index value if FLUXOPT = INDEX. The clearness index is the ratio of radiation on a horizontal surface to the extraterrestrial radiation. The clearness index is employed to estimate solar radiation under overcast conditions using the Solar Energy Research Institute method found in Maxwell, E.L., 1987, Solar Energy Research Institute, United States.

VAL4

VAL4 is the diffuse sky radiation factor if FLUXOPT = ATT, otherwise it should be blank or 0.

This is the ratio of the diffuse solar flux originating from the sky incident upon a horizontal plate to the direct attenuated solar flux incident upon a plate normal to the sun vector. (cf table 1 ASHRAE Handbook, 1995, HVAC Applications, p30.2)

VAL5

VAL5 is the albedo value if FLUXOPT = ATT or FLUXOPT = TURB, otherwise, it is blank or 0.

Albedo is the fraction of the solar radiation reflected from the nearby ground.

VAL6

VAL6 specifies the type of clearness values that are defined for VAL3.

Code example


DIURNAL4 3 ATT 1.188116E+03  1.559929E-01 1.000000E+00  7.115684E-02  3.060000E-01 FACTOR
DIURNAL4 3 NOATT 1100.0
DIURNAL4 3 TABLE 10