MIL-HDBK-1003/19

This result indicates that 14 percent of the solar energy absorbed in

the building during the harshest winter month (February for Norfolk at a

base temperature of 60deg.F) must be ventilated to avoid driving the room

air temperature more than 10deg.F above the thermostat setpoint.

5.3.10 Average maximum temperature. The average daily maximum

temperature during the reference month is determined by the equations

provided on Worksheet 8 which is reproduced in the examples.

The first equation gives the solar energy delivered to the living space

during February which is the reference month. All quantities in the

equation are available from previous worksheets except the monthly degree

days (DD) which is obtained from Appendix B. Next, the excess solar

energy is determined by taking the product of QD and the compliment of the

utilization efficiency. The excess solar energy is 1.69 MMBtu. The

average temperature in the living space, assuming the excess solar energy

_

is ventilated, is T which is found to have a value of 70.7 for this

example. When a night time setback is employed, the effective thermostat

_

setpoint (Te) is used for Tset in the equation for T. Finally, the

temperature increment without ventilation ([W-DELTA]TI) is computed to

_

be 1.3deg.F which is added to T to obtain an average daily maximum

temperature of 72deg.F, which is well within the comfort range.

5.3.11 Incremental cooling load. The incremental cooling load is

determined by filling out Worksheets 9 and 10 which are reproduced in the

examples. First read the TOTAL ANNUAL TRANSMITTED RADIATION from the row

marked DUE SOUTH AND VERTICAL in the weather table for Norfolk. Since the

system is double glazed, select the quantity:

(QTA2)o = 232,584 Btu/ft2

.

Then read and record C1 through C5 from the row marked AZIMUTH AND TILT

COEF. and record them on the worksheet. Finally, using equation 5.15 as

indicated, calculate the transmitted solar radiation corrected for azimuth

and tilt. The result is:

QTA2 = 231,210 Btu/ft2

.

The last equation on the worksheet yields:

QD = 177.4 x 106 Btu

,

for the delivered solar energy.

We begin filling out Worksheet 10 by selecting a maximum temperature of

80deg.F. In this case Tset is 70deg.F which is the same value used for

the auxiliary heat consumption analysis. Therefore, we may use the annual

heat to load ratio and the auxiliary heat requirement that were previously

recorded on Worksheet 6. Enter these numbers and calculate the annual solar

heating fraction using the indicated equation. Then calculate the actual

indoor temperature from the equation provided on Worksheet 10. The result

is:

Tact = 75.8deg.F

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