MIL-HDBK-1003/19
where TLCs is the steady state total load coefficient. If on the other
hand, the effective aperture conductance (G), expressed in Btu/deg.F-day
ft2, is selected, then:
TLCe = NCL + G [multiplied by] Ac
(Equation 4.12)
where TLCe is the effective total load coefficient. The effective
conductance (G) is a system correlation parameter, as will be expanded on in
5.1.1, and includes the effect of solar aperture dynamics. The appropriate
choice of TLC parameters will be specified for each application in these
procedures.
4.4.1.9 Thermostat setpoint. The thermostat setpoint (Tset) is the
temperature setting of the thermostat that controls the auxiliary heating
system.
4.4.1.10 Diurnal heat capacity. The diurnal heat capacity (DHC) is the
amount of heat that can be stored in the thermal mass of a building, per
unit room air temperature swing, during the first half of a 24-hour cycle
and returned to the space during the second half of the cycle. The
performance of passive solar buildings is enhanced when the DHC is elevated.
Procedures for calculating this important parameter will be presented in
5.1. The DHC has units of Btu/deg.F.
4.4.1.11 Effective heat capacity. The effective heat capacity (EHC) is
a correlating parameter that relates the thermal performance of otherwise
identical direct gain buildings that have arbitrary thermal storage media
arranged in various geometric configurations. As such, the EHC, which has
units of Btu/deg.F of solar aperture, provides a measure of the amount of
heat that may be stored in the thermal mass of a building during one day and
returned to the room air on the same day or on succeeding days at times and
rates that lead to improvements in building performance. Improvements in
solar thermal performance occur when stored solar energy is delivered to the
room air in phase with the building thermal load, thereby reducing auxiliary
heating requirements. A nomograph for the EHC will be presented in 5.1.
4.4.1.12 Effective thermostat setpoint. The analysis methods presented
in this document require the use of a constant thermostat setpoint. Because
control strategies involving nightime setbacks are advantageous due to the
resultant reduction in auxiliary heat consumption, a procedure has been
developed for relating building and control parameters to a constant
effective thermostat setpoint (Te); this procedure is described in 5.1.
The temperature Te should be used in place of Tset for the analysis of
any building that employs a control strategy.
4.4.1.13 Base temperature. The base temperature (Tb) is the
thermostat setpoint (or the effective setpoint) adjusted in a manner that
accounts for internal-source heating by people, lights, appliances, office
equipment, or any other device not primarily intended as an auxiliary heat
source. The base temperature is given by:
Tb = Tset - Qint/TLCs,
(Equation 4.13)
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