ρa
|
Air density, kg m−3
|
1.225 |
Qtw
|
Total flow of wall fans, m3 s−1
|
0 |
ca
|
Specific heat of air, J kg−1 K−1
|
1005.4 |
Qtp
|
Total flow of pit fans, m3 s−1
|
0.823 (0.412,1.65) |
Tr, |
Room temperature, K |
Computed in Eq. 1; initial value = 293 |
Qapc
|
Flow through contaminant control equipment (APC), m3 s−1
|
0, 0.236, 0.472, 0.944, 1.888 |
Tp
|
Pit temperature, K |
Computed in Eq. 1; initial value = 293 |
rapc
|
Fraction of air in APC that is recirculated |
0, 0.25, 0.5, 0.75, 1.0 |
Tf
|
Floor temperature, K |
273.9 |
Qae
|
Airflow exchange ratio between pit and room air, m3 s−1
|
0.1×Qtp
|
Tg
|
Ground temperature, K |
273.9 |
qgen |
Heat generation rate, W |
qheater + qlamps + qswine
|
To
|
Outside temperature, K |
Eq. 3 |
qheater |
Heat generation rate from 2 heaters, W |
35166, when on |
Tbias
|
Temperature bias to set median winter Temperature to test site in equation 3, K |
278 |
qlamp |
Heat generation rate from heating lamps (20 125-W lamps), W |
2500 |
Arw, |
Surface area of room-walls (including ceiling), m2
|
238.4 |
qswine |
Heat generation rate from swine, W (Eq. 4) |
11,254 (sow = 181.4 kg, piglet = 5.85 kg) |
Arf
|
Surface area of floor, m2
|
54.6 |
Pelect
|
Electricity cost, $ / kWh |
0.0536 |
Apw
|
Surface area of pit-walls, m2
|
146.464 |
Pgas
|
Natural gas cost, $ / m3
|
0.19 |
Urw
|
Heat transfer coefficient, room to wall, W m−2 K−1
|
0.286 |
Qheater |
Natural gas consumption of 1 heater, m3 s−1
|
0.000472 |
Urf
|
Heat transfer coefficient, room to floor, W m−2 K−1
|
0.568 |
qfan |
Pit fan power consumption, W |
345 |
Upw
|
Heat transfer coefficient, pit to wall, W m−2 K−1
|
0.568 |
qapc |
APC power consumption, W |
Varies by APC; See Table 4
|
|
|
|
Sheater
|
Switch function of heater, as determined by room temperature, per second |
0 = off; 1 = on |