HVAC Flashcards
1
Q
Heat Transfer - Uniform Material
A
Q = (k A DT ) / t
2
Q
Heat Transfer - Pipe
A
Q = (k 2pi L DT) / ln (r2 / r1)
3
Q
Heat Transfer Coefficient
A
U = (U1 A1 + U2 A2) / A U = 1 / R = k / t R = (1 / h) + R1 + R2 R1 = L / k
4
Q
Heat Transfer - k
A
k - conductivity, Btu in/ hr ft2 F
5
Q
Molar Mass Air & Water
A
Mair = 29 g/mol Mw = 18 g/mol
6
Q
Specific Heat Air & Water
A
Cpair = .24 BTU/lb F Cpw = 1 BTU/lb F
7
Q
Density Air & Water
A
Pair = .075 lb/FT3 Pw = 62.4 lb/FT3
8
Q
Heat Transfer - Water
A
Q (BTU/h) = 500 Q DT
Q = m Cp DT
9
Q
Heat Transfer - Sensible
A
Q (BTU/h) = 1.1 Q DT
10
Q
Heat Transfer - Latent
A
Q (BTU/h) = 4,840 Q DW
11
Q
Heat Transfer - Total
A
Q (BTU/h) = 4.5 Q DH
12
Q
Mixing Airstreams
A
h3 = h1 Q1 + h2 Q2 / (Q1 + Q2) w3 = w1 Q1 + w2 Q2 / (Q1 + Q2) T3 = T1 Q1 + T2 Q2 / (Q1 + Q2) h3 = h1 RH1 + h2 RH2
13
Q
What causes condensation?
A
Surface T is below DP T
14
Q
Low P refrigerants _____ at _____ T
A
boil low
15
Q
High P refrigerants _____ at _____ T
A
condense high
