HVAC

Question 1

Heat Transfer - Uniform Material

Answer 1

Q = (k A DT ) / t

Question 2

Heat Transfer - Pipe

Answer 2

Q = (k 2pi L DT) / ln (r2 / r1)

Question 3

Heat Transfer Coefficient

Answer 3

U = (U1 A1 + U2 A2) / A
U = 1 / R = k / t
R = (1 / h) + R1 + R2
R1 = L / k

Question 4

Heat Transfer - k

Answer 4

k - conductivity, Btu in/ hr ft2 F

Question 5

Molar Mass Air & Water

Answer 5

Mair = 29 g/mol   
Mw = 18 g/mol

Question 6

Specific Heat Air & Water

Answer 6

Cpair = .24 BTU/lb F
Cpw = 1 BTU/lb F

Question 7

Density Air & Water

Answer 7

Pair = .075 lb/FT3
Pw = 62.4 lb/FT3

Question 8

Heat Transfer - Water

Answer 8

Q (BTU/h) = 500 Q DT

Q = m Cp DT

Question 9

Heat Transfer - Sensible

Answer 9

Q (BTU/h) = 1.1 Q DT

Question 10

Heat Transfer - Latent

Answer 10

Q (BTU/h) = 4,840 Q DW

Question 11

Heat Transfer - Total

Answer 11

Q (BTU/h) = 4.5 Q DH

Question 12

Mixing Airstreams

Answer 12

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

Question 13

What causes condensation?

Answer 13

Surface T is below DP T

Question 14

Low P refrigerants _____ at _____ T

Answer 14

boil low

Question 15

High P refrigerants _____ at _____ T

Answer 15

condense high

Question 16

Evaporation

Answer 16

Low P (constant), High T (constant - all heat changes phase), Gas

Question 17

Compressor

Answer 17

High P (inc), High T, Gas (constant entropy)

Question 18

Condenser

Answer 18

High P, Low T, Liquid

Question 19

Expansion Valve

Answer 19

Low P, Low T, Gas/Liquid

Question 20

BHP vs HP

Answer 20

HP = BHP / Eff(m)

Question 21

Enthalpy of mixtures

Answer 21

h(fg) = h(f) - h(g) 
h(mix) = h(f) + X h(fg)

Question 22

Isentropic

Answer 22

constant entropy (s)

Question 23

Adiabatic

Answer 23

no heat transfer (q=0)

Question 24

q (heat output for motor)

Answer 24

q (btu/h) = HP * 2545 * Eff(m)

Question 25

Cooling Tower - Range

Answer 25

DT across cond unit | Twin - Twout

Question 26

Cooling Tower - Approach

Answer 26

DT leaving and entering | Twout - WBTairin

Question 27

Cooling Tower - Eff

Answer 27

Eff = R / (R+A)

Question 28

Partial Pressure

Answer 28

P = Psat @ T * %RH

Question 29

PSI -> FT head

Answer 29

PSI * 2.31 = FT

Question 30

Rectangle Equivalent Diameter

Answer 30

Rectangle De = 1.3 (a b)^.625 / (a + b)^.25

Question 31

ASHRAE 15

Answer 31

Safety for Refrigeration Systems

Question 32

ASHRAE 34

Answer 32

Classification of Regrigerants

Question 33

ASHRAE 55

Answer 33

Thermal EV Conditioning for Human Occupancy

Question 34

ASHRAE 62.1

Answer 34

Ventilation for IA Quality

Question 35

ASHRAE 62.2

Answer 35

Ventilation for IA Quality - Residential

Question 36

ASHRAE 90.1

Answer 36

Energy Codes

Question 37

Natural Gas "name"

Answer 37

Methane

Question 38

HZ & RPM

Answer 38

1 HZ = 60 RPM