Vሶ E
C
C
B
C
D
E
MIXING OF TWO AIR STREAMS:
𝑚ሶ 𝑅′ ℎ𝑅′
A
hO
𝑚ሶ 𝑆
𝑚ሶ 𝑂
𝑉
𝜈
(kg/s)
hmix
ℎ𝑚𝑖𝑥
ℎ𝑅′ +
ℎ𝑚𝑖𝑥 =
C
[and 𝑉 = 𝑚𝜈
ሶ ]
COOLING MOIST AIR:
hR’
𝑚ሶ 𝑆
W
@ ℎ𝑖𝑛
& 𝑊𝑖𝑛
IN
OUT
(Liquid H2O
condensate at
Tout ∴ hWout = hf)
Tdb
𝑚ሶ 𝑂
+1
𝑚ሶ 𝑅′
𝑚ሶ 𝑊
𝑞ሶ 𝑐𝑜𝑜𝑙𝑖𝑛𝑔 = 𝑚ሶ 𝑠
hS hin
𝑚ሶ 𝑆
𝑞ሶ
O
𝑚ሶ 𝑂
ℎ
𝑚ሶ 𝑅′ 𝑂
hout
@ ℎ𝑜𝑢𝑡
& 𝑊𝑜𝑢𝑡
W
IN
S
OUT
= Moisture
Win
Wout
Tdb
𝑞ሶ 𝐿 = 𝑚ሶ 𝑠 𝑊𝑖𝑛 − 𝑊𝑜𝑢𝑡 ℎ𝑊𝑜𝑢𝑡
𝑞ሶ 𝑆 = 𝑚ሶ 𝑠 ℎ𝑠 − ℎ𝑜𝑢𝑡
𝑊𝑖𝑛 − 𝑊𝑜𝑢𝑡
ℎ
1000 𝑔/𝑘𝑔 𝑊𝑜𝑢𝑡
ℎ𝑖𝑛 − ℎ𝑜𝑢𝑡 −
HEATING:
𝑞ሶ
𝑚ሶ 𝑆
@ ℎ𝑖𝑛 & 𝑊𝑖𝑛
hin
𝑚ሶ 𝑆
@ ℎ𝑜𝑢𝑡 & 𝑊𝑜𝑢𝑡
IN
D
𝑉ሶ = volume flowrate (L/s)
𝑉= volume flowrate (m3/s)
𝑞ሶ = energy flowrate (W) or (J/s)
𝑚ሶ = mass flowrate (kg/s)
ν = specific volume (m3/kg)
ℎ = enthalpy (kJ/kg)
B
R’
ℎ𝑂
Heat losses
& gains (W)
MIXING
COOLING
HEATING
HUMIDIFICATION
FIND THE SUPPLY AIR CONDITION
Mass flowrate: 𝑚ሶ =
qሶ gains
Vሶ S
H
C
qሶ losses
The
Space
Vሶ R′
Vሶ O
A
Vሶ E′
Vሶ R
hout
W
IN
OUT
𝑚ሶ 𝑆
Tdb
hW
[kJ/g-H2O]
𝑚ሶ 𝑆
E
W
Wout
OUT
IN
OUT
IN
Tdb
𝑚ሶ 𝑊 @ hW
(Water or steam
injected into air stream)
To find the state of OUT
Win
= Wout
OUT
HUMIDIFICATION: (Change in temp. and moisture)
𝑚ሶ 𝑊 = 𝑚ሶ 𝑠 𝑊𝑖𝑛 − 𝑊𝑜𝑢𝑡
Win
𝑞ሶ ℎ𝑒𝑎𝑡𝑖𝑛𝑔 = 𝑚ሶ 𝑠 ℎ𝑜𝑢𝑡 − ℎ𝑖𝑛
FIND THE SUPPLY AIR CONDITION:
𝑞ሶ 𝑠 = SENSIBLE HEAT ADDED OR LOST
SHF = SENSIBLE HEAT FACTOR =
i. Plot point R on the Pchart
ii. Determine σ 𝑞ሶ 𝑠 & σ 𝑞ሶ 𝐿 for
the space
iii. Draw the SHF line on the
inner axis of the protractor
𝑞ሶ 𝐿 = LATENT HEAT ADDED OR LOST
𝑞ሶ 𝑠
𝑞ሶ 𝑠 +𝑞ሶ 𝐿
ii. Look up hW on the steam tables
iii. Draw hW on P-chart protractor
(hw = Δh/ΔW ∴ divide by 1000)
iv. Draw a parallel line through IN
- Liquid H2O: hW = hf (Saturated
- H2O vapour: hW = hg Tables)
v. Locate point OUT
(∴ Need extra criteria)
Digitally illustrated by Kelsey Towers-Jones, 2021
∆𝐻𝑆
∆𝐻𝐿
iv. Draw a parallel line through R
v. Calculate
ℎ𝑆 = ℎ𝑅 −
𝑞ሶ 𝑠 + 𝑞ሶ 𝐿
𝑚ሶ 𝑠
vi. Locate point S
hR
:
i. Plot IN on the P-chart
=
SHF
(Inner)
hS
W
R
S
Tdb