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7/25/2019 Cooling tower expt
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SCHOOL OF CHEMICAL AND BIOMEDICAL
ENGINEERING
(Division of Chemical & Biomolecula En!ineein!"
Nan#an! $echnolo!ical %nivesi#
CH'()*
E+,eimen CE-Coolin! $o.e
Sho Re,o
Gou, mem/es0 Chan 1ei Shan (%22*)3)34"
Hu Sihui (%22**5)*L"
Sim 6an! Ron! (%22*27354"
8u 4im 9an! (%22**7*G"
Gou, 0 G9
Dae of E+,: 0 ;h
Se,em/e *)2'< $hus=a#
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1
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Sho e,o > CE- Coolin! $o.e
2" Ino=ucion an= O/?ecives
Cooling tower is a heat removal device where heat exchanges happen between high
temperature fluid and low temperature fluid. It consists of two main type, where heatis removed either by the evaporation of water or by low temperature air. An example
of counter-current device is used in this experiment to demonstrate the operating
theory of the cooling tower. The water stream enters the device from the top while air
is introduced from the bottom due to density difference. Once in contact, heat
exchange will happen at the interface, which will lead to water evaporation. Thus
latent heat is transferred from hot water to bul air by water vapour. Also, throughout
the cooling tower, pacing material is used to increase the contacting surface area
between air and water. As a result of heat and mass transfer, the temperature of water
outflow is lower than the temperature of water inflow, while air outflow is at higher
temperature and humidity compared with air inflow.
The frst objective o the experiment was to examine the mechanicso a bench-scale cooling tower under dierent cooling loads. Thesecond aim was to practice using a psychrometric chart and tocalculate mass and energy balances.
*" Summa# of chan!es o ,oocol
!. The fan inlet shutter was half open rather than fully open.
". The regular interval adopted was " minutes rather than !# minutes. Also the total
experimental time is $# minutes for each run.
%. The tan was refilled after each time interval rather than at the end of one run. Theaverage was taen to estimate the mae-up &uantity.
$. The mae-up water &uantity was determined by taing the difference between the
initial and final water level readings.
2
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'" Resuls
':2 Daa esuls fom e+,eimens
'sing the raw data recorded in tables A! and A" in the appendix, the mean values of
temperatures, water flow rate and orifice differential were calculated. These measured&uantities recorded in the appendix were taen at intervals of " minutes over a time
period of $# minutes for cooling load !.#( and !.)(.
Table !* Tabulation of the mean values of data of cooling load !.#( and !.)(
Cooling load !.#( !.)(
Time interval
" minutes
interval over a
period of $#
minutes
" minutes
interval over a
period of $#
minutes
Air inlet dry bulb
temperature, t!+C"%./ "$.%%
Air inlet wet bulb
temperature, t"+C!0.$! !0.$
Air outlet dr bulb
temperature, t%+C"$.)" "/.
Air oulet wet bulbtemperature, t$+C
"%./# ").0/
(ater inlet
temperature, t)+C%#.1/ %/."$
(ater outlet
temperature, t/+C"%. ").0#
Orifice 2ifferential
+mm 3"O!1./ !1.0#
(ater flow rate +g4s %/."1 %/.##
5ae-up &uantity
+m6$1.)# //.")
5ae-up &uantity
+g#.#$1)# #.#//")
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':* Calculaions
a. 'sing the psychometric chart provided +prepared for ! atm pressure, estimate the
specific humidity, enthalpy and specific volume of inlet and outlet for each run.
Table "* Tabulation of specific humidity, enthalpy and specific volume of inlet and outlet ofeach run
b. 7erform a
mass balance
for each run to
determine the
extent to
which the
rate of mae-up addition agrees with the rate of evaporation.
i: Mass /alance calculaions fo 2:)@1
'sing the relation between pressure drop across the orifice and air flow rate given
in the laboratory manual,
ma=0.0137 x
v top (1+utop )
0.0137 17.86
0.867 (1+0.0181 )
ma=0 .0616 kg /s
!
Cooling load +( !.# !.)
hbottom+84g )).") )/.)#
ubottom+g 3"O 4 g
dry air#.#!"" #.#!"/
vbottom+m%4g #.) #.)0
htop+84g 1#.1) #.##
utop +g 3"O 4 g
dry air#.#!! #.#"#0
vtop+m%4g #./1 #.10
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Sein! u, a s,ecies mass /alance on ai acoss he =oe= line /oun=a#