ABSTRACT The objectives of the cooling tower experiment are to determine the correlation of water to air mass ow ratio with increasing water ow rate and to determine the cooling load eect, the eect of dierent ow rates on the wet bulb approach. approach. Another Another objective objective is to estimate the evaporation evaporation rate of water (water (water loss) for the tower. tower. The experiment experiment is varied b using three three variables! variables! heating load, blower damper and water ow rate. The experiment is started b undergoing general start"up procedure. procedure. #alves $ to % are are closed, while valve & is partiall opened. The load and ma'e"up tan' is lled with de"ionised water. nstallation of cooling tower is done appropriatel. The water ow rate is set to *.+ -, heating load $.+ '/ and full opened the damper. The dierential pressure sensor is also chec'ed. The unit is left to operate for *+ minutes to achi achiev eve e stan standa dard rd stea stead d stat state e opera operati tion ons. s. /ater ater level level in ma'e ma'e"u "up p tan' tan' is observed and relled if it decreased. The rst experiment is started b varing the heating load. The variables are +.0 '/, $.+ '/ and $.0 '/. '/. /ater ow rate and blower damper is xed xed to *.+ - and full opened respectivel. The e1ciencies of cooling tower b using +.0 '/, $.+ '/ and $.0 '/ are $$23, 40 3, 5& 3 respectivel and their mass ow rate per area are $.%4& 6 $+ "2'g7m*s, $.%45 6$+ "2'g7m*s and $.%45 6$+ " 2
'g7m*s respectivel. n second experiments, the air ow is varied b full"open the blower ($++
3 air ow) and half"open the blower (0+ 3 air ow). The heating load and the water ow rate are xed to +.0'/ and *.+ - respectivel. ts e1ciencies are 5% 3 and 5% 3 respectivel while the mass ow rate per area are $.%456 $+ " 2
'g7m*s and $.%456 $+ "2'g7m*s respectivel. The third experiment is done in order to determine the eects of water
ow rate. Thus, the water ow rate is varied to *.+ -, *.8 - and *.5 -. The heating load and blower damper are xed to +.0 '/ and full"open respectivel. The e1ciencies of the cooling tower are $++ 3, $+% 3 and $$$ 3 respectivel. The mass ow rates per area are $.%4* 6 $+ "2'g7m*s, *.+22 6$+ " 2
'g7m*s and *.2&0 6$+ "2'g7m*s respectivel.
$
INTRODUCTION The laborator cooling tower is a cooling tower unit from a commercial c ommercial air conditioning sstem used to stud the principles of cooling tower operation. t is used in conjunction with a residential si9e water heater to simulate a cooling tower used to provide cool water to an industrial process. n the case of the laborator laborator unit, the industrial process process load is provided provided b the water heater. heater. The laborator cooling tower allows for complete control of the speed of the fan used in cooling the warm return water and the pump used to return return the cooled water to the water heater. heater. :xperiments can be conducted which stud how adjustment of one or both of these parameters aects the amount of heat removed from the water provided to the water heater.;ooling towers are heat transfer devices used to remove proc proces esss wast waste e heat heat to the the atmosphere atmosphere.. ;ool ;oolin ing g towe towers rs ma ma either either use use the the evaporation of water to remove process heat and cool the wor'ing uid to near the wet"bulb air temperature or rel solel on air to cool the wor'ing uid to near the dr dr" "bu bulb lb air te tempe mpera ratu ture re.. ;omm ;ommon on appl applic icat atio ions ns incl includ ude e cool coolin ing g the the circulating water used in oil reneries, reneries, chemical plants, plants, and building cooling. The towers var in si9e from small roof"top units to ver large hperboloid that can be up to *++ meters tall and $++ meters in diameter, or rectangular structures that can be over 8+ meters tall and 5+ meters long.
), form the second major reason. t is used to provide lower than ambient water temperatures and are more cost eective and energ e1cient *
than than most most other other alter alterna nati tives ves.. ;ool ;ooling ing towe towers rs are are commo commonl nl used used in man man commercial and industrial processes, according to its classifing use. ;ooling
towers also can
be categori9ed
b its air"to"water
ow. ;rossow
is one of them.
;rossow is a
design in which
the air ow is
directed
perpendicular
to the water ow
(gure$).
Ai Air
ow enters one
more
vertical faces of
or the
cooling
tower
the ll material.
/ater
to
meet ows
(perpendicular to the air) through the ll b gravit. The air continues through the ll and thus past the water ow into an open plenum area. A distribution or hot water basin consisting of a deep pan with holes or no99les in the bottom is utili9ed in a crossow tower. ?ravit distributes the water through the no99les uniforml across the ll material.
@igure$. crossow tpe design. The counterow is another design for cooling tower. tower. t is completel opposite to the above crossow design. Air ow enters one or more vertical faces of the cooling tower to meet the ll material. /ater ows (perpendicular to the air) through the ll b gravit gravit . The air continues through the ll and thus past the water ow into an open plenum area. A distribution or hot water basin consisting of a deep pan with holes or no99les in the bottom is utili9ed in a crossow tower. ?rav ?r avit it dist distri ribu bute tess the the wate waterr thr through ough the the no99 no99les les unifo uniform rml l acro across ss the the ll ll 2
material. 0 @igure*. counterow tpe design
OBJECTIVES
To determine the correlation correlation of water to air mass ow ratio with increasing increasing To water ow rate. To determine the cooling load eect. To To 'now the eect of dierent ow rates on the wet bulb approach. approach. To To estimate the evaporation rate of water (water loss) loss) for the tower. tower. To
THEORY A cooling tower is a speciali9ed heat exchanger that has been modied in which air and water are brought into direct contact for the transfer of heat to aect. To accomplish that, it is spraing a owing mass of water b the spra"lled tower into a rain"li'e pattern, through which an upward moving mass ow of cool air is induced induced b the action of a fan. ;ooling tower use the principle of evaporative or wet"bulbB cooling in order to cool the water. t has some advantages over a conventional heat"exchanger such as it can achieve water temperatures below the temperature of the air used to cool it. Cesides that, it is also smaller and cheaper for the same cooling load. gnoring an negligible amount of sensible heat exchange that ma occur through the walls or casing of the tower, the heat gained b the air must eDual to 8
the heat lost b the water b eDuilibrium. /ithin the air stream, the rate of heat gain is identied b the expression
• • •
G (h2 – h1) , whereE
G F ass ow of dr air through the towerGlb7min. h1 F :nthalp (total heat content) of entering airGCtu7b of dr air. air. h2 F :nthalp of leaving airGCtu7b of dr air. air.
/ithin the water stream, the rate of heat loss would appear to be L (t1 – t2) , whereE
• • •
L F ass ow of water entering the towerGlb7min. t1F =ot water temperature entering the towerGH@. towerGH@. t2 F ;old water temperature leaving the towerGH@. towerGH@.
This derives from the fact that a Ctu (Critish thermal unit) is the amount of heat gain or loss necessar to change the temperature of $ pound of water b $H@. =owever, because of the evaporation that ta'es place within the tower, the mass ow of water leaving the tower is less than that entering it, and a proper heat balance must account for this slight dierence.
air. H1 F =umidit ratio of entering airGlb vapor7lb dr air. air. H2 F =umidit ratio of leaving airGlb vapor7lb dr air.
The notation (t* " 2*) F An expression of water enthalp at the cold water temperatureGCtu7b. (The enthalp of water is i s 9ero at 2*H@) ncluding this loss of heat heat thr through ough evapo evapora rati tion on,, the the tota totall heat heat bala balanc nce e betwe between en air air and and wate water, r, expressed as a dierential eDuation, isE G dh = L dt + G dH (t2 - 32)
(1)
0
The expression I dtJ in eDuation ($) represents the heat load imposed on the tower b whatever process it is serving. =owever, because pounds of water per unit time are not easil measured, heat load is usuall expressed asE Heat Load = gpm x R x 81⁄3 = Btu/min.
(2)
where: o
gpm F /ater ow rate through process and over towerGgal7min. R F IKangeJ F Lierence between hot and cold water
o
temperaturesGH@. wate r. 81⁄3 F -ounds per gallon of water
o
Mote from formula (*) that heat load establishes onl a reDuired temperature dierential in the process water, and is unconcerned with the actual hot and cold water temperatures themselves. Therefore, the mere indication of a heat load is meaningless to the Application :ngineer attempting to properl si9e a cooling tower. tower. ore information of a specic nature is reDuired. Nptimum operation of a process usuall occurs within a relativel narrow band of ow rates and cold water temperatures, which establishes two of the parameters reDuired to si9e a cooling towerGnamel, gpm and cold water temperature. The heat load developed b the process establishes a third parameterGhot water temperature coming to the tower. @or example, letBs assume that a process developing a heat load of $*0,+++ Ctu7min performs best if supplied with $,+++ gpm of water at 50H@. /ith ith a sligh slightt tran transf sfor orma mati tion on of form formul ula a (*), (*), we can can dete determ rmine ine the the wate waterr temperature elevation through the process asE Therefore, the hot water temperature coming to the tower would be 50H@ O $0H@ F $++H@. =aving determined that the cooling tower must be able to cool $,+++ gpm of water from $++H@ to 50H@, what parameters of the entering air must be 'nownP :Duation ($) would identif enthalp to be of prime concern, but air enthalp is not someth something ing that that is routi routinel nel measur measured ed and record recorded ed at an geograp geographic hic location. /etbulb temperature is the onl air parameter needed to properl si9e a cooling tower, and its relationship to other parameters is as shown in the @igure @igure $ diagram.
%
igu!e 1
APPARATUS /ater cooling tower NL:E =:"$0*
EXPERIMENTAL PROCEDURE ?eneral start"up procedure.
$. #alve #$ to #% are are ensured ensured to be closed closed while valve valve #& is partiall partiall closed. closed. *. The load load tan' is lled lled with with deionised deionised water water.. 2. The ma'e"up ma'e"up tan' tan' is lled with with deionised deionised water water up to 9ero 9ero mar' on the 8. 0. %. &.
scale. Leionised Leionised water is added added to the the wet bulb sensor sensor reservoir reservoir to to the fullest. fullest. The appropri appropriate ate cooling cooling tower tower is install installed ed for the the experiment. experiment. All appropriat appropriate e tubing to the dierent dierential ial pressur pressure e sensor is connected connected.. The temperatur temperature e set point of of temperature temperature contro controller ller is set to to 80Q;. The The $.+ '/ water heaters is switched on and the water is heated up to approximatel 8+Q;. &
5. The pump is switched switched on and the the control control valve #$ is slowl slowl opened. opened. The The water ow rate is set to *.+ -. A stead operation where the water is distributed and owing uniforml through the pac'ing is obtained. 4. The fan damper damper is full opened opened and and the fan is switche switched d on. ;hec' ;hec' that the dierential pressure sensor is giving the reading E a. To measure measure the dierential dierential pressure pressure across across the orice, orice, open valve #8 and #0 ! close valve #2 and #%. b. To measure the dierential pressure across the column, open valve #2 and #% ! close valve #8 and #0. $+.The unit is being let to run for *+ minutes for the oat valve to correctl adjust the level in the load tan'. Kell the ma'e"up tan' as reDuired. $$.The unit is now read to use. :xperiment $. $. *. 2. 8. 0. %. &.
The heater is switched on and set to +.0 '/. '/. -ump and blower is then been switched on. The blower damper is full opened. The water ow rate is set set to * -. The water cooling tower is being let to operate for $+ minutes. The reading is ta'en when the oat valve is correctl adjusted.
:xperiment *. $. *. 2. 8. 0. %.
The heater is switched switched on and set set to +.0 '/. '/. The blower damper is full opened.
:xperiment 2. $. *. 2. 8. 0. %. &.
The heater is switched switched on and set set to +.0 '/. '/. -ump and blower are switched on. The blower damper is full opened. The water ow rate is set set to * -. The unit is being let let to operate operate for $+ minutes. The reading is ta'en ta'en after stead operation achieved.
?eneral shut"down procedure. $. The heater heater is switched switched o to let the the water to circulate circulate throu through gh cooling cooling tower for 2"0 minutes until the water is cooled down. 5
*. 2. 8. 0.
The blower blower is switche switched d o and the the blower blower damper is is full closed closed.. The pump pump and and power power suppl suppl is is switch switched ed o. The water water in the reservoir reservoir tan' is is retained retained.. The water water from from the the unit unit is completel completel drained drained o.
RESULTS DESCRIPTION TOP
Air Nutlet Lr Culb, T2 Air Nutlet /et Culb, T8 /ater nlet Temperature, T0
WATER FLOWRATE (LPM)
*0.+ *%.+
*8.5 *0.0
*8.0 *0.+
2+.*
*5.8
*&.8
*5.+ *&.2 *&.*
*&.& *&.* *&.+
*&.% *&.$ *&.+
*&.2 *&.0 *&.0
*&.* *&.8 *&.2
*%.4 *&.* *&.$
*&.% *&.0 *&.&
*&.0 *&.8 *&.%
*&.8 *&.+ *&.8
*5.+ *0.$ *0.$
*5.$ *8.4 *8.&
*&.5 *8.& *8.8
40
55
5+
*.+ 88 * /
*.8 8* % /
*.5 8* 0 /
STATION III
Air Lr Culb, T5 Air nlet /et Culb, T4 /ater Temperature, T$8 STATION II
Air Lr Culb, T$+ Air nlet Culb, T$$ /ater Temperature, T$0 STATION I
Air Lr Culb, T$* Air nlet /et Culb, T$2 /ater Temperature, T$% BOTTOM
Air nlet Lr Culb, T$ Air nlet /et Culb, T* /ater Temperature, T% Nrice Lierential, Lp (-a) /ater @low rate, @t (-) =eater -ower, R$
DESCRIPTION
Air nlet Lr Culb, T$ Air nlet /et Culb, T* Air Nutlet Lr Culb, T2 Air Nutlet /et Culb, T8 /ater nlet Temperature, T0 /ater Nutlet Temperature, T% Nrice Lierential, L-$
0.5 kW
HEATER POWER 1.0 kW
1.5 kW
*&.4 *8.% *8.+ *8.%
*&.4 *8.0 *0.+ *8.&
*5.+ *8.0 *%.* *0.8
*&.%
2+.*
2*.5
*8.*
*8.5
*0.%
%4
%$
8& 4
(-a) /ater @low Kate, @T$ (-) =eater -ower,R$ (/)
*.+
*.+
*.+
82%
5*+
$*20
DESCRIPTION
-ac'ing densit (m "$) Air nlet Lr Culb, T$ Air nlet /et Culb, T* Air Nutlet Lr Culb, T2 Air Nutlet /et Culb, T8 /ater nlet Temperature, T0 /ater Nutlet Temperature, T% Nrice Lierential, L-$ (-a) /ater @low Kate, @T$ (-) =eater -ower,R$ (/) -ressure drop across pac'ing L-* (-a)
AIR FLOW 100% 50%
$$+ *&.4 *8.0 *0.5 *%.+ *4.% *0.* 24 *.+ 88* &
$$+ *5.+ *8.% *0.8 *0.& *4.+ *0.$ 20 *.+ 88+ %
SAMPLE CALCULATION ;ross sectional area area E **0 cm * =igh
E %+ cm E $$+ m "$
-ac' column
:>-:K:MT $E :@@:;T N@ =:ATM? NAL @ixed variables! vari ables! $. Air ow ow F $++3 $++3 (Lamp (Lamper er full full open) open) *. /ater ater ow ow rate rate F *.+ *.+ - a) =eating load F $.+ '/ R!"# $ &$$'!" $*#+ !
Kange
F /ater inlet temperature, T0 " water outlet temperature, T% F 2+.*S; *8.5S; F0.8S;
A,,+$&- $ &$$'!" $*#+
$+
Approach F /ater /ater outlet temperature, T% Air outlet wet bulb, T* F *8.5S; *8.0 S; F +.2S ; E/&#!& $ &$$'!" $*#+
UF
range range + approach
6$++
5.4
F
5.4
+0.3 6 $++
F 40 3 T$' &$$'!" '$2
;ooling load F pump input, R$ O heating load F 5*+ / O
(
1.0 kW ×
1000 W 1 kW
)
F $5*+ /
A+ 3 4$* +# ,#+ ! +#
´ ( (m / s ) V 3
´ ( kg / m s )= m 2 (m3 / kg ) A ( m ) . V ( 2
^
@rom pschometric chart ( (@elder (@elder V Kousseau, Kousseau, *++0, p. 250)! 250) ! Air inlet wet bulb, T* W T wb F *8.0 S ; nterpolationE T*6 (7C)
V ^
(389k")
*+.++ *8.0+
+.50
2+.+%
+.4+
V ^
$$
−20.00 V − 0.85 = 30.06 −20.00 0.9− 0.85 24.50
^
V F +.5&* m27'g ^
;ross"sectional Area of tan' load F **0 cm * F +.+**0 m* Thus!
´ F m
| |
L 2.0 min
3
1 min
1m
60 s
1000 L
|
( 0.0225 m ) ( 0.872 m / kg ) 2
3
F $.%45 6 $+"2 'g7m*s W#+ 3 4$* +# ,#+ ! +#
´ ( kgof air / m s ) m ´ ( kgof water / m s )= m hr ( kgwater / kgair ) 2
2
@rom pschometric chart ( (@elder (@elder V Kousseau, Kousseau, *++0, p. 250)! 250) ! Air inlet wet bulb, T* W T wb F *8.0 S ; nterpolationE T*6 (7 (7C)
-+(k" *#+9k" +)
*+.++ *8.0+ 2+.+%
+.+*5% hr +.+$85
h −0.0286 −20.00 = r 30.06 − 20.00 0.0148 − 0.0286 24.50
hr F +.+**8 'g water7'g air
´= m
−3 1.698 × 10 kgair
water 0.0224 kg water
2
/m s
/ kgair
F +.+&05 'g7m *s $*
W#+ 3 4$* +# ,#+ ! +#
´ ter / m s ) m ( kg of water wa 2
r=
r=
´ (kg of air m air / m s ) 2
0.0758 −3 1.698 × 10
r F 88.%8 H#!" '$2 (kW) R!"# (7C) A,,+$&- $ &$$'!" *#+ (7C) E/&#!& $ &$$'!" *#+: ; (%) T$' &$$'!" '$2 (W) A+ 3 4$* +# ,#+
0.5
1.0
1.5
2.8 "+.8
0. 8 +. 2
&.* $.$
$$2
40
5&
42% $.%4& 6 $+
! +# (k"93 <) W#+ 3 4$* +#
$5*+ "2
$.%45 6 $+
*&20 "2
$.%45 6 $+ "2
+.+&5%
+.+&05
+.+&05
8%.2*
88.%8
88.%8
,#+ ! +#(k"93 <) W#+ 3 4$* +# $ + 3 4$* +# +$: +
:>-:K:MT *E CN/:K LA-:K @ixed variables! vari ables! $. =eat =eatin ing g loa load d F +.0 +.0 '/ '/ *. /ater ater ow ow rate rate F *.+ *.+ - a) Air ow F $++ 3 (Clower full open) R!"# $ &$$'!" $*#+ !
Kange
F /ater inlet temperature, T0 " water outlet temperature, T% F *4.% S; *0.* S; $2
F 8.8 S; A,,+$&- $ &$$'!" $*#+
Approach F /ater /ater outlet temperature, T% Air inlet wet bulb, T* F *0.* S; *8.0S; F +.& S; E/&#!& $ &$$'!" $*#+
UF
range range + approach
6$++
4.4
F
4.4
+ 0.7 6 $++
F 5% 3 T$' &$$'!" '$2
;ooling load F pump input, R$ O heating load
(
F 88* / O
0.5 kW ×
1000 W 1 kW
)
F 48* / A+ 3 4$* +# ,#+ ! +#
´ ( (m / s ) V 3
´ ( kg / s )= m
A ( m ) . V ( m / kg ) 2
3
^
@rom pschometric chart ( (@elder (@elder V Kousseau, Kousseau, *++0, p. 250)! 250) ! Air inlet wet bulb, T* W T wb F *8.0S; nterpolationE T*6 (7C)
V ^
(389k")
*+.++ *8.0
+.50
2+.+%
+.4+
V ^
$8
−20.00 V − 0.85 = 30.06 −20.00 0.9− 0.85 24.50
^
V F +.5*& m 27'g ^
´ m
F
| |
L 2.0 min
3
1 min
1m
60 s
1000 L
|
( 0.0225 m ) ( 0.872 m / kg ) 2
3
F $.%45 6 $+ "2 'g7m*s W#+ 3 4$* +# ,#+ ! +#
´ ( kgof air / m s ) m ´ ( kgof water / m s )= m hr ( kgwater / kgair ) 2
2
@rom pschometric chart ( (@elder (@elder V Kousseau, Kousseau, *++0, p. 250)! 250) ! Air inlet wet bulb, T* W T wb F *8.0 S ; nterpolationE T*6 (7 (7C)
-+(k" *#+9k" +)
*+.++ *8.0+ 2+.+%
+.+*5% hr +.+$85
h −0.0286 −20.00 = r 30.06 − 20.00 0.0148 − 0.0286 24.50
hr F +.+**8 'g water7'g air
´= m
−3 1.698 × 10 kgair
water 0.0224 kg water
2
/m s
/ kgair
F +.+&05 'g7m *s W#+ 3 4$* +# $ + 3 4$* +# +$
$0
´ ter / m s ) m ( kg of water wa 2
r=
r=
´ (kg of air m air / m s ) 2
0.0758 −3 1.698 × 10
r F 88.%8
A+ F'$* R!"# (7C) A,,+$&- $ &$$'!"
100%
50%
8.8 +.&
2.4 +.0
*#+ (7C) E/&#!& $ &$$'!"
5%
54
*#+: ; (%) T$' &$$'!" '$2 (W) A+ 3 4$* +# ,#+
48* $.%45 6 $+"2
48+ $.%4& 6 $+ "2
! +# (k"93 <) W#+ 3 4$* +#
+.+&05
+.+&5%
88.%8
8%.2*
,#+ ! +#(k"93 <) W#+ 3 4$* +# $ + 3 4$* +# +$: +
:>-:K:MT 2E /AT:K @N/ KAT: @ixed variables! vari ables! $. =eat =eatin ing g loa load d F +.0 +.0 '/ '/ *. Air @low @low F $++ 3 (Clowe (Clowerr full full open) open) a) /ater @low Kate F *.+ - R!"# $ &$$'!" $*#+ !
Kange
F /ater inlet temperature, T0 " water outlet temperature, T% F 2+.* S; *0.$ S; F0.$S;
A,,+$&- $ &$$'!" $*#+
%$ Approach F /ater /ater outlet temperature, T% Air inlet wet bulb, T* F *0.$S; *0.$S; F + S;
E/&#!& $ &$$'!" $*#+
UF
range range + approach
6$++
5.1
F
6 $++
+
5.1 0
F $++ 3 T$' &$$'!" '$2
;ooling load F pump input, R$ O heating load
(
F 88* / O
0.5 kW ×
1000 W 1 kW
)
F 48* /
A+ 3 4$* +# ,#+ ! +#
´ ( (m / s ) V 3
´ ( kg / s )= m
A ( m ) . V ( m / kg ) 2
3
^
@rom pschometric chart ( (@elder (@elder V Kousseau, Kousseau, *++0, p. 250)! 250) ! Air inlet wet bulb, T* W T wb F *0.$ S ; nterpolationE T*6 (7C)
V ^
(389k")
*+.++ *0.$
+.50
2+.+%
+.4+
V ^
$&
−20.00 V − 0.85 = 30.06 −20.00 0.9− 0.85 25.1
^
V =¿ +.5&0 m27'g ^
´ m
F
| |
L 2.0 min
3
1 min
1m
60 s
1000 L
|
( 0.0225 m ) ( 0.875 m / kg ) 2
3
F $.%4* 6 $+"2'g7m*s W#+ 3 4$* +# ,#+ ! +#
´ ( kgof air / m s ) m ´ ( kgof water / m s )= m hr ( kgwater / kgair ) 2
2
@rom pschometric chart ( (@elder (@elder V Kousseau, Kousseau, *++0, p. 250)! 250) ! Air inlet wet bulb, T* W T wb F *8.% S ; nterpolationE T*6 (7 (7C)
-+(k" *#+9k" +)
*+.++ *8.%+ 2+.+%
+.+*5% hr +.+$85
h −0.0286 −20.00 = r 30.06 − 20.00 0.0148 − 0.0286 24.60
hr F +.+**2 'g water7'g air
´= m
−3 air 1.692 × 10 kg air
0.0223 kgwater
2
/m s
/ kgair
F +.+&04 'g7m *s W#+ 3 4$* +# $ + 3 4$* +# +$
´ ter / m s ) m ( kg of water wa 2
r=
´ (kg of air m air / m s ) 2
$5
r=
0.0759 −3 1.692 × 10
r F 88.5%
W#+ F'$* R# (LPM) R!"# (7C) A,,+$&- $ &$$'!"
<.0
<.=
<.>
0.$ +
2. & "+.*
2.+ "+.2
*#+ (7C) E/&#!& $ &$$'!"
$++
$+%
$$$
*#+: ; (%) T$' &$$'!" '$2 (W) A+ 3 4$* +# ,#+
48* $.%4* 6 $+"2
4*% *.+226 $+"2
4*0 *.2&0 6$+"2
! +# (k"93 <) W#+ 3 4$* +#
+.+&04
+.+4*4
+.$+&*
88.5%
80.&+
80.$8
,#+ ! +#(k"93 <) W#+ 3 4$* +# $ + 3 4$* +# +$: +
SAMPLE ERROR CALCULATION There are some errors errors that present in the calculation of E/&#!& $ &$$'!" *#+: ; (%) for experiment $ and 2.
:>-:K:MT $ E :@@:;T N@ =:ATM? NAL H#!" '$2 (kW) R!"# (7C) A,,+$&- $ &$$'!" *#+ (7C) E/&#!& $ &$$'!"
0.5
1.0
1.5
2.8 "+.8
0. 8 +. 2
&.* $.$
$$2
40
5& $4
*#+: ; (%) T$' &$$'!" '$2 (W) A+ 3 4$* +# ,#+
42% $.%4& 6 $+
! +# (k"93 <) W#+ 3 4$* +#
$5*+ "2
$.%45 6 $+
*&20 "2
$.%45 6 $+ "2
+.+&5%
+.+&05
+.+&05
8%.2*
88.%8
88.%8
,#+ ! +#(k"93 <) W#+ 3 4$* +# $ + 3 4$* +# +$: +
The e1cienc of cooling water for +.0 '/ heating load is supposed to be less than $++3 li'e the rest of manipulated variable, vari able, $.+ '/ and $.0 '/. =owever, UF F
range range + approach 6$++
2.8
x $++
2.8"+.8 F $$2 3 This is due to the temperature temperature of approach cooling water having a negative value. t is supposed to be greater than + S;.
:>-:K:MT 2E :@@:;T N@ /AT:K /AT:K @N/ KAT: W#+ F'$* R#
<.0
<.=
<.>
(LPM) R!"# (7C) A,,+$&- $
0.$ +
2.& "+.*
2.+ " + .2
&$$'!" *#+ (7C) E/&#!& $
$++
$+%
$$$
(%) T$' &$$'!" '$2
48*
4*%
4*0
(W) A+ 3 4$* +#
$.%4* 6 $+"2
*.+226 $+"2
*.2&0 6$+"2
+.+&04
+.+4*4
+.$+&*
&$$'!" *#+: ;
,#+ ! +# (k"93<) W#+ 3 4$*
*+
+# ,#+ ! +#(k"93<) W#+ 3 4$*
88.5%
80.&+
80.$8
+# $ + 3 4$* +# +$: +
range range + approach 6$++
2.&
x $++
2.& +.* F $+% 3 @or water ow rate of *.5 -,
UF F
range range + approach 6$++
2.+
x $++
2.+ +.2 F $$$ 3 This is also due to the temperature of approach cooling water having having a negative value. t is supposed to be greater than + S;.
DISCUSSION The experiment that was carried out is called cooling tower experiment. ;ooling tower is a device that rejects rejects heat which removes removes the waste heat to the atmosphere to achieve the temperature needed. The tpe of heat rejection in a cooling tower is termed XevaporativeX where it allows a small portion of the *$
water being heated to evaporate then is condensed condensed into a moving air stream to provide signicant cooling to the rest of that water stream. The heat from the water stream transferred to the air stream raises the airYs temperature and its relative humidit to $++3, and this air is discharged to the atmosphere. The objectives of the cooling tower experiment are $ 2##+3!# -# &$++#'$! $ *#+ $ + 3 4$* +$ *- !&+#!" *#+ 4$* +# and $ 2##+3!# -# &$$'!" '$2 #?#&: !2 -# #?#& $ 2?#+#! 4$* +# $! -# *# 6'6 ,,+$&-. Another objective is $ #3# -#
experiment is #@,$+$! +# $ *#+ (*#+ '$) $+ -# $*#+ . The experiment varied b using three variables! heating load, blower damper and water ow rate.
The correlation of water to air mass ow ratio is called +, is important to 'now 'now the portio portion n transf transferr erred ed b evapora evaporatio tion. n. The higher higher the evapor evaporati ation on of water, the mass ow rate of the water will be reduced which is what we actuall wanted. Nnce the water mass ow rate is reduced, the mass ow rate of air that enters the column pac'ing remains the same. LPM, the the + values are ==.>: =5.0 !2 =5.1= respectivel. /e can see that the water ow rate aects the r value for which the higher the water ow rate produces higher + value. . =ence, the cooling eectiveness will be higher in water ow rate of *.+ -. Nther than that, cooling load also determine the performance of cooling tower. ;ooling load is the rate at which heat is removed from the water. The higher the cooling load, the higher the heat removal from the water. =ence, the water water wil willl experi experienc ence e lower lower tempera temperatur ture e which which is actual actuall l that that we wanted wanted.. =owe =owever ver,,
the the cool coolin ing g load load is diere dierent nt accor accordi ding ng to its its para parame mete ters rs.. @or
parameter of heating load, of 0.5 kW: 1.0 kW !2 1.5 kW, the cooling loads are 8 W: 1><0 W !2 <85 W respectivel. /e can see that the higher the **
heating load, the higher the cooling load would be. This is because the heating load is actuall the power of the pump that compresses the water to increase the temperature and also pressure of the water. The higher the heating load, the higher the evaporation rate of the water. Thus, the temperature dierence of the evaporated water with the temperature of air in the cooling tower will bring to great heat removal from the evaporated water. water. @or param paramet eter er of blow blowin ing g damp damper, er, which which are are -' -' $,#!# $,#!#2 2 !2 !2 '' '' $,#!#2, the cooling loads are =0 W !2 =< W respectivel. /e can come
into a conclusion that when the area of the damper is larger, the cooling load will be increasing increasing because when the area of damper blower is wide, more air will be entered the cooling tower hence will cooled the evaporated more eectivel. LPM, the cooling loads are =< W: < W !2 <5 W respectivel. Motice that, the higher the water ow rate, the lower the cooling load. This is due to the amount of water ows in certain time is in small portion.
n addition, approach is another term that used in cooling tower that tells how closel the leaving cold water temperature approaches the entering air wet bulb temperature. To be exact it is actuall the temperature dierences between the water leaving the cooling tower and the ambient wet"bulb temperature. Approach is the most important indicator of cooling water performance because it dictates the theoretical limit of the leaving cold water temperature and no matter the si9e of the cooling tower, range or heat load, it is not possible to cool the water water below the wet bulb tempera temperatur ture e of air. air.
=ence, =ence, the leaving leaving water water
temperature must be higher than the wet bulb temperature. The dierent air ow rates will aect the approach of the experiment. n this experiment, when the 6'$*#+ 23,#+ $,#!#2 '' , the + 3 4$* +# 1.> 10 8 k"93< while when the 6'$*#+ 6'$*#+ 23,#+ 23,#+ -'$,# -'$,#!#2 !#2 , the + 3 4$* +# 1. 108 k"93<. The higher the air mass ow rate, the higher the
*2
approach would be because the air that enters through the blower will decrease the wet bulb temperature so that the water leaving the tower will be higher than the wet bulb temperature. @urthermore, during the experiment there are some errors that occurred. The error is that we did not ta'e the amount of water loss from the ma'e"up tan' ever time the variables are changed.
CONCLUSION @rom the experiment that has been conducted we can conclude that, all objective of this experiment is achieved. The correlation of water to air mass ow ratio with increasing water ow rate has been determined. /here for water ow rates of <.0 LPM: <.= LPM and <.> LPM, the + values are ==.>: =5.0 !2 respectivel el.. /e also manage to calculate calculate the eectiveness eectiveness of cooling cooling =5.1= respectiv tower which is the highest at *.+ - for 100%. The eect of heating load to the cooling tower is also achieved. The higher the amount of heating load, the more eective is the cooling tower performance. Nther than that, cooling tower with *8
full opened blower will operate more eective compared with cooling tower with half full opened. This experiment was not conducted successfull as there are errors when conducting the experiment.
RECOMMENDATIONS The time reDuired before all the reading is ta'en should be *0 to 2+ minutes to ma'e sure the operation is stead and stable. a'e sure all the bulbs are full with water so that it will not aect the experiment. :ver experiment should be done in 2 times and record all the reading before calculate the average reading. /e should wait about 2+ minutes before starting ever new experiment to ensure that the eDuipment in the stable condition. Auxi Auxilia liar r heat heater er shou should ld be used used durin during g this this expe experi rime ment nt in orde orderr to increase the temperature dierence between the cool suppl water and the return water. water. This will allow the larger enthalp dierence. Lo not put hands or something at an rotation eDuipment li'e fan or blower to avoid from f rom an error in reading and experiment. Lo not not touc touch h an an elec electr tric ical al conn connec ecti tion on and and tur turn o elec electr tric ic main main immediatel if there is an eDuipment malfunctions. ab coats, goggles and safet helmet must be wearing before doing the experiment.
REFERENCES $. (*++%). (*++%). K Ketrieve etrieved d a *4, *+$*, from from ;hemical ;hemical :ngineer :ngineer E httpE77chem.engr.utc.edu7webres7820@72T";T72T";T.html *. Applications of Cooling Tower Tower . (n.d.). Ketrieved Ketrieved a *4, *+$*, from httpE77ieeexplore.ieee.org7xpl7freeabsZall.jspParnumberF0&8&4$4 2. ;engel, [. A., V Coles, Coles, . A. A. (*++&). (*++&). Thermodynamics, An ngineering Approach!
*0
8. Cooling Tower . (*+$$, \anuar 0). Ketrieved a *4, *+$*, from f rom httpE77www.cti.org7whatis7coolingtowerdetail.shtml 0. Cooling Towers. (n.d.). Ketrieved a *4, *+$*, from =drosenseE httpE77www.hdrosense.bi97index.php7sectors7cooling"towers7P gclidF;>?D0bhia5;@]x&%wod\g"\g %. @elder, K. K. ., V Kousse Kousseau, au, K. K. /. /. (*++0). (*++0). lementary "rinciples of Chemical "rocesses! ]nited
&. Morm Morman an,, /.
APPENDICES
*%
*&
@igure * E -sichometric ;hart
*5
