3.7 DATA
REDUCTION
The
heat gained by the cold fluid is
Qc = mcCc(Tco
– Tci)
Where mc is mass flow rate and Cc
is the specific heat of the cold fluid. Tco and Tci are
the outlet and inlet temperatures of the cold fluid.
The heat lost by the hot fluid is
Qh = mhCh(Thi
– Tho)
Where mh is mass flow rate and Ch is
the specific heat of the hot fluid. Tho and Thi are the
outlet and inlet temperatures of the hot fluid.
The flow rate of the cold stream can be
found by using the Reynolds number expression,
|
DOUBLE
PIPE HEAT EXCHANGER USING NANO FLUID
CONCENTRATION
OF THE NANOFLUID IS :
copper
tube details:
internal diameter =7mm
outside
diameter =10mm
thickness =1.5mm
Gi pipe
Internal diameter =22mm
Outside diameter =27.5mm
Thickness =2.25mm
LENGTH
OF THE TEST SECTION =1 METER
|
|
Properties taken
for nanofluids
|
1)DENSITY OF THE PARTICLE =KG/M3
2)CALCULATED DENSITY OF THE
NANOFLUID } = KG/M3
3) SPECIFIC HEAT OF THE NANOFLUID = KJ/KG/K
4)THERMAL CONDUCTIVITY = Kw/MK
5)AVERAGE PARTICLE SIZE = NANO
METER
6)DYNAMIC VISCOSITY = Pa s
7)SPECIFIC HEAT OF THE NANO PARTICLE = KJ/KG K
TO FIND THE MASS FLOW RATE
OF THE HOT WATER
HOT WATER READING IN Measuring
Jar is maintained at a constant
Rate of 4 litres /minute for
all concentration .
EQUAL IN VOLUME RATE =4/1000
M3 / MINUITES
=4/1000/60 m3 /seconds
=4/1000*1/60 m3 /seconds
EQUAL IN VOLUME RATE =
4*10-3 /60 m3
/seconds
Volume rate =8.33*10-5 m3 /seconds
We know
density = mass /volume
Mass = volume *
density
Therefore mass Flow rate } =8.33*10-5 *1000
=0.0833 kg/second
Heat transfer of hot water :
Q w =Mw*cw*(∆t)
Qw =mw*cw
(Twater in-Twister out)
Qw
=0.0833*4.187*1
Qw =0.349 KW
VOLUME RATE OF COLD FLUID :Various Discharge RATES OF
0.2lpm,0.4lpm,0.6lpm,0.8lpm
Can be adjusted by the flow meter
TO FIND THE MASS FLOW RATE :
Density =
Mass flow rate/ Volume flow rate
Mass flow rate = Volume flow rate× Density
Q=ρAv
Where ρ =density of
the nanofluids in kg/m3
A=
cross sectional area in m2
V=
velocity of the nanofluids in m/s
Q=
mass flow rate of the nanofluids in kg/s
COLD fluids at
Varius discharge rates of 0.2LPM, 0.4LPM, &0 .6LPM
.8LPM:
Qcf =mcf *ccf (Tout–Tin) cf
Qmean = Qh +Q cf / 2
The
convective heat transfer co efficient for nano fluid were calculated
From
the following equation :
h cf =Qmean/A(TWALL-T
cf IN) KW/M2 K
Where Qmean =average heat transfer in
kw
A = area of the tube in m2
Twall = +T4+T5+T6⁄3 in°
centigrade
Tcf = temperature of
the nanofluid at inlet in ° centigrade
h cf = heat transfer coefficient of the nanofluid
The
nusselt number for nanofluid were calculated from the following
Equation
:
Nucf =h
cf D/k cf
where Nu cf =average
heat transfer co efficient Of the nanofluid
K cf = thermal conductivity of the
nanofluid
h cf = heat
transfer coefficient Of the nanofluids
D =internal diameter of
the test section
Pressure drop: ∆p
∆p =(ρhg –ρo)g
*H sin 48.5°
Instead of
hg we
have used ccl4
Where ∆p = pressure drop in Newton /m2
ρ ccl4 =density of carbon tetra chloride CCL4 is1594 kg/m3
g = acceleration dew to gravity 9.81
metre/sec2
H = difference of pressure head in metre
ρO =mass density of water at ambient
temperature
EFFECTIVENESS :Ԑ
The effectiveness of the heat exchanger can be calculated by,
Qact is the heat gained by the cold stream
Qmax = Cmin(Thi - Tci)
Where, Cmin = mcCc , mc is
the mass flow rate and Cc is the specific heat of the cold fluid. Thi
and Tci are the hot stream and cold stream inlet temperature.
FRICTION FACTOR :
f =64/Re
LMTD
(∆T)lm = (Tho _-Tci) -(Thi –Tco )/ ln [Tho-Tci]/[Thi
–Tco]
Where Tho =temperature hot out
Thi = temperature hot in
Tci = temperature cold in
Tco = temperature cold out
Where U
=overall heat transfer coefficient KW/M2 K
A =area in M2
LMTD =log mean temperature differences
Qc = heat transfer of nanofluids in KW
THEORETICAL NUSSELT NUMBER
NU =0.247*Re0.66Pr0.4
Where
Re =Reynolds Number
Pr = prandtl Number
Nu= Nusselt Number
Pr = Cpμ /k
CONVECTIVE HEAT TRANSFER
COEFFICIENT FOR HOT FLUID:
Qh =hhA ∆T
WHERE Qh
=Heat transfer rate of hot
fluid in kw
hh = Convective heat
transfer rate of hot fluid kw/m2k
A = Area πdl in m2
∆T = difference in
temperature in° centigrade
Qh =hA∆T
hh1 =276/ΠDL*1
hh1 =276/π*0.0334*1*1
hh1 =3297.8051W/M2K
hh1 =hh2 =hh3 =hh4
Since there is no change in temperature &heat
transfer rate of
hot fluid ( Here water is hot fluid)
The overall heat transfer
coefficient can be calculated by,
Q = U A (LMTD)
U =Q/A.LMTD
Where A is the total heat transfer area and Q = Qc,
LMTD
=(Tho-Tci)-(Thi-Tco)/In((Tho-Tci)/(Thi-Tco))
Ui = 1/{1/hi+ri/k*ln(ro/r
i)}
Where ,
hi
= convective heat transfer
co efficient of cold fluid in Kwm-2k-1
ri = radius of the inner tube in meter
ro = radius of the outer tube in meter
k =thermal conductivity of cold fluid
kWm-1k-1
The Nusselt number for a double pipe heat exchanger
is given by
Nu = 0.023Re0.8.Prn
Pr =prandtl number
Re = Reynolds
number
Nu = Nusselt number
n = 0.3 for cooling of fluids
NANOFLUID CONCENTRATION OF Nano Material fluid
particle used is (X)
DENSITY IN (X) CONCENTRATION OF NANOFLUID:
ρnf =φpρp
+(1-φ)ρf
Where f =base fluid water
Φ= nanoparticle volume fraction
P= particle
ρ
=density kg/m3
nf=nanofluids
ρnf 1 =φpρp + (1-φ) ρf
Specific
heat capacity of nanofluids is given as
:
Cpnf =φ (ρ cp)p +(1-φ ) (ρcp)f/ρnf
Where f =base fluid
Φ =nano particle volume fraction
p =particle
ρ =density/m3
nf =nanofluids