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http://www.iaeme.com/ijte/index.asp 10 [email protected]
International Journal of Thermal Engineering (IJTE)
Volume 6, Issue 1, Jan–June 2018, pp. 10–17, Article ID: IJTE_06_01_002
Available online at
http://www.iaeme.com/ijte/issues.asp?JType=IJTE&VType=6&IType=1
ISSN: 2347-3932
© IAEME Publication
CONDENSATION RATE ENHANCEMENT OF
FLUID IN STEAM CONDENSER BY MIXING
NANOPARTICLES
Ajeet Kumar
Assistant Professor, Guru Nanak Institute of Technical Campus, Hyderabad, India
Mukesh Kumar
Lecturer, Assosa University, Ethiopia
Yohannes Feyissa Beyisho
Dean, Assosa University, Ethiopia
Vipul Kumar Sharma
Research Assistant, Drexel University, Philadelphia, PA, US
ABSTRACT
In thermal power plants, the application of a steam condenser is to condense the
exhaust steam from a steam turbine to obtain maximum shaft work, and to change the
turbine exhaust steam into pure water so that it may be reused in the steam
generator boiler as boiler feed water. Condensation rate depends on the physical
properties of steam and the condensate. Condensate properties can be changed
significantly by mixing nanoparticle like Al2O3, SiO2 and CuO. In this paper analysis
of enhancement of condensation rate has been done by changing the thermophysical
properties of condensate by mixing nanoparticle. Mathematically, value of thermal
conductivity, density, absolute viscosity, convective heat transfer coefficient, and mass
condensation rate of fluid at different value of volume fraction has been determined.
Key words: Condenser, condensate, volume fraction and nanoparticle
Cite this Article: Ajeet Kumar, Mukesh Kumar, Yohannes Feyissa Beyisho and
Vipul Kumar Sharma, Condensation Rate Enhancement of Fluid in Steam Condenser
by Mixing Nanoparticles. International Journal of Thermal Engineering, 6 (1), 2018,
pp. 1–9.
http://www.iaeme.com/ijte/issues.asp?JType=IJTE&VType=6&IType=1
NOMENCLATURE
Symbols
kp Thermal conductivity of nanoparticle [W/m°C]
kf Thermal conductivity of fluid [W/m°C]
Greek symbols
φ Volumetric fraction [-]
ρf Density of fluid [kg/m3]
Condensation Rate Enhancement of Fluid in Steam Condenser by Mixing Nanoparticles
http://www.iaeme.com/ijte/index.asp 11 [email protected]
keff Thermal conductivity of nanofluid [W/m°C]
h Convective heat transfer coefficient [W/m2°C]
hfg Latent heat of vaporization [W/m2°C]
Q Heat transfer rate [W]
m Mass rate of condensation [gram/meter]
tsat Saturation temperature of fluid [°C]
ts Surface temper of pipe [°C]
D Diameter of condenser pipe [m]
g Acceleration due to gravity [m/s2]
ρp Density of nanoparticle [kg/m3]
ρeff Density of liquid nanofluid [kg/m3]
ρv Density of vapour nanofluid [kg/m3]
µf Viscosity of fluid [Ns/m2]
µeff Viscosity of nanofluid [Ns/m2]
1. INTRODUCTION
Condenser is a heat exchanging device used to convert steam into water. This is a type of heat
exchanger. In heat exchanger phenomena of heat transfer is complicated because at the time
of condensation phase change takes place from vapor to liquid. In condenser heat transfer take
place at constant temperature. Size of condenser depends on compactness of condenser
(surface area per unit volume), properties of material, direction of fluid flow, and properties of
cooling and heating fluids. Thermal conductivity of fluids can be improved substantially by
mixing nanoparticle. Size of nanoparticle, volume concentration and different types of
nanoparticle affect the properties of fluids.
Heat exchanger has been classified in different ways. Based on direction of flow: counter
flow, parallel flow, and cross flow have been classified. Counter flow has more value of log
mean temperature difference compared to remaining two. But crossflow is more compact
compare counter flow. When vapor condenses, there is liquid film formation takes place on
the surface of the condenser. Liquid films cover the surface and avoid direct contact of steam
with cooling surface.
1.1. Nanofluids and its Thermo Physical Property
Thermo physical properties of the nanofluids are very important for prediction of heat transfer
behavior. It becomes exceedingly valuable in the control for energy saving perspectives of the
industrial. There is always a significant industrial interest in nanofluids and nanoparticles.
Especially nanoparticles play immense potential for the improvement of thermal transport
properties compared to conventional micrometer sized particles, millimeter and particles
fluids suspension. In the last decade, due to its enhanced thermal properties, nanofluids have
gained significant attention.
Studies have shown that thermal conductivity of nanofluids depends on many factors such
as particle volume fraction, material, particle size, shape, base fluid material, and temperature.
The thermal conductivity enhancement was also shown to be effective in amount and types of
additives and the acidity of the nanofluid. The transport properties of nanofluids: viscosity
and dynamic thermal conductivity are dependent on volume fraction of nanoparticle and is
highly dependent on other parameters such as particle size, shape, mixture combinations and
surfactant, slip mechanisms, etc. Experimental studies showed that by use of nanofluid
compared to base fluid the thermal conductivity and viscosity both increases. Thus far,
different theoretical and experimental studies have been conducted and various correlations
have been proposed for dynamic viscosity and thermal conductivity of nanofluids. So far, due
to lack of collective understanding on mechanism of nanofluid no general correlations have
been established. There are limited rheological studies reported in the literature for viscosity
as compared with the experimental studies on thermal conductivity of nanofluids. To model
Ajeet Kumar, Mukesh Kumar, Yohannes Feyissa Beyisho and Vipul Kumar Sharma
http://www.iaeme.com/ijte/index.asp 12 [email protected]
the effective viscosity of nanofluid as a function of volume fraction different models of
viscosity have been used by researchers.
1.2. Application of Nanofluids
The novel and advanced concepts of nanofluids offer fascinating heat transfer characteristics
compared to conventional heat transfer fluids. There are considerable Researches on the
superior heat transfer properties of nanofluids especially on thermal conductivity and
convective heat transfer. Applications of nanofluids in industries such as heat exchanging
devices appear promising with these characteristics. Kostic reported that nanofluids can be
used in following specific are as: Heat-transfer nanofluids.
Tribological nanofluids.
Surfactant and coating nanofluids.
Chemical nanofluids.
Process/extraction nanofluids.
Environmental (pollution cleaning) nanofluids.
Bio-and pharmaceutical-nanofluids.
Medical nanofluids (drug delivery and functional tissue–cell interaction
2. THERMAL CONDUCTIVITY
Maxwell was first to propose model for conductivity of heterogeneous mixture. Thermal
conductivity model is based on continues and discontinues phase. The effective thermal
conductivity has been given by Maxwell [5] as
=
(1)
2.1. Viscosity
Viscosity is an important parameter when dealing with nanofluid. It directly affects the
pressure drop and pumping power of the system. Einstein [6] proposed the viscosity model
which has been used by Brinkmann to calculate viscosity of particles suspended in fluid.
Brinkmann model [7] includes the volume concentration of nanoparticles as shown in
equation.
=
(2)
Where 𝛍eff is the dynamic viscosity of nanofluid and 𝛍f is the dynamic viscosity of the
base fluid.
2.2. Density
Pak and Cho [13] used following equation for calculating density of nanofluids
ρeff = ρp +(1- )ρf (3)
Where ρp and ρf are the density of particle and base fluid respectively
3. CONDENSATION
Condensation is a process in which vapour converted into liquid when it comes to the contact
of liquid surface. Depending on nature of cold surface, condensation is classified in two in
Condensation Rate Enhancement of Fluid in Steam Condenser by Mixing Nanoparticles
http://www.iaeme.com/ijte/index.asp 13 [email protected]
two ways: Film condensation & Dropwise condensation. When condensate tends to wet the
cold surface and thereby makes a liquid film, then condensation process is called film
condensation. In dropwise condensation, the vapour condenses into small liquid droplets of
various sizes which fall down the surface in random fashion.
Figure 1 Dropwise and Filmwise Condensation
3.1. Film heat transfer coefficient
Nusselt’s analysis for laminar filmwise condensation on horizontal tubes leads to the
following relation:
=0.0725[
]
for single horizontal tube.
Here, D=2.5cm, tsat =90°C, ts = 70°C, and hfg = 2309kJ/kgK has been taken. Pressure
inside the inside the condenser is 0.7 bar.
3.2. Rate of Condensation
The rate of condensation for the single tube per meter length is
m =
=
Table 1 Effective thermal conductivity of nanofluid
S.No Fluid
conductivi
ty(Kf)
W/m°C
Thermal conductivity of
nanoparticles(Kp)
W/m°C
Volume
fraction
(φ)
Thermal conductivity of
nanofluids(Keff)
W/m°C
Water
Al2O
3 CuO
SiO
2
TiO
2 Al2O3 CuO SiO2 TiO2
1 0.65 40 33 1.4 8 0.01 0.6561 0.6561 0.6518 0.6551
2 0.65 40 33 1.4 8 0.02 0.6622 0.6620 0.6536 0.6601
3 0.65 40 33 1.4 8 0.03 0.6681 0.6679 0.6554 0.6651
4 0.65 40 33 1.4 8 0.04 0.6739 0.6736 0.6571 0.6699
5 0.65 40 33 1.4 8 0.05 0.6796 0.6793 0.6589 0.6747
6 0.65 40 33 1.4 8 0.06 0.6851 0.6848 0.6607 0.6794
7 0.65 40 33 1.4 8 0.07 0.6906 0.6903 0.6624 0.6841
Ajeet Kumar, Mukesh Kumar, Yohannes Feyissa Beyisho and Vipul Kumar Sharma
http://www.iaeme.com/ijte/index.asp 14 [email protected]
Table 2 Density of nanofluids
S.No
Fluid
density(ρf)
Kg/m3
Density of
nanoparticles(ρp)
Kg/m3
Volume
fraction
(φ)
Density
of nanofluids(ρeff)
Kg/m3
Water
Al2O
3 CuO SiO2
TiO
2 Al2O3 CuO SiO2 TiO2
1 1000 3890 6310 2650 4230 0.01 0.6561 0.6561 0.6518 0.6551
2 1000 3890 6310 2650 4230 0.02 0.6622 0.6620 0.6536 0.6601
3 1000 3890 6310 2650 4230 0.03 0.6681 0.6679 0.6554 0.6651
4 1000 3890 6310 2650 4230 0.04 0.6739 0.6736 0.6571 0.6699
5 1000 3890 6310 2650 4230 0.05 0.6796 0.6793 0.6589 0.6747
6 1000 3890 6310 2650 4230 0.06 0.6851 0.6848 0.6607 0.6794
7 1000 3890 6310 2650 4230 0.07 0.6906 0.6903 0.6624 0.6841
Table 3 Convective heat transfer coefficient of nanofluids
S.No Volume
fraction
(φ)
Convective heat transfer coefficient(h)
(W/m2°C)
Rate of condensation (gram/ses-
meter)
Al2O3 CuO SiO2 TiO2 Al2O3 CuO SiO2 TiO2
1 0.01 10002.60 10119.55 9893.23 10007.66 5.91 5.98 5.84 5.91
2 0.02 10145.87 10373.04 9928.41 10154.21 5.99 6.13 5.86 6.00
3 0.03 10286.12 10621.77 9964.07 10299.45 6.07 6.27 5.88 6.08
4 0.04 10424.51 10863.74 9999.01 10441.13 6.16 6.42 5.90 6.17
5 0.05 10554.02 11094.24 10028.80 10574.57 6.23 6.55 5.92 6.24
6 0.06 10680.74 11318.59 10059.23 10705.89 6.31 6.68 5.94 6.32
7 0.07 10786.58 11517.69 10070.06 10815.83 6.37 6.80 5.95 6.39
4. RESULTS AND DISCUSSION
From mathematical analysis it was found that nanoparticle improves significantly physical
properties of fluids. When concentration of nanoparticle increases, thermal conductivity,
density, absolute viscosity and convective heat transfer coefficient of fluid increases. Because
of this improved properties condensation rate of fluid increases. Result is shown in below
figures.
Figure 2 Change of thermal conductivity of nanofluid with nanoparticle volume fraction
Condensation Rate Enhancement of Fluid in Steam Condenser by Mixing Nanoparticles
http://www.iaeme.com/ijte/index.asp 15 [email protected]
Figure 3 Density with change in volume fraction
Figure 4 Dynamic viscosity vs Volume fraction
Figure 5 Convective heat transfer vs Volume fraction
Ajeet Kumar, Mukesh Kumar, Yohannes Feyissa Beyisho and Vipul Kumar Sharma
http://www.iaeme.com/ijte/index.asp 16 [email protected]
Figure 6 Rate of condensation vs Volume fraction
Among all (Al2O3, CuO, SiO2 and TiO2), CuO is more effective. It shows good impact
on the on the physical properties of fluids.
According to Newton’s law cooling
Q = hA(Tsat-Ts)
So, size of heat exchanger can be reduced by increasing convective heat transfer
coefficient for the same heat rejection, and cost of heat exchanger can be decreased
significantly.
5. CONCLUSIONS
From the above result it is concluded that condensation rate of vapour fluid can be increased
by dispersing nanoparticle in fluid and it also depend on size of particle, material of particle
and volume fraction. And from the compact (low surface area by volume ratio) condenser
more condensation rate can be achieved. Enhancing the condensation rate by extending
surface is obsolete idea.
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