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COMPARISON OF NANO FLUIDS WITH OTHER COOLANT IN RADIATOR HEAT TRANSFER
Abstract— There were many coolants which were used conventionally such as water and ethylene glycol in the radiator but having the downside of having a low thermal conductivity was a big block and obligation in achieving a better efficiency. But addition of a small amount of nanoparticles with these coolants was providing some good results. Some of the examples of these were copper nanoparticles based ethylene glycol which was showing positive results and along with this also is evident for the reduction in frontal area of the vehicle. An advancement of 3.8% heat transfer was record when 2% nanoparticles were added in ethylene glycol. An increase in heat transfer coefficient was recorded when nanoparticles of Copper Oxide were added in the coolant of ethylene glycol and water. In the best conditions an increase of 55% in heat transfer coefficient was achieved. Positive results were achieved when nanoparticles of Titanium Oxide were added in the base fluid where 3% increase in thermal conductivity was recorded and along with this 10% increase in convective heat transfer was recorded when 1% weight of nanoparticles were added in the base fluids. Nanofluids properties and empirical correlations were used to investigate the effect of the nanoparticles.
Cooling system of vehicle is smart edge technology. It affects the overall efficiency of vehicle along with the weight and size of vehicle. If cooling system is week it doesn’t cool off engine or it is big enough it make the vehicle heavier which will affect the efficiency of vehicle. By using nanofluids, the size of this cooling system such as radiator, pump can be effectively reduced. The radiator can be make lighter and shorter which affect the size of vehicle along with efficiency. Argon researchers, Singh have determine that the use of high-thermal conductive nanofluids in radiators can lead to reduction in the frontal area of the radiator by up to 10% , This reduction in aerodynamic drag can lead to fuel saving up to 5%. The application of nanofluids also contributed to reduction of friction and wear and tear, reducing parasitic losses, operation of components such as pumps and compressors, and subsequently leads more than 6% of fuel saving. In this project, there will be comparison of the nanofluids with other coolant which are used in radiators.
The demand for high efficiency engines has been increased day by day because of continuous technological development in automotive industries. The aspects like Radiator, Charge air cooler, thermal management system, can be very helpful in determining the efficiency of the vehicle. The efficient engine depends on its performance, better fuel economy and less emissions. Overcoming, the problem of wind resistance, the manufacturers must consider some steps which will result in improving the aerodynamic design of vehicle. About 65% of total energy output of vehicle at high speed gets wasted to compensate the aerodynamic drag. This result due to large size of radiator whose function is to optimize the cooling effect of the incoming air.
Radiator is a part of cooling system. Cooling system in the engine plays important role. It carries heat waste from engine to surroundings. It cools down the engine and protects the vehicle from any damage. Traditionally, we focus only on the rate of cooling which has reached its limit. Now focus is on the properties of the coolant. Ethylene Glycol and water are widely used coolant in automobile industry. These are readily available and work well in achieving the cooling of the vehicle. The use of nanofluids will be a stepping stone in achieving the cooling at a faster which will lower the amount of heat or energy wasted. Moreover, it will result in the decrease in the size and weight of the radiator which will ultimately have a positive effect on the performance of the vehicle.
Some researches had proved that the nanofluids enhance the heat transfer of the system. With carefully selecting the material, size, shape, base fluid type, nanofluids will perform better than conventional water coolant. Al2O3/ water Oxide and aqueous Ti2O are one such example of nanofluids. There are many benefits of nanofluids. Some of them are high specific surface area which helps in transfer surface between particles and fluids, high dispersion stability. It also help in reducing the pump power and size, reduce particle clogging and has adjustable properties, including thermal conductivity.
Steve Choi  one of the researchers has improves the vehicle cooling system efficiency through nanofluids. The field of Nanofluids and nanoparticles are the new type of suspensions, which are dispersed into nanometer size solid particles in heat transfer fluids for better heat thermal conductivity. After production of nanofluids it was discovered that nanofluids have a much higher temperature dependent thermal conductivity at low particle concentrations than conventional radiator coolants without nanoparticles . Various researches has demonstrated that nanofluids have significantly better heat transfer properties than the base fluids. Nanofluids are promising future coolants for the transportation industry.
Nanofluids in enhancing thermal conductivity
Eastman  found that the thermal conductivity of ethylene glycol containing 3% of copper particles can be enhanced up to 30-40% compared to that of ethylene glycol base nanofluid. They obtained about 27% enhancement of thermal conductivity by adding 4% volume fraction of zinc dioxide nanoparticles in ethylene glycol. Present study concluded that size of nanoparticles and viscosity of the nanofluids played a vital role in thermal conductivity enhancement ratio of them.
Researcher named Milta found the effect of temperature, particle size and volume fraction on thermal conductivity of water based nanofluids of copper oxide and alumina. Many have suggested that thermal characteristics can be enhanced with increase of nanoparticles volume fraction, temperature and particle size. Authors found that the smaller the particle size, the greater the effective thermal conductivity of the nanofluids at the same volume fraction. Contact surface area of particles with fluid and Brownian motion can be increased when smaller particles are used in the same volume fraction. This consequently increased thermal conductivity of nanofluids. 
Challenges of Nanofluids
There are always strong van-der Waals interactions in the nanoparticles and due to this preparing a homogenous suspension is a big challenge.
The price of the nanofluids is also a challenge as it will get very expensive if they will be used in a greater scale.
Long term stability is also a concern as a study reveals that there is decrease in thermal conductivity with time of ethylene glycol containing 0.3% copper nanoparticles.
The specific heat of the nanofluids is less as compared to the base fluids. A coolant which possesses high specific heat results in achieving better cooling. 
II. Objectives and Problem Statement
To increase the cooling effect achieved by the radiator if we will use nanofluids and to achieve greater horsepower.
To decrease the size and weight of the radiator.
To achieve better stability of nanofluids for a long term.
To compare and analyze the heat transfer of radiator with nanofluids and other coolants
We were basically comparing the effectiveness of different coolants in the radiators. We went through a lot of examples by surfing the internet. It was clearly evident that the choice of coolants is a vital part in improving the efficiency of the automobile as it is the first and most usual demand of any customer that the vehicle should be a good investment and it should not be a big hassle for them. So as per time passed we went through how car manufacturers were using different coolants and were very concerned about their effectiveness as well. Fluids such as water and ethylene glycol and so on were used conventionally for heat transfer. But as per the advancement of technology and now we are dealing with the nanotechnology, and moreover based on their positive repercussions, car companies had to definitely use this with the above mentioned coolants. By adding nanoparticles such as magnesium oxide and Aluminum oxide and in specific concentration. We went through a number of reports published in which comparisons with added nanoparticles and without the nanoparticles were recorded. Mathematical correlations were there in the reports which performance of the radiators was recorded with added nanoparticles with the coolants. Approach was also to consider all the other factors such as shape of the tubes for maximum heat transfer such as in most of the experiments flat tubes were used. Various assumptions were also made as the real scenarios can differ in many ways. So there were a set of rules for the effectiveness of the experimental study as follows.
To study where exactly the traditional method is not providing us with the better results and how can we use the nanofluids specifically in what proportion by volume and which nanoparticles should be included to achieve better efficiency.
To collaborate various studies and to know the behavior of fluids in different conditions and surrounding.
To study the chemical reactions in the process and how stability for a longer time can be achieved.
To analyze the heat transfer rate of different coolant along with nanofluids with help of their thermal conductivity along with the scientific calculation based on their on their heat transfer coefficient. This study will includes some graphs along with data comparison of different fluid
If First step include the preparation of nanofluids.
Preparation of nanofluid
In this method, we usually user oxide nanoparticles where they are dispersed in the base fluid for the desired nanofluid. There is one disadvantage of this method. The nanoparticles get agglomerated due to attractive Van der waals forces between the particles. 
Second way is by dispersing the nanoparticles. This can be done by direct evaporation of the nanoparticles in metal form. Then began the condensation of the nanoparticles into the liquid. The main disadvantage of this method is low amount of production capacity, concentration of nanoparticles. It also has a high coast associate with this method. This technique didn’t have the disadvantage of nanoparticles agglomeration or it is minimized to certain extent. The suspensions obtained by either case should be well mixed, uniformly dispersed and stable in time. The heat transfer properties of nanofluids could be controlled by the concentration of the nanoparticles and by the shape of nanoparticles. 
With smaller the size come with the greater stability of colloidal dispersion, with greater stability of colloidal dispersion the greater would be probability of interaction and collision among particles. The collision among particles and fluid and the greater the effective heat energy transport inside the liquid (Xue 2003).Thermal conductivity enhancement ratio 
(Keffective = Knanofluid / Kbasefluid)
In this analysis we are using Aluminum oxide (Al2O3) as the nanofluid coolant. The volume density and fraction of Aluminum oxide in given suspension is defined by the given equation.
Mass of the nanoparticles required for 1l of nanofluids is given as
Data needed was taken from the literature for analysis in this study. The radiator data needed for this study is taken from the Vasu  and kays and London  as shown in table. 1 and 2. This compact heat exchanger consists of 644 brass flat tubes and 346 continuous copper fins. Compact heat exchanger is a unique and special class of heat exchanger having a large heat transfer area per unit volume. In addition, flat tubes are more popular in automotive applications due to the lower drag profile compared to round tubes These two features will enhance the cooling rate and at the same time minimizing the flow resistance. It is a cross-flow compact heat exchanger with unmixed air and fluid as coolants.
Flat tube radiator and its dimension from S.M. Peyghambarzadeh /International Communications in Heat and Mass Transfer 38 (2011)
The mathematical equations are taken from the reference [7, 9, 10, 11, and 12]. These equations show the comparison of nanofluid coolants to other coolants such as ethylene glycol. It shows the heat transfer rate for nanofluids and other coolant in the radiator. Thermal performance can be calculated using this equation.
Core geometry of flat tube heat exchanger from V. Vasu
Characteristics of heat exchanger from D.G chruluya
international journal of heat and fluid flow 30 (2009) /SH Noie
Relevant data is shown in these tables for the theoretical calculation for finding the thermal performance of radiator.
Heat transfer coefficient can be expressed by
Is obtained from Eastman where,
were calculated based on correlations obtain from Tsai and Chein.
Heat capacity rate, Cnf can be expressed as
Total heat transfer coefficient, where wall resistance and fouling factors are neglected.
This is done on the specification of radiator from above table. There are some condition for this test and can be explained below.
(a) The Reynolds number was taken constant for coolant. The concentration for nanoparticles is 0.3%. The Prandtl and Nusselt number are then calculated.
(b) Analysis includes the thermal comparison of thermal performance of radiator with nanofluids.
V. Results and Discussions
Effect of nanoparticles to thermal performance
In this study, Dynamic viscosity of nanofluid has been calculated using the correlation with nanoparticles. It is explained by equation
From where we can calculate the value of Gnf.
The coolant mass flow rate can be calculated using following equation.
From this equation we can find Wnf
Volume flow rate of nanofluids is decreased with increase of volume fraction of nanoparticles and prandtl number also decreases. Prandtl number can be calculated using the eq. (8)
TITANIUM OXIDE BASED COOLANT
When we will use the nanoparticles of Titanium Oxide in the coolant instead of going with only the equal solution of Ethylene glycol and water, we have seen the exit engine coolant temperature increase by about more than double. Moreover, the effectiveness if the radiator was 29% with distilled water as compared to 51% using nanoparticles of Titanium oxide with water.
The thermal conductivity of Titanium oxide nanoparticles is 11.8W/mK as compared to the conventional coolant( Ethylene glycol and water) which is only 0.3745.
ALUMINUM OXIDE BASED COOLANT
At the concentration of 1% by volume of nanoparticles of Aluminium oxide, heat transfer increased by 40% as compared to pure water.
It was found due to addition of Al2O3 nanoparticles only by volume fraction 0.2% in the water/MEG base fluid (50:50 by volume) the thermal conductivity enhancement was 0.63%-, Viscosity increase by 24.52% which causes heat transfer enhancement approximately 30% for 8.82LPM coolant flow rate. Peyghambarzadeh  also found the 40% enhancement in EG based Al2O3 nanofluids with approximately 4% variation in Thermal conductivity. For less than 15% enhancement in conductivity water based
Al2O3 nanofluids Heris [15, 16] also found 40% enhancement in heat transfer.
It is not the thermal conductivity which is responsible for more heat transfer but instead it is the Brownian motion of the nanoparticles.
Ethylene glycol/ water
Table3 comparison of thermal conductivity of Water, EG and TiO 
The use of nanoparticles helps in increasing thermal conductivity than normal coolant but effectiveness depends on the ratio of the nanoparticles as increasing more than a specific amount of these will result in increment of dynamic viscosity which will ultimately affects heat transfer.
One more result of the studies undergone is that when it comes to anti freezing capabilities of the coolant, nanoparticles are only effective if they are used in the cold weather. As if we will use the mixture in hot areas or in summers, it will decrease in heat rejection.
The effectiveness of radiator is also very important as the combination of both the radiator and mixture of nanoparticles and the coolants will ultimately provide us the best results.If we are able to increase the pressure drop, we will be able to increase the concentration of copper nanoparticles for even better results.
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