25 | P a g e

EXPERIMENTAL INVESTIGATIONS OF PULSATING

HEAT PIPE IN AUTOMOBILE RADIATOR WITH

ENTROPY GENERATION MINIMIZATION

Hathiwala K. A1, Dr. Vikas J. Patel

2, Patel H.M

3

1,2,3Mechanical Engineering Department, Gujarat Technological University,

S.V. Mandal Institute of Technology, Bharuch. (India)

ABSTRACT

Flow visualization was conducted for the close loop pulsating heat pipe using charged coupled device. It was

observed that during the start up period, the working fluids oscillates with large amplitude, however, at steady

operating state, the working fluid circulates. The direction of circulation for the working fluid is consistent once

circulation is attained, but direction of the circulation can be different for the experimental run. Phenomena

such as nucleation boiling, coalescence of bubbles, Formation of slug and propagation of inertia wave were

observed in the close loop pulsating Heat pipe. the finding shoe that the meandering Bends, uneven slug and

plug distribution and non-concurrent boiling at the evaporator contributed to the driving and restoring forces

For fluid circulation and oscillation.

I. INTRODUCTION

A heat pipe is a heat transfer mechanism that combines the principles of both thermal Conductivity and phase

transition to efficiently manage the transfer of heat between two solid interfaces. This type of heat pipe is

essentially a non-equilibrium heat transfer device. A heat pipe is a container tube filled with the working fluid.

Heat pipes are referred to as the semiconductors of heat due to their fast Transfer capability with low heat loss.

One end of this tube (called evaporator section) is brought in thermal contact with a hot point to be cooled. The

other end (called condenser section) is connected to the cold point where the heat can be dissipated. A portion of

the tube between evaporator and condenser is called adiabatic section. Number of PHP studies has been carried

out Since 1990s. Researchers agree that the oscillations are driven by an instability that appears due to coupling

of the adiabatic vapor compression and evaporation/condensation mass exchange. However this instability has

not been studied until recently. Such important parameters as oscillation threshold, heat transfer coefficient, and

maximum heat load cannot be predicted from calculations. It is not even clear whether the oscillations are

persistent or not and at which regimes. For these reasons the PHP applications are very limited. The PHP

parameters are adjusted empirically, often without any certainty.

To our knowledge, only a couple of small companies in the world produce them.

26 | P a g e

Fig 1 Pulsating Heat Pipe

II. LITERATURE REVIEW

A. Dimoudiet al [1] presented the cooling performance of a radiator based roof Component. Space cooling is

getting important in most countries and different techniques have been developed one of which is radiative

cooling. A prototype roof component, exploiting radiative cooling was built and tested in the outdoor test

facilities of the Centre of Renewable Energy Sources in Greece. He studied that radiator efficiency is drastically

reduced with increasing water flow rates. With increasing flow rates temperature difference between inlet and

outlet decreases and increases with decreases cooling flow rates.

A.K.A. Shati et al [2] presented the effect of surface roughness and emissivity on radiator output. The effect of

altering the emissivity and the roughness of a wall behind a radiator on the radiator heat output has been

studiedexperimentally and by using computational fluid dynamics. The results indicate that the presence of large

scale surface roughness and a high emissivity surface increases both the heat flow rate and the air velocity

behind the radiator compared to a smooth shiny surface. The surface roughness will increase both the surface

area for heat transfer and the turbulent intensity which increase the mass transfer and free convective heat flux

through the air gap. He studied that increasing the air gap will augment heat output and heat transfer rates.

Adnan M. Hussein [3] presented Heat transfer enhancement using nano fluids in an automotive cooling system.

Heat transfer enhancement using TiO2 and SiO2 nano powders suspended in pure water is presented. The test

setup includes a car radiator, and the effects on heat transfer enhancement under the operating conditions are

analyzed under laminar flow conditions. He studied that SiO2 nano fluid produces a higher heat transfer

enhancement than the TiO2 nano fluid; likewise, TiO2 nano fluid enhanced heat transfer more than pure water.

Ahmet Z. Sahin et al [4] presented Entropy generation in laminar fluid flow through circular pipes. Entropy

generation rate in a developing laminar viscous fluid flow in a circular pipe is analyzed.Theentropy

generationrate is higher near the wall and sharply decreases along the radius away from the surface of the pipe.

27 | P a g e

This is due to existing temperature and velocity gradient in this region. Around the centerline these gradients are

small and therefore the entropy generation is small.

Benjamin Siedel, Valérie Sartre et al [5] presented Numerical investigation of the thermo hydraulic behavior of

a complete loop heat pipe. He concluded that Heat losses to the ambient and through the transport lines are

considered. A low evaporation coefficient leads to a large increase of the LHP temperature.

C. Oliet, A. Oliva et al [6] presented parametric studies on automotive radiator. This work provides an overall

behavior report of automobile radiators working at usual range of operating conditions, while significant

knowledge-based design conclusions have also been reported. He studied that overall heat transfer coefficient

reveals almost independent of the air inlet temperature; but depend on coolant flow regime.Cooling capacity

increases with increasing coolant and air flow.Air inlet temperature increases both heat transfer & cooling

capacity decreases.Small fin spacing and higher louvered fin angles have higher heat transfer.

Ching-Ming Chiang et al [7] presented Theoretical study of oscillatory phenomena in a horizontal closed-loop

pulsating heat pipe with asymmetrical arrayed mini channel. He concluded that The dominant parameters

affecting the PHP dimensions of the flow channel, the number of turns, the filled liquid ratio, the frequency

ratio, the operating temperature and the temperature difference between the average evaporating region and the

average condensing region are investigated in this study. The closed-loop pulsating heat pipe with asymmetrical

arrayed mini channel with lower number of turns, lower filled liquid ratio, higher operating temperature and

higher temperature difference between the average evaporating region and the average condensing region for the

frequency ratio of unity could achieve a better performance due to larger oscillatory motions.

Cihat Arslanturk et al [8] presented Optimization of a central-heating radiator. An approximate analytical model

has been used to evaluate the optimum dimensions of a central heating radiator. The radiator problem is divided

into three one dimensional fin problems and then the temperature distributions within the fins and heat-transfer

rate from the radiator are obtained analytically. He studied that optimum radiator geometry maximizing the heat

transfer rate has been obtained by using the approximate analytical model.Increaseof radiator volume fraction

increases the maximum heat transfer rate and optimum tube diameter.

D. Yin, H. Rajab, et al [9] presented Theoretical analysis of maximum filling ratio in an oscillating heat pipe.A

maximum filling ratio to start up the oscillating motion can be found.maximum filling ratio is dependent on the

working fluids and the operation temperature.Pressure difference in the system is produced, which acts as an

exciting force to start up the movement of the liquid plugs and vapor bubbles in the OHP.

Dehao Xuet al [10] presented Thermo-hydrodynamics analysis of vapor–liquid two-phase flow in the flat-plate

pulsating heat pipe. He concluded that with the increasing heat load, the overall temperature level of the FP-PHP

increases, and the integral equivalent thermal resistance decreases.

Dong Liu et al [11] presented Flow and heat transfer performance of a mini channel

channel heat sinks have relatively low Nusselt number due to small Reynolds number. the friction factor of

mini-channel flow was larger than that of the macro channel flow due to larger surface roughness, and the

pressure drop caused by cylinder disturbed flow was less than 5%.he studied that Distributed flow has relatively

small effect on thermal resistance when velocity is slow. However the effects get stronger when velocity grows

larger.

Elsayed A.M. Elshafei et al [12] presented Experimental study of heat transfer in pulsating turbulent flow in a

pipe. He concluded that Observations of the local Nusselt number revealed that the heat transfer coefficient may

28 | P a g e

be increased or decreased, depending on the value of frequency and Reynolds number. Higher values of the

local heat transfer coefficient occurred in the entrance of the tested tube.

H. Khalkhali et al [13] presented Entropy generation in a heat pipe system. He concluded that Entropy

generation in a heat pipe can also be reduced by removing the insulation in the transport section. Both the

condenser ambient temperature and the convection heat transfer coincident in the transport section must be

adjusted to obtain a minimum entropy generation.To reduce the entropy generation in fluid flow evaporator

length should be as small as possible.

Himel Barua, et al [14] presented Effect of filling ratio on heat transfer characteristics and performance of a

closed loop pulsating heat pipe. He concluded that for water, both at lower and higher heat input, lower filling

ratio shows less thermal resistance and optimum heat transfer is obtained.

Huseyin Yapici, Gamze Basturk, Nesrin Kayatas et al [15] presented Numerical study on transient local entropy

generation in pulsating turbulent flow through an externally heated pipe.The author analyzed the entropy

generation in pulsating turbulent flow through a pipe for three different cases i.e. sinusoidal, step and saw down.

The effect of the period of the pulsating flow on the entropy generation investigated.The highest temperature

occurs in the step flow case. They also investigated that irreversibility due to the heat transfer dominates when

Bejan number is 1.With the increase of flow period, the highest levels of the total entropy generation rates

increase logarithmically in the case of sinusoidal and saw-down flow cases, whereas they do not almost change

in the step-flow case.

K.Y. Leong et al [16] presented Performance investigation of an automotive car radiator operated with nano

fluid-based coolants. Water and ethylene heat transfer fluids offer low thermal conductivity. With the

advancement of nano technology, the new generation of heat transfer fluids called, “nano fluids” have been

developed and Researchers found that these fluids offer higher thermal conductivity compared to that of

conventional coolants. He studied that Heat transfer rate is increased with increase in volume concentration of

nano particles.Volumetric flow rate of nano fluids is decreased with increase of volume fraction of copper nano

particles.

Manfred Grol et al [17] presented closed loop pulsating heat pipes: visualization and semi-empirical modeling.

He concluded that the study strongly indicates that design of these devices should aim leading to higher local

heat transfer coefficients.

Maziar Mohammad et al [18] presented Overall thermal performance of Ferro fluidic open loop pulsating heat

pipes: An experimental approach. He concluded that Ferro fluid improves the steady state thermal performance

of OLPHPs relative to distilled water charged ones under certain conditions. Higher concentrations of Ferro

fluid, reduces the steady state thermal performance of OLPHPs as a result of higher viscosity.

Mukherjee, et al [19] presented Second-law analysis of heat transfer in swirling Flow through a cylindrical

duct.They calculated the rate of entropy generation. They defined also a merit function and discussed influence

of swirling on this merit function.

N.Sahiti et al [20] presented Entropy generation minimization of a double-pipe pin fin heat exchanger. He

concluded that shorter flow length is accompanied with lower entropy production rates.It could be shown that

larger pin length sare accompanied with larger entropy production rates.

29 | P a g e

Nandan Saha et al [21] presented Influence of process variables on the hydrodynamics and performance of a

single loop pulsating heat pipe. He concluded that Different kinds of flow pattern have been observed and

transition of flow Pattern from oscillatory-slug to circulatory-annular .This transition is more likely in case of

low FR due to a larger degree of freedom. There exists a minimum start-up power or threshold power below

which no movement of fluid is observed inside CLPHP.Best performance of the loop was found to occur at an

inclination angle lower than 90.

O.M. Haddad et al [22] presented Entropy generation due to laminar forced convection in the entrance region of

a concentric annulus. He concluded that the total entropy generation decreases with the increase in Reynolds

number. The total Entropy generation decreases as the dimensionless entrance temperature increases.Increasing

the annulus radius ratio increases the entropy generation.

Piyanun Charoensawan et al [23] presented closed loop pulsating heat pipes: parametric experimental

investigations. He concluded that the internal diameter of the tubes tested in the present study, as governed by

the critical Bond number is well within the specified limit, bubble shapes are affected by the buoyancy forces. A

certain critical number of turns are required to make horizontal operation possible and also to bridge the

performance gap between vertical and horizontal operation.

Roger R. Riehl, Nadjara do Santoset al [24] presented Water-copper nano fluid application in an open loop

pulsating heat pipe. He concluded that with copper nano fluid, the pulsation was better visualized. Greater

amplitudes on the pulsations could be observed with the nanofluid. The presence of solid nano particles in the

working to increase the nucleation sites necessary for bubble formation.

S.M.Peyghambarh et al [25] presented Experimental study of heat transfer enhancement using water/ethylene

glycol based nano fluids as a new coolant for car radiators. Heat transfer performance of pure water and pure

EG has been compared with their binary mixtures. Different amounts of Al2O3 nano particle have been added

into these base fluids and its effects on the heat transfer performance of the car radiator have been determined

experimentally. The heat transfer enhancement of about 40% compared to the base fluids has been recorded. He

studied that with increasing the nano particles increase heat transfer rates and heat transfer coefficient.

Additionof nano particles to the coolant has the potential to improve automotive and heavy duty engine cooling

rates or equally causes to remove the engine heat with a reduced size cooling system.

Seyfolah Saedodin et al [26] presented Analysis of Entropy Generation Minimization in Circular Porous Fins. In

porous fins, with increase of porosity, the entropy generation number will increase. Increased porosity the

entropy generation will decrease.Increased that porosity the entropy generation will decrease. Also with the

increase of Reynolds number, the values of entropy generation at all them will increase.

Todd A. Jankowski et al [27] presented Minimizing entropy generation in internal flows by adjusting the shape

of the cross section. In adiabatic flow, the circular cross section will minimize flow resistance, which is reflected

by a minimization of the entropy generation. A Duct with a large wetted perimeter will increase the surface area

available for heat transfer and will minimize the overall entropy generation.When the available cross-sectional

area of the flow channel is doubled, the resistance to flow in the duct is reduced, thereby reducing the entropy

generation associated with fluid friction. Using larger perimeter compare to cross section area entropy

generation is minimized.

Tsuyoshi et al [28] presented Numerical and experimental studies on circulation of working fluid in liquid

droplet radiator. Model of the circulation of the working fluid in a liquid droplet radiator has been developed.

30 | P a g e

The behavior of the circulation of the working fluid calculated from the model is compared with that obtained

from experiments in the case that the flow rate of the circulating working fluid is changed. He studied that as

flow rates decreases with time pressure difference in working fluid increased and this phenomena can be

improved by adjusting number of revolution in gear pump used in model.

Xuefeng Wang, et al [29] presented Numerical analysis of heat transfer in pulsating turbulent flow in a pipe.The

model analysis shows that Womersley number is an important parameter in the study of pulsating flow and heat

transfer.Higher the womersely number benefits to heat transfer enhancement only in entrance region. It indicates

that larger velocity induced by pulsation of the fluid flow results in higher heat transfer rate.

Yuwen Zhang, et al [30] presented Oscillatory Flow in Pulsating Heat Pipes with Arbitrary Numbers of Turns.

He concluded that increase in the number of turns has no effect on the amplitude and circular frequency of

oscillation when the number of turn’s water, functional thermal fluids (FS-39E microcapsule fluid and Al2O3

nano-fluid) as working fluid in PHP can enhance its heat-transport capability. Like FS-39E microcapsule fluid,

Al2O3 nano-fluid as working fluid can enhance heat-transport capability of PHP.the best concentration of

Al2O3 nano-fluid is 0.1 wt%.

III EXPERIMENTAL SET UP

FIG 3.1 Experimental Set Up

3.1 Working Fluid

The selection of the working fluid used in pulsating heat pipes is dependent on a number of variables. The

approximate temperature range the system will be exposed to be the most critical in determining the proper

working fluid. Using an approximate temperature range of 50 to 150 degrees Celsius in turn means many

potential working fluids are possible options. Additional requirements need to be examined as well and are

listed below:

Thermal stability

Wet-ability

Reasonable vapor pressure

Compatibility with heat pipe materials

High thermal conductivity and latent heat

Reasonable freezing point

31 | P a g e

Low vapor and liquid viscosity

For this experiment and various other experiments involving pulsating and oscillating heat pipes, distilled water

is used as the working fluid. Water was chosen for its thermodynamic attributes that make it more appealing

than others, such as methanol. It has a high latent heat of vaporization of 2260 kJ/kg which has the potential to

spread significantly more heat with less fluid flow. Latent heat is defined as the heat required converting a solid

into a liquid or vapor, or a liquid into a vapor, without a change in temperature.

IV. PHP DESIGN

The PHP performance data (for pure and binary mixture of working fluid) were obtained according to the

following procedure: Heat input was stepwise increased until a quasi thermal equilibrium was established. Then,

the spatial temperatures and heat input were recorded, so the thermal resistances could be determined. The

thermal resistance is defined by

Where, Teand Tc are the average evaporator and condenser surface temperatures, which is the average of three

temperatures, Calculated by using Equation

Ti=

Where i= e or c

Q is heat input power to PHP. Thermal heat loss Q can be determined by Q = P - Qloss where, P is the input

electrical power Qloss is the heat loss, which was verified to be about 4% to 9%, depending on the heat load.

The heat transfer capacity of a typical pulsating heat pipe can be calculated using equation

Where T is the overall temperature difference along the heat pipe; and are the effective thermal conductivity

and length, and is the cross sectional area of the pulsating heat pipe.

Fig. 4.1 Pressure Enthalpy (P-h) Diagram of a Pulsating Heat Pipe

32 | P a g e

Pulsating heat pipe that is properly designed and constructed should experience little thermal contact resistance.

The conductive thermal resistance in the wall can also be considered negligible. The contact and conductive

resistances are independent of the heat pipe operating temperatures, and because of this the thermal resistances

due to the evaporation in the evaporator, Revp Two-phase flow along the heat pipe, Rl-v and the condensation in

the condenser, Rcond are, however, significant to the performance of the heat pipe.

Fig. 4.2Thermal Resistance Schematic of a Typical Pulsating Heat Pipe

Typically during operation of the PHP, a continuous flow boiling associated with strong bubble growth and

water slug flow takes place in the evaporator section of the heat pipe. The two phase flow continues its way

towards the heat pipe condenser section where the bubbles collapse and condense while giving up their latent

heat of vaporization. The vapor-liquid thermal resistance through the length of the pulsating heat pipe is a

function of the temperature and pressure drop from the evaporator to theCondenser. Typical pulsating heat pipes

in previous studies have shown small thermalResistances, ranging from (3.29x104 /A)/°C/W and (2.10 x 10-

3/A) /°C/W. Figure zooms on a typical liquid-vapor plug system as formed in the PHP and suggests the various

forces, heat and mass transfer processes. The analysis of the control volume on a micro scale will manifest much

more complicated molecular forces and heat and mass transfer processes than what has been depicted in Figure

4.3 Such a system will be mathematically too complicated and impractical

V. RESULT AND DISUSSION

As fig 4.1 & 4.2 shows an effect of thermal resistance on pulsating heat pipe. It shows that as heat input

increases thermal resistance of pipe decreases. Effect of thermal resistance on PHP and different filling ratio is

also shown. We also observed effect of filling ratio on PHP. We also found that as filling ratio increases thermal

resistance of PHP decreases. So thermal resistance decreases for a given heat input and filling ratio. We also

determine effect of diameter on pulsating heat pipe. So optimal filling ratio is found to be 70% for pulsating

heat pipe.

33 | P a g e

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

100 200 300 400 500

Th

erm

al R

esis

tan

ce(°

C/W

) 4mm

Diameter

2mm

Diameter

Heat Load (W)

FIG 4.1 Thermal Resistance vs Heat Load

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

100 200 300 400 500

Th

erm

al

Res

ista

nce

(°C

/W)

F.R

40%

F.R70

%

FIG 4.2 Thermal Resistance vs Heat Load

Major reasons of entropy generation in pulsating heat pipe are: due to temperature difference and fluid with a

friction. We determine entropy generation in pulsating heat pipe a two different diameter and filling ratio. We

found that as temperature increases, entropy generation increases. Minimum entropy generation number means

minimum entropy generation .we found that as temperature increases entropy generation number decreases and

at certain point minimum entropy generation number is found and then increases entropy generation number. So

it means minimum entropy generation number is minimum entropy generation in pipe.

34 | P a g e

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

369 371 369 372 372En

trop

y G

ener

ati

on

(W

/°K

)

4mm

Diameter

2mm

Diameter

Te ( K)

Fig 4.3 Entropy Generation vs T e

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

0.16

369 371 369 372 372

En

trop

y G

ener

ati

on

(W

/°K

)

F.R 40%

F.R 70%

T e ( K)

Fig 4.4 Entropy Generation vs T e

35 | P a g e

0

20

40

60

80

100

120

140

160

180

369 371 369 372 372

Ns (S

gen

/Sg

en,m

in )

F.R

40%

F.R

70%

Te ( K)

Fig 4.5Ns vs T e

020406080

100120140160180

369 371 369 372 372

Ns

(Sg

en/S

gen

,min

)

4mm

Diameter

2mm

Diameter

Te ( K)

Fig 4.6 Ns vs Te

VI. CONCLUSION

We found that as heat input increases thermal resistance decreases for both 40% and 70% filling ratio. Thermal

resistance also decreases for both 2mm and 4mm diameter. A optimal filling ratio is found to be 40%. A better

pulsation can be observed in 2mm diameter. We found that as temperature increases entropy generation rate

increases. Minimization of entropy depends on entropy generation number.Minimum entropy generation

number found at 372K .So minimum entropy is generated at that particular point.

36 | P a g e

REFERENCES

[1]. A.Dimoud, Androutsopoos.(2006).perormance of a radiator based roof Component.Solar Energy.

[2]. A.K.A. Shati, S.G. Blakey,S.B.M. Beck .,(2011)The effect of surface roughness and emissivity on

radiator output. Energy & Buildings.

[3]. Adnan M. Hussein, R.A.Bakar,K. Kadirgama,K.V. Sharma.(2014) Heat transfer enhancement using

nano Fluids in an automotive cooling system. International Communications in Heat and Mass Transfer.

[4]. Ahmet Z. Sahin and Rached Ben-Mansour.,(2003).Entropy generation in laminar fluid flow through

circular pipes. ISSN 1099-4300, Entropy.

[5]. Benjamin Siedel, Valérie Sartre (2013). Numerical investigation of the thermo hydraulic behavior of a

complete loop heat pipe. Applied Thermal Engineering.

[6]. C. Oliet, A. Oliva,J. Castro, C.D. Pe´rezSegarra.(2007).parametric studies on automotive radiator.

Applied Thermal Engineering.

[7]. Ching-Ming Chiang, Han MingChen,Chi ChuanWang.,(2012). theoretical Study of Oscillatory

phenomena in a Horizontal closed loop pulsating heat Pipe with a symmetrical arrayed mini

Channel.International Communications

[8]. Cihat Arslanturk,A. Feridun Ozguc, (2006) Optimization of a central Heating Radiator.Applied Energy.

A.K.A. Shati,S.G. Blakey,S.B.M. Beck. (2011). effect of surfaceRoughness and emissivity on radiator

Output.Energy and Buildings.

[9]. D. Yin,H. Rajab, H.B. Maa.,(2014). Theoretical analysis of maximum filling ratio in an oscillating heat

pipe.International Journal of Heat and Mass Transfer.

[10]. Dehao Xuet, Taofei Chen, Yimin Xuan., Thermo hydro dynamics analysis of Vapor Liquid two- phase

flow in the flat plate pulsating heat pipe.International Communications in Heat And Mass Transfer.

[11]. Dong Liu, Minghou Liu,Dan Xing Sheng Xu., (2011). Flow and heat transfer performance of a mini

channel Radiator with cylinder disturbed flow. Experimental Thermal and Fluid Science.

[12]. Elsayed A.M. Elshafei, M. SafwatMohamed, H. H. Mansour, M. Sakr., (2008). Experimental study of

heat Transfer in pulsating turbulent flow in a Pipe. International Journal of Heat and Fluid Flow.

[13]. H. Khalkhali,A. Faghri,Z.J. Zuo., (1999) Entropy generation in a heat pipe System.Applied Thermal

Engineering.

[14]. Himel Barua, MohammadAli, Mdnuruzzaman, M. Quamrul Islam, chowdhury M. Feroz., (2013). Effect

of filling ratio on heat transfer characteristics and performance of a closed loop pulsating heat pipe.

Procedia Engineering.

[15]. Huseyin Yapici, Gamze,Batyrk, Nesrin Kayatas, And Senay Yalcin .,(2005).Numerical study on

transient local entropy generation in pulsating turbulent flow through an externally heated pipe. Vol. 30,

Part 5, October 2005, pp.

[16]. K.Y. Leong,R. Saidur,S.N. Kazi, A.H. Mamun., (2010). Performance Investigation Of an automotive

carRadiator operated with nano fluid based Coolants.Applied Thermal Engineering.

37 | P a g e

[17]. Maziar Mohammad,Hossein AfshinMohammad Hassan Saidi, Mohammad Behshad Shafii., (2013).

Overall thermal Performance of Ferro fluidic open loop Pulsating heat pipes: An experimental

Approach. International Journal of Thermal Sciences.

[18]. Mukherjee, P.; Biswas, G.; Nag, P.K.,(1987).Second law analysis of heat transfer in swirling Flow

through a cylindrical duct.ASME Journal of Heat Transfer.

[19]. N.Sahiti,F.Krasniqi,X.Fejzullahu, J.Bunjaku,A. Muriqi.,(2008). Entropy generation minimization of a

Double pipe pin fin heat exchanger. Applied Thermal Engineering.

[20]. Nandan Saha,P.K Das.,(2014). Influence of process variables on the hydro dynamics and performance

of a single loop pulsating heat pipe. International Journal of Heatand mass Transfer.

[21]. O.M. Haddad, M.K. Alkam, M.T. Khasawneh., (2004). Entropy Generation due to laminar forced

convection in the entrance region of a concentric annulus. Energy.

[22]. Piyanun Charoensawan, Sameer Khandekar, Manfred Groll., (2003) closed loop pulsating heat pipes:

Parametric experimental investigation. Applied Thermal Engineering.

[23]. Roger R. Riehl, Nadjara do Santoset. (2012).Water-copper nano Application in an open loop pulsating

Heat pipe.Applied Thermal Engineering.

[24]. S.M.Peyghambarh, S.H. Hashemabadi S.M.Hoseini,M. Seifi Jamnani.,(2011) Experimental study of

heat transfer Enhancement using water/ethylene Glycol based nano fluids as a new Coolant for car

radiators.

[25]. Sameer Khandekar,Piyanun Charoen Sawn, Manfred Groll,Pradit Terdtoon. (2003). Closed loop

pulsating heat Visualization and semi empirical Modeling.Applied Thermal Engineering.

[26]. Seyfolah Saedodin,Siamak Sadeghi., (2012). Analysis of Entropy generation Minimization in Circular

Porous Fins.ISRN Chemical Engineering Volume.

[27]. ToddA.Jankowski.,(2009).minimizi Entropy generation in internal flows by Adjusting the shape of the

cross section.International Journal of Heat and Mass Transfer.

[28]. Tsuyoshi Totani,Takuya Kodama, Kota Nanbu,Harunori Nagata, Isao Kudo.(2006). Numerical and

Experimental studies on circulation of Working fluid in liquid droplet radiator.

[29]. Xuefeng Wang, Nengli Zhang.,(2005).Numerical analysis of heat transfer in pulsating turbulent flow in

a pipe.International Journal of Heat and Mass Transfer.

[30]. Yuwen Zhang, Amir Faghri., (2003). Oscillatory Flow in Pulsating Heat Pipe with arbitrary Number of

turns. Journal of thermo physics and heat Transfer.