report on solar collector

8/11/2019 Report on Solar Collector

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CERTIFICATE

It is certified that the work contained in the project report entitled USE OF NANO

COLLOIDAL DISPERSION FOR SOLAR ENERGY RECOVERY" has been carried out by

Anamika Sinha during the period of project training from 20th

May 2014 to 14th

July 2014

under my supervision and guidance at R&D and Scientific Services, TATA STEEL,

Jamshedpur. She has completed her project successfully. Without prior approval of Tata Steel

Ltd. no data/information should be shared with any other agency or no communication should

be there in any journal/ patent body.

Mr. Tapan Kumar Rout

14th

July, 2014


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ACKNOWLEDGEMENT

I wish to express my deepest gratitude to my guide Mr Tapan Kumar Rout, Manager, R&D

department, TATA STEEL Ltd. for his invaluable guidance, excellent supervision and

constant inspiration throughout this project work. His encouragement and advice kept me

motivated and ensured a timely completion of my project.I would also like to thank all the

members of MMPD/OSP Lab, Scientific Services, Tata Steel for their constant support and

coordination without which, this project would not have been a success.

I would also like to extend my sincere gratitude to Mr Anup ----, MMPD/ OSP Lab,

Scientific Services, TATA STEEL Ltd., for his constant support during the course of my

project.

I thank once again all other people, who were directly or indirectly involved to complete myproject successfully.

Anamika Sinha

VT 20142553


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ABSTRACT

Solar energy radiant light and heat from the sun, is being harnessed using severaltechnologies such solar collector, solar cells, solar architecture, etc.

Solar collector is a device for capturing solar radiation. Conventional solar collector used

water as a coolant inside tubes to transfer heat. Efficiency of these collectors is limited by

absorption properties of the working fluid. Conventional solar collectors are available with

poor efficiency and high cost. Mixing nano-particles in a liquid increases its thermal

conductivity. Nanoparticles also improve the radiative properties of liquid improving the

efficiency of solar collector.

Aim of our project is to study about nanoparticles and their dispersion in water in order toincrease the heat absorbing capacity of working fluid in solar collector and also to design a

suitable model of solar collector.


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CONTENTS

Page no

1. INTRODUCTION----------------------------------------------------------------------------6

2. STUDY OF NANOPARTICLES FOR SOLAR ENERGY RECOVERY ------- 7-11

2.1. ABSORBING CAPACITY OF DIFFERENT NANOFLUID--------------------7

2.2. THERMO-PHYSICAL PROPERTIES OF NANOFLUID------------------------8

2.3. CURRENT RESEARCH---------------------------------------------------------------8

3. SOLAR COLLECTOR DESCRIPTION------------------------------------------------11-17

3.1. HEAT PIPE------------------------------------------------------------------------------12

3.2.STUDY OF FLAT PLATE COLLECTOR USING HEAT PIPE--------------- 14

3.3.PROPOSED DESIGN OF SOLAR COLLECTOR---------------------------------15

3.4.EFFECT OF L/di RATIO ON EFFICIENCY---------------------------------------16

3.5.EFFECT OF Le/Lc RATIO------------------------------------------------------------17

4. THERMAL ANALYSIS------------------------------------------------------------------17-22

5.

PREPARATION OF CARBON BLACK NANOFLUID------------------------------22

6. EXPERIMENTAL RESULT-------------------------------------------------------------23-26

7. DISCUSSION ON RESULT---------------------------------------------------------------27

8. CONCLUSION------------------------------------------------------------------------------27

9. REFERENCE--------------------------------------------------------------------------------28


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1.INTRODUCTION

Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient

times using a range of ever evolving technologies. Of all the sources of renewable energy

especially solar energy has the greatest potential when other sources in the country havedepleted. Because of the desirable environmental and safety aspects it is widely believed that

solar energy should be utilized instead of other alternative energy forms, even when the costs

involved are slightly higher. Solar energy technologies include solar heating, solar

photovoltaics, solar thermal electricity and solar architecture, which can make considerable

contributions to solving some of the most urgent problems the world now faces. Solar

technologies are broadly characterized as either passive solar or active solar depending on the

way they capture, convert and distribute solar energy. Active solar techniques include the use

of photovoltaic panels and solar thermal collectors to harness the energy.

Solar collector is a device used for absorbing solar energy. It consists of basically three parts,

a transparent cover, tubes carrying coolants and back plate. Solar radiant incident upon the

transparent surface of the solar collector is transmitted through this surface. The inside of the

solar collector is evacuated and trapped solar energy inside is used to heat the coolant

contained within the tubes. The back plate is black painted to absorb solar radiation. The

solar collector is insulated to avoid heat loss. The solar collector box is usually made up of

wooden frame.

Conventional solar collector uses water as a coolant inside the tube which has poor efficiency

and high cost. Instead of using water we can use nanofluid which has high thermal

conductivity and thus helps in increasing the efficiency of solar collector. Nanoparticles such

as graphite, copper, silver and carbon nanotubes increase the thermal conductivity of workingfluid in achieving efficiency improvements upto 5%.


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1.STUDY OF NANOPARTICLES FOR SOLAR ENERGY

RECOVERY

There are so many methods introduced to increase the efficiency of the solar water heater

(Xiaowu and Hua, 2005; Xuesheng et al., 2005; Ho and Chen, 2006; Hussain, 2006). But the

novel approach is to introduce the nanofluids in solar water heater instead of conventional

heat transfer fluids (like water). The poor heat transfer properties of these conventional fluids

compared to most solids are the primary obstacle to the high compactness and effectiveness

of the system. The essential initiative is to seek the solid particles having thermal

conductivity of several hundred times higher than those of conventional fluids. An innovative

idea is to suspend ultra fine solid particles in the fluid for improving the thermal conductivity

of the fluid by Hetsroni and Rozenblit (1994). These early studies, however, used suspensions

of millimeter- or micrometer-sized particles, which, although showed some enhancement,

experienced problems such as poor suspension stability and hence channel clogging, which

are particularly serious for systems using mini sized and micro sized particles. The suspendedmetallic or nonmetallic nanoparticles change the transport properties and heat transfer

characteristics of the base fluid. Hwang et al. (2007) studied the stability and thermalconductivity characteristics of nanofluids. In this study, they concluded that the thermal

conductivity of ethylene glycol was increased by 30%.Nanofluid is a new class of heat transfer fluids containing stably suspended nano-sized

particles, fibers, or tubes in the conventional heat transfer fluids such as water, ethylene

glycol, etc. When nanofluids are used as working fluids of the direct solar absorbers, the

thermal properties of nanofluids are critical to the solar utilization. Photothermal property is

very important to the assessment of solar energy absorption of nanofluids because it directly

reflects the solar absorption ability of nanofluids. Viscosity and rheological behaviors not

only are essential parameters for nanofluid stability and flow behaviors but also affect theheat transfer efficiency of direct solar absorbers. Thermal conductivity is an important

parameter for heat transfer fluids. It also affects the collectors heat transfer efficiency. Great

efforts have been made to the rheological behaviors and thermal conductivities of nanofluids,

and these studies are helpful to the research of nanofluids as solar absorption working fluids.

2.1. ABSORBING CAPACITY DIFFERENT NANOFLUID:

The absorbance of AlNwater nanofluid and Zno- water nanofluid is lower than

50% in wide spectral region (wavelength > 1170nm). The absorbance of these two

nanofluids is greater than 90% in spectral region of wavelength > 1330nm. The absorbance of ZrCwater nanofluid is greater than 90% at most wavelength.

The absorbance of TiNwater nanofluid is greater than 95% in whole spectrum.

ZrCwater nanofluid has the highest absorptance among TiO2 and SiO2.

Carbon black has very good absorption in the whole sunlight wavelength range. The

solar absorbance in the wavelength range 200nm2500nm is over 96% somewhat

better than TiO2, SiO2 and ZrC.


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2.2. THERMO-PHYSICAL PROPERTIES OF NANOPARTICLES

NANO-

PARTICLES

PARTICLE

SIZE

nm

THERMAL

CONDUCTIVITY

W/m/k

HEAT CAPACITY

J/kg/k

WATER SOLUBLE?

COPPER 40 400 385 INSOLUBLE

SILVER 20-80 429 233 INSOLUBLE

GRAPHITE 40 25470 711 INSOLUBLE

TITANIUM

OXIDE

39 11.7 711 INSOLUBLE

ZINCOXIDE 20 26 962 INSOLUBLE

ALUMINA 30 30 930 INSOLUBLE

ZIRCONIUM

CARBIDE

20 25 - INSOLUBLE

SILICON

DIOXIDE

15-30 1.4 - SOLUBLE

ALUMINIUM

NITRIDE


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into the base liquid enhanced the thermal conduction and the enhancement increased with

increasing particle concentration and decreasing particle size. Their results also showed that

the convective heat transfer coefficient increases with nanoparticle concentration in both the

laminar and turbulent flow regimes and the effect of particle concentration seems to be more

considerable in the turbulent flow regimes for the given flow Reynolds number and particlesize. Pressure drop of nanofluids was very close to that of the base liquid for given flow

Reynolds number. Predictions of the pressure drop with the conventional theory for the base

liquid agree well with the measurements at relatively low Reynolds numbers. Deviation

occurs at high Reynolds numbers possibly due to the entrance effect.

8) Kulkarni et al., (2008) investigated heat transfer and fluid dynamic performance of

Nanofluids comprised of silicon dioxide (SiO2) nanoparticles suspended in a 60:40 (% by

weight) ethylene glycol and water (EG/water) mixture. The heat transfer test section was a

straight copper tube with outside diameter of 4.76 mm, inside diameter of 3.14 mm, and a

length of 1 m. The wall temperature was measured by means of six thermocouples mounted

on the tube surface along the length. The inlet and outlet temperatures of the nanofluid were

measured using two thermo wells at the inlet and outlet of the test section. Two plastic

fittings at inlet and outlet section of the copper tube provide a thermal barrier to axial heat

conduction. The test section was heated electrically by four strip heaters to attain the constant

heat flux boundary condition. The test section was insulated by 10 cm of fiber glass to

minimize the heat loss from the heat transfer test system to ambient air. A four-pass shell and

tube counter flow heat exchanger cools the nanofluids to keep the inlet fluid temperature

constant using shop water. The effect of particle diameter (20 nm, 50 nm, 100 nm) on the

viscosity of the fluid was investigated. They performed experiments to investigate theconvective heat transfer enhancement of nanofluids in the turbulent regime by using the

viscosity values measured. They observed increase in heat transfer coefficient due to

nanofluids for various volume concentrations and loss in pressure was observed with

increasing nanoparticle volume concentration.

9) Hwang et al., (2009) investigated flow and convective heat transfer characteristics of

water-based Al2O3 nanofluid flowing through a circular tube of 1.812 mm inner diameter

with the constant heat flux in fully developed laminar regime. Water-based Al2O3 nanofluid

with various volume fractions ranging from 0.01% to 0.3% are manufactured by the two-step

method. They also measured physical properties of water-based Al2O3 nanofluids such as the

viscosity, the density, the thermal conductivity and the heat capacity. They presented that the

nanoparticles suspended in water enhance the convective heat transfer coefficient in the

thermally fully developed regime, despite low volume fraction between 0.01 and 0.3 vol%.

Especially, the heat transfer coefficient of water-based Al2O3 nanofluids was increased by

8% at 0.3 vol% under the fixed Reynolds number compared with that of pure water and the

enhancement of the heat transfer coefficient is larger than that of the effective thermal

conductivity at the same volume concentration. Based on their experimental results, it was

shown that the Darcy friction factor of water-based Al2O3 nanofluids experimentally

measured has a good agreement with theoretical results from the friction factor correlation forthe single-phase flow (f = 64/ReD).


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10) Sharma et al., (2009) conducted experiments to evaluate heat transfer coefficient and

friction factor for flow in a tube and with twisted tape inserts in the transition range of flow

with Al2O3 nanofluid. Hydro dynamically and thermally developed heat transfer test section

is having 1.5 m long with an L/D ratio of 160. The tube was heated uniformly for a length of1.5 m by wrapping with two nichrome heaters of 1 kW electrical rating. Their twisted tapes

were made from 1 mm thick and 0.018 m width aluminum strip. The two ends of the strip are

held on a lathe and subjected to 180 twist by turning the chuck manually and obtained twist

ratios of 5, 10 and 15. The results showed considerable enhancement of convective heat

transfer with Al2O3 nanofluids compared to flow with water. They found that the effect of

inclusion of twisted tape in the flow path gives higher heat transfer rates compared to flow in

a plain tube. They also observed the equation of Gleninski(1976) applicable in transitional

flow range for single-phase fluids exhibited considerable deviation when compared with

values obtained with nanofluid. The heat transfer coefficient of nanofluid flowing in a tube

with 0.1% volume concentration was 23.7% higher when compared with water at number of

9000.

3. SOLAR COLLECTOR DESCRIPTION:

Usually, conventional solar collectors use pipes attached to the collecting plate and a heat

transfer fluid, such as water, to transfer by natural or forced circulation the heat captured by

the solar collector to a storage tank. Some of the short comings associated with conventional

solar collectors include of the forced circulation system due to the pump and its extracted

power, extra space required for the natural circulation system due to the position limitationsrequired, the night cooling due to the reverse flow of cooled water, freezing of the water on

cold nights, pipe corrosion due to the use of water and the limited quantity of heat transferred

by the heat transfer fluid. Promising solution is the use of heat pipe.


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3.1. Heat Pipe

The heat pipe is a device of very high thermal conductance; that is, it will transport

thermal energy without an appreciable drop in temperature. The heat pipe is suitable for a

wide range of applications including solar collector. In a heat pipe, the process is evaporationCondensation convection. Thus, solar collectors with heat pipes have a lower thermal mass,

resulting in a reduction of start-up time.

A heat pipe is a very efficient heat conductor. Heat pipes are the heat transfer

devices available to deal with the high density electronic cooling problem due to their

high thermal conductivity, reliability and low weight. A Heat pipe uses the principles of

both thermal conductivity and phase transition to manage the heat transfer between two

solid interfaces. Due to the high capacity to heat transfer, heat exchanger with heat pipes

has become much smaller than traditional heat exchangers in handling high heat fluxes.

Furthermore, the thermal resistance and heat transfer capability are affected by the

influence of various parameters such as working fluid, tilt angle, fill ratio, wick

structure, thermal properties, heat input and applications in different fields.

Heat pipes are one of the most effective procedures to transport thermal energy from

one point to another. It uses two principles of thermal conductivity and phase transition to

efficiently manage the transfer of heat. Heat pipes contain no mechanical moving parts and

typically require no maintenance. The concept of heat pipe was originally invented by

Gaugler of the General Motors Corporation. In1944.

The advantage of heat pipes over many other heat- dissipation mechanisms is their

great efficiency in transferring heat. They are fundamentally better at heat conduction overa distance than an equivalent cross-section of solid copper (a heat sink alone, though

simpler in design and construction, does not take advantage of the principle of matter phase

transition). A second feature of the heat pipe is that relatively large amounts of heat can be

transported with small light weight structures. The amount of heat that can be transported as

latent heat of vaporization is usually several orders of magnitude larger than can be

transported as sensible heat in a conventional convective system with an equivalent

temperature difference. The performance of a heat pipe is often expressed in terms of

equivalent thermal conductivity. In applications where conventional cooling methods are

not suitable, heat pipes are being used very often. Once the need for heat pipe arises, the

most appropriate heat pipe needs to be selected. Often this is not an easy task. For

applications involving energy conservation, the heat pipe is a prime candidate and has been

used to advantage in heat recovery systems and energy conversion devices. Conservation of

energy has never been more important before, as the cost of fuel is ever rising and the

reserves are diminishing. The heat pipe provides an effective tool in a large number of

applications associated with conservation.


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The basic heat pipe is a closed container consisting of a small amount of vaporizable fluid

(e.g., a refrigerant).The heat pipe employs an evaporating condensing cycle, which acceptsheat from an external source, uses this heat to evaporate the liquid (latent heat) and then

releases latent heat by reverse transformation (condensation) at a heat sink region. This

process is repeated continuously by a return feed mechanism of the condensed fluid back tothe heating zone. In the solar collector, the condensation zone is at a higher level than the

evaporation zone .The transport medium condensed (in the condensation zone) returns to the

evaporation zone under the influence of the gravity. The maximum operating temperature of

a heat pipe is the critical temperature of the used heat transfer medium.


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3.2. STUDY OF FLAT PLATE COLLECTOR USING HEAT PIPES

1. Two identical with same dimensions, experimental set up of flat plate collectors using

-heat pipes were fabricated. In each set up three identical wickless copper heat pipes

are used having length 620 mm and outer diameter of 18 mm. The working fluid usedin one set up is pure water and in another pure water with nanoparticles. The

nanoparticles used are CNT having diameter 10-12 nm & length 0.1-10 J.l. For the

dispersion of CNTs (0.15% by volume) in aqueous media (water) functionalization

process is used. These set ups are initially tested at Indian standard tilt angle 31.5 and

Maximum performance angle 50. At the same angles these collectors are tested using

the solar tracking system. Both collectors gave maximum instantaneous efficiency at

the 50 for with and without tracking. The nanofluid working fluid collector gave the

better performance in the all conditions. For both fluids Solar tracking system founds

more effective and the trend of difference of their instantaneous efficiencies are found

initially more and then decreases it becomes almost equal and then their difference

again increases.

The main objective of this study was to reduce the size of the solar flat plate

collector so that it can be a new innovation for Compaq solar collector would be

utilized in commercial scale.

2. The thermal enhancement of solar collector performance was investigated with silver

nano-fluid as working fluid. The silver nano-particle size was 20 nm with

concentrations at 1,000 and 10,000 ppm and the based working fluid was water. The

experiments were undertaken with three identical flat plate solar collectors each had

an area of 0.15 x 1.0 m2. When the concentration of silver nano-fluid increased more

heat from solar collector or less heat loss was obtained then the difference between

inlet and outlet temperatures of the working fluid from the flat-plate solar collector

increased. However, the concentration at 1,000 ppm showed insignificant results

compared with water. Use of silver nano-fluid as a working fluid could improve

thermal performance of flat-plate collector compared with water, especially at high

inlet temperature.

3. Thermomax Evacuated Heat Pipe Solar Collectors (tubes) operate differently than the

other collectors available on the market. These solar collectors consist of a heat pipeinside a vacuum sealed tube, as shown.

Each tube contains a sealed cooper pipe (heat pipe).

The pipe is then attached to a black copper fin that fills the tube (absorber

plate).

Protruding from the top of each tube is a metal tip attached to the sealed pipe

(condenser). These tubes are mounted, the metal tips up, into a heat exchanger.

As the sun shines on the black surface of the fin, the liquid inside the heat pipe

is heated.

Hot vapor rises to the top of the pipe.Water, or glycol, flows through themanifold and picks up the heat from the tubes.


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The heated liquid circulates through another heat exchanger and gives off its

heat to water that is stored in a solar storage tank.

The system is simple to install and easy to expand.

3.3. PROPOSED DESIGN OF SOLAR COLLECTOR

A heat pipe acts like a high conductance

thermal conductor. Due to its thermal-physicalproperties, its heat transfer rate is thousand's

times greater than that of the best solid heat

conductor of the same dimensions. The basic

heat pipe is a closed container consisting of a

capillary wick structure and a small amount of

vaporizable fluid. The heat pipe employs an

evaporating-condensing cycle, which accepts

heat from an external source, uses this heat to

evaporate the liquid (latent heat) and thenreleases latent heat by reverse transformation

(condensation) at a heat sink region. This

process is repeated continuously by a return

feed mechanism of the condensed fluid back to

the heat zone.


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Solar collector is a flat plate collector having dimension 0.85 m x 0.60m with a glass cover.The collector absorber is a 2mm thick black painted steel sheet. It consists of six tin heat

pipes having inner diameter of 19mm and length 1m. Evaporator length is 85cm and

condenser length is 15cm. Each individual heat pipe is mechanically bonded to the steel

absorber plate. The absorber plate is anodized matt black to enhance its ability to absorb heat.

The heat absorbed by the heat pipes was removed and measured using a water-cooled heat

exchanger. The heat exchanger consisted of six inter-connected tin collars, with an outside

diameter of 25 mm and 150 mm length which fitted around the condenser section of the heat

pipes.

The absorber plate and heat exchanger are housed in wooden framework. The panel rests on a

backing insulation layer of 50 mm thick glass wool while the condenser section is insulated

with Aeroflex sheet insulation. Ordinary glass window is chosen as the upper glazing for the

collector. The air gap between the glass cover and the absorber plate is 40 mm.

3.4. EFFECT OF L/di RATIO ON EFFICIENCY OF SOLAR COLLECTOR:

Efficiency for lesser L/di ratio is better due to increase of capillary pumping pressure whichin turn results in increase in heat transport factor when L/di is reduced.


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3.5. EFFECT OF Le/Lc ratio:

With the increase of the heated length-cooled length, Le/Lc, the absorber area will increase

and thus both the absorbed solar energy by absorber plate and the heat loss from the absorberwill increase. On the other hand the heat transfer coefficient in condenser will increase and

thus causing to increase the heat transfer rate in the condenser. As the solar energy absorbed

by absorber plate increases, heat transfer coefficient of evaporator section of heat pipe

decreases and heat transfer coefficient in condenser section increases with increase in the

heated length-cooled length ratio, Le/Lc. The increased Le/Lc seems to provide a more

efficient system as a whole. However, there is a limiting value of Le/Lc above which thetrend will become opposite [18]. The factors that dominate the optimum ratio are heat pipe

working fluid and heat pipe diameter.

4. THERMAL ANALYSIS:

The heat pipe solar collector was made up of a number of heat pipes where the condenser of

heat pipes mounted into a heat exchanger (manifold). The manifold was a copper pipe thatwrapped around each heat pipe condenser. The water flowed through the manifold and picked

up heat from the heat pipe condenser.For the theoretical steady state analysis of the system assumptions made are:

The heat exchanger can absorb all the heat delivered by the evaporator.

The overall heat loss coefficient between the collector and the ambient is assumed to

be constant.

The heat loss from the heat exchanger and the ambient is negligible.For a collector with n heat pipes, the water flows from one condenser to another. The outlet

water temperature of the first condenser becomes the inlet water temperature of the second

one, and so on.

The actual heat transfer rate for a single heat pipe Qhp1, which is the thermal energy transferfrom evaporator to the condenser section, may be written as:


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The heat transfer between a single heat pipe and the cooling liquid may be expressed as

(3)

From Eqs (1) and (3) condenser outer surface temperatures may be written as:

The overall condenser heat transfer coefficient can be written as

Where Di is the inside diameter of heat exchanger and do is the outside diameter of heat pipe.

The fluid flow in the manifold is considered to be fully developed laminar flow. It is assumedthat the flow inside the condenser of the heat pipes is thermally developed and therefore

under a constant heat flux boundary condition at the wall, the Nusselt number is constant.

Thermal conductivity of water at 20 degree Celsius = 0.6 W/mk

Thermal conductivity of water at 40 degree Celsius = 0.63W/mk

Thermal conductivity of water at 60 degree Celsius = 0.654 W/mkThermal conductivity of water at 80 degree Celsius = 0.670W/mk

Thermal conductivity of water at 100 degree Celsius = 0.679W/mk


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The outlet water temperature from the first condenser, Tc,o1 can be calculated from thermalresistance analysis.

In the vapour space, the only end-to-end temperature variations are associated with changes

in vapour pressure caused by vapour flow pressure drops. These pressure drops are very

small, and the vapour space is assumed to operate at constant saturation pressure andtemperature along the axial length of the heat pipe. However, since heat is transferred radially

into and radially out of the heat pipe, temperature drops occur. In steady state operation, the

total heat added to the evaporator section must be rejected at the condenser section.

Evaporator resistances:

Within the evaporator section, the thermal resistances which account for temperature drops

are container wall and internal resistance at the evaporator. These can be expressed in term of

film coefficient he.

Re,p is the thermal resistances across the thickness of the container wall thickness, may

presented as follows:

Re,i is the thermal resistance that occurs at the vapourliquid interfaces in the evaporator and

may be written as

Condenser resistance:

The vapour condenses on the inner wall of the condenser releasing the latent heat of

condensation. The heat must then be conducted through the container wall to outer wall

surface. The resistance associated with the conduction process through the pipe wall is

The thermal resistance associated with the condensing process is given by

Thermal analysis of a single heat pipe absorber:

The useful energy gained by a single heat pipe, is the difference between solar energy

absorbed and the heat loss to the ambient over the length of the absorber. The rate of useful

energy collected may be modeled according to the well known HottelWiller equation:


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The useful energy extracted in the form of heat by fluid flowing in the heat exchanger can

also be expressed as

So that

In the condenser section of a single heat pipe heat exchanger, cold fluid is in cross flow withvapour flow inside the heat pipe. However, since the vapour inside a heat pipe is almost at

constant temperature, its specific heat, Cp, and capacity rate, CL, will by definition be equalto infinity and as a result Cc=CL 0. Therefore, the effectiveness-NTU equation for this

condition will be as follows

The condenser water temperature at the outlet of a single heat pipe is

For a collector with n heat pipes, as shown in Fig. 5, the water flows from the condenser of

one heat pipe to another. The outlet water temperature of the first condenser becomes the

inlet water temperature of the second condenser. For a collector with n heat pipes the final

temperature can be calculated from


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Thermal analysis of heat pipe array:

The final water outlet temperature for an array of n heat pipes may also be obtained by a

different approach, without going through each condenser and continuing the thermal

analysis. By this method,for overall effectiveness of n condenser, one fluid is in series and

the other fluid is in cross flow. Referring to fluid in series, the overall effectiveness E can be

written as

Assuming equal effectiveness for all condensers

The water outlet and heat pipe temperature of the collector array are

Theoretical efficiency is given by


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Nomenclature:

5. PREPARATION OF CARBON BLACK NANOFLUID:

To obtain stable nanofluids, the carbon powder was pretreated: 7.5 g of carbon powder and200 ml H2O2 (30%) were mixed into a flask and boiled under magnetic stirring for 4 h. Thenadditional 200 ml H2O2 were added and the solution was further stirred and boiled for

another 4 hours and finally it was diluted with distilled water to 300 ml. Hydrogen peroxide

reacts on the carbon surface, and undergoes decomposition to oxygen and water. The reaction

of oxygen with carbon surfaces has two main effects: activation of molecular oxygen on the

surface and stabilization of activated species by formation of covalent bonds with carbon

atoms. The oxidation of carbon significantly alters its physicochemical properties, such as

wettability, sticking and surface adsorption, which contributes to the producing of stable

nanofluids.


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6. EXPERIMENTAL RESULT:

THERMAL CONDUCTIVITY OF CARBON NANOFLUID:

Sample 1 at concentration of 25g/dm3:

Temperature in Kelvin Thermal conductivity in S/cm

303 677

313 860

323 1036

333 1220

343 1447

Graph 1


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Sample 2 at concentration 10g/dm3:


302 45

313 63.2

323 80

333 93

343 109

Graph 2


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Sample 3 at concentration 2g/dm3:


302 11.7

313 16.7

323 20.7

333 25.1

343 30.9

Graph 3


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Sample 4 at concentration 0.1g/dm3:


302 9.1

313 12.1

323 14.5

333 17.2

343 20.6

Graph 4


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7. DISCUSSION ON RESULT:

It can be seen that the temperature of the nanofluids increase more quickly than water.

The addition of carbon particles logically improves the solar thermal energy

absorption properties.

Thermal conductivity of carbon nanofluid is found to be more than water. Thus it is

more efficient for solar collector.

Thermal conductivity of carbon nanofluid at 4 different temperatures were taken for

different concentration values and shown in graphs (Graph1Graph 4). Thermal

conductivity of carbon nanofluid increases linearly with temperature keeping

concentration constant.

Thermal conductivity of carbon nanofluid increase with increasing concentration

keeping temperature constant.

8. CONCLUSION:

In the present work, an experimental investigation of the thermal performance of heat pipe

solar collector together with a simple theoretical analysis have been developed and carbon

black nanofluid is prepared to study its thermal conductivity.The results of the investigation may be summarized as follows:

The pretreatment of carbon nanoparticles with hydrogen peroxide (by heating andmagnetic stirring) results in surface activation and improvement of their physical and

chemical properties, in terms of adsorption and wettability. Stable nanofluids can beobtained by dispersion of these pretreated particles in water. The temperature increase

enhance-ment of carbon black nanofluids is higher than that of TiO2/water,SiO2/water, and ZrC/water nanofluids. This proves once more that these fluids are a

good medium for the absorption of solar energy. These nanofluids are suitable for use

at temperatures up to 90oC at atmospheric pressure.

The results obtained from the developed theoretical model suggest an optimum heated

length-cooled length ratio to absorb more heat and increase the overall amount ofuseful heat.

Finally, the model is capable to predict some performance characteristics of the solar

system, such as heat pipe temperature,water outlet temperature, efficiency, and usefulabsorbed heat.


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9. REFERENCE:

http://nopr.niscair.res.in/bitstream/123456789/5163/1/JSIR%2064(9)%20698-701.pdf

http://scholarsresearchlibrary.com/aasr-vol4-iss6/AASR-2012-4-6-2582-2590.pdf

http://rcme.engr.tu.ac.th/TSME-ICoME%20Web/full_paper_file/ETM/ETM10%20848-1415-

1-RV.pdf

http://www.rmcet.com/lib/E-

Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep20

08/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%

20collector.pdf

http://www.isfh.de/institut_solarforschung/files/jack_eval_methodes_4_heat_pipes_ises_s

wc_11.pdf

http://www.eurekalert.org/pub_releases/2011-04/aiop-nis040411.php

http://en.wikipedia.org/wiki/Solar_thermal_collector

http://www.academia.edu/5320282/Flat_Plat_Solar_Collector_Using_Nanofluids
http://nopr.niscair.res.in/bitstream/123456789/5163/1/JSIR%2064(9)%20698-701.pdfhttp://nopr.niscair.res.in/bitstream/123456789/5163/1/JSIR%2064(9)%20698-701.pdfhttp://scholarsresearchlibrary.com/aasr-vol4-iss6/AASR-2012-4-6-2582-2590.pdfhttp://scholarsresearchlibrary.com/aasr-vol4-iss6/AASR-2012-4-6-2582-2590.pdfhttp://rcme.engr.tu.ac.th/TSME-ICoME%20Web/full_paper_file/ETM/ETM10%20848-1415-1-RV.pdfhttp://rcme.engr.tu.ac.th/TSME-ICoME%20Web/full_paper_file/ETM/ETM10%20848-1415-1-RV.pdfhttp://rcme.engr.tu.ac.th/TSME-ICoME%20Web/full_paper_file/ETM/ETM10%20848-1415-1-RV.pdfhttp://www.rmcet.com/lib/E-Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep2008/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%20collector.pdfhttp://www.rmcet.com/lib/E-Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep2008/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%20collector.pdfhttp://www.rmcet.com/lib/E-Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep2008/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%20collector.pdfhttp://www.rmcet.com/lib/E-Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep2008/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%20collector.pdfhttp://www.rmcet.com/lib/E-Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep2008/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%20collector.pdfhttp://www.isfh.de/institut_solarforschung/files/jack_eval_methodes_4_heat_pipes_ises_swc_11.pdfhttp://www.isfh.de/institut_solarforschung/files/jack_eval_methodes_4_heat_pipes_ises_swc_11.pdfhttp://www.isfh.de/institut_solarforschung/files/jack_eval_methodes_4_heat_pipes_ises_swc_11.pdfhttp://www.eurekalert.org/pub_releases/2011-04/aiop-nis040411.phphttp://www.eurekalert.org/pub_releases/2011-04/aiop-nis040411.phphttp://en.wikipedia.org/wiki/Solar_thermal_collectorhttp://en.wikipedia.org/wiki/Solar_thermal_collectorhttp://www.academia.edu/5320282/Flat_Plat_Solar_Collector_Using_Nanofluidshttp://www.academia.edu/5320282/Flat_Plat_Solar_Collector_Using_Nanofluidshttp://www.academia.edu/5320282/Flat_Plat_Solar_Collector_Using_Nanofluidshttp://en.wikipedia.org/wiki/Solar_thermal_collectorhttp://www.eurekalert.org/pub_releases/2011-04/aiop-nis040411.phphttp://www.isfh.de/institut_solarforschung/files/jack_eval_methodes_4_heat_pipes_ises_swc_11.pdfhttp://www.isfh.de/institut_solarforschung/files/jack_eval_methodes_4_heat_pipes_ises_swc_11.pdfhttp://www.rmcet.com/lib/E-Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep2008/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%20collector.pdfhttp://www.rmcet.com/lib/E-Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep2008/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%20collector.pdfhttp://www.rmcet.com/lib/E-Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep2008/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%20collector.pdfhttp://www.rmcet.com/lib/E-Journals/Experimental%20Thermal%20and%20Fluid%20Science/Vol.32%20No.08%20Sep2008/Theoretical%20and%20experimental%20investigation%20of%20heat%20pipe%20solar%20collector.pdfhttp://rcme.engr.tu.ac.th/TSME-ICoME%20Web/full_paper_file/ETM/ETM10%20848-1415-1-RV.pdfhttp://rcme.engr.tu.ac.th/TSME-ICoME%20Web/full_paper_file/ETM/ETM10%20848-1415-1-RV.pdfhttp://scholarsresearchlibrary.com/aasr-vol4-iss6/AASR-2012-4-6-2582-2590.pdfhttp://nopr.niscair.res.in/bitstream/123456789/5163/1/JSIR%2064(9)%20698-701.pdf


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