NAME:- NEHA KUMARI

REG.NO:-1011018058

SEMSESTER:-7TH

SECTION:-D

HEAT TRANSFER OF NANOFLUIDS IN A SHELL AND TUBE HEAT

EXCHANGER

INTRODUCTION HEAT EXCHANGER NANOFLUIDS EXPERIMENTAL SETUP DATA PROCESSING RESULTS CONCLUSION REFERENCE

CONTENTS

A wide verity of industrial processes involve the transfer of heat energy. Throughout any industrial facility, heat must be added, removed or moved from one stream to another and it become major task for industrial necessity.

The enhancement of heating or cooling in an industrial process may create a saving in energy, reduce process time, raise thermal rating, and improve working life of equipment.

OBJECTIVE:- To enhance effective fluid

thermal conductivity and heat transfer coefficient

by suspending solid nanoparticles.

INTRODUCTION

nanoparticles

HEAT EXCHNAGER is a device which is used to transfer heat between two or more fluid steams at different temperature.

It is widely used in power generation, chemical processing, electronic cooling, air conditioning, refrigeration, automotive applications.

HEAT EXCHANGER

Shell and tube heat exchanger

According to the flow arrangement:-

1. Parallel flow H.E:- the fluids enters to the same end and travel parallel to one another to other side.

CLASSIFICATION OF HEAT EXCHANGER

Shell-side fluid inlet

Tube -side fluid inlet

Tube -side fluid outlet

Shell- side fluid outlet

2. Counter flow H.E:- In counter-flow heat exchangers the fluids enter the exchanger from opposite ends. The counter current design is most efficient, in that it can transfer the most heat from the heat (transfer) medium.

Tube-side fluid outlet

shell- side fluid inlet

Shell-side fluid outlet Tube-side

fluid inlet

According to geometry construction:-1. Shell and tube heat exchanger

2. Plate type heat exchanger

3. Extended surface heat exchanger

Here in the experimental setup shell and tube type heat exchanger is used. And the flow of fluid is counter flow.

Suspension of nanoparticles in base fluid. Nanoparticles are made of metal , oxide, carbides. Common base fluids may be water, ethylene glycol and oil. Nanofluids enhances thermal conductivity and convective heat

transfer coefficient as compare to base fluid.

Advantages of nanoparticles:-

I. High specific surface area

II. High dispersion stability

III. Reduced particle clogging

IV. Adjustable properties, including thermal conductivity and surface wettability, by varying particle concentrations to suit different applications.

NANOFLUIDS

1. Nanoparticle materials includes:-

◦ Oxide ceramics – Al2O3, CuO, TiO2

◦ Metal carbides – SiC

◦ Nitrides – AlN, SiN

◦ Metals – Al, Cu

◦ Nonmetals – Graphite, carbon nanotubes

2. Base fluid includes:-

◦ Water

◦ Ethylene- or tri-ethylene-glycols and other coolants

◦ Oil and other lubricants

◦ Bio-fluids

◦ Polymer solutions

◦ Other common fluids

Materials for Nanoparticles and Base Fluids

EXPERIMENTAL SETUPNANOFLUID INLET

NANO FLUID OUTLET

WATER INLET

WATER OUTLET

Two series of nanofluids were prepared using two different types of nanoparticles, γ-Alumina(γ-Al2O3) and Titanium dioxide(TiO2), while water is used as a base fluid.

The nanofluids with different particle volume concentrations were prepared to investigate the effect of nanoparticle concentrations on the heat transfer performance of nanofluids.

The nanoparticle volume concentrations of γ-Al2O3/water and TiO2/water nanofluids vary in the range of 0.3-2% and 0.15-0.75% ,Respectively.

Table1

The experimental data were used to calcuclate the overall heat transfer coefficient and convective heat transfer coefficient of nanofluids with various particle volume concentration and peclet number.

The heat transfer rate of nanofluid is:

Q=ṁCpnf(Tout-Tin)Where, ṁ = the mass flow rate of nanofluid

Cpnf= effective specific heat of nanofluid

Tout and Tin= outlet and inlet temperature of nanofluid The heat transfer coefficient of the test fluid, hi, can be calculated by

the following equation:

DATA PROCESSING

Where, Di and Do = the inner and outer diameter of tubes, respectively.

Ui =the overall heat transfer coefficient based on the inside tube area.

hi and ho = individual convective heat transfer coefficient of fluids inside and outside the tubes respectively.

kw = the thermal conductivity of the tube wall.

Ui is given by:-

Where , where Ai = πDiL and ΔTlm is the logarithmic mean temperature difference.

Peclet number is given by:-

Where, Pe is peclet number of particles

Vm=mean velocity

dp=diameter of particles

αnf= diffusitivity of nanofluid

RESULTS

FIG 2: Overall heat transfer coefficient of γ-Al2O3/water nanofluid versus Peclet number for various volume concentrations.

Volume concentration of γ-Al2O3(in percentage% )

0.30 0.50 0.75 1 2

enhancement of Overall heat transfer coefficient(Ui)(in %)

14 20 16 15 9

FIG3: Overall heat transfer coefficient of TiO2/water nanofluid versus Peclet number for various volume concentrations.

Volume concentration of TiO2

(in percentage% )0.15 0.30 0.50 0.75

enhancement of Overall heat transfer coefficient(Ui)(in %)

11 24 16 13

FIG4:Convective heat transfer coefficient of γ-Al2O3/water nanofluid versus Pecletnumber for different volume concentrations

Volume concentration of γ-Al2O3(in percentage% )

0.30 0.50 0.75 1 2

enhancement of convective heat transfer coefficient(hi)(in %)

46 56 46 38 19

FIG4 :Convective heat transfer coefficient of γ-Al2O3water nanofluid versus Peclet number for different volume concentrations

FIG5: Convective heat transfer coefficient of TiO2/water nanofluid versus Peclet number for different volume concentrations

Volume concentration of TiO2

(in percentage% )0.15 0.30 0.50 0.75

enhancement of convective heat transfer coefficient(hi)(in %)

20 56 33 18

Addition of nanoparticles to the base fluid enhances the heat transfer performance and results in larger heat transfer coefficient than that of the base fluid at the same Peclet number.

Both nanofluids have the different optimum volume concentrationin which the heat transfer characteristics show the maximum enhancement. The nanoparticle with less mean diameter (TiO2 nanoparticle) has a lower optimum volume concentration.

At different nanoparticle concentrations the heat transfer enhancement of both nanofluids are not the same. TiO2/water and γ-Al2O3/water nanofluids possess better heat transfer behavior at the lower and higher volume concentrations, respectively.

CONCLUSION

[1]Farajollahi, S.Gh. Etemad, M. Hojjat ,Heat transfer of nanofluids in a shell and tube heat exchanger heat transfer 53(2010)12-17.

[2] Sarit,K.Das., Stephen U. S. Choi, “A Review of Heat Transfer in Nanofluids”.2009

[3] M. Raja a*, R.M. Arunachalam b and S. Suresh c,Experimental studies on heat transfer of alumina/water nanofluid in a shell and tube heat exchanger.

REFERENCE