v) 5.1 CONCLUSIONS: In this study, heat

   v)                 The numericalanalysis can be done and can be compared with the experimental results.iv)               Other shapes offins (trapezoidal, parabolic, pin fins etc.) as well as its dimensions can bevaried and experimentally checked for the enhancements in heat transfercharacteristics.iii)               The twisted tapestwist ratio can be varied to balance the heat transfer and pressure drop.

ii)                 The optimum heattransfer rate can be found at by increasing the concentration of Fe2O3nanoparticle above 0.2% by volume and keeping a balance on frictionfactor.i)                   The experiment canbe carried out with other types of nanoparticle like Alumina, CuO, SiO2,ZnO, etc.

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Thepresent work was conducted to understand the heat transfer enhancement in heatexchanger with the tube wall inserts using Fe2O3/EthyleneGlycol-Water (40:60) nanofluids. For further research understanding, thefollowing suggestions can be considered:5.2   SCOPE FOR FUTURE WORK: v)               The Pressure dropalso increased with the flow rate as well as with the increase inconcentrations of nanofluids. Another major reason of increase is the tube wallinserts which increase the turbulence and hence leading to increment inpressure drop.

iv)             It seems that theincrease in the effective thermal conductivity and the variations of the otherphysical properties are not solely responsible for the large heat transferenhancement. Brownian motion of nanoparticles maybe one of the major factors inthe enhancement of heat transfers. The presence of nanoparticles and theirrandom motion within the base fluid causes the thinning of thermal boundarylayer and it has important contributions to such heat transfer improvement.

iii)             The Nusselt Numbershowed an increasing trend with increasing volume concentration (up to 0.2%) ofnanoparticle. This is due to increase in heat transfer coefficient and Brownianmovement. At 70°C inlet temperature and 15 LPM, Nusselt Number increased 285when volume concentration of nanoparticle increased up to 0.

2%. ii)               The Overall heat transfercoefficient has increased with the increasing volume concentration ofnanofluids, hence heat transfer also increased accordingly. At 70°C inlettemperature and 15 LPM, the overall heat transfer coefficient and heat transferrate were increased to 593 W/m2K and 2420 W respectively.i)                 The heat transfercoefficient of experimental data for the base fluid show good agreement withthe Dittus-Boelter equation, and that of nanofluid shows good agreement withPak and Cho equation.Thethermal characteristics of nanofluids were experimentally studied and thefollowing conclusions were drawn:5.1   CONCLUSIONS:In this study, heat transfer enhancement in a heatexchanger with the tube wall inserts has been investigated experimentally withfour working fluids namely (40:60) Ethylene Glycol/Water and three differentvolume concentrations of (40:60) Ethylene Glycol/Water based Fe2O3nanofluids. It is found that the presence of Fe2O3nanoparticle in (40:60) Ethylene Glycol/Water can enhance the heat transferrate.

The degree of the heat transfer enhancement depends on the quantity ofnanoparticles added to the base fluid. Inlet temperature was maintainedconstant at 70°C and water flow rate was kept constant and volume flow rate ofnanofluids were varied. The experiment was carried out with volume concentrationsof 0.05, 0.1 and 0.

2% iron oxide in 40:60 mixture of ethylene glycol-water basefluid. The variation of Nusselt Number, Reynolds Number and percentage increasein Nusselt Number, Overall heat transfer coefficient and heat transfer with variousvolume concentrations of nanofluids were evaluated.CONCLUSIONSCHAPTER-5


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