v) has important contributions to such heat transfer




The numerical
analysis can be done and can be compared with the experimental results.

Other shapes of
fins (trapezoidal, parabolic, pin fins etc.) as well as its dimensions can be
varied and experimentally checked for the enhancements in heat transfer

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The twisted tapes
twist ratio can be varied to balance the heat transfer and pressure drop.

The optimum heat
transfer rate can be found at by increasing the concentration of Fe2O3
nanoparticle above 0.2% by volume and keeping a balance on friction

The experiment can
be carried out with other types of nanoparticle like Alumina, CuO, SiO2,
ZnO, etc.

present work was conducted to understand the heat transfer enhancement in heat
exchanger with the tube wall inserts using Fe2O3/Ethylene
Glycol-Water (40:60) nanofluids. For further research understanding, the
following suggestions can be considered:



The Pressure drop
also increased with the flow rate as well as with the increase in
concentrations of nanofluids. Another major reason of increase is the tube wall
inserts which increase the turbulence and hence leading to increment in
pressure drop.

It seems that the
increase in the effective thermal conductivity and the variations of the other
physical properties are not solely responsible for the large heat transfer
enhancement. Brownian motion of nanoparticles maybe one of the major factors in
the enhancement of heat transfers. The presence of nanoparticles and their
random motion within the base fluid causes the thinning of thermal boundary
layer and it has important contributions to such heat transfer improvement.

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

The Overall heat transfer
coefficient has increased with the increasing volume concentration of
nanofluids, hence heat transfer also increased accordingly. At 70°C inlet
temperature and 15 LPM, the overall heat transfer coefficient and heat transfer
rate were increased to 593 W/m2K and 2420 W respectively.

The heat transfer
coefficient of experimental data for the base fluid show good agreement with
the Dittus-Boelter equation, and that of nanofluid shows good agreement with
Pak and Cho equation.

thermal characteristics of nanofluids were experimentally studied and the
following conclusions were drawn:


In this study, heat transfer enhancement in a heat
exchanger with the tube wall inserts has been investigated experimentally with
four working fluids namely (40:60) Ethylene Glycol/Water and three different
volume concentrations of (40:60) Ethylene Glycol/Water based Fe2O3
nanofluids. It is found that the presence of Fe2O3
nanoparticle in (40:60) Ethylene Glycol/Water can enhance the heat transfer
rate. The degree of the heat transfer enhancement depends on the quantity of
nanoparticles added to the base fluid. Inlet temperature was maintained
constant at 70°C and water flow rate was kept constant and volume flow rate of
nanofluids were varied. The experiment was carried out with volume concentrations
of 0.05, 0.1 and 0.2% iron oxide in 40:60 mixture of ethylene glycol-water base
fluid. The variation of Nusselt Number, Reynolds Number and percentage increase
in Nusselt Number, Overall heat transfer coefficient and heat transfer with various
volume concentrations of nanofluids were evaluated.




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