الفهرس 
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Abstract
The experimental investigation is studying the effect of variables section
of coil heat exchanger on heat transfer and friction factor. The Reynolds number
inside the shell is considered a constant value of 3500, while the Reynolds
through the coil tube is varied from 1500 to 4500. The AL2O3 nanoparticles are
added distilled water with different volume concentrations (0.1 %, 0.2 %, and
0.3 %) and used as a working through a coil tube side. In addition, five types of
coils cross-section are used through this study, straight, low to high, high to
low, high to low to high, and low to high to low and the coil tube 7 mm
diameter.
The experimental study showed that the Nusselt number increases with
the increase of Reynolds number. While the friction factor is decreasing with
the increase of Reynolds number. In addition, the average Nusselt number
through the coil of nanofluid is enhancement by 7.3 %, 17.7 %, and 25.4 %
compared with based water for a nanofluid concentration of 0.1 %, 0.2% and 0.
3 % for straight coil respectively. Also, the average Nusselt number showed is a
maximum value for low to high coil compared by other coils. Where, the value
of the average Nusselt number of low to the high coil is increased by 10.3 %,
2.5 %, 5.12 %, and 6.12 % for straight, high to low, high to low high, and low to
high to low coils respectively. In another hand, the average friction factor is a
minimum value for straight compared with other coils. where the value of
average friction factor is 0.097, 0.104, 0.0135, 0.1086, and 0.1084 for straight,
low to high, high to low, high to low to high, and low to high to low coils for all
nanofluid concentrations respectively.
Finally, the heat transfer factor is enhancement by an increase of
nanofluid concentrations. where the heat transfer factor improved by 8 %, 13
%, and 26 % compared by the based water fluid for 0.1 %, a0.2 %, and 0.3 %
III
respectively. Also, the heat transfer factor is the best value for both two coils
high to low to high and low to high to low coils. where the heat transfer factor
is increased by 26 % and 27 % over the unity for two coils high to low to high,
low to high to low.