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ABSTRACT
This work presents the heat transfer and friction characteristics of turbulent circular tube flow through a square wing with combined solid ring twisted tape inserts have been analyzed experimentally. Experiments have been carried out for the range of Reynolds number (Re) from 3000 to 21000, number of twisted tape inserts from 1.0–4.0, ring pitch ratios
from 0.5 to 2.0, wing pitch ratios
from 2.0 to 3.5, wing depth ratios
from 0.083 to 0.333 and ring diameter ratio
from 0.831 to 0.932. The experimental results show that the heat transfer is increased around 5.66 times higher than plane circular heat exchanger tube. The optimum value of thermal hydrodynamic performance has been found corresponds to
= 3.0,
= 1.0,
= 3.0,
= 0.167 and
. The finest value of thermal and hydrodynamic performance has been found to be 2.74 for
of 3,000 within the range of the parameters investigated.
Nomenclature
| A | = | Convection heat area of circular tube, m2 |
| AO | = | Area of orifice plate, m2 |
| = | Coefficient of discharge | |
| = | Specific heat capacity of air, | |
| = | Diameter of tube, | |
| = | Distance between rings, | |
| = | Inner diameter of rings, | |
| = | Outer diameter of rings, | |
| = | Ring ratio | |
| = | Rings pitch ratios | |
| = | Depth ratio | |
| = | Friction factor | |
| = | Heat transfer coefficient | |
| = | Head difference, | |
| = | Heat exchanger tube | |
| = | Thermal conductivity of air, | |
| L | = | Length of tube, |
| m | = | Mass flow rate of air, |
| = | Number of twisted tape | |
| = | Nusselt number | |
| ΔP | = | Pressure drop, |
| = | Prandtl number | |
| = | Pitch between wings, | |
| = | Wing pitch ratios | |
| = | Heat flux | |
| = | Useful heat transfer, W | |
| = | Reynolds number | |
| = | Rayleigh number | |
| = | Swirl parameter | |
| = | Inlet temperature, | |
| = | Mean temperature, | |
| = | Outlet temperature, | |
| = | Twisted tape | |
| TTT | = | Typical twisted tape |
| = | Total wall temperature, | |
| = | Twist ratio | |
| = | Air flow velocity, | |
| = | Wings depth, | |
| = | Width of tape, | |
| = | Wing depth ratios | |
| Greek Symbols | = | |
| = | Density, | |
| = | Dynamic viscosity, | |
| = | Hydrodynamic thermal performance parameter | |
| = | Kinematic viscosity of air, m2/s |