Abstract: This paper presents a three-dimensional numerical and
experimental geometric optimization study to maximize the total heat transfer
rate between a bundle of finned tubes in a given volume and external flow, for
staggered arrangements of circular and elliptic tubes. Experimental results were
obtained for circular and elliptic configurations with twelve tubes, starting
with an equilateral triangle configuration, which fitted uniformly into the
fixed volume with a resulting maximum dimensionless tube-to-tube spacing where S
is the actual spacing and b is the
smaller semi-axis of the ellipse. Several experimental configurations were built
by reducing the tube-to-tube spacings, identifying the optimal spacing for
maximum heat transfer. Similarly, it was possible to investigate the existence
of optima with respect to other two geometric degrees of freedom, such as tube
eccentricity and fin-to-fin spacing. The results are reported for air as the
external fluid in the laminar regime, for and 1065, where L
is the swept length of the fixed volume. Circular and elliptic arrangements with
the same flow obstruction cross-sectional area were compared on the basis of
maximizing the total heat transfer. Global optima with respect to tube-to-tube
spacing, eccentricity and fin-to-fin spacing for and 1065) were found and reported
in dimensionless terms. A relative heat transfer gain of up to 19% is observed
in the optimal elliptic arrangement, as compared to the optimal circular one.
The heat transfer gain, combined with the relative material mass reduction of up
to 32% observed in the optimal elliptic arrangement in comparison to the
circular, show that the elliptical tubes arrangement has better overall
performance and lower cost than the traditional circular tubes geometry.
Keywords and phrases: constructed theory, tube spacings, fin spacings, eccentricities.
