(57) A heat exchanger, for use especially but not exclusively in a gas-fired appliance,
is of unitary construction and comprising a water inlet manifold (11) and a water
outlet manifold (12) interconnected in water flow communicating relationship by at
least one externally-finned heat exchange tube (13).
A preferred heat exchanger consists of three parallel externally-finned heat exchanger
tubes integral with the end manifolds.
With such a unitary heat exchange structure it will be manifest that during installation
and servicing, save for water pipe connections to the manifolds and a drain plug,
there are no sealing requirements and consequently there are no possible leakage paths
from the heat exchanger perse.
The heat exchanger is preferably but not exclusively formed of cast-iron and is preferably
but not exclusively formed using a green sand moulding process with the fins (15)
disposed as closely together as is possible within the limitations of the moulding
process. The fins are preferably of radiussed configuration and also of converging
configuration both transversely and axially of the respective heat exchanger tube
to facilitate the moulding process.
Turbulence-creating means (17) is provided between at least some of the adjacent fins
of the or each heat exchange tube to ensure re-mixing of combustion products of different
temperature in the region of the heat exchange tube to improve the heat transfer qualities
of the heat exchanger.
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