Turn
on the heat
Dr
Anupam Dewan, emphasises the need for better heat transfer techniques
in heat exchangers to augment productivity
Heat
transfer is crucial to several industrial and environmental processes
as well as to energy production and conversion. Heat exchangers are
used in various industrial applications and are devices to transfer
thermal energy between two (or more) fluids at different temperatures
without having direct contact. The design procedure of heat exchangers
is quite complicated, as it needs exact analysis of heat transfer rate
and pressure drop estimations apart from the issues, such as, long-term
performance and economic aspect of the equipment. The major challenges
to the design of a heat exchanger are to make it compact, which is,
to achieve a high heat transfer rate and at the same time to allow its
operation with a small power loss (or pumping power). Compact heat exchangers
are being widely used in the industry and are characterised by a relatively
large surface area in a given volume compared to a conventional heat
exchanger. Some recent designs of compact heat exchangers can have only
5 per cent of the volume of the standard equivalent. A compact heat
exchanger can work effectively only if a suitable heat transfer augmentation
technique has been incorporated to it.Lately high costs of energy and
material have resulted in increased efforts to design and produce efficient
heat exchangers and therefore studies on heat transfer enhancements
have attracted new interests. The heat exchanger industry has been striving
for improved thermal contact (enhanced heat transfer coefficient) and
reduced pumping power in order to improve the thermo-hydraulic efficiency
of heat exchangers. A good heat exchanger design should have an efficient
thermodynamic performance, which is, a minimum generation of entropy
or minimum destruction of available work in a system incorporating heat
exchanger. It is almost impossible to stop available energy loss completely,
but it can be minimised through an efficient and practical design of
a heat exchanger.
Need for heat transfer enhancement
Techniques for heat transfer augmentation are relevant
to several engineering applications. Further, as a heat exchanger gets
older, the resistance to heat transfer increases due to fouling or scaling.
These problems are common for heat exchangers used in marine ...
....CONTD
