3.1) TROCATER
In fuel burn applications, the pre-heating of combustion air increases burning efficiency.
This is usually done using the hot and dirty exhaustion gase. Instead of expelling the
exhastion gas directly to atmosphere, its heat is partially recovered in order to pre-heat the
clean air through the use of regenerative heat exchangers. The overall fuel saving resulting
from this practice is in the range of 10-12%.
Heat pipe technology allows the development of compact heat exchangers of easy maintenance,
with no rotational parts, and no need of external energy input. Such technology is widely used
in the Far East (i.e., China and South Korea). Since year 2000, PETROBRAS and LABTUCAL have been
researching, developing, and applying this technology in Brazil. Figure 1 shows the concept of heat
exchangers using heat pipes. Basically it has two rectangular ducts, one on the top of the other.
Hot gases flow in the lower duct, while the cool, clean air flows inside tthe upper duct. A bundle
of vertical thermosyphons connects both ducts, transferring heat from hot gases to the cold gas duct.
The temperature levels of hot gases affect the choice of thermosyphon to be used in the heat exchanger. LABTUCAL has been working on applications in which temperatures range from 100-1000ºC. The 100-250ºC range is most widely used. Higher temperatures are considered in special applications, such as the high and intermediate temperature heat pipes.
Publications: MOLZ, M.; MANTELLI, M. B. H.; LANDA, H. G. Transient Modelling of a Closed Two-Phase Thermosyphon for Heat Exchanger Application. In: 13th International Heat Pipe Conference, 2004, Shanghai, 2004.
MANTELLI, M. B. H.; MARTINS, G. J.; REIS, F.; ZIMMERMAN, R.; ROCHA, G. K. L.; LANDA, H. G. Experimental Study of Vertical Thermosyphons for Industrial Heat Exchanger Applications. In: 13th International Heat Pipe Conference, 2004, Shanghai, 2004.
