Hybrid dry cooler heat exchange with water-droplet slit and water-droplet splitting louver for heat exchangers with primarily latent heat transfer

Abstract

Hybrid dry cooler heat exchangers with one or more tube-fin heat exchange assemblies including at lease one such assembly wetted by water dropped on it with the first of such assembly stamped to provide arrays of slit / louver combinations breaking up water droplets and averting flight of droplets into a gas flowing between adjacent fins.

Description

FIELD AND BACKGROUND OF THE INVENTION[0001]The present invention relates to heat exchangers, often used for large air-conditioning and large refrigeration systems and more particularly to the finned tube heat exchangers used therein for the hybrid cooling of a liquid medium or for the liquefaction of refrigerants. Such types of apparatus have an air-side heat transfer surface wettable with water or other liquid and exposed to ambient air sucked in by at least one fan as coolant, for evaporation of water carried in the circulation system.[0002]Hybrid dry coolers are known (see e.g., European Patent EP 428 647 B1) in which the liquid medium of the primary cooling circuit flows through a finned heat exchanger and the heat to be dissipated via the cooling fins is emitted to the air stream partially as sensible and partially as latent heat.[0003]One or several fans suck the air stream through the heat exchanger and always run at the same rotating speed. The wetting water is pumped from a...

AI Technical Summary

Benefits of technology

[0015]Even at low flow velocities, the uneven geometric arrangement of an elementary formation of the water-droplet slit and water-droplet splitting louvers produces sufficient turbulence to increase the heat transfer coefficient in pure dry operation and the evaporation percentage during wetting.

[0016]The louvers are arranged at different distances from each other and produce no noises over a very broad range of different flow velocities. Both the exciter frequencies and the natural frequencies differ as a result of the geometric arrangement. This permits a multiple repetition of the elementary arrangement over the entire fin surface, or an improvement to this heat exchanger by increasing the heat transfer coefficient in pure dry operation and an increase in the evaporation percentage during wetting at a very broad range of different flow velocities with simultaneous elimination of troublesome noise emissions. The system also does not tend to vibrate.

[0018]This results in a noticeable decrease in the heat transfer area required for a certain performance, and with it a reduction in the investment costs. Thanks to higher air loading, the switchover point from dry operation to wetting does not shift noticeably, despite the reduced surface, enabling the economical operation of the hybrid cooler to be retained.

[0019]Other advantages that result from higher air loading during wetting include a more economical operation of a connection in series of a drying cooler for purely sensible heat transfer with a hybrid (water-wettable) cooler for mainly latent heat emission, especially at high cooling-medium entry temperatures, a very large cooling range and use of the same fans for forced-air feeding through both heat exchangers. The same advantages also result during completely wetted operation of heat exchangers connected in series or in parallel.

Problems solved by technology

With smooth fins, the droplets unavoidably produced when wetting the fins with excess water are held suspended between the fins by the tube effect of the air stream, and are carried out as a result of excessively high surface tension.

This filmy wetting inevitably leads to a major increase in the surface wet with water, and therefore to a noticeable increase in the latent heat transfer through evaporation.

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