Heat exchange – Tubular structure – With discrete heat transfer means
Patent
1998-09-25
2000-11-07
Lazarus, Ira S.
Heat exchange
Tubular structure
With discrete heat transfer means
165111, F28B 300, F28F 114
Patent
active
061422231
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to an air-cooled condenser for condensing a vaporous medium, preferably steam.
BACKGROUND ART
Condensers are widely used in the manufacturing, chemical and energy industry. The air-cooled condenser is a special type of condenser, which generally operates under a vacuum. First of all we shall describe the physical processes that take place in air-cooled condensers, to make sure that the operation of the air-cooled condenser according to the invention is understood.
The description of physical processes and of the prior art apply to power plant steam condensers and to condensing steam, but of course the invention is not restricted to this type of condenser: they can also be used as applicable in other places and for other vaporous mediums where air-cooled condensers are required.
Air-cooled steam condensers generally consist of a large number of tubes connected in parallel which are densely finned on the air side. The processes taking place in the parallel tubes are principally identical, so it suffices to describe the processes taking place in a single tube.
FIG. 1 shows a schematical cross-sectional view of a known air-cooled condenser comprising a distributing chamber 14, a condensate collecting chamber 16 arranged on a lower level, and these sloping connecting parallel coupled condenser tubes 1 of which only one is shown.
The cross-section of the condenser tubes 1 can be different, and in practice generally condenser tubes 1 with round, elliptical or flat, horse-race track shaped cross-section are used. Inside the condenser tube 1, the condensing steam flows in the direction of arrow 2, and outside the condenser tube 1, perpendicular to the axis thereof, the cooling air flows in the direction of arrows 3.
Since the steam condensing in the condenser tube 1 has a very high heat transfer coefficient, which may be as high as 23.260 W/m.sup.2 K, and the air side heat transfer coefficient is low, between 58 and 81 W/m.sup.2 K, it is advisable to increase the air-side surface in order to improve the efficiency of heat exchange, which is practically implemented by fins 4.
From the direction of arrow 2, not only pure steam enters the condenser tube 1, but also a very low quantity of non-condensable gases, mainly air. One part of the non-condensable gases, as volatile alkalizers and dissociation products, are carried by the steam, while the larger part gets into the steam as a result of leaks in the technological system. In the case of an appropriately implemented and maintained steam turbine, the amount of non-condensable gases--mainly air--entering the condenser with the steam is 0.005 to 0.01% by weight.
Although this quantity in relation to the steam is very low, it becomes obvious later on that the operation of the condenser is very much influenced by the presence of non-condensable gases.
The condensate of the steam and the non-condensable gases must be removed continuously. A pipe 6 and a condensate pump 10 serves to discharge condensate 5 from the condensate collecting chamber 16, while mixture 7 of the non-condensable gases and some remaining steam leaves through an air extraction pipe 8 towards a vacuum pump 9.
In the course of condensation, the change in important physical characteristics, i.e. in the partial pressure of the air, in the steam space under-cooling, and in the steam-side heat transfer coefficient can be neglected as long as 97 to 99% of the steam is not condensed. The only exceptions from this rule are the flow volume and velocity of the steam-air mixture 7, which are inversely proportional with the volume of the condensed steam. Thus for example if 97% of the steam is condensed, the flow volume and the velocity are only 3% of the values at the entry point.
However, in the condensation of the remaining 3%, but especially in that of the last 0.5% of steam, due to the presence of non-condensable gases, significant changes can be experienced in the various parameters, as can be seen in the following table.
______________________________________ Rema
REFERENCES:
patent: 3229722 (1966-01-01), Kritzer
patent: 3556204 (1971-01-01), Dehne
patent: 3710854 (1973-01-01), Staub
patent: 4815296 (1989-03-01), Amir
patent: 4909309 (1990-03-01), Palfalvi et al.
patent: 5323851 (1994-06-01), Abraham
Bodas Janos
Csaba Gabor
Szabo Zoltan
Duong Tho
Energiagazdalkodasi Reszvenytarsasag
Lazarus Ira S.
LandOfFree
Air-cooled condenser does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Air-cooled condenser, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Air-cooled condenser will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1631959