NZ209149A

NZ209149A - Drift eliminator for cooling tower

Info

Publication number: NZ209149A
Application number: NZ209149A
Authority: NZ
Inventors: P A Frohwerk
Original assignee: Ceramic Cooling Tower Co
Priority date: 1984-04-23
Filing date: 1984-08-08
Publication date: 1987-02-20
Also published as: IT8448780A0; IT8448780A1; GB2157818B; GB8429149D0; IT1179419B; GB2157818A; AU3134684A; FR2563330A1; DE3429086A1; ZA845466B

Description

<div class="application article clearfix" id="description"> v. .-■<*&? , ■ ;"S ;209149 ;Priority Datejs): ... ?Jfr ;Complete Specification Filed; ;CIms: ;...... . ;Paaligation Date: ...... j2;Q. F£9.1??/.'. ;P.O. Jcurnjl, ;n.^atentoffice. -8 AUG 1984 ;RECElVgD_ ;Patents Form No. 5 ;NEW ZEALAND PATENTS ACT 1953 ;COMPLETE SPECIFICATION ;"MULTI-CELL TILES WITH OPENINGS FOR USE IN A LIQUID COOLING TOWER" ;-3ry WE CERAMIC COOLING TOWER COMPANY, incorporated in the State of Texas/ U.S.A. of 4100 International Plaza, ;Tower No. 1., Suite 900, Fort Worth, Texas 76109 U.S.A. ;hereby declare the invention, for which -iVwe pray that a patent may be granted to me/us, and the method by which it is to be performed, to be particularly described in and by the following statement:- ;-1- ;(folfowed by page 1 A.^ ;209149 ;Background ;This invention relates to drift eliminators for cooling towers. ;Examples of cooling towers are described in New Zealand Patent Specification No. 202,488 and U.S. Patent No. 4,382,046. Cooling towers are used to cool liquid by contact with air. The liquid is allowed to x ;flow downwardly through a heat and mass transfer section in the tower, and a counter current flow of air is drawn through the falling liquid by various means. A common application of liquid cooling towers is for cooling water (dissipating waste heat) used in electrical generating and process plant and industrial and institutional air conditioning systems. ;The water is broken, up into droplets in the heat and mass transfer section, and some of the water becomes entrained in the air. Accordingly, cooling towers conventionally include a drift eliminator through which the air passes before it leaves the tower in order to remove the droplets from the air. ;Most drift eliminators for cooling towers are inertial impact separators. Such drift eliminators provide obstructions to the flow of air, and water which is carried by the air is carried by its inertia into contact with the obstructions. ;Two conflicting considerations must be kept in mind when designing a drift eliminator -- the amount of water loss or drift, and air resistance. Increasing the obstruction to air flow in order to increase water separation also increases the air resistance of the drift eliminator. The efficiency of a cooling s^tower is a function of the air resistance or pressure drop of he tower. Although the air flow through a tower with high air resistance could be increased by using a larger horse power fan, this would result in increased equipment and energy cost. ;la ;On the other hand, if the air resistance of the drift eliminator is reduced, the water loss will generally increase. ;Many types of prior art drift eliminators have been used in cooling towers. Such drift eliminators commonly have a zig-zag or air foil configuration in which the air is forced to follow a zig-zag or curved path. In prior art drift eliminators the first portion of the air passage is generally inclined from the vertical or provides some resistance to upward air flow. It is believed that this resistance directs some of the air away from the air passage and increases the air resistance of the eliminator. Also, it is believed that in some of the designs the streamlined flow of air forms eddies under high air speed in the vacinity of obstructions in the eliminator which interfere with the inertial impact of the water on the obstruction. ;Summary of the Invention ;The invention provides a drift eliminator with improved drift efficiency and lower air resistance. The drift eliminator includes a plurality of spaced-apart parallel vanes, each vane having a vertical lower portion, an intermediate or impact portion which extends at about 45° from the vertical, and an upper portion which extends substantially vertically. The vertical lower portions of the vanes channel the upwardly flowing air toward the impact portions, and the inclined impact portions provide a substantial impact area for the water. The upper portion provides another impact area and redirects the air so that it flows substantially vertically when it leaves the eliminator. ;•■Ppfe/ ;m ;-■'A ;- / ;" -■-¥ ;■j ;4l|# ;Description of the Drawing ;4£l> i "'i? ;O ;O ;G ;1 ;a ;The invention will be explained in conjunction with an illustrative embodiment in which — ;Fig. 1 is a perspective view, partially broken away of a cooling tower equipped with a drift eliminator in accordance with the invention; ;Fig. 2 is a perspective view, partially broken away of a portion of the drift eliminator; ;Fig. 3 is a side elevational view of a portion of the drift eliminator; ;Fig. 4 is an enlarged side elevational view of one of the vanes of the drift eliminator; and ;Fig. 5 is a fragmentary perspective view of one of the vane holders of the drift eliminator. ;Specific Embodiment ;Fig. 1 illustrates a coolingtower10 of the type described in U.S. Patent No. 4,422,983. The cooling tower includes a basin 11, a rectangular side wall 12, and a top 13. A heat and mass transfer section 14 is supported above the basin, and a water distribution assembly 15 is supported above the heat and mass transfer section. The water distribution assembly includes a header pipe 16 and a plurality of lateral pipes 17 which extend from opposite sides of the header pipe. The lateral pipes are equipped with spray nozzles or orifices for distributing the water over the heat and mass transfer section. ;As described in U.S. Patent Nos. 4,422,983 and 4,382,046, the preferred embodiment of heat and mass transfer section comprises layers of extruded clay tiles. As water flows downwardly through the tiles, air is drawn upwardly through the tiles by a fan 19 which is mounted in a fan opening in the roof. ;" * 7 ~ ' • /. ' ;s. m o -/ 2 A drift eliminator assembly 20 is supported between / . • .the water distribution assembly and the fan to remove the water droplets and vapor from the air before the air leaves the cooling tower. In the embodiment illustrated, the drift eliminator is supported on top of the lateral pipes 17, but a separate support can be used if desired. The portion of the drift eliminator in the lower right portion of Fig. 1 has been removed to show the water distribution pipes and the heat and mass transfer section. The drift,eliminator 20 includes a plurality of vanes • or blades 22 (Fig. 2) which are held in a fixed relationship by retainer rails 23 (Figs. 1 and 5) which extend transversely with respect to the vanes. Referring to Fig. 5, each retainer rail 23 is provided with slots 24 which have the same general shape as the vanes, and the vanes are inserted into the slots in the rails. The retainer rails may be spaced about twp feet apart. Each of the vanes includes a vertically extending lower portion 26, an inclined impact portion 27 , and an upper portion 28, In the preferred embodiment the impact portion 27 extends at an angle of 45° from the vertical, and the upper' portion 28 extends at an angle of 7-1/2° from the vertical. The included angle A (Figs. 3 and 4) between the lower portion 26 and the impact portion 27 is therefore 135°, and the included angle B between the impact portion and the upper portion 28 is 127-1/2°. The angle C between the upper portion and the vertical is 7-1/2°. The spacing between adjacent vanes and the dimensions of the vanes are such that the drift eliminator provides high drift efficiency and relatively low air resistance. In the preferred embodiment, the spacing D (Fig. 3) between the vertical lower portions of adjacent vanes is from about 1 to 1-1/2 inches. The height E (Fig. 4) of each lower portion is 1/2 inch, the horizontal component F of the length of the impact portion is three inches, and the height G of the upper portion is 1-2 inch. The length of - da, U" I h- y thie impact portion is F/cos(A-90°) or 4.24 inches. The maximum • thickness T of each blade should be no more than 0.05 inch. The preferred material of the vanes is polyvinylchloride. The retaining rails 23 hold the vanes in fixed positions so that the respective portions 26-28 of the vanes extend parallel. As the air is drawn upwardly by the fan and approaches the drift eliminator, the air flows into the vertical channels provided by the parallel lower portions 26 without any significant turbulence. The air is then directed by the vertical channels toward the impact portions 27. The horizontal component F of each impact portion extends substantially beyond the width of the vertical channel and provides a substantial impact area for the water which is entrained in the air. As the air flows upwardly between adjacent impact portions, the angled upper portions 28 provide additional impact areas. The upper portions also serve to redirect the air so that the air is flowing substantially vertically and in the direction of the fan when it leaves the drift eliminator. Although in the preferred embodiment the upper portions are angled slightly beyond the vertical, i.e., 7-1/2 0, the upper portions could also extend vertically without a significant decrease in drift efficiency. The 1 to 1-1/2 inch spacing between the lower portion of the vanes optimizes the competing considerations of component economics, drift efficiency, and air resistance. If the spacing is increased to over two inches, the drift becomes.unacceptable but the air resistance remains about the same as for the one inch spacing. If the spacing is decreased below one inch, the air resistance becomes unacceptably high. While in the foregoing specification a detailed description of a specific embodiment of the invention has been set forth for the purpose of illustration, it will be understood that many of the details herein given may be varied considerably by those skilled in the art without departing from the spirit and scope of the invention. — i" — </div>

Claims

<div class="application article clearfix printTableText" id="claims"> 209149 ' WHAT WE CLAIM IS;

1. A drift eliminator for a cooling tower comprising a plurality of spaced-apart parallel vanes, each vane; having a substantially vertical lower portion and an inclined portion extending angularly from the lower portion and an upper portion extending angularly from the inclined portion, the included angle between the upper portion and the inclined portion being less than the included angle between the lower portion and the inclined portion1.

2. The drift eliminator of claim 1 in which the upper portion of each vane extends substantially vertically upwardly from the inclined portion.

3. The drift eliminator of claim 1 in which the inclined portion of each vane extends at an angle of substantially 135° from the lower portion.

4. The drift eliminator of claim 3 in which each vane includes an upper portion which extends at an angle of substantially 127-1/2° from the inclined portion,

5. The drift eliminator of claim 1 in which the lower portions of adjacent vanes are spaced 1 to 1-1/2 inches apart.

6. The drift eliminator of claim 1 in which the lower portion of each vane has a height of. substantially 1-1/2 inch.

7. The drift eliminator of claim 6 in which the ; inclined portion of each vane extends at an angle of substantially 135° from the lower portion.

8. The drift eliminator of claim 7 in which the length of the inclined portion of each vane is substantially 4 .2 inches . t 209149

9. The drift eliminator of claim 8 in which each vane includes an upper portion which extends angularly from the inclined portion, the included angle between the upper portion and the inclined portion being less than the included angle . between the lower portion and the inclined portion.

10. The drift eliminator of claim 9 in which the upper portion of each vane has a length of substantially two inches.

11. The drift eliminator of claim 10 in which the inclined portion of each vane extends at an angle of substantially 135° from the lower portion and the upper portion of each vane extends at an angle of substantially 127-1/2° from the inclined portion.

12. The drift eliminator of claim 9 in which the lower portions of adjacent vanes are spaced 1 to 1-1/2 inches apart..

13. A drift eliminator as claimed in claim 1 substantially as herein described with reference to the accompanying drawings. BALDWIN, SON & CAaiEY ATTORNEYS FOR THE APPLICANTS: </div>