US3352547A

US3352547A - Cooling towers

Info

Publication number: US3352547A
Application number: US389054A
Authority: US
Inventors: Parkinson Graham Charles
Original assignee: L T MART CO Ltd
Current assignee: L T MART CO Ltd
Priority date: 1963-09-19
Filing date: 1964-08-12
Publication date: 1967-11-14
Anticipated expiration: 1984-11-14
Also published as: GB1076278A

Description

Nov. 14, 1967 G. c. PARKINSON 3,352,547

COOLING TOWERS Filed Aug. 12, l964 2 Sheets-Sheet l Inventor G. C. PAR K\NSON ttorneys Nbv. 14, 1967 c5. c PA'RKINSON COOLING TOWERS 2 Sheets$heet 2 Filed Aug. 12, 1964 (3.6. PARK\NSON United States Patent Delaware 12, 1964, Ser. No. 389,054

Filed Aug. Claims priority, application Great Britain, Sept. 19, 1963, 36,938/ 63 4 Claims. (Cl. 261-112) ABSTRACT OF THE DISCLOSURE A water cooling tower comprising a tapering shell provided with a vertical shroud ring onto which water is deflected to form a curtain behind air inlets at the bottom of the tower.

This invention relates to water cooling towers of the kind which are commonly used for cooling the water circulated to the condensers of steam turbines in electric generating stations and which comprise an upwardly tapering shell, usually of hyperbolic shape, having an open top and an air inlet opening around its bottom and containing a packing over which the water being cooled splashes downwards and a draught of air produced by convection flows upwards.

To ensure that adequate cooling of the water takes place when the temperature of the atmospheric air which flows upwards through the tower is fairly high, it is important that the packing should be designed so that the water is broken up into small droplets to present a large surface area to the air flowing past it in countercurrent. The diificulty then arises however that in Winter if the air temperature drops substantially below freezing point, the small droplets of water will freeze and the packing rapidly becomes seriously obstructed. The tendency for this freezing to take place occurs mainly around the outside of the packing just inside and immediately above the air inlet opening which extends around the bottom of the shell. This is because it is here that the air temperature is lowest.

To overcome this difliculty, it has previously been proposed to fit a ring water main provided with a number of outlets at intervals around it inside the shell just above the opening at its bottom. Normally all the water to be cooled passes through the pacln'ng and is broken up into droplets in contact with the air. Under conditions where icing is likely to occur however, some of the water is supplied to the ring main and this water flows directly from the main and forms a curtain extending over the inlet opening at the bottom of the shell. The water in this curtain is not broken up into small droplets and therefore its tendency to freeze is not very great. In any case, if it does freeze, it does not obstruct the packing because it falls from the curtain directly into the pond in the bottom of the cooling tower where it mixes with the other water at a slightly higher temperature and is then pumped back to the turbine condensers.

With this arrangement it is not satisfactory to operate the cooling tower with water supplied to the ring main under all conditions, and as already stated, the supply to the ring main is only therefore turned on when conditions Warrant it. There is a tendency therefore for the operators of the cooling tower not to turn on the water supply until some substantial amount of icing has already occurred and it is then too late even when the water supply to the ring main is turned on to get rid of the ice which has already started to form. Once ice has started to form it tends to accumulate very rapidly and it has been found, for this reason, that the known arrangement with the ring main is not entirely satisfactory in practice.

According to the present invention, a cooling tower of the kind described is provided with a packing consisting of rings of concentric louvres which are arranged in layers extending around the shell and at least the outer ones of which are shaped or orientated in such a way that they deflect the falling water outwards towards the shell, and a shroud ring is provided extending around the inside of the lower part of the shell just above the opening, the shroud ring having a substantially vertical inside surface and a sharply defined lower edge formed so that water deflected outwards by the louvres runs down the inside surface of the shroud ring and flows from the lower edge of the ring with a smooth flow so that it is not appreciably broken up and forms a curtain of water over the opening.

The curtain of water formed over the opening at the bottom of the shell in this way has been found to have the same effect in inhibiting icing of the packing under low temperature conditions as the curtain formed by water supplied from a ring main. With the present invention however the curtain is formed automatically whenever the cooling tower is in operation and the chances of human error destroying the effectiveness of the arrangement are overcome. The water which forms the curtain has already passed through some of the packing before it reaches the inside surface of the shroud ring and is therefore partly cooled. It is found therefore that the presence of the curtain does not appreciably adversely affect the performance of the cooling tower in the summer when the temperature of the air flowing through it is higher.

The provision of the shroud ring appears a simple expedient, but it has been found to be completely effective and it overcomes difiiculties which have been experienced with cooling towers over a period of many years.

The shells of cooling towers of the kind described are commonly constructed of reinforced concrete and the bottom edge of the shell above the opening extending around the base of the shell is usually formed with a square cut bottom surface. In this case, the shroud ring may be formed of concrete at the same time as the shell itself is formed, but if this is done the bottom inside edge of the shell at the lower end of the shroud ring must be formed with a very acute angled corner and this is difl'lcult to do with concrete and make the corner sufiiciently sharply defined to ensure that the water runs off it to form a continuous curtain. Indeed if the edge is sufiiciently sharply defined, it will tend to break off and the shroud ring will no longer be effective. It is usually necessary therefore to cast in a tip of metal or other material which is less brittle than concrete. The shroud ring is preferably therefore made of plywood or other thin sheet material fitted inside the bottom of the concrete shell. When this is done, the taper of the inside surface of the concrete shell continues to its very bottom edge which facilitates its construction and the shroud ring in the form of a thin-walled cylinder is fitted inside the bottom of the shell and is attached to the inside surface of the shell.

The packing which deflects the water outwards against the inside surface of the shroud ring may be of the known kind consisting of a series of rings of louvres one above the other supported on bearers which extend radially from the centre of the tower. Each of the louvres is of right-angled triangular section made by splitting a batten diagonally and each louvre is arranged with the hypotenuse substantially vertical or sloping slightly inwards from the bottom to its top so that its top surface slopes outwards and downwards. The louvres in adjacent layers are staggered from each other so that water collected on the sloping surfaces of the louvres in one layer tends to run oif the surface towards the tower shell and to f ll from the bottom edges of the louvres onto the sloping surfaces of the louvres nearer the shell in the next layer. It is in this Way that the drops of water are caused to migrate outwards. When the drops reach the smooth surface of the shroud ring they coalesce and run down the inside surface of the shroud ring with a lamina flow and the water runs from the bottom edge of the shroud ring in a curtain which is continuous or at least substantially so.

An example of a water cooling tower constructed in accordance with the invention is illustrated in the accompanying drawings in which:

FIGURE 1 is a vertical diametric section through the cooling tower; and,

FIGURE 2 is a perspective sectional detail of a part of the tower to a much larger scale.

The tower has a conventional reinforced concrete shell 1 supported from a concrete footing 2 by a series of legs 3 which are spaced apart around the bottom of its periphery. As is shown most clearly in FIGURE 2, the shell 1 terminates at the tops of the legs 3 in a bottom edge 4 and between this bottom edge and the footing 2 is a main air inlet opening which extends around the whole of the bottom of the tower in between the legs 3. When the tower is in use, a flow of air is induced by convection inwards through the opening around the bottom of the periphery of the tower and out through its open top 5.

The water itself is cooled in a conventional manner by means of a packing 6 supported on reinforced concrete beams 7 extending between columns 8. The water is supplied to the packing through a number of radially extending pipes 9 parts of two opposite ones of which are shown in FIGURE 1 and the water issues from these pipes in a large number of sprays from small nozzles 10 shown in FIGURE 2. The water spraying from the nozzles 10 falls downwards through the packing 6 which breaks it up into small droplets so that it is brought into close contact with the stream of air flowing upwards through the tower. The water, which is thus cooled, collects in a pond 11 bounded by the footing 2 and from this pond it is pumped back to the condensers of the steam turbine or wherever else it may be required.

A part of the packing 6 is shown in detail in FIGURE 2. The effective part of the packing which breaks the water up into droplets consists of a very large number of rings made of timber strip 12. The rings 12 are supported at intervals along their lengths by radially extending timber supports 13. Parts of one vertical row of supports 13 are shown in FIGURE 2 and some of the rings 12 supported by them are also shown. There are however rings 12 at equally spaced intervals along all of the supports 13 and there are thus a number of closely spaced concentric rings on each of the supports 13 and a number of layers of rings one above the other. The water sprayed from the nozzles 10 fixed to the radial pipes 9 falls on to the top surfaces of the top layer of rings 12. Each of the rings 12 is built up from a number of lengths of timber strip formed by cutting a rectangular timber batten twice as wide as it is thick diagonally to form two triangular louvres. The rings 12 are arranged with the bisector of the smallest angle of the triangular section vertical, that is with the hypotenuse sloping slightly inwards so that their top surfaces slope downwards and outwards and therefore the water falling onto the top layer of rings 12 tends to be diverted outwards by the top surfaces of these rings and the water then falls onto the layer of rings below. These rings tend to divert the Water still further outwards so that at the periphery of the tower the water follows the slope of the shell 1 outwards. In passing through the packing formed by the rings 12, the water is broken up into small droplets.

As shown in FIGURE 2, the supports 13 are themselves supported by timber uprights 14 one of which is shown in FIGURE 2 and these timber" uprights extend between the beams 7 which are made of reinforced concrete and they are supported by horizontal runners 15. The outermost ring of uprights 14 one of which is shown in FIGURE 2,. have their upper ends supported by a batten 16 which is fixed to the inside face of the shell 1.

A shroud ring 17 formed by a series of flat plywood sheets is fixed to the inside face of the shell 1 by means of a

framework comprising battens

18 and 19 and uprights 21). The join between the top of the shroud ring 17 and the inside face of the shell 1 is sealed by a copper flashing 21.

As the water from the nozzles 11 is diverted outwards through the rings of louvres 12, the water leaving the nozzles 10 near the outer ends of the pipes 9 eventually gets diverted to the very periphery of the packing onto the inside face of the shroud ring 17. The shroud ring 17 is made of plywood only A inch thick and 8 feet high and the water runs down its smooth inside face and leaves in a steady unbroken stream from its comparatively sharp bottom edge 22. This water forms a curtain over the open ing below the bottom edge 4 of the shell and this water falls into the pond 11.

We have found that this curtain of water greatly inhibits the icing of the packing 6 especially around its outside where this icing commonly takes place when the temperature of the air entering the opening at the bottom of the cooling tower is below freezing point. Although there is a steady stream of water from the bottom edge 22 of the shroud ring 17, this curtain is sufficiently discontinuous to allow the air to flow in through the opening and up through the shell 1 in the usual way.

I claim:

1. In a water cooling tower. comprising an upwardly tapering shell having an open top and means forming an air inlet opening around its bottom, and, within said shell, a packing over which water being cooled splashes downwards and a draught of air produced by convection flows upwards, the improvement comprising a shroud ring extending around the inside of the bottom of said shell just above said opening, said shroud ring including a substantially vertical inside surface terminating in a sharply defined lower edge and wherein said packing. comprises rings of concentric louvres, means supporting said louvres in layers one above the other extending around said shell and at least the outer ones of said louvers being arranged to deflect the falling water outwards onto the inside surface of said shroud ring so that it runs vertically down said inside surface and flows smoothly in the same direction from said lower edge of said ring to form a substantially continuous curtain of water over said opening.

2. A water cooling tower as claimed in claim 1, wherein said shroud ring comprises a cylinder of thin sheet material and means fitting said cylinder within the inside of the bottom of said shell. 7

3. A water cooling tower as claimed in claim 1, wherein said means supporting said louvres comprise bearers extending radially from the centre of said shell, and each of said louvres being of right-angled triangular section with its hypotenuse directed inwards and its top surface sloping outwards and downwards.

4. A water cooling tower as claimed in claim 3, wherein said louvres in adjacent layers are staggered from each other whereby water collected on the sloping surfaces of said louvres in one layer tends to run ofi said surface towards said shell and fall from said louvres onto said sloping surfaces of louvres nearer said shell in a lower layer of said louvres.

(References on following page) 6 References Cited OTHER REFERENCES Rish et 211.: Design and Selection of Hyperbolic Cool- FOREIGN PATENTS ing Towers, Combustion, January 1960 (pages 42, 46

512,035 11/1930 Germany. and 47 ,259 11/1920 Great Britain. HARRY B. THORNTON, Primary Examiner.

473,900 10/1937 Great Britain. E. H. RENNER, Assistant Examiner.

Claims

1. IN A WATER COOLING TOWER COMPRISING AN UPWARDLY TAPERING SHELL HAVING AN OPEN TOP AND MEANS FORMING AN AIR INLET OPENING AROUND ITS BOTTOM, AND, WITHIN SAID SHELL, A PACKING OVER WHICH WATER BEING COOLED SPLASHES DOWNWARDS AND A DRAUGHT OF AIR PRODUCED BY CONVENCTION FLOWS UPWARDS, THE IMPROVEMENT COMPRISING A SHROUD RING EXTENDING AROUND THE INSIDE OF THE BOTTOM OF SAID SHELL JUST ABOVE SAID OPENING, SAID SHROUD RING INCLUDING A SUBSTANTIALLY VERTICAL INSIDE SURFACE TERMINATING IN A SHARPLY DEFINED LOWER EDGE AND WHEREIN SAID PACKING COMPRISES RING OF CONCENTRIC LOUVRES, MEANS SUPPORTING SAID LOUVRES IN LAYERS ONE ABOVE THE OTHER EXTENDING AROUND SAID SHELL AND AT LEAST THE OUTER ONES OF SAID LOUVRES BEING ARRANGED TO DEFLECT THE FALLING WATER OUTWARDS ONTO THE INSIDE SURFACE OF SAID SHROUD RING SO THAT IT RUNS VERTICALLY DOWN SAID INSIDE SURFACE AND FLOWS SMOOTHLY IN THE SAME DIRECTION FROM SAID LOWER EDGE OF SAID RING TO FORM A SUBSTANTIALLY CONTINUOUS CURTAIN OF WATER OVER SAID OPENING.