Heat dissipation unit for cross flow type cooling tower and process for making the same

Abstract: The present invention relates to a heat dissipation unit (A) for cross flow type cooling tower with which it is possible to prevent the emission of white vapor without lowering the cooling power of the cooling tower, and also without requiring troublesome routine operation. In order to accomplish the above object, the heat dissipation unit of the present invention comprises filling plates (1) arranged vertically and parallel with each other so as to form spaces therebetween, each of the filling plates (1) having uneven surfaces down which water to be cooled flows when water to be cooled is supplied onto the filling plates (1), and cowl members (2) disposed between neighboring filling plates (1), each of the cowl members (2) including a pair of side plate portions (21) having upper ends and a roof portion (22) connecting the upper ends of the side plate portions (21). The side plate portions (21) of the cowl members (2) are arranged substantially parallel with the filling plates (1) so as to form gaps between the filling plates (1) and the side plate portions (21) of the cowl members (2).

Description: BACKGROUND OF THE INVENTION The present invention relates to a heat dissipation unit, a cross flow type cooling tower and a process for making the heat dissipation unit. The conventional cross flow type cooling tower has a general tendency to emit white vapor from the exhaust port thereof in cold weather, and this white vapor is liable to cause anxiety in the neighboring residents. For example, the neighboring residents are likely to believe that the white vapor pollutes the air and to feel an aversion to the white vapor; or they are likely to mistake the white vapor for smoke from a fire when the vapor reflects red light from, for example, of neon signs. Various attempts have been made in the prior art to prevent the emission of the white vapor from the cross flow type cooling tower. For example, Japanese Patent Application, First Publication No. 3-75495, discloses a cross flow type cooling tower comprising an improved heat dissipation unit. This heat dissipation unit includes a plurality of filling plates vertically arranged parallel with each other so as to make fixed clearance between them, and each of the filling plates has uneven surfaces along which the water to be cooled flows down when the water is sprayed onto the heat dissipation unit. The upper ends of the gaps formed between the neighboring filling plates are closed; or, are covered with cowl members which can be opened, and air passages are formed for emitting only the air from the heat dissipation unit. However, because the exclusive air passages are provided, the above heat dissipation unit has a drawback that the cooling power is lowered in comparison with conventional ones, and it is necessary to enlarge the size of the cooling tower to obtain the necessary cooling power. Furthermore, in the case where the openable cowl members are provided, opening and closing the cowl members requires a great deal of labor, and makes routine maintenance troublesome. JP-A-06 201279 discloses an heat exchanger apparatus. As shown in figure 1 of said document (front view), the heat exchanger apparatus disclosed in JP-A-06 201279 comprises a plurality of filling plates 11 arranged vertically and parallel with each other so as to form spaces therebetween, and dry heat exchanger units B are arranged between parts of the filling plate to form air passages 13 through which air flow passes in a horizontal direction. Each dry heat exchanger unit B has a pair of side walls 20 and 21, and upper and lower cowl portions 15 and 16 connecting the upper and lower ends of the side walls 20 and 21. As shown in figure 2 (plan view) of said document, the filling plates 11 and the side walls 20 and 21 of the dry heat exchanger unit B have waving cross sectional shapes, and narrow water passages 14 are formed between each of the side walls 20 and 21 and the filling plate 11. Because an air flow passing through the dry heat exchanger unit B does not contact with cooling water flowing down through the water passages 14, impurities in the cooling water do not adhere to the outer surface of the unit B, and the outer surface of the unit B is always maintained in a clean state so that heat transfer efficiency from the water passage 14 to the element B can be improved. Therefore, white smoke is effectively prevented from being generated from the exhaust port of the cooling tower. Figure 4 (front view) of said document illustrates a second embodiment, and this embodiment comprises dry heat exchanger units B1 having a height shorter than the unit B. The unit B1 has a pair of inclined lower ends 16a extending toward the filling plates 11, and these inclined lower ends 16a splash water flowing down onto the filling plates 11. Figure 6 of said document explains a method for forming the dry heat exchanger unit B1 by bending a metal plate. SUMMARY OF THE INVENTION It is an object of the present invention to provide a heat dissipation unit and a cross flow type cooling tower with which it is possible to prevent the emission of white vapor without lowering the cooling power of the cooling tower, and also without requiring troublesome routine operation, such as opening and closing operations for cowl members according to changes in the seasons. In order to accomplish the above object, the heat dissipation unit of the present invention comprises the features of claim 1 and the cross flow type cooling tower comprises the features of claim 6. According to the heat dissipation unit of the present invention, hot water to be cooled supplied from above the heat dissipation unit is caught by the roof portions of the cowl members, the water flows into the gaps formed between the side plate portions and the filling plates and it flows down the uneven surfaces of the filling plates. Because the entire amount of water flows down along the uneven surfaces of the filling plates and can contact air horizontally Mowing through the spaces between the filling plates, the hot water can be effectively cooled by heat of vaporization. At the same time, moist air is generated. In contrast, in the water non-supply area of the heat dissipation unit, while the air is flowing through passages surrounded by the filling plates and the cowl members, the air contacts with the dried surfaces of the filling plates which are heated by the hot water contacting the filling plates in the water supply area. Therefore, dry air is generated and it is mixed with the moist air while flowing through the passages, the mixed air which does not contain supersaturated vapor is emitted from the exhaust port of the cooling tower without generating white vapor even when the ambient temperature is low. It is another object of the present invention to provide a process for making a heat dissipation unit in which process the manufacturing cost can be decreased. In order to accomplish the above object, the process for making a heat dissipation unit of the present invention comprises the steps of claim 7. According to the above process, because the cowl member can be easily made of a flat plate, it is possible to manufacture the heat dissipation unit at reduced cost. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross section of a cross flow type cooling tower in which a heat dissipation unit of the present invention is used. Figure 2 is a perspective view of a cowl member of the heat dissipation unit of the present invention. Figure 3 is a cross section of a plate for making the cowl member. Figure 4 is a cross section showing a step for forming projections on the plate. Figure 5 is a cross section showing a step for folding the plate to form the cowl member. Figure 6 is a side view showing a step for installing the cowl member on filling plates. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figures 1 to 6, the best mode of the heat dissipation unit and the cross flow type cooling tower, and the manufacturing method thereof, according to the embodiment of the present invention, will be explained. As shown in Figure 1, the cross flow type cooling tower of this embodiment comprises a heat dissipation unit A, an upper water tank 3 provided above the heat dissipation unit A for spraying hot water to be cooled onto the heat dissipation unit A, and a lower water tank 4 provided below the heat dissipation unit A for receiving the cooled water falling from the heat dissipation unit A. The heat dissipation unit A comprises a plurality of filling plates 1 having a rectangular shape, which are vertically arranged parallel with each other so as to form a constant space therebetween. Each filling plate 1 has uneven surfaces on both faces, and water to be cooled which is sprayed from the upper water tank 3 flows along the uneven surfaces. Between neighboring filling plates 1, cowl members 2 having an inverted gutter shape are horizontally fixed along the upper and lower ends of the filling plates 1. The cowl member 2 consists of a pair of side plate portions 21 having a long rectangular shape and a roof portion 22 connecting the upper ends of both side plate portions 21. The side plate portions 21 of the cowl members 2 are arranged in parallel with the corresponding filling plates I so as to form constant gaps between the filling plates 1 and the side plate portion 21, and these gaps allow passage of water to be cooled and passage of heated air. As shown in Figure 2, a plurality of projections 211 are formed on the outer surface of the side plate portion 21 at a constant intervals along the longitudinal direction of the side plate portion 21, and the projections 211 are bonded to the filling plate 1, for example, by means of an adhesive. Thus, the cowl members 2 are fixed to the filling plates 1 while forming gaps having a constant thickness between the side plate portions 21 and the filling plates 1. The thickness W of the gap is not restricted in the present invention, but is preferably in the range of 2-10 mm, and is more preferably, about 5 mm. The height H of the side plate portion 21 of the cowl member 2 is not restricted in the present invention, but is preferably determined in the range of 20-80 mm according to the size of the cooling tower, and is more preferably, about 50 mm. The roof portion 22 consists of a pair of inclined plate portions 221 abutted against each other to form an overall inverted "V" section so that the water sprayed from the upper water tank 3 can be dispersed by the roof portion 22. Considering the dispersing effects of the roof portion 22, the angle between the two inclined plate portions 221 is preferably in the range of 100-180°, and more preferably, is about 120°. The process for making the above heat dissipation unit A will be explained referring to Figures 3 and 6. First, a plurality of the filling plates I are arranged vertically and parallel with each other so as to make a constant space therebetween to form the skeleton of the heat dissipation unit A. Next, as shown in Figure 3, flat plates 2a formed from a material having plasticity, for example, plastic or metal, are prepared. After softening the plate 2a by heating, the plate 2a is subjected to press forming for forming the projections 211 as shown in Figure 4. The method for forming the projections 211 is not restricted to the press forming, but other forming method, such as vacuum forming, can be also employed. The shape of the projection 211 is not limited to a rectangular shape, but can be modified to other suitable shapes, such as a disc shape or a triangular shape. The plates 2a on which projections 211 are formed are subjected to bending in order to form the cowl member 2 using press dies 5 and 6 as shown in Figure 5. Each of the press dies 5 and 6 has a press faces having an inverted "V" section and a horizontal length being identical with or longer than the cowl member 2, and the width of the press faces is decided according to the width of the cowl member to be formed. Each plate 2a is pressed between the two dies 5 and 6, if necessary, after heating, and is bent to have an inverted "V" section. Furthermore, both ends of the plate 2a, protruding from the dies 5 and 6, are bent until both ends contact with the side face of the male die 5; thus, it is possible to form the cowl member 2 having a pair of the side plate portions 21 and a roof portion 22. As shown in Figure 6, when the cowl member 2 is released from the dies 5 and 6, the bending angle of the roof poution 22 will be widened by springing back. Therefore, if the sectional angle of the press faces of the dies 5 and 6 is 1, which is the sectional angle of the roof portion 22 of the cowl member 2 installed in the heat dissipation unit A, the sectional angle of the roof portion 22 will become 2 being larger than 1, and the distance between both side plate portions 21 will also be widened compared to the parallel condition. Accordingly, by means of inserting the cowl member 2 into the space between the filling plates I while pushing the side plate portions 21 toward each other, it is possible to elastically press the projections 211 against the filling plates 1 after the insertion. Therefore, only by means of applying adhesive agent between the projections 211 and the filling plates 1, it is possible to easily bond the cowl member 2 to the filling plates 1. Furthermore, in the case that the cowl member 2 is formed by bending the flat plate 2a, the cost for manufacturing the heat dissipation unit A can be reduced. The upper water tank 3 comprises a number of spray nozzles on the bottom thereof and shutters 31 provided on each of the spray nozzles for controlling the amount of the water to be sprayed by each nozzle. It is thereby possible to control the area ratio of a water supply area and a water non-supply area on the upper end face of the heat dissipation unit A. By controlling the area ratio of a water supply area and a water non-supply area, it is possible to control the vapor concentration of the air emitted from the cooling tower so as to prevent the emission of the white vapor. In general, the water supply area should be decreased in cold season in which white vapor can be easily generated, and it should be increased in warm season. In the water supply area of the heat dissipation unit A, the hot water to be cooled sprayed by the nozzles of the water tank 3 is caught by the roof portions 22 of the cowl members 2, the water flows into the gaps between the side plate portions 21 and the filling plates 1, and it flows down the uneven surfaces of the filling plates 1. While the water is flowing down along the uneven surfaces of the filling plates 1, the water directly contacts with the air which is horizontally flowing through the spaces between the filling plates 1, and the hot water is cooled by heat of vaporization; thus, moist air is generated. In contrast, in the water non-supply area of the heat dissipation unit A, while the air is flowing through passages surrounded by the filling plates 1 and the cowl members 2, the air contacts with the dried surfaces of the filling plates 1 which are heated by the hot water contacting the filling plates 1 in the water supply area. Therefore, dry air is generated and will be mixed with the moist air while flowing through the passages, and the mixed air which does not contain supersaturated steam is emitted from the exhaust port of the cooling tower without generating white vapor even in the cold seasons. In the above embodiment, the cowl members 2 are disposed at the upper and lower ends of the filling plates 1. Furthermore, instead of the upper water tank 3 shown in Figure 1, water sprinkler pipes can be provided above the heat dissipation unit A as a water supply means. In this construction, it is easy to control the area ratio of a water supply area and a water non-supply area on the upper end face of the heat dissipation unit A.

Claims: A heat dissipation unit comprising : filling plates (1) arranged vertically and parallel with each other so as to form spaces therebetween, each of said filling plates (1) having uneven surfaces down which water to be cooled flows when water to be cooled is supplied onto said filling plates (1) ; first cowl members (2) disposed between upper ends of neighboring filling plates (1) ; and second cowl members (2) disposed between lower ends of neighboring filling plates (1) ; wherein each of said first and second cowl members (2) include a pair of side plate portions (21) having upper ends and a roof portion (22) connecting said upper ends of said side plate portions (21), said side plate portions (21) of said cowl members (2) being arranged substantially parallel with said filling plates (1) so as to form gaps between said filling plates (1) and said side plate portions (21) of said cowl members (2). The heat dissipation unit according to claim 1, wherein said roof portion (22) of said cowl member (2) comprises a pair of inclined plate portions (221) abutted against each other to form an inverted "V" shape. The heat dissipation unit according to claim 1, wherein each side plate portion (21) of said cowl member (2) is fixed to said filling plate (1) by means of spacers (211). The heat dissipation unit according to claim 1, wherein each side plate portion (21) of said cowl member (2) has at least a protrusion (211) projecting towards said filling plate (1) and said protrusion (211) is fixed to said filling plate (1). The heat dissipation unit according to claim 1, wherein the thickness (W) of said gap formed between said side plate portions (21) and said filling plate (1) is in the range of 2-10 mm, and the height of said side plate portion (21) of said cowl member (2) is in the range of 20-80 mm. A cross flow type cooling tower comprising : a heat dissipation unit (A) having upper and lower ends ; water supply means (3) for supplying water to be cooled to said upper ends of said dissipation unit (A) so as to form water supply areas and water non-supply areas on said upper ends of said heat dissipation unit (A) ; and a water receiver (4) for collecting cooled water flowing down from said lower ends of said heat dissipation unit (A) ; wherein said heat dissipation unit (A) comprises : filling plates (1) arranged vertically and parallel with each other so as to make spaces therebetween, each of said filling plates (1) having uneven surfaces down which water to be cooled flows when water to be cooled is supplied onto said filling plates (1) ; first cowl members (2) disposed between upper ends of neighboring filling plates (1) ; second cowl members (2) disposed between lower ends of neighboring filling plates (1) ; wherein each of said first and second cowl members (2) include a pair of side plate portions (21) having upper ends and a roof portion (22) connecting said upper ends of said side plate portions (21), said side plate portions (21) of said cowl members (2) are arranged substantially parallel with said filling plates (1) so as to from gaps between said filling plates (1) and said side plate portions (21) of said cowl members (2) so that water supplied from said water supply means flows down along said filling plates (1) positioned under said supply areas. A process for making a heat dissipation unit (1) comprising the steps of : arranging filling plates (1) in parallel with each other so as to form spaces therebetween ; folding plates (2a) to form first and second cowl members (2) having a pair of side plate portions (21) and a roof portion (22) connecting said side plate portions (21) to each other ; providing spacing protrusions (211) on an outer surface of each of said side plate portions (21) of said cowl members (2) ; inserting said first cowl members (2) between upper ends of said filling plates (1) and fixing said spacing protrusions (211) of said first cowl members (2) to said filling plates (1) so as to form gaps between said filling plates (1) and said side plate portions (21) of said first cowl members (2) ; and inserting said second cowl members (2) between lower ends of said filling plates (1) and fixing said spacing protrusions (211) of said second cowl members (2) to said filling plates (1) so as to form gaps between said filling plates (1) and said side plate portions (21) of said second cowl members (2) ; wherein said steps of inserting said first and second cowl members (2) are performed while elastically deforming said first and second cowl members (2) to reduce the width of the space between said side plate portions (21) so that said side plate portions (21) move toward said filling plates (1) after said inserting step.

Inventors: GOTO OSAMU, USUI MASAHIRO, YAMAMOTO SHIGEHIRA, GOTO, OSAMU, USUI, MASAHIRO, YAMAMOTO, SHIGEHIRA
Applicants: ISHIKAWAJIMA HARIMA HEAVY IND, ISHIKAWAJIMA-HARIMA HEAVY INDUSTRIES CO., LTD.
Application year: 1996
Main classification: F28C1
IPC codes: F28F25, F28C1