RU2462675C1 - Design of ejection cooling tower, and method of organisation of heat and mass exchange process - Google Patents

Abstract

FIELD: power industry. ^ SUBSTANCE: ejection cooling tower includes housing made in the form of polygonal prism, which is installed on supports based together with water collecting tray on support frame, and in upper part of housing there mounted is exhaust passage consisting of confuser and diffuser having a manhole, below which there located is ladder and upper technological platform enveloping on the outside the housing top, inside which on the same level there installed is drop catcher. Housing bottom has the shape of inverted truncated pyramid the side surface of which is formed with inclined water drains with water-air ejectors installed on them, and water distributing system located immediately below them. Inlet openings of ejectors are holes made in planes of water drains along the outline of inner edges of which there mounted are wind partitions enclosing the space from water drains to water collecting tray some part of surface of which on the outer side from wind partitions is fully closed with grating forming the lower technological platform. Each ejector has vortex jet atomiser mounted in the centre of air inlet opening along the outline of which above water drain there welded is water baffle ring, and ejection channel is installed coaxially with atomiser so that between water drain plane and the latter there is drain gap with height of 3-5 mm. Ejection channel has the diameter which is larger by 50-60 mm than diameter of water baffler ring and installed so that annular gap is formed between them. ^ EFFECT: invention allows improving cooling capacity of cooling tower, reducing material consumption of the design and improving the conditions of the unit maintenance. ^ 7 cl, 3 dwg

Description

The invention relates to industrial power systems and can be used as coolers for circulating water and other liquid media in various industries.

Known ejection cooling tower comprising a housing, a water catcher, air inlet and air outlet shafts. In the upper and lower parts of the body are installed main cooling collectors with ejection nozzles that spray water and eject air. The casing has four air shafts, inside the casing there is a vertical baffle and pre-cooling collectors with nozzles facing the outlet openings up, which together with the vertical baffle set the direction of movement of the exhaust air (see patent RU No. 2187058 C1, F00C 1/00, 08/10/2002 )

Such a cooling tower has the following main disadvantages.

Difficult maintenance of nozzles and collectors pre-cooling and other components inside the unit.

The exhaust air outlet area is located in close proximity to the inlet of the upper air shaft.

The orientation of the nozzles on the two manifolds inside the housing towards the water trap increases the water loss associated with the droplet drop.

The excessive consumption of electricity to increase the volume of ejected air associated with the outflow of part of it from the tower in places where the perimeters of round flares do not touch the flat walls of the air shaft.

Closest to technical solutions is an ejection tower containing a housing with air inlet ejector windows made in the form of a longitudinal channel and located along the upper edge of the tower, a collector with nozzles pointing down (see patent RU No. 2166163, C2, F28C 1/00, 27.04 .2001) is a prototype.

This cooling tower also has a number of significant drawbacks.

To provide a water seal in a rectangular ejection channel, mutual overlap of flares is 60-70%. Studies show that an overlap of more than 30% leads to the destruction of flares, which reduces the ejection coefficient and degrades the cooling capacity of the tower.

The installation of nozzles in the upper part of the tower reduces the available head in front of the nozzles by the height of the tower.

When torches are directed downward, the nozzle “shoots through” the entire volume of a low cooling tower almost instantly, while the process of heat and mass transfer in cooling towers to complete saturation of the air takes at least 4-5 seconds, which requires an increase in the unit height to several tens of meters. As a result, the material consumption of the structure increases and the required pressure increases, accompanied by an excessive consumption of electricity.

When the ejection channels are located in close proximity to the exhaust channel of the cooling tower, there is a constant suction of exhaust moist air and its continuous recirculation, which worsens the cooling capacity of the unit.

The objectives of this invention are: to increase the cooling capacity of the tower; reduction of energy consumption of the process and material consumption of the structure; Improving the maintenance conditions of the unit.

To solve the tasks, a new design of the ejection cooling tower and a method for organizing the heat and mass transfer process are proposed.

The present invention allows to achieve a depth of cooling of the circulating water to the level of air temperature using a wet thermometer plus 4-5 °. Reduce the material consumption of the structure, since the orientation of the ejectors from the bottom up does not require a large tower height. Reduce the energy intensity of the process due to a decrease in the required pressure to 0.2-0.25 MPa. Improve unit maintenance convenience.

A schematic diagram of a cooling tower is shown in figures 1-3. Figure 1 presents a longitudinal section of the tower, figure 2 is a cross section in figure 1.

According to the scheme, the cooling tower has a housing 1 in the form of a multifaceted prism mounted on supports 2, based together with a drainage pan 3 on the supporting frame 4. The base of the case has the shape of an inverted truncated pyramid, the edges of which are weirs 5 made of metal sheets. In the planes of the spillways, holes are made, over which water-air ejectors are mounted. The number of ejectors is determined by the nozzle performance at a given operating pressure and the total flow rate of the cooled water through the cooling tower. The water distribution system is located directly under the spillways and includes several risers 6 and collectors 7 in the form of closed polyhedrons that repeat the shape of the body and are located concentrically relative to its axis. The space between the weirs and the drainage pan is closed by the wind partitions 8 installed along the contours of the inner edges of the weirs. A door is made in one of the wind partitions. Outside of the wind partitions, the pallet is covered with a continuous flooring, forming the lower technological platform 10, In the upper part of the cooling tower has an exhaust channel for the exit of the steam-air mixture, consisting of a confuser 11 and a diffuser 12. At the base of the confuser, the upper technological platform 13 encircling the top of the housing from the outside. A droplet eliminator 14 is installed inside the casing at the same level. A ladder 15, which is adjacent to the hatch in the diffuser wall, rests on the upper technological platform (the hatch is not shown in the diagram).

When installing a cooling tower over a recessed catchment basin, there is no catchment pan in its design.

The design of the water-air ejector is presented in figure 3.

Round holes are made in the weir planes. In the center of each hole there is a special jet-vortex nozzle 16 oriented upward along the axis of the ejector with a slope towards the axis of the tower.

On the contour of each hole, which is also the input window of the ejector, a water-discharge ring 17 is welded on top of the spillway.

The ejection channel 18 is installed coaxially with the nozzle and has a drainage gap with a spillway with a height of 3-5 mm. Studies show that not only the presence of a water seal, but also its location significantly affects the magnitude of the ejection coefficient. In this regard, the height of the ejection channel, depending on the diameter of the ejector inlet window and the angle of the nozzle opening, is set to ensure a guaranteed water seal between the torch and the solid wall of the ejection channel in an area 150 mm wide from the upper edge of the channel. The diameter of the ejection channel is 50-60 mm larger than the diameter of the water-retaining ring, as a result of which an annular gap of 25-30 mm wide remains between them. Ejectors are arranged in rows symmetrically relative to the collectors of the water distribution system. In order to exclude the destruction of the torches of the dispersed liquid of neighboring ejectors when they intersect at a closer distance between them, the installation step of the ejectors is taken equal to the diameter of the ejection channel plus 50-100 mm.

The cooling tower is very convenient for maintenance. From the surface of the lower technological platform 10, free access to ejectors and elements of the water distribution system is provided even during operation of the unit, as weirs 5 protect personnel from falling rain. Penetration into the body of the tower is carried out from the surface of the same platform through the door 9. In the volume of the exhaust channel, personnel enter the ladder 15 through the manhole in the wall of the diffuser.

This design of the cooling tower defines a new way of organizing the heat and mass transfer process.

Heated water under pressure is supplied to the collectors 7 of the water distribution system, from which it is pushed through the nozzles 16 into the ejection channels 18, in the volume of which the required amount of atmospheric air is sucked, after which, in the active zone of the tower, during heat transfer from the heated water to the cooler air and partial evaporation of water, it is cooled.

The water film formed in the area of the hydraulic seal slides down the walls of the ejection channel, and then, washing the water baffle ring 17, flows through the drainage gap along the inclined spillway 5. Thus, water losses from the ejectors are excluded when they are oriented upward.

After the ejectors, the flows of dispersed liquid together with the ejected air move along curved trajectories with a slope to the axis of the tower. In the upper part of the tower there is a multilateral frontal collision of flows, accompanied by repeated fragmentation and soaking of drops in the process of chaotic movement, that is, the flow seems to freeze in volume for some time. After the collision, the stream falls down in the form of rain. At the same time, some of the ejected air saturated with steam leaves the collision zone through the exhaust channel into the atmosphere. Another part of the air carried away by the rain moves down. At the surface of the liquid in the drain pan 3, the air turns and, distributed in volume, rushes into the exhaust channel of the tower, "sifting" between the drops of freely falling rain.

With this method of organizing the heat and mass transfer process, the phase contact time increases to 5 or more seconds. In the direction of flow, three zones of intense heat and mass transfer can be distinguished. The first is in the regime of active turbulence in the area from ejectors to flow collisions. The second is the zone of collision of flows in the regime of chaotic soaring of drops. The third is the area of free-falling rain in counter-current mode with ascending air currents.

Thus, in addition to the rational scheme of the heat and mass transfer process, which significantly increases the phase contact time, other factors provide high efficiency of the cooling tower.

The head-on collision of flows in the center of the tower plays a significant role in the overall process of heat and mass transfer .:

The presence of a reliable water seal during the operation of each nozzle of a jet-vortex type into its ejection channel of circular cross section provides high ejection coefficients and a decrease in working pressure to 0.2-0.25 MPa.

Dry air enters the cooling tower through ejectors, as localization of the active zone of the cooling tower by weirs, wind partitions and a continuous flooring of the lower technological site prevents its moistening with vapors and drop moisture.

In the design of the cooling tower of the zone of entry of dry atmospheric air and exhaust of the exhaust vapor-air mixture, they are maximally distant from each other, which prevents moisture recirculation.

Claims (7)

1. An ejection tower containing a casing in the form of a multifaceted prism mounted on supports based together with a water drain pan on a supporting frame, and an exhaust channel is mounted in the upper part of the casing, consisting of a confuser and a diffuser having a manhole, below which there are trap a ladder and an upper technological platform surrounding the top of the casing outside, inside of which, at the same level, a drop catcher is installed, characterized in that the base of the casing has the shape of an inverted truncated pyramid, a side surface which is formed by inclined spillways with water-air ejectors installed on them and a water distribution system located directly below them, the openings of the ejectors being openings made in the planes of the spillways, along the contour of the inner edges of which are mounted wind walls that enclose the space from the spillway to the drainage pan, part the surface of which, outside the wind partitions, is completely covered by a deck forming the lower technological platform. 2. The ejection tower according to claim 1, characterized in that each ejector has a jet-vortex nozzle mounted in the center of the air inlet window, a water baffle ring is welded along the top of the spillway, and the ejection channel is installed coaxially with the nozzle so that between it and the plane spillway left a drainage gap with a height of 3-5 mm. 3. The ejection tower according to claim 2, characterized in that the ejection channel has a diameter of 50-60 mm larger than the diameter of the water baffle ring and is installed so that an annular gap is formed between them. 4. The ejection tower according to any one of claims 1 to 3, characterized in that the height of the ejection channel, depending on the diameter of the air inlet and the opening angle of the nozzle, is set to provide a guaranteed water seal between the torch and the wall of the ejection channel in an area 150 mm wide from the top edge of the channel. 5. The ejection tower according to claim 1, characterized in that the water distribution system includes risers and collectors in the form of closed polyhedrons that repeat the shape of the body, located concentrically relative to its axis. 6. The ejection tower according to claim 5, characterized in that the ejectors are arranged in rows symmetrically relative to the collectors, while the step of their installation is equal to the diameter of the ejector channel plus 50-100 mm, which eliminates the destruction of the dispersed liquid flares when they cross at a closer distance between them . 7. The method of organizing the heat and mass transfer process, which consists in the fact that when the nozzle feeds cooled water into the volume of the tower, the required amount of atmospheric air is sucked in the ejection channel, after which, in the active zone of the tower, during heat transfer from heated water to cooler air, partial evaporation of water, it is cooled, and the resulting vapor-air mixture goes through the exhaust channel of the cooling tower back into the atmosphere, characterized in that each nozzle is directed upward with a bias it supplies cooled water to the tower’s axis to its individual circular ejection channel, which ensures a guaranteed water trap, after which the movement of dispersed liquid flows from each ejector in the regime of intense turbulence inevitably leads to a comprehensive frontal collision in the upper part of the cooling tower, as a result of which multiple crushing and dropping of droplets in the regime of chaotic motion and the flows seem to freeze in the volume for some time, while part of the ejected air ha, saturated steam, leaves the cooling tower in an exhaust passage, and another part, entrained rain on the surface of the liquid in the catchment tray rotates and the air distributed over the volume, also goes into the exhaust passage, "sifting" between the free-falling rain drops.

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