【 Weak current College 】 cooling towers feature and type description

First, the cooling towers of function and basic principles of the so-called cooling towers by definition that is applied to the cooling tower for the purpose of sprinkler systems; to the top of the General common in small and medium-sized air conditioning with cooling towers, the structure is nothing more than a round or square crust, and the shell from top to bottom, respectively, a ventilation motors and drives the fan of pumping, retaining plate, Isaac (powder) water, the thermal material (fill material), in a outlet, the lowest for the Flume, inlet and outlet and pump motor, its function is absorbed by the air conditioning or heat energy generated by cooling water transfer in cooling towers in the water and air in direct contact with the heat emissions to the atmosphere.　　Because water has a high latent heat (evaporative heat) energy, plus obtain easily, while the air has a moisture capacity in such favourable conditions, cooling towers into the heat of the most effective and least expensive tools.　　Cooling water tower in retaining plate is mainly used for small water droplets of loss stop, when the hot water through the sprinkler nozzles are sprayed in cooling towers to the top of the filler, with gravity downward flow, because the reverse flow of air will result in smaller droplets with air flow to take, in order to reduce the loss of cooling water, water sprinkler nozzles above sets the retaining plate device, small droplets encounter retaining device affected by the barrier and attached files, such as water on stalls on water Edition accumulated up to larger droplets, when its gravity is higher than the air flow driven by impedance drops of reverse power, will fall down to packing. Second, the cooling towers form classification introduction on the market of cooling towers form types, depending on the type of air-driven can be divided into mechanical force-driven (Mechanical draft) and natural convection (Nature Draft); according to air and water flow path of the relative direction, cooling towers, basically can be divided into the reverse-flow (commonly known as counter-flow or reverse flow) and cross-flow (commonly known as a cross-or Exchange); according to cooling water circuit and can be divided into tight loop road-cooling towers or known as hermetic cooling towers, another is the open loop-type cooling tower or called open cooling towers, which closed loop road-type cooling tower, also known as evaporative-cooling towers.　　The different types of cooling towers of features will be described below. 3. air-sidecar (Mechanical Draft) cooling towers is characterized by a mechanical power (generally the motor fan) driven air movement, and water tower in cooling water or heat exchanger for heat and mass transfer in order to reduce the cooling water temperature. Depending on the location can be classified as exhaust fan and blowing-in the so-called two, is blowing-in of air blown into the fan shell inside and Shell internal cooling water to heat and mass transfer Exchange job, usually made of blown under the shell, the absorption of water vapor in the air above a blow out, blown-cooling towers is through the fan will blow out gas into the Tower, the Tower air as positive pressure (greater than 1 atmosphere), density than higher than atmospheric pressure of air density, air heat exchange coefficient is slightly higher, this is blown-cooling towers.　　Usually blow in cooling towers Tower of the surrounding gas density (closed degrees) demanding that the reason was to avoid the tower top air cannot entirely by air blowing out, has not fully and cooling water full exposure to heat and mass transfer; second blowing-in effect by fan blades at the air inlet port local kinetic energy, local wind speed will be a higher end (air outlet side) of the air flow dispersion, export out of the wind speed is more stable, dynamic local outlet not to exhaust type are relatively high, and therefore out of the wind flow scenarios more, this is blown into the shortcomings of cooling towers. Ventilation-cooling tower is usually at the top of the tower is equipped with a motor drive of an axial flow fans, exhaust-hence its Tower in the air as negative pressure (less than a standard atmospheric pressure), the Tower air density is low, as a result of heat and mass transfer coefficient should also be relatively low, this is the disadvantage of exhaust type. However, due to its exports of locally driven fan blade, export a high velocity air local, blowing out of local wind speed is larger, so the drain of humid air is blown off, its back to the traffic is much lower than that of blown-cooling towers, which are the advantages of exhaust type.　　However due to the air density is low (because the outlet air temperature is high and the moisture content is the larger) of ventilation-demand more of the kinetic energy of wind-driven. From the top of the water droplets are often overflow the mechanically driven air-cooling towers are very difficult to completely avoid, because of the cooling towers of cooling water cooling mode to use air and water by direct contact, by the evaporation of water vapor the air away, so the air and water contact area in particular, and thus water droplets scatter when wind speeds are sufficient to drive the water drops, drops of water may vary according to the wind and the water tower up elegant, causing loss of phenomena, splash, usually near the outlet (fan below) equipped with retaining plate to stop water splash damage.　　Ventilation-cooling tower water spatter loss often than blown-cooling towers to many because the ventilation-cooling towers of export local wind speed is large, this point is completely air-cooling towers of shortcomings.　　4. natural convection driven air-type (Nature Draft) cooling towers of natural convection driven air-cooling towers feature is the air flow is according to the temperature difference or density difference the formation of buoyancy driven air flow in cooling towers, not driven by mechanical power, the principle of the air flow is driven by density difference air natural convection to achieve the effect of air circulation; in cooling towers internal air temperature with humidity and are relatively high, the outside temperature is higher, the lower the relative density, moisture content, the more relative density is lower, because the Tower air density and a tower, air density is low, the tower containing humid air floatation results prompted the Tower exterior dry air from the Tower bottom into the Tower, reaching the same mechanical-driven cooling towers of air circulation. In addition to the above category, the cooling towers can be mechanically driven air and natural convection driven air mixture of the two classes, a more advanced natural convection cooling towers, at the bottom with fan-assisted driving air flow (Fan assist cooling tower), this way you can save the height of the Tower, the initial costs are less, but the operation power consumption increased costs arising from its disadvantages. Another natural convection cooling towers internal device of heat after combustion flue pipe outlet, which went to sulfide device may also installed in the Tower, the use of exhaust heat from the flue gas temperature increase, increased convective activityShould be, so you can lower the Tower high savings in initial funding.　　(5) the counter-flow with AC-cooling towers form according to the relative air and water flow path direction, cooling towers, basically can be divided into reverse-flow patterns and cross-flow, air and water to the Tower within the exchange of heat and mass transfer, when the air and water flow in the opposite direction, this is called a counterflow cooling towers and air and water in the vertical direction of mobile users, this is referred to as AC-cooling towers. Common of upstream cooling towers more than round tower-like structure, a circular tower-like structure of cooling towers for own design (but sometimes also for dual model design), mainly due to the round tower-like structure has the ring of the Tuyere, big air volume, efficiency will also be high, the round will be considered more fan combination, can achieve sufficient space utilization. Square cooling towers more module features can usually be done for multiple unit combination products, combined with the housing space utilization, the square for more unit combinations arranged in a straight line, the space utilization of great advantages, within these areas are relatively small. General square of the air intake located below on both sides, counterflow square cooling towers are in a outlet restrictions are small tonnage type, larger tonnage-based communication.　　Counterflow cooling towers of the air primarily by thermal packing under the direction of flow, tricking the above affected by gravity downward flow formation and air counterflow, reverse flow with high heat conductivity, because when water closer, closer to the air inlet, where the air moisture content is low, the wet-bulb temperature relative also lower, even relatively close to the export of low-temperature thermal water has continued, and by air to air close to the exit, the air because of the moisture of the air inlet temperature is improving a lot, but here is the entrance to the water (near Sahara water service), the water temperature is also relatively high, the water heat transfer to air still sustainable, water temperature and the air is always available at the temperature difference, so the high heat efficiency. AC-type cooling tower design is available in the main square, circular design, shape differences mainly consider the venue space arrangements to square easier placement, square AC-cooling towers air flows from the Tower of the lateral, and gravity downward vertical water into the Sahara, because large area on both sides of the water tower, air intake relative cross-sectional area is larger, so this type of design for large tonnage type; AC-cooling towers of packing is typically installed into and level into a winning oblique angle, because the air intake flow direction causes the water to flow through; AC-cooling towers on either side of the heat exchange area is located below the fan is designed to be hollow, air from both sides of the center of the space, then the top fan off, so the exchange type is classified as exhaust-cooling towers. Square AC-cooling towers maximum advantage is space layout easier, have a better ability of module, available from the other side of the multiple sets of parallel still does not affect the air inlet duct of the side; AC-another advantage is less spatter loss, when the air flow from the ends shall be determined by the central space almost level into the up with inertial force of water droplets difficult steering and with fans. But AC-cooling towers, water is unevenly distributed, as well as units of heat transfer surface area is relatively low heat effect is its shortcomings, is located at the water tower near the outlet water temperature on both sides, and the water flows towards the lowest bottom allows lateral water always at low temperature and low temperature of inlet air, and is located in the inside of the cooling water tower more contact with the air and water are the air of the downstream side, air closer downstream end its moisture content is higher, the higher the wet bulb temperature, at which point the water vapour absorption cooling volume is limited, so the inside temperature is also relatively high up on the outside.　　Obviously the thermal heat transfer packed inside a lateral heat carrier temperature slightly worse, uneven distribution of cooling capacity when overall will be slightly lower.　　6 Jet-type cooling tower design Jet-type cooling tower is a so-called long term not be maintenance of cooling towers, the reason is that this type of cooling towers are not required (no) turn component, do not need (no), and does not have soaks wadding circuit in it; because the use of the conditional distribution of a wide, in operation and maintenance scenarios vary, depending on air quality and purity of water. The Jet-type of general maintenance of cooling towers are described below, due to the cooling towers mainly with refrigeration air-conditioning host or industrial process of cooling, generally regarded as host of the system, and more with the host configuration location is not in the same place, while the host is considered to be periodic maintenance of focus, but the cooling towers of related inspection and maintenance work are often been missed. For Jet-type cooling tower of the main system maintenance and cleanliness of the air and water are closely connected, in the air, the factory emissions and some insoluble solids are causing corrosion of the main culprit; water especially water evaporation of impurity will accumulate in the water circulation system, a high concentration to a degree, related scaling and corrosion will produce.　　As the air and water cleanliness is determined fixed displacement and maintenance cycles.　　For Jet-type cooling tower (fanless cooling towers) maintenance of very small, so this kind of cooling towers and as no fault in General-cooling towers, it's maintenance of a relatively small and simple, including nozzle maintenance, make-up water valve maintenance, cleanup of flume, drainage systems review and adjustment, leakage checks, as well as metal surface protection coating inspection and so on.　　The Jet-type cooling towers of spray rate is high, the smaller the nozzle, where the congestion shall particularly careful processing, so the water filter to be more sophisticated, generally fitted with double filter, in addition to sink in a coarse filters, Jet dispersion, together with the former has a smaller particle filters, in order to avoid nozzle blocked shall always remain clean filter screen, so the filter net of the design should be easy to take the easy install. Because of the water must be always examine the air inlet steady flow distributor should be designed to be easily removed from so that we can carry out with the Jet observation. Jet air distribution tubes on the heels of imports after steady flow Distributor, remove the air inlet steady flow distributor to observing jets is normal.　　When the nozzle orifice has blocked are available as non-type brush brushing. 7. open (Open Type) and closed (Closed Type) cooling towers by cooling water circulation loops can be divided into open water sensitive cycle loop type (Open Type) hereinafter referred to as open and closed water circulation loop type (Closed Type) "Closed-type cooling tower, open cooling tower is often used for refrigeration and air conditioning systems or industrial process of cooling, for example in the refrigeration and air conditioning system in its circulation of cooling water main purpose is to serve as the host of ice water condensing refrigerant, when cooling water uptake in the condenser condensation of refrigerant emissions of heat, cooling water temperature will be promoted, in order to make this cooling water recycling, in cooling towers with the Tower of space within the internal air and water quality of convective heat and directly pass, this space is usually equipped with filling materials to increase the cooling water and air of heat and mass transfer area, and a fan will air only from the bottom up, rising air and self watering unit Sala of cooling water in direct contact with the part of the cooling water because of evaporation gasification and was off the air absorption and evaporation gasification of cooling water can be taken away large amounts of energy, to achieve the effect of the cooling water temperature, the temperature of the cooling water to the circulation pump to the condensation of refrigerant condenser absorption release of thermal energy. As the tradition of cooling towers for the open architecture, circulation of cooling water directly in contact with air, the air of pollutants is easy through the contact with the cooling water is water absorption.　　Long-term contact with air, because of the evaporative cooling water constantly need new water added, it is extremely easy to make the cooling water concentration increases, the other with dust and other factors will result in delivery of cooling water foul and ion concentrations increase, easily scaling is now like in the formation of lines and the condenser, the accumulation of scale build-up resulting flow reduction, resulting in increased horsepower and transportation within thermal impedance of the condenser increases, heat exchange efficiency and thus reduce the efficiency of the system allows the decline, the formation of wasted energy and heat exchanger reduces the service life.　　In order to improve the open cooling tower causing heat exchanger inevitable of corrosion and fouling problems, hermetic cooling towers to be the best choice, airtight cooling towers, mainly by a closed loop one side cooling water circulation pipes (the original opening of the cooling water) and then with an opening of the secondary side cooling water circuit, such arrangements can make a side cooling water completely in a closed loop recycling and to avoid the problems of scale factors, at the opening of the secondary side and both phase changes of thermal establishments, there is a high-efficiency liquid to liquid tube type heat exchanger or plate-fin heat exchangers for the purpose of achieving heat; this arrangement of cooling towers of component as its key, high-efficiency water spray and spray head, on liquid pipe type or plate-fin heat exchangers and stall shower bath, etc.　　Closed-type cooling towers to pipe type airtight cooling towers structure more and more for refrigeration and air conditioning systems or industrial process cooling and water cooling job agencies, cool water to avoid structure occurred in refrigeration and air conditioning systems or industrial process of in-house, to maintain the long-term nature of high thermal transfer agency efficiency thus prolonging life and conservation agencies and save maintenance costs, and so on, apart from the tube type, using the plate heat exchanger in airtight cooling towers structure is also an effective way to present to employers are already active in its efficient plate heat exchanger for cooling towers, and has a number of years. 8. reduce the emission of visible moisture-cooling towers (saving) design General cooling towers (classic) discharge of water and gas mixture are approximated or beyond saturation, full evaporation of water vapor is a colorless, however if the exhaust with incomplete evaporation of water mist is a white smoke (mist) formation, when temperatures are low, white steam caused Visual obstacles are serious, some areas are causing visual impairments, especially winter season due to low temperatures, when water vapor emissions into the atmosphere when it is formed by heat and water fog. If you want to avoid water mist cause visual impairments are like, emission gas as possible below the saturation, one can reduce water vapor discharge of cooling water tower design, as shown in Figure 12, the design principles is the cooling towers are divided into two sections for dry, wet, dry section is located in the upper area of the hot water inlet, wet period is located in the River district, hot water first to do sections upstream areas and air for heat, this area of the water and the air completely area into two road, non-contact, no water evaporation and therefore the air dry, General design this section uses the pipe fin type heat exchanger or only bare tube type heat exchanger, hot water through the dry period followed into the wet period area, wet section area of water and air direct contact for heat and mass transfer, this segment of the air because of the evaporative water export approach saturation; dry air and exhaust of wet air from the fan, and for mixed before discharge into the atmosphere, far from saturated, exhaust gas to form after a difficult therefore does not return a water mist discharge is like a Visual disorder problems.　　However due to the increase in the dry section district, this design increases the cost, of course, it also reduces water evaporation. IX. conclusions of the cooling towers of many kinds, currently on the market mainly still to traditional open to main products, however, the structure has been the most difficult to effectively overcome the problem with the notion of closed-type cooling tower constantly popular, future cost to overcome the high efficiency of closed-type cooling tower will have the opportunity to replace the traditional open cooling towers, then the noise problem to be resolved, no fan cooling towers will be able to effectively address the noise problem, but is still subject to further improvement of the product.