Evaporative pre-cooler for air cooled heat exchangers

Abstract

The pre-cooler includes one or more cells which are oriented about an air stream to be cooled. A housing defines a perimeter of the cell with an inlet and outlet for air passing therethrough. Water outlet nozzles within the housing are preferably supported upon bars which orient the nozzles facing in a direction counter to flow of air through the housing. Each nozzle is coupled to a separate stage with multiple stages of nozzles coupled to separate valves. A controller opens or closes different valves. The controller measures ambient humidity and temperature conditions as well as air flow rates to calculate the amount of water to be added to the air and then opens appropriate numbers of stages of valves so that an appropriate number of nozzles spray water into the air to saturate the air. Flow rate control is thus provided without pressure variations, for optimal nozzle performance.

1 . An evaporative pre-cooler with variable water flow, comprising in combination:
 a support interposed within an air stream to be cooled;   a plurality of water outlets coupled to said support and oriented to discharge water into the air stream;   said plurality of water outlets each including a nebulizer, such that the water is discharged as a fine spray;   a source of water coupled to said plurality of water outlets and upstream of said plurality of water outlets;   each of said plurality of water outlets coupled to one of at least two valves downstream of said source of water, with each said water outlet that is coupled to a common valve discharging water from said source of water when said common valve is open; and   a controller adapted to operate said at least two valves to cause a water flow rate into the air stream to be varied.   
     
     
         2 . The evaporative pre-cooler of  claim 1  wherein said nebulizer includes an ultrasonic nebulizer. 
     
     
         3 . The evaporative pre-cooler of  claim 1  wherein said nebulizer includes a sufficiently small hole in each of said plurality of water outlets, in conjunction with a sufficiently high pressure of water upstream of said plurality of water outlets that water exiting said hole is atomized into a fine spray. 
     
     
         4 . The evaporative pre-cooler of  claim 3  wherein said valves and lines coupling said source of water to said water outlets through said valves are each sized to facilitate a greater flow rate of water than a sum of water outlet flow rates for water outlets associated with each said valve, such that pressure upstream of said water outlets is maintained. 
     
     
         5 . The evaporative pre-cooler of  claim 4  wherein a pump is interposed between said source of water and said at least two valves, said pump pressurizing water upstream of said valves to a pressure greater than a minimum pressure required to maintain nebulizer fine spray performance at said water outlets. 
     
     
         6 . The evaporative pre-cooler of  claim 1  wherein said water outlets coupled to said common valve of said at least two valves define a stage, with a number of said stages equal to a number of said valves downstream of said source of water, each of said stages having at least two water outlets therein, and wherein said water outlets of each said stage are spaced apart to decrease concentration of water within the air stream when said valve associated with said stage is open and each of said water outlets associated with said valve is discharging water. 
     
     
         7 . The evaporative pre-cooler of  claim 6  wherein a plurality of bars are oriented extending transverse to the air stream, said bars supporting a plurality of said water outlets thereon, said water outlets of each said bar coupled to at least two separate stages. 
     
     
         8 . The evaporative pre-cooler of  claim 1  wherein said support includes a partial enclosure surrounding the air stream on lateral sides of the air stream, and with an open front and rear, with the air stream entering said front of said enclosure and exiting said rear of said enclosure, said enclosure having a depth between said front and said rear at least as great as a majority of spray distance of said fine spray of water discharged from said plurality of water outlets. 
     
     
         9 . The evaporative pre-cooler of  claim 8  wherein said water outlets are located closer to said rear than to said front and with said water outlets facing at least partially toward said front of said enclosure. 
     
     
         10 . The evaporative pre-cooler of  claim 8  wherein a drift eliminator is located adjacent said rear of said enclosure, said drift eliminator having a plurality of open cells passing entirely therethrough and adapted to allow the air stream to pass through said cells in said drift eliminator, said cells having an at least somewhat curving path such that the air stream is required to curve while passing through said cells of said drift eliminator. 
     
     
         11 . The evaporative pre-cooler of  claim 10  wherein said water outlets are located adjacent said drift eliminator and facing away from said drift eliminator. 
     
     
         12 . The evaporative pre-cooler of  claim 11  wherein a drain is located below said drift eliminator, said drain adapted to collect water condensing on said drift eliminator and falling down off of said drift eliminator, said drain coupled to said plurality of water outlets through a pump upstream of said water outlets, such that water condensing on said drift eliminator is at least partially recycled back to said water outlets. 
     
     
         13 . The evaporative pre-cooler of  claim 1  wherein an anemometer is coupled to said support and oriented to measure a flow rate of the air stream to be cooled, said anemometer coupled to said controller to supply a signal related to speed of the air stream to be cooled. 
     
     
         14 . The evaporative pre-cooler of  claim 13  wherein a humidity sensor is coupled to said support and positioned to measure humidity of the air stream to be cooled, said humidity sensor adapted to send a signal to said controller indicative of humidity of the air stream to be cooled. 
     
     
         15 . The evaporative pre-cooler of  claim 1  wherein a sensor is located downstream of said water outlets, said sensor adapted to measure humidity of the air stream after the air stream has been cooled by evaporation of the fine spray of water discharged by said plurality of said water outlets, said sensor supplying a signal in the form of feedback to the controller to adjust a water flow rate from said plurality of water outlets responsive to humidity sensed by said humidity sensor downstream from said water outlets. 
     
     
         16 . The evaporative cooler of  claim 1  wherein said support is located adjacent an air inlet of an air receiving mechanical device with a fan therein, said fan generating the airflow, a signal associated with speed of said fan coupled to said controller to supply a signal related to speed of the air stream to be cooled. 
     
     
         17 . A water evaporation pre-cooler, comprising in combination:
 a plurality of water outlets oriented to discharge water into an air stream;   said plurality of water outlets each including a nebulizer, such that the water is discharged as a fine spray;   a primary source of water coupled to said plurality of water outlets upstream of said plurality of water outlets;   a drain below said plurality of water outlets, said drain adapted to collect condensed water from said water outlets;   said drain routed to a secondary source of water coupled to said plurality of water outlets upstream of said plurality of water outlets; and   at least one feed valve upstream of said plurality of water outlets, said at least one feed valve adapted to control which of said primary source of water and said secondary source of water supplies water to said plurality of water outlets.   
     
     
         18 . The water evaporation pre-cooler of  claim 17  wherein said primary source of water has a greater water capacity than said secondary source of water. 
     
     
         19 . The water evaporation pre-cooler of  claim 18  wherein said primary source of water has a water capacity greater than twice a capacity of water in said secondary source of water. 
     
     
         20 . The water evaporation pre-cooler of  claim 19  wherein said primary source of water has a water capacity at least ten times greater than a water capacity of said secondary source of water. 
     
     
         21 . The water evaporation pre-cooler of  claim 17  wherein said secondary source of water has a lesser amount of dissolved solids contained therein than said primary source of water. 
     
     
         22 . The water evaporation pre-cooler of  claim 17  wherein a drift eliminator is located downstream of said water outlets, said drift eliminator having a plurality of open cells passing entirely therethrough and adapted to allow the air stream to pass through said cells in said drift eliminator, said cells having an at least somewhat curving path such that the air stream is required to curve while passing through said cells of said drift eliminator. 
     
     
         23 . The water evaporation pre-cooler of  claim 22  wherein an enclosure surrounds at least portions of the air stream to be cooled, said enclosure including an entrance opposite an exit with said entrance adapted to receive said air stream therein and said exit adapted to discharge said air stream therefrom, said enclosure including a floor on one lateral side of the air stream extending between said entrance and said exit, said floor having said drain therein, said floor located beneath said drift eliminator, said drift eliminator located adjacent said exit of said enclosure. 
     
     
         24 . The water evaporation pre-cooler of  claim 23  wherein said water outlets are located adjacent said drift eliminator and oriented to spray said fine spray of water at least partially toward said entrance of said enclosure. 
     
     
         25 . The water evaporation pre-cooler of  claim 24  wherein each of said plurality of water outlets is coupled to one of at least two valves downstream of both said primary source of water and said secondary source of water, with each said water outlet that is coupled to a common valve discharging water when said common valve is open. 
     
     
         26 . The water evaporation pre-cooler of  claim 25  wherein said water outlets coupled to said common valve of said at least two valves define a stage, with a number of said stages equal to a number of said valves downstream of said source of water, each of said stages having at least two water outlets therein, and wherein said water outlets of each said stage are spaced apart to decrease concentration of water within the air stream when said valve associated with said stage is open and each of said water outlets associated with said valve is discharging water. 
     
     
         27 . The water evaporation pre-cooler of  claim 26  wherein a plurality of bars are oriented extending transverse to the air stream, said bars supporting a plurality of said water outlets thereon, said water outlets of each said bar coupled to at least two separate stages. 
     
     
         28 . A method for cooling an air stream, including the steps of:
 providing a plurality of water outlets oriented to discharge water into the air stream, the plurality of water outlets each including a nebulizer, such that the water is discharged as a fine spray, a source of water coupled to the plurality of water outlets and upstream of the plurality of water outlets, each of the plurality of water outlets coupled to one of at least two valves downstream of the source of water, with each water outlet that is coupled to a common valve discharging water from the source of water when the common valve is open, and a flow rate controller coupled to the water outlets and adapted to control a rate of flow out of the water outlets;   determining an amount of water flow needed to cool the air stream a desired amount by evaporation of the water into the air stream; and   adjusting the at least two valves to adjust a number of water outlets discharging water to more closely match the needed amount of water flow.   
     
     
         29 . The method of  claim 28  including the further step of defining water outlets coupled to a common valve as being associated with a common stage, with a number of stages equaling a number of valves, with each stage having a corresponding water flow rate when open; and
 selecting stages to be open as needed to total the desired amount of water flow. 
 
     
     
         30 . The method of  claim 29  including the further step of spacing water outlets within common stages so that when a stage is operating water outlets associated with the operating stage are spaced apart to distribute water evenly within the air stream. 
     
     
         31 . The method of  claim 30  including the further step of dividing the air stream into separate portions and providing separate cells associated with each portion of the air stream to be cooled, the separate cells each including a separate enclosure which surrounds at least portions of the air stream to be cooled, said enclosure including an entrance opposite an exit with the entrance adapted to receive the air stream therein and the exit adapted to discharge the air stream therefrom, the enclosure including a floor on one lateral side of the air stream extending between the entrance and the exit. 
     
     
         32 . The method of  claim 31  including the further step of collecting unevaporated water from the air stream by providing a drift eliminator adjacent each exit, the drift eliminator having a plurality of open cells passing entirely therethrough and adapted to allow the air stream to pass through the cells in the drift eliminator, the cells having an at least somewhat curving path such that the air stream is required to curve while passing through the cells of the drift eliminator. 
     
     
         33 . The method of  claim 31  wherein said dividing step includes the step of configuring each cell to have the floor thereof located beneath the drift eliminator and adjacent the exit of the enclosure. 
     
     
         34 . The method of  claim 33  including the further step of configuring each cell to have a separate controller and separate valves for independent operation of the separate cells on an associated portion of the air stream. 
     
     
         35 . The method of  claim 33  wherein the separate cells include a common controller and common valves with each stage having at least one water outlet associated with each cell. 
     
     
         36 . The method of  claim 28  including the further step of locating a drain below said plurality of water outlets, the drain adapted to collect condensed water from the water outlets, the drain routed to a secondary source of water coupled to the plurality of water outlets upstream of the plurality of water outlets, and locating at least one feed valve upstream of the plurality of water outlets, the at least one feed valve adapted to control which of the source of water and the secondary source of water supplies water to the plurality of water outlets. 
     
     
         37 . The method of  claim 36  wherein the secondary source of water has a capacity less than a capacity of the source of water. 
     
     
         38 . The method of  claim 37  including the further step of cycling the feed valve to cause the water outlets to periodically receive water from the secondary source of water, the secondary source of water having a lesser amount of dissolved solids therein, such that said cycling step purges dissolved solids from water lines upstream of the plurality of water outlets.