An improved evaporative cooling unit. The unit efficiently cools air when the evaporative cooling pad is dry and utilizes the turbulent intermixing of air and water to evaporatively cool air without requiring excess water flow onto and from the cooling pad.

This invention relates to evaporative cooling systems. 
More particularly, the invention relates to an evaporative cooling unit 
which is utilized to precool air flowing over a refrigeration unit 
condenser coil and which extends the operational life of the porous, 
wetted heat transfer pad utilized in the evaporative cooler. 
In another respect, the invention relates to an evaporative precooling unit 
in which excess water does not flow from the bottom of the heat transfer 
pad and which therefore does not require a sump for storage of excess 
water or require a hose to drain excess water from the precooler unit. 
In a further respect, the invention relates to an evaporative precooling 
unit which, in the vicinity of the precooling unit, reduces the incidence 
of arthropods such as arachnids and oval, flat bodied Blattidae insects, 
and reduces the incidence of smut, rot and other fungi which produce 
disagreeable odors and provide a breeding ground for disease. 
In still another respect, the invention pertains to an evaporative 
precooling unit which efficiently cools air when the evaporative cooler 
pad is dry, which utilizes the turbulent intermixing of air and water to 
evaporatively cool air without requiring excess water flow onto and from 
the cooler pad, and which minimize the accumulation of water on the 
condenser coil of a refrigerator unit. 
In yet a further respect, the invention relates to an evaporative 
precooling unit in which the pad is moistened and cooled by a stream of 
air flowing through the pad. 
Evaporative precoolers have long been utilized to reduce the temperature of 
air being drawn over the condenser coil of a refrigeration unit. In 
operation, water flows onto a pad in the precooling unit. Heat in air 
flowing through the pad is consumed in evaporating water in the pad, 
reducing the temperature of the air. 
While evaporative precooling systems require the construction and use of 
relatively simple equipment and consume only minimal amounts of 
electricity, there are disadvantages inherent in such systems. Water 
soaked pads create substantial resistance to the flow of air through the 
pads and can saturate the air with water droplets which are carried from 
the evaporative cooling pad to the refrigeration unit cooling coil. When 
water on the coil evaporates, mineral deposits form on the coil. Further, 
evaporative cooling units have acquired the apt name of "swamp coolers" 
because they promote the formation of mildew and other fungi which produce 
disagreeable odors. Since evaporative cooling units are utilized in warm 
ambient temperatures and provide a ready source of water, components of 
the cooling units are susceptible to corrosion and decay. In particular, 
when conventional cooler pads fabricated from paper are utilized, the 
steady flow of water through the pads leaches protective chemicals from 
and causes the disintegration of the pads, making the pads potential hosts 
for growths of slimes. Sump trays which collect excess water from the pad 
or hoses carrying water away from the pad support growths of algae and 
fungi plant diseases like rot and smut. Infestations of cockroaches, 
rodents and other vermin which emerge during the night are attracted to 
the vicinity of the cooler units and leave their excrement larvae. 
Accordingly, it would be highly desirable to provide an improved 
evaporative precooling unit which would not produce excess water and which 
would minimize the leaching and disintegration of paper pads which occurs 
when water is sprayed onto the pads or is directed onto the top of and 
flows downwardly through the pads. 
Therefore, it is a principal object of the invention to provide an improved 
evaporative cooling unit. 
A further object of the invention is to provide an improved evaporative 
cooling unit which reduces the likelihood that infestations of arachnids, 
cockroaches, rodents and other nighttime vermin will occur in the vicinity 
of the cooling unit, and which reduces the likelihood that water bearing 
components of the cooling unit will serve as hosts for algae, rot, smut 
and other growths which produce disagreeable odors and provide a breeding 
ground for disease. 
Another object of the instant invention is to provide an improved 
evaporative precooling unit which efficiently cools air when the normally 
wetted porous precooler pad is dry, which utilizes the turbulent 
intermixing of air to evaporatively cool air, and which minimizes the 
accumulation of water on the coil of a refrigeration unit. 
Still a further object of the invention is to provide an improved 
evaporative cooling unit which does not produce excess water and which 
therefore does not require a sump or hose for handling of excess water. 
Yet another object of the invention is to provide an improved evaporative 
cooling unit which extends the operational life of the porous, wetted heat 
transfer pad utilized in the cooling unit.

Briefly, in accordance with my invention, I provide a heat exchange unit 
for precooling an air stream traveling toward and over the condensing coil 
of a refrigeration unit. The heat exchange unit includes a frame; a porous 
heat transfer pad mounted in the frame; nozzle means carried on the frame 
for directing a spray mist forwardly of the heat transfer pad, the spray 
mist emitted from the nozzle means initially traveling in a direction such 
that the mist will not contact the heat transfer pad; means mounted on the 
frame for causing turbulent intermixing of the airstream with the spray 
mist prior to the airstream passing into the heat transfer pad; and, means 
for controlling the quantity of water emitted by the nozzle means such 
that substantially all of the spray mist is intermixed with the air stream 
prior to the airstream passing through the heat transfer pad. 
In another embodiment of my invention, I provide a method of precooling an 
air stream traveling toward and over the condenser coil of a refrigeration 
unit. The method includes the steps of positioning an evaporative heat 
exchange unit forwardly of the refrigeration unit condensor coil such that 
the air stream travels through the heat exchange unit prior to traveling 
over the condensor coil, and operating the heat transfer unit to precool 
the air stream. The heat exchange unit includes a frame; a porous dry heat 
transfer pad mounted in the frame and having a lower edge; nozzle means 
carried on the frame for directing a spray mist forwardly of the heat 
transfer pad, the spray mist emitted from the nozzle means initially 
moving in a direction of travel such that the spray mist will not contact 
the heat transfer pad; means mounted on the frame for causing the 
turbulent intermixing of the airstream with the spray mist prior to the 
airstream passing through the porous heat transfer pad; and, means for 
controlling the quantity of water emitted by the nozzle means such that 
substantially all of the spray mist is intermixed with and evaporated in 
the air stream prior to the airstream passing through the heat transfer 
pad. Excess water does not flow from the lower edge of the pad during 
operation of the heat exchange unit. 
Turning now to the drawings, which depict the presently preferred 
embodiments of the invention for the purpose of illustrating the practice 
thereof and not by way of limitation of the scope of the invention, and in 
which like reference characters represent corresponding elements 
throughout the several views, FIGS. 1-5 illustrate an evaporative cooling 
unit constructed in accordance with the principles of the invention and 
including a frame having side walls 12 and 13, front wall 14, rear wall 
15, floor 16, top 17 removably secured to front wall 14 by screws 18, 
screen grating 19 attached around its peripheral portions to wall 14, 
porous paper heat transfer pad 20 secured to grating 21, and grating 22 
attached to rear wall 15. L-shaped strips 23 are secured to side walls 12 
and 13 by rivets 24 and, along with rear wall 15 and the portions of wall 
12 spanning the distance between wall 15 and strips 23, forms an elongate 
generally vertically oriented U-shaped groove into which pad 20 and 
grating are slidably inserted. Fitting 26 secured to wall 12 fixedly 
maintains nozzle means 27 and control means 28 in position adjacent walls 
12. Control means 28 is powered by electricity delivered by wires 29. 
Water is delivered to control means 28 and nozzle means 27 through conduit 
30. Control means 28 includes a sensor (not shown) which monitors the 
temperature and humidity of the ambient air and adjusts the flow of water 
through nozzle means 27 such that the large majority of water emitted from 
nozzle means 27 as spray mist stream 31 is evaporated or carried in stream 
of air 32 flowing into and through the evaporative cooling unit 11. Air 
stream 33 leaving unit 11 generally, depending on the temperature and 
humidity of the ambient air in stream 32, has a temperature cooler than 
that of air in stream 32. Gratings 19, 21 and 22 interrupt the generally 
laminar flow of air in stream 32 and cause the formation of eddy currents 
33 and turbulence in stream 32 as it passes into unit 11. This turbulence 
facilitates the intermixing of mist stream 31 in stream 32 to evaporate a 
substantial portion of mist stream 31 in stream 32 prior to stream 32 
passing into cooler pad 20. The flow rate of spray mist stream 31 from 
nozzle 27 is regulated by control unit 28 such that the very large 
majority of mist stream 31 is carried and evaporated in stream 32 and such 
that there is not an excess of mist stream 31 which falls toward the floor 
16 and forms a puddle of water thereon. The flow rate of mist stream 31 
from nozzle means 27 refers both to the volume of water emitted by nozzle 
means 27 and to the velocity of the mist when it initially leaves nozzle 
means 27. If the volume of water emitted by nozzle 27 is too great, then 
stream 32 will not evaporate or carry away all of mist stream 31 and a 
puddle of water will form on floor 16. If the velocity of water, i.e., the 
pressure, of water emitted from nozzle means 27 is too great in relation 
to the size of the mist particles, then portions of mist stream 31 may 
travel through stream 32, impinge on wall 13, combine with other mist 
particles, and flow down wall 13 to floor 16. 
Spray mist is emitted from nozzle means 27 in a direction of travel which 
will not carry the mist into contact with grating 21. While in FIG. 2 
portions of mist 31 can be directed toward grating 21 and still be 
contacted and evaporated by stream 32 before contacting grating 21, it is 
preferred that mist stream 31 have an initial direction of travel which is 
parallel to or moving away from screen 20. If spray mist stream 31 
impinges pad 20, efficient evaporation of water in air stream 32 is more 
difficult to achieve and the water from stream 31 tends to accumulate in 
and flow downwardly through pad 20. When excess water flows downwardly 
through pad 20, protective anti-fungi chemicals are leached from pad 20 
and a pool of excess water forms in the bottom of unit 11. The size of 
water droplets in spray mist stream 31 can vary; however, a very fine 
particle size is desired in order to facilitate evaporation of the water 
in stream 32 prior to the time stream 32 flows into and through pad 20. A 
microprocessor embodiment of the invention like that described above is 
depicted in FIG. 6 and includes temperature sensor 50, humidity sensor 51, 
microprocessor 52, valve 54, and data 53 contained in the microprocessor 
memory. 
Pad 20 functions to remove unevaporated water droplets from stream 32 and 
to filter out dust, etc. from stream 32. During operation of unit 11, pad 
20 normally becomes damp but does not produce excess water which drips or 
flows from the pad. This is, as earlier described, accomplished by control 
means 28 which adjusts the flow rate of water through nozzle means 27 such 
that the majority of the volume of spray mist 31 emitted from nozzle means 
27 is evaporated in stream 32 before stream 32 flows into pad 20. Control 
means 28 includes a valve and a microprocessor. Sensors (not visible) 
continually monitor and provide the microprocessor with the ambient air 
temperature and humidity, the volume and velocity of air streams 32 and 
33, and the temperature and pressure of water flowing through conduit 30. 
The microprocessor is also provided with data such as the size of water 
particles emitted through nozzle means 27; data showing the relationship 
between the wet bulb temperature, the dry bulb temperature and the 
humidity of the ambient air; data showing the interrelationship between 
the temperature, vapor pressure and humidity of air; the amount or degree 
of turbulent air flow caused by screens 19, 21 and 22; and, formulae the 
other data which readily permit the microprocessor to determine the proper 
flow rate of spray mist stream 31 from nozzle means 27 into air stream 32 
in order to allow generally all of mist 31 to be evaporated or carried in 
stream 32 to avoid the formation of puddles of excess water inside unit 
11. The programming and data necessary for the microprocessor to make 
these calculations are well known to those of ordinary skill in the art. 
The presently preferred grating 19 is illustrated in FIGS. 3 and 4 and is 
identical to gratings 21 and 22. The shape and dimension of grating 21 
facilitates the formation of eddy currents in stream 32 passing through 
grating 19 and therefore promotes the efficient intermixing of mist stream 
31 and stream 32 and the evaporation of mist stream 31 in stream 32. As 
shown in FIG. 3, grating 19 is comprised of a plurality of interconnected 
rectangular panel-shaped legs 34, 35, 36 which define a plurality of 
adjacent hexagonal shaped apertures through which air stream 32 flows. 
Cylindrically shaped legs can be utilized in place of rectangular legs 
34-36, but do not as effectively produce eddy currents in air stream 32. 
Each elongate leg 34, 35, 36 has a planar upper surface 37 spaced apart 
from, opposed to, and generally parallel to a planar lower surface 38A of 
generally identical dimension. If each leg 34, 35, and 36 were oriented 
such that upper and lower surfaces 37, 38A were parallel to the direction 
of travel of stream 32, then the flow of air around legs 34, 35 and 36 
would have a greater tendency to be laminar and not to generate eddy 
currents and turbulent areas in air stream 32. As shown in FIGS. 4 and 5, 
surfaces 37, 38 are not parallel to the direction of travel of airstream 
38 because each leg 34, 35, and 36 is slightly canted or rotated about a 
longitudinal axis 39 extending along the rear edge of the leg. In FIGS. 4 
and 5, the ghost outline of member 34 represented by dashed lines 38 
represents the orientation leg 34 would have if its upper and lower planar 
surfaces 37 and 38A were parallel to the direction of travel of stream 32. 
Instead, the actual orientation of leg 34 with respect to stream 32 is 
obtained by rotating the ghost outline 40 slightly about axis 39 in the 
direction of arrow A. When each leg 34 is canted into stream 32, turbulent 
air flow is caused in the manner indicated by arrows 40-44 in FIG. 4. 
Similar turbulent airflow is caused by screen 21 positioned intermediate 
mist stream 31 and pad 20. The turbulent airflow around screen 21 further 
facilitates the evaporation of water in stream 32 prior to the exiting 33 
of the air stream from unit 11. Screen 22 serves the same water-air 
intermixing function just described for screen 19 and 21. 
The particular advantages of the apparatus of the invention are that when a 
dry pad 20 is slidably inserted in unit 11 and operation of the unit is 
initiated, air 32 flowing into the unit is immediately cooled. It is not 
necessary for pad 20 to become wetted before cooling occurs. Maintenance 
of the unit is greatly reduced because little, if any, excess water is 
produced by the unit. Operating unit 11 without continuously directing a 
downward flow of water through pad 20 increases the operational life of 
pad 20. Unit 11 is especially useful as a precooler because cooled air 33 
exiting the unit has few, if any, water droplets which can collect on the 
condenser coil of a refrigeration unit. 
Eddy current screens 21 and 22 can be in a position which is immediately 
adjacent or spaced apart from pad 20. If unit 11 is operated without 
screen 19 in place, the passage of air stream 32 through mist 31 still 
creates air turbulence which facilitates the intermixing of water and air; 
however, when eddy currents exist in stream 32 when stream 32 contacts 
stream 31, intermixing of air and water appears to be greatly facilitated. 
When unit 11 is operating at peak efficiency, stream 33 will not contain 
excess water droplets which can collect on the condenser coil of a 
refrigeration unit.