Apparatus and method for dehumidification systems

A method and apparatus for controlling the atmosphere in a controlled environment including passing air into a cooling means to remove humidity and back into the environment and exchanging heat from the air entering the cooling means to the air exiting the cooling means, to increase dehumidification by a cooling recovery process.

BACKGROUND OF THE INVENTION 
This invention relates generally to an apparatus and method for maintaining 
a controlled environment. More particularly, the invention relates to an 
energy efficient dehumidifier which may be used alone or in connection 
with passive cooling systems to maintain a comfortable environment more 
efficiently. 
In America the use of air conditioning is common place and considered by 
most to be a necessity. A significant portion of the energy use in America 
is consumed by air conditioning. 
This was of little concern to America during the period of cheap energy 
costs. However, this ended with the era of the oil embargo and it is 
believed to be generally accepted that the days of cheap energy are gone 
forever. 
The large amounts of energy used by America have placed a financial strain 
on the economy particularly with regard to the balance of payments and is 
viewed by many as even a greater threat to America. The large dependence 
upon imported oil still remains even though the source of supply of 
imported oil is volatile and cannot be guaranteed. The high cost of oil 
from OPEC has resulted in some conservation. Thermostats have been lowered 
in winter and raised in the summer to attempt to produce energy 
consumption. A great deal of work is also being performed in the area of 
passive cooling to provide comfortable controlled environments with low 
energy costs. 
Passive cooling, however, cannot reliably remove humidity from the air 
because the cooling does not ordinarily reach the dew point temperature. 
Accordingly, although passive cooling can provide temperatures in the 
comfortable range, these temperatures may not be satisfactory in 
conditions of high humidity. Dehumidification is therefore required. 
Commercially available room air dehumidifiers are relatively inefficient 
and conventional air conditioners waste considerable energy if only 
dehumidification is desired by providing cooling not only redundant with 
but actually detrimental to the passive cooling system. The air 
conditioning can make the environment uncomfortable by unnecessarily 
reducing the temperature in order to remove humidity which significantly 
affects the comfort in the environment. 
The problem of providing dehumidified air to a controlled environment is 
well known. Known methods of doing this are shown in U.S. Pat. Nos. 
2,715,320, 3,293,874, 3,460,353, 3,921,413 and 4,189,929. Since a source 
of heat is readily available in conventional air conditioning units, one 
need only provide a heating coil in connection with the cooling coil so 
that the air which has been produced to the dew point temperature to 
provide dehumidification is heated to a desired temperature before 
entering the room. While this type of system is workable it does not 
increase the efficiency of the apparatus. Rather, it provides the desired 
results at a similar cost to conventional air conditioning. 
It is also well known in the art that heat exchangers can be utilized in 
connection with ventilating and heating systems. Examples of such heat 
exchangers are shown in U.S. Pat. Nos. 1,825,498, 2,092,835, 2,945,680, 
4,194,538, 4,222,436. These devices usually include a means for bringing 
in fresh outside air and transferring heat from the exhausted inside air 
to the incoming outside air to reduce the heat loss. 
With the large increases in the cost of energy, a need has arisen for a 
highly efficient apparatus and method for providing a comfortable 
controlled environment. Much of this effort has apparently been directed 
to increase the efficiency of conventional air conditioning systems. While 
this has reduced energy consumption, it has not provided an answer to the 
problem. It is believed that the present invention prides a solution to 
the long felt need for an efficient apparatus and method for controlling 
environments. The apparatus and method of the invention feels this long 
felt need for providing an efficient and workable solution to controlling 
environments. Other objects of the invention will become apparent from the 
following detailed description in the specification.

SUMMARY OF THE INVENTION 
A method and apparatus for variable cooling and dehumidifying or just 
dehumidify air for a controlled environment including a cooling means for 
reducing the dew point of air flowing across the cooling means to provide 
dehumidification through condensation. A heat transferring means is also 
provided to remove heat from the air entering the heat transferring means 
and to transfer this heat to the air exiting the cooling means to increase 
the efficiency of dehumidification by recovering the cooling potential of 
cold air exiting the cooling means. 
BRIEF DESCRIPTION OF THE THEORY AND EXPERIMENTAL ANALYSIS 
The essential components of the system are a cooling means and a heat 
transferring means. The cooling means must be able to reduce the dew point 
of the air coming from the conditioned environment. This cooling could be 
accomplished by an electrically driven vapor compression cycle device such 
as a conventional air conditioner or an electric refrigerator. It could 
also be accomplished by an absorption chiller powered by natural gas, 
solar, coal, etc., or it could be effected by chilled water, or some other 
chilled fluid or solid with cooling obtained from any source. 
The heat transferring means could be an air-to-air heat exchanger with a 
wide variety of internal configurations and materials, an air-to-air heat 
exchanger utilizing an intermediate heat transfer fluid such as a heat 
pipe or air-to-water-to-air heat exchange system, etc. Air motion through 
the heat exchanger and cooling means could be effected by one or more 
fans, blowers or other devices able to create an air flow. 
Both a conventional air conditioner and this invention can, under a range 
of ambient temperature and humidity conditions, produce dehumidification. 
By way of example, and not by limitation to explain the theory, the 
dehumidification process in a conventional air conditioner will be 
compared to the dehumidification process by the apparatus and method of 
this invention. For this example the invention apparatus is composed of a 
conventional air conditioner acting as the cooling means and a counter 
flow air-to-air heat exchanger as shown in FIG. 1. 
The apparatus and method of the invention differs from the standard air 
conditioner in that incoming air is significantly cooled in the heat 
transferring means before the air reaches the cooling means which in this 
case would be the cooling coils or evaporator coils of the air 
conditioner. The incoming air may even reach the dew point in the 
air-to-air heat exchanger before reaching the cooling coils of the air 
conditioner. This is made possible by the outgoing air which is 
considerably cooler than the incoming air. The cool outgoing air does not 
return immediately to the conditioned environment but rather passes out 
through the heat transferring means during which time its potential to 
assist dehumidification is realized as it precools the incoming air. The 
process in the heat exchanger can be considered a recovery of the valuable 
cooling power of the outgoing air. The air conditioner acting alone 
without the heat exchanger dumps the cold air directly into the 
conditioned room. Thus, the heat pump capacity of the air conditioner is 
largely used to cool the room and only a limited amount of 
dehumidification is accomplished. The same air conditioner connected to a 
heat exchanger, as the two component invention, uses its heat pump 
capacity largely for dehumidification with only a small amount of cooling 
in addition. In either configuration the electrical energy consumed is 
virtually the same so the invention is much more energy efficient at 
dehumidification than just the air conditioner acting alone. 
Experiments have been performed which substantiate the theory. Additional 
clarification of the theory is made as the experimental analysis and 
results are explained. The experimental apparatus consisted of two 
identical air conditioners, one made into the invention configuration by 
attachment of an air-to-air heat exchanger (similar to FIG. 1) and the 
other air conditioner acting alone as the comparison or experimental 
control. Room air temperature and relative humidity were measured as were 
inlet and outlet air temperatures of both air conditioners and the heat 
exchanger. Power consumption to each air conditioner was measured (the 
heat exchanger is unpowered and has no moving parts) and the condensate 
from both systems was collected. It was found that the invention did work 
as the theory predicted. 
The analysis of one experiment shows an actual operating comparison between 
a conventional air conditioner and the invention. The inlet conditions 
(room conditions) for both systems was 77.degree. F. and 66% relative 
humidity. The temperature and humidity of a typical packet (one pound) of 
air are traced on a psychrometric chart as air moves through the 
respective systems. Referring to FIG. 2 of the drawings, there is shown 
the psychrometric chart for this experiment. In particular, the chart is 
in the form of a graph with temperature on the "X" axis and grains of 
water per pound of dry air on the "Y" axis. The horizontal lines on the 
chart are constant moisture lines. The relative humidity and enthalpy 
lines are at angles to the constant moisture lines. 
The conventional air conditioner performed as follows. The air entered the 
cooling coil section at Point A, with the room condition of 77.degree. F. 
and 66% relative humidity. As the air flows over the first cold coils it 
is first cooled along line AB at constant moisture content until the 
temperature is reduced to the dew point of approximately 65.degree. F. 
Then the air moves along the curved path BC during which condensation 
occurs and the dew point, which is a measure of the amount of moisture in 
the air, is reduced. Point C is the state of the air as it left the air 
conditioner and reentered the room. The total moisture removal was 
91-64=27 grains of water and the heat or enthalpy pumped out of the room 
by the air conditioner was 9.3 Btu's. 
The form of the invention tested similar to FIG. 1 performed as follows: 
The air entered the heat exchanger at Point A, 77.degree. F. and 66% RH. 
As the air progressed through the heat exchanger it was cooled to 
58.degree. F. as measured just before the air contacted the cooling coils 
of the air conditioner. Note that path AB and part of BC had been 
traversed. The air had not only been cooled to the dew point of the room 
air, Point B, 65.degree. F., but the dew point occurred in the heat 
exchanger even before the air reached the air conditioner. Entering the 
air conditioner cooling coil at 58.degree. F. the air was cooled to a low 
of 43.degree. F. The 43.degree. F. dewpoint corresponds to a moisture 
content of 41 grains per pound. Total moisture removal was 91-41=50 grains 
of water or approximately twice as much as the air conditioner system 
acting alone could produce. At this stage the enthalpy loss is 
considerably larger than 9.3 BTU's. Path DE depicts the cooling recovery 
process of the invention. The 43.degree. F. air exited the air conditioner 
and reentered the heat exchanger on its outbound path back to the room. 
The cold air cooled the heat exchanger surfaces which separated the cold 
air from the warmer incoming air. The farther along the heat exchanger 
path the cold air traveled the more it warmed up since it progressively 
transferred its coolness to the incoming air. Since the heat exchanger is 
in a counter flow configuration the outgoing air is always somewhat cooler 
than the corresponding incoming air on the other side of the heat 
exchanger surface. Thus the heat exchange continued until the cool air 
reenters the room, which is condition E on the chart, 71.degree. F. and 
36% relative humidity. As the outgoing air warmed up, its enthalpy 
increased until the net loss was 9.3 BTU's. The efficiency of the heat 
exchanger determines the exit temperature relative to the inlet. A more 
efficient heat exchanger than the one tested could have driven the dew 
point down to theoretically as low as 36.degree. F. and 30 grams of water. 
Conversely, a less efficient heat exchanger would result in less efficient 
dehumidification. 
Viewed from an energy consumption and comfort standpoint, a larger air 
conditioner acting alone with throttled air flow could also have reduced 
the dew point of the processed air to 43.degree. F. but at greater energy 
consumption. Furthermore, the 43.degree. F. air dumped directly in the 
room could progressively cool the room and make it perhaps too cold for 
comfort. It is believed that individuals within a controlled environment 
with the method and apparatus of the invention will enjoy greater comfort 
levels than with conventional air conditioning. In situations where the 
ambient temperature does not need to be reduced, but rather where only 
dehumidification is desired, the invention can result in substantial 
energy savings at about the same initial cost but with much lower 
operating cost. This is achieved by reducing the amount of Btu capacity of 
the unit and the time necessary for the unit to operate. Initial cost of a 
small air conditioner plus heat exchanger may be comparable to the cost of 
a considerably larger air conditioner of equal dehumidification capacity. 
BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to FIG. 1 of the drawings there is shown a first embodiment which 
includes a heat transferring or counterflow heat exchanger means 10 
connected with a conventional air conditioning unit 11. The air 
conditioning unit 11 is of the type used to cool a single room and is 
often positioned in a window or opening in a wall. 
In operation ambient air from the controlled environment enters the grill 
12 and passes through a filter 13. The air then passes over the baffles 14 
and 15 and into the air conditioner 11. The air passes through the 
condensing coils of the air conditioner 11 and out the exhaust port 16 
where it strikes baffle 17. The cool air passes around the baffle 17 where 
it engages the baffle 18, the baffle 19 and out the exhaust grills 20a, 
20b and 20c. A winding or labyrinth heat exchange surface 21 is provided 
whereby the air entering the air conditioner and exhausting the air 
conditioner passes thereover. 
Air entering the grill 12 and passing through the filter 13 will come in 
contact with the heat exchange surface 21 and as it passes through the 
heat transferring or heat exchanger means 10, will transfer heat to air 
being exhausted from the exhaust 16 of the air conditioner. The type and 
amount of heat exchange surface provided is determined to provide the 
desired amount of heat transfer so that the air exiting the grills 20a, 
20b and 20c is of the desired temperature and humidity. 
Suitable control means 22 can be provided to control the air conditioner 
11. In the case of existing air conditioners, the heat transferring or 
heat exchanger means 10 could be designed to fit over the intake and 
exhaust of the air conditioner while leaving the conventional controls of 
the air conditioner exposed for controlling this operation. The 
temperature and humidity of the air entering the controlled environment 
from the heat transferring and heat exchanger means 10 can be regulated by 
the thermostat of the air conditioner. Some adjustments or modifications 
may be required in the air conditioner control systems. 
Referring to FIG. 3 of the drawing there is shown an embodiment of the 
invention which might be used with existing central heating and air 
conditioning systems. The device uses a conventional condenser 30 and a 
conventional forced air furnace 31. In its air conditioning mode the 
condenser is activated and air passes through the cooling coils 32 and 
into the conduit or duct 33. Conduit portion 33 extends upwardly and 
communicates with a horizontal conduit portion 34. A plurality of 
selectively closable grills 35, 36, 37 and 38 is provided along the length 
of the conduit 34. The grill 35 as shown in its opened position so that 
air will be exhausted through it with the grills 36, 37, and 38 shown in 
their closed positions. 
The return air conduit 39 is connected with a vertical conduit 40 which 
extends upwardly into communication with a horizontal conduit portion 41 
which terminates in an inlet grill 42 where air enters the return air 
conduit. 
In operation the blower motor of the furnace 31 is activated providing for 
a flow of air as shown by the arrows in the conduit. The condensor 30 may 
then be selectively activated to cool the cooling coils 32. 
The system shown is FIG. 3 permits varying the amount of heat transferred 
from the air entering the grill 42 to the air exiting one or more of the 
grills 35, 36, 37 and 38. The heat transfer surface 43, which is 
schematically shown can be selectively utilized depending on which of the 
grills 35, 36, 37 or 38 is open. If only grill 38 is open, then maximum 
heat transfer of the entering air will be supplied to the exiting air 
which will result in greater dehumidification and a higher temperature for 
the air exiting grill 38. This would be utilized in conditions where the 
temperature was in the comfortable range but the atmosphere in the 
controlled environment was uncomfortable due to excess humidity. In 
situations when the temperature in the controlled environment exceeded a 
comfortable range then cooling could be provided by varying the amount of 
heat transfer surface 43 which was utilized. As will be apparent, as one 
progresses from right to left in FIG. 3 selectively opening and closing 
the grills 35, 36, 37 or 38 the amount of heat transfer surface utilized 
would decrease. 
Another embodiment of the system of the invention is shown in FIG. 4. This 
embodiment is similar to that shown in FIG. 3 in that it includes a 
horizontal conduit portion 34a for directing air into the room defined by 
the walls 44 and 45 and additional walls (not shown). A return air conduit 
portion 41a is also provided to direct air to a heat exchange unit 46. The 
conduits 34a and 41a include a heat exchange surface (not shown) which may 
be the same as heat exchange surface 43 in FIG. 3. Air is drawn into the 
grill 42a and passes over the heat exchange surface into the cooling and 
heating means 46. This may take the form of a condensor or the like for 
receiving heated or chilled water to provide cooling or heating as 
desired. The air passes through the cooling and heating means 46 into the 
conduit 34a where it is selectively vented through vents 35a, 36a, 37a and 
38a. As shown in the drawing, the vent 37a is open to provide the desired 
amount of heat exchange between the air in the conduits 34a and 41a to 
provide a predetermined amount of dehumidification. 
Another embodiment of the invention is shown in FIG. 5. This embodiment 
includes a cooling means 50 which may be a conventional commercial type 
air conditioner. The cooling means 50 includes a compressor 51, fan 52, 
which blows through coil means 53. A cooling coil 54 is provided to cool 
air flowing into the cooling means 50. Air exiting the coil means 53 
carries heat from the cooling means to the atmosphere as indicated by 
arrow 53a. The duct 53b can exhaust contaminated air from the controlled 
environment. Damper 53c controls whether air is recirculated or exhausted. 
The exhausted air represented by the arrow could pre-cool the incoming air 
represented by arrow 70. The cooling means 50 is of conventional type 
constructions so no further description is provided. Other types of 
cooling means could be used. One example is the use of water chilled which 
is directed through cooling coils. 
In operation, air enters the return air conduit 55 through grill 56. The 
grill 56 is positioned within the controlled environment such as a 
building as is well known in the art. Air passes through the return air 
conduit 55 into a heat transferring or heat exchanging means 57. 
The heat transferring or heat exchanging means 57 includes a heat exchange 
surface 58 which has a predetermined heat exchanging capacity. A plurality 
of baffles, 59, 60 and 62 direct incoming air and provide mixing of the 
air to increase heat transfer. Air passing through the heat transferring 
and heat exchanging means 57 is directed to a conduit 63 which directs the 
air into the cooling coil 54. Cooling coil 54 is a condensing coil in that 
it is cooled which results in condensation of moisture in the air. This 
condensate is directed out of the unit in a conventional manner. 
The air passing through the cooling coil is directed out of the heat 
exchanger via baffles 64, 65, 66, 67, and 68. 
A plurality of dampers is provided to control the amount of heat exchange 
in the air. A first baffle 69 provides for fresh air or recirculation. The 
dark arrow, 70 represents outside air. When the damper 69 is in its 
vertical position, recirculation occurs with air passing through the grill 
56. 
A plurality of dampers 70, 71, 72, and 73 determine the amount of heat 
transfer between the air entering the heat transferring or heat exchanging 
means 57 and the air passing out of it. In particular, when the dampers, 
70, 71 and 72 are substantially closed, as shown in FIG. 5, a substantial 
portion of the air leaving the cooling coil 54 passes through the heat 
exchanger past the damper 73. This results in substantial heat exchange 
and increased dehumidification. The temperature of the air exiting the 
heat exchanger is also involved. Suitable control means are provided to 
alternately open and close the dampers 70, 71, 72 and 73 to provide the 
desired heat transfer and dehumidification. 
A plurality of dampers 74, 75, 76 and 77 is also provided to alternately 
direct air through the conduits 78, 79, 80 and 81 or through the large 
main conduit 82. As will be apparent, the dampers 74, 75, 76 and 77 as 
well as the dampers 70, 71, 72, 73 and 69 may be selectively opened and 
closed to provide the desired amount of heat exchange and dehumidification 
as well as to direct the air leaving the heat exchanger into different 
rooms or areas of the controlled environment. 
While there has been shown and described a preferred embodiment of an air 
apparatus and method for passive cooling system in accordance with the 
invention, it will be appreciated that many changes and modifications may 
be made therein without, however, departing from the essential spirit of 
the invention within the scope of the claims.