U.S. patent number 3,812,685 [Application Number 05/359,368] was granted by the patent office on 1974-05-28 for air conditioning process.
Invention is credited to Ted R. Brown.
United States Patent |
3,812,685 |
Brown |
May 28, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
AIR CONDITIONING PROCESS
Abstract
A process for efficiently conditioning air for beneficial use by
sequentially cooling dry air in three distinct steps, e.g.,
pre-cooling the air out of the presence of moisture, adiabatically
cooling the air in the presence of moisture, and refrigerating the
air to finally cool the air and coincidentally condense excess
moisture.
Inventors: |
Brown; Ted R. (Salt Lake City,
UT) |
Family
ID: |
26868655 |
Appl.
No.: |
05/359,368 |
Filed: |
May 11, 1973 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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172968 |
Aug 19, 1971 |
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Current U.S.
Class: |
62/93; 62/92;
62/91; 62/271 |
Current CPC
Class: |
F24F
5/0035 (20130101); Y02B 30/54 (20130101); Y02B
30/542 (20130101); Y02B 30/545 (20130101) |
Current International
Class: |
F24F
5/00 (20060101); F25d 017/06 () |
Field of
Search: |
;62/271,91,92,93,94,95 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Wye; William J.
Attorney, Agent or Firm: Workman; H. Ross
Parent Case Text
This invention is a continuation-in-part of my copending
application Ser. No. 172,968, filed Aug. 19, 1971, now abandoned.
Claims
What is claimed and desired to be secured by United States letters
patent is:
1. A process for controlling the temperature and moisture content
of air having a dew point of not more than 57.degree. corresponding
to at least 90.degree. F dry bulb temperature, sequentially
preparing an air flow path accommodating 400-600 CFM/ton net
sensible cooling;
drawing fresh dry air exclusively from a fresh air source and
through the flow path in the amounts of 400 to 600 CFM/ton net
sensible cooling;
pre-cooling the fresh air with a heat exchanger without altering
its moisture content;
scrubbing the air with recirculating water to adiabatically cool
the air; and
refrigerating the adiabatically cooled air to further cool the air
to within a range of 53.degree. to 60.degree. F and coincidentally
condensing excess moisture.
2. A process for conditioning air sequentially comprising (a) first
cooling 100 percent fresh air having a dew point of not more than
57.degree. corresponding to at least 90.degree. F dry bulb
temperature without altering its moisture content; (b) second
cooling the air adiabatically by scrubbing the dry air with
recirculating water; (c) third cooling the air by refrigeration to
within the range of 53.degree. to 60.degree. F with coincidental
condensation of excess moisture, all three cooling steps being
applied sequentially to air quantities exclusively within the range
of 400 to 600 CFM/ton net sensible cooling.
Description
BACKGROUND
1. Field of the Invention
The present invention relates to the production of low temperature
gases such as air for beneficial use in air conditioning.
2. The Prior Art
It is well-known that the efficiency of air conditioning systems is
highly dependent upon the temperature of ambient air. In summer
months, where the ambient air temperature is high, usually
refrigerated air conditioning systems are employed to produce
consistently cold air. This is particularly true where high
temperatures are accompanied by relatively high humidity levels.
So-called "swamp cooler" type air conditioning systems become of
almost negligible value when both the temperature and humidity of
ambient air are high.
Because of the great difficulty with which air is reduced to a very
low temperature in hot summer months, most air conditioning systems
have been engineered so as to recirculate and recool the
conditioned air instead of continuously cooling fresh air. This
procedure has been found necessary to keep the size and attendant
costs of air conditioning systems from becoming prohibitive. Until
this present invention, an economical and efficient way of
substantially reducing the temperature of air or other gas for
cooling purposes year-round without refrigeration has not been
known.
It is also well-known to condition air by successive cooling,
humidifying, drying and recooling steps which are inefficient,
complicated and expensive. See, for example, U. S. Pat. No.
1,863,578.
BRIEF SUMMARY AND OBJECTS OF THE INVENTION
The present invention relates to conditioning fresh air by
sequentially (1) pre-cooling dry air out of the presence of
moisture, (2) adiabatically cooling the air, and (3) refrigerating
to finally cool the air and coincidentally condense excess
moisture. Surprising efficiency and cooling results from this
process using a total fresh air system and treatment of the air in
quantities between 400 and 600 cubic feet per minute per ton of net
sensible in-space cooling.
It is, therefore, a primary object to efficiently provide air
having controlled temperature and humidity for air
conditioning.
It is another important object to provide a process for effecting
sensible cooling using a total fresh air system.
These and other objects of the present invention will become more
fully apparent from the following description and appended claims
taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1, 2 and 3 are schematic flow diagrams illustrating fluid
circuits and apparatus for reducing air temperature according to
the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
General
Heat exchange processes such as used in air conditioning systems
have always been required to have increased capacity in order to
adequately cool air when the temperature and/or the humidity of
external air climbs as in summer months and on hot days.
While it is relatively easy and comparatively inexpensive to remove
heat from gases when the temperature of the gas is high, the
difficulty with which heat is removed increases at an astonishing
rate when the temperature of the gas is already low. Thus,
generally speaking, it is much easier and less expensive to make
hot air cool than to make cool air cold using prior art techniques.
Historically, the approach used to make cool air cold was to
increase the size and capacity of cooling systems.
The present invention includes treating dry warm air out of the
presence of moisture to reduce its dew point. Air most efficiently
used with the illustrated embodiments has a dew point of not more
than 57.degree. which is low compared to the dry bulb temperature
of the warm air. This treatment can be performed by pre-cooling in
a conventional heat exchanger.
According to the present invention, the temperature of the
pre-cooled gas is then adiabatically reduced so that the gas is
cold. Adiabatic processes are defined as those processes carried
out in such a manner that heat is not exchanged between the system
and its surroundings. Thus, the adiabatic cooling step does not
require an energy input to reduce the temperature. When the gas is
adiabatically cooled according to the present invention, heat is
not actually removed from the cooling system but is reduced
psychrometrically.
If a stream of gas is intimately mixed with a quantity of
recirculating liquid at a given temperature in an adiabatic system,
the temperature of the gas will drop and its humidity will
increase. Furthermore, the temperature of the recirculating liquid
will approach the wet bulb temperature of the gas. The low
temperature gas which has been cooled adiabatically is subjected to
refrigeration which both further cools the air and coincidentially
condenses excess moisture.
When 100 percent fresh (unrecirculated) air is used for cooling,
air quantities treated according to the preferred embodiments of
the invention must necessarily be limited to a rather narrow range
in order to efficiently produce desired cooling to within a range
of 53.degree. to 60.degree. F without imposing larger than
necessary pre-cooling and refrigeration loads on the air cooling
process.
It has been found according to the present invention that
approximately 400 to 600 cubic feet of fresh air per minute per ton
(CFM/ton) of net sensible in-space cooling is an adequate amount to
develop conditioned air at a desirable temperature of between
53.degree. and 60.degree. F. The surprising efficiency of this
system can be recognized by observing that conventional fresh air
swamp coolers require about 1,000 CFM/ton even with very dry fresh
air. The efficiency of the system using this air volume range
presumes 100 percent fresh (unrecirculated) air having a dew point
of not more than 57.degree. F coincident with dry bulb temperatures
of not less than 90.degree. F. Under these climatic conditions, the
presently preferred embodiment of the invention produces 53.degree.
to 60.degree. F moisture conditioned air with surprising efficiency
and without requiring intermediate drying steps.
The FIG. 1 Embodiment
Referring more particularly to FIG. 1, warm dry air is first
obtained from a fresh air source, e.g., ambient. To maximize the
efficiency of the system, the dew point of the air should be at
least as low as 57.degree. F when air having a dry bulb temperature
of not less than 90.degree. F is used.
The warm air is first pre-cooled in a heat exchanger 62. The heat
exchanger 62 may be any one of a variety of heat exchangers which
will not add moisture to the air, one suitable type being the
fin-coil heat exchanger often called an extended surface heat
exchanger. This type of heat exchanger is very inexpensive to
acquire and operate and is very efficient at high temperatures.
Therefore, according to the illustrated embodiment of the
invention, the pre-cooled dry air emerging from the heat exchanger
62 is conducted to an air washer 64 which scrubs the air with water
or, if desired, other cooling liquid. The water used to scrub the
pre-cooled dry air is recirculated through an external circuit 66
continuously. The temperature of the recirculating water in the
circuit 66 approaches the wet bulb temperature of the air which
enters the air washer 64. Thus, the entering pre-cooled air has its
temperature adiabatically reduced from the dry bulb to near the wet
bulb temperature in the air washer.
The cold air emerging from air washer 64 is treated with a
conventional refrigeration circuit generally designated 70. The
refrigeration circuit conventionally comprises a condenser 72 and a
compressor 74 with an evaporating coil 76 interposed therebetween.
A conventional expansion valve 78 admits refrigerant fluid into the
evaporating coil 76.
The use of the refrigeration circuit 70 allows the temperature of
air emerging from the air washer to be reduced to the desired
temperature range of 53.degree. to 60.degree. F. Also, excess
moisture in the air emerging from the air washer 64 is condensed by
the evaporating coil 76 to control the moisture content of the
effluent, conditioned air. It should be observed that unless the
temperature of the air were first adiabatically reduced in the air
washer 64, a far larger and more expensive coil 76 and larger
refrigeration system 70 would be necessary to obtain the same very
cold air temperature developed according to the embodiment of FIG.
1.
The system of FIG. 1 is designed to transport and condition about
400 to 600 CFM/ton net sensible cooling. Using the air having a
57.degree. dew point, temperatures as low as 53.degree. to
60.degree. F may be economically and efficiently achieved.
Accordingly, the effluent conditioned air has a surprisingly low
temperature and controlled humidity without requiring expensive
dehumidifying (warming) and recooling steps.
The FIG. 2 Embodiment
The embodiment of FIG. 2 differs from the embodiment of FIG. 1
principally in that the evaporating coil 76 acts upon the
pre-cooled air as it traverses from the heat exchanger 62 to the
air washer 64 (i.e., from the pre-cooling to the adiabatically
cooling steps). When the pre-cooled air is further cooled, its wet
bulb temperature is lowered. Accordingly, upon adiabatic cooling in
the air washer 64, its dry bulb temperature is further reduced to
about 53.degree. to 60.degree. F.
The moisture content of the effluent from the air washer 64 will be
controlled in proportion to the amount of cooling to which the air
is subjected in advance of the adiabatic cooling in air washer 64.
The dry bulb and wet bulb temperatures imposed upon the air in
advance of the adiabatic cooling step will determine the amount of
moisture that can be added in the adiabatic cooling step.
The Embodiment of FIG. 3
The embodiment of FIG. 3 differs from the previously described
embodiments principally in that the evaporation coil 76 reduces the
temperature of recirculating water in the air washer 64.
Accordingly, the temperature of the water is reduced sufficiently
that both adiabatic and sensible cooling of the air results. The
refrigeration system 70 is specifically limited to avoid exclusive
refrigerated cooling in the air washer 64 to insure that effluent
air is within the range of 53.degree. to 60.degree. F.
Using the embodiments of FIGS. 1-3, cold air in the range of
53.degree. to 60.degree. F for air conditioning or any other
desired beneficial use can be obtained with surprising efficiency
using a 100 percent fresh air system at maximum outdoor
temperatures. Thus, the need for recirculating the same air in
order to reduce the costs of cooling is unnecessary. Furthermore,
cold air can be obtained without using large and expensive
refrigeration systems. The refrigeration system 70 required for
this combination of cooling steps has been found to be
approximately one-third the size required if conventional
recirculating air refrigeration systems are employed. Accordingly,
the advantages of a complete fresh air system can be substituted
for the lower quality, more expensive recirculating air
systems.
The invention may be embodied in other specific forms without
departing from its spirit or essential characteristics. The
described embodiments are to be considered in all respects only as
illustrative and not restrictive and the scope of the invention is,
therefore, indicated by the appended claims rather than by the
foregoing description. All changes which come within the meaning
and range of equivalency of the claims are to be embraced within
their scope.
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