U.S. patent number 3,653,589 [Application Number 05/058,312] was granted by the patent office on 1972-04-04 for air conditioning system.
This patent grant is currently assigned to Carrier Corporation. Invention is credited to William L. McGrath.
United States Patent |
3,653,589 |
McGrath |
April 4, 1972 |
AIR CONDITIONING SYSTEM
Abstract
A system for supplying treated air to an enclosure including a
heat exchanger through which a heat exchange medium flows and a fan
arranged to route air to be treated over the heat exchanger in heat
transfer relation with the medium. A control operates to vary the
speed of the fan in response to changes in room temperature. At
least one outlet is provided for discharging the treated air from
the system, the outlet being positioned so that the treated air is
discharged with minimal turbulence substantially adjacent and
parallel to the ceiling of the enclosure.
Inventors: |
McGrath; William L. (Syracuse,
NY) |
Assignee: |
Carrier Corporation (Syracuse,
NY)
|
Family
ID: |
22016038 |
Appl.
No.: |
05/058,312 |
Filed: |
July 27, 1970 |
Current U.S.
Class: |
236/49.3;
236/78D; 236/78R |
Current CPC
Class: |
F24F
5/0003 (20130101); G05D 23/24 (20130101); F24F
11/76 (20180101); G05D 23/1906 (20130101) |
Current International
Class: |
F24F
5/00 (20060101); F24F 11/04 (20060101); F24F
11/053 (20060101); G05D 23/24 (20060101); G05D
23/20 (20060101); F24f 007/06 () |
Field of
Search: |
;236/38,11
;165/55,57,121-123 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Michael; Edward J.
Claims
I claim
1. A method of regulating the temperature of air circulating within
an enclosure having communication with a structure serving as an
air passage and provided with at least one outlet through which
treated air is delivered, comprising the steps of:
A. passing air to be treated through a heat exchanger in heat
transfer relation with either a relatively warm heat exchange
medium or a relatively cold heat exchange medium;
B. sensing the temperature of the air in the enclosure;
C. creating a control signal which is a function of the sensed
temperature;
D. varying the quantity rate of air passing through said heat
exchanger, the magnitude thereof being a function of the control
signal; and
E. discharging the treated air from the air passage substantially
adjacent to the ceiling of the enclosure to cause the treated air
stream to adhere to the ceiling and flow therealong to
substantially uniformly mix with the treated air in the enclosure
irrespective of the quantity of treated air delivered to the air
passage and irrespective of the temperature thereof.
2. An air conditioning system for supplying treated air to a
conditioned space, comprising:
A. means for sensing the temperature of the air in the conditioned
space;
B. means for supplying a control signal which is a function of the
sensed temperature;
C. means for receiving the control signal;
D. means operable to produce treated air, the quantity of treated
air being a function of the control signal, said means being
selectively operable to provide either relatively warm air for
heating the conditioned space or relatively cool air for cooling
same;
E. supply means for delivering the treated air to the conditioned
space, said supply means including a pressurized chamber; and
F. discharge means communicating the conditioned space with said
pressurized chamber, said discharge means having a first member
spaced from the ceiling of the conditioned space so as to define an
air passage between said member and said ceiling so that the
treated air is discharged parallel to and substantially adjacent to
the ceiling, means operable to vary the area of said discharge
means, said last mentioned means being responsive to the pressure
of the treated air in the pressurized chamber, said discharge means
causing treated air passing therethrough to adhere to the ceiling
and flow therealong to substantially uniformly mix with air in the
conditioned space irrespective of the quantity of air delivered to
the pressurized chamber and irrespective of the temperature
thereof.
Description
BACKGROUND OF THE INVENTION
This invention relates to an air conditioning system and more
particularly to an arrangement for directing the discharge of
treated air from said system in a predetermined path.
Air conditioning apparatus of the type employing a heat exchange
coil to circulate a heat exchange medium therethrough, for example
chilled or warm water, and having a fan for bringing air to be
conditioned into heat exchange relation with the medium flowing
through the coil are well known and widely employed by those
skilled in the air conditioning art. Such apparatus are generally
referred to as fan coil units.
Fan coil units are employed with central station apparatus for
cooling and heating circulating water for conditioning multi-room
buildings, such as motels, hotels, and apartments. Such apparatus
afford a relatively effective means for simultaneously conditioning
a plurality of areas in a common enclosure, while providing
individual control by the occupants of each area. In addition, fan
coil units are relatively simple to install and to maintain in
operating condition and are relatively inexpensive, making such
units particularly suitable for low-cost multiple dwelling housing.
However, certain problems have been encountered which reduce the
overall efficiency and effectiveness of their operation.
For example, the on-off cycling of the fan in a typical fan coil
unit creates annoying sound variances. In addition, an on-off type
of control does not provide uniform air distribution, and can be
annoying from the standpoint of noise. Particularly, temperature
variations of a considerable magnitude above and below the room
setpoint may be produced in portions of the room, the variations
being caused by stratification of the air during the off cycle.
To overcome these problems, a variable speed control for the fan
motor, to modulate the discharge of conditioned air from the
apparatus, has been considered. A typical fan motor control is the
subject of co-pending application, Ser. No. 58,315, filed July 27,
1970, Ronald L. Roof, inventor. The variable fan speed control
obviates the noise problem by continuously operating the fan at the
lowest speed consistent with the cooling or heating load thereon.
However, at low fan speeds, problems have resulted due to the low
velocity of the conditioned air being discharged into the
conditioned space, particularly when the air is at a relatively
cold temperature.
Such low velocity causes the air stream to lose momentum, resulting
in the relatively cold air spilling into the room, rather than
following a trajectory above the occupied space until mixing is
complete, thus causing discomfort to the occupants by producing
wide variations in temperature across the room and from floor to
head level.
In addition, with a typical discharge outlet employed with fan coil
units, considerable discoloring of the ceiling of the enclosure
being served by the apparatus will normally occur, particularly
when warm air is being supplied. The discoloring occurs due to
turbulence created between the top of the discharged treated air
stream and the lower surface of the ceiling.
The object of this invention is an improved air conditioning system
employing a novel conditioned air discharge outlet, operable to
obviate the problems hereinabove described.
SUMMARY OF THE INVENTION
This invention relates to an air conditioning system and more
particularly to an improved outlet for directing the flow of
treated air from such system in a predetermined path.
The system includes an air conditioning apparatus employing a heat
exchanger adapted to receive a heat exchange medium such as chilled
or warmed water which may be treated in a central station or other
remote location. A fan is operable to route air to be treated over
said heat exchange coil in heat exchange relationship with the
medium flowing therethrough. A temperature sensing element is
installed in the area being conditioned, and is operable to
generate a signal, the magnitude thereof being related to the
sensed temperature in the conditioned area. The signal is supplied
to the fan motor and is operable to vary the speed thereof in
proportion to the temperature of the room to vary the static
pressure produced by the treated air.
The treated air from the heat exchange medium is passed to one or
more outlets of the system. The outlets are positioned so that the
point of egress therefrom is substantially adjacent the ceiling of
the enclosure. The treated air will therefore be discharged from
the outlet substantially parallel to and adjacent the ceiling.
The air being discharged from the outlets will adhere to the
surface of the ceiling due to the natural phenomenon known as the
"Coanda effect." The treated air will flow along substantially the
entire length of the ceiling even when the volume is substantially
reduced, thus avoiding the prior art defects.
In a second embodiment, means are included in the outlet to vary
the area of the discharge opening in response to changes of static
pressure of the treated air supplied thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic and cross-sectional view of an air
conditioning system and apparatus embodying invention, and includes
a schematic wiring diagram of the control employed in the
apparatus; and
FIG. 2 is a cross-sectional view of a second embodiment of my
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to the drawings, there is shown a preferred embodiment of
an air conditioning system including the invention disclosed
herein.
Referring in particular to FIG. 1, reference numeral 10 indicates
an area in an enclosure which is to be treated by having air at a
predetermined temperature discharged therein. Although it is within
the scope of the invention to have only one such area or room being
served, it should be understood that several rooms, each employing
at least one outlet in accordance with this invention, may be
conditioned simultaneously. Area 10 includes ceiling 11.
The embodiment illustrated by FIG. 1 includes an air conditioning
apparatus 12. Apparatus 12 includes a heat exchange coil 13 to
which a heat exchange medium such as cold or warm water is supplied
via conduit 14. The heat exchange medium is supplied at a
predetermined temperature which is regulated by central station
refrigeration machinery (not shown). The heat exchange medium is
returned to the central station machinery via conduit 15. Fan 16,
operatively connected to motor 17, routes ambient air over the heat
exchange coil in heat transfer relation therewith. The ambient air
is treated by passing in heat transfer relation with the heat
exchange medium flowing through the coil. The air conditioning
apparatus is disposed in housing 20, which includes upper wall 22
and lower wall 23, said walls defining a plenum 20' . The upper
wall 22 is connected to the lower surface of the ceiling by
suitable means (not shown).
Communicating with plenum 20' is outlet 18. The opening defined by
the outlet may include a protective screening which would
discourage access to the interior of the unit, without disturbing
the air flow pattern. Outlet 18 includes a first member 21 having
an end 21' disposed substantially planar with the surface of the
ceiling. Spaced below member 21 is a second member 25. Members 21
and 25 define therebetween the exit passage for the treated air
being discharged from the apparatus.
In accordance with this invention, it is desirable to operate fan
motor 17 at a variable speed. Preferably, fan motor 17 is an
alternating current motor which is connected to a source of
alternating current, such as power line terminals L.sub.1 and
L.sub.2. Switch 30 operates to connect the motor 17 to the source
of electrical current. Switch 30 is preferably a bi-directional
gated solid state switch of a type sold under the trademark
"Triac." Switch 30 is provided with a gate 31 in series with a
secondary winding 32 of a pulse transformer by which the switch is
triggered to a conducting state by either a positive or negative
pulse being applied to gate 31. Switch 30 should be sufficiently
fast in operating so that it may be switched on during any desired
portion of each half cycle of alternating current supplied to motor
17 to arrive at a desired average power, so that the motor speed
and consequent fan speed is varied in accordance with the capacity
demand of the room served by the system.
A control circuit is provided to control the operation of switch 30
in accordance with the desired speed of the motor 17. As shown in
the drawing, a full wave diode rectifier circuit 34 is connected in
series with a dropping resistor 35 to provide a source of .C.
voltage across a series connected resistor 36 and Zener diode 37.
It will be appreciated t hat Zener diode 37 has a very low
resistance characteristic such that it provides a constant voltage
drop across its terminals. A series circuit comprising unijunction
transistor 39 having one base 40 connected in series with resistor
38 and another base 41 connected in series with the primary winding
33 of the pulse transformer is connected across Zener diode 37 to
provide a constant voltage to the series circuit.
Thermostat elements 44 and 45 are connected in series with the
constant voltage provided by Zener diode 37. Element 44 is
preferably a variable resistance element, such as a potentiometer,
that may be selectively regulated by the occupant to obtain a
desired temperature in the enclosure. Element 45 D.C. preferably a
NTC thermistor, positioned to sense the temperature of the air in
the enclosure that be explained hereinafter. Elements 44 and 45
operate in combination to provide a voltage signal, the magnitude
thereof being related to the temperature of the air sensed and to
the mode of operation of the apparatus. Switch 47 is of the type
known as a double-pole, double throw switch. Switch 47 selectively
connects the terminals of elements 44 and 45 in the circuit
depending upon whether heating or cooling is desired. The operation
of switch 47 may be controlled by bimetal 46 which is mounted about
conduit 14, in heat transfer relation therewith, to sense the
temperature of the medium flowing therethrough. When switch 47 is
in the position shown by the solid lines, the control is set for
heating mode operation. If bimetal 46 senses that a cold medium is
being supplied to coil 13, it operates to position switch 47 in the
dotted line position of FIG. 1.
Emitter 42 of unijunction transistor 39 is connected through a
diode 48, which prevents leakage current from charging capacitor
43. Additionally, the circuit includes diode 55 which prevents
current flow in an undesirable direction. Connected in series with
capacitor 43 is resistor 56. Capacitor 43 and resistor 56 combine
to provide a "fixed ramp" voltage signal to transistor 39 as is
obvious to those skilled in the art. It may be desirable in
practice to add various additional circuits to prevent spurious
gating of switch 30.
It will be appreciated that the circuit shown is illustrative
generally of a phase control type of motor speed control. The
circuit shown is merely illustrative of one type of motor speed
control system, and other types of motor speed control can be
adapted to this invention.
In operation, switch 30 is in a nonconducting state, and motor 17
is deenergized until a pulse is applied to gate 31. A charge builds
up on charging capacitor 43 at a rate which is determined by the
resistance of resistor 56. Since resistor 56 is fixed, the charging
rate of capacitor 43 is fixed. When the charge on capacitor 43
reaches a predetermined value, a predetermined voltage signal is
supplied to transistor 39. This signal is referred to as the "ramp"
voltage. The magnitude thereof is insufficient to place transistor
39 in its conductive state. To the ramp is added a second voltage
signal, which is known as the "pedestal." The magnitude of the
"pedestal" voltage is variable and is dependent upon the
temperature of the air in the enclosure and upon the mode of
operation. When the combined ramp and pedestal signal reaches a
predetermined value, transistor 39 becomes conductive, discharging
a pulse through primary winding 33 of the pulse transformer. A
pulse is thereby induced in secondary winding 32 of the pulse
transformer which is applied to gate 31 of switch 30, causing the
switch to conduct.
Switch 30 is preferably a solid state device having the
characteristic that once it is turned on by a pulse being applied
to gate 31, it remains in the conducting state until the current
through the device becomes zero. Consequently, switch 30 remains
conducting after a pulse is applied to gate 31 until the end of the
half cycle of the alternating current during which it begins
conducting. The value of the electrical components are chosen so
that switch 30 is turned on for a time during each half cycle by
the control circuit such that the power supplied to motor 17 is
just sufficient to rotate fan 16 at a speed which provides the
desired air flow over heat exchange coil 13.
As noted hereinbefore, it is desirable to operate the fan motor and
thus the fan at the lowest speed consistent with the cooling or
heating load on the air conditioning apparatus, to obviate the
difficulties presented by the on-off cycling of a typical fan coil
unit. However, as also noted hereinbefore, by producing a
concurrent decrease in the velocity of the air being discharged
when the fan speed is decreased, poor air distribution has resulted
due to air spilling into the room, particularly when the air is at
a relatively cold temperature.
If on cooling mode operation, and the temperature of the enclosure
increases above the setpoint of thermostat element 44, thermistor
45 will sense the increase and will generate a control signal so
that the speed of fan motor 17 increases. As the temperature of the
enclosure approaches the setpoint, the signal generated by
thermistor 45 will operate to reduce the speed of the motor.
Similarly, if on heating mode operation, the temperature of the
enclosure decreases below the setpoint, thermistor 45 will generate
a control signal to increase the speed of motor 17. As the
temperature of the enclosure increases, the signal generated by
thermistor 45 will operate to decrease the speed of the fan to the
desired speed to maintain the desired temperature.
The present invention relates to an air discharge outlet which
directs the air being discharged from the apparatus in a path which
will prevent the problems hereinbefore discussed. In addition,
improved heating performance will be obtained by utilization of the
novel outlet disclosed herein as shall be more fully explained
hereinafter.
In particular, by positioning the outlet to discharge the treated
air so that the air stream is directed substantially adjacent to
the surface of the ceiling, the air stream will adhere to the
ceiling and flow therealong. Thus, air circulation will be
maintained in the area being treated, irrespective of the static
pressure in plenum 20' and thus irrespective of the discharge
velocity.
The reason that the air stream will adhere to the surface of the
ceiling when discharged adjacent thereto is based upon the natural
phenomenon known as the "Coanda effect." By providing an outlet
that directs the air stream in a manner so that the advantages
produced by the Coanda effect are obtained, the prior art defects
are obviated.
In addition, when the apparatus is providing warmed air to the
enclosure, improved heating will be obtained by the employment of
the novel outlet of this invention. Heating of the room air is
obtained in two ways. The discharged treated air will induce the
room air to flow in a stream parallel thereto and to mix therewith.
By maintaining the flow of the treated air for substantially the
entire length of the enclosure, more uniform mixing with the room
air will be obtained, thus reducing stratification problems.
In addition thereto, the discharged treated air will warm the
surface of the ceiling for the entire length thereof. The surface
of the ceiling will then radiate its heat toward the floor of the
enclosure causing it to warm up, thus providing the upper and lower
surfaces of the enclosure at an elevated temperature, thus
increasing the mean radiant temperature within the enclosure,
thereby providing improved comfort.
Referring now to FIG. 2 of the drawing, there is shown a modified
outlet in accordance with this invention. In referring to the
drawings, like numerals shall refer to like parts, except for the
addition of the numeral 1 in front of all numerals employed in
discussing the components of FIG. 2. To increase the desirability
of the air conditioning system, apparatus 112 includes two heat
exchange coils 113 and 113'. A relatively cold heat exchange medium
is available at all times to coil 113 via conduit 114, the flow
thereof being controlled by valve 165. A relatively warm heat
exchange medium is available at all times to coil 113' via conduit
114', the flow thereof being controlled by valve 165'. By including
two heat exchange coils in apparatus 112, the occupant of the
enclosure may obtain heating while the occupant of a second
enclosure may obtain cooling. Preferably, valves 165 and 165' are
electrically operated.
The outlet shown in FIG. 2 includes a movable damper blade assembly
119 positioned to regulate the area of the outlet from the
apparatus as defined by members 121 and 125, in response to changes
of the static pressure in plenum 120'. It should be specifically
noted that damper blade assembly 119 operates so that all
throttling of the discharge area is done at the lower portion
thereof to maintain the flow of treated air discharged from the
apparatus substantially adjacent to the surface of ceiling 111.
It has been found that by varying the area of the discharge opening
in response to changes of the static pressure in plenum 120' in
accordance with variations of fan speed 116, a substantially
constant discharge velocity will be obtained. Damper blade assembly
119 includes a counterweight 127 attached to a rod 128. Rod 128 is
connected to a member 129 which is connected to blade 119' to move
therewith. The blade is pivotally mounted to rotate about bearing
154.
The control circuit for varying the speed of the fan motor is the
same as heretofore described and is not shown. However, the
terminals of the thermal elements will be properly positioned for
the desired mode of operation by the occupant of the enclosure,
manually moving the double-pole, double throw switch, in lieu of
the bimetal switch shown in FIG. 1. The handle for the double-pole
switch will also be connected to means for selectively energizing
either valve 165 or valve 165' to obtain the proper heat exchange
medium for the mode of operation desired.
In operation, as the speed of the fan increases in response to the
signal provided to the control circuit, the quantity of air
supplied to plenum 120' increases, thus increasing the static
pressure operating on the surface of the blade to rotate the blade
in a clockwise direction, to increase the area of the discharge
opening from the apparatus.
If the control signal to the fan motor indicates that a slower
speed is required to meet a decreased demand for treated air, a
reduced flow of air will be routed over the heat exchange coils.
The reduction in air flow produces a reduction in pressure in
plenum 120' of housing 120. Counterweight 127, due to the reduction
in force acting on blade 119', moves in a counterclockwise
direction, pivoting the blade upwardly to partially close the
discharge opening. The reduction in the discharge opening caused by
the rotation of blade 119' compensates for the reduction in static
pressure to thus maintain the velocity of the air discharged from
the apparatus substantially constant.
Irrespective of the speed of the fan, the air being discharged from
the apparatus will flow along the surface of ceiling 111 as
indicated by the arrows of FIG. 2 for substantially the entire
length of area 110. Return air to be treated by apparatus 112
passes through opening 162 in wall 160 and is directed through a
passage defined by walls 161 and 163 through a filter 164 into
housing 120. The air is then passed in heat transfer relation with
the heat exchange medium supplied to either coil 113 or coil 113'.
The air being supplied to the enclosure will follow the path as
indicated by the arrows, regardless of the mode of operation of the
system. By employment of the novel control device, improved
circulation and performance will be obtained.
In addition to the advantages previously discussed which are
obtained by operating the fan continuously, it has been determined
that a more efficient control of the humidity level, when the
apparatus is operating on cooling mode, may be obtained by
continuously operating the fan, rather than employing an on-off
cycle, or modulating the cold water flow to the heat exchange
coil.
While I have described and illustrated a preferred embodiment of my
invention, it is to be understood that my invention is not limited
thereto but may otherwise be embodied within the scope of the
following claims.
* * * * *