US3610522A

US3610522A - Air-conditioning system

Info

Publication number: US3610522A
Application number: US793835*A
Authority: US
Inventors: Richard D Tutt
Original assignee: Krueger Manufacturing Co Inc Co
Current assignee: Krueger Manufacturing Co Inc Co
Priority date: 1969-01-24
Filing date: 1969-01-24
Publication date: 1971-10-05
Anticipated expiration: 1988-10-05

Abstract

An air-conditioning system including a means for mixing primary air with recirculated secondary air. Primary air is passed through a plurality of nozzles to form a primary airstream for inducing the flow of secondary air into the stream. The secondary air enters the stream through dampers which may be positioned in accordance with the temperature requirements of the room receiving the mixed air. A primary air passageway by passing the nozzles is provided and also includes a bypass damper. A directacting thermostat senses the temperature of the room and provides pneumatic input to a pneumatic motor coupled to the dampers at the input of the secondary air. A static pressure-sensitive regulating element senses the static pressure at the exit. A second motor operates the bypass damper to admit more or less primary air to regulate the volume rate of air being supplied to the room.

Description

United States Patent [72] Inventor Richard D..Tutt 3,1 l4,505 12/1963 Kennedy 236/13 Tucson, Ariz. 2,957,629 10/1960 Curran 236/l3 [2]] p 793335 Primary Examiner-William E. Wayner [22] Flled 1969 Attorney-Drummond Cahill & Phillips [45] Patented Oct. 5, 1971 t [73] Assignee Krueger Manufacturing Company ABSTRACT: An air-conditioning system including a means for mixing primary air with recirculated secondary air. Prima- [54] AIR CONDITIONING SYSTEM air is pasfsed through a plurality of nozzles to form a primary 10 Claims 4 Drawing Figsalrstream or inducing the flow of secondary arr into the stream. The secondary air enters the stream through dampers [52] US. Cl 236/13, which may be positioned in accordance with the temperature 98/33 requirements of the room receiving the mixed air. A primary ll!- air passageway passing the nozzles is provided and also in- Fleld of Search D, cludes a by ass damper A direcbacflng thermostat gnses the 33 236/13,49 temperature of the room and provides pneumatic input to a pneumatic motor coupled to the dampers at the input of the [56] References cued secondary air. A static pressure-sensitive regulating element UNITED STATES PATENTS senses the static pressure at the exit. A second motor operates 3,053,454 9/1962 Waterfill 236/l3 the ypas damper to admit more or less primary air to regu- 3,058,664 10/1962 Donahue 236/13 late the volume rate of air being supplied to the room.

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RICHARD D. TUT T ATTORNEYS AIR-CONDITIONING SYSTEM The present invention pertains to air-conditioning systems, and more particularly, to those systems utilizing apparatus for mixing primary air under relatively constant pressure and secondary air that is to be recirculated.

In air-conditioning systems wherein substantial heat is generated in the rooms being air conditioned, it is common practice to utilize the heat thus generated to temper the incoming or primary conditioned air. In such'installations, the air in a room being conditioned is free to communicate through a ceiling into a plenum space immediately thereabove; the plenum may be formed by the space between the ceiling and a suspended false ceiling such as commonly found in commercial structures. The heat generated by business machines, lighting fixtures and persons in the room warms the air which then rises and passes into the plenum space. Cool conditioned air is admitted to the room in accordance with the temperature requirements as sensed by the thermostat. The incoming conditioned air may conveniently be tempered by inducing and mixing part of the secondary air therewith for subsequent recirculation. Prior art systems have typically mixed the primary and secondary air by means of controlling dampers on primary and secondary air inlet passages to a mixing box; the dampers are positioned in accordance with the temperature requirements of the room to mix various proportions of cool primary and warm secondary air. Difficulties are encountered, however, when the design requirements of the system dictate a constant volume rate; in the latter case, the total volume per unit of time of mixed air must be constant. The constant volume is achieved by a precise mechanical connection of the dampers admitting primary and secondary air to the mixing box. This complex and expensive arrangement is not entirely satisfactory since the positioning of the respective dampers is not precisely linear and to achieve and maintain a constant rate of flow, the dampers must assume positions which are not readily achievable when they are interconnected.

It is therefore an object of the present invention to provide an air-conditioning system utilizing air mixing apparatus to deliver a constant volume rate of mixed primary and secondary air.

It is another object of the present invention to provide apparatus for utilizing a primary airstream to induce the flow of secondary air while maintaining a constant volume rate.

It is still another object of the present invention to provide an air-conditioning system including apparatus for mixing primary and secondary air and wherein the secondary airflow is controlled in accordance with the temperature requirements of the room being conditioned and the primary airflow is controlled in accordance with a predetermined static pressure.

These and other objects of the present invention will become apparent to those skilled in the art as the description thereof proceeds.

Briefly, in accordance with the embodiment chosen for illustration, a unique air-mixing box and associated apparatus are positioned in the plenum space between a ceiling and a lower suspended false ceiling. The inlet to the box is connected to a conventional primary air duct. The primary air passes into the box and through internally mounted nozzles to increase the velocity of the primary air. Openings are provided in the box in the vicinity of the nozzles for admitting secondary air present in the plenum space into the box to subsequently be mixed with the primary air. Dampers are provided for restricting these openings and are positioned by attachment to a pneumatic motor. The motor, in turn, is energized by connection to a direct-acting pneumatic thermostat which senses the temperature of the room being conditioned and accordingly adjusts the dampers to permit more or less secondary air to be mixed with the primary air, thereby tempering the primary air. A bypass passageway is provided within the box, bypassing the nozzles so that primary air flowing through this passageway does not pass through the nozzles and does not induce the flow of secondary air; the passageway is provided with a bypass damper. The bypass damper is connected to a second pneumatic motor which is energized from a static pressure controller having a sensing element at the exit of the mixing box. A predetermined static pressure may thus be maintained at the exit of the box without regard to the position of the secondary air inlet dampers since the primary air bypass damper will insure that the proper total volume of air is provided.

The present invention may more readily be described by reference to the accompanying drawings, in which:

FIG. 1 is a perspective view, partly schematic, of an air-conditioning system incorporating the teachings of the present invention.

FIG. 2 is a longitudinal cross-sectional view of a portion of the apparatus of FIG. 1.

FIG. 3 is a top view of the primary air nozzles used in the apparatus of FIGS. 1 and 2.

FIG. 4 is a schematic control diagram of an air-conditioning system incorporating the teachings of the present invention.

Referring now to FIGS. 1, 2, and 3, the apparatus shown therein may conventionally be mounted in the plenum formed by the space between a ceiling and a false ceiling. This plenum space will, as mentioned previously, act as a collector of secondary air by reason of openings provided in the false ceiling to permit the upward flow of the warm air in the rooms to be air conditioned. The warm air to be recirculated (secondary air) is derived from lighting fixtures, etc. A primary air duct 10 will usually be connected to a source of cool primary air (not shown) that will operate at a substantially constant static pressure. However, in some instances it may be desirable to include a static pressure controller such as shown at 11 to insure that the static pressure of the primary air being supplied to the air conditioned spaces is at a predetermined pressure. The relatively constant pressure primary air is thus delivered through a duct 12 to the mixing box 13. The mixing box includes an inlet chamber 14 which communicates directly to a plurality of nozzles 15 for increasing the velocity of the primary air. The high-velocity stream of primary air emanating from the nozzles 15 passes into the throat 16 of a venturi section 17. The reverse tapering of the venturi terminates in a rectangular outlet section 19.

A pair of

induction ports

21 and 23 are provided on opposite sides of the box and are positioned adjacent to the nozzles 15 to permit the induction of secondary air into the primary airstream. The induction ports are each provided with

induction dampers

25 and 27 respectively which may be rotated about their respective axes as illustrated by arrow 29 to thereby adjustably restrict the flow of secondary air into the induction ports. A bypass passageway 30 communicates with the chamber 14 and provides a passageway for the primary air around the nozzles 15 and into the throat 16 of the venturi. Primary air thus following the bypass passageway 30 will not induce the flow of secondary air into the box 13 through the

induction ports

21 and 23. A bypass damper 32 is pivoted about a shaft 33 and may be positioned to restrict the flow of primary air through the bypass passageway. The outlet 19 of the box 13 may conveniently be connected to a rectangular cross-sectioned duct 35 which in turn supplies branch ducts such as that shown at 37 connected through a down duct 38 to a conventional room diffuser 39. Obviously, the diffuser 39 provides an outlet through the false ceiling in the room to be conditioned.

The positioning of the

induction dampers

25 and 27 is achieved by connecting a pneumatic motor 40 to the shafts 41 of the dampers as the latter extend through the sidewall of the box 13. Similarly, the bypass damper 32 is positioned by connecting the shaft 33 to a pneumatic motor 42. The

pneumatic motors

40 and 42 are conventional commercially available devices that receive air under pressure and provide an output shaft positioned in response thereto. In some instances, as will be explained more fully hereinafter, a subcooling damper may be provided in the primary air duct 12 and may be pivoted about a shaft 50 to permit positioning of the damper by a pneumatic motor 51.

Referring now to FlG. 4, the control diagram for the system of the present invention will be described. A connection is made via conduit 60 to a source of compressed air of the type commonly utilized in pneumatic control systems. The pressure of such systems may typically be approximately 20 p.s.i.g. The pneumatic pressure is supplied to a conventional static pres sure controller 61 and to a conventional direct-acting pneumatic thermostat 62. The thermostat 62 will sense the temperature at a desired location and will admit air under pressure to the pneumatic motor 40 in accordance with the deviation between the sensed temperature and the selected temperature. The pneumatic motor will respond by repositioning its output shaft to thus reposition the

induction dampers

25 and 27. The mechanical connection between the pneumatic motor and the shafts 41 of the induction dampers is shown schematically by dashed lines. It will be obvious to those skilled in the art that there are enumerable ways in which the linear positioning of the pneumatic motor output shaft may be translated to rotational positioning of the shafts 41. The static pressure controller receives air under pressure from the compressed air source through the conduit 60 and provides pneumatic pressure through conduit 65 to pneumatic motor 42 in accordance with the static pressure sensed by the sensor 66. The pneumatic motor 42 is connected to the shaft 33 of the bypass damper 32 (FIG. 2). The sensor 66 and the static pressure controller are commercially available and well-known devices and need not be discussed further.

The operation of the system of the present invention may now be described. Assuming a quiescent state has been achieved in the room to be conditioned, the bypass damper 32 and

induction dampers

25 and 27 will be at predetermined positions to provide the necessary static pressure as sensed by the sensor 66. if the room temperature should rise above the setting of the thermostat 62, pneumatic pressure would be admitted to the pneumatic motor 40 which would subsequently rotate the induction dampers in a manner to reduce the amount of secondary air being induced. The ratio of primary to secondary air would thus be changed in favor of providing cooler mixed air. The increased restriction to the flow of recirculated secondary air will reduce the pressure at the outlet 19 of the box 13. The sensor 66 detects the reduced static pressure and will cause the static pressure controller 61 to admit correcting pneumatic pressure to the pneumatic motor 42. The change of pneumatic pressure provided to the pneumatic motor 42 will cause the bypass damper 32 to reduce the restriction to the flow of primary air through the bypass passageway 30. The total volume rate provided to the air-conditioned room will thus remain constant since the static pressure at the output of mixing box 13 will remain constant regardless of the ratio of primary to secondary air. No interconnection between primary air dampers and secondary air dampers is required and the precise interrelationship of the positioning of the primary and secondary air dampers may be achieved. It may therefore be seen that the induced warm air quantity is controlled by the room thermostat while the cool primary air quantity is controlled by changes in the total air discharged from the mixing box; the end result of the independent control of the primary and secondary air is a constant volume of air being provided to the conditioned room.

In some circumstances, such as nighttime with no persons occupying the room and lighting fixtures, etc. having been turned off, there is insufficient warm recirculated air to maintain the desired temperature. Under these circumstances, it may be advisable to utilize a primary air damper mounted on the shaft 50 to regulate the primary air being provided to the mixing box 13. Thus, -when the thermostat 62 indicates that the temperature is too low and the repositioning of the induction dampers 25 and 27rby the pneumatic motor 40 fails to result in the adequate rise in temperature, the conditioned reduction of the temperature actuates pneumatic motor 51, thus closing the primary air duct 12. The subcooling operation obviously is not constant volume but is frequently justified since properly designed air-conditioning systems arrive at this state only during unoccupied hours not requiring constant volume operation.

As mentioned previously, utilization of compressed air components is well known in the art. For example, the 20 p.s.i.g. compressed air source operating on the thermostat 62 will conventionally result in operating pressure at the output of the thermostat in the range of from 2 to 15 p.s.i.g. Pneumatic motor 40 is conventionally chosen to be responsive to the sensed temperature for positioning the normally closed induction dampers and operates at pressures of from 3 to 8 pounds while the pneumatic motor 42 is chosen to close the otherwise normally open bypass damper at pneumatic pressures of from 3 to 8 pounds in response to sensed static pressure. Similarly, pneumatic motor 51 is responsive to pressures supplied thereto of from 8 to 13 pounds.

Numerous static pressure controllers are available on the market, a satisfactory controller being Model PR 269 CAV- HP regulator manufactured by the Powers Regulator Company; numerous pneumatic motors are also commercially available on the market, such as, for example, the Robertshaw Model M504. It will be obvious to those skilled in the art that a variety of arrangements may be used for the interconnection of the various elements of the present invention. For example, it may be entirely possible to substitute electrically operated components for the pneumatic components described in connection with the embodiment chosen for illustration.

lclaim:

1. In an air-conditioning system having a source of primary air under constant pressure and having means for collecting and storing secondary air for recirculation, the improvement comprising: a mixing box having an outlet; a nozzle mounted in said box and connected to said source of primary air for increasing the velocity of said primary air; an induction port in said box positioned adjacentsaid nozzle and communicating with a source of secondary air for inducing the flow of secondary air into the box and into a stream of primary air emanating from said nozzle; an induction port damper for restricting the flow of secondary air into said box; means defining a bypass passageway in said box connected to said source of primary air and bypassing said nozzle; a bypass damper for restricting the flow of primary air in said bypass; means responsive to the temperature of a selected location for positioning said induction port damper to control the flow of secondary air into said box; means responsive to the static pressure at the outlet of said box for positioning said bypass damper to provide a constant total volume rate of flow in said box outlet.

2. The combination set forth in claim 1, wherein said means responsive to the temperature includes: a thermostat; a motor connected to said induction port damper for receiving energy from said thermostat and altering the position of said induction port dampers.

3. The combination set forth in claim 2, wherein said thermostat is a direct-acting pneumatic thermostat and wherein said motor is a pneumatic motor.

4. The combination set forth in claim 2, wherein said means responsive to the static pressure includes a static pressure sensor positioned at the outlet of said mixing box connected to a static pressure controller for regulating energy supplied to a motor connected to the bypass damper.

5. The combination set forth in claim 4, wherein said motor is a pneumatic motor.

6. Apparatus for use in an air-conditioning system, comprising: a mixing box having an inlet and an outlet for mounting in a plenum containing secondary air; a plurality of nozzles mounted in said box and connected to said mixing box inlet; a plurality of induction ports in said box positioned adjacent said nozzles, said induction ports opening to the exterior of said mixing box for admitting secondary air into a stream of primary air emanating from said nozzles; a plurality of induction port dampers for restricting the flow of secondary air into said box; a bypass passageway extending from said box inlet around said nozzles for admitting primary air to said box bypassing said nozzles; a bypass damper mounted in said passageway for restricting the flow of primary air in said bypass; means responsive to the temperature of a selected location for positioning said induction port dampers to control the flow of secondary air into said box; means responsive to the static pressure at the outlet of said box for positioning said bypass damper to provide a constant total volume rate of flow at said box outlet.

7. The combination set forth in claim 6, wherein said means responsive to the temperature includes: a thermostat; a motor connected to said induction port damper for receiving energy from said thermostat and altering the position of said induc-

Claims

1. In an air-conditioning system having a source of primary air under constant pressure and having means for collecting and storing secondary air for recirculation, the improvement comprising: a mixing box having an outlet; a nozzle mounted in said box and connected to said source of primary air for increasing the velocity of said primary air; an induction port in said box positioned adjacent said nozzle and communicating with a source of secondary air for inducing the flow of secondary air into the box and into a stream of primary air emanating from said nozzle; an induction port damper for restricting the flow of secondary air into said box; means defining a bypass passageway in said box connected to said source of primary air and bypassing said nozzle; a bypass damper for restricting the flow of primary air in said bypass; means responsive to the temperature of a selected location for positioning said induction port damper to control the flow of secondary air into said box; means responsive to the static pressure at the outlet of said box for positioning said bypass damper to provide a constant total volume rate of flow in said box outlet.

7. The combination set forth in claim 6, wherein said means responsive to the temperature includes: a thermostat; a motor connected to said induction port damper for receiving energy from said thermostat and altering the position of said induction port dampers.

8. The combination set forth in claim 7, wherein said thermostat is a direct-acting pneumatic thermostat and wherein said motor is a pneumatic motor.

9. The combination set forth in claim 7, wherein said means responsive to the static pressure includes a static pressure sensor positioned at the outlet of said mixing box connected to a static pressure controller for regulating energy supplied to a motor connected to the bypass damper.

10. The combination set forth in claim 9, wherein said motor is a pneumatic motor.