US3387647A - Air treating means including an air flow directing system - Google Patents

Description

Filed Aug. 15, 1966 0 0 r 4 1 wzwd mu 5 6 2 wa 4 7 M E M B WM v F. m E k [M z I4 [-4 MA- I z. N w 6 e 0 MN N 6 6 40 N 7 0 6 s P 10 8 Y 6 w 0. 3 B 7 6 a Z 0 Z 2 z 4. w a 2 o m, I 2 a 8 u. MA x G A. 7 s 2 A L I \H w W NAM F III. E 1|: 4 i i flm n m G. HESKESTAD ET AL June 11, 1968 AIR TREATING MEANS INCLUDING AN AIR FLOW DIRECTING SYSTEM FIE-E United States Patent 3,387,647 AER TREATING MEANS INQLUDENG AN AIR FLOW DIRECTING SYSTEM Gunnar l-Ieskcstad, 34 Seymour Terrace, Piscataway, NJ.

08854, and Daniel Gordon Galiie, 6757 (Iortiand, Aiien Park, Mich. 48101 Filed Aug. 15, 1966, Ser. No. 572,384 16 Claims. (Cl. 16532) ABTRAT OF THE DESCLQSURE An air treating means comprising two heat exchange coils arranged in parallel flow relation (side-by-side in the air duct). Air is admitted to the coil faces through a small inlet duct, and is directed to one or the other coil by boundary layer control devices. Each control device comprises an air extraction mechanism arranged to withdraw a minor amount of air from the main stream boundary layer as it passes from the small inlet duct into the larger duct containing the heat exchange coils. By controlling the amount of air withdrawn from the respective portions of the boundary layer we expect to control or direct the main stream.

This invention relates to commercial and industrial air conditioning systems, including those under development for future passenger vehicles, having the heating and cooling coils in parallel flow relationship. In such systems dampers are often used to regulate the volume of air treated by each of the coils in response to the moisture and temperature requirements of the environment being conditioned. During service, air is conveyed to the coils through ducts at a relatively high velocity for the purpose of conserving space and material. Before entry into the coils, the air is reduced to a relatively low velocity in order to provide more efiective treatment of the air over the coil surface.

In many systems the space between the supply duct and the coils is occupied by a flaring difiuser duct that is shaped with an increasing cross-sectional area in the direction of air flow. The purpose of the diffuser duct is to expand the air by having it occupy all of the duct cross-sectional area as it moves through the diffuser, and thereby be decelerated to a lower velocity at the diffuser outlet. The length of the diffuser must be sufficient to provide for complete expansion; otherwise the air will separate from the diifuser walls and expand at less than the required rate. Whenever there is incomplete expansion, a portion of the coil face does not come into contact with the air stream and greater velocities than intended exist at the coil, causing higher flow resistance.

As a corrective measure to the heat transfer problem, additional coil capacity is sometimes used in order that the part of the coil exposed to the air stream can properly carry the thermal load. Additional coil capacity is made available by increasing the fin density and the coil thickness, or by using either of the two methods separately. The net effect of moving air through a coil of increased capacity is additional flow resistance necessitated by incomplete expansion, which by itself increases the flow resistance. Abbreviated diffusers may be said to impart the following penalties:

(a) Necessitate the use of a coil with increased thermal capacity having added size, weight, and cost.

(b) Necessitate the use of a fan with increased pressure capacity, requiring more power and creating additional noise.

(c) Necessitate the use of a higher capacity fan drive mechanism and motor.

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In spite of the above penalties economics requires that the diffuser length be as abbreviated as possible to limit material and space requirements. Thus, a penalty is usually imposed on the performance of the system as a result of the abbreviated diffuser which is commonly used.

The present invention seeks to eliminate the flaring diffuser section and dampers generally found necessary under prior art practice. In accomplishing this result we employ air extraction mechanisms at the juncture between the blower discharge and the downstream duct leading to the heat exchange coils. The air extraction mechanisms are arranged to draw portions of the air stream around the corner between the blower discharge duct and transition wall leading to the large duct containing the heat exchange coils; the air draw-off action is such as to cause the main stream to become attached to the tran sition wall and more completely diffuse into all areas of the larger duct. Certain air discharge mechanisms may be arranged to exert a blowing action transverse to the main air stream, to thus cooperate with the air extraction mechanisms in obtaining directional control of the main stream. Selector valves may be employed to selectively energize the air extraction mechanisms and air discharge mechanisms, whereby the main air stream is caused to be selectively diverted through the heating coil or cooling coil.

This invention suggests the application of the air extraction effect, with or without the blowing effect, to derive the following advantages:

(a) Regulating the quantity of air through either coil.

(b) Expanding the air over the entire coil face.

(0) Minimizing flow losses through the transition duct and coil.

(d) Reducing floor space and duct length.

The air extraction principle exercises an influence on a central air stream such that when air is moving through a shortened diffuser with a stepped shape (expanding wall of diffuser is normal to direction of air flow), the air stream will deviate from its normal flow path. The amount of deviation is dependant on the width and angle of inclination of the suction slots and on the volume of air extracted through the slots located in the walls of the duct. The slots are typically inclined at an angle of 45 with the upstream Wall; they have a width equal to 3% of the smallest cross-sectional linear dimension of the approach duct, and are located immediately upstream of the step in the diffuser. I

Winter operation of a parallel coil system requires that the amount of air passing through the heating coil is varied in accordance with the load. Unheated air is bypassed through the cooling coil which is inoperative, and thereupon mixes with air from the heating coil in satisfying load requirements. Replacement of the conventional dampers with air extraction or suction slots should reflect improvements beyond the mode usually employed for winter operation. The air extraction slots would divert only as much of the air through the heating coil as necessary in fulfilling load requirements. When most of the air is being diverted through the heating coil, it is expected that the deflecting action of the air extraction slot may be supported by injecting or blowing air into the slot located on the duct wall opposite the heating coil. The air in jection technique is employed in this invention to deflect the portion of the main air stream that is least influenced by the slot action.

During milder weather as the demand for heat is diminished, less air would be diverted through the heating coil. The amount of air being injected through the slot into the main stream on the cooling coil side of the duct would be decreased; that slot would commence to extract air from the main stream with increased demand for cooling. Thus, a greater quantity of the main air stream would be directed to the cooling coil, and with the cooling coil becoming operational, air conditionin" requirements would be satisfied.

in addition to the demand for cooled and dehumidified air during summer operation, heated air is essential for tempering the air to satisfy requirements after the cooling and moisture separating process has occurred in the cooling coil. During this phase, all of the air would be directed through the cooling coil with maximum air extraction occurring throu h the slot on the cooling coil side of the duct, and maximum air injection into the main stream through the slot on the opposing duct wall. A heating coil would be located in a downstream position to temper the conditioned air at the necessary rate.

Under conventional methods the rapid expansion of air, together with deflection toward one of two coils is usually an inefficient process. The action is conventionally improved by replacing a highly divergent diffuser with one of extended length and a lower rate of wall diver gence. However, as suggested in the present invention, rapid expansion of air through a stepped diffuser equipped with suction slots is as efficient in recovering pressure as the conventional diffuser of extended length. Moreover, the new slotted diffuser represents added economy in terms of floor space and duct cost.

Other savings are reflected in the heating and cooling coil cost where less fin surface is necessary in providing an equivalent thermal capacity. This is due to the more complete coverage of air across the coil face, with the entire coil surface being effective in transferring heat at maximum coil loading. Similarly, with flow occurring through a larger area of the coil face, the air velocity diminishes due to the more complete coverage across the face. The combination of a lower face velocity and less fin surface represents a reduction in air flow resistance through the coil, resulting in reduced fan input horsepower.

Elimination of dampers from he coil face excludes the need for damper motors and connecting linkage. For the larger installations, the damper motors require considerable torque capacity and incur added expense. It is expected that the new suction slot arrangement will be less expensive compared with conventional systems.

One object of the present invention is to provide improved means for regulating the flow of air through either coil in a multi-coil air treating arrangement.

Another object is to provide improved means for causing an air stream to undergo a smooth controlled expansion as it moves from a relatively small duct into a larger duct.

Another object is to minimize energy losses due to turbulence as an air stream moves from a small duct into a larger duct.

A further object is to provide an air treating means of the dual coil type wherein both coils are as small as possible, as regards size, weight and cost.

An additional object is to provide an air treating mechanism having a fan and duct system of improved pressure capacity and sound-emitting characteristics.

An additional object is to provide an air treating mechanism occupying lesser space than corresponding prior art systems.

A further object is to provide an air treating mechanism wherein a fan discharges a highly diffused air stream directly into one or more heat exchange coils without the necessity of intervening louvers or dampers to provide directional control.

In the drawings:

FIG. 1 is a sectional view taken through an air treating means constituting one embodiment of the invention.

FIG. 2 is a transverse sectional view taken on line 2-2 in FIG. 1.

FIGS. 3 and 4 are fragmentary sectional views of portions of two ducts, showing the flow pattern therein.

Referring more particularly to the drawing, there is shown an air treating means comprising a large rectangular air duct l6 having a bottom wall 12, side walls 14 and i6, and top wall 18. Extending across duct 1% is a transverse wall 2! separating the duct into an upstream portion 22 and a downstream portion 24. in service, air in duct portion 22 is drawn into the conventional centrifugal blower housing 26, which is preferably of the double inlet type and equipped with a conventional fan wheel 28 having forwardly curved blades. The conventional center plate 3% of the wheel is arranged to be rotated within housing 26 by an external motor (not shown) whereby to draw the air into the wheel through the housing inlet eyes .32 and The air is discharged from the wheel into a rectangular duct 36 having a top wall 38, bottom wall ii-3*, and side walls 42 and 44-. The air at a relatively high pressure, as for example eight inches water gage static pressure, flows leftwardly out of duct 36 into the larger duct section rranged within the upper portion of duct section 24 is a heating coil 53 of the two row type having heat exchange fins 45 extending parallel to the duct side walls 14 and 16. Hot fluid such as water at about 200 F. may be supplied to coil 43 to heat the air as it passes between the fins 45. Arranged within the lower portion of duct section 24 is a cooling coil 46 having fins 48 extending parallel to side walls 14 and 16. Cold fluid such as water having an entering temperature of 45 F. may be supplied to coil 46 to cool the air passing between fins 48.

It will be noted that the distance between duct 36 and the entering faces of the fins 45 and 48 is advantageously relatively small, being on the order of one diameter or width of duct 36. Unless special precautions are taken the air discharged from duct 36 will tend to pass through the coil portions in direct alignment with duct 36, i.e. the upper portions of coil 46 and the lower portions of coil 43. Little or no air will flow through the lower portions of coil 46 or the upper portions of coil 43. This invention proposes a special control mechanism to provide a more even velocity distribution across the entering faces of the coils.

As shown in the drawing, the control mechanism comprises an air extraction mechanism comprising two air manifolds 5t} and 52. Manifold 56 extends across the width of wall 38 and halfway down side walls 42 and 44. Manifold 52 extends across the full width of duct wall 40 and upwardly halfway along each side wall 42 and 44. End walls or partitions 54 close and separate the respective manifolds. The general arrangement is such that manifold 50 extends about the upper half of the perimeter of duct 36 and manifold 52 extends about the lower half of the perimeter of duct 36. The manifolds do not connect with one another in a fluid sense.

Manifold 50 communicates with the main air stream through a slot 56 which preferably extends substantially the entire length of the manifold at the corner between duct 36 and transverse wall 20. One or more control ducts 58 lead from manifold 50 to a control valve 66 having a valve element 62 seated on a lower seat 64 when solenoid 66 is in the tie-energized condition. When the solenoid is energized the conventional armature plunger 68 is raised to move element 62 from seat 64 onto upper seat 70. A flow path is thus provided between control duct 58 and a second control duct 72.

Duct '72 includes an open end 73 extending into the inlet eye 32 of the fan 26. Therefore when the fan is operating the wheel 23 induces a flow of air through duct 72 in the arrow '74 direction. This air in turn draws air through duct 58 in the arrow 76 direction, which in turn extracts air from manifold 50. The manifold air is in turn replaced with air drawn through slot 56. This extraction of air through slot 56 has been found to minimize the separation which would otherwise occur along the downstream face of wall 20.

FIGS. 3 and 4 illustrate the general flow pattern, with and without the air extraction mechanism. As shown in FIG. 3, the air continues undeflected into the enlarged duct 24a, the space immediately adjacent duct wall 18a having nearly stagnant fluid. When air extraction mechanism St is used the air tends to fill the enlarged duct.

Apparently the air extraction slot 56 tends to deflect the main air stream around the corner between duct 36 and wall 20. A limited separated Zone 78 exists in the corner of walls 18 and 20. Beyond this zone the air stream has diffused so that it substantially completely fills the large duct section 24. The air in effect undergoes a smooth controlled expansion with a minimum of turbulence which would otherwise be expected with the abrupt increase in duct dimension provided by transverse wall 26'. Preferably, suction slot 56 faces the downstream duct area, with the plane of the slot having an angle of about 45 degrees with respect to the walls of duct 36. The width of slot 56 is preferably between 1% and of the width of upstream duct 36.

In some cases the air-extracting effect of slot 56 may be enhanced by blowing air transversely across duct 24. There are therefore provided two additional manifolds 8t) and 82. Manifold 80 extends across the full width of duct wall 18 and halfway down the sidewalls l4 and 16. Manifold 82 extends across the full width of duct bottom wall 12 and halfway up the sidewalls 14 and 16. The ends of the manifolds are closed by partitions 84. Thus, it will be seen that manifold 80 occupies the upper half of the perimeter of duct section 24, and manifold 82 occupies the lower half of the perimeter of duct section 24. Each manifold is provided with an air injection or discharge slot 86 or 88 preferably extending substantially the full length of the respective manifold.

As shown in FIG. 1, manifold 89 communicates with a control duct 90 leading to valve 69. In the illustrated position of valve element 62, a pilot-fluid control path is provided by manifold 80, duct 99, valve seat 70, duct 58, and manifold 59'. When fan 26 is operating the static pressure in duct 24 adjacent slot 86 may be relatively high. Assuming the pressure at 86 is higher than the pressure at 56, with valve element 62 in the illustrated position air from duct section 24 would flow into manifold 89, through duct 90 in the arrow 92 direction, across valve seat '79, into control duct 58 and eventually out through slot 56. The air blowing out of slot 56 would attempt to deflect the main air stream downwardly toward coil 46. In some systems the pressure difierential might not be obtained, and the blowing effect could not be realized.

When solenoid 66 is energized to move valve 62 onto seat 70 a new pilot fluid control path is provided. This new path includes slot 56, manifold 50, duct 58, seat 64, and duct 72. Flow through this path in the arrow 74 direction will cause the main air stream to lock onto the downstream face of transition wall 20 and diffuse transversely as previously described.

The control duct system for manifolds 52 and 82 is preferably the same as the control duct system for manifolds 50 and 80; hence similar primed numerals are employed. In each case the control may be triggered by a solenoid 66 or 66. Solenoid 66 may be energized by a conventional room thermostat or ductstat responding to temperature or humidity conditions in the spaces being treated by the air treating apparatus. The heating thermostat is shown schematically in FIG. 1 as a snap switch 94 adapted to have its contacts opened and closed by a bimetal actuator 96. A similar cooling thermostat may be used to control solenoid 66'.

The solenoid valves and their controls may be so arranged that on the call for heat slot 56 functions as an air extraction slot while slot 57 functions as an air blowing slot. On the call for cooling slot 56 should function as a blowing slot and slot 57 as a suction slot. The suction effect is decidedly the predominating effect, and with certain coil dimensions the blowing operation may be eliminated or unobtainable. In that event the 3-way valves 60, 60' and air discharge manifolds 80, 82 may be eliminated in favor of simple 2-way valves connected between duct sections 90, and 72, 72. The illustrated fully open fully closed valves 60, 60' may be replaced with more expensive motor-operated modulating valves if more precise directional control of the main stream is desired. Instead of two separate valves 60 and 60' there may be employed a single multi-passage valve of the selector type programmed to provide the desired pilot-control action.

As illustrated, the inlet side of the system supply fan may be used as a suitable suction source for achieving a satisfactory air extraction action. Alternately a small vacuum pump driven by the supply fan motor or an auxiliary motor may be employed. A water or air-powered jet pump might also be used as a suction source. Under some circumstances the air extraction action could be controlled by controlling the auxiliary pump or suction source; this would be an alternative to valves 60' and 60.

It will be seen that with the described use of air suction or extraction the general objects of the invention are attained, namely regulation of air flow through either coil in a multi coil arrangement, a smooth non-turbulent expansion of the air as it moves from small duct 36 into larger duct 24, a uniform face velocity across each coil, a possible reduction in coil size and cost, the elimination of louvers or dampers between the blower and coils, and a reduction in diliuser length.

We claim:

1. Air treating means comprising a relatively small inlet duct; a relativley large outlet duct; a transition wall connecting said ducts to provide a transverse expansion of the air stream as the air flows into the outlet duct; first and second heat exchange coils arranged respectively in different spatial portions of the outlet duct in parallel flow relation with one another; a first air extraction mechanism arranged to withdraw a minor amount of air from one boundary layer portion of the air stream as it passes into the outlet duct, to thus draw the air stream toward the first heat exchange coil; a second air extraction mechanism arranged to withdraw a minor amount of air from another boundary layer portion of the stream as it passes int-o the outlet duct, to thus draw the air stream toward the second heat exchange coil; and control means operable to regulate the air flow rates through individual ones of said first and second air extraction mechanisms whereby to apportion the flow between the heat exchanger coils.

2. The air treating means of claim 1 and further comprising a suction source; said control means comprising first and second valved control passages extending between respective ones of the air extraction mechanisms and the suction source.

3. The air treating means of claim 1 wherein the control means comprises valve means controlling flow through the air extraction mechanisms, and automatic means responsive to conditions within the area serviced by the treating means for controlling the valve means.

4. The air treating means of claim 1 and further comprising a centrifugal fan arranged upstream from the inlet duct to supply a stream of air thereto; said control means comprising first and second valved control passages extending from respective ones of the air extraction mechanisms to the fan inlet, whereby said fan constitutes a suction source for the extraction mechanisms.

5. The air treating means of claim 1 wherein the control means is operable to inversely vary the relative flows through respective ones of separate control ducts communicating with individual air extraction mechanisms.

'6. The air treating means of claim 1 wherein the inlet duct has a rectangular cross section, the cross sectional width and length of the inlet duct being less than the corresponding cross sectional width and length of the outlet duct, whereby the air undergoes a two-dimensional expansion as it flows into the outlet duct.

7. The air treating means of claim 1 wherein the first air extraction mechanism comprises a manifold extending around approximately one half of the perimeter of the inlet duct at its juncture with the transition Wall, and the second air extnaction mechanism comprises a second manifold extending around approximately the remaining one half of the perimeter of the inlet duct at its juncture with the transition wall.

8. The air treating means of claim 1 and further comprising a first air discharge mechanism arranged downstream from the transition wall adjacent a perimetrical portion of the first heat exchange coil; a second air discharge mechanism arranged downstream from the transition wall adjacent a perimetrical portion of the second heat exchange coil; a suction source; said control means including structure operable to selectively connect each air extraction mechanism with its respective air discharge mechanism or suction source, whereby in one condition of the control means air may flow from a given discharge mechanism into its respective air extraction mechanism to exert a blowing action on the mainstream, and in another condition of the control means air may flow from the respective air extraction mechanism to the suction source to exert a suction action on the mainstream.

9. The air treating means of claim 8 wherein the control means includes a three-way valve, a first control duct extending between an air extraction mechanism and one chamber of the valve, a second control duct extending between an air discharge mechanism and another chamber of the valve, and a third control duct extending between the suction source and a third chamber of the valve, said valve including a first valve seat between the first and second chambers and a second valve seat between the first and third chambers.

10. The air treating means of claim 1 wherein the transition Wall extends substantially normal to the duct axis.

References Cited UNITED STATES PATENTS 2,052,869 9/1936 Coanda 230122 XR 2,191,224 2/1940 Adair 165-126 XR 2,284,764 6/1942 Parks 165-27 XR 2,303,094 11/1942 Sharpe 16527 XR 2,344,835 3/1944 Stalker 230-422 2,894,728 7/1959 Davis 165126 XR 2,944,729 7/1960 Foley et al 230-l22 ROBERT A. OLEARY, Primary Examiner.

M. A. ANTONAKAS, Assistant Examiner.

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