Air conditioning apparatus

G. W. WOOD

AIR CONDITIONING APPARATUS

Filed Jan. 13, 1959

May 9, 1961

2,983,484

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INVENTOR.

GEORGE W. WOOD

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ATTO

2,983,484

Patented May 9, 1961

United States Patent Office

2,983,484

AIR CONDITIONING APPARATUS

George W. Wood, West Springfield, Mass., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania

Filed Jan. 13, 1959, Ser. No. 786,594

Claims. (CI. 257—137)

This invention relates to air conditioning apparatus and more particularly to air flow systems in compact, Unit type or self-contained air conditioners. It deals more particularly with the noise and efficiency involved in directing air against the inlet face of a tinned tube heat transfer unit which serves to change; the temperature of the air delivered to the enclosure.

The demand for greater compactness in air conditioning units of the type adapted to be mounted in a window or other opening of a building for cooling an enclosure has necessitated unit designs which employ other than ideal air flow systems. Particularly with respect to the room air section of such units; crowding together the components of .the units, coupled with reduction in the size of air flow passages, has resulted in .high noise levels and inefficient utilization of heat exchanger surfaces. The noise and efficiency problems arc particularly, troublesome when the location of the room air blower is such that air is directed obliquely toward the face of the heat exchanger which functions, during codling operation,' as a cooling unit or evaporator, rather than at right angles to the face of this heat exchanger, Most unit type air conditioners employ finned tube evaporators and it has been observed that air directed across the edges of the closely spaced fins causes turbulence in the air flow with resulting noise. Directing air obliquely toward the face of the evaporator also results in uneven distribution of the air flow; through, the evaporator and not-; all areas of the evaporator are effectively utilized.

It is the principal object of this invention to effect a reduction in the noise emanating from, air flow systems having the deficiencies noted above and to increase the efficiency of heat transfer between the evaporator or heat transfer unit and the air flowing therethrough.

In accordance with this invention, the face of the evaporator or heat transfer unit at which air is directed is covered by a perforated sheet which preferably possesses a surface that is smooth, except for the perforations. Air directed against the face of an evaporator, for example, first encounters and flows over this perforated sheet which, because of the small size of the openings therein, offers less resistance to air flow across its surface and causes less noise to be generated than if the air impinged directly on the bare fins of the evaporator. The perforated sheet also introduces a limited overall restriction to air flow into the evaporator and uniform air pressure is built up across the face of the sheet, which causes air to flow uniformly through all areas of the evaporator. It has been found that this restriction, though effecting a reduction in the total quantity of air passing through the evaporator, actually results in greater overall cooling capacity because of the more efficient utilization of the evaporator surfaces.

The several features, objects and advantages of this invention can be better understood from the following detailed description of the invention wherein reference is made to the accompanying drawing, forming a part hereof and in which:

Fig. 1 is a plan view of an air conditioning unit which embodies the invention and from which the top has been removed to show the interior of the unit;

Fig. 2 is a vertical sectional view through the room air section of the unit, taken along line Π—Π in Fig. 1 and having portions broken away to clarify the illustration; and,

Fig.. 3 is an enlarged fragmentary illustration of a portion of the evaporator of the air conditioner of Fig. 1.

The unit comprises a casing 11 having a partition 12 therein dividing the casing into a room air section 13 and an outdoor air section 14. The outdoor air section 14 houses a motor compressor unit 15 which supplies compressed refrigerant to a condensing unit 16 which, in turn, delivers liquid refrigerant to a cooling unit or evaporator 17 disposed within the indoor air section 13. Refrigerant is vaporized in the evaporator 17 to absorb heat from room air Which is circulated over the evaporator by a motor-driven blower wheel 18. The evaporator 17 is formed of several serpentine passes of refrigerant tubing 19 which have a plurality of closely spaced, thin metal fins 20 disposed transversely of the tubes in good heat transfer relation therewith. It is to be understood that so far as the present invention is concerned the evaporator 17 is to be regarded as a heat transfer unit for changing the temperature of the air delivered to the room, the reference to an evaporator being given by way of example as a part Of the illustrated embodiment.

; Room air enters the air conditioner through one face of the casing 11 beneath the evaporator 17 and enters a scroll shaped, blower casing 21 through an inlet opening 22 provided therein. The blower wheel 18 rotates about a horizontal axis aligned with the center of opening 22, picks up air flowing through the opening and propels it through the casing 21 and upwardly onto the evaporator 17 at. the inlet thereof.

As can best be seen in Fig. 1, the air conditioning unit embodying this invention is unusually compact, in that the several components thereof have been placed as closely together as possible, leaving but minimum space for air flow through the unit. For example, the blower wheel 18 is located as close to the evaporator 17 as possible. The wheel 18 is spaced slightly below the lower edge of the evaporator 17 (see Fig. 2) and is disposed in closely spaced relation to the plane of the inner, or inlet, face of the evaporator, indicated at 23. The disposition of the blower wheel 18 and its scroll casing 21 is such that air is discharged across the inner face 23 of the evaporator 17; i.e., the general direction of air movement is more nearly at right angles to rather than parallel to the planes of the fins of the evaporator. The partition 12 is angled toward the inner face of the evaporator 17 at the end thereof opposite the blower wheel 18, as shown in Fig. 1, to direct air into the evaporator 17.

The inner face of the evaporator 17 is equipped with means for reducing noise that would otherwise result from air impinging against the inlet edges of the evaporator fins 20. This means takes the form of a smooth surface, perforated sheet 24 which covers the inner face 23 of the evaporator. The sheet 24 is preferably made of metal or plastic and is provided throughout its entire extent with a multiplicity of apertures or openings 25. Some of the openings have been omitted from the drawing to simplify the illustration. The sheet 24 is held against the inlet face of the evaporator 17 by suitable fastening means, such as nails 26 driven through openings in the sheet and wedged between fins 2® of the evaporator.

In operation, air issuing from the blower casing 21

2.983.484 ³ encounters the perforated sheet 24 and is prevented from striking the fins 20 of the evaporator 17. Sheet 24 presents a relatively smooth surface to the air flow so that the air moving thereover does not generate noise. The small openings 25 in the sheet 24 offer some resistance to air flow and pressure is built up between the sheet and the partition 12, causing air to flow evenly through the sheet and through all areas or regions of the evaporator 17.

For a typical room cooling unit, the sheet 24 preferably has openings 25 therein whose diameters are of the order of .080 inch to .095 inch, and the openings are spaced so as to provide at least 36% open area across the sheet. For example, a .032 inch thick metal sheet, having .088 inch diameter holes on .125 inch staggered equilateral centers (40% open area) has been shown to be particularly effective when used with evaporators having .007 inch thick fins spaced .076 inch apart (14 fins per inch). . It has been_; shown by tests that, while the quantity of air flowing through the evaporator 17 is reduced somewhat by the introduction of the perforated sheet 24 into the air flow path, an actual increase in the cooling capacity of the unit results from more efficient utilization of the evaporator surfaces in cooling air. Thus, the use of the perforated sheet 24 in the above described manner not only effectively reduces noise that would otherwise emanate from the room air system of the unit but, in addition, improves the operating efficiency of the unit.

While the invention has been shown in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.