Air Cooler Having Multiple Cooling Coils

Abstract

An air cooler comprising two parallel finned heat exchange coils acutely angled to the direction of airflow and located within a rectangular duct housing, each coil having a drain trough at its downstream edge. By angling the coils it is possible to provide greater total fin face area, a lower air velocity through the coils, a higher heat transfer, and less pressure drop in the airstream.

Description

THE DRAWINGS

FIG. 1 is a transverse sectional view taken through an air cooler formed under the invention.

FIGS. 2 and 3 are fragmentary sectional views taken on lines 2--2 and 3--3 in FIG. 1.

FIG. 4 through 6 are schematic views showing the FIG. 1 cooler operatively associated with other components to make up various different air conditioner assemblies.

The cooler 10 shown in FIG. 1 comprises a boxlike housing having a top wall 12 and bottom wall 14 connected at their four corners by vertical pillars 16. FIG. 2 shows two of the pillars; similar pillars would be provided at the remaining two corners of the box. The space between the two illustrated pillars 16 is occupied by a vertical panel 18 having insulation 20 adhered to its inner face. A similar panel may be provided between the other two nonillustrated pillars 16. One or more of the panels 18 can be removably connected to the pillars, as by screws, to provide side access to the interior of the duct formed by the boxlike housing.

As shown in FIG. 1 the duct may be arranged to have airflow therethrough in the directions denoted generally by numeral 22. The duct is subdivided into two separate duct sections by means of a partition 24 which extends across the entire width of the housing as measured in the arrow A direction (see FIG. 2). The space above partition 24 forms one air duct section, and the space below partition 24 forms a second separate duct section.

Each duct section contains a finned heat exchange coil 26 having a suitably number of coolant tubes 28 and plate-type fins 30. The drawings show each heat exchanger as having one row of tubes 28, but in practice each heat exchanger is preferably equipped with three rows of tubes. The plate-type fins 30 are in the plane of the paper in FIG. 1 so that the air flows between the parallel fins in moving from each space 32 to each space 34. The fins are suitably spaced, as for example 14 fins per inch, and the fins are angled with respect to the flow axis of each dust section so that the length b of each heat exchanger is appreciably greater than the transverse dimension a of each duct section. Preferably the angularity of each coil is about 25.degree., and the length of the housing is such that dimension b is approximately twice as great as dimension a. This permits housing 10 to be formed as a boxlike structure having a generally square configuration but having a total coil face area that is substantially greater than can be provided by coils arranged in upright dispositions.

CONDENSATE REMOVAL

During service the air flowing across the fins is cooled by the relatively cold fluid (water or vaporizable refrigerant) flowing through tubes 28. Moisture in the entering airstream is condensed out of the air and flows downwardly along the trailing edges of the fins 30. Ultimately this moisture is discharged into one of two drain troughs 38 which extend the full width of the airspace (dimension A). Each trough is essentially a U-shaped channel mechanism closed at its opposite ends but having an open mouth portion facing the end edges of the respective heat exchange coil 26 the mouth of each trough has a dimension d that is somewhat greater than the thickness of the coil as measured by dimension c. Therefore the air box 10 can have different gravitational orientations without hampering the condensate-trapping capability of the two troughs 38. Thus, the box can be arranged for horizontal airflow as shown in FIG. 1, or the box can be arranged for downflow application or upflow application as will be apparent hereinafter, without interfering with the action of the trough.

It will be noted from FIG. 1 that partition 24 has a slight angularity with respect to the duct axis, the partition being pitched slightly downward from front to rear, i.e., in the direction of trough 38. The lateral edges of partition 24 are turned upwardly as at 27, so that the partition serves as a tray for conducting condensate in the arrow 29 direction into the trough 38.

Condensate can form in each of the spaces 32 when coils 25 are direct expansion coils utilizing vaporizable refrigerant. In such applications the liquid refrigerant lines, refrigerant dryer, refrigerant suction line, refrigerant expansion valve, etc. can be disposed within the box in space 32. These refrigerant devices are relatively cold and have a tendency to condense moisture out of the entering airstream; the moisture gravitates into the tray formed by partition 24. Additional moisture can also form on the outer surface on the return bends 40 for each of the coils. FIG. 2 shows one return bend, but it will be appreciated that a large number of bends are necessary to interconnect the straight portions of the tubes 28. These return bends are arranged above the space circumscribed by the upper tray 24 or the lower tray 24a, both trays being essentially the same construction, and each leading to one of the troughs 38. The general arrangement is such that trays 24 and 24a are adapted to convey liquid condensate into their respective drain troughs 38.

As shown in FIG. 1, the upper drain trough 38 is connected to the lower trough via a hollow connector tube 42. Thus, moisture collected in the upper trough gravitates through tube 42 into the lower drain trough 38 and ultimately through a discharge opening 44 formed by the short discharge pipe 46.

COIL SUPPORT

The coil and condensate disposal assembly can be mounted within box 10 by various different support mechanisms. As shown in FIGS. 1 and 2, the coils are mounted in generally cantilever fashion from two upright angle irons 48, only one of which is visible in the drawings. Each angle iron 48 is suitably welded to a rear one of the pillars 16, and each angle iron extends the full housing height. Each angle iron 48 carries two generally triangular side sheets 50 and 52, each side sheet having an inturned flange 54 which is suitably bolted to a flange 55 on the tube sheet 60 of the respective coil 26. Each coil is therefore suspended from two triangular side sheets, said sheets serving to channel the outlet airstream through the box outlet. Such an arrangement prevents airflow around the ends of the respective coils, thereby insuring that essentially all of the air passes through the fin areas.

AIR COOLER ACTION

As previously noted, the coils have lengths b that are appreciably greater than the duct section dimensions a. The face area of each coil is accordingly appreciably greater than the duct cross-sectional area as defined by dimension a. Because of the area relation the air is caused to appreciably decelerate as it enters each coil; also the air is diffused along the face of the coil. The air having a relatively low linear velocity has a relatively long transition time in the fins so that the air is able to give up a substantial portion of its heat content to the fins and to the fluid in tubes 28.

It would be possible to increase the fin transition time of the air by using upright heat exchangers having deeper fins (dimensions c) and a greater number of rows of tubes. Thus finned coils having as many as eight rows of tubes are commercially obtainable. However such deep coils increase the lengths of the narrow air passages between the fins, and thus appreciably increase a larger blower, which increases space requirements and also noise emission. The illustrated arrangement, using two coils inclined or angled with respect to the direction of airflow, is advantageous in that heat transfer is achieved without large pressure drops or high linear air velocities.

The relatively low air velocity means a reduced carryover of moisture in the outlet stream. Assuming the air cooler is arranged for horizontal airflow application, the moisture tends to flow downwardly along the trailing edges 36 of the fins and into the trough 38. Some of the moisture tends to be reintrained by airlift action, but because the air velocity is relatively low the tendency toward reintrainment is lessened.

The reintrainment problems encountered in conventional units usually requires that the drain pan extend for a suitable distance beyond the coil to trap sufficient numbers of airborne droplets. With the illustrated drain trough design the condensate collection mechanism can be shorter with consequently reduction in the front-to-rear reduction of the housing.

AIR COOLER DISPOSITION

The FIG. 1 air cooler can be used in various duct systems as show in FIGS 4, 5 or 6. As shown in FIG. 5, the duct system includes a filter box 70, the previously described cooler 10, a blower box 72, and duct-type electric heater 74 having resistance heater elements (not shown) extending across the duct 74 space. This type of system may be used in a horizontal position within a crawl space or other space having a small vertical clearance. The vertical dimension of the duct sections 70, 72 and 74 can be relatively small because cooler 10 employs inclined air cooler coils.

FIG. 4 illustrates the FIG. 5 assembly with certain components juxtaposed and arranged for downflow application. In such an application the FIG. 1 cooler would be arranged so that walls 12 and 14 would be disposed vertically. The air would flow downwardly, and in the same general pattern as by arrows 22. The troughs 38 would be disposed in the lower areas of the housing, and condensate would collect in both troughs. The pipe 42 would continue to conduct liquid from one trough to the other. Condensate would be discharged through pipe 46.

FIG. 6 illustrates the system of components arranged for upflow application. In such an application cooler 10 would be disposed with its walls 12 and 14 vertical, and with drain troughs 38 at the lower end of the housing. The air would flow in a direction reverse to that indicated by arrows 22, in which case the fin edges 36 would be the leading edges and fin edges 35 would be the trailing edges. Condensate forming on edges 35 would flow into trays 24 and 24a and thence into the troughs 38 via the spaces between the fins.

Claims

I claim:

1. An air cooler comprising a rectangular air duct which includes two parallel duct sidewalls defining the general path flow through the duct; a partition generally midway between and parallel to said duct walls for subdividing the duct into two separate duct sections having transverse dimensions a ; finned heat exchange coil in each duct section; each coil taking an acute angle to the flow axis of the respective duct section; and each coil spanning substantially the entire dimension a between the respective partition and duct sidewall; the aforementioned angularity of each coil being such that each coil has a length b in the direction of flow which is appreciably greater than the duct section dimension a; said coils extending en general parallelism with one another at approximately the same angle to the aforementioned duct sidewalls; the duct being constructed so that the air is caused to flow through each duct section in the same direction; the partition acting as a flow splitter to subdivide a single incoming airstream into two separate component streams flowing through the two coils in parallel flow relationship to one another.

2. The air cooler of claim 1 wherein the duct is adapted for horizontal airflow disposition; said coils being sloped downwardly in the direction of the duct outlet; each coil having a drain trough subjacent the end thereof closest to the duct outlet for receiving condensate flowing downwardly along the fin trailing edges.

3. The air cooler of claim 2 and further comprising a connector tube interconnecting the two drain troughs so that condensate is able to drain from one trough to the other.

4. The air cooler of claim 2 wherein the partition takes the form of a first tray operable to receive condensate from the upstream face of the overhead coil; the combination further comprising a second try operable to receive condensate from the upstream face of the lowermost coil; each tray being pitched slightly from the air inlet to the air outlet so as to empty into the respective drainage trough.

5. The air cooler of claim 4 wherein each drain trough is essentially a U-shaped channel mechanism having its mouth facing an end edge of its respective coil; each coil having a thickness dimension c and each trough having a mouth dimension d which is somewhat greater than dimension c whereby the air duct is adapted for vertical airflow disposition, either upflow or downflow, such that the troughs continue to retain their condensate-trapping capabilities.