Heat exchanger for stationary air conditioning system with improved water condensate drainage
A heat exchanger in a cabinet space for use in a stationary air conditioning system, wherein the heat exchanger has a pair of substantially horizontal manifold tanks engaged to a plurality of substantially vertically oriented flow tubes bent into substantially an L shape having a bend angle sufficiently steep that condensate runs along the surface under the force of gravity. Furthermore, the heat exchanger has improved fins and is angled in the horizontal direction for less inhibited drainage of condensate.
This application claims priority to U.S. Provisional Application Ser. No. 60/779,630 filed on Mar. 6, 2006.
TECHNICAL FIELDThis invention relates to heat exchangers used in stationary or residential air conditioning systems, and particularly to a heat exchanger used in an outdoor cabinet of the type having a generally rectangular prismatic shape of limited height, depth and frontal area.
BACKGROUND OF THE INVENTIONStationary air conditioning systems employ an outside heat exchanger that exchanges heat with the outside or ambient air, and an indoor heat exchanger that exchanges heat with the indoor air. In systems used strictly for cooling, the inside heat exchanger operates always as an evaporator (and generally only during warm months), while the outside heat exchanger operates only as a condenser. As such, the inside heat exchanger (evaporator) is subject to water condensation on its cold outer surfaces, while the outside heat exchanger is not. Some provision must be made to drain the indoor evaporator, but that is not an issue with the outdoor condenser. In so called heat pump applications, where the refrigerant flow and heat exchanger function is switched from cold to warm months, the outside heat exchanger acts as an evaporator in colder months. As such, surface water condensation is an issue, and a more critical issue than with the indoor heat exchanger, since it is subject to frosting or icing. This is especially critical when a defrosting operation is run on the outside heat exchanger. Failure to drain off the melted surface water can result in a harder freeze once the defrosting operation is halted.
Possible surface condensation drainage schemes are affected by the type of heat exchanger construction, and by the available installation space for the heat exchanger. Historically, the typical heat exchanger construction has been expanded copper tubing with flat, so called plate fins. Flat plate fins drain relatively easily when oriented vertically (with the tubes horizontal). A simple trough under the bottom edge of the core serves to collect the drainage. With inside heat exchangers, installation is often in a duct which is limited in vertical space (parallel to the direction in which gravity acts), but not as limited in horizontal space. Also, with duct mounted indoor heat exchangers, the fan source of forced air flowing through the duct is generally more remote from the inside heat exchanger, so its shape and installation orientation are generally determined strictly by questions of drainage and available space, with no need to accommodate the shape of a proximate fan or blower. In order to get more heat exchanger capacity within a duct volume of limited vertical space, it is known to bend the core into a symmetrical V shape, presenting two wings to the air flow, which together comprise more surface area than just a single vertical slice of the duct volume would provide. When the core construction is the plate fin and expanded tube type, the V may be oriented with the apex vertical, as seen in U.S. Pat. No. 5,062,280, and a V shaped trough below would serve for drainage. If the core construction is instead a so called tube and center type, with flat flow tubes fed at opposite ends by manifold tanks, and corrugated fins brazed between the tubes, then it is the flat tubes which become the more convenient drainage surface, as opposed to the flat fins. The core can be simply oriented with the tubes vertical, and the tanks above and below, with a trough below the lower tank. If it is desired to pack more heat exchange capacity into the duct space, a symmetrical V shape can be created by bending the tubes in the middle (which is far easier than bending the tanks) and the resulting V shape oriented with the bend at the bottom, and both tanks in a plate above the bend, as disclosed in U.S. Pat. No. 5,279,360. A lower trough below the bend collects the condensate. The angle of the V bend is sharp, less than 90 degrees, so that the tubes are still close to a vertical orientation to drain well under the force of gravity.
Some indoor heat exchangers are incorporated not in ducts with remote air supply, but in wall mounted units with proximate squirrel cage type fans. Examples may be seen in U.S. Pat. Nos. 5,918,666 and 4,958,500. In these units, horizontal space is more limited than the available vertical installation space. Consequently, a tube and flat plate fin type core is bent in a much more shallow V, and oriented with one tank above, one below, so that the flat fins are, if not vertical, at least oriented in vertical planes to enhance drainage. Again, a trough below the lower edge of the core collects condensate.
In the case of outside heat exchangers used in heat pump applications, as noted, condensate drainage is even more critical, but the installation and mounting considerations are different, and drainage is likewise dependent on the available installation space and the type of core construction. One typical configuration is barrel shaped or cylindrical, with a central fan and a cylindrical heat exchanger surrounding the central fan. With an expanded tube and plate fin type of core, the entire core is bent into a cylindrical shape, and the plate fins are oriented vertically, in planes that basically radiate from the central axis of the cylinder. Being vertically oriented, drainage is fairly good. Replacing the cylindrical or barrel shaped core with a manifold tank and flat tube construction presents two alternatives, straight vertical tanks with tubes bent into a C shape and lying in horizontal planes, or straight, vertical tubes with the manifold tanks bent into a C shape. Flat tubes lying in horizontal planes are obviously poor candidates for surface condensate drainage, while it is difficult to bend anything but simple manifold shapes out of a straight line. Cylindrical, one piece tubular manifolds may be fairly easily bent, but heavier, two piece box shaped manifolds would be difficult to bend.
Another typical configuration for outside heat exchangers is shown in
The subject invention provides a flat tube and tank type construction capable of being installed in a rectangular prism shaped outdoor cabinet, in which most of the tube length is oriented vertically for good drainage. The disclosed embodiment provides an equivalent capacity of an L shaped core, but the manifold tanks are straight and do not require bending.
In the embodiment disclosed, the manifold tanks are both straight and substantially horizontally oriented, one at the top and one at the bottom, but the two tanks are not located directly in line with one above the other. Instead, one tank is offset relative to the other, with the flow tubes bent into a basic L shape as they extend from one tank to the other. The majority of the length of each tube is straight and vertical, so that most of the area of the core lies in a plane parallel to the front grill of the cabinet. Each shorter bent section of tube is bent not at a ninety degree angle, as in the prior art described above, but at a shallow angle relative to the horizontal that is just sufficient to allow condensed surface water to run along and drain of the shorter section of the tube. The angle necessary for the water to run is shallow enough that the vertical projection of the shorter section tube does not add unduly to the vertical height of the cabinet. In the embodiment disclosed, the offset tank is the lower tank, and the lower tank is also tilted slightly, so that condensed water running down the tubes and hitting the lower tank also runs along the length of the lower tank to an end thereof, concentrating at a point for easier removal.
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Variations in the disclosed embodiment could be made. The bent tube sections 64B could be placed at the top of the available space, the entire heat exchanger 58 being flipped vertically, in effect, providing essentially the same capacity in the same volume. Or, an additional bent section could be provided at the top, providing more capacity, which occupying slightly more vertical space. Regardless, most of the core area and tube length would be vertically oriented, while the bent sections would provide more capacity without detracting from the outer surface condensate drainage.
Claims
1. A heat exchanger for use in a stationary air conditioning system having a heat exchanger cabinet space in substantially the shape of a rectangular prism with a predetermined height, a predetermined depth, a substantially vertical front grill area, and an air fan spaced horizontally from said front grill area, and in which air conditioning system a refrigerant heat exchanger contained in said cabinet space is subject to surface condensation from air passing thereover, said heat exchanger comprising,
- a pair of substantially horizontal and straight manifold tanks, one near the top of said cabinet space and one near the bottom, both of which are oriented substantially horizontally,
- and a plurality of substantially vertically oriented and parallel refrigerant flow tubes running from said top to said bottom tank, each tube being bent into substantially an L shape with a substantially vertically oriented straight section oriented substantially parallel to said front grill, and a substantially bent section having a bend angle from the horizontal that is sufficiently shallow that the vertical projection of said bent section fits within said predetermined height and depth and sufficiently steep that water condensed on said bent section runs along the surface thereof and under the force of gravity so as to drain therefrom.
2. A heat exchanger as recited in claim 1 further comprising:
- corrugated fins conjoining said flow tubes, wherein said fins have fin crests brazed to said flow tubes and means to provide condensate drainage through said brazed fin crests.
3. A heat exchanger as recited in claim 2 wherein said means to provide condensate drainage through said brazed fin crests include elongated louvers constructed in said fins, wherein said louvers form a pattern of angled lead louvers and angled trailing louvers.
4. A heat exchanger as recited in claim 3 wherein said fins are oriented so that said lead louvers are in the same general direction as the natural direction of condensate flow for less inhibited condensate drainage through said louvers.
5. A heat exchanger as recited in claim 1 wherein said heat exchanger is positioned between said fan and said front grill, and below said fan.
6. A heat exchanger as recited in claim 1 wherein said bent angle of said flow tube is about or greater than 10 degrees relative to the horizontal.
7. A heat exchanger as recited in claim 1 wherein said manifold tank near bottom of said cabinet is angled at about 5 degrees or greater relative to the horizontal.
8. A heat exchanger as recited in claim 1 where in said heat exchange is formed of brazed aluminum.
9. A heat exchanger as recited in claim 1 wherein said manifold tanks comprise of:
- a thick gauge aluminum base; and
- a clad aluminum slotted plate, wherein said slotted plate is brazed onto said aluminum base.
10. A heat exchanger for an air conditioning system with improved condensate drainage comprising of:
- a plurality of vertically oriented parallel refrigerant flow tubes having opposing tube end openings;
- top and bottom manifold tanks, wherein said tanks are substantially horizontal and hydraulically engaged with said respective tube end openings; and
- fins conjoining said flow tubes, wherein said fins have elongated louvers for directing condensate drainage;
- wherein said flow tubes are bent into substantially an L shape having a longer bent section and shorter bent section.
11. A heat exchanger as recited in claim 10 wherein said shorter bent section is located near said top manifold tank.
12. A heat exchanger as recited in claim 10 wherein said shorter bent section is located near said bottom manifold tank.
13. A heat exchanger as recited in claim 10 wherein said heat exchanger is angled at about 5 degrees or greater relative to the horizontal.
14. A heat exchanger of claim 10 wherein said substantially vertical flow tubes are bent about 10 degrees or greater relative to the horizontal.
15. A heat exchanger as recited in claim 10 wherein said elongated louvers form a pattern of angled lead louvers and angled trailing louvers, wherein that said lead louvers are oriented in the same general direction as the natural direction of condensate flow.
16. A heat exchanger for use in an air conditioning system positioned within a vented cabinet, said heat exchanger comprising,
- a pair of substantially horizontal manifold tanks, one near the top of said cabinet and one near the bottom;
- and a plurality substantially vertically oriented and parallel flow tubes running from said top to said bottom tank, each tube being bent into substantially an L shape with a longer, substantially vertically oriented straight section, and a substantially shorter bent section having a bend angle from the horizontal that is sufficiently shallow so that water condensed on said bent section runs along the surface thereof and under the force of gravity so as to drain therefrom.
17. A heat exchanger as recited in claim 16 wherein said bottom manifold tank is angled at about 5 degrees or greater relative to the horizontal.
18. A heat exchanger as recited in claim 17 wherein said bent angle of said tube is equal to or greater than 10 degrees relative to the horizontal.
19. A heat exchanger as recited in claim 18, further comprising fins conjoining said flow tubes, wherein said fins have elongated louvers for directing condensate drainage.
20. A heat exchanger as recited in claim 19 wherein said elongated louvers form a pattern of angled lead louvers and angled trailing louvers, wherein that said lead louvers are oriented in the same general direction as the natural direction of condensate flow.
21. A heat exchanger for use in a stationary air conditioning system having a heat exchanger cabinet space in substantially the shape of a rectangular prism with a predetermined height, a predetermined depth, a grill area, and an air fan spaced from said grill area, and in which air conditioning system a heat exchanger contained in said cabinet space is subject to surface condensation from air passing thereover, said heat exchanger comprising,
- a pair of substantially horizontal and straight manifold tanks, one near the top of said cabinet space and one near the bottom, both of which are oriented substantially horizontally,
- and a plurality of substantially vertically oriented and parallel flow tubes running from said top tank to said bottom tank, each tube being bent into substantially an L shape with a substantially vertically oriented straight section, and a substantially bent section having a bend angle from the horizontal that is sufficiently shallow that the vertical projection of said bent section fits within said predetermined height and depth and sufficiently steep that water condensed on said bent section runs along the surface thereof and under the force of gravity so as to drain therefrom.
Type: Application
Filed: Nov 15, 2006
Publication Date: Sep 6, 2007
Inventors: Henry Earl Beamer (Middleport, NY), Robert Michael Runk (Lockport, NY)
Application Number: 11/599,836
International Classification: F24B 1/06 (20060101); F28D 1/02 (20060101);