Patent Application
20110290465
The present disclosure relates to an inlet distributor for an evaporator; more particularly to an inlet distributor having a plurality of orifices arranged along the length of the distributor tube.
Residential and commercial air conditioning and heat pump systems are known to employ modified automotive heat exchangers, which are desirable for its proven high heat transfer efficiency, durability, and relatively ease of manufacturability. Automotive heat exchangers typically include an inlet header, an outlet header, and a plurality of refrigerant tubes hydraulically connecting the headers for refrigerant flow therebetween. Corrugated fins interconnect adjacent refrigerant tubes to increase the available heat transfer area, as well as to increase the structural integrity of the heat exchanger. The coil of the heat exchanger is defined by the refrigerant tubes and interconnecting corrugated fins.
To meet the demands of residential and commercial applications, the size of the coil of the heat exchanger has to be increased accordingly, which in turn dramatically increased the lengths of the inlet and outlet headers. For a heat exchanger operating in evaporator mode, the increased length of the headers tends to result in refrigerant mal-distribution through the refrigerant tubes. Momentum and gravity effects, due to the large mass differences between the liquid and gas phases, can result in separation of the phases in the inlet header and cause poor refrigerant distribution through the refrigerant tubes. Poor refrigerant distribution degrades evaporator performance and can result in uneven temperature distribution over the coil. To assist in providing uniform refrigerant distribution though the refrigerant tubes, it is known to provide a distributor tube in the inlet header.
A typical distributor tube extends the length of the inlet header and includes a plurality of uniformly spaced orifices for distributing the two-phase refrigerant throughout the length of the header. The orifices are oriented at a designed angle relative to the center of the cross-section of the refrigerant tube to provide the maximum performance for the coil in a specific application. Typically, the angle of the orifices is selected based on testing a vertical slab coil design with the refrigerant tube aligned in the opposite direction of gravity.
Indoor evaporators also have the additional challenge of packaging constraints; the evaporators have to fit within the limited volume offered by the plenums of residential HVAC systems. In a slab coil design, the refrigerant tubes lie in a plane much like that of an automotive heat exchanger, and for maximum efficiency it is preferable that the refrigerant tubes are aligned in the direction of gravity with the inlet header lower than the outlet header. To provide the cooling capacity required within a limited space, two smaller slab coils are assembled into an A-Frame design or a single larger slab coil is bent into an ARC design. The A-Frame design or ARC design may need to be installed in various orientations with respect to gravity, in which the refrigerant tubes may not be aligned in the direction of gravity and the inlet header may not be lower than the outlet header. The desired distribution of refrigerant flowing through the coil may be adversely affected due to the orientation of the evaporator. There is a long felt need for an evaporator that provides good refrigerant distribution regardless of its orientation.
The invention relates to a heat exchanger assembly having an inlet header, an outlet header spaced from the inlet header, a plurality of refrigerant tubes hydraulically connecting the inlet header with the outlet header. A distributor tube having a plurality of orifices disposed in the inlet header, wherein the orifices are arranged along the distributor tube such that at least one orifice is oriented in the liquid phase of a two-phased refrigerant pressed against the internal surface of the distributor tube regardless of the orientation of the evaporator.
According to one aspect of the invention, the orifices may be substantially uniformly spaced along the length of the distributor tube in pairs or groups of four (4). Within each pair of orifices, one of the orifices may be oriented 90 to 180 degrees apart from the other with respect to the pair's respective point on a central axis. Each pair of orifices may be rotated 90 to 180 degrees from the adjacent pair of orifices. For groups of four (4) orifices, each of the orifices may be oriented 90 degrees apart from the adjacent orifice with respect to the group's respective point on a central axis. Each group of four (4) orifices may be rotated 45 degrees from the adjacent group of four (4) orifices.
In another aspect of the invention, the cylindrical refrigerant distributor tube may have a plurality of orifices spiraled along the tube. With respect to an end view of the central axis, each succeeding orifice may be offset 45 to 180 degrees from the preceding orifice.
The above configurations of orifices on the distributor tube provide that at least one of the orifices will be located within the liquid phase of the two-phase refrigerant flowing through the distributor tube regardless of the final orientations of the evaporator coil. This provides at least the advantage of improved refrigerant distribution through the refrigerant tube of the heat exchanger assembly resulting in improved heat transfer efficiency.
This invention will be further described with reference to the accompanying drawings in which:
For a typical slab coil design evaporator, the desired angle of the orifices of a distributor tube is selected based on testing of a vertical slab coil in which the refrigerant tubes are aligned in the direction of gravity with the inlet header lower than the outlet header. To accommodate the packaging constraints required for residential applications, a residential indoor evaporator may be constructed by using two slab coils in an A-Frame design or a single slab coil bent into an ARC design. Shown in
Each of the A-Frame design and ARC design provides an evaporator 10 having at least one apex 18. The A-Frame or ARC design can be installed within a HVAC plenum in various orientations with respect to the direction of gravity, in which the apex 18 may be up, down, horizontal, and any other orientation therebetween. With these varieties of possible orientations, the inlet header 12a may be located above the outlet header 12b, below the outlet header 12b, or horizontal with the outlet header 12b. The headers 12a, 12b are typically perpendicular to that of the direction of gravity, but the bottom header may be slightly angled toward the direction of gravity to facilitate condensate drainage.
A standard angle designed for the orifices 22 of the distribution tube 20 relative to the refrigerant tube 14 may not necessarily work efficiently when used in all the various potential orientations of the evaporator 10. It was found that only certain range of angles of the orifices 22 of the distribution tube 20 relative to the refrigerant tube 14 are acceptable for each of the various evaporator coil 16 orientations. In other words, orifice angles are application specific; therefore, the desired orifice range of angles has to be calculated for each specific orientation of the evaporator 10.
With reference to
It was found that if the orifices 22 were facing in a direction other than between 45 to 315 degrees with respect to the opposite direction of gravity being 0 degree, mostly vapor phase refrigerant tend to exits the orifices 22 migrating toward the refrigerant tubes 14. This is undesirable because optimal heat transfer efficiency is obtained when the refrigerant entering the refrigerant tubes is in a substantially liquid phase.
With reference to
An aspect of the invention provides a means to transport the liquid phase refrigerant from the distributor tube 20 to the refrigerant tubes 14 for efficient boiling and thus improved heat transfer performance regardless of the orientation of the A-Frame or ARC evaporator coil evaporator. This can be achieved by having orifices 22 at angles from 45 to 315 degrees, preferably between 90 to 270 degrees, with respect to the opposite direction of gravity being 0 degree, along the distributor tube 20 to ensure that at least one, but preferably a group, of orifices 22 is substantially oriented within the liquid refrigerant cross-sectional profile 30. By having one or more orifices within the liquid profile 30, the refrigerant flowing through the distributor tube 20 will push the liquid phase refrigerant through the orifices 22 and toward the refrigerant tubes.
With the above configurations of orifices 22 on the distributor tube 20 or any configuration that provides at least one orifice 22 in the desired direction regardless of the orientation of the evaporator 10 would improve the distribution of refrigerant though the refrigerant tubes 14. Therefore, if the evaporator coil 16 is positioned in any one of the various possible orientations, at least one of the orifices 22 would be located within the liquid refrigerant cross-sectional profile 30.
While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/350,123 for an ORIENTATION INSENSITIVE REFRIGERANT DISTRIBUTION TUBE, filed on Jun. 1, 2010, which is hereby incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61350123 | Jun 2010 | US |
