Patent Grant
9746255
The present disclosure relates a heat pump heat exchanger; more particularly, to a heat pump heat exchanger having a distribution 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, as heat pump heat exchangers. A conventional automotive heat exchanger typically includes an inlet manifold, an outlet manifold, and a plurality of refrigerant tubes hydraulically connecting the manifolds 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 core of the heat exchanger is defined by the refrigerant tubes and interconnecting corrugated fins.
Heat pump heat exchangers, also known as heat pump coils, are capable of operating as an evaporator and as a condenser. A heat pump system typically includes two heat pump heat exchangers, one located outdoors and the other indoors. When the heat pump system is in cooling mode, the indoor heat pump heat exchanger operates in evaporator mode and the outdoor heat pump heat exchanger operates in condenser mode. Inversely, when the heat pump system is in heating mode, the indoor heat pump heat exchanger operates in condenser mode and the outdoor heat pump coil operates in evaporator mode.
To meet the demands of residential and commercial applications, the size of the core of the heat pump heat exchanger has to be increased accordingly, which in turn dramatically increased the lengths of the inlet and outlet manifolds. For a heat pump heat exchanger operating in evaporator mode, the increased length of the manifolds tends to result in refrigerant mal-distribution through the refrigerant tubes. The effects of momentum and gravity, due to the large mass differences between the liquid and gas phases, can result in separation of the phases in the inlet manifold and cause poor refrigerant distribution through the refrigerant tubes. Poor refrigerant distribution degrades evaporator performance and can result in uneven temperature distribution over the core.
To assist in providing uniform refrigerant distribution through the refrigerant tubes, an inlet distributor having a plurality of uniformly spaced orifices is disposed within the inlet manifold for distributing the two-phase refrigerant throughout the length of the inlet manifold. Similarly, an outlet collector having a plurality of uniformly spaced orifices is disposed within the outlet manifold for collecting the vapor refrigerant throughout the length of the outlet manifold. Since refrigerant is in a vapor phase, its volume, vapor velocity, and the resulting pressure drop along the outlet manifold or outlet collector are much higher than if it remained in a liquid phase.
Outlet pressure drop in the outlet collector reduces performance by both constraining refrigerant flow, inducing refrigerant flow mal-distribution, and raising the core inlet pressure and temperature. Accordingly, there remains a need for a heat pump heat exchanger that has an improved outlet collector to provide for a reduced outlet pressure drop and more uniform refrigerant distribution throughout the core.
The invention relates to a heat pump heat exchanger having a first manifold, a second manifold spaced from the first manifold, a plurality of refrigerant tubes hydraulically connecting the manifolds, and a distribution tube disposed in the first manifold. The distribution tube includes an inlet end, a distal end opposite the inlet end, a plurality of orifices between the inlet end and the distal end. The distribution tube also includes a terminal aperture immediately adjacent the distal end, wherein the terminal aperture includes an open aperture area greater than any one of the open orifice area. The open aperture area is large enough to provide a uniform refrigerant collection with acceptable minimal pressure drop in evaporative mode, but small enough to prevent vapor overflow to an area of the manifold adjacent to the distal end in condenser mode. The length of the distribution tube is less than ¾ the length of the first manifold.
It is preferable that the ratio of the open area of the terminal aperture to the total open area of the other orifices is equal to the ratio of the manifold length minus tube length to the tube length as presented in the following equation:
[Areaterminal aperture/Total Areaorifices]=[[lengthmanifold−lengthtube]/[lengthtube]]
Where:
Areaterminal aperture=the open area of the terminal aperture;
Total Areaorifices=the sum of the open areas of the orifices;
lengthmanifold=the length of the manifold;
lengthtube=the length of the improved distribution tube.
The improved distribution tube design provides similar refrigerant distribution as that of the full length distribution tube when functioning as an outlet collector, but improves evaporator performance by as much as 15% by reducing the outlet manifold pressure drop. The improved distribution tube has minimal, if any adverse effect when the heat pump heat exchanger operates in condenser mode, in which the improved distribution tube functions as an inlet distributor.
In the drawings as hereinafter described, a preferred embodiment is depicted; however, various other modifications and alternative designs and construction can be made thereto without departing from the spirit and scope of the invention.
This invention will be further described with reference to the accompanying drawings in which:
Shown in
The first manifold 102 is shown above the second manifold 104 respect to the direction of gravity; therefore, the first manifold 102 is also known as the upper manifold 102 and the second manifold 104 is known as the lower manifold 104. In evaporator mode, a two-phase refrigerant flows from the lower manifold 104 to the upper manifold 102 absorbing heat from a stream of ambient air flow as the refrigerant expands into a low pressure vapor refrigerant. In condenser mode, a high pressure vapor refrigerant flows from the upper manifold 102 to the lower manifold 104 while dispersing heat to the stream of ambient air flow as the vapor refrigerant condenses to a high pressure liquid refrigerant. In other words, the upper manifold 102 is the outlet manifold 102 when the heat pump heat exchanger 100 is in evaporator mode and an inlet manifold when the heat pump heat exchanger 100 is in condenser mode.
Due to higher heating and cooling load demands, residential and commercial heat exchangers require manifolds 102, 104 that are typically 3 to 8 times the length of a conventional automotive manifold. This dramatically increases the length of the manifolds 102, 104. Distribution tubes are known to be used in either or both of the manifolds 102, 104 in order to improve refrigerant distribution across the refrigerant tubes 106. A conventional distribution tube typically includes a cylindrical hollow tube having a plurality of orifices spaced along its length and extends substantially the full length of the manifolds 102, 104. Distribution tubes used in the inlet manifold are known as inlet distributors and distribution tubes used in the outlet manifolds are known as outlet collectors.
Inlet distributors are configured to deliver partially expanded a two phase refrigerant uniformly along the length of the inlet manifold. In practice their capacity is limited by the pressure drop created by the cross sectional area of the inlet distributor. Theoretically, the overall pressure drop generated by an inlet distributor does not affect evaporator performance, but in practice the pressure drop along the inlet manifold constrains performance by limiting refrigerant flow down the inlet manifold. Likewise outlet collectors are configured to collect expanded gaseous refrigerant uniformly along the length of the outlet manifold. Since the expanded refrigerant is primarily vapor at this point, due to the increase in volume, the velocity and the resulting pressure drop can be much higher. Increased outlet pressure drop reduces performance by constraining refrigerant flow, thereby inducing refrigerant flow mal-distribution across the refrigerant tubes, and raising the heat exchanger inlet pressure and temperature.
A conventional heat pump heat exchanger includes full length distribution tubes, approximately the same length of the manifolds, with distinct holes, also known as orifices. As mentioned above, when in evaporative mode, the upper manifold functions as an outlet manifold and the associated distribution tube functions as an outlet collector. It was surprisingly discovered that the conventional full length distribution tube disposed in the upper manifold may be replaced with an improved distribution tube 200 that runs only a portion of the length, approximately one-third to three-fourth, of the upper manifold. The improved distribution tube design provides similar refrigerant distribution as that of the full length distribution tube when functioning as an outlet collector, but improves evaporator performance by as much as 15% by reducing the outlet manifold pressure drop. It was also surprisingly found that the improved distribution tube 200 has minimal, if any adverse effect when the heat pump heat exchanger 100 operates in condenser mode, in which the improved distribution tube 200 functions as an inlet distributor.
Shown in
The size of the open area of the terminal aperture 220 is large enough to provide a uniform refrigerant collection throughout the manifold with acceptable minimal pressure drop in evaporative mode, but small enough to prevent vapor overflow to the area of the manifold adjacent the distribution tube 200 distal end 216 in condenser mode.
It is preferable that the ratio of the open area of the terminal aperture 220 to the total open area of the other orifices 206 is equal to the ratio of the manifold length minus tube length to the tube length as presented in the following equation:
[Areaterminal aperture/Total Areaorifices]=[[lengthmanifold−lengthtube]/[lengthtube]]
Where:
Areaterminal aperture=the open area of the terminal aperture 220;
Total Areaorifices=the sum of the open areas of the orifices 206;
lengthmanifold=the length of the manifold 102;
lengthtube=the length of the improved distribution tube 200.
Shown in
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. 61/727,173 for a HEAT EXCHANGER HAVING A LOW PRESSURE DROP OUTLET COLLECTOR, filed on Nov. 16, 2012, which is hereby incorporated by reference in its entirety.
| Number | Name | Date | Kind |
|---|---|---|---|
| 7331195 | Bae et al. | Feb 2008 | B2 |
| 8561680 | Jiang et al. | Oct 2013 | B2 |
| 20020046827 | Saito et al. | Apr 2002 | A1 |
| 20030010483 | Ikezaki et al. | Jan 2003 | A1 |
| 20070039724 | Trumbower et al. | Feb 2007 | A1 |
| 20080093051 | Rios et al. | Apr 2008 | A1 |
| 20110017438 | Huazhao et al. | Jan 2011 | A1 |
| 20110127023 | Taras et al. | Jun 2011 | A1 |
| 20110203308 | Chiang et al. | Aug 2011 | A1 |
| 20120292004 | Chen et al. | Nov 2012 | A1 |
| 20130192808 | Liu | Aug 2013 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20150122470 A1 | May 2015 | US |
| Number | Date | Country | |
|---|---|---|---|
| 61727173 | Nov 2012 | US |
