The present application is related to a pin fin heat exchanger with pins having an airfoil profile.
Heat exchangers capable of drawing heat from one place and dissipating it in another place are well known in the art and are used in numerous applications where efficiently removing heat is desirable. One type of heat exchanger used in fluid cooling systems dissipates heat from two parallel fluid passages into a cooling fluid passage between the passages. A cooling fluid (such as air) is then passed through the cooling fluid passage. Heat from the parallel fluid passages is drawn into the cooling fluid passage and is expelled at the opposite end of the heat exchanger with the cooling fluid. Heat exchangers of this type are often used in vehicle applications such as aircraft engines or car engines.
Devices constructed according to this principle transfer heat from the surface area of the parallel passages into the fluid flowing through the cooling fluid passage. In order to increase the surface area which is capable of dissipating heat, some heat exchangers have added pins extending from the walls of the parallel fluid passages into the air gap. The pins are thermally conductive and thus heat can be conducted from the passages into the pins and dissipated into the cooling fluid. The pins can be held in place using crossed ligaments. A device according to the above described design is referred to as a pin fin heat exchanger. The ligaments also provide more surface area which the fluid being forced through the cooling fluid passage is exposed to, and thereby allow a greater dissipation of heat. Some designs in the art utilize pins where each pin is connected to both of the parallel fluid passages resulting in a post running perpendicular to the parallel fluid passages through the gap. Current heat exchangers using pins have a symmetrical pin profile such as a circular or diamond profile.
Disclosed is a heat exchanger having pins connecting extending from a wall of a fluid passage into a cooling fluid passage. The pins conduct heat from the fluid passage into a cooling fluid passage adjacent to the wall. A cooling fluid flows through the gap and heat is dissipated from the pins and the wall into the fluid. The pins have an airfoil profile.
These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.
A simplified heat exchange system according to the present application is illustrated in
In order to increase the surface area exposed to the cooling fluid in the cooling fluid passage 110, and thereby increase the heat transfer potential of the heat exchanger, thermally conductive pins 112 connect the facing surfaces 106, 108 of the fluid passages 102, 104. The pins 112 conduct heat from the facing surfaces 106, 108 into the cooling fluid passage 110, thereby exposing more surface area to the cooling fluid flowing through the cooling fluid passage 110. Since the amount of heat dissipated in the heat exchanger is proportional to the surface area exposed to the cooling fluid, and the pins generate more exposed surface area, the efficiency of the heat exchanger is increased.
Previous pin fin heat exchanger designs used a circular, diamond, or other symmetrical shape for the pin 112 profile. In previous designs, when a cooling fluid flowing through the cooling fluid passage 110 in one direction hits the side of a symmetrical pin, the cooling fluid is naturally forced around the pin. It is well known in the art that the flow path can be either attached to surface, whereby the flow path near the wall is moving parallel to the wall and provides effective heat transfer, or separated from the surface, whereby the flow path is not necessarily parallel to the wall and does not provides effective heat transfer. In the process of flowing around the pin, the cooling fluid flow path becomes separated from the surface of the pin, resulting in the cooling fluid flow remaining attached to as little as half of the pin's surface area. Consequently, only the portion of the surface area of the pin contacting the flow path can provide heat dissipation and the remainder of the pin's surface area is wasted.
The airfoil pin 112 profile in
An additional advantage realized by the placement of the ligaments 306 in the cooling fluid passage 110 arises from the natural interference with the cooling fluid flow caused by the ligaments 306. When the cooling fluid flow contacts the ligaments 306 a wake zone is created behind the ligament 306. The wake zone causes turbulence in the cooling fluid which mixes the cooling fluid which was directly in the cooling fluid flow path with cooling fluid that was not directly in the cooling fluid flow path.
Mixing the cooling fluid in the cooling fluid flow path with the cooling fluid not directly in the cooling fluid flow path provides a beneficial dispersal of the heated cooling fluid from the direct flow path into the unheated cooling fluid not directly in the cooling fluid flow path. The mixing effect thereby increases the efficiency of the heat exchanger as it allows the cooling fluid directly in the fluid flow path to have a reduced temperature farther into the cooling fluid passage 110 than previous designs.
An example construction for the array of pins 112 and ligaments 306 is disclosed in
Once each sheet 402, 404, 406 has been etched to the proper shape and thickness, the sheets 402, 404, 406 are stacked on top of each other (illustrated in
In addition to providing more surface area through which heat can be dissipated, including additional ligaments 306 creates a restriction in the flow passage because the ligaments 306 block a portion of the flow. The restriction decreases the space through which the fluid can flow, thus causing flow acceleration and a decrease in flow pressure through the cooling fluid passage 110. By design, this decrease occurs in the deceleration regions 220 and 222, thereby this decrease in flow pressure results in less flow separation. A design taking advantage of the lower flow separation could be used in an application where the fluid flow pressure drop is not a significant design constraint.
Another example embodiment, illustrated in
Designs utilizing the ligament 306 layout of
Although example embodiments of this invention have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the true scope and content of this invention.
Number | Name | Date | Kind |
---|---|---|---|
1929365 | Mautsch | Oct 1933 | A |
1949041 | De Lagabbe | Feb 1934 | A |
1958364 | Govers | May 1934 | A |
2678808 | Gier, Jr. | May 1954 | A |
3741285 | Kuethe | Jun 1973 | A |
4821389 | Nelson | Apr 1989 | A |
4886018 | Ferroli | Dec 1989 | A |
4993487 | Niggemann | Feb 1991 | A |
5154679 | Fuller et al. | Oct 1992 | A |
5193611 | Hesselgreaves | Mar 1993 | A |
5512250 | Betta et al. | Apr 1996 | A |
5832993 | Ohata et al. | Nov 1998 | A |
5884691 | Batchelder | Mar 1999 | A |
6167952 | Downing | Jan 2001 | B1 |
6520252 | Bizzarro | Feb 2003 | B1 |
7111672 | Symonds | Sep 2006 | B2 |
7278474 | Valenzuela et al. | Oct 2007 | B2 |
7302998 | Valenzuela | Dec 2007 | B2 |
7353864 | Zaffetti et al. | Apr 2008 | B2 |
20040194936 | Torii | Oct 2004 | A1 |
20080066888 | Tong et al. | Mar 2008 | A1 |
20090145581 | Hoffman et al. | Jun 2009 | A1 |
20090151920 | Polcyn | Jun 2009 | A1 |
20090314474 | Kimbara et al. | Dec 2009 | A1 |
Number | Date | Country |
---|---|---|
2122738 | Jan 1984 | GB |
55-122077 | Aug 1980 | JP |
61-74784 | May 1986 | JP |
1-217193 | Aug 1989 | JP |
9737187 | Oct 1997 | WO |
2005033607 | Apr 2005 | WO |
Entry |
---|
European Search Report for European Patent Application No. 10250006.3 dated Nov. 28, 2013. |
Number | Date | Country | |
---|---|---|---|
20100170667 A1 | Jul 2010 | US |