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[0001] This patent application claims benefit of priority to provisional patent application No. 60/339,765, titled “AN IMPROVED HEAT EXCHANGER TO FACILITATE ACCURATE TEMPERATURE CONTROL”, filed Nov. 1, 2001.
[0002] The invention relates to the field of heat exchangers. More specifically, the invention relates to an improved convective heat exchanger that facilitates precise temperature control.
[0003] Recently, inspection methods involving thermal signatures of materials are being utilized, in particular, infrared (IR) detection imaging. A turbine component inspection method utilizing IR imaging involves applying a thermal differential to the component. An example of a turbine component may be a thin or flat object that may be referred to as vanes or blades utilized to cause fluid flow or direct fluid.
[0004] For example, often times, applying a thermal differential involves delivering a thermal stimulus, such as a gas, at a high temperature thermal stimulus to the component, and then, immediately following the high temperature inspection medium, delivering another thermal stimulus, such as the gas, at a cold temperature (i.e., cold, relative to the high temperature thermal stimulus) to the component.
[0005] Often times, in inspecting a turbine component, hot and cold gases are used as thermal stimuli. An example of an IR inspection apparatus may be found in copending U.S. patent application Ser. No. ______, titled “TURBINE COMPONENT INSPECTION SYSTEM”, contemporaneously filed, and having at least partial common inventorship with present application. Furthermore, in order to increase quality of results from such an inspection apparatus, inspection conditions such as, but not limited to, temperature, pressure, humidity, etc. may be required to be identical for various blade types.
[0006] Often times, in order to heat the gas, heat exchangers may be utilized. Heat exchangers are designed to transfer heat between fluids at different temperatures. Examples of common heat exchangers may be a vessel in which hot and cold streams are mixed, two streams at different temperatures separated by a wall or tubes, where conductive heat transfer occurs, and so forth. Furthermore, control of the different temperature streams may increase the cost and difficulty associated with manufacturing these types of heat exchangers.
[0007] Other types of heat exchangers may involve convective heat transfer, where a gas is allowed to flow through an area of high temperatures to heat the gas, such as a common hair dryer. In a common hairdryer, air at ambient temperature is forced through heating elements. As the air flows past the heating elements, the heating elements are hot enough to heat the air to very hot temperatures within a relatively short distance. However, the precise temperature at the outlet of the hairdryer is difficult to predict because typical prior art heat exchangers are designed to maximize the amount of hear transfer, i.e. minimizing the amount of time required to bring a fluid to a desired temperature. Thus, slight variations in length air travels past heating elements and temperature and humidity at an inlet of a heat exchanger having an intrinsic steep gradient of heat exchange, substantially affects the temperature at the outlet.
[0008] Another type of heat exchanger that involves convective heat transfer may be where the gas is allowed to travel through a heated metal pipe. However, here again, for the same reasons discussed earlier, a small variation of the length of the heated metal pipe substantially affects the temperatures of the gas at the outlet of the pipe.
[0009]
[0010] Thus, an improved heat exchanger providing a more precise control over the temperature of an exiting fluid, while inexpensive and simple to manufacture, is desired.
[0011] The invention is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings, in which the like references indicate similar elements and in which:
[0012]
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[0018]
[0019] In the following description, various aspects of the invention will be described. However, it will be apparent to those skilled in the art that the invention may be practiced with only some or all described aspects. For purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the invention. However, it will also be apparent to one skilled in the art that the invention may be practiced without the specific details. In other instances, well-known features are omitted or simplified in order not to obscure the invention.
[0020] Various operations will be described as multiple discrete steps in turn, in a manner that is most helpful in understanding the invention. However, the order of description should not be construed as to imply that these operations are necessarily order dependent. In particular, these operations need not be performed in the order of presentation.
[0021] In various embodiments of the present invention, an improved convective heat exchanger that facilitates precise temperature control is disclosed. This and other advantages will be evident from the disclosure.
[0022] In designing a heat exchanger, if a gas is allowed to flow through a very long heated metal pipe, the temperature of the gas will eventually reach the same temperature of the heated metal pipe. If the temperature of the long metal pipe is precisely known, the temperature is held constant over the entire length of the long metal pipe, and the behavior of the flow (i.e., turbulent, laminar, or transitional), the temperature of the gas at the outlet may also be precisely known. However, the length required to heat a gas convectively might be long enough to make its use difficult, costly, or difficult to manufacture.
[0023] Further, in order to have the gas flow through a very long path (i.e., very long effective length of a metal pipe) while reducing the overall length of the metal pipe, the very long metal pipe may be coiled. A coiled metal pipe provides a long path for the gas flow within a relatively short overall length. But, heating a coiled metal pipe is difficult because all of the surface areas of the coiled metal pipe may dissipate heat into its surroundings, and proper connections between parts may also be difficult to achieve.
[0024]
[0025] Heat may be provided to the heat exchanger
[0026] Utilizing the convective heat transfer principles of gas flowing through a heated tube, the predetermined length
[0027]
[0028] As will be described in further detail below, the space between the grooves
[0029] The material of the metal rod may be any type of thermally highly efficient conductive material that also provides enough mass to reduce the thermal dissipation effects, such as significant temperature drops. An example of the thermally highly conductive material that can efficiently yield the desired mass may be a material, such as, but not limited to, pure copper. Additionally, the metal rod
[0030]
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[0032] It should be appreciated by one skilled in the art that the heat exchanger
[0033] Additionally, to ensure proper flow of the gas through the grooves
[0034]
[0035] As a result, precise control of temperatures of the gas flowing through a heat exchanger while increasing a
[0036]
[0037] Shown in
[0038] In
[0039] The material of the disks
[0040] While the present invention has been described with regard to a rectangular heat exchanger, it should be appreciated by those skilled in the art that present invention may be practiced to with different shaped heat exchangers, such as, but not limited to, a heat exchanger in the shape of a cylinder. Additionally, the present invention has been described with gas flowing through the heat exchanger; however, it should be appreciated that the heat exchanger may be modified to accommodate any type of flowing matter, such as, but not limited to, liquids and be within the spirit and scope of the present invention. Different embodiments and adaptations besides those shown and described herein, as well as many variations, modifications and equivalent arrangements will now be apparent or will be reasonably suggested by the foregoing specification and drawings, without departing from the substance or spirit and scope of the invention. While the present invention has been described herein in detail in addition to its preferred embodiment, it is to be understood that this disclosure is only illustrative and exemplary of the present invention and is made merely for purposes of providing a full an enabling disclosure of the invention.
[0041] Thus, an improved convective heat exchanger that facilitates precise temperature control has been disclosed