Patent Application
20070107444
The present invention relates generally to heat exchangers.
Fluids are used in various industries for certain heating or cooling applications. For example, fluids (liquid or gas) are used in heat exchangers. A heat exchanger is a device used to transfer thermal energy from one fluid to another fluid. The two fluids are held in separate containers that are thermally coupled to each other so that the transfer of thermal energy occurs. The use of heat exchangers for liquid cooling is used in industry for a variety of tasks. A typical refrigerant (or cooling) fluid used in industry is Freon. In a heat exchange system, the Freon is driven by compressors through its container to cool a working fluid in the other thermally coupled container.
Freon systems, however, tend to be very complicated, expensive, large and prone to frequent breakdowns. Another type of heat exchange system uses liquid nitrogen (LN2) as a cooling fluid. LN2 heat exchangers (or cooling systems) have an advantage over the Freon systems. One of the major advantages is that they have fewer moving parts. LN2 systems, however, are difficult to design since the cold temperatures provided by the LN2 can cause the exchanger to fracture or fail. Moreover, the working fluid in an LN2 exchanger is also prone to freeze in the exchanger near the LN2 inlet. In addition, the LN2 can flood and remain in the exchanger even when the supply is turned off. This excess cooling energy causes the system to lose control and can take the product beyond its temperature limits.
For the reasons stated above and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for an efficient and effective LN2 heat exchange system that is not as susceptible to limitation of prior systems.
The above-mentioned problems of current systems are addressed by embodiments of the present invention and will be understood by reading and studying the following specification.
In one embodiment, a heat exchanger is provided. The heat exchanger includes a first tube and a second tube. The first tube has at least one coil and a first diameter. The second tube also has at least one coil and a second diameter. The at least one coil of the first tube is positioned next to the at least one coil of the second tube such that thermal energy is exchanged between the at least one first and the at least one second coil.
In another embodiment, a method of manufacturing a heat exchanger is provided. The method includes forming one or more coils in a first conductive tube. Forming one or more coils in a second conductive tube and coupling the one or more coils of the first conductive tube next to the one or more coils of the second conductive tube such that thermal energy is transferred between the first and second tubes.
In yet another embodiment, a method of operating a heat exchanger is provided. The method includes pumping a working fluid through a first tube in a loop fashion. The first tube has at least one coil. Providing a liquid nitrogen (LN2) supply to a first end of a second tube. The second tube also has least one coil that is thermally coupled to the at least one coil of the first tube. Exhausting out gas through a second end of the second tube and transferring thermal energy between the working fluid and the LN2.
In still another embodiment, a heat exchange system is proved. The heat exchange system includes a means to transfer thermal energy between working fluid in at least one coil of a thermally conductive tube and liquid nitrogen LN2 in at least one coil of a second thermally conductive tube.
The present invention can be more easily understood and further advantages and uses thereof more readily apparent, when considered in view of the description of the preferred embodiments and the following figures in which:
In accordance with common practice, the various described features are not drawn to scale but are drawn to emphasize specific features relevant to the present invention. Reference characters denote like elements throughout Figures and text.
In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the inventions may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical and electrical changes may be made without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined only by the claims and equivalents thereof.
Embodiments of the present invention provide an efficient LN2 heat exchanger system that is not prone to the problems of prior systems. In particular, embodiments of the present invention provide a tube on tube embedded heat exchanger that provides a large surface area for exchanging thermal energy while minimizing volume. The tubes are bent into coils. The round shape of the coils provides the largest surface area for the smallest volume, thus a minimum amount of LN2 collects in the exchanger while still allowing the maximum transfer of thermal energy between the working fluid and the LN2. In addition, because there are no welds or joints in embodiments of the present invention, the chance of the exchanger cracking or failing due to thermal gradients is minimized. Moreover, because of the full contact of the coils, little LN2 is wasted.
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In one embodiment, the tubes 102 and 104 are of equal length but unequal in diameter. The lengths of the tubes are coiled into one or more circles of the same diameter and placed next to each other. In this embodiment, the tube 104 having the smaller diameter is connected to the LN2 supply while the larger tube 102 is connected to the working fluid.
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Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement, which is calculated to achieve the same purpose, may be substituted for the specific embodiment shown. This application is intended to cover any adaptations or variations of the present invention. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.
