Patent Publication Number: US-2007107453-A1

Title: Heat exchanger with embedded heater

Description:
TECHNICAL FIELD  
      The present invention relates generally to heat exchangers and in particular to heat exchangers having both heating and cooling functions.  
     BACKGROUND  
      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. In some applications the heat exchangers are designed for both heat exchange and cold exchange. For heat exchange, a heater is typically submerged in an associated fluid which is then activated to heat the fluid as it flows over the heater. The heated fluid is then pumped through the heat exchanger (i.e. through the containers thermally coupled to each other to transfer the heat from the heated fluid to the other fluid). This type of arrangement, however, presents a problem with the separation of control of the energy entering and exiting the system. In particular, this type of arrangement, can cause oscillation at set points and unreliable operation during ramps (i.e. the transition period it takes from going from an initial temperature to a desired temperature). In addition, in very cold dwells or rapid ramps, the cold exchanger can actually freeze the working fluid in the exchanger, stopping all flow. If this happens, no matter how much heat the heating system adds, the cold exchanger will not thaw since there is no flow of the fluids. This forces the system to stop operation until the cold exchanger thaws out on its own. This can take days in large systems causing loss of production and time. Another disadvantage to this type of system is the bulkiness of the total system (i.e. the separate heater and heat exchanger takes up a lot of space). Where space is limited, this type of heat exchanger system is not a viable option.  
      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 a heat exchange system that is efficient, not as susceptible to the freezing of the working fluid and is relatively small in size.  
     SUMMARY OF INVENTION  
      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 exchange system is provided. The heat exchange system includes a first container, a second container and at least one heater. The first container is adapted to hold a first fluid. The second container is adapted to hold a second fluid. Moreover, the second container is thermally coupled to the first container such that thermal energy transfer between the first and second container occurs. The at least one heater is embedded with the first and second container.  
      In another embodiment, a method of manufacturing a heat exchanger is provided. The method comprises forming a first thermal container adapted to contain a first liquid. Forming a second thermal container adapted to contain a second liquid. The second thermal container is thermally coupled to the first thermal container. Finally, embedding at least one heater with the first and second thermal containers.  
      In yet another embodiment, a method of operating a heat exchange is provided. The method comprises generating a flow of a first fluid in a first container. Generating a flow of a second fluid in a second container, wherein the second container is thermally coupled to the first container and adjusting the thermal energy in the first and second fluids with at least one heater that is integrated with the first and second container.  
      In still another embodiment, a heat exchange system comprises a first means for containing a first fluid and a second means for containing a second fluid. The first and second means being in thermal contact with each other. The heat exchange system also includes a means for heating the first and second fluids with a heater embedded with the first and second means for containing the first and second fluid.  
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      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:  
       FIG. 1  is a cross-sectional side view of a heat exchanger system of one embodiment of the present invention;  
       FIG. 2  is a side view of a heat exchanger system of another embodiment of the present invention;  
       FIG. 3  is an illustration of a heat exchanger system of one embodiment of the present invention;  
       FIG. 4  is an illustration of a heat exchanger system of  FIG. 3  including a layer of thermally conductive material. 
    
    
      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.  
     DETAILED DESCRIPTION  
      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 a heat exchanger that has a heater embedded therein. By embedding the heater in the heat exchanger, greater temperature control of the heat exchanger is achieved since the thermal capacitance stored in the cold exchanger is driven away by one or heaters embedded in the heat exchanger rather then simply being transferred to the working fluid. Moreover, a controller of the heat exchanger of embodiments of the present invention does not have to try and compensate for residual cooling potential left in the cold heat exchanger after it is no longer needed. In addition, in embodiments of the present invention, you do not have to wait for the working fluid to pass through the entire system and return before heating the cold exchanger, thus reducing feedback time. This helps to minimize overshoot while ramping to set point as well as oscillation at set point. Embodiments of the present invention also help to prevent the cold heat exchanger from freezing during cold dwells and rapid ramps. Moreover, if the exchanger does freeze and the flow of working fluid is stopped, the heater or heaters can rapidly thaw the exchanger and restore the fluid flow. Finally, embodiments of the present invention provide a heat exchange system that is relatively small in size.  
      Referring to  FIG. 1 , a cross-sectional view of a heat exchange system  100  of one embodiment of the present invention is illustrated. As illustrated, the heat exchange system includes a first thermally conductive container  102  adapted to hold a first fluid  106  (gas or liquid) and a second thermally conductive container  104  to hold a second fluid (gas or liquid) ( 108 ). In this example of the embodiment of the present invention, the first container  102  is in the form of an annulus that surrounds the second container  104  which is in the form of a pipe. Fluid  106  exchanges thermal energy with fluid  108  in performing the heat exchange function.  
       FIG. 1 , also illustrates heaters  110 - 1  through  110 -N which are embedded in the heat exchange system  100 . In one embodiment the heaters  110 - 1  through  110 -N are electrical heaters. Also illustrated in  FIG. 1  is controller  112  that is designed to control the electric heaters  110 - 1  through  110 -N. Under control of the controller  112 , the thermal capacitance stored in the cold exchanger is selectively driven away by the heaters  110 - 1  through  110 -N embedded in the heat exchanger rather then simply being transferred to the working fluid. The present invention is not limited to the type of heat exchanger  100  illustrated in  FIG. 1  since other types of heat exchange systems would benefit from having one or more heaters embedded in the system. Moreover, embodiments of the present invention use different types of heaters which include but are not limited to solid plate heaters, rope heaters, wire heaters and immersion heaters and the like. Accordingly, the present invention is not limited to a specific type of heater.  
      An example of a different type of heat exchange system  200  incorporating an embodiment of the present invention is illustrated in  FIG. 2 . As illustrated, the heat exchange system  200  of  FIG. 2  includes a first and second container  202  and  204  respectively. The first and second containers  202  and  204  in this embodiment are tubes that are formed into coils. The tubes are made from a material that has relative high thermal conductivity such as copper. The coils of the first and second containers  202  and  204  are positioned next to each other so that thermal energy can be transferred between them. Also positioned next to the coils of the first and second containers  202  and  204  is a heater  206 . In particular, in this embodiment, the heater  206  is a wire (or cable) heater that is wrapped around the coils of the first and second containers  202  and  204 .  
      The embodiment of  FIG. 2  also includes a thermally conductive material  208  that encases the coils of the first and second container  202  and  204  as well as the heater  206  wrapped around the coils of the first and second containers  202  and  204 . The thermally conductive material  208  enhances thermal conduction between the fluids in the coils of the first and second containers and the heater  206 . This embodiment further includes a layer of insulation  210  that encases the thermally conductive material  208 . The layer of insulation  210  provides further efficiency to the heat exchanger system  200  of  FIG. 2 , by inhibiting unwanted thermal energy exchange between the heat exchange system  200  and the environment surrounding the system  200 .  
      Referring to  FIG. 3 , an illustration of a heat exchange system  300  similar to the heat exchange system of  FIG. 2  of one embodiment of the present invention is provided. This heat exchange system  300  also includes a first and second container  302  and  304  respectively. The first and second container  302  and  304  are tubes that are formed into coils that are positioned next to each other to achieve thermal transfer. Embedded in the coils is an electric wire heater  306 . The connections to the electric wire heater are indicated at  308  and  310 .  FIG. 4  illustrates the heat exchange system  300  of  FIG. 3  including conductive material  408  embedding the coils of the first and second containers  302  and  304  and the embedded wire heater  306 . In one embodiment, the conductive material is made from conductive clay that hardens after it is placed around the coils of the first and second containers  302  and  304  and the embedded wire heater  306 .  
      A flow diagram  500  illustrating the operation of a heat exchange system of one embodiment of the present invention is illustrated in  FIG. 5 . As illustrated, the operation begins by generating a flow of first and second fluids through a respective first and second containers ( 502  and  504 ). In embodiments of the present invention the thermal energy in the first and second fluids is adjusted using an embedded heater ( 506 ). As discussed above, the embedded heater provides greater temperature control of the heat exchanger since the thermal capacitance stored in the cold exchanger is driven away by the rather then simply being transferred to the working fluid. As a result, you do not have to wait for the working fluid to pass through the entire system and return before heating the cold exchanger, thus reducing feedback time. This helps to minimize overshoot while ramping to set point as well as oscillation at set point. Moreover, the adjusting of the temperature at ( 506 ) also helps to prevent the cold heat exchanger from freezing during cold dwells and rapid ramps. In addition, even if the exchanger does freeze and the flow of working fluid is stopped, the adjustment of the temperature at ( 506 ) can rapidly thaw the exchanger and restore the fluid flow.  
      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.