Abstract:
A cooling blanket to provide cooling capability may include a first sheet, a second sheet opposed to the first sheet, a cooling tube positioned between the first sheet and the second sheet to provide a path for cooling fluid and a acoustic refrigerator to cool the cooling fluid.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a blanket and more particularly to a cooling blanket that may include cooling capabilities. 
       BACKGROUND 
       [0002]    Blankets have been used extensively to provide heat and warmth for individuals particularly to be used on beds. However, there is a need for a device to provide cooling capability especially in warmer climates during the summer time. Air-conditioning has been used to provide cooling capabilities for an entire room or structure, but there is a large amount of energy/electricity that is needed to provide the necessary air-conditioning. 
         [0003]    There is a need to provide cooling capabilities at a fraction of the cost of cooling an entire room or building. 
         [0004]    Thermoacoustic engines (sometimes called “TA engines”) are thermoacoustic devices which use high-amplitude sound waves to pump heat from one place to another, or conversely use a heat difference to induce high-amplitude sound waves. In general, thermoacoustic engines can be divided into standing wave and travelling wave devices. These two types of thermoacoustics devices can again be divided into two thermodynamic classes, a prime mover (or simply heat engine), and a heat pump. The prime mover creates work using heat, whereas a heat pump creates or moves heat using work. Compared to vapor refrigerators, thermoacoustic refrigerators have no ozone-depleting or toxic coolant and few or no moving parts therefore require no dynamic sealing or lubrication 
       History 
       [0005]    The history of thermoacoustic hot air engines started about 1887, when Lord Rayleigh discussed the possibility of pumping heat with sound. Little further research occurred until Rott&#39;s work in 1969. 
         [0006]    A very simple thermoacoustic hot air engine is the Rijke tube that converts heat into acoustic energy. This device however uses natural convection. 
       Research in Thermoacoustics 
       [0007]    Modern research and development of thermoacoustic systems is largely based upon the work of Rott (1980) and later Steven Garrett, and Greg Swift (1988), in which linear thermoacoustic models were developed to form a basic quantitative understanding, and numeric models for computation. Commercial interest has resulted in niche applications such as small to medium scale cryogenic applications. 
       Current Research 
       [0008]    Orest Symko at University of Utah began a research project in 2005 called Thermal Acoustic Piezo Energy Conversion (TAPEC). 
         [0009]    Score Ltd. was awarded £2M in March 2007 to research a cooking stove that will also deliver electricity and cooling using the Thermo-acoustic effect for use in developing countries. 
         [0010]    Cool Sound Industries, Inc. is developing an air-conditioning system that uses thermoacoustic technology, with a focus on HVAC applications. The system is claimed to have high efficiency and low costs compared to competing refrigeration technologies, and uses no HFC, no HCFC, and no mechanical compressor. 
         [0011]    Q-Drive, Inc. is also engaged in developing thermoacoustic devices for refrigeration, with a focus on cryogenic applications. 
       SUMMARY 
       [0012]    A cooling blanket to provide cooling capability may include a first sheet, a second sheet opposed to the first sheet, a cooling tube positioned between the first sheet and the second sheet to provide a path for cooling fluid and a acoustic refrigerator to cool the cooling fluid. 
         [0013]    The acoustic refrigerator may include a cold heat exchanger. 
         [0014]    The acoustic refrigerator may include a hot heat exchanger. 
         [0015]    The acoustic refrigerator may include a loudspeaker. 
         [0016]    The acoustic refrigerator may include a stack of plates. 
         [0017]    The cooling tube may include a pump. 
         [0018]    The cooling tube may include a heat exchanger. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The invention may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which, like reference numerals identify like elements, and in which: 
           [0020]      FIG. 1  illustrates a thermoacoustic refrigerator of the present invention; 
           [0021]      FIG. 2  illustrates a detail of the thermoacoustic refrigerator of the present invention; 
           [0022]      FIG. 3  illustrates a diagram of temperature and pressure of the thermoacoustic refrigerator of the present invention 
           [0023]      FIG. 4  illustrates a blanket with cooling capabilities of the present invention; 
           [0024]      FIG. 5  illustrates a portion of the blanket with cooling capabilities of the present invention; 
           [0025]      FIG. 6  illustrates a cross-section of the cooling blanket of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0026]    A thermoacoustic device basically consists of heat exchangers, a resonator, and a stack (on standing wave devices) or regenerator (on travelling wave devices). Depending on the type of engine a driver or loudspeaker might be used as well to generate sound waves. 
         [0027]    Consider a tube closed at both ends. Interference can occur between two waves traveling in opposite directions at certain frequencies. The interference causes resonance creating a standing wave. Resonance only occurs at certain frequencies called resonance frequencies, and these are mainly determined by the length of the resonator. 
         [0028]    The stack is a part consisting of small parallel channels. When the stack is placed at a certain location in the resonator, while having a standing wave in the resonator, a temperature difference can be measured across the stack. By placing heat exchangers at each side of the stack, heat can be moved. The opposite is possible as well, by creating a temperature difference across the stack, a sound wave can be induced. The first example is a simple heat pump, while the second is a prime mover. 
       Heat Pumping 
       [0029]    To be able to create or move heat, work must be done, and the acoustic power provides this work. When a stack is placed inside a resonator a pressure drop occurs. Interference between the incoming and reflected wave is now imperfect since there is a difference in amplitude causing the standing wave to travel little, giving the wave acoustic power. 
         [0030]    In the acoustic wave, parcels of gas adiabatically compress and expand. Pressure and temperature change simultaneously; when pressure reaches a maximum or minimum, so does the temperature. Heat pumping along a stack in a standing wave device can now be described using the Brayton cycle. 
         [0031]    Below is the counter-clockwise Brayton cycle consisting of four processes for a refrigerator when a parcel of gas is followed between two plates of a stack.
       1. Adiabatic compression of the gas. When a parcel of gas is displaced from its rightmost position to its leftmost position, the parcel is adiabatic compressed and thus the temperature increases. At the leftmost position the parcel now has a higher temperature than the warm plate.   2. Isobaric heat transfer. The parcel&#39;s temperature is higher than that of the plate causing it to transfer heat to the plate at constant pressure losing temperature.   3. Adiabatic expansion of the gas. The gas is displaced back from the leftmost position to the rightmost position and due to adiabatic expansion the gas is cooled to a temperature lower than that of the cold plate.   4. Isobaric heat transfer. The parcel&#39;s temperature is now lower than that of the plate causing heat to be transferred from the cold plate to the gas at a constant pressure, increasing the parcel&#39;s temperature back to its original value.       
 
         [0036]    Travelling wave devices can be described using the Stirling cycle. 
       Temperature Gradient 
       [0037]    An engine and heat pump both typically use a stack and heat exchangers. The boundary between a prime mover and heat pump is given by the temperature gradient operator, which is the mean temperature gradient divided by the critical temperature gradient. 
         [0000]    
       
         
           
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         [0038]    The mean temperature gradient is the temperature difference across the stack divided by the length of the stack. 
         [0000]    
       
         
           
             
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         [0039]    The critical temperature gradient is a value depending on certain characteristics of the device like frequency, cross-sectional area and gas properties. 
         [0040]    If the temperature gradient operator exceeds one, the mean temperature gradient is larger than the critical temperature gradient and the stack operates as a prime mover. If the temperature gradient operator is less than one, the mean temperature gradient is smaller than the critical gradient and the stack operates as a heat pump. 
       Theoretical Efficiency 
       [0041]    In thermodynamics the highest achievable efficiency is the Carnot efficiency. The efficiency of thermoacoustic engines can be compared to Carnot efficiency using the temperature gradient operator. 
         [0042]    The efficiency of a thermoacoustic engine is given by 
         [0000]    
       
         
           
             η 
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                 η 
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         [0043]    The coefficient of performance of a thermoacoustic heat pump is given by 
         [0000]    
       
      
       COP=I·COP 
       c  
      
     
       Derivations 
       [0044]    Using the Navier-Stokes equations for fluids, Rott was able to derive equations specific for thermoacoustics. Swift continued with these equations, deriving expressions for the acoustic power in thermoacoustic devices. 
       Efficiency in Practice 
       [0045]    The most efficient thermoacoustic devices built to date have an efficiency approaching 40% of the Carnot limit, or about 20% to 30% overall (depending on the heat engine temperatures). 
         [0046]    Higher hot-end temperatures may be possible with thermoacoustic devices because there are no moving parts, thus allowing the Carnot efficiency to be higher. This may partially offset their lower efficiency, compared to conventional heat engines, as a percentage of Carnot. 
         [0047]    The ideal Stirling cycle, approximated by travelling wave devices, is inherently more efficient than the ideal Brayton cycle, approximated by standing wave devices. However, the narrower pores required to give good thermal contact in a travelling wave regenerator, as compared to a standing wave stack which requires deliberately imperfect thermal contact, also gives rise to greater frictional losses, reducing the efficiency of a practical engine. The toroidal geometry often used in travelling wave devices, but not required for standing wave devices, can also give rise to losses due to Gedeon streaming around the loop. 
         [0048]      FIG. 1  illustrates a thermal acoustic refrigerator  101  which may be electronically driven by a radically modified loudspeaker  103  to maintain a standing sound wave  105  which may be input to the loudspeaker  103  in an inert gas in a resonator  107 . The sound wave  105  interacts with an array of parallel solid plates  109  referred to collectively as a stack  111 . A cold heat exchanger  113  may be positioned at one end of the stack  111 , and a hot heat exchanger  115  may be positioned at an opposing end of the stack  111 . The resulting refrigeration can be understood by examining a typical small element of gas  117  between the plates  119  of the stack  111 . As the gas  117  oscillates back and forth because of the effect from the standing sound wave, the element of gas  117  changes in temperature. Much of the temperature change comes from compression and expansion of the gas  117  by the sound pressure (as always in a sound wave), and the rest of the temperature change is a consequence of heat transfer between the gas  117  and the stack  111 . In the example shown, the length of the resonator may be one fourth the wavelength of the sound produced by the speaker  103 , so all the elements of gas  117  are compressed and heated as the gas  117  move to the right, and the elements of the gas  117  are expanded and cooled as they moved to the left. Thus each element of gas  117  goes through a thermodynamic cycle as shown in  FIG. 3  in which the element of gas  117  is compressed and is heated; the element of gas  117  rejects heat at the right end of its range of oscillation; the element of gas  117  is depressurized and cooled, and absorbs heat at the left end. Consequently, each element of gas moves a little heat from left to right, from cold to hot, during each cycle of the sound wave. The combination of the cycles of all the elements of gas  117  transports heat from the cold heat exchanger to the hot heat exchanger much as a bucket brigade transports water. The spacing between the plates  109  in the stack provides proper function: if the spacing is too narrow, the good thermal contact between the gas  117  and the stack  111  keeps the gas at nearly the same temperature as the stack  111 , whereas if the spacing is too wide, much of the gas  117  is in a poor thermal contact with the stack  111  and does not transfer heat effectively to and from the stack  111 . 
         [0049]      FIG. 2  illustrates a detail of a first plate  109  of the stack  111  and a second plate  109  of the stack  111 , and illustrates the oscillation of the element of gas  117  between the cold heat exchanger  113  and the hot heat exchanger  115 . 
         [0050]      FIG. 4  illustrates the cooling blanket  100  of the present invention which may include a cooling tube  201  which may be filled with a cooling fluid such as anti-freeze to conduct the heat from the cooling blanket  100 . The cooling tube may be formed into an array  205 , and the cooling blanket  100  may include the thermal acoustic refrigerator  101  as illustrated in  FIG. 1 . The thermal acoustic refrigerator  101  may include an input tube  207  and an output tube  209  to input the fluid from the cooling tube  201  to the cold heat exchanger  113  and to output the fluid to the cooling tube  201  from the cold heat exchanger  113  respectively. 
         [0051]    The input tube  207  and the output tube  209  are connected to a heat exchanger  211  as shown in  FIG. 5  which may be positioned within the cooling tube  201  in order to cool the fluid to remove the heat from the cooling blanket  100  within the cooling tube  201 . 
         [0052]      FIG. 5  illustrates a connector  215  to connect the cooling tube  201  and may include a fluid pump  217  to circulate or pump the fluid to the cooling blanket  100  within the cooling tube  201  and may include an internal temperature sensor  219  to measure temperature. 
         [0053]      FIG. 4  additionally illustrates that a power cord  221  may be connected to the acoustic refrigerator  101  to supply power to the acoustic refrigerator  101  and additionally illustrates an external temperature sensor  223  to measure the external temperature to the acoustic refrigerator  101 . 
         [0054]      FIG. 6  illustrates a cross-section of the cooling blanket  100  of the present invention and illustrates the cooling tube  201  positioned between a first sheet  202  and a second sheet  203 . 
         [0055]    While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed.