Patent Publication Number: US-2011075702-A1

Title: Thermal sensing equipment and thermal sensing process

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of application Ser. No. 11/877,113, filed Oct. 23, 2007, which is incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The application generally relates to liquid compositions for use in thermal sensing equipment. The application relates more specifically to fluids that can substitute toluene in thermal sensing equipment utilized for Heating, Ventilation, Air Conditioning and Refrigeration (HVAC&amp;R) systems. 
     Liquid toluene, which has a known coefficient of expansion, is a thermal fluid utilized to fill temperature sensing elements and temperature sensing equipment. Toluene has been considered a hazardous material by the U.S. Department of Transportation and has been classified by National Fire Protection Association (NFPA) within the NFPA fire diamond as having a Health Value of 2, Flammability Value of 4 and Reactivity Value of 1. This last classification includes an extremely hazardous flammability and a moderately hazardous health hazard requiring human protection through the use of a breathing apparatus. The use of fluids having such classifications are undesirable in temperature sensing equipment. 
     A temperature sensing element is a closed piece of metal tubing filled with a liquid. The tubing is configured with one of the ends of the element including a flexible diaphragm that exhibits contraction or expansion as a result of a corresponding volume change of the liquid that can be induced by a temperature change of the element. The original volume of the liquid contained in the element is known at a given temperature and the liquid has a known coefficient of thermal expansion. In other words, since the volume and coefficient of expansion of the liquid is known, the expansion and contraction of the liquid (and hence the diaphragm) can be determined as the temperature changes. The expansion and contraction follows the following formula: 
       Δ V=β×V   i   ×ΔT  
 
     Where ΔV corresponds to the volume change of the liquid in cubic inches (in 3 ), β represents the coefficient of thermal expansion of the fluid inverse degree Fahrenheit (1/° F.) V i  is the initial volume at the initial temperature in cubic inches (in 3 ) and ΔT is temperature change in degrees Fahrenheit (° F.). The lower value of β of a fluid, the greater temperature change required to produce a given diaphragm movement. Therefore, if the value of β for a given liquid is smaller than the value of β for toluene, a different and larger range of differential movement of the diaphragm for the same volume of liquid and the same diaphragm configuration of the element is expected for the given liquid as compared to toluene. Toluene has been used in various temperature sensing elements and temperature sensing equipment for at least 50 years. Existing thermal fluids known as being less hazardous than toluene using the NFPA classification, are typically synthetic, organic, low viscosity materials having a β smaller than toluene. Such differences in β of the fluids require a redesign of the thermal sensing equipment including an increased bulb size and/or larger differentials in the specification for the element if the other fluid is to be used. 
     Intended advantages of the disclosed systems and/or methods satisfy one or more of these needs or provide other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the claims, regardless of whether they accomplish one or more of the aforementioned needs. 
     SUMMARY 
     One embodiment relates to a thermal fluid having a fluid that includes a compound selected from the group consisting of compounds having the following general formulas: 
     
       
         
         
             
             
         
       
     
     Combinations of the fluids may also be utilized. The fluid is arranged and disposed to expand or contract in response to temperature. 
     Another embodiment relates to a temperature sensing element including a variable volume chamber. A fluid is disposed within the chamber. The fluid includes a compound selected from the group consisting of compounds having the following general formulas: 
     
       
         
         
             
             
         
       
     
     Combinations of the fluids may also be utilized. The fluid is arranged and disposed to expand or contract in response to a temperature change. The expansion or contraction of the fluid within the chamber varies the volume of the chamber. 
     Still another embodiment relates to a method for sensing a temperature condition. The method includes providing a variable volume chamber. The method further includes a fluid within the chamber, where the fluid includes a compound selected from the group consisting of compounds having the following general formulas: 
     
       
         
         
             
             
         
       
     
     Combinations of the fluids may also be utilized. The fluid is arranged and disposed to expand or contract in response to a temperature change. The method further includes exposing the element to a temperature change. The volume of the chamber is monitored and a temperature is determined from the volume of the chamber. 
     Certain advantages of the embodiments described herein are a reduced hazard fluid, including reduced toxicity, flammability and reductions in other hazards with respect to toluene. 
     In addition, the thermal fluids are capable of replacing current thermal fluids without significant changes in design or alternation of existing equipment. 
     Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a temperature sensing element according to an embodiment. 
         FIG. 2  is a volumetric device according to an embodiment. 
         FIGS. 3A and 3B  shows data of volumetric change over temperature ranges of a fluid according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     The thermal fluids or temperature sensing fluids according to one embodiment include ethylene glycol diacetate (CH 3 COOCH 2 CH 2 OOCCH 3 ), also known as 1,2-ethanediol diacetate, ethylene diacetate, 1,2-diacetoxyethane and/or 2-(acetyloxy)ethyl acetate and propylene glycol diacetate (CH 3 CH(OCOCH 3 )CH 2 OCOCH 3 ), also known as 1,2-propanediol diacetate, propylene diacetate, 1,2-diacetoxypropane and/or 2-(acetyloxy)-1-methylethyl acetate. Specifically, the thermal fluids according to one embodiment includes compositions having a compound selected from the group consisting of compounds having the following general formulas: 
     
       
         
         
             
             
         
       
     
     Combinations of the fluids may also be utilized. 
     The thermal fluids used in temperature sensing elements of the one embodiment include fluids having a β and thermal characteristics substantially identical to toluene. Table 1 describes values for β for toluene as well as for the two thermal fluids in a temperature range of −58 degrees F. to 392 degrees F. 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 β VALUES FOR TOLUENE AND REPLACEMENT FLUIDS 
               
               
                   
               
             
            
               
                 Toluene β (degrees Fahrenheit −1  (° F. −1 )), (degrees Celsius −1  (° C. −1 )): 
               
            
           
           
               
               
            
               
                 0.000600-0.000630 (−58 to 32 degrees Fahrenheit −1  (° F.)) 
                 0.00134-0.00140 (−50 to 0 degrees Celsius −1  (° C.)) 
               
               
                 0.000630-0.000664 (32 to 122 degrees Fahrenheit −1  (° F.)) 
                 0.00140-0.00148 (0 to 50 degrees Celsius −1  (° C.)) 
               
               
                 0.000664-0.000706 (122 to 212 degrees Fahrenheit −1  (° F.)) 
                 0.00148-0.00157 (50 to 100 degrees Celsius −1  (° C.)) 
               
               
                 0.000706-0.000758 (212 to 302 degrees Fahrenheit −1  (° F.)) 
                 0.00157-0.00169 (100 to 150 degrees Celsius −1  (° C.)) 
               
               
                 0.000758-0.000828 (302 to 392 degrees Fahrenheit −1  (° F.)) 
                 0.00169-0.00184 (150 to 200 degrees Celsius −1  (° C.)) 
               
            
           
           
               
            
               
                 Ethylene glycol diacetate β (degrees Fahrenheit −1  (° F. −1 )), (degrees Celsius −1  (° C. −1 )) 
               
               
                 Thermal Fluid #1: 
               
            
           
           
               
               
            
               
                 0.000529-0.000553 (−58 to 32 degrees Fahrenheit −1  (° F.)) 
                 0.00098-0.00103 (−50 to 0 degrees Celsius −1  (° C.)) 
               
               
                 0.000553-0.000580 (32 to 122 degrees Fahrenheit −1  (° F.)) 
                 0.00103-0.00108 (0 to 50 degrees Celsius −1  (° C.)) 
               
               
                 0.000580-0.000610 (122 to 212 degrees Fahrenheit −1  (° F.)) 
                 0.00108-0.00114 (50 to 100 degrees Celsius −1  (° C.)) 
               
               
                 0.000610-0.000649 (212 to 302 degrees Fahrenheit −1  (° F.)) 
                 0.00114-0.00121 (100 to 150 degrees Celsius −1  (° C.)) 
               
               
                 0.000649-0.000697 (302 to 392 degrees Fahrenheit −1  (° F.)) 
                 0.00121-0.00130 (150 to 200 degrees Celsius −1  (° C.)) 
               
            
           
           
               
            
               
                 Propylene glycol diacetate β (degrees Fahrenheit −1  (° F. −1 )), (degrees Celsius −1  (° C. −1 )) 
               
               
                 Thermal Fluid #2: 
               
            
           
           
               
               
            
               
                 0.000580-0.000606 (−58 to 32 degrees Fahrenheit −1  (° F.)) 
                 0.00108-0.00113 (−50 to 0 degrees Celsius −1  (° C.)) 
               
               
                 0.000606-0.000635 (32 to 122 degrees Fahrenheit −1  (° F.)) 
                 0.00113-0.00118 (0 to 50 degrees Celsius −1  (° C.)) 
               
               
                 0.000635-0.000670 (122 to 212 degrees Fahrenheit −1  (° F.)) 
                 0.00118-0.00125 (50 to 100 degrees Celsius −1  (° C.)) 
               
               
                 0.000670-0.000711 (212 to 302 degrees Fahrenheit −1  (° F.)) 
                 0.00125-0.00132 (100 to 150 degrees Celsius −1  (° C.)) 
               
               
                 0.000711-0.000763 (302 to 392 degrees Fahrenheit −1  (° F.)) 
                 0.00132-0.00142 (150 to 200 degrees Celsius −1  (° C.)) 
               
               
                   
               
            
           
         
       
     
     The thermal fluids #1 and #2 have an average coefficient of thermal expansion of from about 0.00098 inverse degrees Celsius (° C. −1 ) to about 0.00130 inverse degrees Celsius (° C. −1 ) (Thermal Fluid #1) or from about 0.00108 inverse degrees Celsius (° C. −1 ) to about 0.00142 inverse degrees Celsius (° C. −1 ) (Thermal Fluid #2) at operational temperatures. Operational temperatures include those temperatures for which the HVAC &amp; R equipment may be exposed. Operational temperature include a range from about −58 degrees Fahrenheit (° F.) to about 392 degrees Fahrenheit (° F.) (−50 degrees Celsius (° C.) to about 200 degrees Celsius (° C.)). 
     Thermal fluids #1 and #2 have not been classified as hazardous materials by the U.S. Department of Transportation and include a NFPA classification within the NFPA fire diamond as having Health Values of 1, Flammability Values of 2 and Reactivity Values of 0. The thermal fluid according to one embodiment is less hazardous than toluene. By less hazardous, the thermal fluids have lower flammability than toluene and/or have a lower health risk than toluene. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 SUBSTANCE IDENTIFICATION 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 THERMAL 
                 THERMAL 
               
               
                 CHARACTERISTIC 
                 TOLUENE 
                 FLUID #1 
                 FLUID #2 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Fluid known as: 
                 Methylbenzene, 
                 1,2-Ethanediol, 
                 1,2-Propanediol, 
               
               
                   
                 Toluol or 
                 diacetate, Ethylene 
                 diacetate, 
               
               
                   
                 Phenylmetane 
                 glycol diacetate, 
                 Propylene glycol 
               
               
                   
                   
                 Ethylene diacetate, 
                 diacetate, 
               
               
                   
                   
                 1,2-Diacetoxyethane, 
                 Propylene 
               
               
                   
                   
                 2-(Acetyloxy)ethyl 
                 diacetate, 
               
               
                   
                   
                 acetate 
                 1,2-Diacetoxypropane, 
               
               
                   
                   
                   
                 2-(Acetyloxy)-1- 
               
               
                   
                   
                   
                 methylethyl acetate 
               
               
                   
                   
                   
                 2-(Acetyloxy)ethyl 
               
               
                   
                   
                   
                 acetate 
               
               
                 Formula 
                 C 6 H 5 CH 3   
                 C 6 H 10 O 4   
                 C 7 H 12 O 4   
               
               
                 CAS Number 
                 108-88-3 
                 111-55-7 
                 623-84-7 
               
               
                 Appearance 
                 Clear, colorless 
                 Clear, colorless 
                 Colorless liquid 
               
               
                   
                 liquid (Saybolt +28- 
                 liquid (APHA 15 
                   
               
               
                   
                 +30) 
                 Max) 
                   
               
               
                 Odor 
                 Aromatic, benzene- 
                 Mild, pleasant 
                 Mild, pleasant 
               
               
                   
                 like 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 PHYSICAL AND CHEMICAL PROPERTIES 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 THERMAL 
                 THERMAL 
               
               
                 CHARACTERISTIC 
                 TOLUENE 
                 FLUID #1 
                 FLUID #2 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 Molecular Weight 
                 92.15 
                 146.12 
                 160.17 
               
               
                 Boiling Point 
                  111° C. 
                 186-193° C. 
                 190-195° C. 
               
               
                 @ 760 mm Hg 
                  (232° F.) 
                 (366.8-373.3° F.)  
                   (374-379.4° F.) 
               
               
                 Melting Point 
                 −95° C. 
                 −40.9-−30.9° C. 
                 −38.9-−30.9° C. 
               
               
                   
                 (−139° F.)  
                 (−42.7-−23.6° F.) 
                 (−38.0-−23.6° F.) 
               
               
                 Specific Gravity 
                 0.86 
                 1.106 ± 0.002 
                 1.059 ± 0.002 
               
               
                 @ 20/20 ° C./TD 
                   
                   
                   
               
               
                 Vapor Density (vs air) 
                 3.14 
                 5.04 
                 5.52 
               
               
                 Vapor Pressure 
                 22.0 
                 0.24 
                 0.57 
               
               
                 @ 20 C (68° F.) Torr 
                   
                   
                   
               
               
                 Evaporation Rate 
                 2.24 
                 0.02 
                 0.02 
               
               
                 (butyl acetate = 1): 
                   
                   
                   
               
               
                 Flash Point 
                    4° C. 
                   88-96.1° C. 
                     87° C. 
               
               
                   
                 (39.2° F.)  
                   (190-209.9° F.) 
                    (188° F.) 
               
               
                   
                   
                 (Cleveland open 
                   
               
               
                   
                   
                 cup) 
                   
               
               
                 Solubility in Water 
                 0.5 
                 160 
                 77 
               
               
                 @ 20° C. (68° F.) g/l 
                 (0.05 gm/100 gm 
                   
                   
               
               
                   
                 water) 
                   
                   
               
               
                 Dynamic Viscosity 
                 0.55 
                 2.9 
                 3.0 
               
               
                 @ 25° C. cP 
                   
                   
                   
               
               
                 Viscosity @ 20° C. cSt 
                 0.68 
                 2.58 
                 2.83 
               
               
                 Surface Tension 
                 28.6 
                 20 
                 — 
               
               
                 (mN/m) 
                   
                   
                   
               
               
                 Refractive Index @ 
                 1.4933 
                 1.4159 
                 1.414 
               
               
                 20° C. 
                   
                   
                   
               
               
                 Acidity, as Acetic 
                 No Free acid 
                 0.05% Max 
                 — 
               
               
                 Acid, WT % (ASTM 
                 (Neutral) 
                   
                   
               
               
                 D-847) 
                   
                   
                   
               
               
                 Chemical Stability 
                 Stable under 
                 Stable under 
                 Stable under 
               
               
                   
                 ordinary conditions 
                 ordinary conditions 
                 ordinary conditions 
               
               
                 Autoignition 
                  480° C. 
                    481° C. 
                    481° C. 
               
               
                 Temperature 
                  (896° F.) 
                 (897.80° F.) 
                 (897.80° F.) 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 4 
               
             
            
               
                   
               
               
                 REGULATORY INFORMATION 
               
            
           
           
               
               
               
               
            
               
                 CHARACTER- 
                   
                 THERMAL 
                 THERMAL 
               
               
                 ISTIC 
                 TOLUENE 
                 FLUID #1 
                 FLUID #2 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 DOT 
                 Hazard Class 3,  
                 Not Listed 
                 Not Listed 
               
               
                   
                 PG II, Flammable 
                   
                   
               
               
                   
                 Liquid 
                   
                   
               
               
                 UN Class 
                 UN1294, 
                 Not Listed 
                 Not Listed 
               
               
                 Air Transport 
                 No exceptions  
                 No exceptions  
                 No exceptions  
               
               
                   
                 for air  
                 for air  
                 for air  
               
               
                   
                 transportation 
                 transportation 
                 transportation 
               
               
                 Passenger 
                 Quantity Limit is  
                 Not Listed 
                 Not Listed 
               
               
                 Aircraft/Rail 
                  5 L. 
                   
                   
               
               
                 Cargo Aircraft 
                 Quantity Limit is 
                 Not Listed 
                 Not Listed 
               
               
                   
                 60 L 
                   
                   
               
               
                 NFPA Health 
                 2 
                 1 
                 1 
               
               
                 NFPA Fire 
                 4 
                 2 
                 2 
               
               
                 NFPA Reactivity 
                 1 
                 0 
                 0 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE 5 
               
             
            
               
                   
               
               
                 HEALTH HAZARD INFORMATION 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 THERMAL 
                 THERMAL 
               
               
                 CHARACTERISTIC 
                 TOLUENE 
                 FLUID #1 
                 FLUID #2 
               
               
                   
               
               
                 Respiratory PPE 
                 Chemical  
                 OSHA 29, CFR 
                 OSHA 29, CFR 
               
               
                   
                 Cartridge 
                 1910.134 
                 1910.134 
               
               
                   
                 Air Respirator 
                   
                   
               
               
                 Skin Protection PPE 
                 Viton or 
                 Neoprene  
                 Wear suitable 
               
               
                   
                 Viton/Neoprene 
                 Gloves 
                 protective  
               
               
                   
                 Gloves 
                   
                 clothing to  
               
               
                   
                   
                   
                 prevent contact  
               
               
                   
                   
                   
                 with skin 
               
               
                 Eye Protection PPE 
                 Safety glasses  
                 Safety glasses  
                 29, CFR 
               
               
                   
                 with side  
                 with OSHA  
                 1910.133 
               
               
                   
                 shields 
                 side shields 
                   
               
               
                 Threshold Limit 
                 100 
                 — 
                 — 
               
               
                 Values (TLV) ppm (8 
                   
                   
                   
               
               
                 h NIOSH) 
               
               
                   
               
            
           
         
       
     
       FIG. 1  shows a temperature sensing element  100  for use with a component of an HVAC&amp;R system or other system. The temperature sensing element  100  determines the temperature of a fluid or other medium in response to the expansion of a fluid  103  contained within the temperature sensing element  100 . The temperature sensing element  100  may be a component of the control system or other equipment and provide sensing and/or control for the components of the system. The temperature sensing element  100  includes a chamber  101  configured to receive a fluid  103 . The chamber  101  includes a variable volume. The volume may be varied by a movable side-wall  105 , which is capable of moving in response to expansion or contraction of the fluid  103 . The chamber  101  and side-wall  105  are fabricated from a resilient material or elastic material having a low coefficient of thermal expansion. The geometry of the chamber  101  is not limited to a cylindrical geometry and may include any geometry capable of receiving a fluid  103 . In addition, the side-wall  105  is not limited to the arrangement shown and may include any structure that provide variable volume to chamber  101 . Fluid  103  includes thermal fluids having compositions including a compound selected from the group consisting of compounds having the following general formulas: 
     
       
         
         
             
             
         
       
     
     Combinations of the fluids may also be utilized. 
     In operation, the temperature sensing element  100  is exposed to a temperature. For example, a medium whose temperature is sensed may be provided in close proximity to the temperature sensing element  100 . In addition, portions of the chamber  101  or extensions thereto may be fabricated from a thermally conductive material in contact or in close proximity to the fluid or other medium to be measured. For example, outside air or interior air may be sensed and the temperature may be determined, wherein the temperature sensing element  100  may be in contact with the air, in close proximity to the air, or a component or extension of the temperature sensing element  100  may be in contact or close proximity to the air. In response to the exposure to the medium temperatures, fluid  103  expands or contracts and the volume of chamber  101  is increased or decreased accordingly. The volume of the chamber  101  is measured and the temperature is calculated based upon the volume resulting from the exposure to the medium. The temperature can be calculated, with respect to a reference temperature, wherein the change in volume is measured from the following formula: 
       Δ V=β×V   i   ×ΔT  
 
     Calibrations based upon volumes of a known fluid or other known techniques may be utilized to provide temperature measurements with respect to a reference temperature. Likewise, differential temperatures may be measured and determined with respect to a difference in changes in volume of the thermal fluid. 
     EXAMPLE 
     The following example illustrates the similar behavior between toluene and thermal fluid #1. The test includes filling a volumetric device  200  with a predetermined volume of test fluid  203  at a predetermined temperature, wherein one device  200  is filled with toluene and another with thermal fluid #1, as shown in  FIG. 2 . Specifically, 68 mL of thermal fluid #1 was added to the device  200  at 140° F. The device  200  is composed of a glass reservoir  205  and graduated volumetric tube  207 . When the fluid filled device  200  is exposed to temperature changes, the expansion thermal coefficient of the test fluid  203  produces corresponding volume changes. Throughout the experiment, changes in temperature with respect to volume are recorded and presented in Table 2. 
     
       
         
           
               
             
               
                 TABLE 6 
               
             
            
               
                   
               
               
                 EXPERIMENTAL DATA 
               
            
           
           
               
               
               
               
               
               
            
               
                 TEMPER- 
                 THERMAL 
                 TOL- 
                 TEMPER- 
                 THERMAL 
                 TOL- 
               
               
                 ATURE 
                 FLUID #1 
                 UENE 
                 ATURE 
                 FLUID #1 
                 UENE 
               
               
                 (° F.) 
                 (ml) 
                 (ml) 
                 (° F.) 
                 (ml) 
                 (ml) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
            
               
                 140 
                 68.0 
                 68.0 
                 −30 
                 62.1 
                 61.9 
               
               
                 130 
                 67.7 
                 67.7 
                 −20 
                 62.1 
                 62.0 
               
               
                 120 
                 67.3 
                 67.3 
                 −10 
                 62.4 
                 62.4 
               
               
                 110 
                 66.9 
                 66.9 
                 0 
                 62.8 
                 62.8 
               
               
                 100 
                 66.6 
                 66.5 
                 10 
                 63.2 
                 63.1 
               
               
                 90 
                 66.2 
                 66.1 
                 20 
                 63.5 
                 63.5 
               
               
                 80 
                 65.8 
                 65.7 
                 30 
                 63.9 
                 63.8 
               
               
                 70 
                 65.5 
                 65.4 
                 40 
                 64.3 
                 64.2 
               
               
                 60 
                 65.2 
                 65.1 
                 50 
                 64.6 
                 64.5 
               
               
                 50 
                 64.9 
                 64.7 
                 60 
                 65.0 
                 64.9 
               
               
                 40 
                 64.5 
                 64.3 
                 70 
                 65.4 
                 65.2 
               
               
                 30 
                 64.1 
                 64.0 
                 80 
                 65.7 
                 65.6 
               
               
                 20 
                 63.7 
                 63.5 
                 90 
                 66.0 
                 65.9 
               
               
                 10 
                 63.5 
                 63.3 
                 100 
                 66.5 
                 66.4 
               
               
                 0 
                 63.1 
                 62.9 
                 122 
                 67.3 
                 67.2 
               
               
                 −10 
                 62.7 
                 62.5 
                 130 
                 67.5 
                 67.5 
               
               
                 −20 
                 62.4 
                 62.2 
                 140 
                 67.9 
                 68.0 
               
               
                 −30 
                 62.1 
                 61.9 
               
               
                   
               
            
           
         
       
     
     Experimental data resulting from measurements taken as the test fluid  203  is exposed to the changing temperatures is plotted in  FIGS. 3   a  and  3   b . In these figures, temperature decrease is plotted in  FIG. 3A  and temperature increase is plotted in  FIG. 3B . From both plots, it is evident that the thermal behavior of the thermal fluid is substantially identical to the thermal behavior of toluene. 
     It should be understood that the application is not limited to the details or methodology set forth in the following description or illustrated in the figures. It should also be understood that the phraseology and terminology employed herein is for the purpose of description only and should not be regarded as limiting. 
     While the exemplary embodiments illustrated in the figures and described herein are presently preferred, it should be understood that these embodiments are offered by way of example only. Accordingly, the present application is not limited to a particular embodiment, but extends to various modifications that nevertheless fall within the scope of the appended claims. The order or sequence of any processes or method steps may be varied or re-sequenced according to alternative embodiments. 
     It is important to note that the construction and arrangement of the apparatus as shown in the various exemplary embodiments is illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited in the claims. For example, elements shown as integrally formed may be constructed of multiple parts or elements, the position of elements may be reversed or otherwise varied, and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present application. 
     It should be noted that although the figures and specification herein may show and/or describe a specific order of method steps, it is understood that the order of these steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on the software and hardware systems chosen and on designer choice. It is understood that all such variations are within the scope of the application. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.