Transient heat conduction using thermocouples, thermochromic liquid crystals, and numerical simulation

Abstract

An apparatus to visually and electronically observe the transient temperature changes in a heat-conducting body, and a method for teaching heat conduction to students incorporating the apparatus. The apparatus includes a heat-conducting body, and a pair of electric strip heaters attached to adjacent sides of the heat-conducting body for conducting heat therethrough. A pair of heat exchangers are attached to sides of the heat-conducting body that are opposite to the sides the electric strip heaters are attached to. A thermochromic liquid crystal sheet is provided on a top surface of the heat-conducting body and displays the transient heat conduction through the heat-conducting body. An insulating plate is located above the top surface of the heat-conducting body to create a gap between the thermochromic liquid crystal sheet and the insulating plate. A plurality of thermocouples are attached to a bottom surface of the heat-conducting body for measuring the transient heat conduction within the heat-conducting body.

What is claimed is:  
     
         1 . An apparatus for observing and measuring transient heat conduction, comprising: 
 a heat-conducting body;    at least one heater attached to one side of said heat-conducting body for conducting heat through said heat-conducting body;    at least one heat exchanger attached to a side of said heat-conducting body that is opposite to the side said heater is attached to;    a thermochromic liquid crystal sheet attached to a top surface of said heat-conducting body, wherein the color of said thermochromic liquid crystal sheet varies due to the transient heat conduction through said heat-conducting body;    an insulating plate located above the top surface of said heat-conducting body to create a gap between said thermochromic liquid crystal sheet and said insulating plate; and    a plurality of thermocouples attached to a bottom surface of said heat-conducting body for measuring the transient heat conduction within said heat-conducting body.    
     
     
         2 . An apparatus for observing and measuring transient heat conduction as recited in  claim 1 , wherein said at least one heater comprises a pair of heaters connected to adjacent sides of said heating conducting body, and at least one heat exchanger comprises a pair of heat exchangers attached to sides of said heat-conducting body that are opposite to the sides said pair of heaters are attached to.  
     
     
         3 . An apparatus for observing and measuring transient heat conduction as recited in claim  1 , wherein said insulating plate insulates said heat-conducting body and restricts heat conduction through the top surface of said heat-conducting body.  
     
     
         4 . An apparatus for observing and measuring transient heat conduction as recited in  claim 1 , further comprising an insulating material supporting the bottom surface of said heat-conducting body and restricting heat conduction through the bottom surface of said heat-conducting body.  
     
     
         5 . An apparatus for observing and measuring transient heat conduction as recited in  claim 1 , wherein said plurality of thermocouples measure the transient heat conduction based upon the composition of the said heat-conducting body, the power supplied to said heater, and the cooling rate of said heat exchanger.  
     
     
         6 . An apparatus for observing and measuring transient heat conduction as recited in  claim 1 , further comprising means to record the transient heat conduction within said heat-conducting body.  
     
     
         7 . An apparatus for observing and measuring transient heat conduction as recited in  claim 1 , wherein said means to record the transient heat conduction comprises a color charge-coupled device (CCD) camera.  
     
     
         8 . A method for teaching heat conduction, comprising: 
 providing an apparatus having: 
 a heat-conducting body,  
 at least one heater attached to one side of said heat-conducting body for conducting heat through said heat-conducting body,  
 at least one heat exchanger attached to a side of said heat-conducting body that is opposite to the side said heater is attached to,  
 a thermochromic liquid crystal sheet attached to a top surface of said heat-conducting body, wherein the color of the thermochromic liquid crystal sheet varies due to the transient heat conduction through said heat-conducting body,  
 an insulating plate located above the top surface of said heat-conducting body to create a gap between said thermochromic liquid crystal sheet and said insulating plate,  
 a plurality of thermocouples attached to a bottom surface of said heat conducting body for measuring the transient heat conduction within said heat-conducting body, and  
 means to record the transient heat conduction within the heat-conducting body;  
   selecting a temperature and heat flux boundary conditions for the heat-conducting body;    recording the temperatures of portions of the heat-conducting body using the plurality of thermocouples; and    recording the colors displayed by the thermochromic liquid crystal sheet with the means to record the transient heat conduction.    
     
     
         9 . A method for teaching heat conduction as recited in  claim 8 , wherein the heat flux boundary conditions are set by setting the temperature of the heat exchanger.  
     
     
         10 . A method for teaching heat conduction as recited in  claim 8 , wherein the step of recording the temperatures of portions of the heat-conducting body comprises measuring the temperatures recorded by the plurality of thermocouples.  
     
     
         11 . A method for teaching heat conduction as recited in  claim 8 , wherein the step of recording the temperatures of portions of the heat-conducting body and the step of recording the colors displayed by the thermochromic liquid crystal sheet are performed simultaneously.  
     
     
         12 . A method for teaching heat conduction as recited in  claim 8 , further comprising: 
 terminating the method when the temperature of the heat-conducting body is no longer changing with time.    
     
     
         13 . A method for teaching heat conduction as recited in  claim 8 , further comprising: 
 plotting the temperature contours obtained from the temperatures recorded by the plurality of thermocouples; and    comparing the temperature contours with recorded colors of the thermochromic liquid crystal sheet.