4 Replies Latest reply on Sep 12, 2013 12:45 AM by Sandip Darveshi

    Please clarify Thermal question

    Jagadeesh Babu

      Hi,

       

      If one body has 560 deg temparature, that body put in ambiant temparature 4 sec. Then What is body temparature after 4 sec (means temparature lose)?

      How will do this process in thermal analysis?  Please clarify us this problem.

       

      Thanks,

      Jagadeesh

        • Re: Please clarify Thermal question
          Sandip Darveshi

          Dear Jagadeesh,

           

          If you dont mind, will like to ask you, why you want to make an analysis, cause it can be done through a simple calculations as below

          q = ε σ (Th4 - Tc4)A

          where

          q = heat transfer per unit time (W)

          ε = emissivity of the object (one for a black body)

          σ = 5.6703 10-8 (W/m2K4) - The Stefan-Boltzmann Constant

          Th = hot body absolute temperature (K)

          Tc = cold surroundings absolute temperature (K)

          A = area exposed to environment of the emitting body (m2)

           

          Just multiply above retrived q by 4 (as the body is kept for 4 seconds in environment), you will get total heat loss to environment.

          i.e.

           

          Loss to environment = Heat transfer per unit time X Time

           

          Once you recieve total loss to environment, again divide it with specific heat of body

           

          i.e. Temperature drop (or Temperature difference) =  Heat loss / Specific Heat of body

           

          So ultimate temperature of body will be equal to 560 - Temperature Drop.

           

           

          Hope this will help you.

           

          Thanks

           

          Sandip Darveshi.

            • Re: Please clarify Thermal question
              Jared Conway

              this assumes the heat loss is only from radiation. what about convection. but i agree, you could solve this problem by hand.

               

              with the software, you're looking at a transient thermal analysis in simulation professional.

                • Re: Please clarify Thermal question
                  Sandip Darveshi

                  Yes Jared you are right, I will like to correct myself.

                   

                  Total Heat Loss = Heat Loss due to Convection + Heat Loss due to Radiation.

                   

                  Convection     q (conv) = hA(Th - Tc)

                   

                  where

                  q(conv) = heat transfer per unit time due to Convection (W)

                  h = heat transfer coeficient (W/m2K)

                  Th = hot body absolute temperature (K)

                  Tc = cold surroundings absolute temperature (K)

                  A = area exposed to environment of the emitting body (m2)

                  __________________

                  Radiation     q (rad) = ε σ (Th4 - Tc4)A

                  where

                  q(rad) = heat transfer due to Radiation per unit time (W)

                  ε = emissivity of the object (one for a black body)

                  σ = 5.6703 10-8 (W/m2K4) - The Stefan-Boltzmann Constant

                  _________________

                   

                  Total Heat Loss = q(conv) + q(rad)

                   

                  Just multiply above retrived Total Heat Transfer by 4 (as the body is kept for 4 seconds in environment), you will get total heat loss to environment.

                  i.e.

                   

                  Loss to environment = Heat transfer per unit time X Time

                   

                  Divide Total Heat Loss to Environment with specific heat of body

                   

                  i.e. Temperature drop (or Temperature difference) =  Heat loss / Specific Heat of body

                   

                  So ultimate temperature of body will be equal to 560 - Temperature Drop.

                   

                  Thanks

              • Re: Please clarify Thermal question
                Jerry Steiger

                Jagadeesh,

                 

                In addition to what Sandip and Jared said, the body will not have a single temperature. The skin will be cooler than the interior.

                 

                Jerry S.