Subject: RE: Heat Transfer of Electric motor
From: "sameer mohrir" <sameerdm@hotmail.com>
Date: Sat, 09 Mar 2002 07:28:38 
Reply-To: "MSC.NASTRAN Discussion Group" <msc.nastran@lists.mscsoftware.com>
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Hi

I will explain u my problem i am facing with analysis of electric motor.
motor of following dimension ID 0.151m and OD 0.18m and length of 0.203m is 
modelled in FEMAP with properties of material with conductiivty of 45w/m2K 
(steel)

Boundary condition applied as follow
Nodal- inside temperature 145 deg. c
and Elemental -convection 25W/m2K at 20deg.C on outside surface of motor

And after solving the problem in MSC Nastran i get 136 deg.C temperature on 
outer surface .But as per standard outside temperature of electric motor 
should be 98 deg.C

So please could you tell us how much velocity of air to be taken to get 
surface temp as 98 deg.C

thanking you

Sameer D.Mohrir


>From: Torfinn.Tobiassen@kongsberg.com
>Reply-To: "MSC.NASTRAN Discussion Group" 
><msc.nastran@lists.mscsoftware.com>
>To: "MSC.NASTRAN Discussion Group" <msc.nastran@lists.mscsoftware.com>
>Subject: [msc.nastran] RE: Heat Transfer of Electric motor
>Date: Fri, 8 Mar 2002 12:06:08 +0100
>
>MSC.NASTRAN Discussion
>Hi
>
>The heat transfer coefficient is related to the Nusselt number by the
>following expression:
>
>h=(k/D)Nu, k=Thermal conductivity, D=diameter, Nu=Nusselt number
>
>Nu can be calculated from the Reynolds and Prandtl numbers.
>
>Pr=0.69, Re=VD/v=8.3E4, V=airspeed, D=Diameter, v=Kinematic viscosity
>
>Nu=0.3+((0.62Re**0.5*Pr**0.33)/((1+(0.4/Pr)**0.67)**0.25))*(1+(Re/282000
>)**0.5, 2E4 < Re < 4E5
>Nu=213.8
>
>You will find the formula in a Heat Transfer textbook (E.g. Heat
>Transfer by A. F. Mills)
>
>Best Regards
>
>Torfinn Tobiassen
>Kongsberg Defence & Aerospace
>
>
>-----Original Message-----
>From: sameerdm@hotmail.com [ mailto:sameerdm@hotmail.com
><mailto:sameerdm@hotmail.com> ]
>Sent: 8. mars 2002 05:21
>To: msc.nastran@lists.mscsoftware.com
>Subject: [msc.nastran] RE: Heat Transfer of Electric motor
>
>
>MSC.NASTRAN Discussion
>Hi
>
>Thanks for your analysis can u please tell me how u have calculated hc
>(heat transfer coeff)
>
>regards
>
>Sameer D.Mohrir
>Pune (India)
>
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