CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > General Forums > Main CFD Forum

Converting mechanical energy into heat

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   July 15, 2000, 07:43
Default Converting mechanical energy into heat
  #1
Marat Hoshim
Guest
 
Posts: n/a
Hello,

I have a basic question concerning the capabilities of CFD. In hydrodynamic brakes for trucks you have some kind of impeller on the drive shaft which runs in a box of oil. The impeller is designed to convert mechanical energy into heat of the oil. 1. Is that conversion process reproduced by the solving NS-equations + energy equation ?

2. If I'm only interested in the velocity field inside the impeller box, is it necessary to solve the energy equation as well ? Or do I get different solution for the velocity field considering the energy equation or not ?

Any comments will be appreciated !

Marat
  Reply With Quote

Old   July 15, 2000, 20:59
Default Re: Converting mechanical energy into heat
  #2
John C. Chien
Guest
 
Posts: n/a
(1). When the space shuttle returns from the space, it must enter the atmosphere at very high speed. Cfd has been used to simulate the hypersonic flow over the space shuttle, so that heat shield can be designed to withstand the high temperature field produced by the viscous and shock effects. This was done many many years ago. (2). So, you can safely say that cfd can produce the high temperature field as a result of viscous effect. (it is proportional to the F_viscous x V_object. where F_viscous is proportional to V_object squared. So, both high velocity and high viscosity can produce high temperature field.) (3). By the way, it is necessary for the non-professional to solve the "full" set of equations all the time, including the energy equation. Energy equation always converge much faster than other equations.
  Reply With Quote

Old   July 16, 2000, 11:46
Default Re: Converting mechanical energy into heat
  #3
PRAVEEN C
Guest
 
Posts: n/a
For imcompressible flow, the mass and momentum conservation equations are decoupled from the energy equation if the coefficient of viscosity and heat conduction can be assumed to be independent of temperature. If in your case, the viscosity and heat conduction coefficients are almost constant for the temperatures that are encountered, then you can ignore the energy equation.
  Reply With Quote

Old   July 17, 2000, 01:30
Default Re: Converting mechanical energy into heat
  #4
Tareq Al-shaalan
Guest
 
Posts: n/a
Check the oil viscosity as a function of temperature. If it is strongly a function temperature, then you need to solve the energy equation coupled with momentum and continuity equations. If it is not, then most probably you need only momentum and continuity equations.

Tareq
  Reply With Quote

Reply


Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
ATTENTION! Reliability problems in CFX 5.7 Joseph CFX 14 April 20, 2010 16:45
Incompressible flow: mechanical energy terms Pinaki Bhattacharya FLUENT 0 January 29, 2009 13:33
Convective Heat Transfer - Heat Exchanger Mark CFX 6 November 15, 2004 16:55
Heat energy imbalance Coriolius CFX 4 November 5, 2004 23:29
VISCOUS heat dissipation Joseph CFX 0 October 1, 2004 09:52


All times are GMT -4. The time now is 01:10.