# Converting mechanical energy into heat

 Register Blogs Members List Search Today's Posts Mark Forums Read

 July 15, 2000, 06:43 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

 July 15, 2000, 19:59 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.

 July 16, 2000, 10:46 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.

 July 17, 2000, 00:30 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

 Thread Tools Display Modes Linear Mode

 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 OffTrackbacks are On Pingbacks are On Refbacks are On Forum Rules

 Similar Threads Thread Thread Starter Forum Replies Last Post Joseph CFX 14 April 20, 2010 15:45 Pinaki Bhattacharya FLUENT 0 January 29, 2009 13:33 Mark CFX 6 November 15, 2004 16:55 Coriolius CFX 4 November 5, 2004 23:29 Joseph CFX 0 October 1, 2004 08:52

All times are GMT -4. The time now is 11:28.