Monthly Archives: May 2011

The Steady Flow Energy Equation

Whilst talking to a number of students recently I realised two things:

  1. Students tend to think of problems as a series of special cases and don’t do a good job of connecting the underlying engineering theory.
  2. The steady flow energy equation is an awesome piece of underlying theory.

The steady flow energy equation (SFEE for short) for those who don’t recall is an energy of analysis of systems with a number of flows in and out of them.  It relates work and heat  transfers across the boundaries to enthalpy changes, velocity changes and gravitational potential energy changes.  I would put this into an equation but frankly the in-built editor for this blog doesn’t handle equations very well.

Anyway with the SFEE allows you to analyse:

  • open and closed feedheaters
  • gas mixtures
  • cooling with and without condensation, heating with and without evaporation
  • humidification by spraying
  • turbines, expanders, pumps and compressors

Basically it is one of only a handful for key pieces of knowledge you need for an undergraduate education in engineering thermodynamics – the rest is application.

This is something I will be emphasising in future courses…


I recently discovered coffee and now have  latte and a panini for lunch each day.  It is like the 1980s have caught up with me…

Moving through history I am no setting up a “snowcam” so that I can view the snow at my house over the web.  1999 is calling and would like its technology back!

So there are a number of tools I am using to get this done:

  • fswebcam which is a very simple program for getting an image out of the camera aka “fswebcam –resolution 1280×800 webcam.jpg”
  • expect to run an automated script to upload to a webdav server
  • cadaver to actually put the files on the web server
  • cron to automate the job.  In theory this will upload a picture of my car everyone morning at 8:10am!

So we shall see if this actually works!  If it does I’ll put the scripts up – it has been a lot more complicated than I thought it would be.

Edit: o.k. for some reason this doesn’t work at all.  I blame the cron job – I’ll update if I get it working…

Edit2: professional tip, to get cron to run point it at something that is actually executable…  this should now work!