Lecture 2 example, thermal system (liquid cooling)TutorialCurrent spec2:28 min

ENGR5001 Lecture 2 worked example 4, thermal system (slides 23-25)

A container of liquid at temperature θ\theta stands in surroundings at temperature θS\theta_S (for example a cup of coffee cooling in a room).

Formulas you may need
  • Newton's law of cooling: rate of change of temperature proportional to the excess temperature (learn this)
  • Generalised first order form τdxdt+x=Ku(t)\tau\dfrac{dx}{dt} + x = Ku(t) (learn this)
  1. (a)
    State the modelling assumption (Newton's law of cooling) and write it as a differential equation with a model coefficient K′K'. Identify the output and the input.
  2. (b)
    Put the model into the generalised first order form and give the time constant and steady state gain. What sign must K′K' have, and why?