Abstract
M.Ing.
There are two advantages of enhanced heat transfer. Firstly a decrease in the heat exchanger size
and secondly an increase in the heat transfer coefficient. A method of increasing the heat transfer
coefficient is to insert spiralled wires in the annulus of a tube-in-tube heat exchanger. It was
decided to investigate this method further and therefore the objectives of the investigation are
twofold. First to determine what the optimum spiral angle of the wires is, and secondly what
mechanism causes the enhanced heat transfer. Specifically to determine if it is an increase in the
turbulence or an increase in the flow rotation. A numerical model that was experimentally
verified was used to do the investigation. It was concluded from the numerical results that for
optimum heat transfer, the spiral angle of the wires should be 30°. It was also found that the
mechanism for enhanced heat transfer is an increase in the rotation of the flow in the annulus.