Oscillatory flow in tapered thermal buffer tubes

In a group of devices, such as thermo-acoustic engines and pulse tube coolers, oscillatory flows are used to achieve power generation and heat pumping or refrigeration. There are few mechanical moving parts in these devices, which makes the devices long lasting and require little maintenance. Environmental friendly inert gases are often used as flow media. Examples of such applications include power recovery from waste heat and solar powered air conditioner and cooler.

A thermal buffer tube is one of the most important components in thermo-acoustic engines and pulse tube coolers. It is meant to provide the transition from one thermal boundary condition to another without power loss, by utilizing the stratified flow in ideal circumstances. However, the oscillatory flows through thermal buffer tubes are not well understood, particular due to the presence of the temperature gradient along the tubes. Undesirable secondary flow, such as mass streaming, could occur in a wrongly-designed thermal buffer tube, which will incur significant heat and power losses.

In this proposed project, numerical and experimental investigations will be undertaken to study the flow behaviour in both straight and tapered tubes/channels at isothermal and adiabatic conditions, and to examine the effect of the geometric and thermal boundary conditions on the performance of the tube.