Thomas J. Hofler
Phys. Dept., Naval Postgraduate School, Monterey, CA 93943
Typically, hot and cold copper fin heat exchangers couple heat into and out of the stack. Effective heat transfer means that large amounts of heat are carried across the stack interface with a small temperature difference. Effective heat transfer is also efficient if thermoviscous losses in the heat exchanger are minimized. This is particularly difficult to achieve in engines having high-power density and large gas displacement amplitudes. A simple model for heat exchanger effectiveness and its relationship to fin length and spacing is discussed. Heat exchanger fins that are shorter than the peak gas particle displacement can be effective if the fin spacing is sufficiently small.