Conduction Loss

Conduction is another loss mechanism that will be discussed in this chapter. Since

Stirling engines incorporate a hot side (heater and expansion space) and a cold side (cooler

And compression space), there are chances of direct conductive heat flow from the hot side to the cold side that should be identified and minimized. As a result of direct heat conduction, there is an increased thermal burden upon heater and cooler, which in turn, decreases the overall efficiency of the Stirling engine. The conduction loss, Qcand, in its simple form, is calculated as,

A

Qcond = kR AT (3.40)

Where k is the conductivity of the material through which heat conduction occurs, A is the effective cross sectional area normal to the heat flow path, L is the effective length of heat conduction path, and AT is the temperature difference across the conduction path.

Since there is a substantial temperature difference across displacer piston, this element

Could provide a substantial heat leakage path, if not designed properly. Regenerator is subject to almost the same temperature difference as displacer piston. However, since it is made of porous material (woven screens, metal felts, etc.) the effective heat conduction area is considerably small, causing a minimal direct heat flow through regenerator. Any other direct path between hot side and cold side of the engine (e. g., heat exchanger housing) can be a potential source of heat loss and should be addressed properly.

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