Loss Mechanisms in Low Temperature Expanders.
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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An experimental study investigated the effect of the boundary layer on the time dependence of the rate of heat transfer through cylinder walls. The experimental expander used was a closed cylinder apparatus with a fixed mass charge of helium gas. Cyclic pressure and volume data points were generated during operation of the expander. The resulting experimental pressure vs. volume data trace was stored digitally and presented graphically using a Nicolet storage oscilloscope. It was concluded that the temperature of the boundary layer gas had the controlling effect over the cylinder bulk gas temperature in determining the actual rate of heat transfer through the cylinder walls. The apparent zero rate of heat transfer point occurred when the bulk gas temperature equaled the cylinder wall temperature. The actual zero rate of heat transfer point occurred when the boundary layer gas temperature equaled the cylinder wall temperature. The boundary layer gas temperature was determined responsible for up to a 64 deg phase difference in the times of the actual and apparent zero rate of heat transfer points in the compression and expansion strokes in the cylinder.
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