Reciprocating-piston devices can be used as high-efficiency
compressors and/or expanders. With an optimal valve design and
by carefully adjusting valve timing, pressure losses during intake
and exhaust can be largely reduced. The main loss mechanism
in reciprocating devices is then the thermal irreversibility due
to the unsteady heat transfer between the compressed/expanded
gas and the surrounding cylinder walls. In this paper, pressure,
volume and temperature measurements in a piston-cylinder
crankshaft driven gas spring are compared to numerical results.
The experimental apparatus experiences mass leakage while the
CFD code predicts heat transfer in an ideal closed gas spring.
Comparison of experimental and numerical results allows one to
better understand the loss mechanisms in play. Heat and mass
losses in the experiment are decoupled and the system losses
are calculated over a range of frequencies. As expected, compression
and expansion approach adiabatic processes for higher
frequencies, resulting in higher efficiency. The objective of this
study is to observe and explain the discrepancies obtained between
the computational and experimental results and to propose
further steps to improve the analysis of the loss mechanisms
Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016.