High-Efficiency Reciprocating Compressors and Expanders
Luona Yu1, Aly I. Taleb1, Paul Sapin1, Caroline Willich2, Drazen
Fabris1 Alexander J. White2, and Christos N. Markides1 1Clean
Energy Processes (CEP) Laboratory, Department of Chemical
Engineering, Imperial College London, London SW7 2AZ, U.K.
2Cambridge University Engineering Department, Trumpington Street,
Cambridge CB2 1PZ, U.K. Outline Introduction and Motivation PTES,
CAES, etc.
Organic Rankine Cycles/Thermohydraulic Generators Thermofluidic
Oscillators (NIFTE) Simplified analytical models Fundamental
understanding and design Gas Springs Why gas springs? Experiment
Simulation Reciprocating-Piston Compressors / Expanders Loss
mechanisms State of the art Conclusion Pumped-Thermal Energy
Storage (PTES)
from White, Parks & Markides (2013), Thermodynamic analysis of
pumped thermal electricity storage. Applied Thermal
Engineering,53(2), Isentropic Ltd. Valve, Pat. No Other systems
with reciprocating machines/processes
Condenser Evaporator Expander Generator Pump Reciprocating-piston
compressors/expanders
Loss Mechanisms: Pressure losses across valves at intake and
exhaust Heat losses Mass leakage (Mechanical, not considered here)
(Mechanical losses, etc.) Why Gas Springs? Focus on thermodynamic
losses due to thermal-energy exchange processes in reciprocating
components Fluid: Lumped, dynamic analytical model
Kornhauser & Smith (1994). Journal of Heat Transfer, 116(3),
(And what not to do) Solid: Conjugation and thermal impedance
(There are also nonlinear conjugate processes that give rise to
frequency spreading in the heat exchange) Still, missing
information on the HTC/Nusselt number
Results Effect of the solid: materials, geometry Still, missing
information on the HTC/Nusselt number CFD simulation: Velocity
field CFD simulation: Temperature field Experimental
apparatus
Measurement of 3 bulk parameters: Pressure P - pressure transducer
Pressure V - rotary sensor Temperature T - ultrasonic sensor
Experimental results: P, V, T
Experimental results: P-V diagram
Only unknown Comparison CFD Model Experiment Reciprocating-piston
expanders: Steady-state models Lumped, dynamic analytical
model
Imposed motion: Perfect gas: Mass conservation: Energy
conservation: Model results: P-V indicator diagrams Model results:
Heat transfer
Newtons law: Complex Nusselt: Still working on this and need
insight from CFD/experiments Model results: Bringing it all
together
Pressure Thermal Conclusions Interest in reciprocating
compression/expansion machines
Significant losses in system performance from these processes
Dynamic/unsteady heat transfer process Conjugate (and nonlinear)
heat transfer effects Valve losses and coupling to heat transfer
Theory, CFD and experimental tools aimed at: Understanding
underlying loss mechanisms/performance Designing components and
systems
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