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