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Session: Volumetric expanders II
Session starts: Tuesday 08 October, 10:00
Presentation starts: 10:40
Room: Van Beuningen Zaal

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Jorrit Wronski (Technical University of Denmark)
Jean-François Oudkerk (University of Liège)
Fredrik Haglind (Technical University of Denmark)

Abstract:
This work presents models covering the operation of a small-scale reciprocating expander for a medium temperature heat source of 150 C. A fictitious expander with a stroke and bore of 10 cm is expected to have a clearance volume 20 cm3 resulting in a maximum cylinder volume of approximately 805 cm3 . Assuming a cogeneration scenario, condenser pressure of a power cycle changes with heat demand. This study considers the effect of elevated back-pressure on the operation of the expansion device concluding with an estimation for achievable power output under ideal operating conditions. Such an approach contributes detailed information to the expander selection process by comparing published work on scroll-type devices to the detailed simulation of a reciprocating piston expander. As a result, a basic control scheme with variable injection timing that is based on condenser temperature only is sketched. Implementing the cutoff angle and condenser temperature relation in an algorithm helps to maintain a high efficiency of approximately 90 percent over a wide range of operating conditions.