PhD defense alert: Xander van Heule

Modelling and Experimental Study of Thermal Non-Equilibrium Two-Phase Expansion within a Free Linear Expander

You are invited to join the PhD Defense of:

Name: Xander van Heule

Title: Modelling and Experimental Study of Thermal Non-Equilibrium Two-Phase Expansion within a Free Linear Expander

Topic: In a world of rapidly increasing energy demand, renewable energy sources and improved energy efficiency play a central role in achieving a sustainable future. Many energy-conversion technologies, such as heat-to-power or power-to-heat systems, rely on thermodynamic cycles in which a working fluid undergoes either compression or expansion. Traditionally, these cycles operate with superheated vapour at the inlet of the compressor or expander. However, introducing a liquid–vapour mixture (i.e. two-phase operation) has been shown to offer potential performance benefits.

This PhD research investigates the feasibility of two-phase expansion, specifically within heat-to-power cycles. While promising, the development of machines capable of operating in this regime poses several challenges. A key issue is the presence of non-equilibrium effects, which delay the phase transition from liquid to vapour during expansion. Experimental investigation combined with the development of a predictive model reveals that this delayed evaporation can reduce the expected work output. By taking this into account, better designs can be achieved that better exploit the potential of two-phase expansion.

Date defense: 10 February 2026 | 5 PM

Online: link to follow online