Supersonic multiphase ejectors for high temperature heat-pumps

Description

In this presentation the challenges in the design process of an ejector for high temperature heat-pumps are presented. The benefit of the ejector, which substitutes the expansion valve in the Carnot-cycle is pressure recovery and therefore higher efficiency. However, supersonic flow is needed to drive the secondary mass flow through the evaporator. Therefore, the main part consists of a Laval nozzle where the entering liquid fluid evaporates during acceleration. Especially if the fluid is subcooled this results in severe challenges for numerical simulations due to metastable effects. The steady state simulations are done with ANSYS FLUENT using an axisymmetric 2D domain. For modelling the multiphase flow inside the ejector, two different models, the homogeneous equilibrium model (HEM) and an extension of the homogeneous relaxation model (HRM), are used. Both models are implemented using UDFs to modify the source term. As a refrigerant Butane or HFO`s like R1233zdE are used by implementing Refprop data through an UDF. The simulations shown were conducted as part of the FFG projects High-Butane, ETHP project and VLESH.

Period	7 Nov 2024
Event title	CADFEM Ansys Simulation Conference Austria: Trends and Innovations in Numerical Simulation
Event type	Conference
Location	Salzburg, AustriaShow on map
Degree of Recognition	National