Introduction and thermodynamical investigation of the Recuperative Two-Phase Cycle

Publikation: Beitrag in FachzeitschriftForschungsartikelBeigetragenBegutachtung

Abstract

Efficient thermodynamic cycles are of great importance for the decarbonisation of the global energy system. In order to increase the cycle efficiency, it is helpful to analyse cycle-dependent loss mechanisms. Based on such an analysis for conventional cycles, a concept is proposed that reduces exergy losses caused by the central temperature lift. This new approach is named Recuperative Two-phase Cycle (RTPC) and realises this central temperature lift by a liquid-two-phase recuperation, which equalises the capacity flows in the high- and low-pressure side of an internal heat exchanger (recuperator). Therefore, it is mandatory to use asymmetric working fluid mixtures. Generally, the concept can be used in heat pumps and power cycles. An advantage over known measures against cycle-dependent losses for the state of the art cycles is that this cycle directly consists out of advantageous changes of state. Besides the basic concept, different variants for various high-temperature heat reservoir characteristics are presented, as well as challenges that could arise during the technical implementation. Furthermore, a calculation program is presented to compare the new concept with cycles of the state of the art. This comparison is carried out using four hypothetical application cases in the commercial and industrial context. Three heat pumps and one power cycle are investigated, whereby subcritical and transcritical operation is covered. Due to the complexity of the working fluid selection, no claim is made that the optimum mixture for the RTPC can be found here. Furthermore, other secondary effects, which can have a positive impact on potential, could not yet be taken into account. However, in all cases, the cycle-dependent losses can be reduced. In the case of a two-stage high temperature lift heat pump, losses in the expansion valves could already be reduced by 63 % through the recuperation. The overall relative performance improvement for the assumptions made ranges between 2 % to 20 % for all study cases. The improvement is greater when the temperature lift is higher and the circuit layout is more complex. The basic theoretical functioning of the approach and its inherent potential could thus be demonstrated.

Details

OriginalspracheEnglisch
Aufsatznummer130898
FachzeitschriftApplied Thermal Engineering
Jahrgang298
AusgabenummerPart 1
PublikationsstatusVeröffentlicht - Juni 2026
Peer-Review-StatusJa

Externe IDs

ORCID /0000-0002-9892-6746/work/213144237
ORCID /0000-0003-3031-9138/work/213144590

Schlagworte

Schlagwörter

  • Rekuperativer Zweiphasen-Kreisprozess