Open Access

ARTICLE

Graphical Analysis and 3D Thermodynamic Cycle Construction for Variable-Composition Ejector Refrigeration Cycle

Anxiang Shen¹, Xinxin Ren², Tao Wang¹, Jianqiu Zhou^1,2,*
1 School of Mechanical and Power Engineering, Nanjing Tech University, No. 30 Puzhu Road(S), Nanjing, China
2 School of Energy Science and Engineering, Nanjing Tech University, No. 30 Puzhu Road(S), Nanjing, China
* Corresponding Author: Jianqiu Zhou. Email:
(This article belongs to the Special Issue: High Efficiency Cooling Technology in New and Renewable Energy System)

Frontiers in Heat and Mass Transfer https://doi.org/10.32604/fhmt.2026.082573

Received 19 March 2026; Accepted 19 May 2026; Published online 03 July 2026

Abstract

To address the growing number of variable-composition ejector refrigeration cycles, this study proposes analyzing the matching performance between working fluids and cycles through 3D (Temperature-Entropy-Mass fraction) Thermodynamic Diagrams. The ejector refrigeration cycle is decoupled into a driving module and a refrigeration module, and a theoretical upper-bound model (COP_limiting) that depends only on working-fluid properties is derived from the T-s diagram. Graph-theoretic analysis yields an explicit relation between COP_limiting and fluid-specific parameters such as Δs_b-b^′/Δs_a-b^′ and Δs_e-e^′/Δs_d-e^′. Definition of k₁ (ΔT_4–7/Δs_e-e^′) and k₂ (ΔT_3–4/Δs_b-b^′) reveals that wet fluids favour the refrigeration module, whereas dry fluids favour the driving module. The influence of different mixtures has been also analyzed. The mixture of R227ea/R152a, R245fa/R134a, and Isobutane/pentane achieved their maximum COP_limiting values at x = 0.5, 0.4, and 0.2, respectively. These optimal compositions all falling within the high-slope region of k₂. Additional parameters (x, t_g, t_c) are evaluated: At MF_t = 0.5, increasing x from 0.1 to 0.2 raises the limiting cycle COP from 0.08 to 0.18 and elevates t_e from −79.24°C to −35.15°C. Raising t_g from 85°C to 95°C lowers the limiting cycle COP from 0.1269 to 0.1235 while lifting t_e from −56.00°C to −49.18°C. Increasing t_c from 30°C to 40°C boosts the limiting cycle COP from 0.1216 to 0.1285 and raises t_e from −60.84°C to −44.26°C.

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Keywords

Ejector refrigeration cycle; limiting cycle; zeotropic mixture; graph theory

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