Investigation on ejector design for CO₂ heat pump applications using Dymola

Abstract

In this paper, the Dymola modelling tool is used to study the influence of ejector design onto the whole heat pump cycle working with carbon dioxide. The cycle is built using the components provided by the TIL Modelica library. It is found that the ejector models in TIL are quite limited, namely by their inability to properly capture the on-design plateau and rapid decrease in performance in off-design operation. Therefore, an in-house state-of-the-art ejector model, originally developed in Python, is implemented as a Dymola object. This model is then calibrated onto CO₂ experimental data. The operation of a simple CO₂ heat pump system is investigated, with focus on the ejector sizing at fixed geometry. It is found that there exists an ejector size that maximises the COP of the cycle. Furthermore, critical ejector pressure is not reached at this optimum COP point; the ejector is operating well under the on-design regime.

Keywords

ejector / heat pump cycle / carbon dioxide / modelica / thermodynamic model / COP

References

[1] Liu J, Wang L, Jia L, Xue H. Thermodynamic analysis of the steam ejector for desalination applications. Appl. Therm. Eng. 2019;159(1):113883.

[2] Liu J., Wang L., Jia L., Xue H. Thermodynamic analysis of the steam ejector for desalination applications // Appl. Therm. Eng. 2019. Vol. 159, N. 1. P. 113883.

[3] Ipakchi O, Mosaffa AH, Garousi Farshi L. Ejector based CO₂ transcritical combined cooling and power system utilizing waste heat recovery: A thermoeconomic assessment. Energy Convers. Manag. 2019;186(1):462–472.

[4] Ipakchi O., Mosaffa A.H., Garousi Farshi L. Ejector based CO₂ transcritical combined cooling and power system utilizing waste heat recovery: A thermoeconomic assessment // Energy Convers. Manag. 2019. Vol. 186, N. 1. P. 462–472.

[5] Besagni G, Mereu R, Inzoli F. Ejector refrigeration: A comprehensive review. Renew. Sustain. Energy Rev. 2016;53(1):373–407.

[6] 3. Besagni G., Mereu R., Inzoli F. Ejector refrigeration: A comprehensive review // Renew. Sustain. Energy Rev. 2016. Vol. 53, N. 1. P. 373–407.

[7] Aidoun Z, Ameur K, Falsafioon M, Badache M. Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 1: Single-Phase Ejectors. Inventions. 2019;4(1):15.

[8] Aidoun Z., Ameur K., Falsafioon M., Badache M. Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 1: Single-Phase Ejectors // Inventions. 2019. Vol. 4, N. 1. P. 15.

[9] Aidoun Z, Ameur K, Falsafioon M, Badache M. Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors. Inventions. 2019;4(1):16.

[10] Aidoun Z., Ameur K., Falsafioon M., Badache M. Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors // Inventions. 2019. Vol. 4, N. 1. P. 16.

[11] Tashtoush BM, Al-Nimr MA, Khasawneh MA. A comprehensive review of ejector design, performance, and applications. Appl. Energy. 2019;240(1):138–172.

[12] Tashtoush B.M., Al-Nimr M.A., Khasawneh M.A. A comprehensive review of ejector design, performance, and applications // Appl. Energy. 2019. Vol. 240, N. 1. P. 138–172.

[13] Elbel S, Hrnjak P. Experimental validation of a prototype ejector designed to reduce throttling losses encountered in transcritical R744 system operation. Int. J. Refrig. 2008;31(3):411–422.

[14] Elbel S., Hrnjak P. Experimental validation of a prototype ejector designed to reduce throttling losses encountered in transcritical R744 system operation // Int. J. Refrig. 2008. Vol. 31, N. 3. P. 411–422.

[15] Taslimi Taleghani S, Sorin M, Poncet S. Modeling of two-phase transcritical CO₂ ejectors for on-design and off-design conditions. Int. J. Refrig. 2018;87(1):91–105.

[16] Taslimi Taleghani S., Sorin M., Poncet S. Modeling of two-phase transcritical CO₂ ejectors for on-design and off-design conditions // Int. J. Refrig. 2018. Vol. 87, N. 1. P. 91–105.

[17] Metsue A, Debroeyer R, Poncet S, Bartosiewicz Y. An improved thermodynamic model for supersonic real-gas ejectors using the compound-choking theory. Energy. 2021. (In Print).

[18] Metsue A., Debroeyer R., Poncet S., Bartosiewicz Y. An improved thermodynamic model for supersonic real-gas ejectors using the compound-choking theory // Energy. 2021. (In Print).

[19] Chen Y, Chen Z, Chen Z, Yuan X. Dynamic modeling of solarassisted ground source heat pump using Modelica. Appl. Therm. Eng. 2021;196(1):117324.

[20] Chen Y., Chen Z., Chen Z., Yuan X. Dynamic modeling of solarassisted ground source heat pump using Modelica // Appl. Therm. Eng. 2021. Vol. 196, N. 1. P. 117324.

[21] Liu F, Qiu W, Deng J, et al. Multi-objective nonsimultaneous dynamic optimal control for an ejector expansion heat pump with thermal storages. Appl. Therm. Eng. 2020;168(1):114835.

[22] Liu F., Qiu W., Deng J., et al. Multi-objective nonsimultaneous dynamic optimal control for an ejector expansion heat pump with thermal storages // Appl. Therm. Eng. 2020. Vol. 168, N. 1. P. 114835.

[23] Hafner A, Försterling S, Banasiak K. Multi-ejector concept for R-744 supermarket refrigeration. Int. J. Refrig. 2014;43(1):1–13.

[24] Hafner A., Försterling S., Banasiak K. Multi-ejector concept for R-744 supermarket refrigeration // Int. J. Refrig. 2014. Vol. 43, N. 1. P. 1–13.

[25] Liu F, Deng J, Pan W. Model-based Dynamic Optimal Control of an Ejector Expansion CO₂ Heat Pump Coupled with Thermal Storages. Energy Procedia. 2018;152(1):156–161.

[26] Liu F., Deng J., Pan W. Model-based Dynamic Optimal Control of an Ejector Expansion CO₂ Heat Pump Coupled with Thermal Storages // Energy Procedia. 2018. Vol. 152, N. 1. P. 156–161.

[27] Zhu Y, Li C, Zhang F, Jiang P-X. Comprehensive experimental study on a transcritical CO₂ ejector-expansion refrigeration system. Energy Convers. Manag. 2017;151(1):98–106.

[28] Zhu Y., Li C., Zhang F., Jiang P.-X. Comprehensive experimental study on a transcritical CO₂ ejector-expansion refrigeration system // Energy Convers. Manag. 2017. Vol. 151, N. 1. P. 98–106.

RIGHTS & PERMISSIONS

Eco-Vector