A Simple Design Approach of Two-Phase Ejectors for CO2 Transcritical Heat Pumps

Ameur, K.; Aidoun, Z.

doi:10.47176/jafm.16.10.1833

A Simple Design Approach of Two-Phase Ejectors for CO2 Transcritical Heat Pumps

Document Type : Regular Article

Authors

CanmetENERGY, Natural Resources Canada, Varennes, Qc, J3X1S6, Canada

10.47176/jafm.16.10.1833

Abstract

Integrating a two-phase ejector in mechanical vapor compression heat pumps is a practical and low-cost solution for improving performance and reducing energy consumption. Typically, using an ejector to recover part of the important pressure expansion losses in CO₂ systems may improve the operating conditions of the compressor. One of the prerequisites for the success of such an application is the proper design of the ejector. This study is mainly dedicated to developing a simple approach for CO₂ ejector design. The advantage of using the ejector as an expander in a transcritical CO₂ heat pump is first introduced. Compressor operation is particularly improved. The development of an ejector design model for CO₂ expanding from transcritical to two-phase conditions is presented. Validation of the thermodynamic model with experimental results from the literature shows the predictions to be within an acceptable range of discrepancy. The primary nozzle throat diameter calculations do not exceed ±8% of error for transcritical conditions. The error of the predicted pressure at the outlet of the ejector is in the limit of -15% to +3%. A practical design example for estimating the transcritical CO₂ ejectors geometry integrated in a heat pump is presented. The results show the important decrease of primary nozzle diameters with the drop of T_evap, especially for the throat. A decrease of D_mix also occurs with T_evap and an optimal diameter is obtained for each condition considered. The design of the diffuser is based on a compromise between the outlet velocity and the length of the diffuser. The detailed design procedure with the proposed model, complemented with data from the literature, is a valuable tool for rapidly generating useful results and obtaining preliminary designs transcritical CO₂ ejector.

Keywords

Main Subjects

Compressible Flows

References

Aakenes, F. (2012). Frictional pressure-drop models for steady-state and transient two-phase flow of carbon dioxide. [Master’s thesis, Norwegian University of Science and Technology].##

Aidoun, Z., Ameur, K., Falsafioon, M., & Badache, M. (2019a). Current advances in ejector modeling, experimentation and applications for refrigeration and heat pumps. Part 2: Two-phase ejectors. Inventions, 4, 1–54. https://doi.org/10.3390/inventions4010016##

Aidoun, Z., Ameur, K., Falsafioon, M., & Badache, M. (2019b). Current advances in ejector modeling, experimentation and applications for refrigeration and heat pumps. Part 1: Single-phase ejectors. Inventions, 4, 1–73. https://doi.org/10.3390/inventions4010016##

Akagi, S., Dang, C., & Hihara, E. (2008). Characteristics of pressure recovery in two-phase ejector applied to carbon dioxide heat pump cycle. 9th International IEA Heat Pump Conference, Zürich, Switzerland.##

Akagi, S., Wang, J., & Hihara, E., 2004. Characteristics of two-phase ejector with carbon dioxide. 41st National Heat Transfer Symposium of Japan.##

Ameur, K., & Aidoun, Z. (2021). Two-phase ejector enhanced carbon dioxide transcritical heat pump for cold climate. Energy Conversion and Management, 243, 114421. https://doi.org/10.1016/j.enconman.2021.114421##

Ameur, K., Aidoun, Z., & Ouzzane, M. (2016). Modeling and numerical approach for the design and operation of two-phase ejectors. Applied Thermal Engineering 109, 809–818. https://doi.org/10.1016/j.applthermaleng.2014.11.022##

Austin, B. T., & Sumathy, K. (2011). Transcritical carbon dioxide heat pump systems: A review. Renewable and Sustainable Energy Reviews 15, 4013–4029. https://doi.org/10.1016/j.rser.2011.07.021##

Banasiak, K., & Hafner, A. (2011). 1D Computational model of a two-phase R744 ejector for expansion work recovery. International Journal of Thermal Sciences 50, 2235–2247. https://doi.org/10.1016/j.ijthermalsci.2011.06.007##

Banasiak, K., & Hafner, A. (2013). Mathematical modelling of supersonic two-phase R744 flows through converging-diverging nozzles : The effects of phase transition models. Applied Thermal Engineering 51, 635–643. https://doi.org/10.1016/j.applthermaleng.2012.10.005##

Banasiak, K., Hafner, A., & Andresen, T. (2012). Experimental and numerical investigation of the influence of the two-phase ejector geometry on the performance of the R744 heat pump. International Journal of Refrigeration 35, 1617–1625. https://doi.org/10.1016/j.ijrefrig.2012.04.012##

Banasiak, K., Hafner, A., Kriezi, E. E., Madsen, K. B., Birkelund, M., Fredslund, K., & Olsson, R. (2015). Development and performance mapping of a multi-ejector expansion work recovery pack for R744 vapour compression units. International Journal of Refrigeration 57, 265–276. https://doi.org/10.1016/j.ijrefrig.2015.05.016##

Banasiak, K., Palacz, M., Hafner, A., Bulinski, Z., Smołka, J., Nowak, A. J., & Fic, A. (2014). A CFD-based investigation of the energy performance of two-phase R744 ejectors to recover the expansion work in refrigeration systems : An irreversibility analysis. International Journal of Refrigeration 40, 328–337. https://doi.org/10.1016/j.ijrefrig.2013.12.002##

Besagni, G., Mereu, R., & Inzoli, F. (2016). Ejector refrigeration: A comprehensive review. Renewable and Sustainable Energy Reviews 53, 373–407. https://doi.org/https://doi.org/10.1016/j.rser.2015.08.059##

Bouziane, A., Bensafi, A., & Haberschill, P. (2012). Modeling and experimental study of an ejector for a transcritical co2 refrigeration system. 10 Th IIR Gustav Lorentzen Conference on Natural Refrigerants. Delft, The Netherlands.##

Cardemil, J., & Colle, S. 2011. Novel cascade ejector cycle using natural refrigerants. 23rd IIR International Congress of Refrigeration. Prague, Czech Republic.##

Eames, I., Aphornratana, S., & Haider, H. (1995). A theoretical and experimental study of a small-scale steam jet refrigerator. International Journal of Refrigeration 18, 378–386. https://doi.org/10.1016/0140-7007(95)98160-M##

Elbel, S. (2011). Historical and present developments of ejector refrigeration systems with emphasis on transcritical carbon dioxide air-conditioning applications. International Journal of Refrigeration 34, 1545–1561. https://doi.org/10.1016/j.ijrefrig.2010.11.011##

Elbel, S., & Hrnjak, P. (2008). Experimental validation of a prototype ejector designed to reduce throttling losses encountered in transcritical R744 system operation. International Journal of Refrigeration 31, 411–422. https://doi.org/10.1016/j.ijrefrig.2007.07.013##

Environment and Climate Change Canada (2022) Canadian Environmental Sustainability Indicators: Greenhouse gas emissions. Gatineau, Canada.##

Giacomelli, F., Mazzelli, F., Banasiak, K., Hafner, A., & Milazzo, A. (2019). Experimental and computational analysis of a R744 flashing ejector. International Journal of Refrigeration 107, 326–343. https://doi.org/10.1016/j.ijrefrig.2019.08.007##

Henry, R. E., & Fauske, H. K. (1971). The two-phase critical flow of one-component mixtures in nozzles, orifice, and short tubes. Journal of Heat Transfer, 93, 179–187. https://doi.org/10.1115/1.3449782##

Huff, H. J., & Radermacher, R. (2003). CO2 compressor-expander analysis. ARTI-21CR/611-10060-01. Arlington.##

Kornhauser, A. A. (1990). The Use of an ejector as a refrigerant expander. International Refrigeration and Air Conditioning Conference. Purdue University. Paper 82.##

Lee, J. S., Kim, M. S. Kim, & M. S. Kim (2011). Experimental study on the improvement of CO2 air conditioning system performance using an ejector. International Journal of Refrigeration 34, 1614–1625. https://doi.org/10.1016/j.ijrefrig.2010.07.025##

Li, D., & Groll, E. A. (2006). Analysis of an ejector expansion device in a transcritical CO2 air conditioning system. 7th IIR Gustav Lorentzen Conference on Natural Working Fluids. Trondheim, Norway.##

Liu, F., Groll, E. A., & Li, D. (2012a). Investigation on performance of variable geometry ejectors for CO2 refrigeration cycles. Energy, 45, 829–839. https://doi.org/10.1016/j.energy.2012.07.008##

Liu, F., Li, Y., & Groll, E. A. (2012b). Performance enhancement of CO2 air conditioner with a controllable ejector. International Journal of Refrigeration 35, 1604–1616. https://doi.org/10.1016/j.ijrefrig.2012.05.005##

Lucas, C., & Koehler, J. (2012). Experimental investigation of the COP improvement of a refrigeration cycle by use of an ejector. International Journal of Refrigeration 35, 1595–1603. https://doi.org/10.1016/j.ijrefrig.2012.05.010##

Ma, Y., Liu, Z., & Tian, H. (2013). A review of transcritical carbon dioxide heat pump and refrigeration cycles. Energy, 55, 156–172. https://doi.org/10.1016/j.energy.2013.03.030##

Mastrowski, M., Smolka, J., Hafner, A., Haida, M., Palacz, M., & Banasiak, K. (2019). Experimental study of the heat transfer problem in expansion devices in CO2 refrigeration systems. Energy, 173, 586–597. https://doi.org/10.1016/j.energy.2019.02.097##

Minetto, S., Brignoli, R., Banasiak, K., Hafner, A., & Tesser, F. (2012). Experimental analysis of a r744 heat pump equipped with an ejector. The 10 Th IIR Gustav Lorentzen Conference on Natural Refrigerants. Delft, The Netherlands.##

Nakagawa, M., Marasigan, A. R., Matsukawa, T., & Kurashina, A. (2011). Experimental investigation on the effect of mixing length on the performance of two-phase ejector for CO2 refrigeration cycle with and without heat exchanger. International Journal of Refrigeration 34, 1604–1613. https://doi.org/10.1016/j.ijrefrig.2010.07.021##

NIST (2010). NIST thermodynamics and transport properties of refrigerants and refrigerant mixtures-REFPROP (Version 9.0).##

Palacz, M., Haida, M., Smolka, J., Nowak, A. J., Banasiak, K., & Hafner, A. (2017). HEM and HRM accuracy comparison for the simulation of CO2 expansion in two-phase ejectors for supermarket refrigeration systems. Applied Thermal Engineering 115, 160–169. https://doi.org/10.1016/j.applthermaleng.2016.12.122##

Ringstad, K. E., Allouche, Y., Gullo, P., Ervik, Å., Banasiak, K., & Hafner, A. (2020). A detailed review on CO2 two-phase ejector flow modeling. Thermal Science and Engineering Progress 20. https://doi.org/10.1016/j.tsep.2020.100647##

Rony, R. U., Yang, H., Krishnan, S., & Song, J. (2019). Recent advances in transcritical CO2 (R744) heat pump system: A review. Energies, 12, 1–35. https://doi.org/10.3390/en12030457##

Saeed, M. Z., Hafner, A., Thatte, A., & Gabrielii, C. H. (2022, June 13-15). Simultaneous implementation of rotary pressure exchanger and ejectors for CO2 refrigeration system. 15th IIR-Gustav Lorentzen Conference on Natural Refrigerants. Trondheim, Norway.##

Sarkar, J. (2010). Review on cycle modifications of transcritical CO2 refrigeration and heat pump systems. Journal of Advanced Research in Mechanical Engineering 1, 22–29.##

Smolka, J., Bulinski, Z., Fic, A., Nowak, A. J., Banasiak, K., & Hafner, A. (2013). A computational model of a transcritical R744 ejector based on a homogeneous real fluid approach. Applied Mathematical Modelling 37(3), 1208–1224. https://doi.org/10.1016/j.apm.2012.03.044##

Takleh, H. R., & Zare, V. (2019). Performance improvement of ejector expansion refrigeration cycles employing a booster compressor using different refrigerants: Thermodynamic analysis and optimization. International Journal of Refrigeration 101, 56–70. https://doi.org/10.1016/j.ijrefrig.2019.02.031##

Taslimi Taleghani, S., Sorin, M., & Poncet, S. (2018). Modeling of two-phase transcritical CO2 ejectors for on-design and off-design conditions. International Journal of Refrigeration 87, 91–105. https://doi.org/10.1016/j.ijrefrig.2017.10.025##

Zha, S., Jakobsen, A., Hafner, A., & Neksa, P. (2007). Design and parametric investigation on ejector for R-744 transcritical system. International Congress of Refrigeration 2007. Beijing.##

Zhu, Y., & Jiang, P. (2018). Theoretical model of transcritical CO2 ejector with non-equilibrium phase change correlation. International Journal of Refrigeration 86, 218–227. https://doi.org/10.1016/j.ijrefrig.2017.10.033##

Zhu, Y., Li, C., Zhang, F., & Jiang, P. X. (2017). Comprehensive experimental study on a transcritical CO2 ejector-expansion refrigeration system. Energy Conversion and Management 151, 98–106. https://doi.org/10.1016/j.enconman.2017.08.061##