Fluid Retrofit for Existing Vapor Compression Refrigeration Systems and Heat Pumps: Evaluation of Different Models

Roskosch, Dennis; Venzik, Valerius; Atakan, Burak

doi:10.3390/en12122417

Cited by 3 publications

(3 citation statements)

References 14 publications

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“…The modeling approach used is based on established methods for heat pump calculations and was shown to be appropriate to analyze the relative performance of refrigerants. [ 45 ]…”

Section: Numerical Modelingmentioning

confidence: 99%

“…The modeling approach used is based on established methods for heat pump calculations and was shown to be appropriate to analyze the relative performance of refrigerants. [45] In the following sections, we briefly summarize the differences between the process parameters, which are degrees of freedom and the definition of the COP.…”

Section: Investigated Flowsheetsmentioning

confidence: 99%

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Investigation of the Interactions between Refrigerant, Flowsheet, and Compressor in Residential Heat Pumps

et al. 2023

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The refrigerant used in heat pumps significantly influences the overall system performance. However, selecting a proper refrigerant is no trivial matter due to the heat pumps’ sensitivity to the selected flowsheet, components, and operating conditions. Herein, a holistic approach is used that covers all these interdependencies simultaneously considering the flowsheet, fluid‐dependent compressor efficiencies, and the operating point. Six low global warming potential (GWP<150) refrigerants are investigated, which include pure fluids, azeotropic mixtures, and zeotropic mixtures from different substance groups. For four flowsheets, the seasonal coefficient of performance (SCOP) by EN 14825 is calculated and serves as the assessment metric. The case study is based on typical conditions of residential heat pumps. The results show that the SCOPs substantially differ depending on the refrigerant and the flowsheet (reaching from 3.8 to 4.6). Differences in the performance of refrigerants for an equal flowsheet are mainly driven by compressor efficiency. However, these differences can be overcome by adjusting the flowsheet. In particular, when an internal heat exchanger is added, the refrigerant ranking is substantially changed. It is shown that R436A, which is inferior to R290 for the basic cycle, benefits more from an internal heat exchanger and reaches a competitive SCOP than R290.

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“…The modeling approach used is based on established methods for heat pump calculations and was shown to be appropriate to analyze the relative performance of refrigerants. [ 45 ]…”

Section: Numerical Modelingmentioning

confidence: 99%

Section: Investigated Flowsheetsmentioning

confidence: 99%

Investigation of the Interactions between Refrigerant, Flowsheet, and Compressor in Residential Heat Pumps

et al. 2023

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“…[16] Evaluating refrigerant candidates with regard to their economic or thermodynamic performance requires a process model of the heat pump. Within the process model, an increasing degree of detail improves the prediction quality [17] but also the computational effort for the evaluation. However, the goal of refrigerant selection is not to predict the heat pump performance quantitatively but to accurately identify the optimal refrigerants.…”

Section: Introductionmentioning

confidence: 99%

Refrigerant Selection for Heat Pumps: The Compressor Makes the Difference

et al. 2023

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Increasingly stringent regulations and new applications require selecting improved refrigerants for heat pumps. The selected refrigerants should be environmentally friendly and maximize the performance of the heat pump process. Systematic refrigerant selection methods usually model the compressor with one fixed isentropic efficiency identical for all refrigerants. However, compressor studies indicate that the isentropic efficiency may be highly refrigerant‐dependent. Herein, the need for a refrigerant‐dependent compressor model for refrigerant selection is investigated. For this purpose, a refrigerant‐dependent compressor model is combined with an integrated design of refrigerant and heat pump process. To guarantee a comparable nominal heating power among refrigerants, the compressor design is tailored to the refrigerant by expanding the refrigerant‐dependent compressor model toward compressor sizing. Integrating compressor design into systematic refrigerant selection is enabled by a computationally efficient model implementation. Accounting for refrigerant‐dependent compression substantially changes the resulting refrigerant ranking compared to the widely used assumption of identical isentropic efficiencies for all refrigerants: The best‐performing refrigerant is not even identified among the best ten refrigerants when assuming identical isentropic efficiencies. Consequently, compression is identified as the main driver for differences in refrigerant performance. Therefore, integrating refrigerant‐dependent compressor models is crucial for systematic refrigerant selection.

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A Study on Adapted Similitude Modeling Method of Turboexpander With Different Gas Working Fluids

Wang

Zhang

et al. 2021

Journal of Engineering for Gas Turbines and Power

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The study on similitude modeling method of turboexpander with different working fluids is not only the key technical means and necessary method for the research and development of turboexpander with special working fluids, but also an effective way to further expand the application scope of turboexpander. In this paper, a new similitude modeling method (NSMM), which is based on dimensional analysis, actual characteristics of real gas and seven similitude criteria, is proposed. On the basis of modeling criterion p4, the new similitude relationship of turboexpander with different gas working fluids is obtained based on rotational speed, inlet total temperature, specific heat ratio and gas constant. Aiming at NSMM, the similitude modeling performance of turboexpander with air, methane, CO2 and helium is verified by using Computational Fluid Dynamics method. The results show that the modeling effects on aerodynamic performance are well predicted in a wide range including the design point (expansion ratio 2.9~5.0), and the errors of the total-to-total isentropic efficiency, relative equivalent mass flow rate, relative equivalent shaft power are less than 0.74%, 1.94% and 1.69%, respectively. Methane and CO2 have the best modeling performance, their errors of efficiency, relative equivalent mass flow rate and relative equivalent shaft power are all less than 0.5%; Furthermore, the NSMM also has pinpoint accuracy with the prediction of internal flow field, which provides a good idea for further research on special working fluid turboexpander and an approach to expand the application scope of turboexpanders.

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Fluid Retrofit for Existing Vapor Compression Refrigeration Systems and Heat Pumps: Evaluation of Different Models

Cited by 3 publications

References 14 publications

Investigation of the Interactions between Refrigerant, Flowsheet, and Compressor in Residential Heat Pumps

Investigation of the Interactions between Refrigerant, Flowsheet, and Compressor in Residential Heat Pumps

Refrigerant Selection for Heat Pumps: The Compressor Makes the Difference

A Study on Adapted Similitude Modeling Method of Turboexpander With Different Gas Working Fluids

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