Working fluid selection for heat pumps in solar district heating systems

Xiao, Shengqing; Nefodov, Dimitri; McLinden, Mark O.; Richter, Markus; Urbaneck, Thorsten

doi:10.1016/j.solener.2022.02.036

Cited by 7 publications

(4 citation statements)

References 20 publications

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“…The parachor was determined from the ancillary equation for the saturated density (Akasaka et al, 15 ) above 300 K and the measured surface tension data. (7) where θ = 1 − T/T crit . The coefficients in the equation are n 1 = 2.1958, n 2 = 6.4706, n 3 = −13.191, and n 4 = 7.7906.…”

Section: Journal Ofmentioning

confidence: 99%

“…Furthermore, physical property, performance, and safety assessments are currently being conducted, including for mixtures with stable substances. HFO-based substances R1336mzz(E) and R1336mzz(Z), which are cis- and trans-1,1,1,4,4,4-hexa-fluoro-butene, respectively, have relatively high boiling points and can be utilized in waste heat recovery systems and solar–thermal systems , or mixed with other refrigerants to reduce the GWP . In addition, the problem of perfluoroalkyl and polyfluoroalkyl substances (PFAS)/perfluorooctanesulfonic acid (PFOS) has been highlighted; however, it is not currently classified as a controlled substance.…”

Section: Introductionmentioning

confidence: 99%

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Surface Tension and Parachor of cis- and trans-1,1,1,4,4,4-Hexafluorobutene [R-1336mzz(Z) and R-1336mzz(E)]

Kawahara,

Kondou,

Iwasaki

2023

J. Chem. Eng. Data

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R1336mzz(Z) and R1336mzz(E), which are cis- and trans-1,1,1,4,4,4-hexa-fluoro-butene, respectively, can be utilized in waste heat recovery systems and solar–thermal systems or mixed with other refrigerants to reduce the global warming potential. This paper presents surface tensions of R1336mzz(Z) and R1336mz(E) in the temperature range of 228–383 K, obtained using a differential capillary rise method. The measurement uncertainty ranges from 0.10 to 0.44 mN m–1 (k = 2). When the R1336mzz(E) data are reduced, the temperature dependence of the parachor is indicated below 300 K, which is the range where saturation density measurements have not been reported. Therefore, the saturation density below 300 K is modified, and the surface tension data are reobtained. Based on the measured surface tension, the empirical correlations for R1336mzz(Z) and R1336mzz(E) are σ = 54.29 (1 – T/T crit)1.26 and σ = 55.47 (1 – T/T crit)1.27, respectively, where T crit is the critical temperature, that is, 444.5 and 403.53 K. Additionally, the substance-specific parameter parachors are determined to be 231.2 and 221.7 for R1336mzz(Z) and R1336mzz(E), respectively.

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Section: Journal Ofmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Surface Tension and Parachor of cis- and trans-1,1,1,4,4,4-Hexafluorobutene [R-1336mzz(Z) and R-1336mzz(E)]

Kawahara,

Kondou,

Iwasaki

2023

J. Chem. Eng. Data

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“…[9,[22][23][24] Other studies introduce process and refrigerant dependency using empirical correlations for the isentropic efficiency. [7,20,25] However, these empirical correlations are fit to data for only a few refrigerants, and refrigerant extrapolation is neither guaranteed nor proven.…”

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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“…In order to meet the net-zero objective, it is crucial to decarbonize also the heating sector through the massive diffusion of heat pumps systems driven by energy from renewable sources or nuclear. A key role to achieve this objective can be played by district heat pump systems, allowing the use of different heat sources with different plant solutions [3] and working fluids [4].…”

Section: Introductionmentioning

confidence: 99%

Ammonia heat pumps for district heating: thermo-economic optimization analysis based on evaporator geometry for either direct expansion or chilled water configurations

Passarelli,

Viscito,

Merlo

et al. 2023

J. Phys.: Conf. Ser.

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Electric heat pumps are recognized as a key technology for decarbonization and have received increasing policy support in several countries over the last few years. These devices offer a highly efficient form of electric heating and could make an important contribution to the transition to a low carbon future, especially in case of district heating systems. Within this context, this paper presents a thermo-economic optimization analysis of a 7.35 MW electric heat pump system employed for district heating purposes and using ammonia as working fluid. The implemented code gathers multiple sub-models calibrated ad-hoc from real data or manufacturers’ datasheets. The heat exchangers are simulated by considering phenomenological equations and well-known heat transfer coefficient and pressure drop prediction methods. The optimization analysis is performed at constant condensation temperature that guarantees in/out hot water temperatures of 30/62 °C and is focused on the matching between compressor and evaporator heat exchanger, by considering either a direct expansion system or a chilled water heat pump. Both the coefficient of performance (COP) and the set-up costs are considered as optimization performance indicators for the construction of the Pareto front.

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Working fluid selection for heat pumps in solar district heating systems

Cited by 7 publications

References 20 publications

Surface Tension and Parachor of cis- and trans-1,1,1,4,4,4-Hexafluorobutene [R-1336mzz(Z) and R-1336mzz(E)]

Surface Tension and Parachor of cis- and trans-1,1,1,4,4,4-Hexafluorobutene [R-1336mzz(Z) and R-1336mzz(E)]

Refrigerant Selection for Heat Pumps: The Compressor Makes the Difference

Ammonia heat pumps for district heating: thermo-economic optimization analysis based on evaporator geometry for either direct expansion or chilled water configurations

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