Influence of evaporating rate on two-phase expansion in the piston expander with cyclone separator

Wu, Weifeng; Wang, Qi; Zhang, Zhao; Wu, Zhijun; Yang, Xiaotian; Xu, Liangcong

doi:10.2298/tsci180903322w

Cited by 8 publications

(5 citation statements)

References 31 publications

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“…During expansion of a two-phase fluid, flashing will occur. Flashing [18,19] is a physical phenomenon in liquids. It represents a change from liquid to vapor as a result of a sudden decrease in the pressure below the saturation pressure.…”

Section: Principles Of Flashingmentioning

confidence: 99%

“…In volumetric expanders, this sudden depressurization is a result of the increasing working volume. Due to the shape of a reciprocating expander, the flashing process could be compared to static flash experiments [19]. Static flash stands for the case where the fluid remains static in the horizontal direction during the flashing process [39].…”

Section: Volumetric Expander Types For Two-phase Expansionmentioning

confidence: 99%

“…Ref. [19] also modeled a two-phase expander with a cyclone separator. The authors applied an evaporation model based on static flash pool evaporation and separated the phases in the cyclone and piston parts.…”

Section: Reciprocating Expandermentioning

confidence: 99%

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Two-Phase Volumetric Expanders: A Review of the State-of-the-Art

2022

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Two-phase expansion is the process where a fluid undergoes a pressure drop through or in the liquid–vapor dome. This operation was historically avoided. However, currently it is studied for a multitude of processes. Due to the volume increase in volumetric expanders, a pressure drop occurs in the fluid resulting in flashing phenomena occurring. These phenomena have been studied before in other processes such as two-phase flows or static flash. However, this has not been extensively studied in volumetric expanders and is mostly neglected. Even if data has shown this is not always neglectable depending on the expander type. The thermal non-equilibrium occurring can be modeled on different principles of flashing flows, such as the mixture model, boiling delay model, and homogeneous relaxation model. The main application area in current literature for volumetric two-phase expansion machines, is in low-temperature two-phase heat-to-power cycles. These cycles have shown benefit over classic options if expanders are available with efficiencies in the range of at least 75%. Experimental investigation of expanders in two-phase operation, though lacking in quantity, has shown that this is an achievable goal. However, the know-how to accomplish this requires more studies, both experimentally and in modeling techniques for the different phenomena occurring within these expanders. The present work provides a brief but comprehensive overview of the available experimental data, applicable flashing modeling techniques, and available models of volumetric two-phase expanders.

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Section: Principles Of Flashingmentioning

confidence: 99%

Section: Volumetric Expander Types For Two-phase Expansionmentioning

confidence: 99%

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Two-Phase Volumetric Expanders: A Review of the State-of-the-Art

2022

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“…Taniguchi et al [24] presented a numerical model to predict the performance of a two-phase flow screw expander. Wu et al [25] studied the trilateral flash cycle (TFC) by means of numerical modeling. In their research, the flash evaporating rate was introduced into a model of the two-phase expansion process in the reciprocating expander with a cyclone separator.…”

Section: Introductionmentioning

confidence: 99%

The Investigation of Two-Phase Expansion Performance with Indicator Diagram in a Twin-Screw Expander

Zhou

Zhu³

2023

Processes

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Volumetric expanders are proven to be more suitable for small-scale waste heat recovery applications because of their simplicity, reliability, lower rotational speed and lower cost. Unlike turbines, volumetric expanders can work in the two-phase fluid state, which broadens their application fields. To investigate the two-phase performance of volumetric expanders, a specific twin-screw expander was chosen and modeled. The leakage loss and the suction pressure loss were primary concerns in this research. The two-phase expansion process in the expander is presented in detail using the developed mathematical model with an indicator diagram. The influence of several factors, including inlet vapor quality, rotational speed and intake pressure, are investigated. The influence mechanism of the vapor phase and the liquid phase on expander performance is clarified. In brief, this paper presents an illustrative understanding of the two-phase expansion process in twin-screw expanders.

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“…Expander is a key device in a thermodynamic cycle. Sometimes the selection of expander will directly determine whether a thermodynamic cycle or process can be successfully realized [19]. Considering that ammonia-water is a binary mixture and the ammonia-rich vapor and ammonia-lean solution in the cycle are both at gas-liquid two-phase state, it is necessary to select an expander that can perform twophase expansion to replace the throttle valve for recovering energy loss due to the throttling in the path of ammonia-lean solution.…”

Section: Introductionmentioning

confidence: 99%

Modification of Kalina cycle system 34g by replacing throttle valve with single-screw expander

Zhang

2022

THERM SCI

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Recovery of the energy loss caused by throttling plays an important role in improving the performance of a cycle. Based on the original Kalina Cycle System 34g, two redesigned cycles, which have different placement of single-screw expanders used to replace the throttle valve, are proposed in this paper. The thermodynamic performance of two redesigned cycles is analyzed and compared with the original Kalina Cycle System 34g. The results show that the thermodynamic performance of each redesigned cycle is better than that of the original Kalina Cycle System 34g and the I?-redesigned cycle performs best. At a low and moderate evaporation pressure, there is an optimal ammonia-water concentration and it increases with the increase of evaporation pressure. With the concentration increases of ammonia-water, the performance advantage of the redesigned cycle system over the original Kalina Cycle System 34g gradually decreases. When the ammonia-water concentration is much lower than the optimal concentration, the single-screw expander produces much work and plays a positive role in net work output of cycle system. The highest cycle exergy efficiency of 54.14% can be obtained in the II-redesigned cycle when the evaporation pressure is 3.0MPa and ammonia-water concentration is 0.85.

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Influence of evaporating rate on two-phase expansion in the piston expander with cyclone separator

Cited by 8 publications

References 31 publications

Two-Phase Volumetric Expanders: A Review of the State-of-the-Art

Two-Phase Volumetric Expanders: A Review of the State-of-the-Art

The Investigation of Two-Phase Expansion Performance with Indicator Diagram in a Twin-Screw Expander

Modification of Kalina cycle system 34g by replacing throttle valve with single-screw expander

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