Experimental investigation of a novel expansion device control mechanism: Vortex control of initially subcooled flashing R134a flow expanded through convergent-divergent nozzles

Zhu, Jingwei; Elbel, Stefan

doi:10.1016/j.ijrefrig.2017.09.023

Cited by 21 publications

(10 citation statements)

References 15 publications

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“…The results obtained highlighted that the mass flow rate can be decreased by 36% with the proposed control technique at the same inlet and outlet conditions. Zhu and Elbel (2018d) extended the previously mentioned work by including six other nozzle geometries relying on R134a. A maximum vortex control range of 42% was assessed.…”

Section: Adjustable Vortex-based Capacity Control Techniquementioning

confidence: 90%

“…The main findings related to the vortex-based capacity control strategy are summarized in Table 3. In accordance with them, it could be claimed that the nozzle restrictiveness can be suitably varied with the aid of the nozzle inlet vortex as well as that the capacity modulation is potentially wide enough to be considered for real applications (Zhu and Elbel, 2018d). In addition, according to the studies implemented by the authors of this concept, vortex ejectors are potentially suitable for smallcapacity applications, such as MAC units and air conditioners.…”

Section: Summary Of the Current Status On The Adjustable Vortex-basedmentioning

confidence: 94%

“…Main findings Zhu and Elbel (2016b) Experimental R134a vapourcompression system  At the inlet and outlet conditions, mass flow rate can be decreased by 36% Zhu and Elbel (2018d) Experimental R134a vapourcompression system  A maximum vortex control range of 42% was observed Experimental Transcritical R744 vapour-compression system for MAC applications  Motive inlet pressure could be varied between 86.09 bar and 96.37 bar for constant total motive mass flow rate and motive inlet temperature  Decrements in vortex ejector efficiency by about 47% from 0.187 to 0.099 with rise in vortex strength Zhu and Elbel (2020) Experimental Transcritical R744 vapour-compression system  System capacity and COP improvements by 11% and 8.1% under offdesign running modes, respectively. Table 4.…”

Section: Investigated Solutionmentioning

confidence: 94%

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A review on current status of capacity control techniques for two-phase ejectors

Gullo

Kærn

Haida

et al. 2020

International Journal of Refrigeration

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The adoption of highly efficient vapour-compression refrigeration, air conditioning and heat pump (RACHP) systems is compulsory to achieve a low-carbon society. Expansion work recovery using a two-phase ejector is widely recognized as one of the most promising measures to improve the energy efficiency of RACHP units. This holds true for all operation conditions provided that an effective capacity control technique is implemented. In this work a thorough critical review on the current status of the presently available capacity control techniques for two-phase ejectors was carried out. In addition, their pros and cons as well as the comparison of their performance were reported. It was concluded that two-phase ejectors can be properly capacity controlled in large-and medium-scale vapour-compression units. However, a suitable capacity control mechanism for small-scale vapour-compression solutions still requires a major breakthrough and is being intensively discussed among experts in the field.

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Section: Adjustable Vortex-based Capacity Control Techniquementioning

confidence: 90%

Section: Summary Of the Current Status On The Adjustable Vortex-basedmentioning

confidence: 94%

Section: Investigated Solutionmentioning

confidence: 94%

See 1 more Smart Citation

A review on current status of capacity control techniques for two-phase ejectors

Gullo

Kærn

Haida

et al. 2020

International Journal of Refrigeration

Self Cite

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“…Ejector using spindle to adjust the throat area of primary nozzle is a common solution to control the ejector performance across variable operating conditions [131]. Recently, Zhu and Elbel [132] experimentally tested a novel nozzle flow control mechanism called vortex control. Without changing the nozzle geometry, the authors showed that the strength of the nozzle inlet vortex could change the restrictiveness of the two-phase convergent-divergent nozzle with initially sub-cooled R134a.…”

Section: Experiments On Ejectorsmentioning

confidence: 99%

Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors

et al. 2019

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Two-phase ejectors play a major role as refrigerant expansion devices in vapor compression systems and can find potential applications in many other industrial processes. As a result, they have become a focus of attention for the last few decades from the scientific community, not only for the expansion work recovery in a wide range of refrigeration and heat pump cycles but also in industrial processes as entrainment and mixing enhancement agents. This review provides relevant findings and trends, characterizing the design, operation and performance of the two-phase ejector as a component. Effects of geometry, operating conditions and the main developments in terms of theoretical and experimental approaches, rating methods and applications are discussed in detail. Ejector expansion refrigeration cycles (EERC) as well as the related theoretical and experimental research are reported. New and other relevant cycle combinations proposed in the recent literature are organized under theoretical and experimental headings by refrigerant types and/or by chronology whenever appropriate and systematically commented. This review brings out the fact that theoretical ejector and cycle studies outnumber experimental investigations and data generation. More emerging numerical studies of two-phase ejectors are a positive step, which has to be further supported by more validation work.

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“…Choked flow in nozzles fed by liquid undergoes flashing, due mainly to rapid expansion pressure decrease [19] and wall friction (formation, growth and departure of bubbles) [20]. An interesting experimental study of Zhu and Elbel [21] investigated the effects of nozzle convergent-divergent length on the initially flashing flow of R134a. Under the same nozzle inlet and outlet conditions, a long convergent part may present two different mass flow rates.…”

Section: Introductionmentioning

confidence: 99%

Experimental Performance of a Two-Phase Ejector: Nozzle Geometry and Subcooling Effects

2020

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This paper presents the results of an experimental study on a two-phase ejector. The main objective is to assess the effects of the nozzle’s divergent and the throat diameter on performance under various working conditions. Under the same conditions, ejector operation with a convergent nozzle, results in higher critical primary mass flow rate and lower critical pressure than with a convergent-divergent nozzle version. Experiments show as well that the flow expansion is higher in the convergent-divergent nozzle. The throat diameter turns out to have an important impact only on the amount of the critical mass flow rate. The nozzle geometry has no impact on its optimal position in the ejector. Globally, the ejector with the convergent-divergent nozzle provides a higher entrainment ratio, due to a reduced primary mass flow rate and an increased secondary flow induction. Tests also show that the ejector with a lower throat diameter provides a higher entrainment ratio, due to better suction with less primary flow. Unlike the convergent-divergent nozzle, the convergent nozzle permits an entrainment ratio almost insensitive to a wide range of primary inlet sub-cooling levels. Primary and secondary mass flow rates increase proportionally with the subcooling level and result in a quasi-constant entrainment ratio.

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Experimental investigation of a novel expansion device control mechanism: Vortex control of initially subcooled flashing R134a flow expanded through convergent-divergent nozzles

Cited by 21 publications

References 15 publications

A review on current status of capacity control techniques for two-phase ejectors

A review on current status of capacity control techniques for two-phase ejectors

Current Advances in Ejector Modeling, Experimentation and Applications for Refrigeration and Heat Pumps. Part 2: Two-Phase Ejectors

Experimental Performance of a Two-Phase Ejector: Nozzle Geometry and Subcooling Effects

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