Development of the free piston expander for work recovery in transcritical CO<sub>2</sub> refrigeration cycle

Peng, Xin; Zhang, B; Guo, Baolin; Xing, Ziwen; Shu, Pengcheng

doi:10.1243/09576509jpe202

Cited by 10 publications

(8 citation statements)

References 2 publications

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“…Peng et al. 3 developed a free piston expander coupled with an auxiliary compressor to consume the recovered work for transcritical CO 2 refrigeration cycle, the feasibility of the prototype was validated through compressed air and CO 2 . Nickl et al.…”

Section: Introductionmentioning

confidence: 99%

“…The results showed that the expander without modifying the geometric parameters of the original compressor performed better than the modified one, and the maximum recorded volumetric efficiency and isentropic efficiency were 68% and 42%, respectively. Peng et al 3 developed a free piston expander coupled with an auxiliary compressor to consume the recovered work for transcritical CO 2 refrigeration cycle, the feasibility of the prototype was validated through compressed air and CO 2 . Nickl et al 4 have developed three generations of piston expander-compressor unit for CO 2 refrigeration systems since 1994.…”

Section: Introductionmentioning

confidence: 99%

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Comparison between modeling and experiments on a two-stage rotary vane expander for an HFC-410A air conditioning system

Wang

Cao

Zhao

et al. 2013

Proceedings of the Institution of Mechanical Engineers, Part A:

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Substituting throttle valve with expander can effectively enhance the performance of a refrigeration system. A novel rotary vane expander with two-stage internal expansion was developed for HFC-410A air conditioning system. The structural characteristics and operating principle of the expander are presented. A simulation model including thermodynamic and dynamic calculations is established. An HFC-410A air conditioning system was built for the purposes of testing the prototype and verifying the model. Through the experimental results, the maximum volumetric efficiency was 55% at 1800 r/min and the maximum isentropic efficiency of the prototype was 31.5% at 1404 r/min. The maximum improvement in the system coefficient of performance was 10.3% at 1404 r/min, in comparison with the coefficient of performance without the expander. Higher rotational speed could reduce leakage time thus improve volumetric efficiency; however, it also generated more frictional loss that eventually deteriorated the expander performance. Properly increasing the condensation pressure could help reducing frictional loss at high speed, thus further improve the overall performance of the expander. The results also show that the expander has a better adaptability to variable operating conditions at high rotational speed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Comparison between modeling and experiments on a two-stage rotary vane expander for an HFC-410A air conditioning system

Wang

Cao

Zhao

et al. 2013

Proceedings of the Institution of Mechanical Engineers, Part A:

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show abstract

“…However, the complexity of components-especially the control mechanism-puts it at a disadvantage in the area of domestic refrigeration systems. Although a free-piston expander with simple active inlet/outlet control is promising for application in the transcritical CO 2 cycle (Peng et al 2006), the volumetric expansion ratio of HCFCs/HFCs is larger than that of CO 2 and, thus, the expander is enlarged. A screw expander has the function of energy recovery in the refrigeration system, but the requirement of high precision in fabrication and high cost make this expander less attractive for use in domestic systems.…”

Section: Introductionmentioning

confidence: 99%

An Experimental Study on Energy Recovery by a Pelton-Type Expander in a Domestic Refrigeration System

He¹,

Xia²,

Zhao³

et al. 2009

HVAC&R Research

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A Pelton-type two-phase expander was developed to replace the throttling valve for energy recovery in a domestic vapor-compression refrigeration system. The Pelton-type expander was designed and fabricated based on thermodynamic and mathematical analysis. It consists of two Laval nozzles and one simplified twin-arc blade impeller. A combined expander-generator prototype was validated in a R-410A domestic refrigeration system and demonstrated a stable operation within a wide speed range of up to 26,500 rpm. Experimental results showed the feasibility of integrating the Pelton-type expander into a domestic refrigeration system. A maximum isentropic efficiency of 32.8% was achieved under the experimental conditions. The relationships between the recovery work, the expander efficiency, and the impeller rotational speed were investigated. The results indicated that the velocity ratio was around 0.17 when the recovery work achieved the maximum value. The results also showed that the increase in the cooling capacity by 6.5% and the coefficient of performance (COP) by 5.4% could be obtained under the testing conditions.

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“…Because of this, some of the compressor designs which are available have been modified to be used as expanders. For example, the reciprocating piston [65][66][67][68][69][70], rotary vane [71,72], rolling piston [73][74][75][76], revolving vane [56,[77][78][79][80], screw [81][82][83][84][85] and scroll [86][87][88][89][90][91] have all been modified to be used as expanders.…”

Section: Evolution Of Refrigerantsmentioning

confidence: 99%

“…This is not common for compressors that usually avoid wet compression because the presence of liquid droplets can damage the compressor [93]. Secondly, some expander types (e.g., reciprocating piston, rolling piston and revolving vane) require externally controlled valves such as solenoid valves [65], electronically activated valves [5] or mechanically activated valves [67,74,94] at the inlet to control the beginning and ending of the suction process. And lastly, expanders must be able to handle sealing, lubrication, liquid slugging, cavitation, vibration and noise control problems which may affect the performance of the expander [95].…”

Section: Expanders In Air-conditioning Heating and Other Applicationsmentioning

confidence: 99%

Development of an energy-efficient expander-compressor unit for refrigeration systems

Yap¹

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The thesis presents the development of a novel expander-compressor unit, named cross vane expander-compressor, or in short CVEC. This device is conceived with the primary motivation of integrating the function of the expander and compressor into a single simple geometry, making energy recovery and efficiency improvement economically practical.Mathematical models have been formulated in this project to facilitate the understanding of the working physics in the 'expander' and 'compressor' of the CVEC. These include volume variations of the working chambers, kinematics of the mechanism, variation of thermodynamics properties of the working fluid, mass flow through suction and discharge ports, the response of the valve reed to pressure and centrifugal forces, the internal leakage of the working fluid through the gaps of the mating components within and across the chambers of the 'expander' and the 'compressor' and the mechanical losses of the machine. An attempt has also been made to analyse the heat transfer of the machine, following which Second Law analysis was carried out to quantify the exergy losses.Theoretical studies were carried out with R-1234yf as the working fluid, operating at the condensing and evaporating temperatures of 54.4°C and 7.2°C, respectively. The results show that through the use of CVEC, the system's COP was improved by 29.5% and the peak power input was reduced by 6.5% at 3000 rpm. The study also reveals that machines with a slender configuration or that with a lower rotating inertia would result in a higher mechanical efficiency. The highest mechanical efficiency of the machine was predicted to be 85.1% at slender ratio of 6.28 (i.e. expander-compressor length of 151.0 mm and outer cylinder radius of 24.1 mm).Additionally, it was found that the major internal leakage occurs through the split bush clearances with 74.1% of the total leakage. This leakage is the main reason behind the drop in pressure in the expansion chamber of the expander and compression chamber of the compressor. The results also show that major mechanical loss is caused by the end-face friction which accounts for 61.9% of the total losses.A prototype has been designed, fabricated and instrumented in an open-loop air-flow system.Tests were conducted from 600 to 1300 rpm. Due to severe internal leakages that occurred in iv the machine, only a limited range of pressures for expander suction and compressor discharge pressure was possible, and in this case, it was from 1.1 to 1.7 bar.The measured data were used to validate the mathematical models. It was found that the average standard deviation between the measured and predicted average torques is 10.5% and that of mass flow rates is 16.1%. Additionally, the comparison between the measured and predicted results shows that the mathematical model is capable of predicting the variation of pressure in the working chamber. As a result of severe internal leakages, the volumetric efficiencies of the machine were measured to be 3.6% to 63.6%.With the validated mathematical model, th...

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Development of the free piston expander for work recovery in transcritical CO₂ refrigeration cycle

Cited by 10 publications

References 2 publications

Comparison between modeling and experiments on a two-stage rotary vane expander for an HFC-410A air conditioning system

Comparison between modeling and experiments on a two-stage rotary vane expander for an HFC-410A air conditioning system

An Experimental Study on Energy Recovery by a Pelton-Type Expander in a Domestic Refrigeration System

Development of an energy-efficient expander-compressor unit for refrigeration systems

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Development of the free piston expander for work recovery in transcritical CO2 refrigeration cycle

Cited by 10 publications

References 2 publications

Comparison between modeling and experiments on a two-stage rotary vane expander for an HFC-410A air conditioning system

Comparison between modeling and experiments on a two-stage rotary vane expander for an HFC-410A air conditioning system

An Experimental Study on Energy Recovery by a Pelton-Type Expander in a Domestic Refrigeration System

Development of an energy-efficient expander-compressor unit for refrigeration systems

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Product

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Development of the free piston expander for work recovery in transcritical CO₂ refrigeration cycle