Piston-cylinder work producing expansion device in a transcritical carbon dioxide cycle. Part I: experimental investigation

Baek, J. S.; Groll, Eckhard A.; Lawless, Patrick B.

doi:10.1016/j.ijrefrig.2004.08.006

Cited by 86 publications

(25 citation statements)

References 1 publication

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“…The valve train signifcantly influences the stable operation of the FPE and flow loss during its intake and exhaust processes [36,37]. Two kinds of valve trains can be selected for the FPE, namely, mechanical control valve manner and electromagnetic control valve manner.…”

Section: Valve Trainmentioning

confidence: 99%

Preliminary Development of a Free Piston Expander–Linear Generator for Small-Scale Organic Rankine Cycle (ORC) Waste Heat Recovery System

Zhang

Yang

et al. 2016

Energies

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Abstract:A novel free piston expander-linear generator (FPE-LG) integrated unit was proposed to recover waste heat efficiently from vehicle engine. This integrated unit can be used in a small-scale Organic Rankine Cycle (ORC) system and can directly convert the thermodynamic energy of working fluid into electric energy. The conceptual design of the free piston expander (FPE) was introduced and discussed. A cam plate and the corresponding valve train were used to control the inlet and outlet valve timing of the FPE. The working principle of the FPE-LG was proven to be feasible using an air test rig. The indicated efficiency of the FPE was obtained from the p-V indicator diagram. The dynamic characteristics of the in-cylinder flow field during the intake and exhaust processes of the FPE were analyzed based on Fluent software and 3D numerical simulation models using a computation fluid dynamics method. Results show that the indicated efficiency of the FPE can reach 66.2% and the maximal electric power output of the FPE-LG can reach 22.7 W when the working frequency is 3 Hz and intake pressure is 0.2 MPa. Two large-scale vortices are formed during the intake process because of the non-uniform distribution of velocity and pressure. The vortex flow will convert pressure energy and kinetic energy into thermodynamic energy for the working fluid, which weakens the power capacity of the working fluid.

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Section: Valve Trainmentioning

confidence: 99%

Preliminary Development of a Free Piston Expander–Linear Generator for Small-Scale Organic Rankine Cycle (ORC) Waste Heat Recovery System

Zhang

Yang

et al. 2016

Energies

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“…The cycle is comprised of two compressors, a condenser, an evaporator, an ITE and an expansion valve. The refrigerant vapor leaving the evaporator (1) and enters the low-stage compressor, where it is compressed to an intermediate pressure (2). Then it is mixed with the refrigerant vapor (4G) discharged from outlet 2 of the ITE.…”

Section: The Improved Impulse Turbo Expander and The Corresponding Cyclementioning

confidence: 99%

“…The two values become lower when HCFCs/HFCs are used as refrigerants, but the gain is still interesting to enhance the overall efficiency of the system, especially for large capacity systems, where it is not only evaluated in a relative value but also in an absolute value. In recent years, various expander concepts and prototypes have been investigated and developed for the transcritical CO 2 refrigeration cycles as well as subcritical refrigeration systems with traditional HCFCs/HFCs as refrigerants, e.g., piston [2,3], rolling/swing piston [4][5][6][7], vane [8][9][10], scroll [11][12][13], and screw [14,15], which have demonstrated the viability of this approach. The economizer is another device used to decrease the throttling loss and improve the cycle efficiency.…”

mentioning

confidence: 99%

Exergy Analysis of a Subcritical Refrigeration Cycle with an Improved Impulse Turbo Expander

Zhang

Tian

2014

Entropy

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Abstract:The impulse turbo expander (ITE) is employed to replace the throttling valve in the vapor compression refrigeration cycle to improve the system performance. An improved ITE and the corresponding cycle are presented. In the new cycle, the ITE not only acts as an expansion device with work extraction, but also serves as an economizer with vapor injection. An increase of 20% in the isentropic efficiency can be attained for the improved ITE compared with the conventional ITE owing to the reduction of the friction losses of the rotor. The performance of the novel cycle is investigated based on energy and exergy analysis. A correlation of the optimum intermediate pressure in terms of ITE efficiency is developed. The improved ITE cycle increases the exergy efficiency by 1.4%-6.1% over the conventional ITE cycle, 4.6%-8.3% over the economizer cycle and 7.2%-21.6% over the base cycle. Furthermore, the improved ITE cycle is also preferred due to its lower exergy loss.

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“…Yang et al [11] thermodynamically found that the employment of an expander to replace a throttle valve leads to about 33% COP improvement in the transcritical cycle. Baek et al [12,13] developed a piston-cylinder-type expander and represented that the device can improve the cooling COP by 6.6% through the theoretical and experimental studies. Li et al [14] experimentally found that their developed rolling-piston expander prototype can improve the COP of the system by at least 10%.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic Analysis of Double-Stage Compression Transcritical CO2 Refrigeration Cycles with an Expander

Zhang¹,

Tong²,

Wang³

2015

Entropy

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Four different double-compression CO2 transcritical refrigeration cycles are studied: double-compression external intercooler cycle (DCEI), double-compression external intercooler cycle with an expander (DCEIE), double-compression flash intercooler cycle (DCFI), double-compression flash intercooler cycle with an expander (DCFIE). The results showed that the optimum gas cooler pressure and optimum intermediate pressure of the flash intercooler cycles are lower than that of the external intercooler cycle. The use of an expander in the DCEI cycle leads to a decrease of the optimum gas cooler pressure and little variation of the optimum intermediate pressure. However, the replacement of the throttle valve with an expander in the DCFI cycle results in little variation of the optimal gas cooler pressure and an increase of the optimum intermediate pressure. The DCFI cycle outperforms the DCEI cycle under all the chosen operating conditions. The DCEIE cycle outperforms the DCFIE cycle when the evaporating temperature exceeds 0 °C or the gas cooler outlet temperature surpasses 35 °C. When the gas cooler exit temperature varies from 32 °C to 48 °C, the DCEI cycle, DCEIE cycle, DCFI cycle and DCFIE cycle yield averaged 4.6%, 29.2%, 12.9% and 22.3% COP improvement, respectively, over the basic cycle.

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Piston-cylinder work producing expansion device in a transcritical carbon dioxide cycle. Part I: experimental investigation

Cited by 86 publications

References 1 publication

Preliminary Development of a Free Piston Expander–Linear Generator for Small-Scale Organic Rankine Cycle (ORC) Waste Heat Recovery System

Preliminary Development of a Free Piston Expander–Linear Generator for Small-Scale Organic Rankine Cycle (ORC) Waste Heat Recovery System

Exergy Analysis of a Subcritical Refrigeration Cycle with an Improved Impulse Turbo Expander

Thermodynamic Analysis of Double-Stage Compression Transcritical CO2 Refrigeration Cycles with an Expander

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