Performance analysis and comprehensive comparison between CO2 and CO2/ethane azeotropy mixture as a refrigerant used in single-stage and two-stage vapor compression transcritical cycles

The stability and operational performance of single stage digestion with and without liquor recycle and two stage digestion were assessed using a mixture of paper and wood as the digestion substrate. Attempts to maintain stable digestion in both single stage reactors were unsuccessful due to the inherently low natural buffering capacity exhibited; this resulted in a rapid souring of the reactor due to unbuffered volatile fatty acid (VFA) accumulation. The use of lime to control pH was unsatisfactory due to interference with the carbonate/bicarbonate equilibrium resulting in wide oscillations in the control parameter. The two stage system overcame the pH stability problems allowing stable operation for a period of 200 days without any requirement for pH control; this was attributed to the rapid flushing of VFA from the first stage reactor into the second stage, where efficient conversion to methane was established. Reactor performance was judged to be satisfactory with the breakdown of 53% of influent volatile solids. It was concluded that the reactor configuration of the two stage system offers the potential for the treatment of cellulosic wastes with a sub-optimal carbon to nitrogen ratio for conventional digestion.

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Numerical assessment on the performance of variable area single- and two-stage ejectors: A comparative study

Proceedings of the Institution of Mechanical Engineers Part E Journal of Process Mechanical Engineering ◽

10.1177/09544089211033129 ◽

2021 ◽

pp. 095440892110331

Author(s):

Anil Kumar ◽

Virendra Kumar ◽

PMV Subbarao ◽

Surendra K Yadav ◽

Gaurav Singhal

Keyword(s):

Change Theory ◽

Single Stage ◽

Two Stage ◽

Entrainment Ratio ◽

Ansys Fluent ◽

One Dimensional ◽

Flow Parameters ◽

Constant Rate ◽

Numerical Assessment ◽

The One

The two-stage ejector has been suggested to replace the single-stage ejector geometrical configuration better to utilize the discharge flow’s redundant momentum to induce secondary flow. In this study, the one-dimensional gas dynamic constant rate of momentum change theory has been utilized to model a two-stage ejector along with a single-stage ejector. The proposed theory has been utilized in the computation of geometry and flow parameters of both the ejectors. The commercial computational fluid dynamics tool ANSYS-Fluent 14.0 has been utilized to predict performance and visualize the flow. The performance in terms of entrainment ratio has been compared under on- design and off-design conditions. The result shows that the two-stage ejector configuration has improved (≈57%) entrainment capacity than the single-stage ejector under the on-design condition.

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Two-Stage Evaporative Inlet Air Gas Turbine Cooling

Energies ◽

10.3390/en14051382 ◽

2021 ◽

Vol 14 (5) ◽

pp. 1382

Author(s):

Obida Zeitoun

Keyword(s):

Gas Turbine ◽

Gas Turbines ◽

Evaporative Cooling ◽

Air Cooling ◽

Vapor Compression ◽

Two Stage ◽

Turbine Cooling ◽

Riyadh City ◽

Vapor Compression Refrigeration ◽

Gas Turbine Cooling

Gas turbine inlet air-cooling (TIAC) is an established technology for augmenting gas turbine output and efficiency, especially in hot regions. TIAC using evaporative cooling is suitable for hot, dry regions; however, the cooling is limited by the ambient wet-bulb temperature. This study investigates two-stage evaporative TIAC under the harsh weather of Riyadh city. The two-stage evaporative TIAC system consists of indirect and direct evaporative stages. In the indirect stage, air is precooled using water cooled in a cooling tower. In the direct stage, adiabatic saturation cools the air. This investigation was conducted for the GE 7001EA gas turbine model. Thermoflex software was used to simulate the GE 7001EA gas turbine using different TIAC systems including evaporative, two-stage evaporative, hybrid absorption refrigeration evaporative and hybrid vapor-compression refrigeration evaporative cooling systems. Comparisons of different performance parameters of gas turbines were conducted. The added annual profit and payback period were estimated for different TIAC systems.

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Performance analysis of hydrogen fuel cell with two-stage turbo compressor for automotive applications

Energy Reports ◽

10.1016/j.egyr.2021.05.007 ◽

2021 ◽

Vol 7 ◽

pp. 2635-2646

Author(s):

Nabeel Ahsan ◽

Ans Al Rashid ◽

Asad A. Zaidi ◽

Ramsha Imran ◽

Sikandar Abdul Qadir

Keyword(s):

Fuel Cell ◽

Performance Analysis ◽

Hydrogen Fuel Cell ◽

Automotive Applications ◽

Hydrogen Fuel ◽

Two Stage ◽

Turbo Compressor

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Performance Analysis of the Test Results on a Two-Stage Transonic Fan

Journal of Engineering for Power ◽

10.1115/1.3227372 ◽

1983 ◽

Vol 105 (1) ◽

pp. 125-129

Author(s):

Baoshi Chen ◽

Tianyi Zhang

Keyword(s):

Mach Number ◽

Performance Analysis ◽

Radial Distribution ◽

Flow Separation ◽

High Load ◽

Test Results ◽

Two Stage ◽

Stall Margin ◽

High Incidence ◽

Transonic Fan

Test results obtained from a two-stage fan are analysed and the reasons that caused the design performance target not to be attained are presented in this paper. Addition of a partspan shroud on rotor 1 caused higher losses and changed radial distribution of parameters. Modification on the flowpath and chord length of stator 1 resulted in excessively high inlet Mach number and flow separation in the hub region. The high load and high incidence at the hub of rotor 2 caused higher losses and reduced stall margin of the fan.

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