Energy efficiency and exergy destruction of supersonic steam ejector based on nonequilibrium condensation model

2021 ◽  
Vol 189 ◽  
pp. 116704
Author(s):  
Hongbing Ding ◽  
Yafei Zhao ◽  
Chuang Wen ◽  
Chao Wang ◽  
Chunqian Sun
Keyword(s):  
Energy Efficiency ◽  
Exergy Destruction ◽  
Steam Ejector ◽  
Condensation Model ◽  
Nonequilibrium Condensation

Numerical Method for Simulating Flows of Supercritical CO2 Compressor With Nonequilibrium Condensation

2016 ◽  
Author(s):  
Takashi Furusawa ◽  
Hironori Miyazawa ◽  
Satoru Yamamoto
Keyword(s):  
Numerical Method ◽  
Supercritical Co2 ◽  
Mass Fraction ◽  
Leading Edge ◽  
Pressure Variation ◽  
Supercritical Pressure ◽  
Local Region ◽  
Preconditioning Method ◽  
Condensation Model ◽  
Nonequilibrium Condensation

We recently proposed a numerical method for simulating flows of supercritical CO2 based on a preconditioning method and the thermophysical models programed in a program package for thermophysical properties of fluids (PROPATH). In this study, this method is applied to the investigation of cascade channel. Numerical results obtained by assuming supercritical pressure conditions indicate that the normal shock generated in the cascade channel deeply depends on the pressure condition. In particular, the speed of sound varying with the pressure variation at the supercritical state is a key thermophysical property which changes the flow field in the cascade channel. In addition, we also simulate those flows with nonequilibrium condensation in which the inlet pressure and temperature approaching to those of the critical point are specified. Then a nonequilibrium condensation model developed by our group is further applied to the numerical method. CO2 condensation observed in a case indicates that condensation occurs at a local region near the leading edge due to the flow expansion; the droplets soon grow at the local region and streams downward with keeping almost the same mass fraction.

scholarly journals On the Application of Small-Scale Turbines in Industrial Steam Networks

Energies ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3149
Author(s):  
Ansgar Weickgenannt ◽  
Ivan Kantor ◽  
François Maréchal ◽  
Jürg Schiffmann
Keyword(s):  
Energy Efficiency ◽  
Design Guidelines ◽  
Economic Feasibility ◽  
Small Scale ◽  
Economic Potential ◽  
Exergy Destruction ◽  
Thermodynamic Process ◽  
Industrial Data ◽  
Specific Investment ◽  
Wide Energy

This study investigates the technical and economic feasibility of replacing throttling valves with smale-scale, oil-free turbomachinery in industrial steam networks. This is done from the perspective of the turbomachine, which has to be integrated into a new or existing process. The considered machines have a power range of P=[0.5,…,250 kW] and have been designed using real industrial data from existing processes. Design guidelines are developed, which take into account the thermodynamic process as well as engineering aspects of such a turbomachine. The results suggest that steam conditioning prior to heat exchange could be completed by small expanders to produce mechanical work, reducing exergy destruction and improving site-wide energy efficiency compared to throttling valves. Cost estimates for such machines are presented, which serve as a basis for case-specific investment calculations. The resulting payback times of less than 18 months highlight the economic potential such solutions.

EXERGY ANALYSIS OF GEOTHERMAL POWER PLANT KAMOJANG 68, 3 MW IN CAPACITY

2018 ◽  
Vol 7 (2) ◽  
Author(s):  
Amiral Aziz
Keyword(s):  
Energy Efficiency ◽  
Power Plant ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Preliminary Design ◽  
Exergy Destruction ◽  
Geothermal Power Plant ◽  
Production Wells ◽  
Geothermal Power ◽  
Exergy Losses

The importance of exergy analysis in preliminary design of geothermal power has been proven. An exergy analysis was carried out and the locations and quantities of exergy losses, wastes and destructions in the different processes of the plan were pinpointed. The obtained results show that the total exergy available from production wells KMJ 68 was calculated to be 6967.55 kW. The total exergy received from wells which is connected during the analysis and enter into the separator was found to be 6337.91 kW in which 5808.8 kW is contained in the steam phase. The overall exergy efficiency for the power plant is 43.06% and the overall energy efficiency is 13.05 %, in both cases with respect to the exergy from the connected wells. The parts of the system with largest exergy destruction are the condenser, the turbine, and the disposed waste brinekeywords: exergy, irreversibility, geothermal power plant, KMJ 68

scholarly journals Performance Enhancement of Nitrogen Dual Expander and Single Mixed Refrigerant LNG Processes Using Jaya Optimization Approach

Energies ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 3278
Author(s):  
Ali Rehman ◽  
Muhammad Abdul Qyyum ◽  
Ashfaq Ahmad ◽  
Saad Nawaz ◽  
Moonyong Lee ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Energy Consumption ◽  
Natural Gas ◽  
Design Optimization ◽  
Lower Energy ◽  
Operating Costs ◽  
Small Scale ◽  
Exergy Destruction ◽  
Capital Costs ◽  
Design Variables

The nitrogen (N2) expander and single mixed refrigerant (SMR) liquefaction processes are recognized as the most favorable options to produce liquefied natural gas (LNG) at small-scale and offshore sites. These processes have a simple and compact design that make them efficient with respect to their capital costs. Nevertheless, huge operating costs, mainly due to their lower energy efficiency, remains an ongoing issue. Utilization of design variables having non-optimal values is the primary cause for the lower energy efficiency; which, in turn, leads to exergy destruction (i.e., entropy generation), and ultimately the overall energy consumption is increased. The optimal execution of the design variables of LNG processes can be obtained through effective design optimization. However, the complex and highly non-linear interactions between design variables (refrigerant flowrates and operating pressures) and objective function (overall energy consumption) make the design optimization a difficult and challenging task. In this context, this study examines a new optimization algorithm, named “Jaya”, to reduce the operating costs of nitrogen dual expander and SMR LNG processes. The Jaya approach is an algorithm-specific parameter-less optimization methodology. It was found that by using the Jaya algorithm, the energy efficiency of the SMR process and nitrogen dual expander natural gas (NG) liquefaction process can be enhanced up to 14.3% and 11.6%, respectively, as compared to their respective base cases. Using the Jaya approach, significant improved results were observed even compared to other previously used optimization approaches for design optimization. Results of conventional exergy analysis revealed that the exergy destruction of SMR and N2 dual expander process can be reduced by 17.4% and 14%, respectively. Moreover, economic analysis identified the 13.3% and 11.6% relative operating costs savings for SMR and N2 dual expander LNG processes, respectively.

scholarly journals A Steam Ejector Refrigeration System Powered by Engine Combustion Waste Heat: Part 1. Characterization of the Internal Flow Structure

2019 ◽  
Vol 9 (20) ◽  
pp. 4275 ◽  
Author(s):  
Yu Han ◽  
Lixin Guo ◽  
Xiaodong Wang ◽  
Anthony Chun Yin Yuen ◽  
Cuiling Li ◽  
...  
Keyword(s):  
Energy Efficiency ◽  
Flow Structure ◽  
Waste Heat ◽  
Mixing Layer ◽  
Internal Flow ◽  
Fluid Temperature ◽  
Refrigeration System ◽  
Shock Train ◽  
Steam Ejector ◽  
Primary Fluid

With the escalating production of automobiles, energy efficiency and environmental friendliness have always been a major concern in the automotive industry. In order to effectively lower the energy consumption of a vehicle, it is essential to develop air-conditioning systems that can make good use of combustion waste heat. Ejector refrigeration systems have become increasingly popular for this purpose due to their energy efficiency and ability to recycle waste heat. In this article, the elements affecting the performance of a typical ejector refrigeration system have been explored using both experimental and numerical approaches. For the first time, the internal flow structure was characterized by means of comprehensive numerical simulations. In essence, three major sections of the steam ejector were investigated. Two energy processes and the shock-mixing layer were defined and analyzed. The results indicated that the length of the choking zone directly affects the entertainment ratio under different primary fluid temperature. The optimum enterainment ratio was achieved with 138 °C primary fluid temperature. The shock-mixing layer was greatly affected by secondary fluid temperature. With increasing of back pressure, the normal shock gradually shifted from the diffuser towards the throat, while the shock train length remains lunchanged.

scholarly journals A POINT OF VIEW ON THE PERCEPTION OF FUTURE PROFESSIONALS ON ENERGY EFFICIENCY OF REFIRGERATION SYSTEMS

2021 ◽  
Vol 1 (2021) ◽  
pp. 38-43
Author(s):  
Ionela Ticu ◽  
Elena Gogu
Keyword(s):  
Energy Efficiency ◽  
Point Of View ◽  
Industrial Processes ◽  
Exergy Destruction ◽  
Environment Protection ◽  
International Context ◽  
Modern Times ◽  
Efficiency Assessment ◽  
National Leaders ◽  
Important Activity

In the modern times, energy efficiency is of high interest because there is direct link between this concept and energy conservation, economics, environment and sustainable development. The energy efficiency intensification at international level is closely follow by national leaders and worldwide governments and organisations and by top companies as well. Considering this obvious aspects, higher education institutions are deeply involved in involving energy efficiency in the curricula of future professionals, in order to allow them to gain skills that will help in solving challenges specific to this activity. In this international context, Constanta Maritime University introduced in the curricula of the students enrolled in the specialization called Engineering and Environment Protection in Industry a discipline dealing with this very important activity, named Thermal Efficiency of Buildings and Industrial Processes. This paper is investigating the manner in which our students have mastered the tools of energy efficiency assessment of refrigeration systems, throughout a questionnaire applied to them, at the end of the chapter dedicated to these technologies. The students had to write short comments to very specific questions. Analysis of the comments helps the lecturer and the students to take appropriate measures in the next future. Thus, the feedback resulted to be quite positive because most of the students gained the knowledge provided in this respect. Still, delicate concepts, such as entropy, exergy or exergy destruction seem to raise difficulties to some students. In this respect, results that such an intermediary assessment has to be repeated more often, for other kind of technologies discussed during this course, with the involvement of the concepts introduced by the second law- which are essential in energy efficiency assessments.

scholarly journals Performance Evaluation of a Full-Scale Fused Magnesia Furnace for MgO Production Based on Energy and Exergy Analysis

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 214
Author(s):  
Tianchi Jiang ◽  
Weijun Zhang ◽  
Shi Liu
Keyword(s):  
Energy Efficiency ◽  
Mass Transport ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Smelting Process ◽  
Exergy Destruction ◽  
Electric Power Supply ◽  
Flow Energy ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis

A three-electrode alternating current fused magnesia furnace (AFMF) with advanced control technology was evaluated by combined energy and exergy analysis. To gain insight into the mass flow, energy flow and exergy efficiency of the present fused magnesia furnace, the exergy destruction was analysed to study the energy irreversibility of the furnace. Two different production processes, the magnesite ore smelting process (MOP) and light-calcined magnesia process (LMP), are discussed separately. Two methods were carried out to improve LMP and MOP; one of which has been applied in factories. The equipment consists of an electric power supply system, a light-calcined system and a three-electrode fused magnesia furnace. All parameters were tested or calculated based on the data investigated in industrial factories. The calculation results showed that for LMP and MOP, the mass transport efficiencies were 16.6% and 38.3%, the energy efficiencies were 62.2% and 65.5%, and the exergy destructions were 70.5% and 48.4%, respectively. Additionally, the energy efficiency and exergy efficiency of the preparation process of LMP were 39.4% and 35.6%, respectively. After the production system was improved, the mass transport efficiency, energy efficiency and exergy destruction were determined.

scholarly journals Computational fluid dynamics simulation of the supersonic steam ejector using different condensation model

2019 ◽  
Vol 23 (3 Part A) ◽  
pp. 1655-1661 ◽  
Author(s):  
Lin Cai ◽  
Miao He ◽  
Ke-Zhen Huang ◽  
Wei Xiong
Keyword(s):  
Fluid Dynamics ◽  
Experimental Data ◽  
Slip Velocity ◽  
Dynamics Simulation ◽  
Computational Fluid Dynamics Simulation ◽  
Entrainment Ratio ◽  
Maximum Value ◽  
Steam Ejector ◽  
Homogenous Nucleation ◽  
Condensation Model

This paper addresses the non-equilibrium condensation (NEC) in supersonic steam ejector under the assumptions of no slip velocity between the droplets and vapor phase and homogenous nucleation. The experimental data carried out by Moore has been used to verify the numerical results. It is illustrated that the maximum value of the flow mach number of the NEC model is lower than that of the equilibrium condensation model, and NEC model increases the ejector?s entrainment ratio in comparison equilibrium condesation model. When using the NEC model, the nucleation characteristics such as subcooling degree, nucleation rate could be obtained in ejector flow field.

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