A modified exergy analysis method for vapor compression systems: splitting refrigerant exergy destruction

2021 ◽  
pp. 117728
Author(s):  
Mengdi Cui ◽  
Baolong Wang ◽  
Falin Wei ◽  
Wenxing Shi
Keyword(s):  
Exergy Analysis ◽  
Vapor Compression ◽  
Exergy Destruction ◽  
Analysis Method ◽  
Vapor Compression Systems

scholarly journals Energy and Exergy Analysis of Combined Organic Rankine Cycle-Single and Dual Evaporator Vapor Compression Refrigeration Cycle

2019 ◽  
Vol 9 (23) ◽  
pp. 5028 ◽  
Author(s):  
Pektezel ◽  
Acar
Keyword(s):  
Exergy Analysis ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Refrigeration Cycle ◽  
Vapor Compression ◽  
Exergy Destruction ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis ◽  
Vapor Compression Refrigeration

This paper presents energy and exergy analysis of two vapor compression refrigeration cycles powered by organic Rankine cycle. Refrigeration cycle of combined system was designed with single and dual evaporators. R134a, R1234ze(E), R227ea, and R600a fluids were used as working fluids in combined systems. Influences of different parameters such as evaporator, condenser, boiler temperatures, and turbine and compressor isentropic efficiencies on COPsys and ƞex,sys were analyzed. Second law efficiency, degree of thermodynamic perfection, exergy destruction rate, and exergy destruction ratio were detected for each component in systems. R600a was determined as the most efficient working fluid for proposed systems. Both COPsys and ƞex,sys of combined ORC-single evaporator VCR cycle was detected to be higher than the system with dual evaporator.

Extended Exergy Analysis Based Comparison of Subcritical and Transcritical Refrigeration Systems

2016 ◽  
Vol 24 (02) ◽  
pp. 1650009 ◽  
Author(s):  
Jahar Sarkar ◽  
Dnyanesh Joshi
Keyword(s):  
Exergy Analysis ◽  
Vapor Compression ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
Vapor Compression Refrigeration ◽  
System Improvement

The main purpose of this study is to apply advanced exergy analysis to the transcritical CO2 vapor compression refrigeration system, and compare with the analysis of subcritical cycle using ammonia and R404a. Endogenous, exogenous, avoidable and unavoidable exergy destructions are determined for each component of these systems. For CO2 system, compressor contributes highest avoidable endogenous exergy destruction and gas cooler contributes highest avoidable exogenous exergy destruction. It is concluded that compressor is the first component for CO2 and R404a, and evaporator is the first component for NH3 to be improved. System improvement options to reduce the exergy destruction are discussed as well.

scholarly journals Advanced exergy analysis of the natural gas liquid recovery process

2021 ◽  
pp. 311-311
Author(s):  
Fakhrodin Jovijari ◽  
Abbas Kosarineia ◽  
Mehdi Mehrpooya ◽  
Nader Nabhani
Keyword(s):  
Heat Exchanger ◽  
Natural Gas ◽  
Exergy Analysis ◽  
Recovery Process ◽  
Exergy Destruction ◽  
Analysis Method ◽  
System Improvement ◽  
Southwest Of Iran ◽  
Oil Company

Energy quality in each country is one of the important indicators of economic development, Which affects the economic growth of that country. Exergy analysis, considering all flow properties including pressure, temperature, composition, is a powerful way to evaluate the energy consumption of equipment such as natural gas and liquefied gas plants. Inefficiency of a system can be defined by the conventional exergy analysis method, While, irreversible resources and real potentials for system improvement can only be identified by the advanced exergy analysis method. This analysis splits conventional exergy destruction into two exogenous and endogenous parts according to origin, and also unavoidable and avoidable parts according to the ability to remove and modifications. In this method, the exergy concept was separated by considering the ideal and avoidable condition assumptions. As a real case study, a natural gas liquid plant 800, from National Iranian South Oil Company located in southwest of Iran was considered to be investigated by conventional exergy analysis, advanced exergy analysis methods. The results of conventional exergy analysis illustrated that the highest amount of exergy destruction belonged to compressor and heat exchanger with 509.99 and 629.04 kW, respectively. However, in the case of heat exchanger, despite having the highest rate of exergy destruction, it is not considered in modification priorities due to its low avoidable exergy destruction value. Also, advanced exergy analysis suggested that the exergy destruction of the compressor and heat exchanger will be reduced by improving performance of these components.

Energy and Exergy Analysis of Vapor Compression Refrigeration System with Flooded Evaporator

2019 ◽  
Vol 27 (04) ◽  
pp. 1950041 ◽  
Author(s):  
Chukwuemeka J. Okereke ◽  
Idehai O. Ohijeagbon ◽  
Olumuyiwa A. Lasode
Keyword(s):  
Exergy Analysis ◽  
Vapor Compression ◽  
Exergy Destruction ◽  
Refrigeration System ◽  
High Compression Ratio ◽  
Cooling Plate ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis ◽  
Vapor Compression Refrigeration ◽  
Potential Area

In this study, energy and exergy analysis was used to evaluate the performance of a vapor compression refrigeration system with a flooded evaporator and the causes of high temperatures of beverage during the production process determined. Subsequently, the components of the operation that require modification were identified in order to improve the system performance. The actual operating parameters related to energy and exergy analysis of the investigated beverage manufacturing plant were measured, the thermal properties of the beverage were determined from a calorimeter experiment, and mathematical models were developed based on the first and second laws of thermodynamics from the literature. The system energy and exergy efficiencies were 57.46% and 21.17%, respectively, whereas the system exergy destruction was 695.71[Formula: see text]kW. The highest exergy destruction among the components of the refrigeration system occurred at the cooling plate, followed by the ammonia compressor. The cooling plate also experienced a loss in the refrigerating effect of 43.59[Formula: see text]kW. Therefore, the cooling plate is the area with the highest potential for improvement. The ammonia compressor presents another potential area of improvement, which includes operating the compressor at a high compression ratio and high superheated temperature. However, the reduction of beverage inlet mass flow rate at the cooling plate offers the best opportunity to achieve a low beverage temperature between 1.00∘C and 2.00∘C and decreasing the system exergy destruction without incurring additional investment costs.

scholarly journals Conventional and Advanced Exergoeconomic Analysis of a Compound Ejector-Heat Pump for Simultaneous Cooling and Heating

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3511
Author(s):  
Ali Khalid Shaker Al-Sayyab ◽  
Joaquín Navarro-Esbrí ◽  
Victor Manuel Soto-Francés ◽  
Adrián Mota-Babiloni
Keyword(s):  
Heat Pump ◽  
Exergy Analysis ◽  
Waste Heat ◽  
District Heating ◽  
Cost Comparison ◽  
Exergy Destruction ◽  
Pump System ◽  
Heat Pump System ◽  
Destruction Rate ◽  
Exergoeconomic Analysis

This work focused on a compound PV/T waste heat driven ejector-heat pump system for simultaneous data centre cooling and waste heat recovery for district heating. The system uses PV/T waste heat as the generator’s heat source, acting with the vapour generated in an evaporative condenser as the ejector drive force. Conventional and advanced exergy and advanced exergoeconomic analyses are used to determine the cause and avoidable degree of the components’ exergy destruction rate and cost rates. Regarding the conventional exergy analysis for the whole system, the compressor represents the largest exergy destruction source of 26%. On the other hand, the generator shows the lowest sources (2%). The advanced exergy analysis indicates that 59.4% of the whole system thermodynamical inefficiencies can be avoided by further design optimisation. The compressor has the highest contribution to the destruction in the avoidable exergy destruction rate (21%), followed by the ejector (18%) and condenser (8%). Moreover, the advanced exergoeconomic results prove that 51% of the system costs are unavoidable. In system components cost comparison, the highest cost comes from the condenser, 30%. In the same context, the ejector has the lowest exergoeconomic factor, and it should be getting more attention to reduce the irreversibility by design improving. On the contrary, the evaporator has the highest exergoeconomic factor (94%).

Study on Energy Consumption Analysis Method of Distributed Cryogenic Separation System

2013 ◽  
Vol 732-733 ◽  
pp. 52-56
Author(s):  
Zhi Guo Wang ◽  
Lei Zhang ◽  
Chai Ling Yin
Keyword(s):  
Energy Use ◽  
Exergy Analysis ◽  
Waste Heat ◽  
Engineering Practice ◽  
Analysis Method ◽  
Analysis Model ◽  
Two Stage ◽  
Separation Plant ◽  
Flow Energy ◽  
Saving Effect

Cryogenic separation method is the main method to recycle NGL (Natural Gas Liquid). Oilfield two-stage expansion NGL cryogenic separation plant is a complex system composed of varieties of material flow, energy flow and equipments, is a typical distributed energy use system composed of three parts, energy supply, energy use and waste heat recovery. In this paper, according to the process characteristics of two-stage expansion cryogenic separation plant, three-box analysis method was used, the system was compartmentalized into six subsystems, represented the exergy analysis model of system—unit—equipment, given the specific analysis process and the assessment rules for the NGL system. Using the practical operational data, the writers conduct the exergy analysis on the operational working condition of Daqing oilfield NGL system. Based on the calculation results, this paper raises some proposals to improve the operational efficiency, and achieved a good energy saving effect in engineering practice.

Energy and Exergy Analysis of the Teduction Zone in a Downdraft (Biomass) Gasifier

2010 ◽  
Vol 8 (1) ◽  
Author(s):  
Avdhesh Kr. Sharma ◽  
Raj Kumar Singh
Keyword(s):  
Kinetic Models ◽  
Exergy Analysis ◽  
Internal Heat ◽  
Calorific Value ◽  
Exergy Destruction ◽  
Reduction Zone ◽  
Reactor Performance ◽  
General Validity ◽  
Energy And Exergy ◽  
Energy And Exergy Analysis

This article describes the energy and exergy analysis of the reduction zone in a downdraft biomass gasifier. A simplistic formulation for describing the pyrolysis and oxidation of these products has been presented for initialization. Equilibrium and kinetic models are used to predict the reduction products leaving the reduction zone and thus the 1st law efficiency. In the reduction zone, exergy destruction due to chemical, physical, compositional, internal heat transfer and heat loss to the surrounding has been quantified to describe 2nd law efficiency. The comparison of equilibrium and kinetic models is carried out with experimental data for general validity. Parametric analysis of char bed length and inflow temperature on gas composition, un-converted char, exergy destruction, 1st law and the 2nd law efficiency has also been carried out. Simulation results identified a critical char bed length (where all char gets consumed) for a given feedstock, which depends on residence time and reaction temperature in the reduction zone. Near critical char bed length, predictions show high calorific value of gas with relatively less exergy destruction and thus optimum reactor performance. The accuracy of the prediction depends on the validity of initial input conditions.

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