scholarly journals Exergy analysis of a reversible chiller

2021 ◽  
pp. 105-106
Author(s):  
Volodymyr Voloshchuk ◽  
Olena Nekrashevych ◽  
Volodymyr Voloshchuk ◽  
Pavlo Gikalo
Keyword(s):  
Heat Exchangers ◽  
Exergy Analysis ◽  
System Component ◽  
Space Heating ◽  
Exergy Destruction ◽  
Exergetic Analysis ◽  
Operational Modes

The work presents the results of exergetic analysis of a reversible chiller providing both cooling and space heating in varying operational modes. The year values of avoidable parts of exergy destruction occurring in each system component are used for the analysis. The outcomes obtained showed that the both inside and outside heat exchangers have the highest priority for improvement revealing more than 718 kW-hr avoidable year exergy destruction within the system.

scholarly journals Advanced exergetic analysis of a heat pump providing space heating in built environment

Energetika ◽  
2017 ◽  
Vol 63 (3) ◽  
Author(s):  
Volodymyr A. Voloshchuk
Keyword(s):  
Built Environment ◽  
Energy Conversion ◽  
Heat Pump ◽  
System Component ◽  
Space Heating ◽  
Exergy Destruction ◽  
Operating Modes ◽  
Conversion System ◽  
Energy Conversion System ◽  
Exergetic Analysis

In addition to conventional exergy-based methods, advanced exergetic analyses consider the interactions among components of the energy-conversion system and the real potential for improving each system component. The paper demonstrates the results of application of a detailed advanced exergetic analysis to a wastewater source heat pump providing space heating in the built environment. In order to determine thermodynamic parameters of the refrigeration vapour compression cycle in different operating modes, the simulation model has been used. The analysis includes splitting the exergy destruction within each component of a heat pump into unavoidable, avoidable, endogenous and exogenous parts as well as detailed splitting of the avoidable exogenous exergy destruction. Besides, variabilities of heating demands of a building within both the chosen heating season and also from year to year are taken into account. Distribution of the split exergy destructions during different periods of time is also presented for the analysed cases of the heat pump and built environment. It is shown that in the investigated system only about 50% of the total annual destruction in components of the heat pump can be avoided. About 30…40% of this avoidable thermodynamic inefficiency is caused by interactions among components. Based on the applied advanced exergetic analysis it is possible to receive more precise and useful information for better understanding and improving the design and operation of the analysed energy-conversion system.

scholarly journals Exergy-based Investigation of Various Heat Pumps for Enhancement of Their Thermodynamic Efficiency

2019 ◽  
pp. 168
Author(s):  
Volodymyr Voloshchuk ◽  
Paride Gullo
Keyword(s):  
Built Environment ◽  
Heat Exchangers ◽  
Heat Pumps ◽  
Space Heating ◽  
Thermodynamic Efficiency ◽  
Exergy Destruction ◽  
Exergetic Analysis

The work demonstrates the results of application of the detailed advanced exergetic analysis to air-source, watersource and wastewater-source heat pumps providing space heating in the built environment. Cumulative values based on seasonal exergy destruction are used for deriving conclusions. It is shown that in the specified conditions of the investigated systems priorities for improving should be given to heat exchangers.

Advanced Exergoeconomic Evaluation and Its Application to Compression Refrigeration Machines

2007 ◽  
Author(s):  
George Tsatsaronis ◽  
Tatiana Morosuk
Keyword(s):  
Energy Conversion ◽  
Exergy Analysis ◽  
System Component ◽  
Exergy Destruction ◽  
Conversion System ◽  
Investment Cost ◽  
Energy Conversion System ◽  
The Cost ◽  
Refrigeration Machine

Splitting the exergy destruction within each component of an energy conversion system into endogenous/exogenous and unavoidable/avoidable parts enhances an exergy analysis and improves the quality of the conclusions obtained from the analysis. The potential for improving each system component is identified and priorities, according to which the design of components should be modified, are established. We call this detailed exergy analysis advanced exergy analysis. For improving the cost effectiveness of an energy conversion system, splitting the investment cost into endogenous/exogenous and unavoidable/avoidable parts is also helpful. The designer should focus on the avoidable thermodynamic inefficiencies (exergy destruction), their costs and the avoidable investment costs. The paper discusses the calculation of these costs in general and the resulting advanced exergoeconomic evaluation that is based on the avoidable endogenous and the avoidable exogenous values for exergy destruction, cost of exergy destruction and investment cost. An application of this methodology to a compression refrigeration machine is presented.

scholarly journals Exergy Efficiency Optimization for Gas Turbine Based Cogeneration Systems

2013 ◽  
Author(s):  
Ana C. Ferreira ◽  
Senhorinha F. Teixeira ◽  
José C. Teixeira ◽  
Manuel L. Nunes ◽  
Luís B. Martins
Keyword(s):  
Gas Turbine ◽  
Gas Turbines ◽  
Exergy Analysis ◽  
Exergy Efficiency ◽  
Plant Performance ◽  
System Component ◽  
Inlet Temperature ◽  
Exergy Destruction ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

Energy degradation can be calculated by the quantification of entropy and loss of work and is a common approach in power plant performance analysis. Information about the location, amount and sources of system deficiencies are determined by the exergy analysis, which quantifies the exergy destruction. Micro-gas turbines are prime movers that are ideally suited for cogeneration applications due to their flexibility in providing stable and reliable power. This paper presents an exergy analysis by means of a numerical simulation of a regenerative micro-gas turbine for cogeneration applications. The main objective is to study the best configuration of each system component, considering the minimization of the system irreversibilities. Each component of the system was evaluated considering the quantitative exergy balance. Subsequently the optimization procedure was applied to the mathematical model that describes the full system. The rate of irreversibility, efficiency and flaws are highlighted for each system component and for the whole system. The effect of turbine inlet temperature change on plant exergy destruction was also evaluated. The results disclose that considerable exergy destruction occurs in the combustion chamber. Also, it was revealed that the exergy efficiency is expressively dependent on the changes of the turbine inlet temperature and increases with the latter.

Endogenous and Exogenous Exergy Destruction in Thermal Systems

2006 ◽  
Author(s):  
George Tsatsaronis ◽  
Solange O. Kelly ◽  
Tatiana V. Morosuk
Keyword(s):  
Exergy Analysis ◽  
System Optimization ◽  
Energy System ◽  
General Concept ◽  
System Component ◽  
Thermal System ◽  
Exergy Destruction ◽  
Thermal Systems ◽  
System Components ◽  
Refrigeration Machine

One of the roles of exergy analysis is to provide thermal system designers and operators with information useful for the system optimization. An exergy analysis identifies the sources of thermodynamic inefficiencies by evaluating the exergy destruction within each system component. However, care must be taken when using the total exergy destruction within a component to reach conclusions regarding the optimization of the overall energy system. The reason is that the total exergy destruction occurring in a component is not due exclusively to that component but is also caused by the inefficiencies within the remaining system components. The endogenous exergy destruction within a component is defined as that part of the component's exergy destruction that is independent of any change in the exergy destruction within the remaining components. The part of the component's exergy destruction which depends upon the changes of the exergy destruction within the other components is defined as the exogenous exergy destruction. It is apparent that the sum of endogenous and exogenous exergy destruction is equal to the total exergy destruction within the component being considered. Knowledge of the exogenous and endogenous exergy destruction for the most important components can further assist the engineer in deciding whether an adjustment in that component or in the structure of the system (i.e. in the remaining components) is required to improve the overall system. The paper presents the general concept of endogenous and exogenous exergy destruction. Using a graphical approach, the endogenous and exogenous exergy destruction of a simple gas turbine process and simple refrigeration machine are investigated.

scholarly journals Advanced Exergy Analysis of Waste-Based District Heating Options through Case Studies

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4766
Author(s):  
Huseyin Gunhan Ozcan ◽  
Arif Hepbasli ◽  
Aysegul Abusoglu ◽  
Amjad Anvari-Moghaddam
Keyword(s):  
Real Time ◽  
Heat Exchangers ◽  
Exergy Analysis ◽  
Thermal Power ◽  
District Heating ◽  
Exergy Efficiency ◽  
Hot Water ◽  
Exergy Destruction ◽  
District Heating System ◽  
The Real

The heating of the buildings, together with domestic hot water generation, is responsible for half of the total generated heating energy, which consumes half of the final energy demand. Meanwhile, district heating systems are a powerful option to meet this demand, with their significant potential and the experience accumulated over many years. The work described here deals with the conventional and advanced exergy performance assessments of the district heating system, using four different waste heat sources by the exhaust gas potentials of the selected plants (municipal solid waste cogeneration, thermal power, wastewater treatment, and cement production), with the real-time data group based on numerical investigations. The simulated results based on conventional exergy analysis revealed that the priority should be given to heat exchanger (HE)-I, with exergy efficiency values from 0.39 to 0.58, followed by HE-II and the pump with those from 0.48 to 0.78 and from 0.81 to 0.82, respectively. On the other hand, the simulated results based on advanced exergy analysis indicated that the exergy destruction was mostly avoidable for the pump (78.32–78.56%) and mostly unavoidable for the heat exchangers (66.61–97.13%). Meanwhile, the exergy destruction was determined to be mainly originated from the component itself (endogenous), for the pump (97.50–99.45%) and heat exchangers (69.80–91.97%). When the real-time implementation was considered, the functional exergy efficiency of the entire system was obtained to be linearly and inversely proportional to the pipeline length and the average ambient temperature, respectively.

scholarly journals Exergetic Analysis of Bioethanol Production from Tunisian Waste Dates

2018 ◽  
Vol 11 (1) ◽  
pp. 19-32 ◽  
Author(s):  
Wahada Zeineb ◽  
Khila Zouhour ◽  
Louhichi Boulbaba ◽  
Boukchina Rachid ◽  
Hajjaji Noureddine
Keyword(s):  
Production Process ◽  
Chemical Engineering ◽  
Exergy Analysis ◽  
System Development ◽  
Assessment Tools ◽  
Bioethanol Production ◽  
Exergy Destruction ◽  
Laws Of Thermodynamics ◽  
Energy Exchanges ◽  
Exergetic Analysis

Objective:This study aims at contributing to the area of sustainable bioethanol production system development. The main objective of this study is to thermodynamically evaluate a bioethanol production process from waste dates.Methods & Materials:To this end, several chemical engineering assessment tools have been simultaneously applied. These tools simulate the bioethanol production process using the SuperPro software in order to determine all the materials and energy exchanges. An exergy analysis is also carried out, based on the first and second laws of thermodynamics, in order to locate thermodynamic imperfections in the process.Results:The results obtained show that approximately 60% of the exergy fed to the process is recovered in the useful products (bioethanol and exhausted pulp used as feedstuff). The overall exergy destroyed in the process considered is about 377 kW which represents 7% of the exergy reaching the process. The distillation section, the most energy-intensive stage, constitutes the main contributor of exergy destruction, followed by the fermentation reactor with contributions of 47% and 33%, respectively.

Thermodynamic Evaluation of a Direct Expansion Ground-Sourced Heat Pump with Horizontal Ground Heat Exchangers Using Advanced Exergy Analysis

2021 ◽  
Author(s):  
Abdolazim Zarei ◽  
Mehran Ameri ◽  
Hossein Ghazizade-Ahsaee
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Exergy Analysis ◽  
Thermodynamic Evaluation ◽  
Ground Heat Exchanger ◽  
Exergy Destruction ◽  
Direct Expansion ◽  
Expansion Valve ◽  
System Improvement

This paper deals with the advanced exergetic analysis of a horizontal direct-expansion ground sourced CO2 heat pump operating in a transcritical cycle. The cycle is thermodynamically modeled in Engineering Equation Solver (EES) considering the pressure drops in both high and low temperature heat exchangers, and the system is to provide a fixed heating load. Conventional exergy analysis orderly suggests a compressor, expansion valve, gas cooler and ground heat exchanger to be considered for system improvement, while tracing exergy destruction of all components in detail demonstrates true improvement potential of each and all components and the system as a whole and offers a different order. Advanced exergy analysis points out that the compressor is directly and indirectly responsible for 56% of the overall exergy destruction generated in the cycle, confirming the detrimental role of this component in the system. The second influential component is recognized to be a ground heat exchanger accounting for 20% exergy destruction of the compressor as well as submitting 89% avoidability in its own exergy destruction, and expansion valve proves to be the last option for system improvement according to this analysis.

Advanced Exergetic Analysis is a Modern Tool for Evaluation and Optimization of Refrigeration Systems

2015 ◽  
pp. 85-105
Author(s):  
Tatiana Morosuk ◽  
George Tsatsaronis
Keyword(s):  
Practical Method ◽  
System Component ◽  
Exergy Destruction ◽  
Real Potential ◽  
The Real ◽  
Exergetic Analysis ◽  
Refrigeration Machine ◽  
Modern Tool

In the last decades an exergetic analysis became increasingly popular because this analysis identifies the location, magnitude and sources of thermodynamic inefficiencies. A conventional exergetic analysis, however, does not consider (a) the real potential for improving a system nor (b) the interactions among the components of the system. The interactions among different components of the same system can be estimated and the quality of the conclusions obtained from an exergetic evaluation can be improved, when the exergy destruction (irreversibilities) within each system component are split into endogenous/exogenous and avoidable/ unavoidable parts. We call this advanced exergetic analysis. The purpose of this chapter is to demonstrate that the advanced exergetic analysis is a practical method that allows engineers to extract useful information and conclusions and to develop ideas and solutions that cannot be suggested by other methods. In this chapter the conventional and advanced exergetic analysis are applied to an air refrigeration machine.

scholarly journals Proposal and Thermodynamic Assessment of S-CO2 Brayton Cycle Layout for Improved Heat Recovery

Entropy ◽  
2020 ◽  
Vol 22 (3) ◽  
pp. 305 ◽  
Author(s):  
Muhammad Ehtisham Siddiqui ◽  
Khalid H. Almitani
Keyword(s):  
Heat Exchangers ◽  
Heat Recovery ◽  
Exergy Analysis ◽  
Thermodynamic Assessment ◽  
Brayton Cycle ◽  
Efficiency Improvement ◽  
Exergy Destruction ◽  
Power Cycles ◽  
Recovery Mechanism ◽  
The Past

This article deals with the thermodynamic assessment of supercritical carbon dioxide (S-CO2) Brayton power cycles. The main advantage of S-CO2 cycles is the capability of achieving higher efficiencies at significantly lower temperatures in comparison to conventional steam Rankine cycles. In the past decade, variety of configurations and layouts of S-CO2 cycles have been investigated targeting efficiency improvement. In this paper, four different layouts have been studied (with and without reheat): Simple Brayton cycle, Recompression Brayton cycle, Recompression Brayton cycle with partial cooling and the proposed layout called Recompression Brayton cycle with partial cooling and improved heat recovery (RBC-PC-IHR). Energetic and exergetic performances of all configurations were analyzed. Simple configuration is the least efficient due to poor heat recovery mechanism. RBC-PC-IHR layout achieved the best thermal performance in both reheat and no reheat configurations ( η t h   = 59.7% with reheat and η t h   = 58.2 without reheat at 850 °C), which was due to better heat recovery in comparison to other layouts. The detailed component-wise exergy analysis shows that the turbines and compressors have minimal contribution towards exergy destruction in comparison to what is lost by heat exchangers and heat source.

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