Exergetic Assessment Research Articles

Energetic and exergetic assessment of two- and three-stage spray drying units for milk processing industry

Energetic and exergetic assessment of two- and three-stage spray drying units for milk processing industry

Energetic and exergetic assessment of operating biofuel, hydrogen and conventional JP-8 in a J69 type of aircraft turbojet engine

Energetic and exergetic assessment of operating biofuel, hydrogen and conventional JP-8 in a J69 type of aircraft turbojet engine

Energetic and Exergetic Assessment of Spiral Heat Exchanger Using Mineral and Oxide Mineral Oil Nanofluid

This paper presents an experimental analysis on the heat transfer and pressure drop enhancement of oil nanofluid flow. In this analysis, the first method has used the helically coiled tube and shell, the oil nanofluids were employed instead of the base fluid (oil) in the second process. the two techniques were used to improve the heat transfer and pressure drop. Nanofluid oil concentrations utilized within range from 1 to 5 percent vol. This paper applied two forms of nanoparticles: copper (Cu (20 nm)) and zirconium oxide (ZrO2 (40 nm)) and base fluid (oil). The influence on the heat transfer coefficient for different factors such as the flow number of Reynolds, the temperature of the nanofluid oil, the concentration and shape of the nanoparticle, and the pressure gradient of the flow have examined. The results indicated that the value of a 40.35 percent in the heat transfer coefficient for Cu + oil and 28.42 percent for ZrO2 + oil increased compared with the base fluid (oil) at 5 percent vol concentration. Using oil nanofluids (Cu, ZrO2 – oil) instead of the base fluid (oil) led to increasing in the heat transfer coefficient and decreasing the pressure. In addition, the result showed that the heat transfer efficiency has enhanced using the helically coiled tube and shell, as well as increasing in the pressure drop was due to the curvature of the tube. Baes on the relationship between viscosity and shear intensity, the oil nanofluid behaviors were similar to the standard Newtonian fluids. Moreover, the related flow and heat transfer methods are used to present the output index. The exergy inflow, exergy destruction and exergy efficiency of oil nanofluid (Cu +oil) were greater than the oil nanofluid (ZrO2 +oil) and oil. The exergy inflow, exergy destruction, and exergy efficiency for the two type of oil nanofluid increased with increasing of nanoparticles concentration.

A new geothermally driven combined plant with energy storage option for six useful outputs in a sustainable community

In this paper, a new integrated system using geothermal energy as a renewable source is developed and analyzed thermodynamically, and its performance evaluation in terms of numerous criteria is conducted. In order to reveal the importance of such a unique approach, multiple useful outputs are obtained from this integrated plant designed. These useful products from the geothermal power-based multigeneration system are primarily power, heat, cooling, hot water, fresh water, heated air for drying, and hydrogen. To generate these outputs, the present multigeneration system consists of six sub-plants, namely the Kalina cycle, hydrogen production subsystem, cooling cycle, drying process, fresh and hot water production plants. A parametric investigation and evaluation is carried out to show what manner direction different design parameters affect the system performance. Based on such comprehensive analysis and assessment study, the energetic efficiency for the integrated plant is found to be 59.93% while the exergetic efficiency is 57.18% which more truly reflects the practicality. Finally, the exergetic assessment results show that the Kalina cycle and the hydrogen generation plant have the maximum exergy destruction rates among other sub-plants of geothermal-based combined plant.

Novel two-stage fluidized bed-plasma gasification integrated with SOFC and chemical looping combustion for the high efficiency power generation from MSW: A thermodynamic investigation

A novel municipal solid waste (MSW)-based power generation system was proposed in this study, which consists of a bubbling fluidized-bed (BFB)-plasma gasification unit, a high-temperature solid oxide fuel cell (SOFC), a chemical looping combustion (CLC) unit and a heat recovery unit. Process simulation was conducted using Aspen Plus™ and validated by literature data. The energetic and exergetic assessment of the proposed system showed that the net electrical efficiency and exergy efficiency reached 40.9% and 36.1%, respectively with 99.3% of carbon dioxide being captured. It was found that the largest exergy destruction took place in the BFB-Plasma gasification unit (476.5 kW) and accounted for 33.6% of the total exergy destruction, followed by the SOFC (219.1 kW) and then CLC (208.6 kW). Moreover, the effects of key variables, such as steam to fuel ratio (STFR), fuel utilization factor (Uf), current density and air reactor operating temperature, etc., on system performance were carried out and revealed that the system efficiency could be optimized under STFR = 0.5, Uf = 0.8 and air reactor operating temperature of 1000 °C. Furthermore, the proposed process demonstrated more than 14% improvement in net electrical efficiency in comparison with other MSW incineration and/or gasification to power processes.

Comparative analysis of biorefinery designs based on acetone-butanol-ethanol fermentation under exergetic, techno-economic, and sensitivity analyses towards a sustainability perspective

Chemical process sustainability has been gaining attention as a comprehensive framework for diagnosing, optimizing, and improving a chemical design. This work presents a comprehensive assessment involving techno-economic, sensitivity, and exergetic factors of two biorefinery configurations for butanol production. The methodology presented here comprises three main steps for assessing biorefinery designs under a mixed techno-economic and exergetic assessment. Firstly, feedstock and processing units were selected based on the defined task (butanol production from lignocellulosic biomass). A general Acetone-Butanol-Ethanol (ABE) fermentation biorefinery was established considering (i) Pretreatment, (ii) Enzymatic hydrolysis, (iii) Fermentation, and (iv) Separation stages. The second step was the process modeling stages, in which biorefineries were simulated using Aspen Plus software, generating several quantitative data to perform economic and exergetic analyses. The last stage of the method is associated with the chemical process sustainability assessment based on techno-economic, sensitivity, and exergy analyses. Biobutanol topology 1 presented a production capacity of 32,737,45 kg/h butanol, while topology 2 generated 37,480 kg/h of this product. Both biorefinery designs had a biomass feed flow of 320,829 kg/h. The results revealed that both topologies were worthy alternatives from an economic viewpoint, considering the Net Present Value (NPV) 908.74 MM USD for topology 1, and 879.03 MM USD for topology 2. The Return on Investment (ROI) was 29.11% for topology 1 and 37.76% for topology 2. Regarding exergetic analysis, biobutanol topology 1 showed an exergy efficiency of 26.03%. In comparison, topology 2 gives an efficiency of 39.89%.

Air-to-water heat pump assessment: Part 1 – Experimental setup

This paper is part 1 of the investigation on the exergetic and exergoeconomic parameters of an existing system with an air-to-water heat pump unit as a heat source. Part 1 presents the used experimental setup. The main aim of the conducted experimental tests is to develop a model of produced heat transfer rate and energetic COP at different ambient conditions. The obtained data is used in Part 2 of the study where the exergetic and exergoeconomic assessment is carried out. The performance of the considered system is evaluated using Seasonal Exergy Efficiency. Moreover, Part 2 of the study has presented the formulation of the cost of the product, and cost allocation within the heat pump unit based on exergy.

Exergetic Assessment of a Newly Designed Solid Oxide Fuel Cell-Based System Combined with Propulsion Engine

Efficient, economic and environmentally friendly aircrafts and their operations have become the focus of research nowadays after the COVID-19 pandemic has spread around the world. This paper presents a combined solid oxide fuel cell with a turbofan engine system in order to improve the efficiency, cost and environmental performance. Two different analyses were conducted through analyses covering exergy and exergoeconomic aspects. Also, the paper investigates five alternative fuels with five fuel blends on the system performance. It is founded that the overall exergetic performance is the same among the five fuel blends of 82% exergetic efficiency and 18% exergy destruction ratio. In addition, using the methanol and hydrogen fuel blend appears to be the most economic way of achieving a relative cost difference of 38% and minimum price of electricity generation in the range of 108 to 621 $/GJ for turbines and SOFC. However, using dimethyl ether and hydrogen fuel blend becomes less favorable.

Modernizing Furnace Systems at Oil Refineries for Multifunctionality

At oil refineries, furnaces account for much of the energy expenditure. Energy efficiency may be improved by means of an integrated system that contains a furnace and a unit for heating the incoming gas with energy recovered from the smokestack gases. By exergetic analysis and efficiency assessment of the energy distribution in the system (on the basis of the zeroth law of thermodynamics), a multifunctional approach to effective integration of the furnace subsystem and the energy subsystem is proposed. That results in greater stability of the integrated system; provides the energy required for all the technological operations, as well as additional inexpensive electrical power; and helps curb thermal pollution of the environment. This approach may be adopted in modernizing existing systems or creating new systems.

Experimental analysis and exergetic assessment of the solar air collector with delta winglet vortex generators and baffles

To increase the efficiency of solar air collectors (SACs), the combined effects of baffles and delta winglet vortex generator (DWLVG) on the performance of SAC have been investigated. An experimental setup has been made, and numerical simulation is carried out in Ansys Fluent. The numerical investigation is validated by the experimental study and focused on the number of baffles as well as the number and the height of DWLVG. The results show that the SAC with no baffles and DWLVG has the lowest efficiency with the maximum value of 13%, while for SAC with six baffles and three pairs of DWLVG, the efficiency reaches up to 20%. The exergy analysis of three cases, SAC without baffles and DWLVG, SAC with six baffles without DWLVG, and SAC with six baffles and three pairs of DWLVG, shows that the maximum exergy efficiency of the SAC is 30.44% and occurs when the height ratio and the number of DWLVG pairs are 0.5 and 3. The results show that for SAC with six baffles and three pairs of DWLVG, the energy and exergy efficiency improve 7.4% and 12% on an average basis compared to the typical flat plate SAC, respectively. This improvement in thermal and exergy efficiency is due to the implementation of DWLVG which produces more turbulence and eliminates the vortices generated at the corners of SAC.

Exergetic Performance Assessment of Optimally Inclined BIPV Thermal System by Considering Cyclic Nature of Insolation

Abstract The structural and architectural elements of building-integrated photovoltaic-thermal (BIPVT) systems are made up of photovoltaic (PV) modules and these are required to be fixed at an optimum inclination angle for generating maximum exergy. This work presents an attempt to determine the amount of exergy generated by an optimally inclined double-storied BIPV thermal system by considering the actual cyclic nature of insolation, surrounding air temperature, PV cell temperature, intermediate slab temperature, and the chamber temperature. The insolation value, which is computed by an anisotropic sky model along with these cyclic variables, is used for solving the set of governing differential equations for evaluating the exergy of the system. Other influencing parameters of the BIPV thermal systems such as air changes in both chambers, packing factor of PV module, the orientation of PV module, and thickness of the intermediate slab are considered for finding its effect on the total exergy of the system. Numerical results show that for packing factor more than 0.6, there is no significant change in total heat exergy with respect to the inclination angle. For packing factor more than 0.3, the generation of electrical exergy exceeds the heat exergy, and the overall exergy of BIPVT system decreases with rise in packing factor (βm) up to 0.3 and then rises nonlinearly.

Regenerative Organic Rankine Cycle as Bottoming Cycle of an Industrial Gas Engine: Traditional and Advanced Exergetic Analysis

This investigation shows a traditional and advanced exergetic assessment of a waste heat recovery system based on recuperative ORC (organic Rankine cycle) as bottoming cycle of a 2 MW natural gas internal combustion engine. The advanced exergetic evaluation divides the study into two groups, the avoidable and unavoidable group and the endogenous and exogenous group. The first group provides information on the efficiency improvement potential of the components, and the second group determines the interaction between the components. A sensitivity analysis was achieved to assess the effect of condensing temperature, evaporator pinch, and pressure ratio with net power, thermal efficiencies, and exergetic efficiency for pentane, hexane, and octane as organic working fluids, where pentane obtained better energy and exergetic results. Furthermore, an advanced exergetic analysis showed that the components that had possibilities of improvement were the evaporator (19.14 kW) and the turbine (8.35 kW). Therefore, through the application of advanced exergetic analysis, strategies and opportunities for growth in the thermodynamic performance of the system can be identified through the avoidable percentage of destruction of exergy in components.

Dual-pressure condensation high temperature heat pump system for waste heat recovery: Energetic and exergetic assessment

High temperature heat pump (HTHP) is an energy-saving solution to recover the industrial waste heat. Five configurations of dual-pressure condensation HTHP are proposed and studied to improve thermal matching in the heat sink. The energy and exergy models are established, and the performance of dual-pressure condensation HTHP systems is assessed and compared with that of traditional single-stage, two-stage and cascade HTHP systems in detail. The results show that the dual-pressure condensation HTHP system is superior to traditional HTHP system from the perspective of energy efficiency and exergetic performance. A maximum COP is obtained at the optimum intermediate water temperature. The COP of dual-pressure condensation water-cooled saturated system (DWSAS) is the highest of 4.16, and 3.37–9.34% higher than the traditional HTHPs. R1234ze(Z) shows much higher energy efficiency over the other refrigerants for the applications of HTHP, and the COP is 2.62–4.47% larger than using R600a at the outlet temperature of heat source of 15–35 °C. The exergy destruction is also significantly reduced by using dual-pressure condensation HTHPs due to the improvement of thermal matching in the condensers. DWSAS shows the lowest exergy destruction, which is 4.28–19.35% lower than traditional HTHPs. DWSAS by using R1234ze(Z) is recommended due to its outstanding energetic and exergetic performance.

Comparative Energetic and Exergetic Assessment of Different Cooling Systems in Vegetable Cold Storage Applications

In this study, four different cooling systems have been thermodynamically analysed for vegetable cold storage application, considering a fixed cooling demand of 10 kW. Both vapour absorption refrigeration (VAR) and compression refrigeration (VCR) cycles are considered, each with two different working fluids. For the VCR cycles, R410A and R134a are considered as refrigerants, whereas for the VAR cycles, NH3–water and LiBr–water solutions are considered as refrigerant–absorbent pairs. Both energetic and exergetic performances are assessed and compared between the cycles. The system performances are assessed by varying the conditions of the evaporator and condenser. The effects of ambient temperature on the system performances are also studied. The study reveals that VAR systems can provide feasible alternatives to VCR systems for the cold space temperature range applicable for vegetable storage with the exception that LiBr–H2O cycle cannot be used for cold space temperature below 2 °C. Exergetic performance (ECOP) of the LiBr–H2O-based cooling system matches well with that of VCR systems for evaporator temperature 2–5 °C, and it exceeds the ECOP of R410A cycle at 2 °C evaporator temperature. When the ambient temperature is reached above 35 °C, the exergetic performance of LiBr–H2O-based system is better than that of both the VCR systems. For higher condenser temperature also (40 °C and above), the VAR and VCR cycles show closer ECOP values.

Exergetic Analysis of a New Direct Steam Generation Solar Plant Using Screw Expanders

Screw expanders are volumetric machines particularly suitable in energy conversion with steam–liquid mixtures and for the exploitation of low temperature heat sources. This study explored the main criteria to evaluate the thermodynamic advantages and exergetic assessment of an innovative solar electricity generation system: Screw expanders are utilized as power machines and parabolic trough collectors as a thermal source. Such a direct steam generation solar system, which is based on the Rankine cycle, offers benefits in comparison with usual power plants with dynamic expanders: The best exploitation of low temperature heat sources, satisfactory thermal efficiency with steam–liquid mixtures, lower evaporation pressures, and reduced size. Under real working conditions, screw expanders can work at part-load operating conditions; thus, the chief purpose of the present paper was to analyze the exergetic advantages of the planned solar power system when solar radiation and off-design working conditions fluctuate. Initially, the polytropic expansion phase with a specific numerical model is described to evaluate the energy losses that affect the thermodynamic performance of screw expanders when installed in the planned renewable energy power plant. Subsequently, to explore the exergy harnessing in the exhausted steam at off-design working conditions and then to appraise the maximum exergetic efficiency of the proposed screw expander-based solar thermal electricity plant, numerical optimization was performed in a broad range of evaporation and condensation temperatures.

Thermodynamics and energy usage of electric vehicles

The global number of electric vehicles is exponentially rising, due to strong marketing efforts and governmental incentives that significantly lower the price of new vehicles. This shift of consumers from internal combustion engine vehicles to electric vehicles is actually a shift from petroleum to the primary sources that generate electricity. The motivation for this paper is the holistic analysis of electric vehicles and the determination of their benefits and detriments. Starting with an exergetic assessment for all road vehicles, this paper determines the electricity needed for the propulsion of electric vehicles. When the heating and cooling requirements of the vehicle’s cabin are included, the range of the vehicles decreases significantly. The electricity requirements of the vehicles are abridged to primary energy sources using the concept of well-to-wheels efficiency. Based on the regional mix of electricity generation, the effect of the shift to electric vehicles on greenhouse gas emissions is determined. Because the charging of the batteries of electric vehicles requires significant power, it was concluded that the simultaneously charging of a number of vehicles will strain the capacity of the electricity grid. The paper also examines the effects of electric vehicles on the further utilization of renewable energy sources.

Energetic and exergetic assessments of a novel solar power tower based multigeneration system with hydrogen production and liquefaction

Abstract In this article, a thermodynamic investigation of solar power tower assisted multigeneration system with hydrogen production and liquefaction is presented for more environmentally-benign multigenerational outputs. The proposed multigeneration system is consisted of mainly eight sub-systems, such as a solar power tower, a high temperature solid oxide steam electrolyzer, a steam Rankine cycle with two turbines, a hydrogen generation and liquefaction cycle, a quadruple effect absorption cooling process, a drying process, a membrane distillation unit and a domestic hot water tank to supply hydrogen, electrical power, heating, cooling, dry products, fresh and hot water generation for a community. The energetic and exergetic efficiencies for the performance of the present multigeneration system are found as 65.17% and 62.35%, respectively. Also, numerous operating conditions and parameters of the systems and their effects on the respective energy and exergy efficiencies are investigated, evaluated and discussed in this study. A parametric study is carried out to analyze the impact of various system design indicators on the sub-systems, exergy destruction rates and exergetic efficiencies and COPs. In addition, the impacts of varying the ambient temperature and solar radiation intensity on the irreversibility and exergetic performance for the present multigeneration system and its components are investigated and evaluated comparatively. According to the modeling results, the solar irradiation intensity is found to be the most influential parameter among other conditions and factors on system performance.

Advanced Exergetic Assessment of a Vapor Compression Cycle With Alternative Refrigerants

The present study compares the thermal performance of various alternative refrigerants with conventional refrigerant operating on a vapor compression cycle with energetic, exergetic, and advanced exergetic approaches. Appropriate alternative refrigerants are selected for the analysis, and R1234yf is recommended as the best suitable refrigerant to replace the existing refrigerants. By splitting the exergy destruction into endogenous and unavoidable, endogenous and avoidable, exogenous and unavoidable, and exogenous and avoidable parts, an advanced exergy method depicts the real potentials for the improvement in the thermal system. Moreover, a traditional exergy method prefers condenser for performance improvement as it has 18.48% higher exergy destruction than evaporator, whereas the advanced exergy method proposes evaporator rather than condenser since its endogenous and avoidable destruction part is 26.38% more than condenser for R1234yf refrigerant.

CO2-utilization in the synthesis of methanol: Potential analysis and exergetic assessment

Carbon capture and utilization represents a major strategy to reduce anthropogenic CO2-emissions by valorization to chemical and petrochemical products. The integration of CO2 is not only aimed at abating emissions, but also at a partial substitution of raw materials, most of which are fossil fuels. In this context, Gas-to-Liquid processes are of great importance, in particular the production of methanol from its predominating feedstock natural gas. In the present study the CO2-utilization potential and impact of CO2-integration measures in methanol synthesis routes are investigated and assessed from a thermodynamic point of view. Sensitivity analyses for an estimation of the CO2-integration potential by dry reforming and direct hydrogenation are carried out. In a dry-reforming process, a carbon dioxide-to-methane mole ratio of one results from tradeoffs among the CH4-conversion, the desired syngas composition, and the heat demand.Regarding the direct hydrogenation, a CO2 inlet fraction of 10 mol-% is recommended for a pareto-optimal operation with a high product yield and a large conversion rate for CO2. The CO2-integration measures are implemented into three processes to evaluate and assess their effects on the overall systems by means of an exergetic analysis. The processes mainly differ in regard to the reforming technology and use conventional steam reforming, dry reforming by CO2, and mixed reforming. Compared to a conventional production process, the natural gas feed is successfully decreased by 38.7 t/h, 50.3 t/h and 61.4 t/h, while an amount of 191.5 kgCO2, 89.3 kgCO2, 425.8 kgCO2 per MWh total exergy of product can be abated, respectively. The process with mixed reforming exhibits a large exergetic efficiency of 48.6%, resulting from a careful integration of CO2 in conjunction with further syngas conditioning units. The processes with steam reforming and dry reforming have, however, lower efficiencies (31.1% and 39.8%, respectively) due to large irreversibilities within the furnace and the steam cycle, which result from the required large amounts for high-temperature process heat. The analyses show that the CO2 stream must be integrated carefully to the plant in order to avoid an excessive increase of the irreversibilities.

Entropy, Energy and Exergy for Measuring PW4000 Turbofan Sustainability

Abstract This study focuses on for a PW4000 high-bypass turbofan engine using energy, exergo-sustainable and performance viewpoint. For this aim, irreversibility and performance analyses are firstly performed for five main engine components at ≈260 kN maximum take-off thrust force. Besides, overall efficiency of the turbofan is determined to be 33 %, while propulsive and thermal efficiency of the turbofan are 72 % and 46 % respectively at 0.8 M and 288.15 K flight conditions. Secondly, calculation component-based exergetic assessment is carried out using exergetic indicators. According to the calculation, the exergetic efficiency of the engine is 32 %, while its waste exergy ratio is 0.678. Furthermore, exergetic sustainability measure is obtained as 0.473, while enviromental effect factor is 2.112. These indicators are also anticipated to help comprehend the connection between engine performance parameters and worldwide dimensions such as environmental effect and sustainable growth.