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The purpose of this study is to carry out energy and exergy analysis of fuels. Production of power and heat in industrialized countries is almost entirely based on combustion of fuels. Usually, combustion takes place in boilers or furnace; well-designed boilers have high thermal efficiencies of > 90 per cent. Even very high efficiencies, close to 100 per cent can be achieved depending on the applied fuel and boiler type. These high thermal efficiencies do suggest that combustion processes are highly optimized and do not need further improvements with regard to their thermodynamic performance. Second law (entropy or exergy) evaluations, however, shows that thermodynamic losses of boiler and furnaces are much larger than the thermal efficiencies do suggest. During combustion, air is predominantly used. When using air, the adiabatic combustion temperature depends only on the properties of fuel and air. The determining parameters for optimal fuel utilization are the fuel type, their composition and moisture content, the air temperature and air factor at combustion inlet.

Following assumptions are made for the analysis: calculation on the basis of 100 kg of dry and ash free fuel entering the control volume; fuel entering the control volume at T₀, P₀ and reacting completely with air entering separately at T₀, P₀ to form CO₂, SO₂, N₂ and H₂O, which exit separately at T₀, P₀ (T₀ = 298 K; P₀ = 1 atm); all heat transfer occurs at temperature T₀; and the chemical exergy of the ash has been ignored The availability change and the irreversibility for chemical reactions of hydrocarbon fuels were studied because fuel and dry air composed of O₂ and N₂ react to form products of combustion in the restricted dead state, and fuel and dry air composed of O₂ and N₂ react to form products of combustion which end up in the environmental (unrestricted) dead state. The difference between the above two statement, is the chemical availability of the product gases as they proceed from the restricted to the unrestricted dead state. These evaluations were made in terms of enthalpy and entropy values of the reacting species. T₀ extend these concepts to the most general situation, it is considered a steady-state control volume where the fuels enters at the restricted dead state, the air (oxidant) is drawn from the environment, and the products are returned to the unrestricted dead state.

It is evident from the analysis that an air factor of 1.10-1.20 is sufficient for liquid fuels, whereas solid fuels will require air factors of 1.15–1.3. When the temperatures of the products of combustion (T_p) are cooled down to that of T₀, the maximum reversible work occurs. From the analysis, it is clear that the rather low combustion temperature and the need for cooling down the flue gases to extract the required heat are the main causes of the large exergy losses. The maximum second law efficiency also occurs when T_p is set equal to T₀. The maximum second law efficiency per kilo mole of fuel is found to be 73 per cent, i.e. 73 per cent of the energy released by the cooling process could theoretically be converted into useful work. It is evident that reducing exergy losses of combustion is only useful if the heat transferred from the flue gas is used at high temperatures. Otherwise, a reduction of exergy loss of combustion will only increase the exergy loss of heat transfer to the power cycle or heat-absorbing process. The exergy loss of combustion can be reduced considerable by preheating combustion air. Higher preheat temperatures can be obtained by using the flue gas flow only for preheating air. The remainder of the flue gas flow can be used for heat transfer to a power cycle or heat-absorbing process. Even with very high air preheat temperatures, exergy losses of combustion are still > 20 per cent. The application of electrochemical conversion of fuel, as is realized in fuel cells, allows for much lower exergy loses for the reaction between fuel and air than thermal conversion. For industrial applications, electrochemical conversion is not yet available, but will be an interesting option for the future.

The outcome of the study would certainly be an eye-opener for all the stakeholders in thermal power plants for considering the second law efficiency and to mitigate the irreversibilities.

This study aims to introduce exergy analysis of a three-spool turboprop engine during the complete flight.

In this study, a flight scenario of the aircraft is assumed. Operating parameters of the aircraft and its engine are modelled based on the assumed flight scenario with the aid of a genuine code. And then performance analysis of the engine is performed for each flight path point with the aid of exergy.

At the end of the study, major exergy parameters of the engine are calculated during the complete flight of a cargo aircraft three-spool turboprop engine.

Findings of the study may be beneficial for industry and practitioners to improve performance of the evaluated engine.

To the best of authors’ knowledge, this paper presented the exergy analysis of a three-spool turboprop engine during the complete flight for the first time. It was shown how the exergy destruction rate depends on the altitude and manoeuvre.

This study aims to use an environomics method to assess the environmental impacts of selected gas turbine power plants in Nigeria.

In this study, exergoenvironomic analysis has been carried out to investigate the environmental impact of selected gas turbine power plants in Nigeria from an exergetic point of view.

The exergy analysis reveals that the combustion chamber is the most exergy destructive component compared to other cycle components. The exergy destruction of this component can be reduced by increasing gas turbine inlet temperature (GTIT). The results of the study show that thermodynamic inefficiency is responsible for the environmental impact associated with gas turbine components. The study further shows that CO₂ emissions and cost of environmental impact decrease with increasing GTIT.

The exergo-environomic parameters computed in this study are CO₂ emission in kg per MWh of electricity generated, depletion number, sustainability index, cost flow rate of environmental impacts (Ċ_env) in $/h and total cost rates of products (Ċ_Tot) in $/hr. For the period considered, the CO₂ emissions for the selected plants vary from 100.18 to 408.78 kgCO₂/MWhm, while cost flow rate of environmental impacts varies from $40.18 /h to $276.97 /h and the total cost rates of products vary from $2935.69/h to $12,232.84/h. The depletion number and sustainability index vary from 0.69 to 0.84 and 1.20 to 1.44, respectively.

This study aims to investigate the aviation, energetic, exergetic, environmental, sustainability and exergoeconomic performances of a micro turbojet engine used in unmanned aerial vehicles at four different modes.

The engine data were collected from engine test cell. The engine performance calculations were performed for four different operation modes.

According to the results, maximum energy and exergy efficiency were acquired as 19.19% and 18.079% at Mode 4. Total cost rate was calculated as 6.757 $/h at Mode-1, which varied to 10.131 $/h at Mode-4. Exergy cost of engine power was observed as 0.249 $/MJ at Mode-1, which decreased to 0.088 $/MJ at Mode-4 after a careful exergoeconomic analysis.

The novelty of this work is the capability to serve as a guide for similar systems with a detailed approach in the thermodynamic, thermoeconomic and environmental assessments by prioritizing efficiency, fuel consumption and cost formation. This investigation intends to establish a design of the opportunities and benefits that the thermodynamic approach provides to turbojet engine systems.

It is essential to develop more environment-friendly energy systems to prevent climate change and minimize environmental impact. Within this scope, many studies are performed on performance and environmental assessments of many types of energy systems. This paper, different from previous studies, aims to prove exergy performance of a low-emission combustor of an aero-engine.

It is a well-known fact that, with respect to previous exergy analysis, highest exergy destruction occurs in the combustor component of the engine. For this reason, it is required to evaluate a low-emission aero-engine combustor thermodynamically to understand the state of the art according to the authors’ best of knowledge. In this framework, combustor has been operated at numerous conditions (variable engine load) and evaluated.

As a conclusion of the study, the impact of emission reduction on performance improvement of the aero-engine combustors exergetically is presented. It is stated that exergy efficiency of the low-emission aero-engine combustor is found to be 64.69, 61.95 and 71.97 per cent under various operating conditions.

Results obtained in this paper may be beneficial for researchers who are interested in combustion and propulsion technology and thermal sciences.

Different from former studies, the impact of operating conditions on performance of a combustor is examined from the viewpoint of thermodynamics.

This paper aims to present an analytical investigation of energy and exergy performance on a solar flat plate collector (SFPC) with Cu-CuO/water hybrid nanofluid, Cu/water and CuO/water nanofluids as collector running fluids.

Heat transfer characteristics, pressure drop and energy and exergy efficiencies of SFPC working on these nanofluids are investigated and compared. In this study, a comparison is made by varying the mass flow rates and nanoparticle volume concentration. Thermophysical properties of hybrid nanofluids are estimated using distinctive correlations available in the open literature. Then, the influence of these properties on energy and exergy efficiencies of SFPC is discussed in detail.

Energy analysis reveals that by introducing the hybrid nanoparticles in water, the thermal conductivity of the working fluid is enhanced by 17.52 per cent and that of the individual constituents is enhanced by 15.72 and 15.35 per cent for Cu/water and CuO/water nanofluids, respectively. This resulted in 2.16 per cent improvement in useful heat gain for hybrid nanofluid and 1.03 and 0.91 per cent improvement in heat gain for Cu/water and CuO/water nanofluids, respectively. In line with the above, the collector efficiency increased by 2.175 per cent for the hybrid nanofluid and 0.93 and 1.05 per cent enhancement for Cu/water and CuO/water nanofluids, respectively. Exergy analysis elucidates that by using the hybrid nanofluid, exergy efficiency is increased by 2.59 per cent, whereas it is 2.32 and 2.18 per cent enhancement for Cu/water and CuO/water nanofluids, respectively. Entropy generation is reduced by 3.31, 2.35 and 2.96 per cent for Cu-CuO/water, Cu/water and CuO/water nanofluids, respectively, as compared to water.

However, this is associated with a penalty of increment in pressure drop of 2.92, 3.09 and 2.74 per cent for Cu-CuO/water, Cu/water and CuO/water nanofluids, respectively, compared with water.

It is clear from the analysis that Cu-CuO/water hybrid nanofluids possess notable increment in both energy and exergy efficiencies to use them in SFPCs.

This study aims to present the numerical analysis of exergy transfer and irreversibility through the discrete filling of high-porosity aluminum metal foams inside the horizontal pipe.

In this study, the heater is embedded on the pipe’s circumference and is assigned with known heat input. To enhance the heat transfer, metal foam of 10 pores per inch with porosity 0.95 is filled into the pipe. In filling, two kinds of arrangements are made, in the first arrangement, the metal foam is filled adjacent to the inner wall of the pipe [Model (1)–(3)], and in the second arrangement, the foam is located at the center of the pipe [Models (4)–(6)]. So, six different models are examined in this research for a fluid velocity ranging from 0.7 to7 m/s under turbulent flow conditions. Darcy Extended Forchheimer is combined with local thermal non-equilibrium models for forecasting the flow and heat transfer features via metal foams.

The numerical methodology implemented in this study is confirmed by comparing the outcomes with the experimental outcomes accessible in the literature and found a fairly good agreement between them. The application of the second law of thermodynamics via metal foams is the novelty of current investigation. The evaluation of thermodynamic performance includes the parameters such as mean exergy-based Nusselt number (Nu_e), rate of irreversibility, irreversibility distribution ratio (I_DR), merit function (MF) and non-dimensional exergy destruction (I^*). In all the phases, Models (1)–(3) exhibit better performance than Models (4)–(6).

The present study helps to enhance the heat transfer performance with the introduction of metal foams and reveals the importance of available energy (exergy) in the system which helps in arriving at optimum design criteria for the thermal system.

The uniqueness of this study is to analyze the impact of discrete metal foam filling on exergy and irreversibility in a pipe under turbulent flow conditions.

The study aims to verify and establish the result of the most suitable optimization approach for higher performance and lower emission of a variable compression ratio (VCR) diesel engine. In this study, three types of test fuels are taken and tested in a variable compression ratio diesel engine (compression ignition). The fuels used are conventional diesel fuel, e-diesel (85% diesel-15% bioethanol) and nano-fuel (85% diesel-15% bioethanol-25 ppm Al₂O₃). The effect of bioethanol and nano-particles on performance, emission and cost-effectiveness is investigated at different load and compression ratios (CRs). The optimum performance and lower emission of the engine are evaluated and compared with other optimization methods.

The test engine is run by diesel, e-diesel (85% diesel-15% bioethanol) and nano-fuel (85% diesel-15% bioethanol-25 ppm Al₂O₃) in three different loadings (4 kg, 8 kg and 12 kg) and CR of 14, 16 and 18, respectively. The optimum value of energy efficiency, exergy efficiency, NO_X emission and relative cost variation are determined against the input parameters using Taguchi-Grey method and confirmed by response surface methodology (RSM) technique.

Using Taguchi-Grey method, the maximum energy and exergy efficiency, minimum % relative cost variation and NO_X emission are 24.64%, 59.52%, 0 and 184 ppm, respectively, at 4 kg load, 18 CR and fuel type of nano-fuel. Using RSM technique, maximum energy and exergy efficiency are 24.8% and 62.9%, and minimum NO_X emission and % cost variation are 208.4 ppm and –6.5, respectively, at 5.2 kg load, 18 CR and nano-fuel. The RSM is suggested as the most appropriate technique for obtaining maximum energy and exergy efficiency, and minimum % relative cost; however, for lowest possible NO_X emission, the Taguchi-Grey method is the most appropriate.

Waste rice straw is used to produce bioethanol. 4-E analysis, i.e. energy, exergy, emission and economic analysis, has been carried out, optimized and compared.

The purpose of this paper is to create models that predict exergetic sustainability index (ESI) and environmental effect factor (EEF) values with high accuracy according to various engine parameters.

In this study, models were created to estimate ESI and EEF sustainability parameters in various flight phases for a business jet with a turboprop engine using the cuckoo search algorithm (CSA) method. The database used for modeling includes the various engine parameters (torque, engine airflow, gas generator speed, fuel mass flow, power and air-fuel ratio) obtained by running a business aircraft engine more than once at different settings and the actual ESI and EEF values obtained depending on these parameters. In addition, sensitivity analysis was performed to measure the effect of engine parameters on the models. Finally, the effect of the CSA number of nest (n) parameter on the model accuracy was investigated.

It has been observed that the models predict ESI and EEF values with high accuracy. As a result of the sensitivity analysis, it was seen that the air-fuel ratio had a greater effect on the output parameters.

These models are thought to assist in the exergetic environment analysis used to find the greatest losses for turboprop business jets and identify their causes and further improve system performance. Thus, they will be a useful tool to minimize the negative impact of business jet on environmental sustainability.

To the best of the authors’ knowledge, this study stands out in the literature because it is the first exergo-metaheuristic approach developed with CSA for business aircraft engine; moreover, the data set used consists of real values.

Nanotechnology has developed gradually in recent years and it is encountered in various applications. It has many usage area especially in energy systems. The purpose of this study, in a photovoltaic thermal system, thermal behaviours of a PV panel has been investigated by energy and exergy analysis method using a phase change material inserted 5 per cent weighted Al₂O₃ nanoparticle.

In this study, one of the three different PV panels was kept normally, the other one was filled with a phase changing material (paraffin-wax) and the last panel was filled with the mixture of a nanoparticle and paraffin-wax.

After the analyses, especially during the time intervals when the radiation is high, it is found that the panel with Np-paraffin mixture has a high electrical and thermal efficiency. In addition, as a result of the exergy analyses, average exergy efficiency of the panel with Np-paraffin mixture has been determined as 10 per cent, whereas that of the panel with paraffin as 9.2 per cent.

Nanoparticles had not been used with PCMs in photovoltaic–thermal systems in the studies made before.