Power Exergy Research Articles

The Exergy and Energy Analysis of Change Phase Steam in Patuha Geothermal Well Production

A Geothermal Power Plant Company in West Java Indonesia have capacity around 55MW. It company have increased the well production quality to keep up the Indonesia's energy demands. The power plant has been operated around ten years, it has ten geothermal production wells and two injection wells. The either of it wells has an abnormality. It wells has water dominated condition so, the separator equipment is required to separate the steam from water and vapor. Previous study indicated that subsurface water entering the broken reservoir pipe. That leaks in reservoir pipe was repaired in 2020. The impact after the pipe have been repaired it made the fluid characteristic of reservoir be vapor dominated. After that a separator as a steam separator is no longer required. The study compares the value energy and exergy power of the power plant. The calculations are performed from the well reservoir and all power plant equipment. According to the results of the energy study, the plant's energy efficiency after the transformation increased by 0.03%, from 19.48% to 19.52%. The exergy value of the brine in either wells (separated steam cycle) is also known to be 2.512,52 kW, beyond which the value will become zero.

Thermodynamic improvements of LNG cold exergy power generation system by using supercritical ORC with unconventional condenser

Organic Rankine cycle (ORC) is the most commonly used power generation cycle that is adopted in this paper to make full use of the cold exergy of liquefied natural gas (LNG). As the heat exchangers are mainly responsible for the exergy destruction of the system, two improvement techniques: supercritical system and unconventional condenser, are proposed to decrease the exergy destructions in steam generator and condenser. The performances of ten preselected working fluids are tested by optimizing five key parameters at three heat source temperatures. The results show that using the supercritical system can improve the system efficiency for fluids with low critical temperatures by reducing the exergy destructions in steam generators. Using the unconventional condenser can greatly improve the system efficiency by decreasing the exergy destruction during the LNG regasification process of most fluids, barring a few wet expansion fluids. The improvements offered by both techniques become more obvious as the heat source temperature increases. However, combining the two techniques only improves the performance for fluids with low critical temperatures, and does not work for most fluids. The highest efficiency is always achieved by the subcritical system with an unconventional condenser at each heat source temperature. When the heat source temperatures are 100 °C and 150 °C, R290 obtains the highest efficiency values of 17.89% and 21.26%, respectively. At 200 °C, R600a achieves the highest efficiency of 25.35%.

Investigations of energy, exergy distribution characteristics of overall working conditions and effect of key boundary parameters on residual energy availability in an automotive turbocharged diesel engine

In this paper, an automotive turbocharged diesel engine was employed to explore energy, exergy distribution characteristics at overall working conditions and key boundary parameters influence on residual energy availability based on test, simulation and theoretical calculation means. The results show that first, low efficiency regions coincide basically with low load regions, while higher efficiency regions are mostly concentrated in higher load regions at medium speed. Secondly, exhaust energy power and exhaust exergy power are positively correlated with load and speed, speed has a greater impact on exhaust energy percentage than load, but a less influence on exhaust exergy percentage. Third, heat transfer energy power and exergy power are positively correlated with load and speed in medium-low output power working conditions, but remain basically unchanged in high output power working conditions. Fourth, high exergy destruction regions are all located in low load regions, exergy destruction degree increases gradually from inside to outside in combustion chamber, EDR (exergy destruction rate) peak value is acquired around theoretical ER (fuel-air equivalent ratio), EDR increases with ER raising in dilute mixing zone. Finally, REAC (residual energy availability coefficient) of exhaust and heat transfer are almost positively correlated with load, measures to decrease REAC are basically parallel with enhancing efficiency by key boundary parameters adjustment.

Experimental investigation of solar cooking system based on evacuated tube solar collector for the preparation of concentrated sugarcane juice used in jaggery making

An experimental investigation of a solar cooking system has been performed for the preparation of concentrated sugarcane juice required in jaggery making. An evacuated tube solar collector has been used as a heat collecting medium. Experiments have been performed on sunny and clear sky days by taking the cooking loads of 1, 1.5 and 2 L of sugarcane juice. To predict the thermal performance of solar cooking system, an exergy-based approach is employed. The obtained results have been compared with the other solar cooking systems considering performance factors like peak exergy power and product of the peak exergy power value with the temperature difference gap. The maximum value of peak exergy power and the product of temperature difference gap with peak exergy output value is observed maximum for the 2 L of cooking load. A percentage increase of 76% and 59% in the value of peak exergy for the presented system is observed with reference to the peak exergy power for the box-type and parabolic trough-type solar cooker design, respectively. Furthermore, 53.3% rise in the time taken is observed for the cooking load of 2 L with respect to 1 L of cooking load. The results from the present study emphasized that evacuated tube-based solar cooking system has the potential to maintain the temperature of sugarcane juice above its boiling point temperature even in low solar intensity hours.

EXERGY ANALYSIS ON THERMAL POWER PLANT PT. MAKASSAR TENE USING CYCLE-TEMPO 5

Analyzing exergy on the power plant generating system specially at PLTU, efficient utilization of energy resources can be obtained particularly since it leads efforts to reduce energy waste that already exists.The purposes of this research are to get the Thermal Power Plant system modeling of PT. Makassar Tene, to get the value of modeled exergy power plant system, to get exergy losses, to get the amount exergy efficiency and to get the cost of exergy losses.The research method was firstly, designing the Power Plant generating systems PT. Makassar Tene using Cycle-Tempo 5 as thermodynamic analysis tool. Results of calculations were then used to calculate the exergy profile.Exergy values analyzed on a system modeled Power Plant consists of turbine components, condensers and pump. Boilers are not included in the analysis because of the input device is not contained and the mass flow rate of the boiler occurs steady state in which the state of the same process with the state of the environment so that there is no exergy difference that can be utilized.The highest exergy losses based on the modelling was on the turbine components that was 10201.50 kW. This was due to the change in the vapor phase into the liquid phase contained in the component before and after leaving the turbine components. While the lowest exergy losses was on the pump component, that was 437.18 kW.The higher the efficiency value of a component, the better its performance is. The highest efficiency value of exergy that was 51.43% contained on the turbine components. While the lowest efficiency value of exergy was 0%.

Ексергетичні втрати в повітронагрівачі теплоутилізаційної системи котельної установки

Однією з причин зниження ефективності теплоутилізаційних систем та їх окремих елементів є втрати ексергетичної потужності. Такі втрати пов'язані з гідродинамічним опором при русі теплоносіїв, з незворотними процесами при теплообміні між теплоносіями, з процесами теплопровідності. Зниження втрат ексергетичної потужності дає змогу підвищити ефективність теплоутилізаційних систем. Це визначає актуальність робіт, присвячених вирішенню зазначеної проблеми. Для розрахунку втрат ексергетичної потужності в теплоутилізаційних системах та їх окремих елементах розроблено комплексну методику, яка поєднує ексергетичні методи з методами, побудованими на розрахунку дисипаторів ексергії. Розроблена методика дає змогу розділити втрати ексергетичної потужності згідно з причинами та зонами їх локалізації і виявити умови, за яких ці втрати будуть мінімальними. Основні етапи методики включають розробку математичної моделі досліджуваних процесів на основі рівняння ексергії, рівнянь балансів ентропії і ексергії, рівняння нерозривності, рівняння для внутрішньої енергії. У межах розробленої математичної моделі отримано диференціальні рівняння ентропії та ексергії і формули для розрахунку дисипаторів ексергії, що характеризують гідродинамічні втрати і втрати ексергетичної потужності внаслідок нерівноважного теплообміну між теплоносіями. Визначено значення дисипаторів ексергії для пластинчастого повітронагрівача теплоутилізаційної системи котельної установки за різних режимів роботи котла. Встановлено внесок кожного виду втрат у сумарні втрати ексергетичної потужності у повітронагрівачі і визначено область максимальних втрат цієї потужності.

COMPREHENSIVE METHODS OF EVALUATION OF EFFICIENCY AND OPTIMIZATION OF HEAT-UTILIZATION SYSTEMS

At present, Ukraine has the necessary potential for the implementation of effective energy-saving technologies for heat recovery, and therefore the problem of their development and implementation is relevant for the country's energy sector. The solution of this problem is related to the need for systematic studies of the efficiency of optimization of heat recovery facilities from the standpoint of modern methodological approaches. The paper outlines the main stages in the development of integrated methods for assessing the efficiency and optimization of heat recovery systems based on the principles of exergic analysis, statistical methods for planning the experiment, structured variational methods, multilevel optimization methods, the theory of linear systems and the thermodynamics of irreversible processes. Examples and illustrations illustrate some of the stages in the development of complex methods. The necessary general step in the development of methodologies is the development of new performance criteria. Such criteria are highly sensitive to changes in the regime and design parameters of heat recovery systems due to the inclusion of some exergic characteristics in them. The developed criteria also serve as target optimization functions. For individual elements of heat recovery systems, efficiency and optimization methods usually include the definition of the functional dependencies of the selected efficiency criteria on the main parameters. For this, balance methods of exergic analysis and statistical methods of experiment planning are used. If such dependencies are established, optimization is carried out using known mathematical methods. For complex heat recovery systems involving a large number of elements, it is not possible to establish general analytical dependencies of the optimization objective functions on the parameters of the system when constructing mathematical models necessary for their optimization. Complex methods based on the basic principles of structural-variant methods, methods of multilevel optimization, the theory of linear systems, and the thermodynamics of irreversible processes have been developed for such cases. For this purpose, structural diagrams of plants, block diagrams of multi-level optimization have been developed, complete input matrices have been constructed, mathematical models for the processes under investigation have been developed, formulas have been derived for calculating the loss of exergy power in heat conduction processes and formulas for calculating dissipators of exergy. A well-founded choice of the methodology for evaluating efficiency and optimization raises the effectiveness of optimization, since it allows the use of parameters maximally close to optimal when developing the heat recovery system design, which in turn increases the efficiency of the system. References 14, figures 5.

Turbogenerator Steam Turbine Variation in Developed Power: Analysis of Exergy Efficiency and Exergy Destruction Change

Developed power variation of turbogenerator (TG) steam turbine, which operates at the conventional LNG carrier, allows insight into the change in turbine exergy efficiency and exergy destruction during the increase in turbine power. Measurements of required operating parameters were performed in eight different TG steam turbine operating points during exploitation. Turbine exergy efficiency increases from turbine power of 500 kW up to 2700 kW, and maximum exergy efficiency was obtained at 70.13% of maximum turbine developed power (at 2700 kW) in each operating point. From turbine developed power of 2700 kW until the maximum power of 3850 kW, exergy efficiency decreases. Obtained change in TG turbine exergy efficiency is caused by an uneven intensity of increase in turbine developed power and steam mass flow through the turbine. TG steam turbine exergy destruction change is directly proportional to turbine load and to steam mass flow through the turbine—higher steam mass flow results in a higher turbine load which leads to the higher exergy destruction and vice versa. The higher share of turbine developed power and the lower share of turbine exergy destruction in the TG turbine exergy power inlet lead to higher turbine exergy efficiencies. At each observed operating point, turbine exergy efficiency in exploitation is lower when compared to the maximum obtained one for 8.39% to 12.03%.

ЕФЕКТИВНІСТЬ ПЛАСТИНЧАТИХ ТЕПЛОУТИЛІЗАТОРІВ ТЕПЛОУТИЛІЗАЦІЙНИХ СИСТЕМ

Розроблено методику розрахунку втрат ексергетичної потужності у процесах теплопровідності під час передачі теплоти через поперечний переріз пластини газоповітряного пластинчастого теплоутилізатора за граничних умов третього роду. Методику засновано на комплексному підході, що поєднує ексергетичні методи з методами термодинаміки незворотних процесів. Математична модель досліджуваних процесів включає рівняння ексергії, рівняння балансу ексергії та ентропії, рівняння нерозривності трифазної термодинамічної системи при зміні концентрації однієї з фаз, рівняння руху фаз, рівняння енергій, рівняння балансу ентальпій, рівняння Гіббса і рівняння теплопровідності за граничних умов третього роду. Для отримання формул для розрахунку втрат ексергетичної потужності використано локальне диференціальне рівняння балансу ексергії. У цьому рівнянні одна зі складових визначає втрати ексергетичної потужності, зумовлені незворотністю процесів і пов'язані з теплопровідністю, в'язкістю фаз, міжфазним теплообміном і тертям між фазами. На підставі цього рівняння і рішення рівняння теплопровідності за граничних умов третього роду для необмеженої пластини, якою моделювалася пластина газоповітряного пластинчастого теплоутилізатора, отримано формули для розрахунку втрат ексергетичної потужності. Виконано розрахунки загальних втрат ексергетичної потужності в газоповітряному пластинчастому теплоутилізаторі за різних режимів роботи котла і втрат ексергетичної потужності у процесах теплопровідності. Встановлено, що втрати ексергетичної потужності у процесах теплопровідності в газоповітряному пластинчатому теплоутилізаторі становлять 8,6-11,6 % від загальних втрат ексергетичної потужності і залежать від режиму роботи котла.

Integrated circular economy and education model to address aspects of an energy-water-food nexus in a dairy facility and local contexts

Universities have responsibilities for accelerating pedagogical innovation to enable a more sustainable future. This research work develops a three-phased approach for integrating principles of a circular economy system within a course in energy policy. The phases involve scanning available resources, identifying possible matches based on the quality of energy, namely exergy, and determining solution areas. The case study is a university-founded dairy facility in the province of Ankara, Turkey with a biogas production potential of 982 m3 per day. Four scenarios are analyzed based on options for combined heat and power, organic Rankine cycle, waste heat recovery, absorption chillers, ground source heat pumps, photovoltaic thermal arrays, and/or low-speed wind turbines. In total, 184.1 kWe of high exergy power and 285.3 kWt of low exergy thermal power may be produced. Further evaluation of the scenarios indicates that the level of exergy match may reach 0.87 while primary energy and primary exergy savings over separate energy production from renewables may be 38% and 61%, respectively. The solution areas can address aspects of an energy, water, and food nexus based on energy from waste, energy for irrigation and agriculture, and other linkages. The results are used to engage students in advancing the Sustainable Energy Action Plans of local municipalities. The approach has applicability to other cases in a time when pedagogical innovation is urgently needed to stimulate environmental sustainability.

Impact of load variation on the energy and exergy efficiencies of a single vacuum tube based solar cooker

A single vacuum tube based solar cooker has high energy and exergy efficiency, and is capable of achieving cooking temperatures as high as 250 °C. The reason for high energy and exergy efficiencies of this solar cooker is the high achievable concentration ratios of 15–20, which are not possible with multiple vacuum tube based solar cookers. In this paper, a comparative study has been carried out to experimentally determine the impact of varying the load on the various performance measuring parameters. Five experiments have been carried out with 3, 4, 5, 6 and 7 kg of respective water loads. Performance measuring parameters including the energy and exergy efficiencies, heat loss coefficient, quality factor, adjusted quality factor, peak exergy power, and peak exergy power to temperature difference gap product have been determined for each case. It is concluded that the performance measuring parameters have correlation with the load on the solar cooker. Performance parameters indicate average peak exergy power of 51.07 W, while the product of temperature difference gap at half power to that of peak exergy power is about 3000 W K. The highest value of the quality factor was found to be 0.0506 with 6 kg of water load.

A review of vacuum tube based solar cookers with the experimental determination of energy and exergy efficiencies of a single vacuum tube based prototype

Abstract Solar cookers may be generally classified into direct and indirect types. The direct types include the box type and parabolic type, while the indirect types include the vacuum tube based cookers. This paper reviews the gradual progress made in the second type. The energy and exergy analysis of a single vacuum tube based prototype has been carried out experimentally. Performance parameters indicate a high peak exergy power of 55.6 W, while the temperature difference gap at half power is 38.75 K and the quality factor is 0.042. The energy efficiency of the cooker is 20–30%, while the exergy efficiency is 4–6%. These results make this compact single family solar cooker comparable in performance to large community based Scheffer type solar cookers. Results have been compared to a number of other solar cooker types.

Effect of load variations on exergy performance of solar box type cooker

In recent times, performing the exergy based analysis on solar cookers has gained momentum. It has been observed that the variations in exergy output power and exergy power lost with temperature difference are qualitatively similar in nature for various topological designs of solar cookers. In the present manuscript, variations in the exergy power output and exergy power lost with temperature difference for different loads/mass of water have been reported for solar box type cooker. The four different benchmark parameters, viz., heat loss coefficient, quality factor, peak exergy, and exergy temperature difference gap product are determined for each case. The mutual dependence of these parameters and the conceptual understanding of their variations with different load of water are explained. The adjusted value of the quality factor has been found to be independent of the mass of water kept inside the cooker during full load tests. The findings also confirm the earlier reports in terms of qualitative response and strengthen the case of exergy based test protocol for solar cookers.

An exergy based unified test protocol for solar cookers of different geometries

It is beneficial for the consumer to have solar cookers of various varieties in terms of geometrical designs, performance and price but it is also a challenge to develop a uniform test standard for evaluating the thermal performance of the cookers irrespective of their geometrical construction. In this paper, four exergy based parameters, are proposed for solar cookers of different topological design, as their thermal performance indicators. To this end, graphs between exergy output power and temperature difference are plotted, and they resemble a parabolic curve for each design. The peak exergy (vertex of the parabola), can be accepted as a measure of devices’ fuel ratings. The ratio of the peak exergy power gained to the exergy power lost at that instant of time can be considered as the quality factor of the solar cooker. Besides, the exergy power lost is found to vary linearly with temperature difference irrespective of the topology of the device and the slope of the straight line obtained through curve fitting represents the heat loss coefficient of the cooker. The proposed parameters can lead to development of unified test protocol for solar cookers of diversified designs.

Exergy efficiency optimization of a thermoacoustic engine with a complex heat transfer exponent

On the basis of exergetic analysis, the performance analysis and optimization of a generalized irreversible thermoacoustic engine with heat resistance, heat leakage, thermal relaxation and internal dissipation, in which heat transfer between the working fluid and heat reservoirs obeys a complex generalized heat transfer law , where n is a complex, is investigated by taking exergetic efficiency as the optimization objective using finite-time thermodynamics. Both the real part and the imaginary part of the complex heat transfer exponent change the optimal exergy efficiency versus power output relationship. Analytical formulas for the exergy efficiency, power output and thermal efficiency of the thermoacoustic engine are derived. Furthermore, comparative analyses of the influences of various factors on optimal performance of the generalized irreversible thermoacoustic engine are carried out with detailed numerical examples. The optimal zone on the performance of the thermoacoustic engine is obtained by numerical analysis. The results obtained herein can provide some theoretical guidelines for the design of a real thermoacoustic engine.

Exergy analysis of a combined fuel cell and Gas Turbine Power Plant with intercooling and reheating

This paper presents a comparative exergy study of the performance of various gas turbine power generation plants and a high temperature Solid Oxide Fuel Cell (SOFC). The overall system is analysed and its exergy efficiency and exergy destruction are obtained, as well as individual models of each component. The results for selected operating conditions are compared against past literature data. Comparisons are presented in terms of thermal and exergy efficiencies, net power and exergy destruction rate, vs. the compression ratio and Turbine Inlet Temperature (TIT). It is found that integrating a conventional GT plant with an SOFC can nearly double the efficiency of the cycle.

Thermodynamic bounds for food deep chilling tray tunnel operation

In this paper a thermodynamically guided intensification method on tray tunnels for food deep chilling is presented. Two indicators of the performance of the system are used: the exergy power and the destruction of specific exergy. The objective function corresponds to the maximization of the exergy power and the minimization of the specific exergy destruction. Exergy has the main advantage to take into consideration both the food mass flow rate and its output temperature level. The food mass flow rate stands for its quantity whereas the temperature level represents its quality. An endoreversible model is also presented in conjunction with a simple mathematical description of the refrigeration cycle internal irreversibilities. A numerical investigation against operation variables permits to find the so-called intensification zone that defines bounds for food mass flow rate and output temperature as well as for the refrigeration cycle evaporator temperature.

EXERGY TRANSFER ANALYSIS FOR CENTRIFUGAL COMPRESSED HIGH POWER HEAT PUMP DEVICE

According to exergy transfer theory, establishment of the exergy transfer mode of unit and device for an online high power centrifugal compressed heat pump is focused on. Some criterions to analyze and evaluate the devices and equipments such as exergy exchange rate, exergy power degressive rate, exergy fluid density degressive rate, and exergy resistance coefficient are raised and defined. The calculation formulas for each criterion are presented also. Using these model and criterions, through an exergy transfer analysis on the energy quality activities during the process of the energy exchange and transfer in the heat pump, the results show that exergy power degressive rate is the highest in throttle and compressor because the flow speed and flow state have the instant drastic changes in the process of flow throttle, which cause the significant loss of exergy, and some deficiencies exist for the compressor mechanism performance and thermophysical properties of refrigerants performance. The exergy resistance coefficient is the highest in evaporator, which reflects that the structure design has the distinct limitation. Exergy power degressive rate and exergy fluid density degressive rate have the same value in the throttle which indicate that the structure factors of the equipment and the time conditions have the same impacts on the throttle. The results of exergy transfer analysis reveal the influence degree of structure design and thermodynamics property of the main equipment, and thermophysical properties of refrigerants impact the process of energy usage in the devices, and indicate the structure design of compressor can be improved further. The method by flow throttling and intensity of pressure decreasing is not appropriate in terms of the significant impacts on the rational energy usage of the devices; the primary problem of the evaporator is caused by the refrigerant factor but not its structure design. From the calculation of the energy analysis and exergy analysis on the devices, it is indicated that energy analysis only reflects the quantitative energy utilizing, and exergy analysis is only the static analysis of energy activities. However, in terms of the dynamic analysis, exergy transfer analysis provides the new information including not only the design parameters for the heat pump device and principle equipments, but also the impacts on the performance of energy usage under the situation with the random running of the equipment system. Therefore, it can provide the detailed suggestions to improve on the heat pump unit designs and direct the device operation.