Thermal Efficiency Analysis Research Articles

Thermal Efficiency Analysis of Small Units of Co-generation of Heat and Power

In some areas in our country, the thermal efficiencies of small units of co-generation of heat and power are low, and the effects of saving energy are not satisfying．The paper takes a heat-supplying plant（12MW）as an example to analyze and calculate small units of co-generation of heat and power in winner and summer, and gets the thermal efficiencies and capability parameters of each part of the system.. Through the comparison of the calculation results of each month condition of whole year, the article presents the relation between the efficiency of CHP unit and the variation of thermal load, it also advances measures to improve the thermal efficiency and the styles of concentrative heating of small co-generation unit.

The Analysis of Thermal Efficiency of CCGT with Back - Pressure via the Methods of Small-Deflection

Presents the results of studying the influence of efficiency gas turbine and steam section of CCGT on the thermal efficiency of combined-cycle plant with back-pressure based on a powerful high-temperature gas turbine. To assess the impact of selected parameters was made analysis by method of small-deflection. The advantages of one-circuit combined-cycle in comparison with more complex schemes. According to the research results, have been made corresponding conclusions.

Development of a Multi-Point Injection System Operating on Superheated Alcohol Fuels and Evaluation of Toxicity of Their Combustion Products

This article is devoted to the development of a fuel injection system for internal combustion engines (ICEs or engines) with positive ignition, which operates on superheated fuels. Such systems allow engines securely starting and working on absolute (96%) alcohol, even in low temperature environments. This article describes the operation principle of a multi-point superheated fuels injection system; and the comparison analysis of thermal efficiency and heat balances of both the baseline gasoline engine and the engine with a developed superheated alcohol-based fuel injection system is provided. In experimental studies, the contents of CO, CH, and CO 2 in the combustion products of alcohols were determined. Based on the obtained results we can conclude that the application of the proposed multi-point injection system operating on superheated alcohol fuels reduces both greenhouse gas emissions and harmful substances in exhaust gas emissions.

An inverse method for flue gas shielded metal surface temperature measurement based on infrared radiation

The infrared temperature measurement technique has been applied in various fields, such as thermal efficiency analysis, environmental monitoring, industrial facility inspections, and remote temperature sensing. In the problem of infrared measurement of the metal surface temperature of superheater surfaces, the outer wall of the metal pipe is covered by radiative participating flue gas. This means that the traditional infrared measurement technique will lead to intolerable measurement errors due to the absorption and scattering of the flue gas. In this paper, an infrared measurement method for a metal surface in flue gas is investigated theoretically and experimentally. The spectral emissivity of the metal surface, and the spectral absorption and scattering coefficients of the radiative participating flue gas are retrieved simultaneously using an inverse method called quantum particle swarm optimization. Meanwhile, the detected radiation energy simulated using a forward simulation method (named the source multi-flux method) is set as the input of the retrieval. Then, the temperature of the metal surface detected by an infrared CCD camera is modified using the source multi-flux method in combination with these retrieved physical properties. Finally, an infrared measurement system for metal surface temperature is built to assess the proposed method. Experimental results show that the modified temperature is closer to the true value than that of the direct measured temperature.

Thermal Field Balance and Efficiency Analysis of Plate Type Electromagnetic Induction Heating

Thermal Field Balance and Efficiency Analysis of Plate Type Electromagnetic Induction Heating

Thermal efficiency analysis of the cascaded latent heat/cold storage with multi-stage heat engine model

The cascaded thermal storage technique has emerged as an important solution for efficient conversion and utilization of thermal energies. In this paper, an exergy optimization was performed for cascaded latent cold/heat storage using multi-stage heat engine model. The optimization solution for both heat storage and cold storage systems was obtained, which was used for guiding the selection of PCMs with two examples presented. Cascaded thermal storage with increased stage number can not only extend temperature band for multi-grade thermal energy, but also reduce the exergy of the outlet HTF. It was found that heat transfer enhancement (improving NTU) is very necessary for a cascaded thermal storage system. The COP of cold energy may be greater than 1, which is also higher than that of heat for the same temperature difference in a cascaded thermal storage system. The increased environment temperature improves the COP of the cascaded cold storage (from 0.54 to 0.68) but reduces that of the cascaded heat storage (from 0.42 to 0.366). In the practical design of the cascaded thermal storage system, the stage number should be determined by balancing economics and system complexity.

Thermal Efficiency Analysis of SkyFuel's Advanced, Large-aperture, Parabolic Trough Collector

Abstract SkyFuel has empirically established the thermal efficiency of the SkyTrough® DSP: an advanced, low-cost parabolic trough collector recently developed by SkyFuel, Inc., and funded in part by DOE grant DE-EE0003584.000. A full-scale demonstration module has been built at SkyFuel's headquarters in Colorado for the purpose of comprehensive performance and efficiency testing. This testing is complete, andincludes the analysis of the collector's optical laser intercept, heat loss of the molten salt-compatible receivers, optical efficiency while tracking the sun, operation with molten salt, and molten salt freeze recovery. Complete results are presented herein for the SkyTrough® DSP parabolic trough.

Thermodynamic analysis and optimization of the Atkinson engine by using NSGA-II

Recently, several studies have been conducted regarding the Atkinson cycle and Atkinson engine which have resulted in various thermal efficiency and output power analysis. In the present study, output power and engine thermal efficiency are maximized via employing the NSGA-II approach and thermodynamic analysis. The multi-objective evolutionary approach on the basis of the NSGA-II method is implemented throughout this work for optimizing the above-mentioned variables. To evaluate the aforementioned goal, two objective functions which comprises the power output (W) and cycle efficiency (η) have been included in the optimization process simultaneously.

Design of Air Thermal Recovery Experiment Device and Analysis of Thermal Efficiency

It was significant for energy save and environment protection that heat recovering high temperature and high humidity air directly discharged into the atmosphere. Based on high temperature and high humidity mine retention tower and return air fluid, the air heat recovery simulation experiment device was designed, and air heat recovery experiment was researched by using spray heat exchanger. Heat exchange efficiency was tested by experiment with certain water spray coefficient and different nozzle number, and experiment result that was error analysis and data correction through compared with theoretical analysis results. Result showed that the air heat recovery simulation device can recycle heat of air fluid stably, and rise temperature of spray cold water to about 15°C. The heat exchange efficiency would be 90% with certain water spray coefficient, which is basically identical with theoretical analysis. Energy saving effect of this device was remarkable with high heat exchange efficiency.

APPLICATION OF MONITORING, DIAGNOSIS, AND PROGNOSIS IN THERMAL PERFORMANCE ANALYSIS FOR NUCLEAR POWER PLANTS

As condition-based maintenance (CBM) has risen as a new trend, there has been an active movement to apply information technology for effective implementation of CBM in power plants. This motivation is widespread in operations and maintenance, including monitoring, diagnosis, prognosis, and decision-making on asset management. Thermal efficiency analysis in nuclear power plants (NPPs) is a longstanding concern being updated with new methodologies in an advanced IT environment. It is also a prominent way to differentiate competitiveness in terms of operations and maintenance costs. Although thermal performance tests implemented using industrial codes and standards can provide officially trustworthy results, they are essentially resource-consuming and maybe even a hind-sighted technique rather than a foresighted one, considering their periodicity. Therefore, if more accurate performance monitoring can be achieved using advanced data analysis techniques, we can expect more optimized operations and maintenance. This paper proposes a framework and describes associated methodologies for in-situ thermal performance analysis, which differs from conventional performance monitoring. The methodologies are effective for monitoring, diagnosis, and prognosis in pursuit of CBM. Our enabling techniques cover the intelligent removal of random and systematic errors, deviation detection between a best condition and a currently measured condition, degradation diagnosis using a structured knowledge base, and prognosis for decision-making about maintenance tasks. We also discuss how our new methods can be incorporated with existing performance tests. We provide guidance and directions for developers and end-users interested in in-situ thermal performance management, particularly in NPPs with large steam turbines.

An Application Analysis of Solution Circulation Heat Recovery System in Natural Gas Fired Boiler

In this paper, a new system which absorbs the water vapor in flue gas of natural gas fired boiler (NGFB) by desiccant solution is introduced. This system can recover the latent heat of water vapor and improve the thermal efficiency of the NGFB significantly. In the theoretical analysis, the packed tower which is the most important equipment of solution circulation heat recovery system (SCHRS) can be designed by establishing a mathematical model. Based on the recovery efficiency of water vapor by desiccant solution absorption, the thermal efficiency analysis of NGFB is discussed, which show that SCHRS has a good application prospect in NGFB waste heat recovery.

Total heat recovery of gas boiler by absorption heat pump and direct-contact heat exchanger

This paper presents a new technology which combines the absorption heat pump and the direct-contact heat exchanger. Based on the analysis of natural gas features and thermal efficiency of the gas boilers, it analyzes existing and new techniques for heat recovery, focusing upon removing heat from the flue gas to a point where it can be below the dew point as significant to realizing the total heat recovery for the gas boiler. Through field test and experimental analysis of an actual case in a district heating system operating at various system load, this paper strives to identify challenges related to high return water temperature, achieving a low-temperature cold source, and enhancing the heat transfer effect; while observing if the system performance is satisfactory, and whether the system can achieve very stable performance under different working conditions and realize the total design heat capacity improvement of 12%. Data will be examined for boiler load and its influences on the condensing rate with suggestions for further improvements.

The Impact of Primary Circuit Coolant Average Temperature on the Secondary Circuit Thermal Efficiency at Nuclear Power Station

The variations of secondary circuit parameters are limited by the parameters of primary circuit during PWR nuclear power station operation, the primary circuit average temperature should vary at the range of nuclear reactor operating safely. In the existing analysis of secondary circuit thermal efficiency at nuclear power station, the impact of primary circuit average temperature on the secondary circuit thermal efficiency is not taken into consideration. In this paper, the changes of primary circuit average temperature in actual operation are considered, the secondary circuit parameters are calculated according to the model of heat flux transfer between primary and secondary circuit, the thermal efficiency of ideal cycle is chosen as the evaluating indicator of secondary circuit thermal efficiency, the thermal efficiencies of ideal cycle in secondary circuit are calculated under the conditions of varying coolant average temperature with the method of matrix, and the calculated results are basis for the safe and economic operation of nuclear power station.

Analysis of thermal efficiency via analysis of heat flow and entropy generation during natural convection within porous trapezoidal cavities

Thermal management via distributions of heatlines and entropy generation for natural convection within trapezoidal cavities in presence of hot left wall, cold right wall and adiabatic horizontal walls has been studied in this article. Heat flow visualization has been carried out via heatline concept. Galerkin finite element method has been used to analyze streamlines, isotherms, heatlines, entropy generation due to fluid friction and heat transfer over wide range of parameters (10-5⩽Da⩽10-3,0.015⩽Pr⩽1000 at Ra=106). At low Darcy number (Da=10-5), conduction dominant heat transfer is found based on low magnitudes of streamlines and heatlines. Heatlines indicate that heat transfer occurs from hot left wall to cold right wall and thermal mixing is found inside the cavity. The thermal mixing is enhanced as Da increases from 10-5 to 10-3. The thermal gradients are high near the lower portion of left wall and near upper portion of right wall for Da⩾10-4 irrespective of φ and Pr and thus, thermal boundary layer thickness is small along those zones. The maximum entropy generation due to fluid friction (Sψ,max) occurs along the left wall for φ=30° and 90° irrespective of Pr whereas that occurs along the right wall for φ=60° at Da=10-3. The maximum entropy generation due to heat transfer (Sθ,max) occurs at the left edge of bottom wall irrespective of Pr and Da for φ=30° and 60° whereas that occurs at the left edge of bottom wall and right edge of top wall for φ=90° with Da=10-5 and 10-4. At φ=90° with Da=10-3,Sθ,max occurs along both side walls for Pr=0.015 whereas that occurs along left wall for Pr=1000. It is found that total entropy generation is high for Pr=1000 compared to that of Pr=0.015 at higher Da. It is also found that the trapezoidal cavities with φ=60° and 90° correspond to less entropy generation with significant heat transfer rates at Da=10-3 for Pr=0.015 and Pr=1000 and thus the trapezoidal cavities with φ⩾60° may be the optimal design for thermal processing of Pr=0.015 and Pr=1000 fluids.

Comparison of energy efficiency assessment methods: Case Bio-SNG process

The goal of biofuel production is to partially replace fossil fuels in energy generation and transport. For the evaluation of biofuel production processes different criteria are applied and usually they include costs, efficiency aspects and emissions. However, evaluation of the energy efficiency of biofuels production is difficult since no general standard method exists for that. This paper compares three different assessment methods of energy efficiency both qualitatively and quantitatively. The methods are: thermal efficiency, exergy analysis and primary energy analysis. The feasibility of the methods is tested on a Bio-SNG (synthetic natural gas) production process which was modelled in AspenPlus and MS Excel. The results show that the exergy analysis seems to be advantageous when it comes to detailed (sub-) process analysis whereas the primary energy analysis offers the advantage of showing how the system is influencing the global primary energy resources. The results obtained by the thermal efficiency analysis do not add any new information to the results obtained by exergy and primary energy analyses. Exergy and primary energy analyses should be the preferred means for process assessment. Especially a combination of the two methods could offer the chance to develop a more holistic energy efficiency indicator.

Effects of water-emulsified fuel on a diesel engine generator’s thermal efficiency and exhaust

Water-emulsified diesel has proven itself as a technically sufficient improvement fuel to improve diesel engine fuel combustion emissions and engine performance. However, it has seldom been used in light-duty diesel engines. Therefore, this paper focuses on an investigation into the thermal efficiency and pollution emission analysis of a light-duty diesel engine generator fueled with different water content emulsified diesel fuels (WD, including WD-0, WD-5, WD-10, and WD-15). In this study, nitric oxide, carbon monoxide, hydrocarbons, and carbon dioxide were analyzed by a vehicle emission gas analyzer, and the particle size and number concentration were measured by an electrical low-pressure impactor. In addition, engine loading and fuel consumption were also measured to calculate the thermal efficiency. Measurement results suggested that water-emulsified diesel was useful to improve the thermal efficiency and the exhaust emission of a diesel engine. Obviously, the thermal efficiency was increased about 1.2 to 19.9%. In addition, water-emulsified diesel leads to a significant reduction of nitric oxide emission (less by about 18.3 to 45.4%). However, the particle number concentration emission might be increased if the loading of the generator becomes lower than or equal to 1800 W. In addition, exhaust particle size distributions were shifted toward larger particles at high loading. The consequence of this research proposed that the water-emulsified diesel was useful to improve the engine performance and some of exhaust emissions, especially the NO emission reduction.Implications:The accumulated test results provide a good basis to resolve the corresponding pollutants emitted from a light-duty diesel engine generator. By measuring and analyzing transforms of exhaust pollutant from this engine generator, the effects of water-emulsified diesel fuel and loading on emission characteristics might be more clear. Understanding reduction of pollutant emissions during the use of water-emulsified diesel helps improve the effectiveness of the testing program. The analyzed consequences provide useful information to the government for setting policies to curb pollutant emissions from a light-duty diesel engine generator more effectively.

Real-Time Analysis of Engine Power, Thermal Efficiency, and Emission Characteristics Using Refined and Transesterified Waste Vegetable Oil

Abstract The study aims to investigate the real-time engine performance in terms of brake power, thermal efficiency and emission characteristics of a diesel engine. Waste vegetable oil samples were collected from several sources, mixed, and refined before transesterification. Test fuels include ultralow sulfur diesel and seven waste cooking oil biodiesel blends. Real-time data acquisition of engine performance was implemented using labview program while following the society of automotive engineers (SAE) power test code. Results showed that acid number was reduced by 99% after refining. NOx has reduced by 33% while thermal efficiency increased by 7.5% when using waste vegetable oil biodiesel.

Energy and Cost Saving of a Photovoltaic-Phase Change Materials (PV-PCM) System through Temperature Regulation and Performance Enhancement of Photovoltaics

The current research seeks to maintain high photovoltaic (PV) efficiency and increased operating PV life by maintaining them at a lower temperature. Solid-liquid phase change materials (PCM) are integrated into PV panels to absorb excess heat by latent heat absorption mechanism and regulate PV temperature. Electrical and thermal energy efficiency analysis of PV-PCM systems is conducted to evaluate their effectiveness in two different climates. Finally costs incurred due to inclusion of PCM into PV system and the resulting benefits are discussed in this paper. The results show that such systems are financially viable in higher temperature and higher solar radiation environment.

Analysis of optimization in an OTEC plant using organic Rankine cycle

This study quantified the effects of evaporation temperature, condensation temperature, and the inlet- and outlet-temperature differences of deep cold seawater and warm seawater on the performance of an ocean thermal energy conversion (OTEC) plant using an organic Rankine cycle (ORC), and also investigated the optimal operations required for the performance. A finite-temperature-difference heat transfer method is developed to evaluate the objective parameter, which is the ratio of net power output to the total heat transfer area of heat exchanger in the system, and R717, R600a, R245fa, R152a, and R134a were used as the working fluids. The optimal evaporation and condensation temperatures were obtained under various conditions for maximal objective parameters in an OTEC system.The results show that R717 performed optimally in objective parameter evaluation among the five working fluids, and that R600a performed better than other fluids in thermal efficiency analysis. The optimal seawater temperature differences between the inlet and outlet of the evaporator and condenser are proposed. Furthermore, the influences of inlet temperatures of warm and cold seawater in the ORC are presented for an OTEC plant. The simulation results should enable the performance of an ORC system to be compared when using various organic working fluids.

Experiment Investigation on Electrical and Thermal Performances of a Semitransparent Photovoltaic/Thermal System with Water Cooling

Different from the semitransparent building integrated photovoltaic/thermal (BIPV/T) system with air cooling, the semitransparent BIPV/T system with water cooling is rare, especially based on the silicon solar cells. In this paper, a semitransparent photovoltaic/thermal system (SPV/T) with water cooling was set up, which not only would provide the electrical power and hot water, but also could attain the natural illumination for the building. The PV efficiency, thermal efficiency, and exergy analysis were all adopted to illustrate the performance of SPV/T system. The results showed that the PV efficiency and the thermal efficiency were about 11.5% and 39.5%, respectively, on the typical sunny day. Furthermore, the PV and thermal efficiencies fit curves were made to demonstrate the SPV/T performance more comprehensively. The performance analysis indicated that the SPV/T system has a good application prospect for building.