Comparative Thermodynamic Analysis Research Articles

Comparative thermodynamic analysis of gold dissolution in four organic carboxylic acid-catalyzed thiosulfate systems using Eh–pH and species distribution diagrams

Comparative thermodynamic analysis of gold dissolution in four organic carboxylic acid-catalyzed thiosulfate systems using Eh–pH and species distribution diagrams

Parametric design optimization and thermodynamic analysis of plate fin heat exchanger for helium liquefaction system

The plate-fin heat exchanger is one of the most important components of helium liquefaction system as it recovers cold energy from helium gas in the cold box. Because of larger heat transfer surface area and compact geometrical configuration, plate-fin heat exchangers are widely used. The design of heat exchanger using helium as a cryogenic fluid needs high thermodynamic performance with minimum pressure drop which particularly requires the optimization of dimensional array and its geometrical configurations. In this regard, a parametric investigation was performed to compute the effective geometrical parameters and its effect on thermodynamic (effectiveness and log-mean temperature difference) performance has been discussed in detail. The present study aims to design optimization and thermodynamic performance evaluation of plate-fin type heat exchangers used in helium liquefaction systems. The developed helium liquefaction model has been simulated for the most critical liquefier with and without liquid nitrogen precooling, mixed mode, and refrigeration mode. Each component of the liquefaction model has been technically and thermodynamically analyzed and, in particular, four plate-fin heat exchangers have been considered and designed accurately using Aspen EDR®. Initially, the sensitivity analysis was carried out to characterize the most significant geometrical parameters (fin thickness, height, number and arrangement of layers, frequency, and fin type) and their effect on thermodynamic performance and pressure drop. After that, the artificial intelligence model was used to determine the optimal range of such geometrical variables in which the heat exchanger has maximum effectiveness and log mean temperature difference. Finally, the operating conditions obtained from cycle modeling and optimized geometrical datasets have been applied in commercial simulation software Aspen EDR® for plate-fin heat exchangers design. Finally, a comparative thermodynamic analysis has been carried out to determine the performance of all the designed heat exchangers operating at four different modes (boundary conditions).

Heat Utilization in Boiler Plants by Using Liquid-Vapor Jet Apparatus

The article solves the problem of heat utilization from combustion products in boiler plants. The proposed solution involves extracting heat to preheat the network water for the heating system and implementing additional heat utilization using a liquid-vapor jet apparatus. This will allow for additional working steam generation in the main steam generator and the unit based on the liquid-vapor jet apparatus. The article provides schemes and descriptions of traditional and proposed plants, indicating their design differences from the basic scheme. Comparative thermodynamic analysis of the proposed installation for additional recuperative heat utilization and the basic scheme is carried out, in which heat utilization occurs due to the extraction of heat from combustion products to preheat the network water of the heating system. As a result, the main thermodynamic parameters of the cycles of basic and proposed schemes are obtained, and the values of the capacities on the apparatuses included in these installations are determined. The energetic potential obtained from additional heat utilization is 8 %, which can be used for electricity generation. Exergy analysis assesses the efficiency of additional heat utilization in boiler plants using units based on liquid-vapor jet apparatus. As a result of the exergy analysis, the value of the exergetic efficiency of the scheme with additional heat utilization was obtained, which is 1.47 times higher than that of the basic scheme. A thermoeconomic analysis was performed to determine the cost values. Implementing the new scheme enables reducing the specific cost of the heating unit by 48 % and increasing the amount of steam generated in the installation by an additional 18 %.

Comprehensive Thermodynamic Performance Evaluation of Various Gas Liquefaction Cycles for Cryogenic Energy Storage

This paper conducts comparative thermodynamic analysis and performance evaluations of various gas liquefaction configurations. The four most common liquefaction systems (Linde–Hampson, Kapitza, Heylandt, and Claude) were considered. The isothermal and multi-stage isentropic compression processes were evaluated and compared as actual compression processes. Thermodynamic evaluation is based on the energy required to compress a unit mass of gas, the liquefied air mass flow rate, and the exergetic efficiency. The modeling results show that three-stage compression cycles retain lower energy requirements. Increasing the compression stage from one to two for all the processes decreases the energy requirement by 34 to 38%. Changing the compression stage number from two to three reduces the energy requirement by 13%. The compression pressure and expander flow rate ratio significantly affect the liquefied air mass flow rate. Hence, a parametric analysis was conducted to obtain the best operating conditions for each considered cycle. Depending on the compression pressure, the optimum expander flow rate values of the Claude, Kapitza, and Heylandt cycles change from 0.65 to 0.5, 0.65 to 0.55, and 0.35 to 0.30, respectively. For the optimum cases, the Claude, Kapitza, and Heylandt cycles result in liquid yields that are about 2.5, 2.2, and 1.6 times higher than that of the Linde–Hampson cycle. The Claude cycle is the best operating cycle for all the considered performance metrics. Moreover, the performances of the Linde–Hampson and Claude cycles are investigated for various gases. Under the same operating conditions, the results show that better performance parameters are obtained with the gases that have relatively high normal boiling temperatures.

Comparative thermodynamic and economic analysis of a conventional gas-steam power plant with a modified gas-steam power plant

This paper presents a thermodynamic and economic comparative analysis of a conventional gas-steam power plant with a modified gas-steam power plant. The modification involves replacing the gas turbine present in the conventional power plant with a High Temperature Gas-cooled Reactor (HTGR) and a turboexpander. In the Joule cycle modified power plant, the circulating medium is helium, while in the conventional power plant it is the exhaust gas produced from the combustion of natural gas. The results obtained show that the innovative dual-circuit gas-steam power plant with a high-temperature HTGR nuclear reactor and TE turboexpander has significantly higher economic efficiency than a conventional gas-steam power plant. This is despite the fact that the unit capital expenditures for a power plant with HTGR and TE are many times higher (about 8 times) compared to those for a conventional gas-steam power plant. Increasing the temperature T3 of the outlet helium from the TE above the value of T3opt= 709.1K with temperature T2 = 1300 K, is possible by reducing the compression ratio p1/p0. This will result in a significant increase in the energy efficiency of the gas-steam power plant ηG-S and of its output NG-S=NTE+NST. Increasing the temperature T3 is advantageous also for economic reasons.

Comparative Thermodynamic and Structural Analysis of Polyfluorinated Dodecylphosphonic Acid Adsorption to Distilled and River Water Interfaces.

As concerns rise about the health risks posed by per- and polyfluoroalkyl substances (PFAS) in the environment, there is a need to understand how these pollutants accumulate at environmental interfaces. Untangling the details of molecular adsorption, particularly when there are potential interactions with other molecules in environmental systems, can obscure the ability to focus on a particular contaminant with molecular specificity. Often adsorption studies of environmental interfaces require a reductionist approach, where laboratory experiments may not be fully tractable to environmental systems. In this work, we study polyfluorinated dodecylphosphonic acid (F21-DDPA) at the aqueous surfaces of distilled water (the most reduced "environmental" surface) and river water to explore the use of vibrational sum-frequency (VSF) spectroscopy as an experimental probe of fluorinated contaminants at natural environmental surfaces. We demonstrate how VSF spectroscopy offers advantages over nonspecific surface tension measurements when measuring PFAS adsorption isotherms at river water surfaces. VSF spectra of the C-F stretching region selectively probe the presence of F21-DDPA and can be used to extract meaningful structural insights and calculate surface concentrations, even at the complex river water surface. This study highlights the potential for VSF spectroscopy to be developed as a probe of fluorinated contaminants at natural environmental interfaces.

Thermodynamic modelling of integrated carbon capture and utilisation process with CaO-based sorbents in a fixed-bed reactor

The global emission of CO2 through fossil fuel combustion is still increasing, which is a major challenge for the international community. An integrated carbon capture and utilisation (ICCU) process with a CaO-based sorbent is a promising alternative to effectively reduce emissions. In this work, a comparative thermodynamic analysis of two CaO-based sorbents (commercial and sol-gel CaO) was performed for one cycle of ICCU. In addition, the influence of temperature was investigated from 600 to 750 °C in terms of the degree of CO2 conversion. Thermodynamic calculations were based on the actual gas composition and developed model, where heat consumption and entropy generation were calculated. The results indicate that the degree of CO2 conversion decreased from 84.6 to 41.2% and from 84.1 to 62.4% for the sol-gel and commercial material, respectively, as the temperatures increased. Furthermore, the total heat consumption during one cycle decreased with higher temperatures. The total amount of consumed heat decreased from 19.1 to 5.9 kJ/g and from 24.7 to 5.4 kJ/g for sol-gel and commercial CaO, respectively. Although commercial CaO always requires more heat during one cycle. Moreover, for both materials, the lowest generation of entropy was calculated at 650 °C with values of 9.5 and 10.1 J/g·K for the sol-gel and the commercial CaO, respectively. At all temperatures, the commercial CaO generated a greater entropy.

Comparative thermodynamic analysis of China Spallation Neutron Source second phase (CSNSII) SRF system cooling Scheme

The China Spallation Neutron Source second phase (CSNS-II) accelerator upgrades consist of three major components: linac energy upgrade from 80 MeV to 300 MeV, injection system upgrade, and new magnetic alloy dual harmonic cavities. There are ten double spoke cavities cryomodules and eight elliptical cavities cryomodules in total. A comparative thermodynamic analysis of the superconducting radio frequency (SRF) systems can be of great importance to select a reliable, cost-effective and easy-maintenance cooling schemes. This is particularly critical for SRF systems that require long-term operation. A comparative thermodynamic analysis of both types of cooling schemes for SRF systems, referred to as Scheme 1 (a cryogenic distribution system with distributed heat exchangers) and Scheme 2 (a cryogenic distribution system with central heat exchangers), was presented in this paperThe length and size of process transfer lines, as well as the heat loads subjected to their components, of cryogenic distribution systems were introduced. In addition, the unsteady state cooldown process for the CSNS-II SRF cryomodules was investigated. The analysis results that included temperature and pressure profiles along the linac distance, as well as distributions of JT expansion effectiveness, mass flow rate, and cryomodule exegetic efficiency. Furthermore, the exergy analysis and refrigeration power are investigated using a neural network optimized by a novel sparrow search algorithm genetic algorithm (SSA-GA). Results show that, Scheme 1 is more advantageous than Scheme 2 because it can save maintenance time. From 300 K to 4.5 K, the total cooldown time of SRF cryomodules is approximately 28 h. The maximum ΔP is around 1.1 bara, which can be considered in the acceptable range. The prediction of ηex is stable at the 7th epoch after being optimized by SSA-GA, and the MSE is 1 × 10-5. And the error between the predicted and true values of the BP neural network after SSA optimization is very small (less than 0.1%), approaching zero, indicating that the BP optimized by SSA achieves good prediction. This paper's work can serve as a solid foundation for the construction and operation of the CSNS-II.

A comparative thermodynamic and thermoeconomic analysis between two ecological regimes for the Novikov energy converter

In the context of finite-time thermodynamics, a comparative thermodynamic analysis between the ecological regime and the ecological efficient power regime, recently introduced, is done. The study examines the Novikov energy converter model with a linear heat transfer law when performing under these regimes. To make the proper comparison, through the so-called compromise functions, a modification to the ecological efficient power energetic function is proposed. It is found that the thermal efficiencies are very similar to the appropriate ones of the modified ecological function. However, notable differences are obtained for the optimal efficiencies from a thermoeconomic optimization analysis.

ADVANTAGES AND ECONOMICS OF HEAT PUMP BASED AIR HANDLING UNITS FOR VENTILATION AND AIR CONDITIONING IN COMMERCIAL AND INDUSTRIAL SECTORS

The current article contains a comparative thermodynamic analysis of the two most popular solutions for general ventilation and air conditioning: supply-exhaust units based on built-in circuits of heat pumps or external compressor-condenser units as the main energy sources. The theoretical analysis was carried out under the same constant conditions in the cold mode of operation in the warm season, when it is necessary to cool the supply air. As a result of the research, graphs of the dependences of the parameters of the two systems (temperature and air humidity at the nodal points of the systems, energy efficiency of HP or CCU and schemes as a whole) were constructed on the parameters of the outside air and the needs for ventilation and air conditioning inside the premises according to the project conditions. The purpose of this article is to theoretically investigate which of the schemes has a higher efficiency under the given conditions. The researched theoretical models of the two systems can be used to assess the feasibility of one or another scheme depending on the project, as well as during the design of the AHU. Using this analysis, it is possible to accurately and effectively select such real plant components as heat exchangers, compressors, heat exchangers, etc. for the production of supply and exhaust units.

Comparative thermodynamic and techno-economic analysis of various medical waste-to-hydrogen/methanol pathways based on plasma gasification

Three novel medical waste-to-hydrogen/methanol pathways based on plasma gasification using Aspen Plus have been proposed: The first pathway is used to convert medical waste into hydrogen; the second pathway is applied to convert medical waste into methanol; the third pathway is used to convert medical waste into hydrogen & methanol. In this study, thermodynamic and techno-economic analyses were conducted to evaluate and compare the performance of three pathways. Furthermore, three schemes are assessed by comparative economic sensitivity concerning the chemical product price, electricity price, capital expenditure, and discount rate. The thermodynamic results show that process efficiency and process exergy efficiency of the third pathway can achieve 72.16 % and 66.88 %, which is higher than the first pathway (69.45 % and 65.65 %) and the second pathway (54.08 % and 50.93 %). The techno-economic results indicate that the first pathway has a shorter dynamic payback period of 3.83 years and a relatively higher net present value of 13,783.57 k$ than the second pathway (7.42 years and 5,700.32 k$) and the third pathway (5.27 years and 10,780.00 k$). This work provides novel methods and guidance for efficient and economical harmless treatment and resource utilization of medical waste.

Comparative thermodynamic analysis of an improved ORC process with integrated injection of process fluid

In contrast to water-steam Rankine cycles, the ORC process uses organic working fluids. For working fluids of the dry class, a recuperator heat exchanger is frequently installed to increase the cycle efficiency. This paper analyses an improved ORC process with these features: A liquid working fluid stream is injected into the vapour flow between the high-pressure and the medium-pressure stage of the turbine. Furthermore, the recuperator is replaced by a spray condenser. The main objective is to increase efficiency with moderate changes in the process layout. A thermodynamic comparison of the improved process with a state-of-the-art ORC process is carried out by simulations and optimisations. A significant efficiency gain for the improved ORC process is obtained by a combination of the aforementioned features, mainly because of an increase of the mass flow in the economiser of the vapour generator (better heat utilization) and a corresponding mass flow in the medium stage of the turbine (additional power production). As a use case, waste heat utilization from a clinker cooler at a temperature level of 275 °C was simulated. The improved process would lead to a significant increase in the overall net efficiency by up to 14%, compared to a state-of-the-art ORC process.

Low-grade heat utilization in the methanol-fired gas turbines through a thermochemical fuel transformation

Methanol can be considered as an alternative fuel for different engines. This paper investigates the low-grade heat utilization in methanol-fired gas turbines. Two cases were analyzed: the first is low-grade heat utilization for steam generation, and the second is for methanol decomposition before its combustion. The concept of low-grade heat utilization via methanol decomposition is developed and described in details. The comparative thermodynamic analysis was performed via Aspen HYSYS under the wide ranges of the operational parameters: gas turbine inlet temperature of 800–1000 °C, compression/expansion ratio of 9–15. The temperature potential of low-grade heat was set from 200 to 400 °C. It was established that low-grade heat utilization via methanol decomposition is more efficient (up to 5%) in comparison to low-grade heat utilization via steam generation. Methanol decomposition before its combustion leads to an increase in the power output in the gas turbine. Simulation tests of various temperatures potential of low-grade heat showed that it does not play a significant role in the efficiency of utilization. However, it was determined that maximal methanol decomposition is observed at a temperature above 300 °C. The Sankey diagrams for the energy flows are depicted and analyzed. The future perspectives of the use of the low-grade heat utilization concept via fuel decomposition were described for carbon-free fuel–ammonia. • Low-grade heat utilization via methanol decomposition concept. • Chemical energy of methanol is converted into heat in two stages. • Efficiency of low-grade heat conversion to electricity is up to 36% • Heat utilization via methanol decomposition is up to 5% more efficiently than traditional ways. • Methanol decomposition before combustion is “chemical exergy pump”.

Comparative experimental evaluation and thermodynamic analysis of the possibility of using degraded C15-C50 crankcase oil waste as thermal storage materials in solar drying systems

The study presents a comparative thermodynamic analysis of degraded C15-C50 grade crankcase oil (DCO) and paraffin thermal storage (PTS) as heat storage materials in solar drying. The goal is to convert DCO from waste to a useful product in solar drying. The assessment was based on drying efficiency, energy and exergy analysis, sustainability assessment and CO2 mitigation of each solar dryer. The difference in drying efficiency between the dryer with DCO and that with PTS is less than 1.5 % while the difference between the specific energy consumption is less than 9 %. In contrast, the difference between the dryer with DCO and that without thermal storage is 24.2 %. The mean exergy efficiency ranged between 41.6 and 49.9 %. The values of the waste exergy ratio (WER), sustainability index (SI) and improvement potential (IP) for the three dryers ranged from 0.00 ≤ WER ≤ 1.00, 0.00 ≤ SI ≤ 34.56, 0.00 ≤ IP ≤ 2.68 kW. Using these dryers instead of diesel, grid-based electricity or coal-powered dryer will limit a maximum of 5,792,826 tons of CO2 from the atmosphere.

Comparative Thermodynamic Analysis of the Performance of an Organic Rankine Cycle Using Different Working Fluids

Today, the study of thermal systems that take advantage of residual thermal sources in the power generation sector is of great importance to mitigate environmental impact and promote sustainable alternatives in this sector. Among these alternatives, the organic Rankine cycle (ORC) is of great relevance since it allows taking advantage of residual energy sources at low temperatures. This work presents a methodology to evaluate the feasibility of using a refrigerant as a working fluid in an organic Rankine cycle based on an exergetic viability index. As a case study, R134a, R600a, R245fa, and R123 refrigerants were considered. A residual thermal source was used that came from the Hybrid Cycle Plant of the Valley of Mexico. Thermodynamic analysis was performed to determine generated power, thermal efficiency, refrigerant mass flow, pinch point temperature difference, specific steam consumption, unused thermal exergy flow, exergy efficiency, and total heat transfer requirement. The weighted average of the differences between these indicators, the global warming index, and the ozone depletion potential relative to the most favorable indicator corresponded to the definition of the exergetic viability index of the refrigerant. The results indicate that the ORC operating at condensing temperatures of 25, 35, and 45 °C with R245fa shows the highest rate of exergetic viability despite not generating the greatest amount of power and being one of the refrigerants with the highest total heat transfer requirement. Finally, at condensing temperatures above 45 °C, it is observed that R600a is exergetically the most viable refrigerant used in the ORC.

CH4 valorisation reactions: A comparative thermodynamic analysis and their limitations

In this study, we report on a first comparative thermodynamic analysis of various CH4 valorisation processes, taking into account the formation of byproducts through a network of side reactions. The analysis is carried out to assess the influence of a wide range of reaction parameters on the performance of each valorisation process in terms of CH4 conversion and desired selectivity metrics. The Gibbs free energy minimization method is used for the equilibrium study of nine CH4 conversion processes, including ten side reactions. The ΔG calculations revealed that the oxidative coupling of methane (OCM) and the methane dehydro-aromatization (MDA) reactions are thermodynamically the most and least feasible reactions, respectively. At P = 1 bar and T = 700 °C, the highest and lowest CH4 conversions were obtained by the dry reforming of methane (DRM) (90%) and oxidative dimerization (18%), respectively. The DRM and steam reforming of methane (SRM) were highly sensitive to changes in operation parameters, while the partial oxidation of methane (POM) and OCM were the least affected. The increasing addition of water in reforming reactions reduced the coke formation to zero at temperatures above 675 °C. From the comparison of the thermodynamic results with the documented experimental data, the carbon deposition was found to decrease both the selectivity and stability of catalysts. Investigations into the thermodynamic and kinetic limitations together with the catalyst design will help in the development of a commercial CH4 valorisation process.

Thermodynamic Analysis of a Semi-Closed Oxy-fuel Combustion Combined Cycle

Semi-closed oxy-fuel combustion combined cycle (SCOC-CC) is a strong concept of carbon capture and storage (CCS) in gas-fired power plants. This technology is similar to a conventional combined cycle, however oxygen instead of air is used in fuel combustion. In the oxy-fuel combined cycle, the gas turbine flue gases consist mainly of CO2 and H2O. One of the problems to implement this technology is the necessity of an air separation unit (ASU) to separate the oxygen from the air, which increases the energy consumption of the power plant. Thus, a comparative thermodynamic analysis was performed between a conventional combined cycle (base case) and an oxy-fuel combined cycle. The objective is to identify each technology's pros and cons, the influence of oxygen purity in the oxy-fuel combine cycle, and the main irreversibilities of each case. The SCOC-CC optimal operating point (maximum energy efficiency) was found utilizing particle swarm optimization (PSO), which lead to the optimal ASU oxygen purity of 95.99%. It was noticed that the oxy-fuel combined cycle first law efficiency is 6.9% lower than the base case, and the second law efficiency is 6.5% lower. Despite the efficiency loss the SCOC-CC is more environmentally friendly than the conventional combined cycle since it can theoretically capture all CO2 produced in the combustion chamber.

A Comparative Thermodynamic and Thermoeconomic Analysis between Two Ecological Regimes for the Novikov Energy Converter

A Comparative Thermodynamic and Thermoeconomic Analysis between Two Ecological Regimes for the Novikov Energy Converter

Comparative thermodynamic analysis of LNG, LPG, methanol, ethanol, biodiesel and hydrogen as alternative fuels in HCCI engines

Aiming to mitigate the problem of harmful emissions arising from the use of conventional fossil fuels, the performances of alternative fuels, namely LNG, LPG, biodiesel, ethanol, methanol, and hydrogen in an HCCI engine have been analyzed. Thus, a thermodynamic model that considers the gas composition of combustion products and the specific heat temperature dependency of the working fluid has been developed. It allows examining the influence of key engine parameters such as the compressor pressure ratio, ambient temperature, equivalence ratio, engine speed, and the compressor isentropic efficiency on the performance of the HCCI engine. The reliability of the model has been successfully verified against various theoretical and experimental data from the literature. Results showed that LNG performs the best in terms of brake efficiency, exergy efficiency, and placed second in terms of brake specific fuel consumption. With the exception of the latter, although it is associated with a higher energy value, hydrogen produces lower performance compared to the other fuels assessed. For all fuels, the largest exergy destruction rates occur in the HCCI engine. It ranges between 78.4 and 87.8 % of the total exergy destruction rate according to the fuel used. The order of exergy destruction rates within the other components differs from one fuel to the other.

A novel solar assisted multigeneration system devoid of external utilities for drought adaptation considering water-exergy nexus analysis

• A sustainable solar multigeneration system was proposed to adapt to climate change. • Comparative thermodynamic, cost, risk, and environmental analysis were conducted. • The system offers 13 times less water withdrawal than conventional power plants. • Exergetic efficiency of the eco-friendly system can reach up to 74.37% • The novel system manages to generate products at a cost rate of 0.017 $.MWh −1. Conventional steam-driven multigeneration systems contribute to environmental damage by losing significant freshwater and emitting greenhouse gases. Here, a novel solar-powered steam jet ejector-based multigeneration system independent of external cold utilities is proposed for climate change adaptation. A Rankine cycle, an organic Rankine cycle, and a reverse osmosis desalination unit are fully integrated for clean power, cooling, and freshwater production employing. The thermo-mathematical model was evaluated considering thermodynamic efficiencies, annual costs, exergorisk, and global warming potential in a stand-alone and comparative framework. The water utilization of the hot utility was compared with two traditional fossil fuels by conducting a water-exergy nexus analysis. The analytical results showed that most of the total exergy destruction (73%) occurred in the solar collectors. The proposed system had 0.0171 $.MWh −1 cost of energy and an exergy efficiency of 57.29 % by employing R11. Compared to a natural gas-fired utility, the proposed solar-powered system reduced freshwater withdrawal, and consumption by 16 and 13 times, respectively. The system could achieve the exergetic efficiency of 74.37 % with the cost of energy of 0.013 $.MW −1 in a parametric model. Finally, R365mfc emerged as the optimal fluid for the proposed system by satisfying all performance criteria.