Gas Heat Research Articles

An open-source software framework for the integrated simulation of structures in fire

The traditional methods to understand the development of elevated temperature in a structure, and also the associated structural response, are not representative of realistic fire scenarios. To provide a more accurate and realistic reflection of the fire development, the current paper develops a generic middleware which interfaces between the computational fluid dynamics (CFD) software Fire Dynamics Simulator (FDS) and the finite element (FE) analysis software OpenSees. This framework enables a fully integrated simulation of a realistic fire scenario including the heat transfer through the structure and the resulting thermo-mechanical response. The proposed framework is open-source and freely available and therefore can be used and further developed by researchers and practicing engineers and customised to their requirements. This paper shows validation against two sets of experimental results and one real fire incident. A number of different types of thermal boundary conditions such as gas temperatures and heat fluxes, are obtained from the CFD analysis and are then used in the subsequent heat transfer and thermo-mechanical analysis. The primary advantage of this computational tool is that it provides consultants and designers with the means to undertake large-scale projects requiring performance-based fire engineering solutions.

Thermal modelling and analysis of a novel solar integrated waste-to-energy plant for sustainable society

Waste-to-energy incineration is an effective and sustainable solution to reduce produced waste and simultaneously generates electricity utilizing thermal energy. The waste-to-electrical efficiency of conventional incineration plants is limited to 20–25% due to the higher amount of moisture content in the feedstock and flue gas heat losses. In addition, tubes of the incineration boiler are subjected to corrosion problems at elevated temperatures. In the present research, a parabolic trough solar-integrated municipal solid waste power plant is proposed and thermodynamically evaluated for different useful outputs. The solar energy is harvested through parabolic trough collectors to reheat the working fluid of the incineration plant to increase the steam temperature before it is fed to the low-pressure turbine. Meanwhile, a single-effect absorption chiller is integrated to utilize the thermal energy of the trough collectors for cooling purposes. In addition, the thermal energy of flue gas is used to power an organic Rankine cycle that further drives a proton exchange membrane and reverse osmosis desalination unit for hydrogen and freshwater production, respectively. In this way, the steam temperature for reheating the low-pressure turbine is increased to further improve the performance of the proposed solar-integrated waste-to-energy plant without causing any corrosion problems to the incineration boiler. The integrated facility is thermodynamically analyzed based on a 560-tons/day incineration plant using the engineering equation solver (EES) software. The results indicate that the overall energy and exergy efficiencies of the proposed plant are 32.51% and 23.7%, respectively, while the coefficient of performance of the absorption chiller is 0.849. Moreover, it is concluded that the produced desalinated water and hydrogen rates are 23.96 kg/s and 0.000857 kg/s, respectively.

A reaction mechanism for oxygen plasmas

Abstract This work presents a reaction mechanism for oxygen plasmas, i.e. a set of reactions and corresponding rate coefficients that are validated against benchmark experiments. The kinetic scheme is validated in a DC glow discharge for gas pressures of 0.2–10 Torr and currents of 10–40 mA, using the 0D LisbOn KInetics simulation tool and available experimental data. The comparison comprises not only the densities of the main species in the discharge— O 2 ( X 3 Δ g − ) , O 2 ( a 1 Δ g ) , O 2 ( b 1 Σ g + ) and O ( 3 P ) —but also the self-consistent calculation of the reduced electric field and the gas temperature. The main processes involved in the creation and destruction of these species are identified. Moreover, the results show that the oxygen atoms play a dominant role in gas heating, via recombination at the wall and quenching of O 2 ( X 3 Σ g − , v ) vibrations and O 2 electronically-excited states. It is argued that the development and validation of kinetic schemes for plasma chemistry should adopt a paradigm based on the comparison against standard validation tests, as it is done in electron swarm validation of cross sections.

Energy management and reducing the environmental impacts of industrial flare gases using a new trigeneration energy system

Recovering the heat of flare gases through energy systems exploits a waste source of energy and contributes to the industrial development of societies. Reducing environmental pollution and energy management of flare gases are considered among the main necessities of industrial complexes, especially refineries. One of the methods to reuse these gases is to employ them in downstream energy systems to produce useful products. A novel trigeneration energy system is presented for power, heating, and freshwater production by recovering the waste heat of industrial flare gases. The system is scrutinized from thermodynamic and thermoeconomic criteria. Furthermore, a multi-objective optimization of the set-up is performed. Optimization results show an acceptable increase in energy and exergy efficiencies while a decrease in the unit cost of product is obtained.

Thermodynamic and economic analysis of a multi-energy complementary distributed CCHP system coupled with solar thermochemistry and active energy storage regulation process

The combination of distributed energy systems (DES) and solar energy is considered a vital measure to save the usage of fossil energy. A new distributed combined cooling, heating and power (CCHP) system integrated with solar thermochemistry (STC) and energy storage (ES) units is proposed. The methane steam reforming (MSR) reaction is driven by solar energy to produce hydrogen-rich syngas, which is fed with high-efficiency solid oxide fuel cell (SOFC) – micro gas turbine (MGT) to produce electricity. The residual heat of the flue gas drives a double effect lithium bromide unit for cooling and a heat exchanger for heating, while a parabolic trough collector (PTC) is used to supplement cooling and heating supply. Under different weather conditions and user load demands, simulation analysis of the matching between system outputs and user loads is conducted, and the thermodynamic and economic performance are analyzed. The results show that through active energy storage regulation, the new system outputs can meet the hourly user loads with a matching degree of 1. The total exergy efficiencies of the system on typical summer, transition and winter days are 69.93%, 62.03%, and 52.28%, respectively, and the specific CO2 emission rates are 152.57 g/kWh, 191.75 g/kWh, and 234.16 g/kWh, respectively, indicating that the system has higher exergy efficiency and is more environmentally friendly under strong solar radiation. Economic analysis indicates that the capital investment cost is 779.34 k$, and the revenue begins in the 9-th year.

Potential of applying the thermochemical recuperation in combined cooling, heating and power generation: Off-design operation performance

Combined cooling, heating and power system (CCHP) as a typical distributed energy utilization technology, is usually installed close to the end-user to satisfy the diverse energy demands, which also has multiple advantages of energy-efficient and environment-friendly. While the simultaneously changing user energy loads brings about a huge challenge for the system energy conversion and regulation process, and then significantly affects the system operation flexibility. Therefore, the new method of thermochemical recuperation (TCR) is employed to enhance the system dynamic energy utilization performances, and also efficiently converts the high-temperature exhaust gas heat into hydrogen-enrich syngas for further application. In this work, by considering the practical system operation, the off-design TCR operation adjustment capacity for the system diverse energy outputs is important, which is extensively investigated. Based on the developed mathematic model, different-size (small, middle and large) gas turbine scenarios are considered, the results indicate that the TCR process effectively optimize the system energy conversion process, and the corresponding power efficiencies are improved by 10.53%–13.87%, 8.56%–14.46% and 14.23%–14.42%, respectively. In addition, with the merits of adaptively coordinating the multi-energy production, the off-design energy outputs boundary of the CCHP system can be extended and then readily match the fluctuant user loads. Specifically, as for the small scale GT-based system application in a hotel building case, the system annual recuperated fuel ratio reaches to 0.54 with the annual coordinated recuperation operation time ratio of 0.70, and then the system operation flexibility is thus enhanced with the annual fuel saving ratio of 6.03%, which also contributes to the CO2 emission reduction. With the favorable potential to optimize the CCHP system operation regulation, the thermochemical recuperation technology provides a feasible pathway to enhance the distributed energy system application feasibility.

Techno-economic analysis of auto-thermal gasification of municipal solid waste with ash direct melting for hydrogen production

Hydrogen is regarded as a promising secondary energy source to tackle the pollutions and carbon emission caused by the usage of fossil fuels. Municipal solid waste (MSW) generated in our daily lives as a potential renewable energy resource can be used for hydrogen production via gasification process. Yet the techno-economic feasibility of the waste-to-H2 process has not been well evaluated. This study proposes a H2 production route from MSW via an auto-thermal steam gasification combined with ash direct melting process. The technical and economic performances of the system are evaluated by process simulation using Aspen Plus. Part of the generated syngas is extracted for combustion with oxygen to provide heat for gasification and achieving ash melting. A net H2 yield of 0.075 kg/kg-MSW was obtained at the gasification temperature of 900 °C and steam/MSW ratio of 0.9. The levelized cost of hydrogen (LCOH) is 18.53 CNY (Chinese Yuan)/kg. Under this condition the energy and exergy efficiency are 47.37% and 40.18%, respectively. Three additional cases were also studied to investigate the effects of external energy supply, ash melting process, and gasification agent on the thermodynamic and economic performances. Using biochar as external supply energy will lead to a higher H2 yield (0.112 kg/kg-MSW), but also a higher LCOH due mainly to the additional biochar cost and CO2 capture cost. If without the ash melting process, the energy efficiency can be improved, yet the generated ash may need further treatment which would otherwise cause environmental pollution. Considering the technical, economical, and environmental perspectives, the gasification and direct melting process as a harmless and resourceful method presents a promising potential for waste-to-H2 conversion.

Using an artificial neural network model for natural gas heat combustion forecasting

Using an artificial neural network model for natural gas heat combustion forecasting

Proposing and thermo-economic optimization of an annular-thermoelectric gas heat recovery unit with a novel hybrid fin-pin vane and porous insert

Heat recovery from the cylindrical surface of the exhaust gas pipes is one of the promising applications of annular thermometric generators (ATEG). A pipe-shape based heat exchanger can be attached to the inner surface of the annular-thermoelectric generator to recover the hot exhaust gas in the form of electricity generation. In this paper, a novel grid annular fin-based heat exchanger with porous inserts is proposed which can boost the output power of the ATEG up to 1.45 and 2.12 times compared to the conventional common pipe-based heat exchangers. A comprehensive parametric analysis is carried out to investigate the impact of various geometric and operational parameters such as porous insert height, porous insert angle, porous inserts length, Re number, number of thermocouples, and so on thermal, exergetic, and economic factors. An optimized value of height, length, and angle of the porous insert can maximize the output power of the proposed system. Economic analysis is also provided to identify the corresponding costs of the grid annular fin-based heat exchanger with porous inserts for the heat recovery aim.

A comparative evaluation of co-gasification of blends of low grade and washed coals with high-rank coal in a fixed bed reactor

ABSTRACT Coal is the most valuable gasification resource due to its abundance and low cost for commercial applications. But utilization of low-rank Indian coals for gasification is challenging due to difficulty in washing. For utilizing low-grade high ash raw coal, blending is one of the effective methods to control the gasification performances. So, the present study explores the gasification of such a low-rank raw coal blend and compares the results with washed coal blend. The blending effects on raw gas yield (kg/kg of coal) and heating value (Kcal/Nm3) were investigated for coal blends-WH (washed coal with high-rank coal) and RH (raw coal with high-rank coal). In WH, raw gas yield is 1.210 to 1.225 (kg/kg of coal), whereas, in RH is 1.189 to 1.213 (kg/kg of coal), though the fixed carbon content of WH (40.75–41.74%) is lower than RH (44.73–45.25%). In washed coal, raw gas yield is minimum (0.75 kg/kg of coal). The heating value is lower in WH (2730–2871 Kcal/Nm3) than in RH (2884–2978 Kcal/Nm3). Statistical correlation is developed between gaseous components of raw gas and heating value; H2/CO ratio is the most significant parameter. RH gasification is economically viable than WH.

Methods to reduce heat losses when transporting gas through long branch pipelines

The article considers options to reduce heat losses accompanying the process of pipeline transportation of natural gas through long branch pipelines. Computational modeling of the gas cooling process in an extended off-take gas pipeline connecting the main gas pipeline and the gas distribution station has been performed. It is shown that when the length of the gas branch pipeline is long, especially in conditions of reduced flow, the gas temperature at the inlet of the gas distribution station will correspond to the ground temperature. We have developed and substantiated options to reduce the intensity of gas cooling in the off-take gas pipeline, involving an increase in its depth, the use of thermal insulation coatings, as well as the regulation of pressure at the inlet using special technical means. The calculation justification of the technical solution, which involves regulating the pressure at the inlet to the gas pipeline outlet, is performed. The results can be used by gas transportation companies. The implementation of the developed solutions to reduce heat losses will reduce the consumption of energy used for gas heating at gas distribution stations and reduce emissions of combustion products.

Techno-economic assessment of a synthetic methane production process by hydrogenation of carbon dioxide from direct air capture

Direct air capture (DAC) is widely investigated to capture carbon dioxide (CO2) emissions from decentralised sources. As an alternative to geological storage, CO2 from DAC can be reacted with hydrogen (H2) from water electrolysis driven by renewable energy to produce synthetic methane (CH4), increasing the penetration of renewable energies and leading to a circular carbon economy. This study presents a techno-economic assessment of an integrated system for DAC based on calcium looping and subsequent methanation of CO2. Photovoltaics (PV) is considered as renewable energy source. For the DAC plant, heat exchangers represent the most expensive component, followed by blowers/compressors, reactors and gas heaters. The levelized cost of CO2 removal for DAC ranges within 693–1587 € tCO2−1 according to the parameters considered. For a methanation plant built in Abu Dhabi (United Arab Emirates), the electrolyzer represents the most expensive component, followed by PV field, H2 storage tank, and reactors. Altogether, the levelized cost of methane (LCOM) ranges within 4.9–8.2 € kgCH4−1 for integration with the DAC plant investigated. It reduces to 3.1–3.9 € kgCH4−1 for integration with point source carbon capture. A comparison between Abu Dhabi and Benevento (Italy) reveals that cities with an uneven distribution of solar energy throughout the year may require a large investment cost for the H2 storage tank, that makes the LCOM increase. In conclusion, LCOM values provided in this study exceeds the current price of methane, suggesting that further improvements or economic incentives are required to increase the competitiveness of this power-to-gas technology.

Simulating the electrical demand variations of air-source heat pumps in Canadian single-family housing

Heat pumps offer an efficient electrification of space heating but can significantly vary the magnitude and duration of house-level electrical demand, especially when replacing fuel-fired heating systems. This paper uses a simulation-based approach to simulate the electrical demand variations of air-source heat pumps (ASHPs) in six Canadian cities (Halifax, Montreal, Toronto, Winnipeg, Vancouver, Whitehorse) when replacing natural gas or electric baseboard heating. Detailed housing models (including a highly zoned model capturing room-based baseboard controls) are combined with a series of custom non-HVAC load profiles and an enhanced data-driven ASHP model to assess the variation that occupancy, climate, and type of heat pump integration can have on electrical demand. ASHPs are shown to increase the magnitude and duration of electrical demand when replacing natural gas furnaces, although selection of climate-appropriate systems (e.g. cold climate units in colder climates) may reduce the magnitude and coincidence of this demand. Where heat pumps replace electric baseboards, HVAC demand may decrease by up to 3.4 kW during ASHP operating periods and remain equal when the ambient temperatures are below the ASHP cutoff. A study of simple mitigation measures through varying temperature setpoints demonstrates the ability of proper controls to reduce electrical demand during high-demand periods.

Determinants of the adoption of energy efficient water heaters in the residential sector: Evidence from a survey in Japan

The purpose of this paper is to explore the determinants that promote the replacement of water heaters with more energy efficient models (e.g., gas or electricity-based energy efficient water heaters). By using survey data on Japanese households' water heater choice collected from an online questionnaire, this paper examines the effect of peers, choice context, and households’ perception of energy sources. The following results are obtained: First, households tend to choose gas or electricity-based energy efficient water heaters which, at the point when the households start to consider replacement, are known to have been used by peers (peer effect). Second, households are more likely to choose a gas or electricity-based energy efficient water heater in the context where they simultaneously replace their water heater and other home facilities (context effect). Finally, as for electricity-based energy efficient water heaters, households with a positive (negative) perception of electricity are more (less) likely to choose an electricity-based energy efficient water heater (perception of energy sources). These results imply the importance of considering these factors when designing policy instruments to promote the adoption of energy efficient water heaters in the residential sector.

General Modeling of Interconnected Hubs in Series and Parallel Structures

Energy decision-makers have considered solutions to meet the demand for affordable and highly reliable energy due to population growth and technological advancement. One of these possibilities is the utilization of several energy carriers in one system as an energy hub. Instead of optimizing a single energy carrier, the energy hub optimizes a system with many energy carriers, including electricity, natural gas, and local heat, by use of its converters and storages. In this paper, a novel and new general framework is proposed to evaluate and compare both series and parallel connections of n hub to analyze cost and reliability aspects by considering coupling matrices. In order to compare the outcomes of the connections of several comparable hubs in both series and parallel modes, new indices are proposed and evaluated from the aspect of evaluating the amount of energy not supplied and the amount of energy input to each hub. Additionally, simulations are run for a variety of scenarios in order to better assess the proposed model and investigate each type of connection by evaluating the proposed performance indices. The results show that in all the examined scenarios, the total cost of the energy carriers in the series mode (link in the output) is lower than in the parallel mode (link in the input).

МЕТОДЫ ЭНЕРГОСБЕРЕЖЕНИЯ ДЛЯ ТРУБЧАТОЙ ПЕЧИ

The main reasons for the low energy efficiency of tube furnaces are discussed. It was revealed that the main cause of heat loss is the inefficient use of the heat of flue gases. Ways to eliminate this problem are proposed

Plasma-based global pathway analysis to understand the chemical kinetics of plasma-assisted combustion and fuel reforming

The Global Pathway Analysis (GPA) algorithm helps analyze the chemical kinetics of complex combustion systems by identifying important global reaction pathways connecting a source species to a sink species through various important intermediate species (i.e., hub species). The present work aims to extend GPA algorithm to plasma-assisted combustion and fuel reforming systems to identify the dominant global pathways in such systems at various conditions. In addition, the present study extends the ability of GPA algorithm to identify reaction cycles involving the excitation of high-concentration species (e.g., O2, N2, and fuel) to their vibrational and electronic states and the subsequent de-excitation to their ground state, based on their significance on the reactivity of plasma-assisted systems in terms of gas heating and radical production. Provisions are made in the GPA algorithm to evaluate the reactivity of identified reaction pathways and cycles based on the element-flux transfer (i.e., dominance), heat release, and radical production rate. The newly developed Plasma-based Global Pathway Analysis (PGPA) algorithm is then used to analyze the plasma-assisted combustion of ammonia and reforming of methane. The PGPA analyses elucidated the significance of vibrational-translational cycles on the reactivity of NH3/air mixtures. Further, analyses on the production of NO ascribed the early reforming of NH3 to N2 and H2 in impeding the production of NO during plasma-assisted NH3 ignition. Lastly, the enhanced reforming of CH4/N2 mixtures using plasma has been attributed to electron impact dissociation of CH4 when compared to thermal reforming. In contrast, conventional path-Flux analysis (PFA) was found to require significant manual effort and pre-analysis intuitions from expert knowledge, making it arduous to provide valuable insights into plasma chemistry. The user-friendly and automated nature of PGPA thus provides a valuable tool for assessing the kinetics of plasma-assisted systems helpful in analyzing and, further, a foundation in reducing plasma-assisted chemistry, without the needs of expert knowledge.

Impact of Cooling Fluid Temperature on the Structural Integrity of Gas Turbine Stator Blades

The importance of gas turbine engines to the aviation industry cannot be overemphasized. Being a major part of aircrafts and jets, its reliability must be second to none. They are continuously subjected to extreme conditions during service making them the subject of constant studies. To produce the thrust and torque power required of them, they have to convert the intense heat and pressure inherent in hot combustion gases. To withstand the high combustion gas temperature without thermal failure, specialized materials and cooling are employed. This study numerically investigated the effect of cooling fluid temperature on the structural integrity of a (DS) GTD111 alloy gas turbine stator blade using COMSOL 5.5 software. Air was used as the cooling fluid in this study. The duct passages of the stator blade are significantly affected by the cooling fluid temperature values. Lower values of cooling fluid temperature proved beneficial for keeping the stator blade material below its metallurgical limit and is a positive for its total displacement, it however, negatively affects the yielding of the material. The cooling fluid temperature can be optimally selected to give optimal cooling effects in terms of total displacement and stress development. Based on this study, a cooling fluid (air) temperature of about 660 K will give optimal results. Internal cooling alone is not sufficient to produce the required cooling for turbine stator blades and this is evident in the output of the study, thus, coating and film cooling must be carried out to prevent thermal failure during service.

A canonical numerical experiment to study detonation initiation from colliding subsonic auto-ignition waves

The collision of two subsonic auto-ignition fronts with initial constant velocity was found to transit to detonation only when the collision angle was acute. The interaction of the reactive phase wave with inert hot layers constituted a singularity providing a continuous source of vorticity due to barocline effect. For an acute angle, this singularity that propagated at supersonic speed induced oblique pressure waves, of which resonance, due to the reactivity gradient geometry, near the center of the channel in the fresh gases accelerated the reactive wave fronts until transition to detonation. The numerical results of the present study, even if based on drastic assumptions, were at least in good qualitative consistency with experiments. The geometry of the reactivity gradients can thus provide another seed for the coupling between gas dynamics and heat release. Continuous pressure fluctuations and oblique shocks coming from vorticity sources and sheets from barocline effects can considerably enhance this transition. This path to transition could be complementary to that invoking mixing burning within premixed non-planar turbulent flame brush.

ASSESSMENT OF METHODS FOR DETERMINING THE NATURAL GAS HEAT OF COMBUSTION

The shortage of fuel and energy resources, the increase in natural gas prices and the continuous increase in gas consumption indicate the relevance of the issues of measuring the natural gas amount and assessing its quality indicators. Ukraine is implementing the European methodology for calculating gas consumption based on its quality and efficiency. The problem of determining the gas quality in Ukraine requires a thorough assessment and research.
 The main physical and chemical indicator of the natural gas quality, which characterizes its energy value, is the specific volumetric gas heat of combustion. The value of this parameter differs for different gas fields. The gas heat of combustion determines the efficiency of its use both in everyday life and in industry.
 The aim of the work is to analyze the main methods for determining the calorific value of natural gas.
 The gas heat of combustion is determined by calorimetric, chromatographic and correlation methods.
 The calorimetric method is characterized by the complexity of the measurement process, complete combustion of the test gas, and long term process. This ensures the objectivity of the results, which is based on taking into account the moisture content of the gas and the presence of non-combustible components in it.
 The basis of the chromatographic method is the separation of the components of a gas sample in a chromatographic column. The result is a chromatogram that shows the percentage composition of hydrocarbons in the gas. The characteristic properties of the method are the identification of a wide range of components and the repeatability of the results.
 When using correlation methods for determining the heating value of natural gas, various physicochemical parameters of samples are measured (such as total hydrocarbon concentration, heat capacity, acoustic wave propagation velocity, carbon dioxide concentration, thermal conductivity, dielectric constant, dynamic viscosity, and others).
 Correlation dependence is based on the choice and association of such parameters. This dependence is studied on different test gas mixtures and allows us to determine the empirical dependence. The mixtures correspond to gases with different calorific values. The obtained empirical dependence is used to register the heat of combustion of real natural gas. The paper evaluates the features of these methods application and instruments based on them.