Amount Of Heat Release Research Articles

The Influence of Helium Addition on the Combustion Process in a Hydrogen-Fueled Turbulent Jet Ignition Engine

There are considerably fewer requirements for the quality of hydrogen combusted in an engine than its quality for fuel cells. Therefore, the analysis was carried out on the combustion of hydrogen–helium mixtures in an engine with a two-stage combustion system (TJI—Turbulent Jet Ignition). A single-cylinder research engine with a passive and active prechamber was used. A hydrogen–helium mixture was supplied to the main chamber in proportions of 100:0, 90:10, 80:20, 30:70, and 60:40 volume fractions. The prechamber was fueled only with pure hydrogen. Combustion was carried out in the lean charge range (λ = 1.5–3) and at a constant value of the Center of Combustion (CoC = 8–10 deg aTDC). It was found that the helium concentration in the mixture affected the changes in combustion pressure, heat release rate and the amount of heat release. It was observed that increasing the proportion of helium in the mixture by 10% also reduces the IMEP by approximately 10% and reduces the rate of heat release by approximately 20%. In addition, helium influences knock combustion. Limits of MAPO = 1 bar mean assumed that knock combustion occurs in the main chamber at values of λ < 1.9. Increasing the excess air ratio results in a gradual reduction in the temperature of the exhaust gas, which has a very rapid effect on changes in the concentration of nitrogen oxides. Studies carried out on the helium addition in hydrogen fuel indicate that it is possible to use such blends with a partial deterioration of the thermodynamic properties of the two-stage combustion process.

Combustion synthesis of the (Ti,Zr)B2-(Zr,Ti)C eutectic composites: Structure formation and properties

The macrokinetic characteristics of combustion of the quaternary Ti-Zr-B-C mixture as well as the mechanism and stages of phase formation for the synthesis products were investigated. The mechanical and thermophysical properties of the hot-pressed boride/carbide ceramics with eutectic composition (Ti,Zr)B2-43%at.(Zr,Ti)C were measured. Preliminary mechanical alloying (MA) of the (Zr + Ti) mixture was shown to yield Ti/Zr granules having a laminar structure and consisting of alternating layers of titanium, zirconium, and (Zr,Ti)ss solid solution. The method used to prepare reaction mixtures and the initial temperature T0 increased within the range of 20–370 °C have virtually no effect on combustion temperature, which is 2260–2400 °C, while higher T0 increases the combustion rate by a factor of 1.5–2. The use of MA Ti/Zr granules reduces the combustion rate as well as the specific heat release amount and the heat release rate. Time-resolved X-ray diffraction data showed that binary carbides (Zr1-xTix)C and diborides (Ti1-yZry)B2 of variable stoichiometry are formed in the combustion wave of the Ti-Zr-B-C reaction mixtures within less than 0.25 s. The carbide and diboride phases are formed simultaneously; the use of MA Ti/Zr granules in the reaction mixtures reduces the content of solid solutions of variable stoichiometry among the reaction products. The ceramics fabricated using a combination of combustion synthesis and hot pressing have a dense and homogeneous structure that consist of bonded grains of the diboride (Ti0.80Zr0.20)B2 and carbide (Zr0.83Ti0.17)C phases having the following properties: density, 5.3 g/cm3; hardness, 22.9 GPa; fracture toughness, 4.7 MPa m0.5; heat capacity, 0.52 J/(g·K); thermal diffusivity, 11.67 mm2/s; and thermal conductivity, 33.28 W/(m·K).

Thermodynamic cycle performance modeling and numerical simulation of higher Mach scramjet with inlet pre-injection

This paper focuses on the thermodynamic cycle performance modeling and numerical investigation of a high Mach number scramjet with inlet pre-injection of hydrogen. The scramjet model used in this study was the Hyshot-Ⅱ engine model. Flight experiments using this model at high Mach number have been conducted previously, which provides a unique testbed for validating the computational prediction of supersonic combustion. A thermodynamic cycle performance model with inlet pre-injection was developed for operating characteristics studies of the scramjet engine. A set of three-dimensional Reynolds average Navier-Stockes (RANS) simulations of the reactive flow was performed with a 9-specie and 19-step kinetic mechanism for hydrogen combustion. The turbulence is modeled by k-ω shear stress transport (SST) turbulence model. The thermodynamic cycle performance analysis results indicate that inlet pre-injection can enhance the hydrogen mixing efficiency, and a small amount of advanced heat release can improve the overall thermal cycle efficiency. Detailed flow analysis from the three-dimensional simulation results indicates flow can be ignited in the first shock wave induced boundary layer separation (SIBLS) region. Inlet pre-injection enables the propagation of the flame toward the core flow compared to the throat injection. The inlet fuel pre-injection proved to be a promising injection method due to the higher combustion efficiency, elevated from 0.75 to 0.85, and higher specific impulse potential, increased from 1570 s to 1810 s. As the ER of inlet pre-injection increases within the examined range, the performance curve exhibits an optimal point. As the geometric compression ratio increases, the entire combustion process advances, leading to a significant increase in the performance potential of the engine. The comparative analysis of the thermodynamic cycle performance modeling and computational fluid dynamics (CFD) modeling indicates the model shows a good prediction on the performance of the scramjet engine with the inlet pre-injection, with the same trend of performance curves and an error of less than 10 % compared to the numerical simulation.

Enhancing fire performance and thermal stability of flexible PVC with lanthanum phytate montmorillonite

This study presents a breakthrough approach to enhance the thermal stability, mechanical properties, and flame retardancy of flexible PVC (fPVC). It introduces lanthanide phytate montmorillonite (Pa-La-Mt) as an innovative nanofiller. Pa-La-Mt was synthesized by intercalating sodium phytate and lanthanum chloride into the interlayer space of montmorillonite (Mt), effectively increasing the layer spacing. The analysis of this study, using X-ray diffraction (XRD) and Fourier infrared spectrometer (FTIR), confirmed this structural transformation. The influence of Pa-La-Mt on the structural and performance aspects of fPVC composites was thoroughly examined. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), mechanical testing, limit oxygen index (LOI), and cone calorimeter (CONE) revealed compelling outcomes. Pa-La-Mt not only improved the dispersion and compatibility of Mt. within the fPVC matrix but also enhanced the thermal stability and mechanical performance of fPVC composites. Most notably, Pa-La-Mt exhibited remarkable flame retardant and smoke suppression effects on fPVC composites. It led to a substantial increase in LOI value, a reduction in the peak heat release rate and total heat release amount, and a decrease in CO and CO2 emissions. This underlines Pa-La-Mt as a promising nanofiller with profound implications for various fPVC applications.

Synergistic Modification of Polyformaldehyde by Biobased Calcium Magnesium Bi-Ionic Melamine Phytate with Intumescent Flame Retardant.

Intumescent flame retardants (IFRs) are mainly composed of ammonium polyphosphate (APP), melamine (ME), and some macromolecular char-forming agents. The traditional IFR still has some defects in practical application, such as poor compatibility with the matrix and low flame-retardant efficiency. In order to explore the best balance between flame retardancy and mechanical properties of flame-retardant polyformaldehyde (POM) composite, a biobased calcium magnesium bi-ionic melamine phytate (DPM) synergist was prepared based on renewable biomass polyphosphate phytic acid (PA), and its synergistic system with IFRs was applied to an intumescent flame-retardant POM system. POM/IFR systems can only pass the V-1 grade of the vertical combustion test (UL-94) if they have a limited oxygen index (LOI) of only 48.5%. When part of an IFR was replaced by DPM, the flame retardancy of the composite was significantly improved, and the POM/IFR/4 wt%DPM system reached the V-0 grade of UL-94, and the LOI reached 59.1%. Compared with pure POM, the PkHRR and THR of the POM/IFR/4 wt%DPM system decreased by 61.5% and 51.2%, respectively. Compared with the POM/IFR system, the PkHRR and THR of the POM/IFR/4 wt%DPM system were decreased by 20.8% and 27.5%, respectively, and carbon residue was increased by 37.2%. The mechanical properties of the composite also showed a continuous upward trend with the increase in DPM introduction. It is shown that the introduction of DPM not only greatly reduces the heat release rate and heat release amount of the intumescent flame-retardant POM system, reducing the fire hazard, but it also effectively improves the compatibility between the filler and the matrix and improves the mechanical properties of the composite. It provides a new approach for developing a new single-component multifunctional flame retardant or synergist for intumescent flame-retardant POM systems.

The effect of 1-octanol blending on the multi-stage autoignition of conventional diesel and HVO fuels

Alternative fuels can reduce the carbon intensity of diesel engine use, and a detailed understanding of the combustion process for these fuels can minimize resulting fuel consumption and emissions. 1-Octanol has been considered as an alternative diesel fuel, but little work evaluating its combustion process in detail exists. In this work, ignition of 1-octanol, both pure and in blends with conventional and renewable diesel base fuels, is analyzed in a constant volume combustion chamber and a modified Cooperative Fuels Research Octane Rating engine operating in homogeneous charge compression ignition combustion mode. 1-Octanol blending reduced the derived cetane number of either base fuel, but modest increases in chamber temperature at injection could compensate for even dramatic reductions in derived cetane number. It was further found that greater amounts of low-temperature heat release were required to reach main ignition as the 1-octanol blending volume fraction was increased in the constant volume combustion chamber. This finding is attributed to the changing local equivalence ratio, as the reacting spray diffuses further into the chamber and approaches the (lean) global equivalence ratio as the ignition delay grows. Finally, it was found that, despite lowering the derived cetane number, 1-octanol blending enhanced the reactivity of the conventional diesel fuel observed in the variable compression ratio engine. This finding is attributed to the higher rates of hydrogen abstraction from the weaker average C–H bonds in 1-octanol, as hydrogen abstraction governs intermediate temperature heat release. These findings clarify the effect of 1-octanol on physical processes and the various chemical regimes of heat release in compression ignition. The dependence of the effects of 1-octanol blending on the base fuel are emphasized, as these can inform the deployment of 1-octanol as a diesel blendstock. Application of these results can support the optimization of conventional combustion strategies for use with 1-octanol, as well as the development of 1-octanol-fueled low-temperature combustion strategies with the associated promise of very low criteria pollutant emissions.

Investigation of the influence mechanism of geometric throats in variable-geometry rocket-based combined-cycle combustors

To explore the reaction mechanism a geometric throat and its influence on the performance of the combustor, this paper studies the working process of a rocket-based combined-cycle (RBCC) variable geometry combustor with geometric throats under Ma4 inflow conditions by both numerical simulation and ground direct-connect testing. The main research contents and conclusions are as follows: (1) The geometric throat can accurately control the choking position. The fuel in the variable geometry combustor can complete the concentrated heat release and bring higher combustor pressure. The thrust of the geometric throat combustor is 8.7% higher than that of the thermal throat combustor. Therefore, the geometric throat combustor provides a better combustor performance than the thermal throat combustor. (2) When the throat area of the Ma4 configuration is adopted, the thrust and specific impulse in the combustor are at their the highest, reaching 6.0% and 0.4% higher than those of the Ma5 and Ma3 throat configuration combustors, respectively. This shows that a certain amount of combustor heat release needs to match the corresponding geometric throat area to ensure the optimal performance of the combustor. (3) In the Ma4 combustor configuration, after closing the primary rocket, the thrust in the combustor decreases by approximately 10.8%, but its specific impulse performance greatly improved by 39.3%. Therefore, the geometric throat can be used in the RBCC mode transition process in combination with the secondary fuel injection strategy to avoid the thrust trap in the mode transition process.

The role of turbulence in the characteristic velocity and length of rocket combustors

High-fidelity direct numerical simulations are conducted to investigate combustion performance in high-pressure methane-oxygen diffusion flames with different inlet turbulence. The results are post-processed to investigate the influence of turbulence on characteristic velocity and length. It is found that despite the eminent fuel-rich non-premixed configuration of the flame, a substantial amount of heat release takes place in premixed lean conditions. It is found that the occurrence of this phenomenon increases with the turbulent kinetic energy due to the mixing enhancement driven by the greater strain rate. The greater prevalence of lean combustion is beneficial for combustion performance near injection but detrimental for the completion of chemical reactions at downstream positions. It is found that excessive upstream oxygen consumption is responsible for this result. With more prevalence of lean combustion, oxygen is depleted sooner, and alternative reaction paths through carbon dioxide reduction are necessary to finalize the burning process. Moreover, it is observed that lower entry turbulence is beneficial for the downstream mixing intensity since it enhances the generation of radial velocity shear and flame-generated turbulence. The opposing effects of turbulence upstream and downstream determine the existence of optimal turbulence characteristics providing minimum characteristic length while achieving complete burnout. The combustion chamber volume savings associated with this optimal configuration are in the order of 50%.

Numerical Analysis of the Roof Slope Effect on the Building Thermal Comfort and the Need for Roofing Materials in Tropical Area

Roof is the most affected building envelope element by local climate changes such as solar radiation, rain, wind, etc. The design of a building's roof will have a significant impact on the building's thermal conditions and comfort. This study aims to numerically analyze and optimize the slope of a gable roof on an 8 m × 12 m residential building with 3 m walls located in a tropical climate region. The parameter analyzed in this parametric study on galvanized steel gable roofs is the slope angle impact in the interval between 150 to 450, with an angle increment at 50. The thermal aspect of the analyzed building is modeled numerically using the TRNSYS simulation tool coupled with CONTAM for aerodynamic modeling. The results showed that the greater the roof slope angle, the more comfortable the room condition was due to the amount of heat release that occurred in the attic zone before penetration into the occupation zone. Otherwise, the greater the angle of inclination, the greater the roof geometry that leads to construction material addition for the frame and roof covering. Therefore, it is necessary to perform numerical analysis to determine the optimal slope of a gable roof that provides maximum thermal comfort in a room with low roofing material requirements. Analysis and optimization of convective heat dissipation from the attic zone through natural ventilation or infiltration to reduce indoor thermal gain is an outlook for further research.

Strengthening Gold Extraction from Carbonaceous Gold Ore Based on Decarburization by Two-Stage Fluidized Oxidation Roasting

Oxidation roasting is one of the most effective methods to remove carbonaceous matter from carbonaceous gold ore. However, the consolidation of calcine is a common problem caused by a large amount of heat release during the oxidation roasting of gold ore with high carbon and sulfur content. In this study, a two-stage fluidized oxidation roasting method was developed to strengthen gold extraction. Pre-roasting was performed in a low oxygen environment for the mild combustion of carbonaceous matter, and then the pre-roasted product was subjected to secondary roasting followed by leaching. The results show that reducing the carbon content in the ore by pre-roasting can effectively lower the peak temperature inside the material. After the second-stage roasting, many cracks and pores were formed in silicates and carbonates, thus increasing the distribution of exposed gold from 28.95% to 88.01%. Finally, the extraction of gold increased from 4.55% to 86.10%. Overall, this study provides references for an efficient strategy for gold recovery from carbonaceous gold ores.

The kinetics of reentrant glass transition in metallic liquids

Reentrant glass transition is a new glass-transition phenomenon in which a devitrified liquid reenters a second glassy state and is well-known in some colloidal systems. Reentrant glass transition has been recently discovered in metallic-liquid systems but its ongoing mechanisms remain mostly unknown. Here, the reentrant glass transition of a series of Pd-Ni-P metallic liquids are investigated using fast-calorimetric analyses and ab-initio molecular dynamics simulation. While the amount of heat release of reentrant glass transition in different Pd-Ni-P liquids are similar, the change of liquid kinetics itself results in different reentrant-glass-transition behaviors: the transition kinetics is governed by the fast hopping of P atoms rather than the cooperative liquid motions related with vitrification. The reentrant glass transition is found to be related to medium-range structural ordering process through vertex-sharing of the P-centered polyhedral clusters. The kinetics map of liquid freezing for Pd-Ni-P glass-forming liquids over broad ranges of heating-rate and composition is presented.

Fire behaviour of a Carbon/Nomex honeycomb sandwich composite used in aircraft interiors as ceiling panel

AbstractFire behaviour of a carbon/Nomex honeycomb composite, used as ceiling panel in aircraft cabins, has been investigated experimentally. The thermal decomposition that was examined in a thermogravimetric analyser (TGA), under inert atmosphere, at several heating rates (5,10 and 20 °C/min), revealed a complex degradation process with overlapping stages. Cone Calorimeter tests at different incident heat fluxes, ranging from 20 to 70 kW/m2 have also been performed. The material exhibited good fire performance with relatively low amount of heat release and long ignition times. Ignition did not occur at 20 and 30 kW/m2. Combustion of the material at 40 kW/m2 proceeded in one stage, while at higher heat fluxes two stages were observed. The burning mechanisms and structural changes during thermal decomposition at different heat fluxes were also examined. The long tail after flameout in heat release curves and the significant increase in CO production and mass loss were analysed with respect to smouldering combustion of the material core. Measurements of the surface temperature prior to ignition were in agreement with the degradation processes observed in the TGA, and were also employed for the determination of ignition temperature (Tig = 593 °C). A modified iterative method, based on the correlation of the ignition data with the imposed heat flux, was adopted for the determination of the ignition parameters, including critical heat flux and temperature for ignition, providing results in agreement with experimental observations.

A Study on the Influence of Air Humidity on the Characteristic Parameters and Thermal Effect of Coal Spontaneous Combustion

ABSTRACT Air humidity has a significant effect on the characteristic parameters and heat changes of the coal spontaneous combustion process. In this study, a self-built precision humidity-generating device with adjustable humidity was used to investigate the effect of different humidity conditions on the spontaneous combustion process of coal. The release of indicator gases was determined by a humidity-generating unit in conjunction with a temperature-programmed device for coal oxidation, and the effect of air humidity on coal spontaneous combustion was studied from a macroscopic perspective. A quantitative study of the effect of air humidity on the heat released during the spontaneous combustion of coal was carried out by obtaining data for exothermic heat release intensity by conducting thermal analysis. Meanwhile, the numerical simulation method was used to study the influence of air humidity on the heat released during the coal spontaneous combustion process. The experimental results indicated that the introduction of moist air could significantly increase the oxygen consumption rate of the coal samples and promote the production of CO and CO2. In the slow oxidation stage, the air humidity has a greater effect on the heat release than that in the accelerated and fast oxidation stages. The simulated results of heat release in the slow oxidation phase are consistent with the experimental data, verifying that the moisture in the air can increase the amount of heat release and promote the coal-oxygen reaction. When the moisture in the air first came into contact with the coal, it released a large amount of adsorption heat in a short time, which increased the coal temperature.

Experimental investigation to study combustion and emission characteristics of diesel engine by application of EGR and heated intake air

Diesel engines are widely used over petrol engine due to their higher torque and higher thermal efficiency. However, the major problem of diesel engine is that it produces carbon dioxide which contribute in greenhouse gas emissions. The recent stringent norms about engine pollution needs to focus on the techniques to reduce the exhaust emissions. The exhaust gas loss is an important loss which affect the performance of engine fueled with diesel. The attempt of implementing systematic designed exhaust gas recovery system was examined for various test modes of diesel engine. A heat exchanger of counter current shell and tube type based heat recovery technique was developed and implemented to heat intake air of the engine and the effects of heated air on diesel engine characteristics studied. The exhaust gas recirculation(EGR) method was also employed for 6 % & 12 % EGR with and without heat exchanger and studied its effects on engine characteristics. The experimentation was conducted on kirloskar make four stroke diesel engine for varying load and at constant speed 1500 rpm for six different test modes of diesel including base diesel test mode. The six modes tested were 1: Base Engine (Diesel WHE) 2. Base Engine test mode withoutHeat Exchanger and with 6 % EGR (DIESEL WHE 6 % EGR) 3.: Base Engine test mode withoutHeat Exchanger and with 12 % EGRN(DIESEL WHE 12 % EGR) 4: Engine withHeat Exchanger (DIESEL HE 0 % EGR) 5: Engine test mode DIESEL HE 6 % EGR) 6. Engine test DIESEL HE 12 %EGR. The experimental results indicate that mechanical efficiency increased by 8.3 % for test mode of Diesel WHE 12 % EGR than base engine condition. The application of heat exchanger indicated improved CO2 emission in the engine exhaust The test mode of diesel WHE 12 % EGR reported higher in cylinder pressure and higher amount of heat release 52.5 J/ °CA at full load.

Relating Vertical Velocity and Cloud/Precipitation Properties: A Numerical Cloud Ensemble Modeling Study of Tropical Convection

AbstractFundamental relationships exist between cloud and precipitation development and their dynamic processes. Latent heat released by cloud/precipitation formation affects cloud vertical motions, which in turn affect convective cloud development. Here, a cloud‐resolving model is used to relate cloud properties and latent heating with cloud drafts using 15‐day simulations for an oceanic and continental environment. The results show condensation, deposition, and freezing occur mainly in moderate (3–5 m s−1) to strong (>10 m s−1) updrafts, evaporation and sublimation mainly in weak (1–2 m s−1) to moderate downdrafts, and melting in moderate updrafts and downdrafts. Active updrafts cover only a small percentage of the model domain but contribute significantly to the latent heat release and are associated with large proportions of the hydrometeors. Active updrafts with vertical velocities exceeding 1 and 2 m s−1 account for more than 75% and 50%, respectively, of the condensation, deposition, and freezing in both the oceanic and continental cases. However, active downdrafts with vertical velocity magnitudes exceeding |1 m s−1| account for less than 40% and 25%, respectively, of the evaporation and sublimation. More evaporation and sublimation than condensation and deposition occur in the inactive cloud regions. Sensitivity tests are also conducted to assess the impact of model grid spacing (1,000 m vs. 250 m) and microphysical schemes (3 ice classes vs. 4 ice classes) on latent heat release and hydrometeor amount. The results show that model resolution had more impact than the microphysics on the simulated cloud properties in both cases.

Surface heat transfer changes over Arctic land and sea connected to Arctic warming

AbstractTurbulent heat transfer from surface to atmosphere is important in the atmospheric energy balance over the Arctic, thereby impacting the remarkable warming that occurs in this region. The impact of heat transfer over the Arctic land and sea (approximate Arctic Ocean) on Arctic warming could be distinct, owing to different heat sources and physical processes on the interfaces. This study sought to analyse the heat transfer and changes over the Arctic land and sea and their contributions to those over the entire Arctic, and discuss the connection between the heat transfer changes and Arctic warming based on ERA5 reanalysis. The Arctic surface releases heat to the atmosphere, with an annual average of 4.5 × 1014 W, which is mainly contributed by the Arctic land in summer and sea in winter. From 1979 to 2018, the amount of heat release was found to markedly increase, with an annual trend of 0.94 ± 0.31 W/(m2 decade). A faster increase occurred in summer and was contributed by both the Arctic land and sea. In contrast, a slower increase occurred in winter and was only contributed by the sea. The heat transfer changed heterogeneously over the Arctic land and sea, with three major changes: Northern Russia Increase over northern Russia in summer, Northern Barents Increase over the northern Barents Sea in winter, and Nordic Sea Decrease over the Nordic Sea and northern Greenland Sea in winter. Notably, the heat transfer change over the Arctic land and sea could be connected to Arctic warming, especially the three major changes, based on distinct feedback processes, which could impact future Arctic warming. Overall, the Arctic land and sea play distinct roles in the heat transfer change and connection to Arctic warming, with the land being more important in summer and the sea being more important in winter.

Assessment of the Thermal Hazard Characteristics of Three Low-Temperature Active Azo Initiators for Polymer Resin in Construction Industries under Adiabatic Conditions.

Resins continue to occupy a place in the waterproof building market. Unlike traditional concrete building materials, the polymerization of resins requires initiators to support the required energy to drive the reaction or reduce the polymerization threshold, which shows a high reaction rate and low energy consumption in the polymerization process. Azo compounds (azos) are energetic substances commonly used in polymerization, but they can cause process hazards due to the amount of heat release and accumulation of the resulting heat. To ensure that similar hazards do not occur, the emerging azo initiators 2,2′-azobis(2-methylpropionamide)dihydrochloride (AIBA), 2-cyanopropan-2-yliminourea (CABN), and 2,2′-azodi(2-methylbutyronitrile) (AMBN) are explored. Depending on the process conditions, it is critical to examine how chemical reactions from a laboratory behave at a large scale. Kinetic models can be used to estimate fundamental safety parameters suitable for assessing the reaction hazards and as control measures, such as time to the maximum reaction rate under adiabatic conditions, time to the conversion limit, and runaway determination for process operation. The structure of this study is a combination of adiabatic calorimeter data and a nonlinear adiabatic dynamics model with the goal of helping to fill the void in research on thermal hazard analysis of emerging azo initiators. The adiabatic data is used to analyze the reaction mode characteristics of the azo compounds, and combined with the external environment, the reaction and temperature parameter changes of the azo compounds due to the reaction are discussed in the actual situation.

Exploring low-grade heat in exhaust gases with moisture via power generation cycles

Low-grade exhaust gases from industrial processes can be reutilised for electricity generation by ways of various thermodynamic cycles. Previous studies assumed that only sensible heat is available in the heat source. However, the presence of moisture is common, and as the moisture condenses, a significant amount of additional heat will be released for reutilisation. To gain further understandings to the influence of moisture in heat recovery, comparative analyses between a simple organic Rankine cycle and alternative cycles, including organic flash cycle, Kalina cycle, transcritical ORC and dual-pressure organic Rankine cycle has been carried out. The results show that with the presence of moisture, the net power output per kg/s of heat source flow increases significantly for all cycles examined. It is due to the large amount of latent heat release during moisture condensation process, that is not seen for dry gases. Among all cycles considered, the dual-pressure organic Rankine cycle shows the most convincing performance enhancement compared to a simple organic Rankine cycle, in terms of the cycle net power output. This is attributed to its flexibility to cope with both high and low-temperature heat sources. With a moisture content of 0.1 (mass fraction of moisture in the heat source), a dual-pressure organic Rankine cycle can achieve a performance enhancement up to 58%. As the moisture content further increases or decreases, its performance enhancement tends to reduce, although still noticeably higher than the simple organic Rankine cycle throughout the range of moisture content examined.

Studies on Red Mud Material to Use for Combustion of Vietnam Pulverized Coal

The catalytic effect of red mud on Vietnam anthracite’s combustion characteristics was investigated. The mineralogical composition of the red mud includes CaCO3, Fe2O3, FeO(OH), FeTiO3, and Al(OH)3. This red mud is rich in Na, Ca, Al, Fe, and Ti. The combustion characteristics were analyzed by the thermogravimetry method. The combustion effectiveness was assessed by thermogravimetric analysis. The results were derived from a combination of several parameters, such as the ignition temperature, the burnout efficiency, and the amount of heat release. The combustion characteristics of pulverized coal were improved by the introduction of red mud, and the greatest catalytic performance was achieved when the content reached 6%. With the optimal addition, the ignition temperature of anthracite was reduced by 12 °C, and the burnout efficiencies were increased by 2.59% compared to raw anthracite. The amount of heat released by anthracite was increased to 6.93 kJ/g by adding red mud.

Review: land, cloud, and climate change (in focus: Borneo)

This article discusses the salient findings of the Intergovernmental Panel on Climate Change Special Report on Climate Change and Land (2019). Local impacts of global warming in Borneo are discussed in terms of changes in temperature and precipitation. A drier and warmer climate is expected with the continued deforestation of Borneo. Changes in land surface characteristics of Borneo also affect the properties of cloud that forms over it. Deforested areas are generally associated with diffused clouds, small cloud particles, and thin and high clouds. Low vegetative areas are associated with a low evapotranspiration rate and low amount of latent heat release, which discourages the formation of convective clouds. The weak updraft associated with a non-convective cloud cannot support the formation of large cloud droplets. Moreover, the deforestation of primary forests of Borneo and replacing them with palm trees may cause larger cloud properties’ variability over the area.