Heat Release Behavior Research Articles

Heat Storage and Release Behavior of Chemical Heat Storage using CaCl<sub>2</sub> Hydration

Heat Storage and Release Behavior of Chemical Heat Storage using CaCl<sub>2</sub> Hydration

有機系収着剤を用いた蓄熱システムにおける放熱挙動

有機系収着剤を用いた蓄熱システムにおける放熱挙動

Simultaneous DSC/TG analysis on the thermal behavior of PAN polymers prepared by aqueous free-radical polymerization

A series of polyacrylonitrile (PAN) polymers with different content of itaconic acid (IA) as comonomer were prepared by an efficient aqueous free-radical polymerization technique. The thermal behavior of the PAN polymers was investigated by simultaneous DSC/TG analysis. Effects of IA content, heating rate and atmosphere on the heat release and weight loss behaviors of the PAN polymers were studied for insight of the nature of the thermo-chemical reactions. A specific triple exothermic peak was observed in the DSC curves of P(AN-IA) copolymers in air atmosphere. Three individual exothermic peaks were obtained by peak fitting and assigned to the respective thermo-chemical reactions, namely, ionic cyclization reaction, free-radical cyclization reaction and oxidation reaction. The ionic cyclization reaction was significantly influenced by the IA content. The free-radical cyclization reaction was sensitive to heating rate and atmosphere. The cyclization reaction preceded the oxidation reaction and acted as a prerequisite for the oxidation reaction. The improvement of the thermal stability of PAN was mainly attributed to the oxidation reaction through dehydrogenation and formation of oxygen-bearing groups. Mechanisms of the thermo-chemical reactions were also proposed and discussed.

Thermally conductive polyamide 6/carbon filler composites based on a hybrid filler system

We explored the use of a hybrid filler consisting of graphite nanoplatelets (GNPs) and single walled carbon nanotubes (SWCNTs) in a polyamide 6 (PA 6) matrix. The composites containing PA 6, powdered GNP, and SWCNT were melt-processed and the effect of filler content in the single filler and hybrid filler systems on the thermal conductivity of the composites was examined. The thermal diffusivities of the composites were measured by the standard laser flash method. Composites containing the hybrid filler system showed enhanced thermal conductivity with values as high as 8.8 W (m · K)−1, which is a 35-fold increase compared to the thermal conductivity of pure PA 6. Thermographic images of heat conduction and heat release behaviors were consistent with the thermal conductivity results, and showed rapid temperature jumps and drops, respectively, for the composites. A composite model based on the Lewis–Nielsen theory was developed to treat GNP and SWCNT as two separate types of fillers. Two approaches, the additive and multiplicative approaches, give rather good quantitative agreement between the predicted values of thermal conductivity and those measured experimentally.

Influence of deteriorated solvent on induction period of Grignard reagent formation

The influence of a degraded solvent on Grignard reagent formation was investigated in terms of heat release behaviour. Since degraded solvent is supposed to contain peroxide by oxidation with air as well as water from atmosphere, peroxide in this study was intentionally produced by the storage of tetrahydrofuran in a pressurized oxygen atmosphere and the induction periods were measured. The induction period which appears prior to the main exothermic reaction increased with increasing amounts of peroxide and water content, respectively. However, there was a difference in heat release behaviour; the reaction including peroxide showed a delay in the heat release and two exothermic peaks, while the solvent that included water simply showed a delay in the start of the reaction. γ-Butyrolactone was found to be a product derived from peroxide, by component analysis of the oxidized solvent. γ-Butyrolactone caused an induction period when it was added to the solvent. This work suggests a deteriorated solvent can lead to inappropriate handling which cause a runaway reaction and gives insight to the chemical industry that manages the risk of potentially hazardous chemical reactions.

G0600603 SrCl_2アンミン錯体形成時の熱移動速度

An ammine complex formation reaction with strontium chloride is promised to storage a waste heat up to 90 ℃ and to release its heat at atmospheric temperature up to 0 ℃. In this reaction system, heat transfer rate is an important factor in determining heat release performance. In this study, overall reaction rate of the reactant packed bed was measured using volumetric method to evaluate the influence of the thickness of the packed bed. As a result, the smaller thickness led to larger reaction rate. When the thickness of the packed bed was 2.5mm, the reaction time was 6 times or more long than that of 0.5mm. Besides, the heat resistance was quantified by another experiments as well as and the heat transfer simulation. As a result, the effective thermal conductivity of SrCl_2 packed bed was λ_<eff>=0.18W/m/K and thermal contact resistance was R_c=2.3×10^<-3>m^2・K/W. It was also found that the simulation results agree with the heat release behavior.

PLIF 및 자발광 계측을 이용한 이중선회 가스터빈 연소기에서 연소불안정 모드 연구

Inchan Choi, Keeman Lee, Mrinal Juddoo and A.R. MasriABSTRACTThis paper described an experimental investigations of combustion instability mode in a lean premixed dual swirl combustor for micro-gasturbine system. When such the instability occurs, a strong coupling between pressure oscillations and unsteady heat release excites a self-sustained acoustic wave which results in a loud, annoyed sound and may also lead a structural damage to the combustion chamber. The detailed period of flame behavior and heat release in combustion instability mode have been examined with high speed OH and CH-PLIF system and CH* chemiluminescence measurement, flame tomography with operated at 10 kHz and 6 kHz each. Experiment results suggest that unstable flame behavior has a specific frequency with 200 Hz and this frequency is accords with about 1/2 sub-harmonic of combustor resonance frequency, not funda-mental frequency. This is very interesting phenomenon that have not reported yet from other previous works. Therefore, when a thermo-acoustic instability with Rayleigh criterion occurs, the fact that the period of heat release and flame behavior are different each other was proposed for the first time through this work.

Research on Cutting-Temperature Field and Distribution of Heat Rates Among a Workpiece, Cutter, and Chip for High-Speed Cutting Based on Analytical and Numerical Methods

High-speed cutting is widely employed in aerospace, automotive, die, and other industries. However, no comprehensive mechanism of high-speed cutting behavior was as yet comprehended completely. Models of thermal sources and fields of cutting temperature are proposed for analysis of thermal equilibrium between heat generation and energy consumption at high-speed dry cutting. Mathematic models of cutting temperature for three cutting deformation areas are developed to analyze heat generation and release behavior in high-speed machining. The ratios of heat distribution among a chip, cutter and workpiece were found for different cutting speeds using the MATLAB software.

Autoignition of n-Butanol/n-Heptane Blend Fuels in a Rapid Compression Machine under Low-to-Medium Temperature Ranges

Ignition delay times of n-butanol/n-heptane mixtures (0%, 20%, 40%, 60% n-butanol in moles) were measured using a rapid compression machine at compressed pressures of 15, 20, and 30 bar, in the compressed temperature range of 650–830 K, and with equivalence ratios of 0.4, 1.0, and 1.5. Sensitivity analysis and reaction fluxes analysis were performed using a detailed mechanism of blend fuels so as to evaluate the impact of n-heptane addition on the ignition and combustion process. Over the experimental conditions in this study, the blend fuels display apparent low and high temperature reactions and a negative-temperature-coefficient (NTC) behavior; with increasing n-butanol mole fraction in the mixtures, the ignition delay times increased; the pressure curves present two-stage heat release behavior at low temperature but one-stage behavior at high temperature. It is worth noting that the n-butanol mole fraction shows negligible effect on the ignition delay times for equivalence ratios of 1.5 at low tempera...

Synergistic effect of expandable graphite, melamine polyphosphate and layered double hydroxide on improving the fire behavior of rosin-based rigid polyurethane foam

The halogen-free flame retardant rosin-based rigid polyurethane foams were successfully prepared based on renewable rosin polyester polyol, intumescent flame retardants (such as expandable graphite and melamine polyphosphate) and layered double hydroxide. The morphology, thermal conductivity, mechanical property, thermal stability, flame retardancy and fire behaviors of all RPUFs were comprehensively investigated. Furthermore, potential synergy between layered double hydroxide (LDH), expandable graphite (EG) and melamine polyphosphate (MPP) on fire behavior of rosin-based RPUF has been investigated in detail. XRD results showed that LDH is exfoliated and well dispersed in rosin-based RPUF. The results of SEM and thermal conductivity tests showed that adding intumescent flame retardants (such as EG and MPP) or further adding LDH into RPUF does not have significant influence on the cell structure and thermal conductivity of rosin-based RPUF. The results of TGA showed that adding EG, MPP or further adding LDH into RPUF decreases the initial decomposition temperature and the second-stage maximum-rate decomposition temperature of RPUF, while increases the char residue of RPUF at high temperature whether under N2 atmosphere or air atmosphere. Furthermore, it is noteworthy that simultaneously adding EG, MPP and LDH into RPUF can significantly improve the flame retardancy, mechanical property and fire behavior of rosin-based RPUF. The LOI value of EG10/MPP10/LDH3.0/RPUF sample increases from 19.1 to 28.0% compared to that of pure RPUF. The compressive strength and specific compressive strength (compressive strength/density) for EG10/MPP10/LDH3.0/RPUF sample in parallel direction increase about 8.3% and 7.1% compared to that of pure RPUF, respectively. The cone calorimeter test results showed that simultaneously adding EG, MPP and LDH into RPUF can significantly decrease the heat release rate (HRR), total heat release (THR) and smoke emission behavior of RPUF sample. The average heat release rate (Av-HRR) and total heat release (THR) decrease about 32.5% and 5.2% compared to that of pure RPUF, respectively. The average smoke production rate (Av-SPR), average rate of smoke release (Av-RSR), average specific extinction area (Av-SEA), total smoke release (TSR) and CO/CO2 weight ratio of EG10/MPP10/LDH3.0/RPUF sample decrease about 26.9%, 25.5%, 2.7%, 0.8% and 16.7% compared to that of pure RPUF, respectively. These test results indicating that LDH has synergistic effect with intumescent flame retardants (such as EG and MPP) on improving the fire behavior of rosin-based rigid polyurethane foam.

Comparative Autoignition Trends in Butanol Isomers at Elevated Pressure

Autoignition experiments of stoichiometric mixtures of s-, t-, and i-butanol in air have been performed using a heated rapid compression machine (RCM). At compressed pressures of 15 and 30 bar and for compressed temperatures in the range of 715-910 K, no evidence of a negative temperature coefficient region in terms of ignition delay response is found. The present experimental results are also compared with previously reported RCM data of n-butanol in air. The order of reactivity of the butanols is n-butanol>s-butanol$\approx$i-butanol>t-butanol at the lower pressure, but changes to n-butanol>t-butanol>s-butanol>i-butanol at higher pressure. In addition, t-butanol shows pre-ignition heat release behavior, which is especially evident at higher pressures. To help identify the controlling chemistry leading to this pre-ignition heat release, off-stoichiometric experiments are further performed at 30 bar compressed pressure, for t-butanol at $\phi$ = 0.5 and $\phi$ = 2.0 in air. For these experiments, higher fuel loading (i.e. $\phi$ = 2.0) causes greater pre-ignition heat release (as indicated by greater pressure rise) than the stoichiometric or $\phi$ = 0.5 cases. Comparison of the experimental ignition delays with the simulated results using two literature kinetic mechanisms shows generally good agreement, and one mechanism is further used to explore and compare the fuel decomposition pathways of the butanol isomers. Using this mechanism, the importance of peroxy chemistry in the autoignition of the butanol isomers is highlighted and discussed.

The influence of sodium and potassium hydroxide on alite hydration: Experiments and simulations

The basic nature of alkali hydroxides (NaOH, KOH) when added to mixing water, increases the pH in proportion to the level of salt addition. For alite (impure tricalcium silicate; MIII-Ca3SiO5) hydration, this pH increase accelerates the rate of hydration and reduces the duration of the induction, acceleration and deceleration regimes. This study evaluates alite hydration in solutions of varying compositions and alkalinities (0.1M, 0.2M and 0.5M NaOH and KOH) in context of their heat release behavior and analysis of the solid/liquid phases. The modeling platform, μic, is used to simulate, describe and discriminate the impact of the pore solution chemistry and reaction product formation parameters on alite hydration (Bishnoi and Scrivener, 2009 [1]). Numerical predictions of the solid and liquid phase compositions and the heat release response show good agreement with experimental determinations. The simulations indicate that the effects up to the end of the induction period follow directly from a change in the pore solution composition under a solution controlled dissolution mechanism, which leads to the faster precipitation of portlandite. The changes in the main heat evolution peak appear to be related to an increase in the nucleation density of C–S–H in alkali hydroxide solutions. Examination under the SEM did not indicate significant difference in C–S–H morphology and composition in the presence of NaOH/KOH.

Comparison of bismuth trioxide and antimony trioxide as synergists with decabromodiphenyl ether in flame retardancy of high-impact polystyrene

Flame-retardant additives used in plastics are based on halogen, phosphorus, inorganic compounds, and minerals. In this study, the use of bismuth trioxide as synergistic agent with brominated flame retardant is investigated and compared to formulations with antimony trioxide. Decabromodiphenyl ether and metal trioxide were incorporated in a polymer matrix via single-screw extrusion. The samples were classified with the UL 94 vertical burning protocol and studied with thermogravimetric analysis. The general combustion and heat release behaviors were studied via cone calorimeter. Results showed that 4% (wt) Bi2O3 displayed a synergistic effect with 12% (wt) of the halogen compound to achieve V-0.

Thermal risk assessment and grading of chemicals with instantaneous power density

The heat release behaviors of several chemical compounds were detected with C80 calorimeter. Furthermore, the thermodynamic and kinetic parameters of the chemicals were obtained based on the experimental data. Chemical thermal risk was simultaneously graded with combined use of instantaneous power density and the classification standard of thermal instability which was offered by the standard system for the identification of the hazards of materials for emergency response (NFPA704). The results show that the grading standard of thermal risk based on NFPA704 was reasonable and can be used as a preliminary thermal risk assessment for reaction hazards.

Synthesis, application and flame retardancy mechanism of a novel flame retardant containing silicon and caged bicyclic phosphate for polyamide 6

A novel flame retardant containing silicon and caged bicyclic phosphate groups, tri(2,6,7-trioxa-1-phosphabicyclo[2.2.2]octane-1-oxo-4-hydroxymethyl) phenylsilane (TPPSi) was successfully synthesized. The chemical structure of TPPSi was characterized by FTIR, 1H NMR and 31P NMR. The application of TPPSi (25 wt%) as a flame retardant in polyamide 6 (PA6) not only gains satisfied flame retardancy and smoke suppression, but also retains the high toughness and inherent appearance of pure PA6. The influence of TPPSi on the decomposition pathway of PA6 was discussed based on TG–FTIR and FTIR analysis. The interaction between TPPSi and PA6 at high temperature alters the decomposition pathway of PA6 resulting in the formation of the residue containing phosphorus and silicon. The heat and smoke release behaviors at different external heat fluxes were measured by cone calorimeter, and the fire residue was analyzed by SEM–EDX. The condensed phase action resulting from the barrier effect of residue is proposed to be the major flame retardancy mechanism of TPPSi in PA6, with the fuel reduction action as the minor.

Study on Heat Release Behavior of Pinus Biomass by TD-GC-MS

Pinus has been put into mass production. However, many heat release volatiles would produce air pollution during drying process. Therefore, the heat release behavior of Pinus biomass was studied by TD-GC/MS. The main constituents were at 100°С 1,4-methanoazulene,decahydro-4,8, 8-trimethyl-9-methylene-(30.6%), 1,4-methanoazulen-9-ol,decahydro-1,5,5,8a-tetramethyl-(14.85%), 1,2,4-methenoazulene, decahydro-1,5,5,8a-tetramethyl-(8.56%), 1r-.alpha.-pinene(7.92%), epiglobulol(4.57%), bicyclo[2.2.1]heptan- 2-one, 1,7,7- trimethyl-, (1r)- (4.33%), caryophyllene oxide(3.37%), etc. And the main constituents at 110°С were 1,4-methanoazulene, decahydro-4,8, 8-trimethyl-9-methylene-(40.31%), 1,4-methanoazulen-9-ol, decahydro-1,5,5,8a-tetramethyl-(15.35%), .alpha.-pinene(8.88%), bicyclo [2.2.1]heptan-2-one, 1,7,7- trimethyl-, (1r)- (5.73%), cyclohexane-1,3-dione, 2-allylamin omethylene-5,5-dimethyl-(5.24%), naphthalene, 1,1'-(1,2-ethanediyl) bis[decahydro-(4.83%), spiro[5.5]undec-2-ene,3,7,7-trime thyl-11-methylene-(4.05%), etc. The heat release volatiles of Pinus biomass was safe to people during drying process.

Study on Heat Release Behavior of Smoked Bamboo Biomass by TD-GC-MS

Smoked bamboo has been put into mass production. However, many heat release volatiles would produce air pollution during thermoplasticization process. Therefore, the heat release behavior of smoked bamboo biomass was studied by TD-GC/MS to make full use of and prevent the pollution of the volatile materials. The main constituents were acetic acid(43.95%), cyclotrisiloxane, hexamethyl-(15.89%), octasiloxane, 1,1,3,3,5,5,7,7,9,9, 11,11,13,13,15,15-hexadecamethyl-(8.22%), 1,3-benzodioxole, 5-(2-propenyl)- (4.8%), cyclodecasiloxane, eicosamethyl-(4.51%), etc at 100°С. And the main constituents were acetic acid(42.05%), 1-phenanthrenecarboxaldehyde,7-ethenyl- 1,2,3,4,4a, 4b,5,6,7,9,10,10a-dodecahydro-1,4a,7-trimethyl-(8.42%), bicyclo[2.2.1]heptan-2-one, 1,7,7-trimethyl-,(1r)- (8.12%), cyclotrisiloxane, hexamethyl-(6.17%), 1,3-benzodioxole, 5-(2- propenyl)-(5.26%), 4-nitro-4'-chlorodiphenylsulfoxide(3.13%), etc at 115°С. The heat release volatiles of smoked bamboo biomass might be used as biomedicines. Particularly, the volatiles had good application prospects and popularized value in purification of cedrol and acetic acid.

Study on Heat Release Behavior of &lt;i&gt;Cunninghamia lanceolata&lt;/i&gt; Biomass by TD-GC-MS

Cunninghamia lanceolata has been the dominated species of plantation forest in South China. And thermoplasticization can decreases the hydroscopicity to increase the additional value of Cunninghamia lanceolata biomass. However, many heat release volatiles would produce air pollution during thermoplasticization process. Therefore, the heat release behavior of Cunninghamia lanceolata biomass was studied by TD-GC/MS to make full use of and prevent the pollution of the volatile materials. The main constituents were cedrol(34.34%), phenol, 2,4-bis(1,1-dimethylethyl)( 11.49%), acetic acid(6.83%), carbon disulfide(3.1%), etc at 150°С. And the main constituents were acetic acid(20.22%), cedrol(17.20%), 1h-3a,7-methanoazulene, 2,3,4,7,8, 8a-hexahydro-3,6,8,8-tetramethyl-(3.58%), benzofuran, 2,3-dihydro-(3.26%), etc at 180°С. The heat release volatiles of Cunninghamia lanceolata biomass might be used as raw materials of bioenergy, rare biomedicines, and so on. Particularly, the volatiles had good application prospects and popularized value in purification of cedrol and acetic acid.

Oxidation of 1-butanol and a mixture of n-heptane/1-butanol in a motored engine

The oxidation of neat 1-butanol and a mixture of n-heptane and 1-butanol was studied in a modified CFR engine at an equivalence ratio of 0.25 and an intake temperature of 120 °C. The engine compression ratio was gradually increased from the lowest point to the point where significant high temperature heat release was observed. Heat release analyses showed that no noticeable low temperature heat release behavior was observed from the oxidation of neat 1-butanol while the n-heptane/1-butanol mixture exhibited pronounced cool flame behavior. Species concentration profiles were obtained via GC–MS and GC-FID/TCD. Quantitative analyses of the reaction products from the oxidation of neat 1-butanol indicate that 1-butanol is consumed mainly through H-atom abstraction. Among the H-atom abstraction reactions, it is observed that the H-atom abstraction from the α-carbon of 1-butanol is particularly favored. The investigation on the oxidation of the mixture of n-heptane/1-butanol showed that the oxidation of 1-butanol is facilitated at low temperatures through the radical pool generated from the oxidation of n-heptane.

Early-Age Properties of Cement-Based Materials. II: Influence of Water-to-Cement Ratio

The influence of water-to-cement mass ratio (w/c) on early-age properties of cementbased materials is investigated using a variety of experimental techniques. Properties that are critical to the early-age performance of these materials are tested, including heat release, semiadiabatic temperature, setting time, autogenous deformation, and strength development. Measurements of these properties using a single cement are presented for four different w/c, ranging from 0.325 to 0.425. Some of the measured properties are observed to vary widely within this range of w/c ratios. The heat release and setting time behaviors of cement pastes are contrasted. While early-age heat release is relatively independent of w/c, the measured setting times vary by several hours between the four w/c investigated in this study, indicating the fundamental differences between a physical process such as setting and heat release which is purely a quantification of chemical reaction. While decreasing w/c certainly increases compressive strength at equivalent ages, it also significantly increases autogenous shrinkage and may increase semi-adiabatic temperature rise, both of which can increase the propensity for early-age cracking in cement-based materials.