Flow Calorimeter Research Articles

A fluid temperature interpolation method for wide temperature range distributed flow calorimeter.

The distributed flow calorimeter is employed to measure reaction enthalpy, mixing enthalpy, and other thermodynamic parameters of hydrocarbon fuels. This information serves as a foundation for selecting and developing hydrocarbon fuels for hypersonic flight. The fluid temperature in the tube is a key factor in characterizing its thermodynamic behavior. Given the challenges of monitoring fluid temperature within a tube using current flow calorimetry, a distributed method for calculating fluid temperature in tubes under high-temperature conditions is proposed. This method realizes the interpolation of the enthalpy function of the experimental fluid through several sets of experiments with varying power levels. The fluid temperature in the tube is calculated by considering the microelement as the research object. First, the methodology for calculating fluid temperature in narrow pipes across a wide temperature range is presented. Second, the simulation model of the flow calorimeter is established, and the methodology is verified through numerical simulation. Finally, a flow calorimetric experimental device is setup. N-decane was used as the fluid in the experiment, and the temperature was calculated, and the calculated results were compared with the NIST data. In the temperature range of 295.50-609.38K, the relative error range of the calculation of n-decane temperature is -0.61% to 1.24%. The experimental results show that the method can effectively estimate the fluid temperature of the distributed flow calorimeter.

Experimental investigation and thermodynamic modeling for isobaric heat capacity of ethanol at elevated temperatures and pressures

Ethanol is a promising sustainable fuel for its environmental friendliness and renewability. Due to the association effect in ethanol molecules, the particular behavior in isobaric heat capacity was explored by combining experimental and theoretical methods. Experimental isobaric heat capacity measurements of ethanol were performed over the temperature range from (298.15 to 573.15) K and at pressures up to 15 MPa in both liquid and vapor phases by a flow calorimeter. Different association schemes were combined respectively with PC-SAFT equation of state and SAFT-VR Mie equation of state to compare their accuracy in isobaric heat capacity prediction, and it could be concluded that two-site (2B) model was better than three-site (3B) model. It was also found that PC-SAFT equation of state was able to yield good results in predicting the isobaric heat capacity far from the saturated state and critical region, however, SAFT-VR Mie equation of state showed better prediction performance near the saturated state and critical region.

Determining kinetics of fast exothermic reactions using a flow calorimeter

Continuous flow calorimeters are considered an emerging technique due to their ability to reduce safety issues associated with highly exothermic rapid reactions. In this study, a custom-made isoperibolic flow calorimeter was constructed, which uses a pyroelectric IR Sensor for temperature profile recording. The objective of this study is to validate the reactor concept for the determination kinetic parameters. Residence time distribution (RTD) analysis was conducted to assess the mixing performance of the packed-bed reactor employed in the calorimeter. This calorimeter was connected to a custom-made conductivity flow cell (CFC), to measure the in-line conductivity of the outlet stream. An axially dispersed plug flow reactor model (AD-PFR) is required to be able to incorporate the non-ideal behaviour of the flow. The experimental apparatus design and methodology was validated by conducting the hydrolysis of acetic anhydride. The activation energy, EA and the pre-exponential factor, ln(k0) for the hydrolysis of acetic anhydride were found to be 52.05 kJ mol−1 and 12.26 (s−1), respectively, which falls within the range of reported values. The new flow calorimeter proved to be effective, and accurate.

Isobaric Heat Capacity Measurements of Methanol by Flow Calorimeter at Elevated Temperatures and Pressures

Isobaric Heat Capacity Measurements of Methanol by Flow Calorimeter at Elevated Temperatures and Pressures

Densities and isobaric heat capacities at high pressures of aqueous solutions of 2-diethylaminoethanol (DEAE) or 2-ethylaminoethanol (EAE) for CO2 capture

Densities and isobaric heat capacities of DEAE + H2O and EAE + H2O systems are presented in this paper. Density measurements were carried out at high pressure (up to 100 MPa) and temperatures from (293.15 to 393.15) K, with amine mass fractions of 0.1; 0.2; 0.3 and 0.4. These data were gathered using a vibrating tube densimeter (Anton Paar DMA HPM) with a relative expanded uncertainty of ±0.1 % (k = 2). A non-adiabatic quasi-isothermal flow calorimeter was used for isobaric heat capacity measurements with a relative expanded uncertainty better than 1 % (k = 2). Measurements reached pressures up to 25 MPa, and temperatures from (293.15 to 353.15) K, with amine mass fractions of 0.1; 0.2; 0.3 and 0.4. Both amine DEAE + H2O and EAE + H2O systems show a density and isobaric heat capacity decrease with amine mass fraction increase. Density data as a function of temperature, pressure and molality were fitted using a modified Tammann-Tait empirical equation of state. Furthermore, isobaric heat capacity data were correlated using an empirical function of temperature and amine mass fraction, but not pressure due to its lack of sensitivity in the measured data. Both correlations are in good agreement with the uncertainties. Comparison with experimental density data available in literature showed lower deviations than the associated uncertainties. Our isobaric heat capacity experimental data agree well with the scarce literature.

The isobaric specific heat capacity and viscosity for 3,3,3-trifluoroprop-1-ene in liquid phase at temperatures from (230 to 293) K and pressures up to 8 MPa

In this paper, the 65 isobaric specific heat capacity (cp) and 9 viscosity (η) data of 3,3,3-trifluoroprop-1-ene (R1243zf) were measured at temperatures from (230 to 293) K and pressure up to 8 MPa using a flow calorimeter and a vibrating-wire viscometer. The uncertainty of temperature, pressure, isobaric specific heat capacity and viscosity were evaluated to be less than 11 mK, 0.02 MPa, 1.0 % and 2.7 %, respectively. Three saturated liquid viscosity (ηs) data were obtained based on the extrapolation of the viscosity data. Empirical correlations were established based on the cp and ηs data, the average absolute relative deviation for cp and ηs are 0.5 % and 1.3 %, respectively.

Cage Nanofillers' Influence on Fire Hazard and Toxic Gases Emitted during Thermal Decomposition of Polyurethane Foam.

Polyurethane (PUR), as an engineering polymer, is widely used in many sectors of industries. However, the high fire risks associated with PUR, including the smoke density, a high heat release rate, and the toxicity of combustion products limit its applications in many fields. This paper presents the influence of silsesquioxane fillers, alone and in a synergistic system with halogen-free flame-retardant compounds, on reducing the fire hazard of polyurethane foams. The flammability of PUR composites was determined with the use of a pyrolysis combustion flow calorimeter (PCFC) and a cone calorimeter. The flammability results were supplemented with smoke emission values obtained with the use of a smoke density chamber (SDC) and toxicometric indexes. Toxicometric indexes were determined with the use of an innovative method consisting of a thermo-balance connected to a gas analyzer with the use of a heated transfer line. The obtained test results clearly indicate that the used silsesquioxane compounds, especially in combination with organic phosphorus compounds, reduced the fire risk, as expressed by parameters such as the maximum heat release rate (HRRmax), the total heat release rate (THR), and the maximum smoke density (SDmax). The flame-retardant non-halogen system also reduced the amounts of toxic gases emitted during the decomposition of PUR, especially NOx, HCN, NH3, CO and CO2. According to the literature review, complex studies on the fire hazard of a system of POSS-phosphorus compounds in the PUR matrix have not been published yet. This article presents the complex results of studies, indicating that the POSS-phosphorous compound system can be treated as an alternative to toxic halogen flame-retardant compounds in order to decrease the fire hazard of PUR foam.

Thermokinetic analyses of metal-sensitive reactions in a ceramic flow calorimeter

A ceramic flow calorimeter for metal-sensitive reactions is characterized and used to obtain thermokinetic data on highly exothermic reactions.

Influence of char‐forming lignin in combination with aluminium phosphinate on thermal stability and combustion properties of polyamide 11 blends

AbstractPolyamide 11 (PA) blends based on char‐forming industrial lignin and aluminum phosphinate (AlP) were prepared to improve flame retardant (FR) properties using a green and eco‐friendly approach. This study investigates the thermal degradation and combustion behavior of PA blends prepared by using AlP in combination with two different types of industrial lignins (i.e., kraft lignin (DL) and lignosulphonate lignin (LL). Thermogravimetric (TG) analysis showed that ternary blends containing LL and AlP developed higher char residue up to 10.7 wt% upon decomposition in inert atmospheres. The combination of lignin and AlP increases the thermal stability by shifting the initial decomposition temperature (T5%) and temperature at maximum decomposition (Tmax) to a higher temperature range, attributed to the stabilization of decomposition products. Furthermore, combustion behavior studied by cone calorimeter (forced combustion) and pyrolysis combustion flow calorimeter (PCFC) tests presented a significant reduction in the peak of heat release rate (PHRR) and total heat release (THR). It was found that LL and AlP‐containing blends more effectively decreased fire parameters like PHRR and THR than that of DL and AlP‐containing blends. The best interaction with reduced fire‐retardant properties was obtained when 10 wt% loading of lignin (DL/LL) and AlP was used. The reduction in heat release parameters was mainly ascribed to the condensed phase mechanism by forming an efficient protective char layer, which acts as a barrier against heat and mass transfer between the condensed and the gas phases. Raman spectroscopy analysis also confirmed the formation of the protective graphitic layer in the condensed phase.

Nebivolol in oral subacute treatment prevents cardiac post-ischemic dysfunction in rats, but hyperthyroidism reduces this protection: mechanisms involved.

Nebivolol could prevent dysfunction in patients suffering myocardial ischemia. However, influence of hyperthyroidism is not known. Consequences and mechanisms of nebivolol treatment were investigated in isolated hearts from euthyroid (EuT) and hyperthyroid (HpT) rats. Rats were orally treated during 1 week with 20 mg/kg/day nebivolol (O-Neb), 30 mg/kg/day atenolol (O-Ate), or not treated (C). Isolated perfused hearts were exposed to global ischemia and reperfusion (I/R) inside a flow calorimeter. Left diastolic ventricular pressure, developed contractile pressure (P), and total heat rate (Ht) were continuously measured, while infarct size was measured after 2-h R. EuT-C and HpT-C hearts developed similarly low post-ischemic contractile recovery and economy (P/Ht). Nebivolol totally prevented dysfunction and reduced infarction size in EuT hearts, but partially improved recovery in HpT rat hearts. Contrarily, oral atenolol totally prevented dysfunction in HpT hearts but partially in EuT hearts. Nebivolol effects were reversed by perfusing L-NAME in both conditions, but partially reduced by aminoguanidine in HpT. However, L-NAME increased P and P/Ht recoveries in EuT-C and HpT-C rat hearts, as well as melatonin. Oral nebivolol prevented post-ischemic dysfunction and infarction in EuT hearts due to adrenergic β1 blockade and activation of iNOS and/or eNOS, but the effect was attenuated in HpT hearts by excessive iNOS-dependent nitrosative pathways.

Research of the Thermophysical Properties of CFRP with Different Reinforcements by Methods of a Stationary Heat Flow and Differential Scanning Calorimeter with Temperature Modulation

Research of the Thermophysical Properties of CFRP with Different Reinforcements by Methods of a Stationary Heat Flow and Differential Scanning Calorimeter with Temperature Modulation

Flame retardancy of sustainable polylactic acid and polyhydroxybutyrate (PLA/PHB) blends

Nowadays, development of new biobased/biodegradable polymers from biological resources is of great interest from a sustainability standpoint. Polyhydroxybutyrate (PHB) and polylactic acid (PLA) are two biopolymers obtained from renewable resources. In this study, the flame-retardant effect of a newly developed flame retardant (FR) based on melamine in a PLA/PHB blend was studied. Several combinations containing this new FR combined with ammonium polyphosphate (APP) and sepiolite were introduced in a PLA/PHB blend. 20 wt% of FR were introduced into a matrix containing 75 wt% PLA and 25 wt% PHB blended with a microcompounder. According to pyrolysis combustion flow calorimeter (PCFC) analyses, all the FR formulations exhibited reduced flammability. The results revealed a considerable decrease in the peak of heat release rate (pHRR) by 33 % in the presence of the new FR while a reduction of about 60 % for combinations with APP and sepiolite. The new FR system significantly enhanced the fire behaviour of PLA/PHB blend. The work presents the first cone calorimeter analyses of PLA/PHB composites. The fire behaviour evolved from thin sample to a thick charring behaviour highlighted by an increase of the residue after cone calorimeter from 0 to 14.7 % with this FR system.

How phosphinated hydroxyurethane groups improve chemical resistance and flame retardant properties of alkyd resins?

A novel phosphorus containing polyhydroxyurethane (PHU) oligomer (DGGDAC-MXDA-DOPO), has been synthetized and grafted onto the remaining acid groups of alkyd resins in order to obtain hybrid poly(alkyd hydroxyurethane) (PAHU) resins with flame retardant properties. PAHU resins have demonstrated better alkali resistance than pure alkyd resins without PHU oligomer. Moreover, the grafting of PHU onto alkyd resin through the formation of amide bonds has exhibited thixotropic properties. The thermal and flame retardancy properties have been investigated through differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. The alkyd resins were applied as a coating on a wood surface and fire behavior was tested by cone calorimeter analysis. The most effective coating, by taking into account, the film properties and the flame retardant behavior contains 24 wt% of PHU (1.5 wt% P) and exhibited a 40% reduction in peak of Heat Release Rate (pHRR) compared to the resins without PHU.

Incorporation of Fly Ash in Flame-Retardant Systems of Biopolyesters.

The incorporation of fly ash in polybutyl succinate (PBS) and polybutyl adipate terephtalate (PBAT) in the partial replacement of ammonium polyphosphate and/or melamine polyphosphate is evaluated in the present work. Furthermore, the influence of the surface modification of fly ash with two silanes and titanate coupling agents was also studied. Cone calorimeter experiments, pyrolysis combustion flow calorimeters (PCFCs), and UL94V tests were used to assess the fire performance of the composites. Scanning electronic microscopy, X-microanalysis, and X-ray diffractometry analysis were carried out on cone calorimeter residues in order to access the fire-retardant mode of action. The formation of new components due to the presence of fly ash was highlighted by X-ray diffractometry, indicating the synergistic effects between the flame-retardant system and fly ash. The X-microanalysis results showed that the main fraction of initial phosphorous is present in the cone calorimeter residue, indicating that the proposed system acts in a condensed phase.

Triple Benefits of Cardanol as Chain Stopper, Flame Retardant and Reactive Diluent for Greener Alkyd Coating

Cardanol, a waste from the food industry and widely produced (1 Mt/y), has been used as a chain stopper during the polycondensation of short oil alkyd resins in order to replace benzoic acid. Then, phosphorylated cardanol has been added in order to both reduce solvent content and bring flame-retardant (FR) properties to the alkyd resins. The renewable carbon content of the formulations has been increased up to 23%. The impact of the introduction of phosphorylated cardanol molecules on the drying time and flexibility has been studied as well as the thermal and flame-retardant properties by differential scanning calorimeter, thermogravimetric analysis and pyrolysis-combustion flow calorimeter. The most effective flame-retardant coating that was associated with excellent FR properties and excellent coating properties has been obtained with phosphate-cardanol added at 2%wt of P. Indeed, the film properties were closed to the classical alkyd resin, the solvent content was reduced by 50% and the pHRR decreased by 42% compared to the reference alkyd resin.

Heat capacities of different amine aqueous solutions at pressures up to 25 MPa for CO2 capture

A high-pressure flow calorimeter is used to determine isobaric heat capacities for aqueous solutions of some amines such as MEA, DEA TEA, DMAE, MDEA, PZ from T = (293.15 to 353.15) K and up to 25 MPa. The experimental device can measure heat capacities with an estimated total uncertainty better than 1% for a coverage factor k = 2. The isobaric heat capacity values are analysed in conjunction with their temperature and pressure dependencies. Furthermore, empirical equations are proposed to fit isobaric heat capacities as functions of temperature and pressure for given conditions, for this kind of mixtures, obtaining standard deviations within the uncertainty of the measurements. Finally, DMAE shows the highest value of heat capacity and TEA the lowest value, when they are compared at the same conditions of temperature, pressure and composition.

Use of fly ash as synergistic and reactive component of flame retardant system in polylactide

For a long time, fly ash has been considered as pure waste of coal power plants. Nevertheless, unique properties and compositions that vary with the material's origin make fly ash appealing as an engineering material in various applications. Thus, the opportunity to reduce the environmental footprint of polylactide through the incorporation of fly ash as a component of flame retardant systems has been investigated. Combinations of fly ash with ammonium polyphosphate and/or melamine polyphosphate were made for a global loading of 25 wt% with various rates of substitution of the flame retardants. Fire performance has been studied from cone calorimeter experiments as well as the use of pyrolysis combustion flow calorimeter (PCFC) and the UL94V test. The interpretation of the fire retardant mechanisms has been performed through the examination of cone calorimeter residues by scanning electronic microscopy, X-ray microanalysis, X-ray diffraction (XRD) and multinuclear solid-state NMR. It can be shown that fly ash is mainly composed of spherical particles which are thermally stable at cone calorimeter tests when used alone in PLA. Conversely, fly ash behaves as a reactive component with both flame retardants, leading to the formation of new crystalline and amorphous compounds as shown by XRD and NMR. Synergistic effects in fire performance resulting from the reactive behavior of fly ash can be highlighted and are ascribed to fire retardant mechanisms acting in the condensed phase, and corresponding to the conservation of high phosphorus contents in the condensed phase.

Characterization of hemp fiber fire reaction

AbstractIntegrating bio‐resources in materials allows to reduce the environmental impact of the building industry. This study deals with fire‐retardant treatments, alternative to boric acid and ammonium salts solutions, applied to hemp fibers for thermal insulation application. The aim is to limit the energy, sanitary and environmental impacts of the treatment, while optimizing the technical performances. A laboratory protocol evaluates the flame‐retardant effect of the developed treatments. Treated fibers, including commercial treatments, are subjected to characterization tests: direct ignition small flame, thermal analysis (thermogravimetric analysis [TGA], differential thermal analysis [DTA]), pyrolysis‐combustion flow calorimeter and cone calorimeter. Some of the methods have been adapted to be applied to fibrous materials. The obtained results orientate the formulation of a treatment and highlight the complementarity of the analysis methods. Coupling the results, the ConeTools's predictive model leads to the estimation of the reaction to fire class according to the Euroclass. Euroclass C appears accessible with a tailored treatment.

Physicochemical fundamentals of processing solutions of thermoplastic poly(ether urethane)s to obtain fibrous-porous polymer composite materials

Objectives. To study the structure and properties of solutions of thermoplastic poly(ether urethane)s (PEUs) to inform their potential use in the production of fibrous-porous polymer composite materials with a given structure and set of performance properties depending on the field of practical application.Methods. The composition of PEUs was studied by attenuated total reflection infrared (ATR-IR) spectroscopy using a program for correcting the spectra on an IR Fourier spectrophotometer, as well by differential scanning calorimetry (DSC) using a heat flow calorimeter. The viscosity of PEU solutions was determined on a rotational viscometer.Results. The chemical composition of PEUs and the nature of the formation of hydrogen bonds were studied. An analysis of the spectra demonstrates the almost complete identity of the PEUs synthesized from the same 4,4'-diphenylmethane diisocyanate. In the studied PEUs of the Vitur and Desmopan® brands, as well as Sanpren, pronounced absorption bands characteristic of urethane groups involved in the formation of hydrogen bonds are visible in the region from 1702 to 1730 cm−1. The temperature transitions and thermal stability of the investigated PEUs were determined by DSC. The influence of the ratio of rigid and flexible blocks, as well as the nature of hydrogen bonds on the melting temperatures of polymers, was shown. Analysis of the DSC curves demonstrated all the studied PEUs to have high melting points ranging from 159 to 215°C. From the studied temperature dependences of the structural viscosity of thermoplastic PEUs solutions, all solutions were established to have a minimum viscosity anomaly; the value of the logarithm of viscosity depends on the chemical composition and structure of the initial PEUs. It is shown that the viscosity anomaly of PEU solutions can be reduced with increasing temperature.Conclusions. A comparison of the chemical composition, structure, thermal and rheological characteristics of thermoplastic PEUs with PEU solutions widely used for the production of fibrous-porous materials and coatings of Sanpren LQ-E-6 and Vitur R 0112 grades demonstrates their practicability as production materials and coatings having a predetermined structure and a set of properties depending on the requirements and operating conditions of finished products.

Influence of Phosphorus Structures and Their Oxidation States on Flame-Retardant Properties of Polyhydroxyurethanes.

This article focuses on the synthesis of polyhydroxyurethane (PHU) materials containing novel phosphorus flame retardants (FR). Four different phosphorus compounds were grafted onto cyclic carbonate: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), diethyl phosphite (DEP), diphenyl phosphite (DPP) and dibenzo[d,f][1,3,2]dioxaphosphepine 6-oxide (BPPO). Thus, three novel phosphorus reactive cyclic carbonates which have never been reported so far were synthetized. Phosphorus FR containing PHU materials were characterized by FTIR to evidence the total conversion of the cyclic carbonate. Moreover, the gel contents up to 80% confirmed the formation of the polymer network. Then, the thermal stability and the flame-retardant properties were investigated by thermogravimetric analyses, cone calorimeter and pyrolysis combustion flow calorimeter. The mode of action of phosphorus compounds, depending on the oxidation state, was especially highlighted. Phosphonate (+III) provided better action in a condensed phase than phosphinate thanks to a more efficient char formation. Among phosphonates, differences were observed in terms of char-formation rate and expansion. DEP provided the best flame-retardant properties, with a reduction of 76% of pHRR with 2 wt% of phosphorus in cone calorimeter analysis. Therefore, this article highlighted the different modes of action of phosphorus flame retardants, depending on the oxidation state of phosphorus, in PHU materials.