Thermal Response Parameter Research Articles

Simulation of an aircraft thermal management system based on vapor cycle response surface model

The modern aircraft Thermal Management System (TMS) faces significant challenges due to increasing thermal loads and limited heat dissipation pathways. To optimize TMS during the conceptual design stage, the development of a modeling and simulation tool is crucial. In this study, a TMS simulation model library was created using MATLAB/SIMULINK. To simplify the complexity of the Vapor Cycle System (VCS) model, a Response Surface Model (RSM) was constructed using the Monte Carlo method and validated through simulation experiments. Taking the F-22 fighter TMS as an example, a thermal dynamic simulation model was constructed to analyze the variation of thermal response parameters in key subsystems and elucidate their coupling relationships. Furthermore, the impact of total fuel flow and ram air flow on the TMS was investigated. The findings demonstrate the existence of an optimal total fuel flow that achieves a balance between maximizing fuel heat sink utilization and minimizing bleed air demand. The adaptive distribution of fuel and ram air flow was found to enhance aircraft thermal management performance. This study contributes to improving modeling efficiency and enhancing the understanding of the thermal dynamic characteristics of TMS, thereby facilitating further optimization in aircraft TMS design.

Radiative ignition properties of food grains and surface temperatures at ignition

Fire safety of food grains in storage, transport and processing facilities requires knowledge of their ignition properties some of which have been determined in this study. Cowpea, lentils, millet, soybean, unshelled peanut, flax (linseed), sunflower, shelled peanut and sesame, at 10% moisture content were studied. A cone calorimeter heater was used to impose radiative heat fluxes of 25, 35 and 47.5 kW/m2 on the food grains to determine the time to piloted ignition concurrently with the surface temperature at ignition ( Ts,ig). Ignition temperatures ( Tig) were calculated from experimentally determined critical heat fluxes. The thermal response parameter and thermal inertia ([Formula: see text]) essential for the characterization of the ignition of the food grains were also calculated. Thermal response parameter appears to be best suited for distinguishing the ignitability of the food grains. Ignition temperatures range between 239°C and 305°C, while thermal response parameter varies between 261 and 565 kWs0.5/m2. Small particle-sized grains showed higher ignitability.

Dual-excitation decoding multiparameter-based ratiometric luminescence thermometry: a new strategy toward reliable and accurate thermal sensing

Luminescence thermometry can perform noninvasive thermal sensing with high spatial resolution and fast response, emerging as an exciting field of research due to its promising applications in biomedicine. Nevertheless, because of the interaction between light and complex tissues, the reliability and the accuracy of this technique suffer serious interference, which significantly restricts its practical utilization. Here, a strategy to implement effective luminescence nanothermometry is preliminarily proposed by employing the different thermal responses between Yb 3 + → Nd 3 + and Nd 3 + → Yb 3 + energy transfer processes. Different from the traditional ratiometric sensing method, where two luminescence intensities are used as the thermal response parameters, we use two intensity ratios between Yb 3 + and Nd 3 + near-IR emissions that are obtained under dual excitation as the detecting and reference signals to perform temperature measurement. This multiparameter-based, self-reference thermometry technique, as we define it, exhibits excellent immunity to the influences arising from the fluctuation and loss of pumping sources as well as the luminescence attenuation in media. High thermal sensitivity ( ∼ 2.2 % K − 1 ) and good resolution ( ∼ 0.35 ° C ) are successfully achieved here, accompanied by a measurement error of ∼ 1.1 ° C in a biological environment test, while large errors are observed based on the traditional ratiometric approach ( ∼ 8.9 ° C , ∼ 23.2 ° C ). We believe the viewpoint in this work could boost luminescence thermometry and provide an ingenious route toward high-performance thermal sensing for biological systems.

Thermal response analysis and parameter prediction of additively manufactured polymers

Fused Deposition Modelling (FDM), is an additive manufacturing technology where polymers are extruded using appropriate processing parameters to achieve suitable bonding while ensuring that overheating does not occur. Among processing parameters, polymer inlet temperature, nozzle size, extrusion speed, and air cooling speed are significantly effect on the extrusion process at the distance between the build plate and the nozzle tip (standoff region). This study aims to evaluate the influences of the processing parameters on the thermal behavior and phase change zone of Polyamide 12 (PA12) and Acrylonitrile Butadiene Styrene (ABS) polymers at standoff region. A nonlinear three-dimensional (3D) finite element (FE) model was developed by implementing an apparent heat capacity model using the Heat Transfer Module in COMSOL® Multiphysics software. FE results in the standoff region were validated by experimental tests, concerning various nozzle sizes and extrusion speed. The validated numerical results demonstrated that there is a complex correlation between processing parameters and thermal behaviors such as phase change and temperature distribution in the standoff region. The FE results were then employed in training an artificial neural network (ANN). A well-established compromise between the trained ANN and the FE results demonstrates that the trained ANN can be employed in the prediction of further thermal and glass transition behavior using subsequent processing parameters.

Incorporating temperature-dependent fish bioenergetics into a Narragansett Bay food web model

Food web models capture shifting species interactions, making them useful tools for exploring community responses to disturbances. The inclusion of environmental drivers, such as temperature, can improve model predictions, as energy demands of an organism can be temperature specific. While mass-balance models such as Ecopath with Ecosim (EwE) and the R implementation, Rpath, have included some thermal responses in past work, models have yet to include temperature-dependent energetic demands and metabolic costs. Our work demonstrates the inclusion of temperature-dependent bioenergetics into an Rpath food web model using the case study of a warming estuary: Narragansett Bay (Rhode Island, U.S.A). Thermal response parameters from literature were used to construct Kitchell curves describing temperature-dependent consumption and modified Arrhenius curves describing temperature-dependent respiration. Surface water temperature time series from 1994 to 2054 for high and low warming scenarios were created using observed temperatures and projections from the Coupled Model Intercomparison Project (CMIP6) multi-model ensemble. The integration of temperature-dependent fish bioenergetics resulted in lower projected biomasses as energetic demands increased. The degree to which biomass was impacted varied by functional group, though piscivorous fishes were particularly affected as both that group and their prey groups had forced bioenergetic changes. The differences in the model-predicted biomasses highlight the importance of accounting for thermal effects on marine species in ecosystem models, which will become increasingly important as ocean temperatures continue to rise in Narragansett Bay and elsewhere.

IMPACT OF THE ELECTRIC CABLES INSTALLATION ON THE IGNITION PARAMETERS OF THE SPRUCE WOOD SURFACE

This study is aimed to investigate of an impact of electrical cables installed on Norway spruce (Picea abies(L.) Karst.) wood board surface on main ignition parameters (mainly critical heat flux, ignition temperature, thermal response parameter and thermal inertia). Ignition parameters have been determined by dependence of ignition times (raised to the power of -1, -1/2 and -0.547) on heat flux. Initiation times have been measured for three configurations of spruce wood boards with surface dimensions of 100 x 100 mm ± 1 mm (the first configuration: board without cables on surface, the second configuration: board with three electrical cables on surface -spacing between cables was equal to their diameter and the third configuration: board with five electrical cables -spacing between cables was equal to their diameter) at five heat fluxes (30, 35, 40, 45 and 50 kW·m-2). Obtained results proved that installation of the electrical cables on the spruce wood board surface has a significant impact on the ignition parameters. The critical heat flux (8.5 kW·m-2), apparent thermal inertia0.20 ± 0.02 kJ2·m-4·K-2·s-1and ignition temperature 324 ± 105°C of spruce wood board increased up to 18 ± 3 kW·m-2(critical heat flux), 0.68 ± 0.03 kJ2·m-4·K-2·s-1(apparent thermal inertia) and 475 ± 27°C (ignition temperature) by theinstallation of electrical cableson the surface of spruce wood board.

The Evaluation of Torrefied Wood Using a Cone Calorimeter.

This study focuses on the energy potential and combustion process of torrefied wood. Samples were prepared through the torrefaction of five types of wood: Ash, beech, oak, pine and spruce. These were heated for 2 h at a temperature of 300 °C under a nitrogen atmosphere. Torrefied wood was prepared from wood samples with dimensions of 100 × 100 × 20 mm3. These dimensions have enabled investigation of torrefied wood combustion in compact form. The effect of the external heat flux on the combustion of the samples was measured using a cone calorimeter. The observed parameters, include initiation times, heat release rate and combustion efficiency. The results show that increasing the external heat flux decreases the evenness of combustion of torrefied wood. At the same time, it increases the combustion efficiency, which reached an average value of approximately 72% at 20 kW m−2, 81% at 30 kW m−2 and 90% at 40 kW m−2. The calculated values of critical heat flux of the individual samples ranged from 4.67 kW m−2 to 15.2 kW m−2, the thermal response parameter ranged from 134 kW s0.5 m−2 to 297 kW s0.5 m−2 and calculated ignition temperature ranged from 277 °C to 452 °C. Obtained results are useful both for energy production field and for fire safety risk assessment of stored torrefied wood.

Effect of Different Dietary Electrolyte Balance Levels on Physiological Responses and Metabolic Rate of Rams Exposed to Heat Stress Conditions

This study was conducted to evaluate the effects of supplementation of different dietary electrolyte balance (DEB, as the equation of Na+K-Cl milliequivalents (meq) /kg of dry matter) levels on physiological responses and metabolic rate of rams exposed to heat stress and to determine which DEB level is the optimum. A total of 20 Farafra mature rams were used in this trail. These animals were divided into Four equal homogenized groups (5 each) as control (received basal diet only and its DEB was 98 meq/kg of feed DM), T1: DEB 200 meq/kg DM, T2: DEB 300 meq/kg DM and T3: DEB 400 meq/kg DM. Different DEB content of the three treatments was achieved by adding sodium bicarbonate by a rate of 0.74%, 1.48% and 2.22% of kg DM in T1, T2 and T3, respectively. Thermal response parameters, blood constituents, and respiratory activities were determined during the experimental period before (11-12 am) solar exposure and after 3 hours of solar exposure (3-4 pm). The results revealed that supplementation of different DEB levels reduced rectal and skin temperatures and respiration rate before and after solar exposure. However, gas volume per minute (GV) and tidal volume (TV) increased significantly in all treated groups. Volume of oxygen consumption (VO2) and metabolic rate tended to increase by treatment. Also, serum DEB level (Na+K-Cl) increased significantly in all treatments. In conclusion, supplementation of different DEB levels had beneficial effects on the thermal responses, respiratory activities and gas exchange parameters of heat exposed rams and the optimum DEB level is 300 meq/kg of DM.

Study on high-precision identification method of ground thermal properties based on neural network model

Accurately estimating ground thermal properties from thermal response tests (TRTs) is critical to design ground source heat pump system (GSHPS). The traditional method may lead to large errors due to the difference between the heat transfer process described by identification models and actual situation. To avoid it, this paper proposes a high-precision identification method based on artificial neural network (ANN), which can directly establish the nonlinear mapping relationship between thermal response parameters (TRPs) and ground thermal properties. Through the inversed orthogonal method, the training and validation samples are obtained from a large number of TRTs on a full-scale simulation platform that is verified by experiments. The estimation accuracy of traditional method and ANN under different ground thermal properties is studied. The results indicate that the estimation accuracy of traditional method varies greatly under different ground thermal properties, and the relative errors of identifying thermal conductivity and volumetric heat capacity vary from −3.61% to 60.14% and −52.06%–110.20% respectively. The estimation accuracy of ANN is almost not affected by the ground thermal properties, and the corresponding errors range from −7.78% to 0.28% and −1.75%–15.6% respectively. This paper provides a new perspective to reduce error caused by identification model.

Fire performance properties of commonly used South African hardwood

The effect of fire or heat and the associated fire hazards of South African hardwoods had been minimally researched. Quantitative investigations on fire performances of selected and common South African hardwood species that include Leadwood ( Combretum imberbe), Mopani ( Colophospermum mopane), Tamboti ( Spirostachys Africana), Stinkwood ( ocotea bullata), and Real Yellowwood ( Podocarpus latifolius) were undertaken using the cone calorimeter and the thermal gravimetric analysis instrument. The results indicated that Leadwood has the superior thermal performance. It has the lowest peak heat release rate (first peak at 156 kW/m2) at external heat irradiation flux of 75 kW/m2, highest thermal response parameter (376.2 kW s1/2/m2), highest thermal inertial (11.5 kW2 s/K2 m4), highest [Formula: see text], lowest fire growth index (derived from first heat release rate peak at 3120 W/s) and lowest smoke growth index (derived from first smoke production rate peaks at 0.760 m2/s2), and lowest smoke release (toxicity) 446.5 kg/kg. Bad thermal performance wood species are Mopani and Real Yellowwood. Stinkwood on the other hand has the best thermal stability from activation energy measurements.

Experimental study on vertical temperature profile of EPS external thermal insulation composite systems masonery façade fire according to JIS A 1310 method

SummaryThermoplastic Expanded Polystyrene (EPS) External Thermal Insulation Composite Systems (ETICS) has caused serious results due to the ravages of frequent fire disasters. The fire propagation over EPS ETICS surface was observed to be very fast. High temperature threatens the safety of exterior building wall. However, vertical temperature distribution of EPS ETICS façade fire (without cavity) is not available until now. Presently, a quantitative correlation was investigated through a series of theory derivation and experiment tests, which involves vertical temperature distribution of EPS ETICS façade surface, window fire intensity, thermal parameters and fire propagation potentials of EPS ETICS specimen. The theory consists of three parts, window‐spilled fire model, thermal parameters and fire propagation index (FPI) method. In JIS A 1310 standard tests, widow fire intensity changes from 600 to 1100 kW, thermal response parameter differs from 163.9 to 276.8 kW · s2/m2 and FPI varied from 17.1 to 28.9 (m/s1/2)/(kW/m)2/3. Finally, an adequate approximation for vertical temperature in the form of a dimensionless temperature is proposed based on test results. It provides a potential correlation to obtain vertical temperature distribution prior to the intermediate‐scale test.

Comparison of thermal and fire properties of carbon/epoxy laminate composites manufactured using two forming processes

AbstractCarbon/epoxy composites have been widely used in the aviation industry. However, the flammability of epoxy resins is of great concern within the industry. Currently, vacuum bag and autoclave forming processes are the most commonly used processes for composites. To compare the thermal and fire properties of carbon/epoxy laminate composites manufactured using these two forming processes, a comprehensive experimental investigation and theoretical analysis was carried out in this work. The glass transition temperatures and epoxy resin matrix content in composites were determined. Several thermal and fire properties were quantitatively evaluated, including onset decomposition temperature, time to ignition, mass loss rate (MLR), and heat release rate (HR). The morphologies of specimens before combustion were also observed. For vacuum bag (VB)‐C/ELC and A‐C/ELC, the critical heat flux (14.48 and 20.56 kW m−2), thermal response parameter (165.56 and 204.49 kW s1/2 m−2), heat of gasification (9.13 and 20.10 MJ kg−1), and theoretical heat of combustion (33.27 and 43.82 MJ kg−1) were calculated and compared using the thermal behavior model, MLR model, and heat release rate model, respectively. It has been found that the forming process can significantly affect the fire properties of carbon/epoxy laminate composites. More specifically, the carbon/epoxy laminate composites formed using autoclave forming processes have more combustion resistance and thus have improved fire properties.

Thermal decomposition characteristic parameters for the outer material of composite hydrogen storage tank by cone calorimeter

The thermal decomposition behaviours of the outer material of the high-pressure fully wrapped composite hydrogen storage tank were studied in cone calorimeter with a piloted ignition at various heat fluxes. The characteristic parameters, such as ignition time, mass loss rate, heat release rate and effective heat of combustion, were measured. In particular, the correlations of the ignition temperature, thermal response parameter, the heat of gasification and the heat of combustion were derived. The composite material satisfies the thermally thick model. The only one peak appears on the curve of MLR, HRR or EHC at the heat fluxes below or equal to 30 kW m−2, while one main peak and multiple small peaks appear at the heat fluxes greater than 30 kW m−2.

Critical Heat Flux Determination of Electric Cable Insulation

Abstract Electric cables can contribute to the spread of fire through the insulating layer. This paper focuses on their properties characterizing the initiation of fire. Samples of ethylene-based cable insulation were tested using a cone calorimeter by exposing them to external heat flows of six different values (25 kW m−2 – 50 kW m−2). Time to initiate flame burning was observed. The critical heat flux (depending on the method of calculation was in the range 2.94 kW m−2 – 4.59 kW m−2) and the thermal response parameter (342 kW s−0.5 m−2) was calculated from the time of initiation and external heat flow dependence.

Modeling the behavior of load bearing concrete walls under fire exposure

A generic three-dimensional (3D) finite element (FE) based numerical model is presented for predicting thermo-mechanical behavior of load bearing reinforced concrete (RC) walls exposed to fire. The proposed model is capable of accounting for critical parameters governing fire resistance of RC walls including wall slenderness ratio, support restrains, and temperature dependent properties of reinforcement and concrete. The model is validated by comparing predicted thermal and structural response parameters with the experimental data on three full scale load bearing RC walls tested under fire exposure. The comparisons show good correlation between model predictions and measured data, indicating that the proposed model can predict the thermo-mechanical behavior of RC walls from pre-loading to collapse stage under fire exposure. The validated model can be applied to undertake parametric studies aimed at quantifying critical factors governing fire performance of load bearing RC walls under fire.

Inverse heat transfer applied to a hydrogeological and thermal response test for geothermal applications

Actual thermal response tests, used to estimate the subsurface thermal conductivity in the geothermal domain, do not provide any estimate on the velocity of the groundwater flow and its orientation. These parameters are important for sizing geothermal borefield, since they influence the heat transfer around a geothermal borehole and the surrounding ground. To correct this shortcoming, a conceptual test has been developed in which heating cable sections inject heat in a borehole. Three temperature probes are strategically located at the borehole edge. This paper applies inverse heat transfer strategies to this thermal response test concept in order to identify the ground thermal conductivity, as well as the groundwater flow velocity and its direction. The suggested thermal response test and parameters estimation methodology are detailed. The influence of initial guessed values for the three unknown parameters was also studied. The work presented in this paper was carried out by numerical simulations.

Effect of concrete slab on the behavior of fire exposed subframe assemblies with bolted double angle connections

This paper presents the development of a three-dimensional nonlinear finite element model for evaluating the system-level transient fire response of double angle connections that are part of a sub framed assembly. The behavior of two subframe assemblies, with double angle connections, exposed to different fire scenarios were modeled using a commercially available finite element software ANSYS. The finite element model accounts for material and geometrical nonlinearities, degradation of constitutive material properties with temperature and non-linear contact interactions. The model is validated by comparing predicted thermal and structural response parameters of connection assemblies with measured data from fire tests on subframe assemblies with and without the concrete slab. The validated model is applied to study the effect of decay rate, loading type, presence of the concrete slab and degree of axial restraint on the fire performance of double angle connection assemblies. Results from the parametric studies indicate that decay rate, loading type and axial restraint have significant influence on the transient fire performance of subframe assembly. Further, presence of the concrete slab significantly enhances the rigidity of the connection assembly and mitigates local instabilities, such as local and lateral torsional buckling, that arise in beams and this improves the performance of connections.

Optimizing the position of insulating materials in flat roofs exposed to sunshine to gain minimum heat into buildings under periodic heat transfer conditions.

Building roofs are responsible for the huge heat gain in buildings. In the present work, an analysis of the influence of insulation location inside a flat roof exposed directly to the sun's radiation was performed to reduce heat gain in buildings. The unsteady thermal response parameters of the building roof such as admittance, transmittance, decrement factor, and time lags have been investigated by solving a one-dimensional diffusion equation under convective periodic boundary conditions. Theoretical results of four types of walls were compared with the experimental results available in literature. The results reveal that the roof with insulation placed at the outer side and at the center plane of the roof is the most energy efficient from the lower decrement factor point of view and the roof with insulation placed at the center plane and the inner side of the roof is the best from the highest time lag point of view among the seven studied configurations. The composite roof with expanded polystyrene insulation located at the outer side and at the center plane of the roof is found to be the best roof from the lowest decrement factor (0.130) point of view, and the composite roof with resin-bonded mineral wool insulation located at the center plane and at the inner side of the roof is found to be energy efficient from the highest time lag point (9.33h) of view among the seven configurations with five different insulation materials studied. The optimum fabric energy storage thicknesses of reinforced cement concrete, expanded polystyrene, foam glass, rock wool, rice husk, resin-bonded mineral wool, and cement plaster were computed. From the results, it is concluded that rock wool has the least optimum fabric energy storage thickness (0.114m) among the seven studied building roof materials.

Thermal degradation of epoxy resin/carbon fiber composites: Influence of carbon fiber fraction on the fire reaction properties and on the gaseous species release

SummaryThe thermal degradation of epoxy resin/carbon fiber composites has been performed in ISO 5660 standard cone calorimeter using a piloted ignition. Two kinds of composites that differ by their volume fractions in carbon fiber (56 and 59 vol.%) were tested in this study. The cone calorimeter irradiance level was increased up to 75 kW m−2 to characterize the carbon fiber volume fraction influence on the composite thermal degradation. Thus, main flammability and combustibility parameters were determined and calculated such as mass loss, mass loss rate, ignition time, thermal response parameter, ignition temperature, thermal inertia, and heat of gasification. As a result, all the characteristic parameters for the thermal resistance of composites were decreased when the carbon fiber volume fraction increased. Moreover, the main gaseous products (such as NO, CO, CO2, HCN, H2O, and lightweight hydrocarbons) emitted as well as the oxygen consumption during the composite thermal decomposition were also quantified simultaneously with a portable gas analyzer and a Fourier transform infrared spectrometer. The main species emission yields calculated from the gas analysis results increased slightly when the carbon fiber volume fraction was increased in the initial sample. The epoxy composite was represented as a sooty material with a significant production of soot particles during the combustion process. Furthermore, heat release rate, total heat release, and effective heat of combustion were calculated by using the oxygen consumption calorimetry technique. The results obtained showed that a small increasing of composite carbon fiber amount induced a sharp decrease of heat release rate and total heat release. Copyright © 2014 John Wiley & Sons, Ltd.

Thermal and chemical analysis of flammability and combustibility of fir wood in cone calorimeter coupled to FTIR apparatus

ABSTRACTThis paper deals with the thermal degradation of fir wood in a cone calorimeter under well‐ventilated atmosphere used with a piloted ignition. The thermal and chemical sample decompositions were studied with heat fluxes varying from 15 to 60 kW m−2. With the cone calorimeter results and equations found in literature, the significant parameters of fir wood sample flammability and combustibility were deduced from ignition time (tig), mass loss and gas analysis. These parameters are thermal response parameter, critical heat flux, ignition surface temperature, thermal thickness, mass loss rate, thermal inertia, effective heat of combustion, heat release rate, heat of gasification and others. Moreover, during each experiment, the main gaseous species emissions were continuously and simultaneously monitored. Furthermore, the solid degradation and combustion process for fir wood were described in details. Experimental results from cone calorimeter were compared with data found in literature, and generally, a quite good accordance was found between the both sets of results. Copyright © 2013 John Wiley & Sons, Ltd.