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The paper presents results of an experimental study of the suppression of thermal decomposition of forest fuel (FF) due to formation of a thin surface water film (3 mm thick). The investigations were carried out with birch leaves, as well as a mixture of birch leaves, pine needles, and twigs of aspen. The experiments involved model bases of fire of the above FFs in the form of cylinders. The cylinders were 20 mm to 60 mm in diameter and 40 mm to 100 mm high. The effect of water on the FFs was monitored via high-speed (up to 105 frames per second) video recording and fast (a thermal lag of less than 1 s) thermal transducers. The times of termination of FF thermal decomposition and the minimum (required) volumes of water were determined. The feasibility of complete suppression of the FF thermal decomposition process due to formation of a thin surface water film (10–15 times thicker than the reacted material) was experimentally supported. The foundations of the physical model of a complex of processes that occur owing to the water film effect on the forest fuel heated to a high temperature (well above the point of thermal decomposition) were formulated.

The study is aimed at investigating the thermal behavior and decomposition kinetics of torrefied oil palm empty fruit bunches (OPEFB) briquettes using a thermogravimetric (TG) analysis and the Coats-Redfern model. The results revealed that thermal decomposition kinetics of OPEFB and torrefied OPEFB briquettes is significantly influenced by the severity of torrefaction temperature. Furthermore, the temperature profile characteristics; Tonset, Tpeak, and Tend increased consistently due to the thermal lag observed during TG analysis. In addition, the torrefied OPEFB briquettes were observed to possess superior thermal and kinetic properties over the untorrefied OPEFB briquettes. It can be inferred that torrefaction improves the fuel properties of pelletized OPEFB for potential utilization in bioenergy conversion systems.

This paper is the first paper clarifying the causes and physical insight of the thermal-lag phenomena by presenting analytical solutions. The theoretical solutions presented are able to answer critical questions about the thermal-lag engine which have not been answered since it was proposed roughly thirty years ago. We find the criteria for onset of the thermal-lag oscillation in the engine. We confirm Tailer’s postulation that a thermal lag can be created to a certain extent by the imperfect heat transfer. We find that the thermal lag angles can be altered by artificially adjusting the geometrical and physical parameters. Finally, the influence of thermal lag on the indicated work output of the engine can be evaluated. In the present study, a nonlinear instability analysis is performed and theoretical solutions are carried out by perturbation method. In parallel, a prototype engine is developed and tested to partially verify the present theory. Experiments are conducted by measuring the displacement of piston under various heating temperatures and design parameters. Close agreement between the experimental data and the theoretical predictions, particularly in the steady oscillation regime, has been observed.

It is common for sample temperatures to be estimated by the power input to the furnace in multi-anvil experiments in which a thermocouple cannot be used or the thermocouple failed during heating. Uncertainties using this technique are often on the order of ±85°C or larger. This paper describes a new method for estimating sample temperature using a second thermocouple outside all pressure media. Temperatures recorded at this external (gasket) thermocouple trend linearly with the internal (sample) thermocouple temperature. Because of thermal lag, it is necessary to determine the first gasket temperature (T0) corresponding to the desired sample temperature. Accurate prediction of T0 for the desired sample temperature can come from relatively few (5–6) gasket-temperature measurements made during the initial temperature ramp over a small temperature range (500–600°C). Using this method and manually ramping to T0 allows for uncertainties in sample temperature estimation as small as ±20°C.

Slow crystallization kinetics and a limited thermodynamical stability of the target crystal phase are characteristic to zeolite formation, representing some of the key obstructions for fast zeolite synthesis. In this paper, the possibility of accelerating NaA zeolite synthesis in a continuous flow reactor (CFR) is studied. The CFR reduces the thermal lag by increasing surface to volume ratio, expediting heat transfer and mass transfer. The properties of the CFR and the reference batch synthesized particles were similar as confirmed by X-ray diffraction, scanning electron microscopy, particle size measurement using laser scattering and water adsorption equilibria. The reduced residence time and reduction in thermal lag provided an ideal synthesis environment for NaA zeolite, without side products, yielding 160 g/h per liter reactor volume of dry NaA crystals synthesized in 16 min and 2-3 mu m particles for a single CFR. In comparison, the batch process produces 33 g/h per liter reactor volume The effects of diluting with NaOH-solution and temperature were studied in the CFR, allowing to determine the optimal conditions. With the enhanced reaction kinetics gained from the increased temperature and molar composition, NaA synthesis is performed 10 times faster than in the optimal batch synthesis. The optimal conditions for the synthesis of NaA in the CFR were determined as: a gel composition of Na2O:4.75 - SiO2:1.93 - Al2O3:1.0 - H2O:192, at a synthesis temperature of 150 degrees C during 16 min without, aging of the gel mixture. This paper shows that the bottlenecks in NaA zeolite synthesis can be widened resulting in faster synthesis in a CFR, making it a feasible pathway for more controllable zeolite synthesis at higher mass production rates (160 g/(h l-reactor)) while reducing the risk of blockage in a continuous flow reactor. (C) 2016 Elsevier Inc. All rights reserved.

This paper presents the experimental investigation of the effect of ambient air humidity and temperature on thermal properties of the laterite rocks used in South-West coastal India. The experimental technique employed was transient plane source method in the saturated salt solution humidity controlled chamber. Experimental results showed an increase of thermal conductivity by 14.7% and specific heat by 9.15% with an increase in the relative humidity of ambient air in the hygroscopic range. A porous and ferruginous matrix of laterite was studied using a scanning electron microscope. The effects of relative humidity of the ambient air and temperature on the unsteady state thermal heat transfer characteristics such as transmittance, admittance, decrement factor, time lag, surface factor, surface factor time lag and heat capacity for different thicknesses of the laterite rock walls were investigated analytically. One dimensional heat flow equation under periodic convective boundary conditions was solved using matrix algebra and a computer simulation program which employs a cyclic admittance method was developed using MATLAB to compute unsteady state thermal characteristics. Results indicate that the decrement factor reduces by 8.35% and time lag increases by 2.88% with an increase in the relative humidity of ambient air compared to the dry state for the Indian standard laterite rock thickness.

The paper presents the pyrolysis behaviour of eleven different rank solid fuels, carried out using thermogravimetry (TG). Obtained experimental curves were compared with profiles determined using the Single First Order Reaction (SFOR) model and three different approaches of Distributed Activation Energy Model (DAEM). The aim of this work was to develop different models dedicated to pyrolysis, in particular further investigate the interrelation between the activation energy and the pre-exponential factor, its impact on the results quality and attribution with the fuel properties and pyrolysis mechanism. Obtained results showed that the compensation effect, often noted for SFOR, has also occurred for DAEM. Furthermore, analysis indicated an existence of a relationship between the characteristic temperature T iso (and ln( k iso )) and fuel properties. Observed interrelation may be attributed to the change in reaction mechanism.

In this study, a cardiac thermal pulse evaluation-based carotid artery stenosis detection method is proposed. It is postulated that the presence of stenosis in the carotid artery results in a thermal lag in skin temperature at the neck skin surface that can be quantified to the degree of stenosis. A finite volume method-based transient bioheat transfer study was performed on a carotid artery-jugular vein 3-Dimensional (3D) geometry model encapsulated by the neck tissue. As the transient physiological blood flow in the carotid artery thermally interacts with the blood perfusion in the neck tissue, a thermal fluctuation or cardiac thermal pulse is resulted in the top-neck skin localized surface temperature contours. Two tissue blood perfusion models, constant (temperature-independent) and varying (temperature-dependent), were used to comparatively study the cardiac thermal pulse characterized by their signal noise. For 0% stenosis case, compared to the constant perfusion model, the average instantaneous noise for the varying perfusion model was found to be significantly lower (0.02 ± 0.01 versus 0.05 ± 0.01, p

In this study, the potential application of activated carbon produced from oil palm kernel shell (OPKS) as the supporting material of paraffin to develop a form-stable composite PCM was investigated. The produced activated carbon managed to retain up to 31% of paraffin by mass. The prepared composite PCM was then characterized using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC) and thermal cyclic test. The experimental results showed that the melting and solidifying temperatures of paraffin-OPKS-activated carbon composite were 29.2 °C and 31.6 °C with a corresponding latent heat of 57.3 J/g and −57.2 J/g. Moreover, paraffin-OPKS-activated carbon composite also demonstrated good stability against thermal degradation, excellent chemical stability, stable phase change temperature with considerable latent heat and great thermal reliability. In addition, concrete incorporated with paraffin-OPKS-activated carbon composite could achieve a compressive strength up to 25 MPa at the age of 28 days. The laboratory scale thermoregulation performance test showed that concrete panels incorporated with paraffin-OPKS-activated carbon composite have a higher thermal lag and lower peak temperature during phase transition of composite PCM.

Wang, Y.; Luo, C.; Yang, S.; Ma, W.; Niu, W., and Liu, H., 2020. Modified thermal lag correction of CTD data from underwater gliders. In: Zheng, C.W.; Wang, Q.; Zhan, C., and Yang, S.B. (eds.), Air-Sea Interaction and Coastal Environments of the Maritime and Polar Silk Roads. Journal of Coastal Research, Special Issue No. 99, pp. 137–143. Coconut Creek (Florida), ISSN 0749-0208.A real-time data quality control process and a modified thermal lag correction procedure are proposed in this paper. The data quality control process is designed for CTD sensors (conductivity, temperature and depth) installed on Petrel gliders. A modified thermal lag correction methodology, based on the hypothesis that CTD data sampled closer in time and space would be more similar, is also put forward in this paper. Therefore, in this method, each down profile and each up profile is split into two segments. The segments with closer temporal and spatial relationships are used to calibrate each other, which is the first time the limitation of using only one profile to correct the thermal lag effect in a glider-carried CTD has been overcome. Moreover, the data obtained in sea trials with a Petrel glider and a reference SBE 911 plus CTD are used to examine the modified method and the newly designed data quality control process. The excellent alignment with the reference data and significant calibrations indicate that the CTD data were successfully corrected.

Differential Scanning Calorimetry (DSC) is a widely accessible and versatile method for the determination of the heat capacities of organic materials as a function of temperature. In routine use, it is typically possible to obtain results with an accuracy better than 3 %. However, to achieve this level of accuracy, careful optimization of the experimental procedure for a specific apparatus must be performed. Using benzoic acid as a test substance, this work highlights some practical aspects of heat capacity measurements by DSC, such as crucible material and its geometry, heating rate, thermal lag, the selection of a suitable pre-stabilization stage before the measurement and the duration of the experiment, that can have a strong influence on the quality of the obtained results.

Thermal pretreatments are used prior to optically stimulated luminescence (OSL) measurements in methods of dose determination, but the reproducibility of such heating appears to be poor within laboratories, and between laboratories. Monitoring the position of the 110 °C thermoluminescence (TL) peak in quartz can be used to routinely assess the reproducibility of heating within a repeated set of measurements on an aliquot (e.g. during the single aliquot regenerative dose protocol) providing feedback on whether changes in sample preparation can improve reproducibility. Poor reproducibility between measurements from a single aliquot are likely to arise from grains between the hotplate and sample holder. Variability between aliquots may also be affected by deformed sample holders. Differences between readers may also be caused by differences in the calibration of the hotplate. Reproducibility of heating can be improved within runs, and between instruments, by taking care to avoid loose grains, by removing deformed sample holders, and if necessary by calibrating hotplates. It is suggested that individual aliquots should only be accepted if the apparent 110 °C TL peak temperature within a sequence of measurements varies by 5 °C or less. Improving the reproducibility of thermal treatment is important in reducing scatter in equivalent dose determinations based on OSL from quartz, but also for signals such as TT-OSL from quartz, and the various feldspar luminescence signals. Temperature control is also critical for accurate kinetic analyses.

International audience; The modelling and prediction of heat transfer in fractured media is particularly challenging as hydraulic and transport properties depend on a multiscale structure that is difficult to resolve. In addition to advection and dispersion, heat transfer is also impacted by thermal attenuation and lag time, which results from fracture‐matrix thermal exchanges. Here we derive analytical expressions for thermal lag time and attenuation coefficient in fractured media, which quantify the effect of fracture geometry on these key factors. We use the developed expressions to interpret the results of single‐well thermal tracer tests performed in a crystalline rock aquifer at the experimental site of Ploemeur (H+ observatory network). Thermal breakthrough was monitored with Fiber‐Optic Distributed Temperature Sensing (FO‐DTS), which allows temperature monitoring at high spatial and temporal resolution. The observed thermal response departs from the conventional parallel plate fracture model but is consistent with a channel model representing highly channelized fracture flow. These findings, which point to a strong reduction of fracture‐matrix exchange by flow channeling, show the impact of fracture geometry on heat recovery in geothermal systems. This study also highlights the advantages to conduct both thermal and solute tracer tests to infer fracture aperture and geometry.

The objective of this study was to analyze a green roof by monitoring the variables that can influence it, comparing its effects to those of a conventional roof with clay tiles in Cascavel/State Paraná. The following parameters were compared in both prototypes: indoor temperature, outdoor temperature, relative humidity, wind speed and solar radiation. Temperature measurements were determined by sensors installed in the prototypes whereas the relative humidity was analyzed by wet bulb sensors. Data concerning to 30 days of experiment were collected and tabulated in Microsoft Excel. The green roof remained for 7 days within the relative humidity range considered comfortable whereas the conventional roof remained for 4 days. The green roof caused a mean reduction of 4.96°C, proving that green roofs contribute to reducing indoor room temperature and thermal lag promoted by the green cover, where the heat input takes longer to occur when compared to the conventional roof. Regarding the behavior of the vegetation cover and substrate, the larger the green cover, the lower the substrate temperature transmitted to the indoor environment.

Autoclave processing is one of the oldest and most widely used processing methods for high-performance composite materials. This chapter addresses important fundamentals of this processing method including autoclave equipment, gas flow and heat transfer, and aspects of autoclave design. Cure and property evolution of thermoset composite materials are discussed including polymerization, cure kinetics, glass transition temperature, liquid, rubbery and glassy behavior of the material, as well as material modeling and process simulation. The chapter ends with examples of how fundamental understanding of gas flow, heat transfer, and material property evolution can be used in the context of a process model to optimize processes with respect to the thermal response. Process simulation is used to evaluate the effect of autoclave equipment, tooling, part and material on thermal lag and exotherms in the process. Defects and mitigation strategies are also discussed.

The lamellar thickness distribution (LTD) of not-reorganized linear polyethylene was calculated on the basis of the melting point distribution using fast scanning calorimetry (FSC) by applying the following precautions. First, by taking sufficiently small sample mass and thickness, the influence of thermal lag during fast-heating is thought to be negligible. Second, by fast-heating, reorganization and cold crystallization are strongly hindered or even suppressed. Third, the influence of superheating has been accounted for and corrected by deconvolution of the FSC curve using the calculated melting kinetics of single-sized lamellae consisting of folded-chain crystal. Under such precautions, the resulting FSC heating curve reflects the melting point distribution of metastable-but-not-reorganized folded-chain crystals. Finally, the Gibbs–Thomson equation was applied to calculate the LTD from the melting point distribution. The average lamellar thickness calculated was in good agreement with that determined b...

Ignition and burnout temperatures are important properties of solid fuels for their applications in industry. In this study, the thermogravimetric analyses (TGA) of bamboo and sugarcane bagasse at five different heating rates of 5, 10, 20, 30, and 40 °C min−1 are performed. The intersection method (IM) and deviation method (DM) are employed to approach the ignition temperatures of the two biomass species, while IM and the conversion method (CM) are adopted to analyze their burnout temperatures. In IM and CM, both the ignition and burnout temperatures increase with increasing heating rate, as a consequence of the pronounced thermal lag in biomass particles at high heating rates. The measured ignition temperatures based on DM are lower than those based on IM, and there is no correlation between the temperature and heating rate. The determined burnout temperatures from IM are close to those obtained from CM, while the difference in the burnout temperatures of the two biomass samples is small. The ignition temperatures of the two biomass species measured from IM are between 250 and 300 °C, and their burnout temperatures are close to 500 °C. As a whole, IM is recommended for determining the ignition temperature of biomass, while CM is a feasible and simple route to approach the burnout temperature. The heating rates in TGA between 20 and 30 °C min−1 are suggested because of their accurate and time-saving operations.

The inclusion of PCM (phase change materials) for improvement of thermal energy storage is a current topic of study, particularly for domestic hot water accumulation. An experimental setup with a 100-L tank was implemented to assess the behaviour of these materials. The PCMs used in this work consist of three different hydrated salts with different encapsulations. An experimental methodology based on a steep thermal demand was developed to compare and study the energy contribution and thermal response of these materials. The calculated energy balance shows that the thermal lag of the three different PCM and encapsulations is less than expected, which means that after 14 min of a thermal demand in the range of 25–30 kW, over 90% of the PCM appears to have aided the response of the tank. In addition, the estimated thermal lag of the different PCM reflects the typical stratification pattern of the tank. This study demonstrates that the three different materials studied in this work (PCM A, PCM B and PCM C) are suitable for delivery of energy during the typical steep demand found in domestic heating, but if the expected response is delivery of heat for fast recovery of the tank, different encapsulations should be used. Finally, a viability analysis of employing these materials is carried out taking into account stability, availability and economic factors.

We present a complete set of freely available MATLAB/Octave scripts called the SOCIB Glider Toolbox (https://github.com/socib/glider_toolbox). This new toolbox automates glider data processing functions, including thermal lag correction, quality control and graphical outputs. While the scientific value of the glider platform has been proven, the experience for the glider data user is far from perfect or routine. Over the last 10 years, ocean gliders have evolved such that they are now considered as a core component of multi-platform observing systems and multi-disciplinary process studies; we now have a generic processing system that appropriately complements glider capability.In an ideal world, a simple connection to a glider would provide oceanographic data ready for scientific application in an intuitive, familiar format; the reality has been somewhat different. Up till now users have faced several time-consuming tasks that prevent them from directly and efficiently extracting new oceanographic knowledge from the acquired data. The SOCIB glider toolbox covers all stages of the data management process, including: metadata aggregation, raw data download, data processing, data correction and the automatic generation of data products and figures. It is designed to be operated either in real-time or in delayed mode, and to process data from two of the most widely used and commercially exploited glider platforms, Slocum gliders and SeaGliders. The SOCIB glider toolbox is ready to accelerate glider data integration and promote oceanographic discovery., The development of the toolbox benefited from the Perseus FP7 project

Coupled green-building roof system can assess bidirectional heat-flux with indoor space. Two high-rise residential blocks in humid-subtropical Hong Kong, with and without roof building thermal insulation (BTI), were monitored for thermal performance across seasons and weather conditions. Each block had three plots: Sedum and herbaceous Peanut green roofs, plus bare Control. Diurnal heat-flux data were partitioned into daytime and nighttime, and positive and negative fractions. On hot summer-sunny day, Control without BTI facilitates notable daytime influx and nighttime efflux of heat. Sedum augments thermal-mass effect pushing more heat indoor than Control. With balance between transpiration-cooling and heat-sink formation, Peanut registers intermediate heat gain. Adding BTI raises heat-gain and eliminates Control heat-loss, curtails Sedum heat-gain, and maintains Peanut heat-gain. BTI partnering with green roof offer synergistic thermal benefit by increasing thermal mass, thermal capacity and thermal resistance to furnish thermal buffering, thermal lag, and extending heat ingress to nighttime. Lower solar-radiation input on summer-cloudy day significantly trims heat gain at Control, with limited reduction at both green roofs. Summer-rainy day brings further drop in heat gain. For cloudy and rainy scenarios, heat-gain suppression is more notable with BTI. Interpretations for other season-weather conditions and implications of the findings are elaborated.

Hybrid rocket combustion frequently displays a sudden amplification of combustion pressures leading into low frequency instability (LFI) with peak frequency of 10 – 20 Hz . A series of experimental tests was designed to examine the triggering mechanism of LFI, which occurred at a certain combustion condition. To this end, a couple of parameters was selected and the sensitivity of each parameter to instability was evaluated including volume ratios between main and post chambers, oxidizer mass flow rates, and solid fuel types. The results showed that the initiation of LFI was related to the flow modifications caused by vortex shedding and volume ratios between main and post chambers. Once LFI was initiated at a certain chamber configuration, the variation of oxidizer mass flow rates and the use of different solid fuel did not alter the triggering mechanism of LFI. Additional attention was focused to understand the critical role of vortex shedding on the initiation of LFI in the post chamber. The results confirmed that pressure oscillations by the thermal lag of solid fuel could be suddenly amplified, which leads to LFI in the case of resonating with unknown sources of pressure oscillations associated with vortex shedding in the post chamber. However, the details of triggering mechanism and the coupling of vortex shedding with additional pressure perturbations still remain unresolved.

This paper develops an analytical solution for a generalized dual phase lag (DPL) model based on the nonequilibrium heat transfer in biological tissues during laser irradiation achieved by performing volume average to the local instantaneous energy equation for blood and tissue. The obtained energy equation is solved by employing the separation of variables and Duhamel's integral method for both absorbing and scattering tissues. The generalized DPL model anticipates different results than that of the predicted by the classical DPL and Pennes bioheat transfer (parabolic) models. It is found that the generalized DPL model calculates lower temperature than that of obtained by the classical DPL model due to considering heat convection between blood vessels and tissue. The obtained analytical results are also compared with existing numerical and experimental data to verify the accuracy of the analytical solution. The results indicate that the generalized DPL model reduces to Pennes bioheat transfer model when both thermal lag times are zero. It is shown that effects of blood perfusion rate, coupling factor and the lag time τT on the temperature response of tissue are similar. Furthermore, the comparison between the analytical results and existed experimental data shows that the present mathematical model is an efficient tool for evaluation of bioheat transfer in biological tissues.

Crystal melting behavior of indium and isotactic polypropylene has been examined by differential scanning calorimetry of heat flux type in terms of the heating rate, $$\beta $$ , dependence. The melting shows the dependence characterized by a power, $$z$$ , of the shift in peak temperature in proportion to $$\beta ^{\text{z}}$$ . The power, $$z$$ , differentiates the melting with and without superheating. For polymer crystal melting, intrinsic nature of the broad melting region with a fractional power, $$z\,\le\,1/2$$ , due to superheating of melting kinetics has been reconfirmed experimentally. On the other hand, the crystal melting of indium, which is supposed to proceed with negligible superheating, showed the shift in peak temperature with the power in the range of $$1/2\,\le\,z \le\,1$$ , depending on sample mass, which is due to instrumental thermal lag predicted by the Mraw’s model consisting of lumped elements. The $$\beta $$ dependence is influenced by the thermal lag determined by the thermal contact resistance between the sample pan and the stage, the effect of which has been examined in terms of the dependence on sample mass and the application of silicone grease between the sample pan and the stage. The influence of two different types of the definition of heat flow has also been examined; the simplified one without the time derivative of temperature difference showed an apparent shift in peak temperature at faster scan rates in a similar way as that of thermal lag.

In this study, the pore size distribution of silica aerogels is measured with thermoporosimetry and compared with results from cellulosic materials. The isothermal step melting method is shown to be a useful method to eliminate thermal lag and measures relatively large pores which have a small melting temperature depression. It is shown that for porous silica, pore volumes can be accurately measured by isothermal step melting and that pore diameter can be calculated from the Gibbs–Thomson equation. The nonfreezing water is found to be a monolayer on the pore wall, indicating that hydrated surface area may be probed with this method. The isothermal step melting method is also shown to be very useful to measure pore size distribution of cellulosic materials. However, the Gibbs–Thomson constant for cellulosic materials is markedly different than for porous silica. The pore size distribution for Kraft pulp fibers and for two types of nanocellulose is reported.

The thermal glass transition of polystyrene (PS) is measured in a range between 0.003 K/s and 4000 K/s using a conventional DSC 1 and a Flash DSC 1 from Mettler-Toledo. The dependency between the cooling rate and the glass transition temperature is in accordance with the Vogel–Fulcher–Tammann–Hesse (VFTH) equation, as it is usually used for description of the frequency–temperature relationship of the dynamic glass transition (or main relaxation process). Furthermore we discuss the influence of the thermal lag on the measurement and develop correction methods.

A quantitative evaluation has been tried on the thermal lags of a fast-scan (≤10 4 K s −1 ) microchip differential scanning nanocalorimeter (DSC). A thin layer (∼0.2 μm thick) of a standard material of Tin was vapor deposited on a thin film of polyethylene (PE) sample (∼1–10 μm thick), and the thermal lags have been examined by the dependences on the applied heating rate, film mass, and film thickness of the melting onset temperature of Tin on the bottom and top surfaces of PE films put on the sensor stage of nanocalorimeter. Thermal lags are comprised of the instrumental thermal resistance and the temperature gradient in the film. The instrumental thermal lag was detected by the melting of Tin on the bottom of PE films and well explained by the reported value of the thermal resistance of sensor. The temperature gradient in the film was detected by the melting of Tin on the top surface of PE films, and showed the dependence predicted by the modeling of heat transfer in the thickness direction. The influences of thermal lags have also been examined in terms of the heating rate, β , dependence of the shift in melting peak temperature of PE crystals. The power of β z characterizing the β dependence of the shift became larger with increasing film mass and thickness, i.e. with introducing larger thermal lags. When the power is utilized as a fitting parameter, the influence of thermal lags on the melting point extrapolated to zero heating rate could be kept at small level (±1 °C) even for thick films (∼10 μm). Those behaviors have been validated by numerical calculations based on the modeling of fast-scan microchip DSC.

This work relates to developing thermal protection for a finite period of exposure to a high temperature environment. This type of transient heat transfer problem starts with a heating period, which is then followed by a cooling period once the high temperature environment disappears. The study is particularly relevant to the thermal protection of flight data recorders from high temperature flame. In this work, transient heat conduction through a three-concentric-layer configuration is numerically studied, which includes a metal housing, a thermal insulation, and a phase change material. The thermal performance is evaluated using the center temperature changing with time. It is found that the center temperature reaches a peak during cooling period rather than heating period. Time taken to reach the peak and the peak value depend on the sizes and properties of the layers. The properties include latent heat of fusion, melting temperature, heat capacities, and thermal conductivities. Parametric study is conducted to analyze and distinguish the influence of these parameters. The study provides general guidance for determining sizes and selecting materials for the thermal design of flight data recorders. Additionally, the study is also useful for other similar applications, for which thermal management and protection over a period of time is needed. In this paper, analysis starts with a baseline configuration composed of specific materials and sizes. Finite changes are applied to sizes, properties of the materials, and the results are compared to understand the roles of the varied parameters in affecting the thermal protection performance.

In this work, glass transition temperature of polylactide obtained over a wide range of cooling rates is investigated. The kinetics associated with the glass transition measured upon cooling and the devitrification measured upon heating are discussed. Thermal lag corrections of the glass transition temperatures are detailed. A verification of thermal lag correction values is also proposed based on structural relaxation phenomena. The glass transition is characterized in terms of fictive temperature, fragility and structural relaxation in order to discuss the intriguing non-dependency of the polylactide fictive temperatures upon cooling for high cooling rates. To our knowledge, this intriguing phenomenon is reported and detailed for the first time by fast scanning calorimetry.

Heating and cooling of residential buildings consumes around ten percent of the world's energy. One approach for reducing these costs is to exploit the high thermal mass of sustainable building materials, for example rammed earth (RE), for intelligent solar passive design. However, there is a lack of scientific evidence about the thermal performance of RE houses in real-world settings.This research investigated to what extent thermal performance in unconditioned RE structures in rural Australia can be captured by current accreditation software. Two custom-designed houses were built in the hotarid city of Kalgoorlie-Boulder, Western Australia: one comprising traditional solid cement-stabilised rammed earth walls (RE) and the other walls with an insulating polystyrene core (iRE). Otherwise the houses were identical in orientation and design. The houses were instrumented to monitor indoor temperature and humidity conditions prior to and during occupancy. Results were compared to those simulated using cutting-edge assessment software BERS Pro (v4.3) as an example of that used for energy efficiency accreditation in Australia. This first paper in this series discusses the houses' construction and instrumentation and results obtained during the unoccupied period, i.e. those purely demonstrative of the structure's thermal performance. A second paper in the series presents data gathered during occupancy, to contrast occupant thermal comfort with that predicted numerically.Measured data showed that both houses performed nominally-identically: the houses did not receive any relative benefit from including iRE. Simulated data was also similar per house. However, measured performance did not match that simulated: simulated rooms had poorer thermal stability and lag and, consequently, exaggerated internal temperature variations. Collected data has been made publicly available for future analyses.

The present study’s main objective was to determine the applicability of organic phase change materials (PCMs) in a building’s envelope construction system for the passive provision of comfortable indoor thermal conditions over one year based on thermal inertia in Mexico City. Research on PCMs relate mainly to their use in building envelope construction systems to reduce energy consumption for mechanical indoor thermal conditioning—not in passive systems. Computer simulation results of mean indoor temperature variations are presented with the objective of evaluating these construction systems’ thermal inertia properties. In the present study, dynamic thermal simulations (DTS), using EnergyPlus software, of ten 1 m3 test units with envelope construction systems combining organic PCMs of different fusion temperatures with conventional materials were performed. Based on the results, it is concluded that the implementation of organic PCMs with a fusion temperature around 25 °C in combination with aerated concrete in a space envelope results in the highest number of hours the indoor temperatures remain within the comfort range throughout a typical year, due to the decrement of indoor temperature oscillations and, to a large extent, to thermal lag.

International audience; By means of fast scanning calorimetry, the glass transition of anhydrous amorphous starch has been measured. With a scanning rate of 2000 K s(-1), thermal degradation of starch prior to the glass transition has been inhibited. To certify the glass transition measurement, structural relaxation of the glassy state has been investigated through physical aging as well as the concept of limiting fictive temperature. In both cases, characteristic enthalpy recovery peaks related to the structural relaxation of the glass have been observed. Thermal lag corrections based on the comparison of glass transition temperatures measured by means of differential and fast scanning calorimetry have been proposed. The complementary investigations give an anhydrous amorphous starch glass transition temperature of 312 +/- 7 degrees C. This estimation correlates with previous extrapolation performed on hydrated starches.

The present paper investigates the heat characteristics of oscillatory piston-driven flow inside thermal-lag type Stirling engine. The geometry consists of a cylinder partially filled with a porous metal structure called regenerator, heated at the lateral wall on one side and cooled on the other side. Brinkman-Forchheimer-Lapwood extended Darcy model is assumed to simulate heat transfer within the regenerator. A numerical model is used to evaluate average entropy generation rate in the regenerator depending on its characteristics (form factor Lr /Dr, porosity and material) and on the oscillatory flow characteristics (working fluid, rotational engine speed, hot end temperature and initial pressure). The output power of the thermal lag Stirling engine is estimated for different working conditions. Results show that, the two main contributors to entropy generation in the regenerator are: entropy due to heat transfer (imperfection loss, internal conduction loss) and entropy due to viscous friction. Regenerator design leading to minimum entropy generation was investigated.

An analytical and CFD method are used to investigate the oscillating flow and friction coefficient in the pulse tube of the Thermal Lag Engine (TLE). The coefficient of friction reciprocating gas flow in the tube and the resulting phase shift angle between the axial velocity of the oscillating flow and gas pressure were obtained using analytical and CFD methods. The efficiency of a pulse tube has been proposed, which can be used to describe the loss of pulse tube quantitatively. The resulting phase angle shift between gas velocity and pressure is obtained analytically with account of friction in oscillating flow in a tube. The velocity profiles and phase angle are in good agreement with the CFD simulation results.

The knowledge of temperature fluctuations is essential for most thermoacoustic systems. In the present paper, cold wire constant-voltage anemometry (CVA) to measure temperature fluctuations is presented. Corrections for the thermal inertia and for the end losses of the wire are applied during the post-processing. The correction for the thermal inertia of the cold wire is achieved by applying a time dependent thermal lag as proposed originally for a constant-current anemometry (CCA) system. This thermal lag is measured in parallel by a hot wire. The thermal end losses of the wires to their supports are also considered and approximate corrections are proposed. The procedure for the cold wire CVA is validated in the acoustic field of an acoustic resonator with wires of different lengths. A comparison between a CVA and a CCA measurement also confirms the CVA measurement. Furthermore, the proposed measurement procedure is applied close to the stack of a thermoacoustic refrigerator. Supposing a two-dimensional flow, the simultaneous measurement of velocity and temperature fluctuations is possible. This allows a detailed examination of the acoustic field close to the stack, including the study of the correlation between temperature and velocity.

In most freeze tolerant insects, the tolerance of the formation of internal body ice is arrived at by a two-step process: (S-1) a period of supercooling of the body fluids that is followed by (S-2) the freezing event. To date, the necessity of S-1 remains to be questioned seriously. The present study reports evidence that S-1 may be almost completely substituted or superseded in large-bodied insects by integumental buffering. In the New Zealand alpine grasshopper Sigaus australis Hutton, there is a substantial difference between external and body core temperatures at the moment when internal ice nucleation is registered. Using the invagination of the pleural suture as a nondetrimental proxy for the core and the sclerotized postnotum as a measure of surface temperature, comparisons of the temperature of crystallization (Tc) show a highly significant difference (P

A quantitative evaluation has been tried on the thermal lags of a fast-scan (≤104 K s−1) microchip differential scanning nanocalorimeter (DSC). A thin layer (∼0.2 μm thick) of a standard material of Tin was vapor deposited on a thin film of polyethylene (PE) sample (∼1–10 μm thick), and the thermal lags have been examined by the dependences on the applied heating rate, film mass, and film thickness of the melting onset temperature of Tin on the bottom and top surfaces of PE films put on the sensor stage of nanocalorimeter. Thermal lags are comprised of the instrumental thermal resistance and the temperature gradient in the film. The instrumental thermal lag was detected by the melting of Tin on the bottom of PE films and well explained by the reported value of the thermal resistance of sensor. The temperature gradient in the film was detected by the melting of Tin on the top surface of PE films, and showed the dependence predicted by the modeling of heat transfer in the thickness direction. The influences of thermal lags have also been examined in terms of the heating rate, β, dependence of the shift in melting peak temperature of PE crystals. The power of βz characterizing the β dependence of the shift became larger with increasing film mass and thickness, i.e. with introducing larger thermal lags. When the power is utilized as a fitting parameter, the influence of thermal lags on the melting point extrapolated to zero heating rate could be kept at small level (±1 °C) even for thick films (∼10 μm). Those behaviors have been validated by numerical calculations based on the modeling of fast-scan microchip DSC.

This study aims to highlight the importance of thermal inertia in buildings. Nowadays, it is possible to use energy analysis software to simulate the building energy performance. Considering Italian standards, these analyses are based on the UNI TS 11300 that defines the procedures for the national implementation of the UNI EN ISO 13790. These standards require an energy analysis under steady-state condition, underestimating the thermal inertia of the building. In order to understand the inertial behavior of walls, a cubic Test-Cell was modelled through the dynamic calculation code TRNSYS and three different wall types were tested. Different stratigraphies, characterized by the same thermal transmittance value, composed by massive elements and insulating layers in different order, were simulated. Through TRNSYS, it was possible to define maximum surface temperatures and to calculate thermal lag between maximum values, both external and internal. Moreover, the attenuation between external surface temperatures and internal ones during summer (July) was calculated. Finally, the comparison between Test-Cell’s annual energy demands, performed by using a commercial code based on the Italian standard UNITS 11300 and the dynamic code, TRNSYS, was carried out.

A ThermoGravimetric analyser with differential scanning calorimetry (TG–DSC) has been studied during the fusion of an indium sample using both an experimental procedure and a CFD simulation. To do so, a CAD model of the real device was built and meshed in detail, in order to take into account the small scale processes which occur inside the crucibles. Several theoretical models, some previously existing in the CFD software used and others developed ad hoc, were applied to simulate the whole facility. Therefore, realistic boundary conditions and a PID-based control system already developed for previous studies had to be used. The validation of the CFD model was done by comparing the outcome of the resulting simulation to the results obtained by experimental procedure in a case where natural convection is the main heat and mass transfer mechanism. This comparison was made for two different heating rates inside the furnace. Typical characteristics of phase change process inside a TG-DSC as thermal lag, onset temperature or heat flow exchange during the fusion could be analysed. As well, a more detailed approach to physical phenomena taking place inside the furnace could be done, since CFD simulations allow to obtain data which is not achievable experimentally. Besides, a valid CFD model for a TG-DSC could be later used in further CFD simulations.

The most commonly used method for studying relaxation processes in polymers is monitoring the enthalpy recovery by measuring differential scanning calorimetry (DSC) heat capacity data. Because of its great influence on heat capacity data, the effect of temperature gradients in the sample on relaxation dynamics study should be investigated. A model for calculating temperature profile in a DSC sample was proposed previously by combining Fourier's law of heat conduction with the Tool–Narayanaswamy–Moynihan (TNM) model. This model was examined using PS samples with different thicknesses. It was found that the temperature gradient influenced optimized values of the kinetic parameters. The thermal history dependence of model parameters is still prominent, however. Here the Scherer–Hodge (SH) equation (based on the Adam–Gibbs model) instead of the TNM equation, is used for describing the relaxation time–structure–temperature relationship in the temperature profile calculation. It is found that the influence of temperature gradients on the thermal history dependence of the Adam–Gibbs (AG) model parameters is greater than that of the TNM model parameters. But the thermal history dependence of the AG model parameters still exists when the thermal lag effect was incorporated.

In this paper, coconut fibre filled precast ferrocement roofing channel components were developed, their thermal behaviour was characterized and its performance was compared to precast ferrocement-only roofing channel components in a real-scale prototype house built at CIIDIR facilities in Oaxaca, Mexico. The experimental analysis performed in this study was based on dynamic climatology. A solar orientation chart of the place was constructed to identify the solar radiation intensity acting on the house. Measurements of roof surface temperatures were conducted to determine temperature damping and temperature wave lag. Monthly average temperature and direct solar radiation data of the site was considered. Coconut fibre filled precast ferrocement roofing performance was compared to a ferrocement-only roofing and to a traditional concrete slab roofing. Results indicate that, coconut fibre filled precast ferrocement roofing channel components experience higher solar radiation intensity but its thermal damping is 40% and its thermal lag of about three and a half hours. Precast ferrocement-only roofing channel showed no thermal lag or damping and traditional concrete slab roofing exhibit a thermal damping of only 13% and its thermal lag of zero. Thus it is concluded that coconut fibre filled precast ferrocement roofing channel components are an ecological alternative for energy saving and thermal comfort.

This study examines the coupled effects of pulsatile blood flow in a thermally significant blood vessel, the effective thermal conductivity of tumor tissue, and the thermal relaxation time in solid tissues on the temperature distributions during thermal treatments. Due to the cyclic nature of blood flow as a result of the heartbeat, the blood pressure gradient along a blood vessel was modeled as a sinusoidal change to imitate a pulsatile blood flow. Considering the enhancement in the thermal conductivity of living tissues due to blood perfusion, the effective tissue thermal conductivity was investigated. Based on the finite propagation speed of heat transfer in solid tissues, a modified wave bio-heat transfer transport equation in cylindrical coordinates was used. The numerical results show that a larger relaxation time results in a higher peak temperature. In the rapid heating case I (i.e., heating power density of 100 W cm− 3 and heating duration of 1 s) and a heartbeat frequency of 1 Hz, the maximum temperatures were 62.587 and 63.107 °C for thermal relaxation times of 0.464 and 6.825 s, respectively. In contrast, the same total heated energy density of 100 J cm− 3 in a slow heating case (i.e., heating power density of 5 W cm− 3 and heating duration of 20 s) revealed maximum temperatures of 57.724 and 61.233 °C for thermal relaxation times of 0.464 and 6.825 s, respectively. In rapid heating cases, the occurrence of the peak temperature exhibits a time lag due to the influence of the thermal relaxation time. In contrast, in slow heating cases, the peak temperature may occur prior to the end of the heating period. Moreover, the frequency of the pulsatile blood flow does not appear to affect the maximum temperature in solid tumor tissues.

The Thermal Lag Engine (TLE) was proposed by Tailer in 1993 and its mechanical simplicity makes it an appealing technology to access renewable sources of energy or recover waste heat. This engine has a single moving part, the piston, which delivers power and acts as the prime mover of the working fluid. The TLE consists of a hot space with a high heat transfer capacity and a cold space with limited heat transfer capabilities. This engine is still not well understood. The paper presents a two control volume model for the TLE. In order to validate the model it is parameterized to describe a TLE built by Organ. The simulations of Organ’s TLE experiments when compared to his experimental results have a correlation coefficient of 0.92 and are significantly correlated within the 95% confidence interval. The different characteristics of Organ’s TLE are discussed based on the simulation results. Conclusions about the required characteristics of the heat transfer regimes and energy fluxes for the TLE are made. It is discussed that the key to a more efficient TLE will result from a careful design of the gas path and the cold heat exchanger, so that more of the enthalpy shuttled into the cold space can be converted into work.

The structure of historic buildings and the materials used in their construction, along with outdoor conditions, affect indoor temperature and humidity. The walls of San Juan Bautista Church at Talamanca de Jarama, Madrid, Spain, exhibit differences in water absorption, whose explanation is to be found in the various types of construction involved in its over seven centuries of building history, the weather conditions and the walls orientation. The south wall fluctuations in inner temperature and humidity produce 11–16 h thermal lag and a very low decrement factor ensuring comfortable interiors all year round with minimal fluctuations in temperature., The present study was funded under projects CGL2011-27902, BIA2009-14395-C04-01, GEOMATERIALES (S2009/MAT-1629), CONSOLIDER-TCP (CSD2007-0058).

This study is aimed to develop a theoretical model to determine criterion of instability and predict performance of a free-piston thermal-lag Stirling engine (FPTLSE). Experiments are conducted to verify the theoretical predictions partly. In the present study, a nonlinear model consisting of non-dimensional equation of motion and energy equation are derived. These governing equations are solved simultaneously by employing a multi-scale method, in which zero-order approximate solutions representing piston motion and temperature variation are obtained. Results show that the FPTLSE can be a self-started engine that may be able to start automatically after heating. In addition, the predictions by the theoretical model are found to agree closely with the experimental data for the oscillation of the piston. The present model is capable of predicting the dynamic behavior of the engine.

The coincident weather data (CWD) means the combination of weather data that affect a moment of indoor heat gains at the same time. It includes the coincidence of dry-bulb temperature, wet-bulb temperature and solar irradiation. The selection of design solar irradiation in the current ASHRAE and CIBSE design handbooks is independent on design dry-bulb and wet-bulb temperature. And the generation methods of CWD in those are based on the original weather data itself. Furthermore, the generation methods in some related literatures are either ignoring the thermal delay and decay of building envelope or not appropriate for engineering using. Hence, a new method based on the hourly heat gain formula, three weather parameters, building heat characteristics and risk factor was developed for the generation of coincident solar irradiance, dry-bulb and wet-bulb temperature. The method was applied to historic weather records of 25 years in Hong Kong and data of 302 kinds of walls to generate coincident design weather data. The result shows that the design dry and wet bulb temperature can be lowered and the solar radiation values are more regular, compared to traditional weather data. In a category of walls, the deviation between the representative parameter and CWD is less than 5%. It’s means that using the new CWD can reduce the building energy consumption, and engineering heat gain calculations can be more precise and concise.

The search for sustainability caused a revival of earth construction. Rammed earth (RE) construction is often preferred as compaction and stabilization leads to stronger, more consistent materials. Tills are glacial sediments. Historically, they were used for construction and brick making. However, their heterogeneous nature has prevented standardisation into mainstream construction. This work contributes to make earth a reliable building material. It evaluates the suitability of till for RE construction by measuring its geotechnical parameters and comparing them against recommended RE values. The results are consistent with other tills and indicate fitness for RE construction. The tills were successfully stabilized with 5% lime, reaching compressive strengths c.1.09 MPa. Thermal performance is vital in construction. High thermal mass materials such as RE can lower today's unsustainable energy demand for heating and cooling. This work experimentally measures the thermal properties of the till and compares them to other constructions. The experimental values are feed into models to compare thermal performance against other REs and concretes. The rammed till has high conductivity (1.65 W/m K) and specific heat capacity (1218.66 J/kg K) indicating a substantial scope to store heat and poor insulation ability. The thermal diffusivity (7.42 × 10 –7 m2/s) suggests that the till will impede heat flow to a greater extent than concrete. In the simulations, the RE assemblies showed the thermal lag typical of high thermal mass materials reducing the fluctuations of external temperature and increasing the internal thermal stability when compared with concrete. All insulated assemblies maintained thermal comfort indexes however, the RE assemblies performed slightly better than concrete; in particular the internally insulated RE, with longer times in superior comfort indices and the smallest temperature drops. The annual heat load of insulated RE is 2–4.2% lower than the concrete construction.