Peak Surface Temperature Research Articles

CFRTP single-lap adhesive bonding and its mechanical performance enhanced by laser surface treatment: Finite element simulation and experimental validation

The outstanding mechanical properties of carbon fiber reinforced thermoplastic polymer (CFRTP) have led to its widespread application in many industrial sectors. In response to the engineering challenge of repairing large non-critical CFRTP structural components in situ, an infrared fiber laser surface cleaning technology is proposed to treat the bonding interface and enhance the tensile strength of polypropylene (PP)-based CFRTP single-lap bonded joints. Specifically, through single-factor and orthogonal experiments, the impact of different process parameters on the properties of the bonded joints was identified first. Then, online temperature monitoring was performed to elucidate the laser treatment mechanism of the CFRTP sample interface. Surface morphology of the laser-treated samples further indicates that when the temperature of the sample surface surpasses the resin decomposition temperature with extended holding time, the resin could be removed from the surface more thoroughly. Additionally, a novel three-dimensional woven finite element (FE) model, accounting for anisotropic heat transfer, was established to predict the surface temperature and cleaning quality of CFRTP. The FE model incorporates the anisotropic heat transfer characteristics of carbon fibers, thus accurately simulating the heat transfer behaviors between carbon fibers and the resin matrix. The laser ablation mechanism is elucidated by examining the surface ablation morphologies and peak surface temperatures. A comparison between experimental results and FE simulations demonstrated a notable coherence in the trend of surface morphology variations, with discrepancies in peak surface temperatures ranging from 3.29 % to 24.63 %. The experimental tests proved that the shear strength of single-lap bonded joints reaches its maximum value when the laser power is 35 W, the scanning speed is 2500 mm/s, and the number of scans is four. The enhancement of the mechanical properties of bonded joints can be attributed to the improved wettability and higher surface free energy of the laser-treated samples.

A long-pulse small edge-localized-mode high-confinement plasma with detachment feedback control by floating potential in an experimental advanced superconducting tokamak in a metal wall environment

Abstract One of the key challenges facing the magnetic fusion research is to demonstrate the compatibility between high confinement and radiative divertor in long-pulse discharges with a metal wall environment. A small edge localized mode (ELM) high confinement plasma is obtained in the upgraded lower divertor of Experimental Advanced Superconducting Tokamak (EAST) with an energy confinement factor H98~1.1 and a Greenwald density fraction fGW ~ 0.65 maintained for 26 s, and periodical detachment is achieved through active control of neon impurity seeding in this long-pulse discharge. For the divertor region, partial detachment is achieved periodically on the outer divertor target plates with the plasma temperature near the outer strike point decreased to below 5 eV and peak surface temperature on the outer divertor target plates maintained below 350C. The peak heat flux of the lower outer divertor decreases significantly and its profile along the target becomes very flat in the detached state. Two low-frequency (<10 kHz) fluctuations that are related to rippling mode caused by a resistive instability appear in the detached state. For the pedestal region, the electron pressure profile is flatter and ELM amplitude is smaller in the detached state than that in the attached state. Edge coherent mode (ECM) appears in the attached state and disappears in the detached state. To achieve this experimentally, a new impurity seeding feedback control scheme is applied, where the floating potential measured by divertor Langmuir probes is used as the feedback sensor, which is more reliable in the long-pulse discharges with high heat fluxes, thus more suitable for application in future devices. This work provides a new approach for the actively controlled radiative divertor as a solution to the divertor heat loads of the future fusion reactors.

Carbon-based phase change composites with directional high thermal conductivity for interface thermal management

Phase change materials (PCMs) can provide a buffer platform for thermal management systems to deal with thermal runaway problems. However, prompt heat dissipation and cost-effective thermal regulation in desired devices are still limited by insufficient thermal transport behavior and liquid leakage of PCMs. Here, we report a facile strategy to develop high-power-density device by carbon-based phase change composites (PCCs) with directional high thermal conductivity. The synergistic effect of self-assembled aligned graphite nanoplatelets (GNPs) inside the resultant PCCs on thermal transport and structural reinforcement enable the PCCs to show high thermal conductivity (in-plane KPCCs of up to 32.86 W m−1 K−1), large heat storage density (158.2–248.3 J g−1), thermal cycling stability, and leakage-proof properties. Furthermore, a PCC-based high-power-density energy device is demonstrated for the tunable thermal regulation by coordinating the orientation of GNPs heat conduction skeleton inside the PCCs with the thermal transport direction of device. The PCC-based module maintains a suitable temperature range of 149–151 °C under various operating conditions and exhibits a decrease of ∼10 °C in the surface peak temperature of power device, showing excellent temperature control performance. Our work holds promising application prospects in the engineering scalable functional PCCs for thermal regulation of electronics and interface thermal management.

Divertor heat load estimates on NSTX and DIII-D using new and open-source 2D inversion analysis code

A thermography inversion algorithm has been developed in the open-source Python-based computer code, HYPERION, to calculate the heat flux incident on plasma-facing components (PFCs) in axisymmetric tokamaks. The chosen mesh size at the surface significantly affects the calculated transient heat flux results. The calculated transient heat flux will exceed the real value when the mesh size tends to zero but will underestimate the real value when the mesh size is large. A criterion for determining the appropriate mesh size for the transient heat flux calculation will be discussed. The numerical scheme for HYPERION uses a 2D fully implicit finite-difference approach, allowing temperature-dependent thermal properties of PFC materials. The inversion algorithm is benchmarked against established heat flux calculation codes, TACO and THEODOR, based on thermography data from NSTX and DIII-D respectively. The primary benefits of HYPERION compared to TACO and THEODOR are that it is open-source and it allows for the optimization of mesh thickness along the substrate. The algorithm also accounts for the thermal properties of thin surface layers that characteristically form on PFCs due to plasma-material interactions. The agreement between HYPERION and THEODOR is excellent, as the percent difference between the codes is ∼5% on average in the case of the DIII-D data for moderate to high heat flux. Verification tests with TACO show slightly higher average percent differences of 8% and 12%. In using HYPERION to study filaments in heat flux, the initial results indicate that small ELMs filaments significantly broaden the divertor heat flux, and decrease divertor peak flux. Compared to the inter-ELM, the small ELM filaments decrease the divertor peak surface temperature. With intermittent divertor filaments, the divertor heat flux width is comparable with that found in L-mode.

The 2019 Marine Heatwave at Ocean Station Papa: A Multi‐Disciplinary Assessment of Ocean Conditions and Impacts on Marine Ecosystems

AbstractIn the past decade, two large marine heatwaves (MHWs) formed in the northeast Pacific near Ocean Station Papa (OSP), one of the oldest oceanic time series stations. Physical, biogeochemical, and biological parameters observed at OSP from 2013 to 2020 are used to assess ocean response and potential impacts on marine life from the 2019 northeast Pacific MHW. The 2019 MHW reached peak surface and subsurface temperature anomalies in the summertime and had both coastal, impacting fisheries, and offshore consequences that could potentially affect multiple trophic levels in the Gulf of Alaska. In the Gulf of Alaska, the 2019 MHW was preceded by calm and stratified upper ocean conditions, which preconditioned the enhanced surface warming in late spring and early summer. The MHW coincided with lower dissolved inorganic carbon and higher pH of surface waters relative to the 2013–2020 period. A spike in the summertime chlorophyll followed by a decrease in surface macronutrients suggests increased productivity in the well‐lit stratified upper ocean during summer 2019. More blue whale calls were recorded at OSP in 2019 compared to the prior year. This study shows how the utility of long‐term, continuous oceanographic data sets and analysis with an interdisciplinary lens is necessary to understand the potential impact of MHWs on marine ecosystems.

New thermal solver for mitigating surface temperature instability in laser-induced heating

An accepted approach to computing laser-induced peak surface temperature is to employ the enthalpy formulation of the transient heat conduction equation [Grigoropoulos et al., Adv. Heat Transfer 28, 75–144 (1996); Sawyer et al., J. Laser Appl. 29, 022212 (2017)]. This approach is generally implemented using an explicit numerical scheme to solve the thermal transport equation. While it offers the advantage of modeling the solid-melt phase transition automatically, the approach results in instability-like behavior in the computed surface temperature. When laser-induced ablation becomes significant, the heating rate in the surface cell becomes unrealistically large. This results in spikes in the computed peak surface temperature due to large errors in calculating the heating rate. In this paper, we present a new approach, which we refer to as the Moving Frame Solver, that employs a moving-coordinate frame of reference, located at the receding evaporating surface. We also use an analytical representation for the phase transition region of the enthalpy-temperature relationship. The Moving Frame Solver combined with an implicit scheme leads to a stable solution without surface temperature, pressure, or velocity spikes. In other words, any instability in these computed parameters due to use of an explicit scheme (such as Dufort–Frankel) has been eliminated. Details of the new thermal solver and example calculations are presented. Numerical experiments suggest that the surface cell size needs to be small, ∼0.1 μm, to obtain a highly accurate solution with a typical metal such as aluminum. Using the Moving Frame Solver with a refined grid near the surface, but coarse elsewhere, enables accurate and stable surface temperature computation.

Experimental study on flexible flame retardant phase change materials for reducing thermal runaway propagation of batteries

The current research on phase change materials (PCM) for Battery Thermal Management Systems (BTMS) often focuses on a single characteristic, either flame retardancy or flexibility. PCM with both flexibility and flame retardancy is relatively uncommon, and studies on flexible PCMs have lacked experimental validation of their effectiveness. This study explored the optimal ratio of aluminium hydroxide (ATH)/ magnesium hydroxide (MTH)/ ammonium polyphosphate (APP), successfully creating a flexible flame-retardant PCM and applying it to battery cooling. The ratio of ATH/MTH/APP was determined as 9: 3:8, providing features such as leak resistance, high thermal conductivity, flame retardancy, and flexibility. Compared to the blank sample without flame retardants, the Peak Heat Release Rate (PHRR) and Total smoke production (TSP) of the PCM decreased by 48 % and 24.3 %, respectively. When applied to BTMS, the PCM restricted the battery's surface peak temperature and maximum temperature difference to 48.76 °C and 4.07 °C, respectively, at a discharge rate of 6C. After applying pressure to leverage flexibility, the temperature difference was further reduced to 1.76 °C, demonstrating the effectiveness of flexibility. In Thermal Runaway (TR) experiments, the PCM delayed the time triggered by TR by 84 s and reduced the maximum temperature by 92.3 °C. This work successfully combines flame retardancy and flexibility, offering valuable insights for the application of flame retardant flexible CPCM in BTMS and other relevant fields.

Experimental Study on Effects of Triggering Modes on Thermal Runaway Characteristics of Lithium-Ion Battery

As an important component of new energy vehicles, the safety of lithium-ion batteries has attracted extensive attention. To reveal the mechanism and characteristics of ternary lithium-ion batteries under different trigger modes, an experimental system was established. The effects of different trigger modes on battery surface temperature, battery internal temperature, injection time, and battery voltage were analyzed. Among them, acupuncture, overheating, and overcharging are used as trigger conditions for mechanical, thermal, and electrical abuse. The results show that the injection time and surface peak temperature are positively correlated with the energy input before thermal runaway. Before the cell triggers abuse, the more input energy, the higher the cell surface temperature, the more serious the thermal runaway, and the higher the damage to the surrounding battery system. Under the same conditions, the intensity and damage degree of overcharge thermal runaway are greater than those of internal short circuit and overtemperature. The abnormal change of voltage suddenly rising and rapidly falling can be used as a condition to judge whether overcharge thermal runaway occurs. Finally, according to the temperature curves at different positions, the thermal diffusion law under different abuse conditions is summarized, which provides a basis for the safety design of the battery module.

Effect of material properties on the laser-induced desorption of hydrogen from tungsten

One of the priority tasks for sustainable operations of future fusion devices is the systematic control of hydrogen isotope content in plasma-facing components. A remote non-damaging analysis of the gas content can be realised by applying laser-induced desorption (LID). LID is based on local heating of the studied surface, followed by the detection of desorbed particles. Interpretation of the LID measurements relies on the definition of effective desorption region from which particles are being released. This region strongly depends on the properties of a laser pulse, an analysed material, and defect centres containing hydrogen isotopes. To investigate the role of these properties on LID, a series of numerical simulation was conducted for the case of hydrogen release from a 10 μm tungsten layer, initiated under nanosecond, microsecond, and millisecond heat loads. The simulations were performed using a common reaction-diffusion model with sequentially varied tungsten thermal conductivity, detrapping energy of hydrogen from traps, concentration of hydrogen traps, and their initial filling ratio. Additionally, the Soret effect was considered in order to estimate its impact on the LID efficiency. Findings reveal that the peak surface temperature reached during heating can characterise the LID efficiency under a particular heat pulse. The LID efficiency dependence on the peak surface temperature weakly varies with material thermal properties, but can alter with the change of trap parameters. The detrapping energy of hydrogen from traps considerably influences the desorption efficiency, while concentration and the initial filling ratio of traps have a moderate effect. The Soret effect is shown to noticeably affect the LID efficiency per a laser pulse only at near-melting temperatures of tungsten. Finally, results demonstrate that the highest desorption efficiency from thick layers can be reached using laser pulses with millisecond duration regardless of surface effects, when the release under short-term pulses can be limited by them.

Temperature Profile Measurement From Radiofrequency Nasal Airway Reshaping Device.

Nasal airway obstruction (NAO) is caused by various disorders including nasal valve collapse (NVC). A bipolar radiofrequency (RF) device (VivAer®, Aerin Medical, Sunnyvale, CA) has been used to treat NAO through RF heat generation to the upper lateral cartilage (ULC). The purpose of this study is to measure temperature elevations in nasal tissue, using infrared (IR) radiometry to map the spatial and temporal evolution of temperature. Experimental and computational. Composite porcine nasal septum was harvested and sectioned (1 mm and 2 mm). The device was used to heat the cartilage in composite porcine septum. An IR camera (FLIR® ExaminIR, Teledyne, Wilsonville, OR) was used to image temperature on the back surface of the specimen. These data were incorporated into a heat transfer finite element model that also calculated tissue damage using Arrhenius rate process. IR temperature imaging showed peak back surface temperatures of 49.57°C and 42.21°C in 1 and 2 mm thick septums respectively. Temperature maps were generated demonstrating the temporal and spatial evolution of temperature. A finite element model generated temperature profiles with respect to time and depth. Rate process models using Arrhenius coefficients showed 30% chondrocyte death at 1 mm depth after 18 s of RF treatment. The use of this device creates a thermal profile that may result in thermal injury to cartilage. Computational modeling suggests chondrocyte death extending as deep as 1.4 mm below the treatment surface. Further studies should be performed to improve dosimetry and optimize the heating process to reduce potential injury. Laryngoscope, 134:1063-1070, 2024.

Cell-level thermal runaway behavior of large-format Li-ion pouch cells

Lithium-ion batteries are widely used in industry for their high energy density and long cycle life; however, they are sensitive to abuse, such as external heating. This study examines 63 Ah, NMC pouch cells at 100% state of charge being forced into thermal runaway (TR) through external side heating at rates ranging from 0.2 to 0.5 °C/s. The fastest heating rate was found to initiate TR earliest, but the peak surface temperatures achieved by all cells were found to be approximately equal. A delay between TR initiation on the heat-exposed surface of the cell and the opposite surface was observed as TR spread across the cell, with the duration found to increase with heating rate. A flaming condition occurred for all cells during TR. For the utilized range of heating rates studied, the radiant heat flux of the flame was found to be unaffected, and the peak chemical heat release rate showed no statistical trend due to the changes in cell heating. Cell mass loss throughout TR also appears to be independent of heating rate with more research required to further explore this parameter. This study provides an in-depth analysis of TR behavior in the context of single, large-format pouch cells, the results of which will be used to develop a future 1D model for cell-level TR that predicts TR propagation behavior in a module.

Post-irradiation examination of the Sirius-1 nuclear thermal propulsion fuel test

Nuclear Thermal Propulsion (NTP) systems hold promise in reducing transit times for exploration of the solar system by both crewed and uncrewed missions. NTP systems currently under investigation include a once-through high-temperature gas-cooled fission reactor to provide thermal energy to heat the coolant, which also serves as the propellant. The fuel system consists of angular UN fuel particles dispersed in a matrix of W/Re, creating a ceramic and metallic composite or cermet, which has been irradiated in Idaho National Laboratory's (INL) Transient Reactor Test Facility (TREAT). This enabled evaluation of these materials under representative nuclear heating rates (∼95 K/s) and peak surface temperatures (∼2527 K). These surface conditions were indicative of achievement of the target peak internal temperature of approximately 2850 K. These tests named Sirius-1 (UN–W/Re), have been irradiated and this paper will present post-irradiation examination results. The Sirius-1 test produced minor, stable cracks in the fuel specimen and spalling of surface material. Volatilized uranium ‘soot’ was found deposited on the inner wall of the irradiation capsule indicating loss of some fissile material from the fuel specimen. Spalling from the surfaces was also noted upon visual inspection. Uranium diffusion from the fuel particles resulted in the formation of U/Re phases and the production of a laminar microstructure on the edge of the fuel system. Overall, the specimen was stable and remained within a coolable geometry upon conclusion of multiple thermal cycles to prototypical operating temperatures.

Molecular Transport Conditions Required for the Formation of Penitentes on Airless, Ice‐Covered Worlds, With Specific Application to Europa, Enceladus, and Callisto

AbstractThe surface morphology of airless, ice‐covered moons of the outer solar system, such as Europa, Enceladus, and Callisto, is not well known at centimeter‐ to meter‐scales. Ice and snow erode differently on such worlds in part because sublimation is the dominant process. On Earth, ice penitentes have been observed in sublimation‐driven environments, and may provide a guide for similar formations on ice‐covered worlds. Penitentes are blade‐like snow features observed on Earth in high‐altitude, low‐latitude snowfields. Models of penitente formation on Earth break down within the free‐molecular regime of airless bodies, leaving a major gap in understanding whether such morphologies can form on their surfaces. To investigate the morphologic evolution of icy bodies, we developed a Sublimation Monte Carlo (SMC) model that enables a numerical approach to modeling exosphere‐surface interactions at free‐molecular conditions. The SMC model uses Monte Carlo tracking of molecules emitted from the surface to determine the net molecular interchange that drives surface changes. We validated results against experiments, matching the evolution of pre‐formed penitentes as they receded in height and became less pronounced. Our results reveal the importance of molecular redeposition on topology, indicating that the stable morphology of isothermal topographies is a planar morphology on regions of net sublimation, regardless of initial surface shape. A study of parametrically varying temperature profiles for sinusoidal penitentes resulted in the following requirement for penitente growth: the trough temperature must exceed the peak temperature by a threshold value, which notably depends on the surface aspect ratio and peak temperature.

Experimental study on nano-encapsulated inorganic phase change material for lithium-ion battery thermal management and thermal runaway suppression

Although widely used in the thermal management of lithium-ion batteries, organic phase change material (PCM) with flammability has been reported to aggravate the fire risk and heat hazards of battery thermal runaway (TR). To reduce the fire risk of PCM during battery TR, an encapsulated inorganic PCM (EIPCM) was synthesized by a nano-encapsulation method of interfacial polymerization in this study. Na2HPO4·12H2O was used as the inorganic core material and silica was adopted as the encapsulated matrix to reduce the inherent defects. The synthesized EIPCM was characterized by a series of tests, demonstrating good phase change properties and thermal stability. The melting temperature of the EIPCM was measured as 51 °C associated with the latent heat of 111.69 kJ/kg. The thermal management effects of EIPCM were further investigated on battery modules at various discharge rates. The results show that EIPCM exhibited good cooling performance, leading to a 23.7% reduction of the peak battery temperature from 86.6 °C to 66.1 °C at a high discharge rate of 3C, and the temperature difference was kept within 3 °C. The TR behavior of batteries with IPCM was further explored, and the results indicate that EIPCM could delay the occurrence of TR by 495 s and decrease the peak surface temperature of the battery by 194 °C. With the nonflammable EIPCM, the fire of TR showed rapid extinction, protecting the batteries from heavier fire hazards. It is also found that EIPCM could inhibit the heat propagation of TR. The prepared EIPCM in this work with good thermal management effects and TR suppression performance has great prospects in practical battery applications, energy storage and other fields.

On the use of natural and forced convection correlations in predictive CFD simulations of liquid pool fires

This paper presents a detailed analysis of predictive numerical simulations of liquid pool fires, i.e., a 1 m – diameter methanol pool, a 0.7 m × 0.8 m ethanol pool, and a 0.18 m – diameter heptane pool. The burning rate is predicted using the ‘film’ model, including empirical correlations for heat and mass transfer. Although the forced convection approach (used in Fire Dynamics Simulator, FDS 6.7.5) yields relatively good results in fuel evaporation rate, it is somewhat questionable from a fundamental standpoint for quiescent burning conditions. Therefore, the natural convection approach is implemented in FDS 6.7.5. The predicted burning rates are similar to the forced convection approach, but the fuel surface temperature is closer to the boiling point by the natural convection approach. Based on the extensive analysis for the methanol pool fire, a modified natural convection correlation is proposed. The latter is tested for the ethanol test with satisfactory results for the peak Heat Release Rate (HRR), burning time, and surface temperature (closer to the boiling point). The modified natural convection approach is further tested for the heptane pool fire. Improved predictions are obtained for the peak burning rate, the transient stage, and the surface temperature.

Experimental and Computational Analyses of Thermal Runaway Behavior of Lithium Ion Pouch Battery at Low Ambient Pressure

Abstract Safety issue concerning “thermal runaway (TR) behavior” of lithium-ion battery (LIB) is one of the core concerns for users. We have studied TR behaviors at various ambient pressures. The thermal runaway onset time (t1) occured in advance at ambient pressure decreasing to 50 kPa from 90 kPa (90, 80, 70, 60, and 50 kPa). At 50 kPa, thermal runaway onset time of LIBs was 177 s earlier than that at 90 kPa. With the decreasing ambient pressure, several values declined, such as battery peak surface temperature, heat release rate (HRR), peak flue gas temperature, and total heat release (THR). Moreover, the peak concentrations of CxHy and CO increased as the ambient pressure decreased, whereas peak concentrations of CO2 and NO showed the opposite trend. Based on the previous studies of the thermal analysis kinetics model of LIBs, a pressure correction factor kp was introduced to establish a prediction model for thermal runaway temperature at low pressure conditions. Based on the model output, the error of thermal runaway onset time t1 could be controlled within ±2 s, and the error of thermal runaway peak temperature Tmax could be controlled within ±2 °C. Our results have been well consistent with the results of simulation, and have been beneficial to further reveal LIBs thermal runaway behavior under low ambient pressure.

Experimental study of bottom reflooding for 5×5 non-uniformly heated rod bundle with spacer grid

Water heat transfer effectiveness during reflooding process in rod bundle geometry is very important for reactor safety under loss of coolant accident. A series of reflooding experiment is carried out at the REFB_NUSOL test facility for a 5 × 5 rod bundle to study the effect of several key parameters on overall reflooding process, including subcooling of coolant (20 °C to 80 °C), coolant flow velocity (2.36 cm/s to 11.19 cm/s), initial peak surface temperature (500 °C–900 °C) and steam temperature on quench front progress. The temperature, heat flux and heat transfer coefficient on the heated rod surfaces have been achieved via a self-developed Reflooding Experimental Data Analysis (REDA) code. Studies on surface temperature variation, quench front progress, heat transfer enhancement caused by spacer grid and effect rules of minimum film boiling temperature are discussed to shed a light on the thermal-hydraulic behaviors during reflooding process in different conditions for rod bundles. Additionally, the prediction accuracy of three published empirical correlations on minimum film boiling temperature are evaluated using our experiment data. The meaning of this work is to explain the reflooding phenomenon of 5 × 5 rod bundle meanwhile provide validation data and suggestions for empirical equation development for nuclear thermal hydraulic analysis code to better predict reflooding process.

Numerical investigation of fire in the cavity of naturally ventilated double skin façade with venetian blinds

Double skin façades (DSFs), offer great views, architectural aesthetics, and energy savings. Yet, in a fire event the glass façade breaks leading to risks to human life and firefighting difficulties. Shading devices incorporated to prevent unfavourable heat gains to reduce cooling load though offer energy savings potentially present other challenges in firefighting and occupants’ evacuation. In this study, Fire Dynamic Simulator (FDS) was used to numerically investigate the spread of a 5 MW HRR polyurethane GM27 fire in a multi-storey double skin façade building with Venetian blinds placed in its cavity. The blinds were positioned 0.4 m away from the internal glazing, middle of the cavity and 0.4 m away from the external glazing respectively. In each blind position the slat angle was opened at 0°, 45°, 90° and 135° respectively. The results show peak inner glazing surface temperature ranged between 283°C to 840°C depending on the thermocouple position, the Venetian blind position and slat opening angle. Without Venetian blinds, peak inner glazing surface temperatures ranged between 468°C to 614°C. In all cases except when the slat angle was 0° and the blind was positioned closer to the outer glazing, the inner glazing surface temperature from the closest thermocouple (TC 14) above the fire room exceeded 600°C, the glass breakage temperature threshold. Overall, the Venetian blind position and slat opening angle influenced the spread of fire. Venetian blind combustibility and flammability were not considered and therefore recommended for future studies. Practical Application: Our manuscript helps to develop new thinking on mitigation of fire risks in buildings for architects, engineers and designers when incorporating Venetian blinds in Double Skin Façades (DSFs).

Analysis of flexural failure mechanism of ultraviolet cured-in-place-pipe materials for buried pipelines rehabilitation based on curing temperature monitoring

Flexural properties is one of the important parameters for the evaluation of buried pipeline ultraviolet cured-in-place pipe (UV-CIPP) rehabilitation effectiveness. The flexure failure mechanism of UV-CIPP materials under the influence of different construction parameters (curing time, UV lamp irradiation intensity, curing distance, and material thickness) is unclear. In this paper, a method was proposed to approximate evaluation of the curing quality by monitoring the surface temperature of UV-CIPP material during the curing process. The flexure failure process and the causes of flexure failure of UV-CIPP materials were analyzed by considering the effects of construction parameters, combined with the monitored material surface peak temperature, and using a three-point bending test incorporating HD video and SEM observations, and sensitivity analysis of construction parameters was carried out by using random forest, and the flexural properties of UV-CIPP materials were predicted by support vector machine. The results showed that matrix cracking, debonding delamination and fiber pull-out fracture are the main reasons for the flexural failure of UV-CIPP materials. Under the influence of a single variable, the exothermic temperature of curing reaction on the surface of UV-CIPP material increases with the increase of curing time, UV lamp power and material thickness within a certain range, and decreases with the increase of curing distance. With the increase of curing time, UV lamp irradiation intensity and curing distance within a certain range, the flexural strength and flexural modulus show a trend of first increase and then decrease, but gradually decrease with the increase of material thickness. The monitoring and analysis results of the curing reaction exothermic temperature show that curing time and UV lamp irradiation intensity are still important factors affecting the curing performance of the material, and the flexural properties of the pipeline UV-CIPP material and the surface curing reaction exothermic temperature satisfy a nonlinear decreasing function relationship, and excessive curing reaction temperatures can reduce the flexural properties of UV-CIPP materials and accelerate its flexural failure.

The effect on thermal comfort and heat transfer in naturally ventilated roofs with PCM in a semi-arid climate: An experimental research

During the past decades buildings have become one of the highest energy demanding component of cities, hence alternatives solutions been sought to reduce their impact. This study presents an experimental evaluation to improve the thermal performance of roofs in semi-arid climate conditions when Phase Change Material (PCM) and natural ventilation are combined. In addition, the results evaluated the thermal comfort under an adaptive model. The performance of two modules (base and PCM) were defined as a function of indoor air temperature, lag time at peak temperature, surface temperature, and heat flux. Four configurations were evaluated: continuous roof components (Cases A) and with an air gap in the roof (Cases B), both with and without natural ventilation. The results, for the configurations with PCM, showed a maximum indoor air temperature reduction between 3.94% and 7.02% and a peak lag time between −10 and 70 min. Likewise, an increase in the solidification time of PCM between 19 and 41% was observed with natural ventilation. The configuration of PCM with 30 cm air gap without natural ventilation obtained the best result, reducing the maximum interior air temperature by up to 2.5°C, 6.85% cooling load reduction, and thermal comfort improved by 50 min.