Reduction In Peak Temperature Research Articles

Eco-friendly flame retardant comprising chitosan-based effectively enhances the flame retardancy of wood with low weight percent gain

Nowadays, there are many types of flame retardants, whether halogenated or halogen-free, that can improve the flame retardancy of wood. However, they continue to pose a significant threat to our environment and cause a substantial increase in the weight gain rates after treatment. It is highly desirable yet challenging to develop an eco-friendly and efficient flame retardant with low weight gain rates. Here, we report a simple and fast process for making eco-friendly flame retardants (chitosan, gelatin, sodium phytate and clay) with weight gain rates of 3.7 %, which form excellent flame retardancy systems. This method can be used to create a 53.5 % reduction in peak heat release rate (pHRR) an 189 % increase in ignition time (cone colorimeter), and a 71.9 % reduction in peak temperature (alcohol spray lamps) compared to raw wood. The results displayed that the effect of flame retardancy (Decreased ratio for pHRR/Weight percent gain) was the best in the past three years. In addition, the flame retardancy mechanism is thoroughly analyzed using the techniques of Raman and so on. This study proposes a novel strategy featured by eco-friendly and simple preparation process for enhancing the flame retardancy of wood in important areas.

Insight into evolution characteristics of pyrolysis products of HLH and HL coal with Py-VUVPI-MS and DFT

To achieve a comprehensive understanding of the influence of chemical structure on the evolution characteristics of coal pyrolysis products, pyrolysis reaction of two kinds of low rank coal (Huolinhe and Huangling coal) were investigated with pyrolysis-vacuum ultraviolet photoionization mass spectrometry (Py-VUVPI-MS). The soft ionized mass spectral detection can provide evolved information of original pyrolysis product. The chemical structure of coal samples was characterized by solid-state 13C-NMR, indicating HLH coal with more branched chain and longer aliphatic chain structure. The bond dissociation enthalpies (BDE) of β-Cal-Cal and β-Cal-O within model compounds were obtained with density functional theory. The difference of peak temperature with maximum evolution was collected to investigate the effect of the chemical environment on evolution behavior of pyrolysis products. The results reveal that branched and long aliphatic side-chains can reduces BDE of β-Cal-Cal and β-Cal-O, resulting in the lower peak temperature of pyrolysis products derived from HLH coal. Substituent groups (such as alkyl and hydroxyl groups) attached on the aromatic rings can reduce peak temperatures. Moreover, the effects of the different substituted position on the aromatic ring of the methyl group presented on differences of the BDE. An increase in aromatic ring size correlates with a certain degree of reduction in BDE for β-Cal-Cal; consequently, peak temperature of pyrolysis products with larger aromatic rings is lower. The pyrolysis behavior of coal were discussed based on the experimental observations and theoretical calculation, which are beneficial to understand the reaction route and mechanism of coal pyrolysis.

Innovative passive cooling of photovoltaic panel using loop heat pipe technology with passive daytime radiative cooling

This paper proposes an innovative cooling technique that utilizes a loop heat pipe (LHP) and passive daytime radiative cooling. The proposed system uses LHP to move the heat load from the photovoltaic (PV) panel surface facing the Sun to a radiator surface where heat is radiated to the sky and dissipated to the surroundings by convection. The LHP allows heat removal from PV panel surface to the radiator surface with negligible temperature difference. Based on selected PV parameters and conditions, the proposed LHP-radiator cooling system achieves a peak temperature reduction of over 10 °C, leading to a 4.6 % enhancement in PV electrical efficiency compared to the reference efficiency. The selected systems’ results show an annual energy saving of 3.4 % (around 8.7 kWh/m2) for the year of 2022.

Temperature overshoot responses to ambitious forestation in an Earth System Model

Despite the increasing relevance of temperature overshoot and the rather ambitious country pledges on Afforestation/Reforestation globally, the mitigation potential and the Earth system responses to large-scale non-idealized Afforestation/Reforestation patterns under a high overshoot scenario remain elusive. Here, we develop an ambitious Afforestation/Reforestation scenario by harnessing 1259 Integrated Assessment Model scenarios, restoration potential maps, and biodiversity constraints, reaching 595 Mha by 2060 and 935 Mha by 2100. We then force the Max Planck Institute’s Earth System Model with this scenario which yields a reduction of peak temperature by 0.08 oC, end-of-century temperature by 0.2 oC, and overshoot duration by 13 years. Afforestation/Reforestation in the range of country pledges globally could thus constitute a useful mitigation tool in overshoot scenarios in addition to fossil fuel emission reductions, but socio-ecological implications need to be scrutinized to avoid severe side effects.

Novel hybrid BTMS by considering safety and driving cycle under extreme fast charge/discharge rates

A battery thermal management system integrating phase change material and mini-channels, with a focus on safety and economic considerations, is proposed to enhance thermal performance across various working conditions, safety scenarios, and realistic driving cycles while minimizing energy consumption. A battery thermal model and PCM simulation model were developed and validated using experimental data. Numerical analyses were conducted to compare the combination of PCM and liquid cooling (hybrid cooling) with fully liquid cooling under different charge/discharge rates and realistic driving cycles, evaluating their safety characteristics, power consumption, and thermal efficiency. The results demonstrated that the hybrid cooling approach can effectively maintain both the maximum temperature and the temperature difference within a desirable range, even when the inlet velocity is reduced from 0.12 to 0.05 m/s compared to liquid cooling. Additionally, the hybrid BTMS provides better working conditions for the battery pack, requiring only 4 × 10−5 W of pumping power compared to 16 × 10−5 W in the liquid cooling system. This underscores the capability of the designed BTMS to cool high-capacity battery packs with significantly lower fluid flow rates. Furthermore, the performance of the proposed cooling system was examined in the event of liquid channel failure, with results showing that the hybrid BTMS can successfully maintain the battery's maximum temperature within an allowable range during fast charge/discharge processes. Lastly, evaluations under realistic driving conditions revealed the superiority of hybrid cooling in reducing peak temperatures and minimizing battery temperature variation.

Experimental analysis of thermal energy efficient clay brick incorporated with phase change material and insulation

In this study, a combination of thermal capacitance (Phase Change Material) and thermal resistance (Polyurethane Foam and air) materials are incorporated into Energy Efficient Clay Brick (EECB) to assess its indoor thermal performance. Various configurations of EECBs were developed, featuring two rectangular slots to accommodate PCM, Polyurethane Foam (PUF), and air in varying orders. These EECBs were then tested in a real outdoor tropical climate over three consecutive days to evaluate the impact of integrating PCM, PUF, and air in indoor thermal performance. The results indicate that the combination of PCM and PUF in EECB-5, with PCM on the outer side and PUF on the inner side, demonstrates the best indoor thermal behavior compared to other configurations. EECB-5 exhibits a maximum reduction in indoor peak temperature of 11.2 % and a time lag ranging from 130 to 140 minutes. EECB-5 shows a decrement factor of 0.54, followed by 0.55 for EECB-2. Additionally, EECB-5 configuration achieves an average surface temperature reduction of 15.01 % compared to Conventional Brick (CB). In addition, the simulation analysis of various configurations of bricks further confirms that the EECB-5 configuration exhibits superior indoor temperature regulation compared to other configurations. It is concluded that PCM enhances the thermal capacitance of building elements by increasing their latent heat storage capacity. Hence, Phase Change Material (PCM) into building elements can help to provide viable solutions for creating energy-efficient building envelopes.

Experimental study of the strategy of C6F12O and water mist intermittent spray to suppress lithium-ion batteries thermal runaway propagation

Extinguished lithium-ion battery fires can experience temperature rebound and re-ignition, necessitating proper fire extinguishing and cooling measures for battery safety. This study introduces a novel approach that integrates C6F12O and water mist as a strategy to prevent the spread of thermal runaway in lithium-ion batteries, evaluating the fire-suppression and cooling ability under various intermittent spray modes. The findings demonstrate that the strategy has a stronger suppression effect compared to continuous water spray and could prevent the spread of thermal runaway. C6F12O can extinguish fires in just 1 s. During the cooling phase, the cooling capacity generally decreases with increasing cycle period and duty cycle. Among different cycle periods, C6F12O combined with intermittent water mist spray (DC = 0.5, Pt = 2 s) exhibited the most effective cooling, significantly reducing peak temperature and providing the highest heat suppression. In terms of duty cycles, C6F12O combined with intermittent water mist spray (DC = 0.1, Pt = 20 s) achieved the longest cooling duration, lowering the temperature of Cell #3 to below 50 °C. The combination of C6F12O and intermittent water mist spray rapidly extinguishes flames, maximizes the cooling impact of water mist, and ultimately hinders the propagation of thermal runaway.

Electric heating curing regimes of temperature self-controlled concrete with nano-carbon black for performance improvement in cold regions

Temperature self-controlled concrete (TSC) demonstrates excellent electric heating performance, providing an effective solution for on-site curing of concrete in cold regions. A suitable electric heating curing (EHC) regime can lead to a desired internal temperature to facilitate the hydration of cement under negative temperature environment and improve the performance of concrete. This study prepared the TSC by adding nano-carbon black into ordinary concrete and investigated the effects of 2 different types of EHC regime, namely constant voltage curing (CVC) and ascending voltage curing (AVC) regimes, on the mechanical properties, electrical properties, temperature evolution, microstructure, and carbon emissions. The results demonstrate that samples cured using traditional methods exhibit the lowest strength. In contrast, the application of EHC shows significant advantages in negative environments compared to traditional curing methods. TSC cured under AVC regimes exhibits a 21.3 % and 33.4 % increase in compressive strength, as well as a 4.4 % and 20.8 % increase in splitting tensile strength at 3 days and 7 days, respectively, compared to TSC cured under CVC regimes. AVC effectively reduces peak temperature and temperature difference, and leads to the peak temperature shifting backward. Additionally, the hydration products of TSC cured under AVC regimes are fewer. However, AVC regimes promote stable microstructural development, favorable resistivity of TSC, and result in a lower carbon footprint during the curing period. The research findings highlight the superiority of AVC regimes in negative temperature environments, potentially addressing challenges in in-situ curing of concrete structures in cold regions and improving efficiency in prefabricated component production.

Miscibility, crystallization and morphology in the novel polylactide/poly(4-hydroxybutyrate) blends

The novel marine degradable poly (4-hydroxybutyrate) (P4HB) synthesized by chemical technique could obviously improve the brittleness of polylactide (PLLA) via physical blending. However, the miscibility, crystallization and morphology in PLLA/P4HB blends are still unexplored. In this article, the PLLA/P4HB blends with different weight ratios were prepared by the solution casting method, followed by the melting crystallization treatment. The PLLA and P4HB were demonstrated to be miscible near the melting temperature of PLLA as revealed by the Flory-Huggins interaction parameter calculating by melting point depression method. Anyway, PLLA and P4HB are supposed to be immiscible at room temperature according to the interfacial tension, fourier transform infrared spectroscopy (FTIR) analysis and scanning electron microscopy (SEM) observation. Both of PLLA and P4HB could form the highly crystalline crystals as casting from solution. The existence of P4HB could significantly induce the cold crystallization of PLLA on the second heating curves characterized by differential scanning calorimetry (DSC), showing of a sharp reduction in peak temperature of about 40 °C lower than that of pristine PLLA. The polarized optical microscopy (POM) and atomic force microscopy (AFM) observation revealed that the P4HB phase could penetrate into the region between fibrous crystals of PLLA spherulites during the isothermal crystallization at 130 °C, and the P4HB fragmented crystals will form after cooling to room temperature, leading to the formation of vertical phase separation in PLLA/P4HB blends associating with the surface tension data. The findings will provide theoretical guidance to understand the miscibility in PLLA based fully biodegradable blends, modulating the morphology and properties of the blends.

Elucidating the influence mechanisms of splat cooling on microstructure evolution in friction stir welding of 2195 Al–Li alloy by multi-scale simulation

Al–Li alloy has been widely used in the manufacture of aerospace aircraft structural parts due to its high specific strength and excellent comprehensive performance. Friction stir welding (FSW), as a solid-state joining technique, generates comparatively lower heat generation in contrast to fusion welding. However, even with this reduced heat input, the welded joints of 2195 Al–Li alloy still exhibit noticeable thermal softening. FSW is very sensitive to welding heat input, and the thermal cycle of high peak temperature coarsens the grain in the weld zone, thereby reducing joint properties. To overcome these problems, external cooling can be applied to reduce peak temperature and increase cooling speed, improving the performance of FSW joints. In order to study the mechanism of external cooling on the microstructure evolution of joints, this work established a multi-scale simulation of splat cooling assisted friction stir welding (SCaFSW) of 2195 Al–Li alloy. The temperature change and material deformation data in SCaFSW were calculated in the macroscopic finite element model and used for further Monte Carlo microstructure evolution simulation, and compared with the conventional FSW process. Results reveal that the splat cooling significantly reduces the area of the high temperature region of the workpiece, decreasing the temperature at the same location 10 mm behind the tool by approximately 50 °C compared to FSW. While the local temperature field around the tool pin is not affected by the splat cooling, which mainly accelerates the cooling rate of the welded joint and reduces the plastic strain. In addition, the dislocation density in the weld nugget zone (WNZ) of SCaFSW joint is higher than that in conventional FSW, which promotes the process of grain nucleation and finally refines the grain in the WNZ. The simulated average grain size and thermal cycling results are in good agreement with the experimental results.

Unlocking energy and economic benefits of integrated green envelopes in office building retrofits

Green envelopes show significant potential in energy conservation and thermal comfort enhancement in office buildings. This study presents a comprehensive method integrating field tests, building energy simulations, and optimization in office buildings in Chongqing, China. A 20-year life-cycle cost analysis was conducted to evaluate the benefits of green roofs (using sedum lineare container-type planting modules) and green façades (featuring vertical kudzu greenery systems). The results indicate that green roofs could reduce peak temperatures by up to 34.3 °C, leading to daily energy savings of 12.5 % during summer. Green façades decreased the wall exterior surface temperatures by up to 3.4 °C and 5.1 °C on the test cold and hot days, respectively. The maximum annual building electricity savings per green-modified area was 22.8 kWh/m2 for the poorly-insulated building and 5.4 kWh/m2 for the well-insulated one. This study highlights the cost-effectiveness of green envelopes in improving building efficiency. The optimal retrofit measure for the poorly-insulated building was the combination of green roofs and daylighting dimming control systems, yielding a 20-year life-cycle net savings per floor area of 81.5 CNY/m2. For the well-insulated building, the daylighting dimming control system alone provided optimal net savings per floor area of 26.4 CNY/m2.

Thermo-fluid analysis on novel design of central impact-inlet double layered micro-channel heat sinks featured with bifurcation verified by experiments

CI-DL-MHCS represents designed central impact-inlet double layered microchannel heat sinks which shows the principal heat transfer feature, and the novel bifurcation is added on upper/lower deck in CI-DL-MHCS, namely CI-DL-MHCS-UB/LB, to explore the further overall thermal advantages numerically and experimentally. The internal located bifurcation parameters including position in CI-DL-MHCS and length have been investigated in the work with the coolant velocities in the range of 0.25–1.05 m/s. The calculated models in simulation is set as symmetric boundary condition, while the assumptions including RNG k-ε turbulence flow and incompressibility dominate in the paper. Bifurcation located lower deck of CI-DL-MHCS has been shown to be effective in controlling the substrate temperature, with a reduction in peak temperature of >18 K compared to referenced CI-DL-MHCS. Numerical simulations clearly demonstrate the enhancement of heat transfer caused by impingement jets and novel located bifurcations with experimental verification. Besides, CI-DL-MHCS with bifurcation have an average Nusselt number enhancement by 4.47% higher compared with CI-DL-MHCS without bifurcation. The bifurcation inevitably occupies the space in CI-DL-MHCS, resulting in a higher pressure drop penalty than the proposed bifurcated structure CI-DL-MHCS, but this can be balanced by an increase in heat transfer considering the overall thermal performance factor. Thus, CI-DL-MHCS featured with bifurcation located in CI-DL-MHCS-LB_3 outperforms significantly in overall thermal performance and thermal uniformity on substrate among all the designed tested models.

A comprehensive analysis of edible and processing quality changes in three whole grain flours induced by dielectric barrier discharge atmospheric cold plasma treatment

SummaryDielectric barrier discharge atmospheric cold plasma (DBD‐ACP) treatment has been used to reduce microbial contamination on the surface of grains, contributing to improved food safety, however, its effect on the edible and processing of whole grain flours is not totally clear. In this study, the effect of DBD‐ACP (5 W, 0–20 min) on the nutritional, physicochemical and structural properties of whole quinoa (WQ), whole highland barley (WHB) and whole triticale (WT) were evaluated. Results showed that the effect of DBD‐ACP treatment on the nutrient composition of different flours differed between grain types. The total polyphenol content of WQ exhibited the most significant changes after 20 min of treatment, decreasing by 62.98%. In addition, DBD‐ACP treatment increased Thr, Phe and Tyr content and accelerated fat oxidation. The results of in vitro simulated digestion experiments indicated that DBD‐ACP treatment significantly reduced (P < 0.05) the final digestibility of three types of whole grain flours. Besides, 20 min of DBD‐ACP treatment significantly changed the physicochemical properties of samples, evidenced by improved hydration and pasting characteristics, increased water absorption index (WAI) and swelling power (SP) and reduced peak temperature (Tp) and gelatinisation enthalpy (∆Hg), especially in WQ20. Further structural analysis showed that DBD‐ACP treatment caused granule cross‐linking and reduced crystallinity of flours. In conclusion, this experiment provided a theoretical basis for the application of DBD‐ACP in grain processing.

Assessment of evaporative porous clay cooler for Building-Integrated photovoltaic systems via energy, exergy, economic and environmental approaches

A thorough study has been conducted for the energy, exergy, economic and environmental analysis to investigate the feasibility of utilizing an evaporative porous structure cooler for the building-integrated photovoltaic (BIPV) system at different building’s sides and directions. Photovoltaic panels within the BIPV systems dissipate their heat to the building’s sides which contribute to rise the interior building’s temperature. In the proposed system, a water-saturated evaporative porous clay cooler is being installed on the back surface of the PV panels to absorb and dissipate their heat by latent evaporation through an evaporation cooling process. A transient numerical heat and mass transfer model based on energy, exergy, economic and environmental approaches was proposed to assist the feasibility of cooling BIPV system via evaporative porous structure cooler. The model was also validated experimentally in the present study. The results exhibited that, comparing with conventional BIPV systems, the presented BIPV/Clay cooling system achieved a peak photovoltaic temperature reduction of 19.1 °C, with a maximum enhancement in the photovoltaic system’s electrical efficiency, electrical power, and exergy efficiency of 9.8 %, 12.6 % and 11.8 %, respectively. The ultimate reduction in the building’s annual thermal load was around 53.8 % when the clay evaporative cooling approach is applied, while the cost of electricity production reduced ultimately by 7.9 %, (from 0.151 $/kWh to 0.134 $/kWh). Further, the payback period decreased by 2.33 years and the annual amount of CO2 emissions decreased by 10.4 % for the utilized BIPV/Clay cooling system compared with the conventional BIPV system.

Selection of suitable cellulose nanofibers derived from eco-friendly sources for the production of lightweight cementitious composites with tuned rheological, mechanical, and microstructure properties

Different cellulose nanofibers (CNF) and ordinary Portland cement (OPC) were combined to prepare CNF-OPC composite pastes at different water to cement ratios (W/C) to optimize density, thermal conductivity, and mechanical strength. The rheological data of CNF-OPC composites showed that the viscosity and yield stress of the mixtures were abruptly increased in comparison to those of OPC pastes at equal W/C. Rheological and morphological data showed that the uniformity of the CNF and degree of fiber entanglement plays a significant role in tuning the composite properties. CNF suspensions with short fibers were observed to improve the mechanical properties of the composite while suspensions with entangled fiber networks were found to decrease density and thermal conductivity. Loss of flexural strength of CNF-OPC compared to OPC was found to be to a lesser extent than loss of compressive strength. The dry density and thermal conductivity of the CNF-OPC composites were substantially reduced to the range of 750 (kg/m3) and 0.1 (W/m−1K−1) at W/C = 2. CNF caused a reduction in peak temperature and postponed the hydration peak by more than 2 h compared to OPC.

Selective chemical doping of carbon nanotube conductors to reduce contact resistance with copper in ultrasonic welds

Electrochemical devices such as batteries, fuel cells, and capacitors employing a carbon nanotube (CNT) electrode can be improved by lowering the contact resistance between CNTs and metallic contacts. The current work investigates two simultaneous strategies to enhance the contact by using chemical doping of CNTs with potassium tetrabromoaurate (KAuBr4) and ultrasonic welding to a metal foil. The specific contact resistivity was measured using the transfer length method (TLM) to evaluate CNT test structures having ultrasonically welded Cu contacts with and without KAuBr4 doping. Purified CNT-Cu samples had a specific contact resistivity of 5.4 mΩ cm2, whereas the KAuBr4 doped CNT-Cu samples were 2.2 mΩ cm2. Confirmation of selective doping to the weld region was made using measured differences in the emissivity of purified and KAuBr4 doped CNTs, which were 0.84 and 0.56, respectively. The lower contact resistance from KAuBr4 doped CNT-Cu ultrasonic welds also reduced the extent of Joule heating beyond the contact region when applying increasing current to failure in a 2-terminal test structure. The benefit of selectively doped CNT-Cu welds was demonstrated across rectangular ribbon and electrode form factors up to an area of 6 cm × 8 cm (typical of electrochemical pouch-cell current collectors). Each form factor showed a 1.5× reduction in peak temperature when selective doping of the CNTs was performed prior to ultrasonic welding of the Cu contact. Thus, the combination of selective doping and ultrasonic welding demonstrates a viable method to fabricate low electrical resistance between CNT electrodes and metallic contacts for electrochemical devices.

Lateral Heterostructure Formed by Highly Thermally Conductive Fluorinated Graphene for Efficient Device Thermal Management.

The continued miniaturization of chips demands highly thermally conductive materials and effective thermal management strategies. Particularly, the high-field transport of the devices built with 2D materials is limited by self-heating. Here a systematic control of heat flow in single-side fluorinated graphene (FG) with varying degrees of fluorination is reported, revealing a superior room-temperature thermal conductivity as high as 128W m-1 K-1. Monolayer graphene/FG lateral heterostructures with seamless junctions are approached for device fabrication. Efficient in-plane heat removal paths from graphene channel to side FG are created, contributing significant reduction of the channel peak temperature and improvement in the current-carrying capability and power density. Molecular dynamics simulations indicate that the interfacial thermal conductance of the heterostructure is facilitated by the high degree of overlap in the phonon vibrational spectra. The findings offer novel design insights for efficient heat dissipation in micro- and nanoelectronic devices.

Enhancing battery cell safety and lifespan through strategic application of insulating and phase change materials utilizing critical thickness for enhanced heat transfer

Efficient and secure operation of electric vehicles relies significantly on the cooling system for lithium iron phosphate (LiFePO4) batteries, a key component in electric vehicle technology. One of the critical challenges faced by electric vehicle is battery cooling to ensure optimal performance, extended battery life, and enhanced safety. The excessive heat generated during battery operation can lead to decrease in performance and potential safety hazards. Conventional cooling systems, such as air or liquid cooling, have limitations in terms of their cooling capacity, weight, and complexity. Therefore, there is a need to explore innovative cooling techniques that can effectively reduce the thermal issues associated with Electric Vehicles LiFePO4 batteries. Employing a thermal insulating coating and phase change material at the critical thickness emerges as an innovative approach to mitigate the surface temperature of battery cells. This is evident during the charging phase, where the bare cell, Teflon-insulated, and paraffin wax-coated cells reached respective peak temperatures of 69 °C, 57 °C, and 53.3 °C. Notably, the Teflon-coated cell exhibited a 17.39% reduction in peak temperature compared to the bare cell, while the paraffin wax-coated cell displayed a more substantial 23.18% reduction. A similar temperature reduction trend is observed during the discharging phase of the battery cell. Utilizing insulating materials or phase change materials with a critical thickness significantly lowers surface temperatures, enhancing the safety of the battery cell and ensuring prolonged life.

Enhancement in air-cooling of lithium-ion battery packs using tapered airflow duct

Temperature uniformity and peak-temperature reduction of lithium-ion battery packs are critical for adequate battery performance, cycle life, and safety. In air-cooled battery packs that use conventional rectangular ducts for airflow, the insufficient cooling of cells near the duct outlet leads to temperature nonuniformity and a rise in peak temperature. This study proposes a simple method of using a converging, tapered airflow duct to attain temperature uniformity and reduce peak temperature in air-cooled lithium-ion battery packs. The conjugate forced convection heat transfer from the battery pack was investigated using computational fluid dynamics, and the computational model was validated using experimental results for a limiting case. The proposed converging taper provided to the airflow duct reduced the peak temperature rise and improved the temperature uniformity of the batteries. For the conventional duct, the boundary layer development and the increase in air temperature downstream resulted in hotspots on cells near the outlet. In contrast, for the proposed tapered duct, the flow velocity increased downstream, resulting in improved heat dissipation from the cells near the outlet. Furthermore, the study investigated the effects of taper angle, inlet velocity, and heat generation rate on the flow and thermal fields. Notably, with the increase in taper angle, owing to the increase in turbulent heat transfer near the exit, the location of peak temperature shifted from the exit region to the central region of the battery pack. The taper-induced improvement in cooling was evident over the entire range of inlet velocities and heat generation rates investigated in the study. The peak temperature rise and maximum temperature difference of the battery pack were reduced by up to 20% and 19%, respectively. The proposed method, being effective and simple, could find its application in the cooling arrangements for battery packs in electric vehicles.

A novel gel dry water: Preparation and application in methane-air explosion

To weaken the adverse effects of methane-air explosions on industrial processes and the environment, the development of highly effective explosion inhibitors is imperative. In this study, a novel ammonium polyphosphate gel dry water (AGDW) powder was synthesized by incorporating superabsorbent polymer (SAP) and ammonium polyphosphate (APP) as additives. The addition of SAP significantly enhanced the physical properties such as stability and water retention of AGDW powder, while APP improved its suppression effects. The suppression effect of AGDW powder on methane-air explosions was investigated in a square explosion pipeline. Experimental results revealed that 4 g AGDW powder with 15 wt% APP completely hindered the propagation of the explosion flame, resulting in a 91.2% reduction in peak temperature and completed elimination of the pressure reflection wave. Increasing the spraying pressure from 0.2 MPa to 0.4 MPa, 2 g AGDW powder with 5 wt% APP was sufficient to suppress the explosion completely. The suppression mechanism of AGDW powder on methane-air explosions was comprehensively elucidated from the cooling effect, diluting effect, and interrupting the chain reaction. This work sheds light on the preparation and application of novel dry water powders and provides a feasible solution for ensuring process safety and controlling gas explosions.