Safe Temperature Research Articles

Experimental study of novel nickel foam-based composite phase change materials for a large-capacity lithium-ion power battery module

Thermal management strategies play an important role in the thermal safety of a power battery. Phase change material (PCM) cooling is considered the most competitive passive heat dissipation mode. In this paper, a novel nickel foam/paraffin (PA)/expanded graphite (EG) composite PCM (CPCM) is proposed for large-capacity prismatic lithium-ion battery modules. First, different proportions of nickel foam-based CPCMs were prepared. Second, the effects of different components of high thermally conductive additive EG on the thermal conductivity, thermal physical properties, thermal stability, and mechanical properties of the composites were studied in depth. Moreover, the fundamental reasons for the aforementioned property changes were analyzed from the microscopic point of view. The results showed that when the content of EG was 4 wt%, the thermal conductivity of the CPCMs approached the peak, which was 1.66 W/(m·K). The peak tensile strength and bending strength of the CPCMs were 2.75 and 6.59 MPa, respectively. The comprehensive analysis showed that adding 4 wt% of EG in the CPCMs was an optimum strategy. Eventually, these compound CPCMs were applied to a large-capacity prismatic lithium-ion power battery module. The experimental results demonstrated that compared with the natural air-cooling module and forced air-cooling module, the peak temperatures (Tmax) of the CPCM cooling module were decreased by 19.52% and 5.79%, and the peak temperature differences (Tmax − Tmin) were decreased by 38.15% and 35.41%, respectively. It is worth noting that even at a 1.5C high-rate uninterrupted charge/discharge cycle repeated five times, the highest temperature is always maintained below the safe temperature (55 °C), and the peak temperature difference is less than 5 °C, showing the dual advantages of the excellent temperature-controlling and temperature-equalizing abilities. The relevant outcomes will provide new ideas and theoretical value for the heat dissipation modes of large-capacity lithium-ion power batteries, ultimately promoting thermal safety performance.

Effect of fin design and continuous cycling on thermal performance of PCM-HP hybrid BTMS for high ambient temperature applications

In the present work, the thermal performance assessment of fins for a Phase Change Material-Heat Pipe (PCM-HP) based hybrid battery thermal management system (BTMS) for maintaining the average temperature of the battery surface below the safe temperature limits during continuous discharge and charge cycles is presented. A 2D computational model is used for fin design selection and to investigate the thermal performance of the PCM-HP hybrid BTMS. Two base designs and twelve fin designs with varying geometry are studied. The optimal design is chosen based on the effectiveness of the fins, the maximum battery temperature, and the PCM melt fraction. With the optimized fin design, the PCM-HP hybrid BTMS reduces the maximum battery surface temperature by 2.95 °C from 62.85 °C to 59.9 °C as compared to PCM-HP BTMS without fin. Using the selected fin the maximum battery surface temperature is maintained below 60 °C with minimum PCM melt fraction at a heat transfer coefficient of 90 W/m2K for three continuous cycles at an ambient temperature of 40 °C. Experiments are performed to verify the thermal performance of the optimized design. Further, it is observed that increasing the latent heat and thermal conductivity enhances the thermal performance of the PCM-HP hybrid BTMS.

A predictive theory on thermal runaway of ultrahigh capacity lithium-ion batteries

Ultrahigh capacity lithium-ion batteries (LIBs) with prudent safety measures are key to future transportation. The undesirable thermal events such as thermal runaway (TR) in LIBs can pose a direct risk to battery life and the consumers. In the present study, a set of new TR criteria are established by closely inspecting the relation between the rate of heat generation and dissipation to anticipate the TR at an early stage. From the proposed criteria, three alarming temperatures prior to TR are identified, such as the safe temperature limit TE (an intersection between heat generation curve and heat removal line), the maximum temperature limit TM (where second derivative of heat generation is zero), and the low temperature TC from the Semenov theory. For a safer battery operation, both the low and upper limit temperatures have to remain below the safety zone, i.e. TM < TE with TC < TE. The criteria are validated by implementing them on the ultrahigh capacity LIBs, which are subjected to the thermal abuse, wherein the rate of heat generation was determined from calorimetry. The state TM < TE indicates the first precursor to TR where a controlled measure can be taken to prevent the runaway. However, TE ≤ TM regarded as the critical state during which a self-sustaining reaction involving delithiated nickel-rich cathode, intercalated anode, and dissociated electrolyte progresses, resulting in an irreversible TR in the system. The validity of the proposed criteria is demonstrated, while additional work is considered in a broad class of batteries subjected to thermal abuse conditions for establishing a safety margin of operation.

Thermal Safety of 1-Ethyl-3-Methylimidazolium Bis(trifluoromethylsulfonyl)imide for Construction-Related Safety Process

The surge in demand for sustainable materials has instigated significant research into versatile substances applicable in fields ranging from everyday commodities to construction and energy. Among these, ionic liquids, notably 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][Tf2N]), have risen to prominence as green solvents. However, an urgent demand exists to comprehend their thermal safety characteristics, particularly for energy applications. Contrary to previous research, which predominantly employed linear fitting or empirical formulas, our study presents a novel non-linear fitting approach to investigate the thermal behavior of [EMIM][Tf2N]. It yields new insights into its activation energy value, marking a significant advance in attaining precise thermal safety data for sustainable construction applications. To ensure safety at elevated temperatures, [EMIM][Tf2N] was selected for comprehensive analysis. Our research evaluated the kinetic model using thermogravimetric analysis coupled with assessing fundamental reaction parameters and simulating thermodynamic equations by identifying hazardous temperatures. This study revealed that the reactivity hazard of [EMIM][Tf2N] escalated considerably when the temperature surpassed 280 °C, emphasizing the importance of process safety. Furthermore, when the temperature exceeded 287 °C, the time to reach the maximum reaction rate (TMR) diminished to less than a day—an aspect crucial to process safety. At temperatures beyond 300 °C, around 70% of the substance was consumed, further underlining the need for stringent safety measures in processing environments. We also considered the impact of different storage containers on thermal safety. The potential runaway temperatures for box-shaped and cylindrical storage containers were established at 270 °C and 280 °C, respectively, providing valuable data for designing safe storage environments. Our research significantly contributes to the prudent utilization and sustainable application of ionic liquids like [EMIM][Tf2N] by considering various safety scenarios and establishing safe temperature ranges.

Food handlers’ lack of knowledge, and misunderstanding of safe food temperatures: An analysis using the theory of social representations

Comprehension is the ability to understand and be familiar with situations and facts. A critical factor causing foodborne diseases is the inadequate temperature during food storage and handling; food handlers often fail to understand this. Therefore, in this study, we investigated how technical language and everyday knowledge operate in the comprehension of safe food temperatures among food handlers in food services. To achieve this, data collection was carried out in two stages. In the first stage, a survey was conducted to 206 food handlers from 14 food service working in the city of São Paulo. Through this survey, we gathered information to characterize the socio-demographic profile of the sample, details about participation in training, and knowledge of technical terms related to safe food temperatures. In the second stage, individuais interviews were conducted on the same day following the questionnaire administration in each food service. A total of 29 interviews were carried out An interview script was developed containing two storylines based on the Fourth Key: “Keep food at safe temperatures,” which is part of the WHO's “Five Keys to Safer Food” manual. Further, the collective subject discourse technique, which is based on the theory of social representations, was employed to analyze each interview and construct a representative collective discourse. Analysis of the results indicated that lack of knowledge about safe food temperatures is mainly a result of the misunderstanding of technical terms. The collective discourses obtained results reinforced that food handlers had diverse and erroneous information about food defrosting, and they exhibited low confidence and clarity about safe food temperatures. Overall, psychological, social, and cultural factors affect the formation of social representations that guide food handlers’ decision-making.

A new multi‐objective optimization of refrigeration cycles (Case study: “Optimization of transcritical carbon dioxide cycle”)

AbstractFor store and maintain products, ingredients, and other perishables at a safe temperature, there is a growing need for low‐temperature refrigeration systems. In this study, a new multi‐objective exergetic criterion is proposed for the optimization of refrigeration cycles, the conventional coefficient of performance (COP) maximization method results in high evaporator temperature, which is in contrast with the philosophy of the invention and design of refrigeration cycles. Thus, it is not a suitable platform for comparing different refrigeration cycles. This research aims to define a practical performance analysis parameter for designing and comparing refrigeration cycles. The novelty of this research is incorporating the impact of evaporator temperature into the COP concept. A performance comparison of the multi‐objective optimization is drawn with that of the maximum COP state on a transcritical carbon dioxide refrigeration cycle. According to the comparison, the evaporator temperature at the optimal state of multi‐objective exergetic optimization was 44 K lower than that of the maximum COP state, which demonstrates the excellent performance of the method. The results of the new multi‐objective exergetic optimization can be used to design low‐temperature evaporation refrigeration cycles. In the end, the flowchart of the suggested performance optimization is presented. Exergy of power at the optimal point of exergetic optimization is about 77% higher than the maximum COP. A comparison of the results obtained from maximum performance coefficient with optimal point of exergetic optimization suggests that the performance coefficient at optimum state of exergetic optimization is about 58% lower than the maximum COP.

Design of novel thermal management system for Li-ion battery module using metal matrix based passive cooling method

Reliable, efficient and safe energy storage is important for electric vehicles and renewable energy storage of power grid. Lithium-ion battery is preferred as energy storage device due to its higher energy density, low self-discharge and longer cycle life. Lithium-ion cells generate heat during high discharge rates and harsh ambient temperature operation, which raises cell temperature and impacts its performance. Therefore, an efficient thermal management system (TMS) is necessary to alleviate thermal issues during charge/discharge process. A combination of phase change material (PCM) with high conductive plate metal matrix is proposed to eliminate the limitation on the heat transfer characteristics of air-cooled systems. To analyze the thermal and electrochemical behavior of a Lithium-ion cell, a detailed CFD simulation with empirical NTGK electro-chemical model is used. The model is first validated with available experimental data and the analysis is then extended to predict thermal response of individual cell of 3s3p module under natural convection boundary conditions. Poor heat transfer capability associated with natural convection at elevated temperature and discharge rate causes the cell maximum temperature (Tmax) and uniformity (ΔT) to be higher than acceptable values of 45 °C and 3 °C respectively. A thermal management system based on passive cooling using PCM is proposed and analyzed using CFD model by first validating the PCM melting behavior under uniform heating. The model is then extended to analyze the impact of PCM on cell temperature rise at different discharge rates of 8 A - 25 A (≈1C - 3.2C) and various operating temperatures of 25°C to 35°C. Low thermal conductivity of PCM limits heat dissipation which leads to higher temperature gradient. A novel TMS based on plate metal matrix structure enclosing PCM is proposed to enhance heat conduction across PCM and increase heat dissipation to maintain battery module under safe operating temperature limits. This approach has brought down the module maximum temperature to 44.1 °C and temperature difference to 1.6 °C during operation at 25 A (3.2C) and 35 °C. Hence, PCM with high latent heat and low thermal conductivity could be used with high conductivity plate metal matrix to improve cell performance by keeping the cell temperature at required range.

Forgone summertime comfort as a function of avoided electricity use

Broadly, energy poverty is defined as insufficient energy access. One often missed sign of energy poverty is an inability to maintain a safe and comfortable indoor temperature. We add to the literature by quantifying the cooling slope gap (i.e., amount of electricity households forgo over the cooling season). We first map a household's electricity consumption across outdoor temperatures using a five-parameter regression model. Next, we identify the household's cooling slope as how much additional electricity they consume per 1 °F increase in outdoor temperature once they start using their air conditioning systems. Using these slopes, we quantify the cooling slope gap in our study region (Arizona). We find that households making less than $15,000 limit their electricity consumption for cooling by 1.03 kWh per 1 °F increase compared to high-income households. For households with the same air conditioning count and efficiency, the cooling slope gap is 0.52 kWh/°F on average, with a maximum of 0.84 kWh/°F. This implies that these households are continuously using coping strategies throughout the cooling season to reduce financial energy poverty but may be putting themselves a heat-illness risk. This finding helps energy poverty mitigation efforts by identifying who is potentially experiencing financial instability or lacks cooling infrastructure.

Peer-to-Peer Human Milk-Sharing Among Israeli Milk Donors: A Mixed-Methods Study in the Land of Milk and Honey.

Evidence is lacking on the phenomenon of peer-to-peer human milk-sharing in the Middle East, specifically, in Israel. This study aimed to uncover peer-to-peer human milk-sharing in Israel, learn about how and whether donors engage in safe milk handling and storage practices, and assess knowledge about human milk and breastfeeding among this milk-sharing population. We also aimed to investigate donors' selectiveness in their decisions about to whom they donate their milk and their perceptions about the sale and purchase of human milk. We conducted a semi-structured online survey, including both closed- and open-ended questions and used mixed methods to analyze responses descriptively. We used non-probability sampling to obtain a broad sample of human milk donors. Out of 250 completed surveys, most participants (87.2%, n = 218) reported engaging in safe milk-sharing practices and were generally knowledgeable about the health risks associated with milk-sharing. Participant religiosity was associated with somewhat lower hygiene practices (r = -0.15, p ≤ .05). Most of the participants (81.7%, n = 190) were against the sale of human milk. Participants generally expressed no preference about the recipient of their milk, with some exceptions. The milk-handling and storage practices of the participants in this study suggest a need to improve knowledge and awareness of safe milk storage temperature and the importance of washing hands before pumping milk, particularly within the religious sector. We propose that guidelines about safe milk-sharing practices be written and adopted by the Israeli Ministry of Health, and communicated through pediatricians, family doctors, nurses in Mother and Child Clinics (In Hebrew: Tipat Halav), and social media.

Design and analysis of cooling jacket developed for vacuum power tubes by multiphase cooling

The vacuum tubes are used extensively in electronic industries. The MW level of vacuum tube are used in RF amplifiers and microwave sources in different sectors like defence, nuclear energy, satellites and medical diagnostics. The first step in the indigenous development of MW level of vacuum tube is the design of its cooling jacket. The cooling jacket of vacuum tubes use hypervapotron (HV) fins which are known for providing efficient cooling in compact space. The key objectives of this paper are to finalize the jacket’s construction material, evaluate the cooling jacket’s heat transfer performance at the MW level of RF (radiofrequency) power, and forecast safe operating conditions for given conditions of high heat flux and water flow rates. In this design, the vacuum tubes’ external dimensions are taken into consideration when designing the cooling jacket. ETP copper (Electrolytic Tough Pitch copper) and copper-chromium-zirconium (CuCrZr) are likely materials for the jacket’s construction. For the aforementioned design of the cooling jacket, FEA (Finite Element Analysis) simulations using a steady-state thermal module and computational fluid dynamics (CFD) simulations using an ANSYS CFX module are described for flow rates of 15, 30, and 60 lpm (liters per minute) and the heat flux 1, 2, 4, and 6 MW m−2. The results of CFD and FEA simulations are found to be in close agreement. A small deviation in results is seen after the start of nucleate boiling. 30 and 60 lpm are desirable flow rates for high heat flux values greater than 2 MW m−2. CuCrZr is the ideal material for a cooling jacket’s construction as it has safe working temperature limit of 350 °C at high heat flux values. Also, 15 lpm flow rate should be avoided while using this cooling jacket at heat flux values greater than or equal to 6 MW m−2.

A hybrid receding horizon optimization and active disturbance rejection control of boiler superheated steam temperature

Efficient control of superheated steam temperature is critical for maintaining the safety and efficiency of a power plant boiler. Exceeding the safe temperature range can cause irreversible damage. However, unknown disturbances and uncertainties, as well as large delay dynamics, often make superheated steam temperature safety control challenging. To this end, this paper proposes a hybrid bi-level safety control for superheated steam temperature control in a power plant boiler. The bottom level uses active disturbance rejection control, while upper level uses receding horizon optimization. The proposed method combines the advantages of active disturbance rejection control in solving unknown disturbances and the dynamic optimization of receding horizon optimization to effectively and safely control superheated steam temperature and optimize the control system performance. The main novelty of the scheme lies in making receding horizon optimization independent of the model of the plant, in terms of making full use of the closed-loop desired dynamics under active disturbance rejection control. Practical synthesis design methods are also presented to illustrate the tuning and optimization of this control strategy. On-site testing results show that the proposed method improves both disturbance rejection and tracking performance, with improvements of at least 20 % over comparison methods. In conclusion, the proposed bi-level control strategy is a promising approach for improving the safety and efficiency of power plants.

Investigation of Cr3+ doped Zn-Co nanoferrites as potential candidate for self-regulated magnetic hyperthermia applications

Controlling the Curie temperature (TC) in the range from 42 °C–46 °C in magnetic hyperthermia (MH) therapy is an essential research topic because overheating can cause irreversible damage to healthy tissue. When TC is in the above temperature range, the magnetic nanoparticles reach a paramagnetic state, effectively turning off the MH treatment. In this work, we synthesized Zn-Co nanoparticles of representative composition Zn0.54Co0.46CrxFe2-xO4, where the Fe3+ cations are carefully replaced by Cr3+ ions, which allow a precise tuning of TC and hence the self-regulation of MH. The x-ray diffraction analysis of the prepared nanoparticles confirms the formation of a single-phase cubic spinel structure. The average crystallite of the nanoparticles increases with Cr3+ doping, while the Tc and saturation magnetization decrease considerably from 78 °C (x = 0.1) to 27 °C (x = 0.6) and 46.6 emu g−1 (x = 0.1) to 15.3 emu g−1 (x = 0.6), respectively. Besides MH potential of the investigated samples as revealed from specific absorption rate (SAR) assays and the maximum temperature reach (Tmax), vary from 7 W g−1 and 37.3 °C, for x = 0.6, to 38 W g−1 and 62.9 °C, for x = 0.1, we found that the composition Zn0.54Co0.46Cr0.4Fe1.6O4 is more promising with SAR of 22 W g−1 and Tmax = 42.3 °C, which is precisely lies in the safe temperature range to automatically activate the self-regulation during the magnetic hyperthermia treatment. The results reveal an excellent combination between size distribution and Cr3+ content in Zn-Co-based ferrite, which has a great potential for self-regulated magnetic hyperthermia applications.

Extremely high heat flux dissipation and hotspots removal with nature-inspired single-phase microchannel heat sink designs

A novel pyramid thermal dissipation unity with conduction–convection coupling thermal dissipation and nature-inspired hotspot removal channel heat sinks is proposed to degrade and dissipate ultra-high heat flux with the order of 103 W cm−2 by using single-phase coolant. A 3D conjugate thermal and flow numerical model is used to validate the feasibility of the proposed ultra-high heat flux dissipation method. The pyramid thermal dissipation unit consists of a spiral tube embedded with etched lotus leaf vein or snowflake-shaped channels. This configuration enables the dissipation of heat fluxes ranging from 1000 to 1500 W cm−2 while maintaining safe operating temperatures for the chip using a single-phase coolant. By utilizing high thermal conductivity materials, the proposed dissipation unit achieves chip working temperatures of 89.89 °C for 1500 W cm−2 and 66.58 °C for 1000 W cm−2. Furthermore, the new design allows for a reduction in the minimum required thermal conductivity for materials to 700 W m−1 K−1 at a pump power of 7.05 W, while still operating within the chip's safe temperature limit of ≤ 120 °C. This expanded range of thermal conductivity values provides more options for selecting suitable materials to fabricate the dissipation unit.

Conceptual Design, Sizing and Thermal Analysis of An Alerting System for Manned Airships

This paper describes an automatic and self-contained electromechanical safety system for manned airships, which alerts the flight crew when the temperature at some point over the envelope exceeds a pre-determined safe limit. The system consists of a thin electrical wire that is looped over the airship envelope along its length, which melts at the location(s) at which the safe temperature is exceeded, and sounds an alarm in the crew cabin. A detailed technical description of the alerting system and all its elements is provided, and a methodology for carrying out sizing of the system, and to carry out thermal analysis is outlined. The methodology is used to size the system for an airship of 30 m envelope length cruising at a speed of 20 m/s at an altitude of 10,000 ft. Results indicate that the mass of the system is a small fraction of the force of buoyancy generated by the airship envelope. Thermal analysis indicates that the alerting system is thermally stable, and despite the fact that current is consistently and continuously flowing in the alarming circuit, the wires are not overheated. The system can be of great help in increasing operational safety levels of a manned airship.

Thermal decomposition mechanism and thermal stability prediction of n-pentane/n-butane mixture

Mixtures appear to hold more promise in organic Rankine cycle (ORC) system than pure working fluids due to their better performance. The key limiting factor for the screening of mixture in the medium- and high temperature ORC system is its thermal stability. ReaxFF reactive molecular dynamic simulations and density functional theory calculations are performed in this study to investigate the thermal decomposition mechanism of n-pentane/n-butane mixture and predict its thermal stability. The results show that the presence of n-butane improves the thermal stability of n-pentane. According to the initial decomposition time, decomposition rates and apparent activation energies of mixture and pure working fluids, n-pentane/n-butane mixture has a better thermal stability than n-pentane and worse than n-butane. Based on the decomposition temperature ranges of n-pentane and n-butane, it can be determined that the n-pentane/n-butane mixture is stable at 280 °C. Therefore, the safe use temperature of the mixture can be roughly predicted based on the thermal stability data of the known working fluids and comparing the thermal decomposition of the mixture with these known working fluids. This paper provides a simple, economical and fast way for the safe use temperature prediction of mixture.

Opportunities to Improve Marine Power Cable Ratings with Ocean Bottom Temperature Models

Determining reliable cable ampacities for marine High Voltage Cables is currently the subject of significant industry and academic reassessment in order to optimize (maximizing load while maintaining safe operating temperatures) design and reduce costs. Ampacity models can be elaborate, and inaccuracies are increasingly predicated on the uncertainty in environmental inputs. A stark example is the role of ambient temperature at cable depth, which, due to the scale of cables and the inaccessibility of the seafloor, is commonly estimated at 15 °C. Oceanographic models incorporating ocean bottom temperature are increasingly available, and they achieve coverage and spatiotemporal resolutions for cable applications without the requirement for project specific measurements. Here, a rudimental validation of the AMM15 and AMM7 mean monthly ocean bottom temperature models for the NW European Shelf indicates encouraging accuracies (MBE ≤ 1.48 °C; RMSE ≤ 2.2 °C). A series of cable case studies are used to demonstrate that cable ratings can change between −4.1% and +7.8% relative to ratings based on a common static (15 °C) ambient temperature value. Consideration of such variations can result in both significant ratings (and hence capital expenditure and operating costs) gains and/or the avoidance of cable overheating. Consequently, validated modelled ocean bottom temperatures are deemed sufficiently accurate, providing incomparable coverage and spatiotemporal resolutions of the whole annual temperature signal, thereby facilitating much more robust ambient temperatures and drastically improving ampacity estimates.

A dumbbell-shaped 3D flat plate pulsating heat pipe module augmented by capillarity gradient for high-power server CPU onsite cooling

With the development of the data center industry and the increasing power density of servers, it is crucial to remove waste heat from small-area heat sources to ensure the safe and efficient operation of data processing chips. To complement existing studies, in this paper, a novel three-dimensional flat plate aluminum pulsating heat pipe (3D-FPPHP) with four different channel structures for radial heat dissipation of high-power server chips was proposed. The results showed that under the favorable influence of the additional capillarity force provided by the variable diameter channels, the FPPHP filled with acetone can start up easily and has good robustness during variable power operation. When the input power was 150 W, the junction temperature of the heating source could be reduced by 42.49 °C (48.67%) compared to an identical aluminum plate. In addition, a heat sink module based on the proposed 3D-FPPHP with optimal charging ratio was tested in a 1U server chassis. The results showed that it can manage an input power of 300 W (corresponding to a heat flux of 41.15 W/cm2) and achieve a total thermal resistance of 0.2053 °C/W under the premise of ensuring a safe junction temperature of chips below 85 °C.

Boosting the thermal management performance of a PCM-based module using novel metallic pin fin geometries: Numerical study

Satellite avionics and electronic components are getting compact and have high power density. Thermal management systems are essential for their optimal operational performance and survival. Thermal management systems keep the electronic components within a safe temperature range. Phase change materials (PCMs) have high thermal capacity, so they are promising for thermal control applications. This work adopted a PCM-integrated thermal control device (TCD) to manage the small satellite subsystems under zero gravity conditions thermally. The TCD's outer dimensions were selected upon a typical small satellite subsystem. The PCM adopted was the organic PCM of RT 35. Pin fins with different geometries were adopted to boost the lower thermal conductivity of the PCM. Six-pin fins geometries were used. First, the conventional geometries were square, circular, and triangular. Second, the novel geometries were cross-shaped, I-shaped, and V-shaped fins. The fins were designed at two-volume fractions of 20% and 50%. The electronic subsystem was assumed to be "ON" for 10 min releasing 20 W of heat, and "OFF" for 80 min. The findings show a remarkable decrease in the TCD's base plate temperature by 5.7 ℃ as the fins' number changed from 15 to 80 for square fins. The results also show that the novel cross-shaped, I-shaped, and V-shaped pin fins could significantly enhance thermal performance. The cross-shaped, I-shaped, and V-shaped reported a decrease in the temperature by about 1.6%, 2.6%, and 6.6%, respectively, relative to the circular fin geometry. V-shaped fins could also increase the PCM melt fraction by 32.3%.

Self-Powered, Non-Toxic, Recyclable Thermogalvanic Hydrogel Sensor for Temperature Monitoring of Edibles.

Thermogalvanic hydrogel, an environmentally friendly power source, enable the conversion of low-grade thermal energy to electrical energy and powers microelectronic devices in a variety of scenarios without the need for additional batteries. Its toxicity, mechanical fragility and low output performance are a hindrance to its wide application. Here, we demonstrate thermoelectric gels with safe non-toxic, recyclable, highly transparent and flexible stretchable properties by introducing gelatin as a polymer network and SO3/42- as a redox electric pair. When the temperature difference is 10 K, the gel-based thermogalvanic cell achieves an open-circuit voltage of about 16.2 mV with a maximum short-circuit current of 39 μA. Furthermore, we extended the application of the Gel-SO3/42- gel to monitor the temperature of hot or cold food, enabling self-powered sensing for food temperature detection. This research provides a novel concept for harvesting low-grade thermal energy and achieving safe and harmless self-driven temperature monitoring.

Experimental assessment of quartz-rich rocks as storage materials for medium and high temperatures air packed bed system

Natural rocks have drawn a lot of interest as sensible storage materials for packed bed system based on their competitiveness in terms of properties, cost and availability compared to other storage materials. Nevertheless, their lifetime depends on the operating temperature range and the used heat transfer fluid. The purpose of this study is to experimentally determine the effects of two temperature ranges: medium range (100 °C–300 °C) and high range (300–600 °C) on the stability of the thermo-physical properties of three quartz-rich rocks namely pegmatite, quartz vein and trondhjemite. For that, firstly, a petrographic description was conducted. Additionally, preliminary stability tests were performed using thermogravimetric and dilatometry analyses to determine the safe operating temperature. Secondly, the durability with air was tested by applying 380 cycles in a laboratory furnace, with a heating/cooling rate of 5 °C/min and 1–2 °C/min respectively, for both temperature ranges. At the end of the durability test, experimental characterizations were conducted on the samples to determine the evolution of their main thermophysical properties such as: density, porosity, water absorption, thermal conductivity and diffusivity and thermal capacity. The obtained results demonstrate the influence of the structural properties on the thermo-mechanical stability of the quartz-rich rocks. We concluded that, large-grained rocks pegmatite and quartz vein are only suitable for medium temperature packed bed systems, while fine-grained trondhjemite rock is well-suited for both ranges.