Differences In Temperature Changes Research Articles

Insights into deformation-induced heating: Temperature-strain prediction in SCM440 steel under deformation scenarios

Recently, deformation-induced temperature was found to be predictable based on corresponding strain, enabling broader applications in temperature prediction and strain measurement. This prediction relies on the temperature-strain relationship during deformation. However, the influence of deformation rate has not been addressed, despite most materials exhibiting rate-dependent behavior that affects both material properties and deformation-induced temperature. This study aims to explore the rate-dependent behavior of the temperature-strain relationship and develop a prediction model. Thermal-strain analysis reveals a linear correlation between deformation-induced temperature and plastic strain, with rate-dependent behavior governed by the deformation rate. Relationships among change in temperature difference per unit strain, heat generation rate, and strain rate are utilized to establish the prediction model. The developed model is primarily applied under various deformation conditions in uniaxial tensile testing. Prediction results for temperature and strain closely match measured values, with an overall difference within 5 % in most cases, except at slow deformation rates where strain estimation is less effective due to dominant heat convection. The model was also applied to three-point bending tests with different artificial-defect specimens, revealing predictable temperature results with a maximum difference of 7 % and estimated strains agreeing with a 5 % error band in the initial 20 % of plastic strain development. Both findings underscore the crucial influence of heat transfer on prediction accuracy, suggesting its necessity in further improvements. This study provides insights into temperature-strain prediction driven by deformation-induced heating, offering guidance for temperature-strain prediction methods and paving the way for applications in thermal-based inspection and temperature-based strain measurement.

Gas leakage physical simulation and its distributed optical fiber sensing experiments in the casing annulus of injection-production pipe column for underground gas storage

Aiming at the problems of high-pressure gas leakage monitoring of injection-production pipe columns in deep underground gas storage under the high-temperature and high-pressure environment, and the problems that distributed optical fiber sensing system is not convenient to carry out detection accuracy and sensitivity testing and verification in actual wellbores, an experimental device for the pipe column gas leakage simulation test of gas storage wellbore is designed and developed to simulate the actual operation conditions of injection-production wellbores. A distributed optical fiber sensing testing environment is built, and the gas leakage signal analysis and location in the casing annulus of injection-production pipe column for the wellbore of underground gas storage are realized by using a distributed temperature sensing (DTS) system and a distributed acoustic sensing (DAS) system. The high-pressure gas leakage signals of the small crack in the damaged area of the wellbore connection can be obtained through the armored optical cable arranged along the casing annulus of pipe columns in the physical device. The optical fiber and its systems can monitor and detect the change of temperature difference and acoustic vibration field in the perimeter caused by high-pressure gas leakage. The spatial-temporal evolution of the casing annulus leakage law and the purpose of pipe column gas leakage can be realized for the wellbore safety monitoring of underground gas storage. The temperature measurement accuracy and positioning sensitivity of the DTS and DAS systems were simulated and verified by designing the pressure difference between inside and outside annular tubes and the leakage source with an interval of 1.0 m. The effectiveness of the pipe column leakage physical simulation experimental device and the reliability of DTS/DAS testing positioning accuracy are verified. This experimental device based on physical model test and its DTS/DAS testing system effectively verify the feasibility and reliability of distributed optical fiber wellbore leakage monitoring for underground gas storage, and its application provides a novel way for the evaluation and analysis of the wellbore tightness and safety of underground energy storage.

Physical activity and temperature changes of Asian elephants (Elephas maximus) participating in eco-tourism activities and elephant polo.

Captive and domestic animals are often required to engage in physical activity initiated or organised by humans, which may impact their body temperature, with consequences for their health and welfare. This is a particular concern for animals such as elephants that face thermoregulatory challenges because of their body size and physiology. Using infrared thermography, we measured changes in skin temperature associated with two types of physical activity in ten female Asian elephants (Elephas maximus) at an eco-tourism lodge in Nepal. Six elephants took part in an activity relatively unfamiliar to the elephants-a polo tournament-and four participated in more familiar ecotourism activities. We recorded skin temperatures for four body regions affected by the activities, as well as an average skin temperature. Temperature change was used as the response variable in the analysis and calculated as the difference in elephant temperature before and after activity. We found no significant differences in temperature change between the elephants in the polo-playing group and those from the non-polo playing group. However, for both groups, when comparing the average skin body temperature and several different body regions, we found significant differences in skin temperature change before and after activity. The ear pinna was the most impacted region and was significantly different to all other body regions. This result highlights the importance of this region in thermoregulation for elephants during physical activity. However, as we found no differences between the average body temperatures of the polo and non-polo playing groups, we suggest that thermoregulatory mechanisms can counteract the effects of both physical activities the elephants engaged in.

The Effect of Intumescent Coating Containing Expandable Graphite onto Spruce Wood

Wood, one of the materials predominantly employed in construction, possesses various advantageous properties alongside certain drawbacks, such as susceptibility to thermal degradation. To enhance wood fire resistance, one approach involves the application of flame retardants. This study compared the fire-retardant effectiveness of expandable graphite, bonded with water glass, as a coating for spruce wood against commercially available fire-retardant treatments. Spruce wood samples (Picea abies (L.) H. Karst) underwent treatment with three distinct retardants: expandable graphite in combination with water glass, Bochemit Antiflash, and Bochemit Pyro. The fire-technical characteristics of the samples were examined by a non-standard test method—a test with a radiant heat source. The experiment evaluated the fire-retardant properties by recording changes in sample mass, burning rate, and temperature difference. The best results among all flame retardants were achieved by expandable graphite in combination with water glass, in all evaluation criteria. Among all the flame retardants used, expandable graphite in combination with water glass achieved the best results in all evaluation criteria.

Effects of photoperiod on the growth and physiological responses in Ulva prolifera under constant and diurnal temperature difference conditions

Photoperiod and temperature are two main factors in the growth of macroalgae, and changes in photoperiod and diurnal temperature difference exist in natural condition. In order to study the effects of photoperiod and diurnal temperature difference on the growth of green algae Ulva prolifera, we cultured this species under three light/dark cycles (light: dark = 10:14, 12:12 and 16:08) with constant (22 °C for light and dark period, noted as 22-22 °C) and diurnal temperature difference (22 °C and 16 °C for light and dark period, respectively, noted as 22-16 °C) conditions. The results showed that: 1) Compared with 10:14 light/dark cycle, the growth of U. prolifera under 12:12 light/dark cycle was significantly enhanced by 39% and 16% for 22-22 °C and 22-16 °C treatments, respectively, while the increase proportion decreased when the daylength increase from 12 h to 16 h. 2) The enhancement in growth induced by diurnal temperature difference was observed under 10:14 light/dark cycle, but not for 12:12 and 16:08 light/dark cycle treatments. 3) The Chl a content and photosynthetic rate increased under short light period and 22-22 °C conditions, while under 22-16 °C conditions, higher photosynthetic rate was observed under 12:12 light/dark cycle and no significant difference in Chl a content was observed. 4) Under 22-22 °C conditions, compared with 10:14 (L:D) treatment, the expression levels of proteins in light-harvesting complexes, PSII and carbon fixation were down regulated, while the photorespiration and pentose phosphate pathway (PPP) were up regulated by 16:08 light dark cycle. Then we speculate that the higher photosynthetic rate may be one compensation mechanism in short photoperiod, and under long light period condition the up regulations of photorespiration and PPP can be in charge of the decrease in enhancement growth induced by longer daylength.

Quantifying Human Contributions to Near‐Surface Temperature Inversions: Insights From COVID‐19 Natural Experiments

AbstractTemperature inversion (TI) constitutes a crucial component in the physicochemical processes of the lower troposphere, but disentangling human contributions to its generation from complex environmental factors poses significant challenges. We leveraged the unique natural experiment prompted by the coronavirus disease 2019 (COVID‐19) pandemic to estimate changes in TI incidence and temperature difference (∆T) caused by the economic shutdown in the first half of 2020 across 500 major cities worldwide. We found that ∆T declined by 2.5% and TI incidence declined by 18.2% compared to 2016–2019, exhibiting spatial‐temporal heterogeneity and pronounced declines in cities with higher levels of economic development and emission reduction. Moreover, we demonstrated that fine particulate matter (PM2.5) may serve as a mediating pathway through which human activities influence air thermal properties, and climate categories modulate this mediating effect. Our analysis provides empirical evidence of human influence on the vertical thermal structure of the atmosphere.

Numerical research on air-based cooling photovoltaic roof

As a new type of building material for plants, photovoltaic roof building materials can be used as roofs of ordinary plants to reduce damage caused by secondary construction to the roofs, and can also absorb and utilize solar radiation to make full use of renewable energy. This article combines photovoltaic modules with air channels to form building material structures with ventilation ducts, establishes physical and mathematical models for photovoltaic roofs in three different inlet modes, and studies the flow and heat transfer characteristics inside air cooling integrated photovoltaic roofs. The simulation results show that the staggered-overlap-joint waterproof double-inlet photovoltaic roof can prevent rain and snow infiltration, and meanwhile, has a cooling effect on the PV panels significantly better than that of the traditional single-inlet air cooling system and the ordinary parallel double-inlet system, and its temperature difference between the inner and outer surfaces of the PV panels is increased by 19.88% compared to the traditional single-inlet air cooling system and by 15.12% compared to the parallel double-inlet system at the maximum. When the included angle between the PV panels of the staggered-overlap-joint waterproof double-inlet photovoltaic roof and the roof is 3°, the change in average temperature difference between the inner and outer surfaces of the PV panels is maximum, which is increased by 3.88% compared with that at 2°. The thickness of the air channel has small influences on the temperature change inside the air channel, the temperature difference between the inner and outer surfaces of the PV panels, and the outlet temperature. When the thickness increases from 50 mm to 200 mm, the change in outlet temperature does not exceed 0.3 K, but the increase in thickness of air layers increases the airflow velocity, which helps to take away more heat.

Can a new cooling method be used in dental implant drilling? An in vitro pilot study

Aims: The aim of this in vitro pilot study was to evaluate the effectiveness of the CryoKB cooling method in increasing the heat-induced temperature during implant drilling in bovine femur bone and to determine its potential usefulness for future in vivo studies. Methods: The study included four groups defined as follows: the G1 group, in which stainless steel materials were cooled using the CryoKB method (n = 13); the G2 group, in which bone was cooled using the CryoKB method (n=13); the K1 group, in which stainless steel materials were cooled using an external irrigation solution (n=13); and the K2 group, in which bone was cooled using an external irrigation solution (n=13). The temperature was measured by creating a 5-mm-deep socket in the bone. The measurements were made every 5 minutes from 0 minutes to 1 hour, using a thermometer device with a type K probe. Results: The temperature changes in 52 samples were evaluated. Statistically significant differences in temperature change were found between the G1 and G2 groups. Statistically significant differences in temperature were found between the G2 and K1 groups and between the G2 and K2 groups. Conclusion: The newly developed cooling method provided more effective and long-lasting cooling than the traditional irrigation method.

Reconstruction of temperature and monsoon precipitation in southwestern China since the last deglaciation

Monsoon precipitation and temperature are the crucial components of the Indian monsoon climate, yet their spatial-temporal relationship remains unclear. In this study, we reconstruct the changes in monsoon precipitation and mean annual temperature simultaneously over the past 16,000 years using multiple proxies, including isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) and n-alkanes, from an alpine lake in southwestern China. On the one hand, the reconstructed monsoon precipitation shows a long-term increasing trend during the last deglaciation and a gradual decrease during the Holocene, with the highest-humidity period occurring in the early Holocene. Our result displays good consistency with the changes in regional mean annual precipitation, summer precipitation, and monsoon intensity during the last deglaciation and the Holocene. On the other hand, the reconstructed mean annual temperature inferred from the n-alkane proxy shows a long-term warm trend since the last deglaciation. Our result is consistent with the regional reconstruction of both mean annual and summer temperatures during the last deglaciation, while evident seasonal differences were observed for Holocene records with a cooling trend of summer temperature and a warm trend of mean annual temperature. Comprehensive comparison reveals that monsoon precipitation in the Indian monsoon region is mainly related to changes in the Intertropical Convergence Zone (ITCZ) and land-sea thermal contrast controlled by boreal summer insolation. In addition, the increase in temperature during deglaciation is primarily attributed to the escalation of greenhouse gases (GHGs), while the divergent trend of seasonal temperature during the Holocene is mainly attributed to the changes in local seasonal insolation. Our research emphasizes that monsoon precipitation is a summer signature in the Indian monsoon region, which is consistent with the changes in summer temperature, while contrasting with the changes in mean annual temperature. Therefore, it is necessary to consider the seasonal difference in temperature changes when investigating the hydrothermal combination in Indian monsoon regions.

Experimental study of the influences of surface roughness and thermal interface material on the performance of a thermoelectric generator

Reducing surface roughness and using thermal interface materials (TIMs) at the interfaces between a thermoelectric generator (TEG), heat source, and heat sink are effective strategies for decreasing the thermal contact resistance (TCR) and enhancing the TEG performance. To evaluate the influences of parameters such as the surface roughness, the thermal conductivity of TIM and loading pressure, we conducted experiments to measure the open-circuit voltage and output power of the TEG under various installation conditions. We also analysed the changes in TCR and temperature difference across the TEG module. The experimental findings were validated with numerical simulations using COMSOL Multiphysics under specific conditions. Our results revealed that reducing surface roughness and using TIM could substantially reduce the TCR, increase the temperature difference across the TEG, and increase the output power from the TEG. In our experiments, we used a temperature controller, cartridge heaters and thermocouples to regulate and record the temperatures of the heat source and heat sink. When maintaining a temperature difference of 53 K between the heat source and heat sink, and loading pressure set at 0.2 MPa, without using TIM, as the surface roughness decreased from 2.2 μm to 0.37 μm and to 0.03 μm, leading to a reduction in the TCR from 0.22 K W−1 to 0.17 K W−1 and to 0.13 K/W. Simultaneously, the open-circuit voltage increased from 1.32 V to 1.65 V and to 1.86 V, and the maximum output power increased from 0.26 W to 0.44 W and to 0.58 W. Additionally, when the surface roughness was 0.37 μm, after using TIM with thermal conductivity of 1 W/m-K, 2 W m−1-K−1, and 5 W m−1-K−1, the open-circuit voltage reached 1.44 V, 1.74 V and 1.94 V, respectively, and the maximum power reached 0.31 W, 0.51 W and 0.65 W, respectively.

Studies on the TEG with changes in temperature difference and material properties

The thermoelectric generators are solid-state devices that produce electricity. They are designed to harness unused energy, or “waste heat”. These devices were primarily utilized in military and space projects due to their reliability as a self-contained power source, requiring minimal maintenance. Additionally, they are environmentally sustainable and renewable sources of energy, emitting no air or noise pollution. According to research, Thermoelectric Generators (TEGs) have a relatively low efficiency rate of less than 5%. However, they hold the potential to effectively harness low-temperature waste heat, making them a promising energy source for the purpose of charging battery cells or super capacitors utilized in autonomous sensors. This study analyses the feasibility of generating electricity through segmented TEGs operating at temperatures below 296 K. Thermoelectric materials were studied to improve the conversion efficiency of the TEG. Furthermore, an investigation was conducted on the configuration of the thermoelectric generator. The COMSOL Metaphysics software is used to design and stimulate the segmented TEG model. This model is initially derived from an existing generator and is known for its accurate outcomes. The study revealed that using an alloy consisting of 75% Bi2Te3, and 25% as a substitute for the thermoelectric material PbSe0.5Te0.5, which led to a significant increase in conversion efficiency and output voltage. A segmented TEG model exhibited higher conversion efficiency. The model is subsequently refined by incorporating various modifications aimed at improving its conversion efficiency.

Mechanism Study of Symmetric Mechanism-Rolling Bearing Dynamic System Considering the Influence of Temperature Factor

Due to the symmetry of their structure and the way they rotate, rolling bearings are often used at high temperatures and high speeds. When the temperature changes, the material properties of the rolling bearing change, which in turn causes the dynamic model equation of the rolling bearing to change. Given the problem in that the conventional dynamic model equation does not consider temperature changes, but because temperature changes cause changes in material performance parameters resulting in differences between the dynamic simulation signals and the actual signals, this paper fully considers three factors, namely, the thermal expansion coefficient, the hardness value, and the friction coefficient. With the influence of temperature changes, a study on the mechanism of the symmetric mechanism-rolling bearing dynamic system considering the influence of temperature factors is proposed. First, combined with the material properties of the rolling bearing, the changes in thermal expansion coefficient, hardness value, and friction coefficient caused by temperature changes were analyzed. Second, the functional relationship expressions obtained above were substituted into the existing conventional dynamic model. Finally, the comprehensive functional relationship formula was substituted into the conventional dynamic model to obtain the rolling bearing dynamic model under temperature difference changes. By studying the mechanism of the symmetric mechanism-rolling bearing dynamic system that considers the influence of temperature factors, this method can undertake a more comprehensive consideration of the dynamic analysis research into rolling bearing fault diagnosis, thereby verifying the effectiveness of the method.

The performance investigation and optimization of reciprocating flow applied for liquid-cooling-based battery thermal management system

Liquid cooling is the most popular battery thermal management system (BTMS) at present, while suffers from high energy consumption and high temperature difference between upstream and downstream. Herein, we first use a reciprocating liquid flow-based BTMS (RLF-BTMS) for cylindrical batteries to release those issues. The comparison among unidirectional flow, cross-direction flow, and reciprocating flow was carried out to investigate the effectiveness of reciprocating flow. After that, the effects of velocity and reciprocating period, two key factors of reciprocating flow, were systematically explored. Finally, a comprehensive criterion of the performance of BTMS considering maximum temperature, temperature difference, temperature distribution coefficient, and energy consumption was proposed to optimize the reciprocating flow. The temperature difference and energy consumption are reduced by 55.3 % and 15.6 % through reciprocating flow. To get energy-saving performance, the reciprocating flow velocity ought to be lower than 0.085 m/s. Since has been greatly reduced, temperature difference changes insensitively with velocity. As decreased from unidirectional flow to 0, the reciprocating periods are divided into three stages: disorder stage, positive stage, and worse stage, according to the thermal characters. Based on the novel BTMS evaluation index, 0.05 m/s and 200 s are selected as the optimal velocity-period combination for the RLF-BTMS. This study recommends applying reciprocating flow to replace the traditional unidirectional flow to get better cooling performance.

Effect of irrigation protocols on bone temperature control during guided implant surgery

Objectives: This experimental laboratory study aimed to compare the effect of four external irrigation protocols on bone tissue heating during guided implant drilling. Methods: Forty perforations were made in ten bovine rib specimens using customized surgical templates. Four experimental groups (n=10/group) were tested: Control group = 10-ml syringe with 25°C saline solution, Group 1 = 10-ml syringe with 10°C saline solution, Group 2 = combined external irrigation using a handpiece and a 10-ml syringe with 25°C saline solution, and Group 3 = combined external irrigation using a handpiece and a 10-ml syringe with 10°C saline solution. The temperature was measured at cervical and apical points using K-type thermocouples, a digital thermometer, and a video recorder. Data were analyzed by ANOVA and Pearson’s correlation coefficients (alpha=0.05). Results: The maximum temperature was 42°C (cervical) and 44°C (apical). No difference in temperature changes was found among groups, but the difference between bone specimens was statistically significant. Temperature and time were positively associated for most groups, mainly in the cervical region. Conclusions: All irrigation methods were equally effective in controlling the bone temperature in cervical and apical regions. However, longer drilling times caused a greater increase in temperature.

The impact of surgical guide design and bone quality on heat generation during pilot implant site preparation: an in vitro study

BackgroundSurgical guides restrict the flow of cooling agent to osteotomy site, which will lead to a temperature rise that provokes tissue injury. Few studies compared differences in the temperature changes between non-limiting ‘conventional’ and limiting ‘guided’ surgical guides during implant site preparation. The objective of this study was to investigate the difference in temperature changes during bone drilling for implant placement using non-limiting and limiting surgical guides at cortical and cancellous bone levels.MethodsForty-four bovine rib samples were used for implant bed preparation in this study with a minimum thickness of 11 mm was chosen for the ribs. The bone was stored in a freezer at 10 °C until it was used. On the day of the study, the bone was defrosted and soaked in water at 21 °C for three hours before embarking on drilling to make sure each sample was at the same temperature when tested. Forty-four bone specimens were prepared and randomly allocated to receive either a limiting or a non-limiting surgical guides (22 for each group). The osteotomy site was prepared by one operator following the manufacturer’s instructions, using limiting and non-limiting surgical guides. Temperature changes were recorded during implant bed preparation using thermocouples that fit into 7 mm-horizontal channels at two different depths (Coronally) and (Apically) at 1 mm distance from the osteotomy site. The data were tested for homogeneity of variances using Levene’s test, then data were analyzed using an Independent sample t-test and the significance level was set at P ≤ 0.05.ResultsThe mean temperature rise for all samples was 0.55 °C. The mean temperature rises for the limiting and non-limiting surgical guides were 0.80 °C and 0.33 °C respectively. There was a statistically significant difference in temperature rise between the limiting and non-limiting surgical guides (P = 0.008). In relation to position of temperature recording (coronal vs. apical), there was no significant difference (P > 0.05). No significant difference was noted between the two groups at cancellous bone level (P = 0.68), but the difference was significant at cortical bone level (P = 0.036).ConclusionLimiting surgical guides showed higher readings than non-limiting. However, for both techniques, temperature rise was not significant clinically and within a safe range.

Designing a professional burnout correction program based on life-purpose orientations in wartime conditions

The work is devoted to substantiation of possibility of reduction of failure rate of thermal mode support system when operating with variable load by control of reliability indicators of thermoelectric cooler. A mathematical model for evaluating the effect of variable thermal load on reliability indicators of a single-cascade thermoelectric cooler at a given temperature level of cooling, medium temperature, geometry of thermocouple branches for various current modes of operation is considered. The relationship between the cooler steady-state operation time and mass and heat capacity of the structure, relative operating current and temperature difference is presented. The results of thermal load relation with operating current, refrigerating factor, time to steady-state mode, energy input, heat dissipation capacity of the radiator, and relative failure rate are presented. Calculations have been made at a given cooling temperature level, medium temperature, temperature differential, and thermocouple branch geometry for various characteristic current operating modes. It is shown that with decreasing thermal load at a given design of thermoelectric cooler, the value of operating current decreases, thus increasing the probability of no-failure operation. The obtained relationship of thermal load with operating current and relative failure rate serves as primary information for design of thermoelectric system for providing thermal modes of thermally loaded elements with variable thermal load. Using the rate of change of temperature difference between the thermally loaded element and the cold electrode of the cooler as a control feature, it is possible to reduce the failure rate when the thermal load decreases, which contributes to increasing the average probability of no-failure operation

Controlling the reliability performance of a thermoelectric cooler under variable heat load

The work is devoted to substantiation of possibility of reduction of failure rate of thermal mode support system when operating with variable load by control of reliability indicators of thermoelectric cooler. A mathematical model for evaluating the effect of variable thermal load on reliability indicators of a single-cascade thermoelectric cooler at a given temperature level of cooling, medium temperature, geometry of thermocouple branches for various current modes of operation is considered. The relationship between the cooler steady-state operation time and mass and heat capacity of the structure, relative operating current and temperature difference is presented. The results of thermal load relation with operating current, refrigerating factor, time to steady-state mode, energy input, heat dissipation capacity of the radiator, and relative failure rate are presented. Calculations have been made at a given cooling temperature level, medium temperature, temperature differential, and thermocouple branch geometry for various characteristic current operating modes. It is shown that with decreasing thermal load at a given design of thermoelectric cooler, the value of operating current decreases, thus increasing the probability of no-failure operation. The obtained relationship of thermal load with operating current and relative failure rate serves as primary information for design of thermoelectric system for providing thermal modes of thermally loaded elements with variable thermal load. Using the rate of change of temperature difference between the thermally loaded element and the cold electrode of the cooler as a control feature, it is possible to reduce the failure rate when the thermal load decreases, which contributes to increasing the average probability of no-failure operation

Experimental Study of Thermally Damaged Concrete under a Hygrothermal Environment by Using a Combined Infrared Thermal Imaging and Ultrasonic Pulse Velocity Method.

This paper proposes a combined inspection method for thermally damaged concrete under a hygrothermal environment. Experiments were conducted to verify the feasibility of the proposed method. Concrete samples with different water-cement ratios (W/C = 0.3, 0.5, 0.7) and moisture contents (dried, 50% saturated, fully saturated) were exposed to elevated temperatures of 200 °C, 400 °C, 600 °C, and 800 °C for 4 h. After cooling to room temperature, infrared thermal imaging (IRT), ultrasonic pulse velocity (UPV) measurements, and mechanical tests were carried out for the damaged concrete samples. The mechanical behavior of thermally damaged concrete with different degrees of water saturation was examined based on mechanical testing. The results show that water can affect the compressive strength and UPV of concrete under certain circumstances, and the residual strength and the heating temperature of the thermally damaged concrete can be evaluated by IRT and UPV measurements. When 50% saturated concrete specimens with a W/C ratio of 0.3, 0.5, and 0.7 are exposed to 200 °C, 12.6%, 27.4%, and 34.6% increases in normalized compressive strength were observed before dropping to approximately 40% at 800 °C. With various moisture contents, the normalized compressive strength variation can be up to 40% at 400 °C in cases with W/C = 0.5 and 0.7. As for UPV, it generally decreases with the increase in moisture content when the peak temperature is 800 °C. On the contrary, whether concrete is saturated or not, there is little difference in temperature change in IRT detection. To obtain a more precise evaluation of concrete structures, IRT can be used to scan a large area to determine the damaged concrete area and areas suspected to be damaged, while UPV could be used to detect concrete members in suspected areas after the completion of IRT scanning.

Micro solid oxide fuel cell thermal dynamics: Incorporation of experimental measurements and model-based estimations for a multidimensional thermal analysis

Transient behaviour of solid oxide fuel cells during various stages of operation, such as warmup, startup, load fluctuations, and shutdown, must be understood and predicted in order to design an efficient controller and prevent degradation/failure of the cell. The difficulty of measuring and monitoring solid oxide fuel cell thermal features necessitates an evaluation of the solid oxide fuel cell thermal dynamics using a hybrid tool that integrates both experimental and numerical methods. In this study, a hybrid measurement tool consisting of a quasi-two-dimensional microscale model and a test rig was used to investigate the solid oxide fuel cell thermal dynamics. Through the hybrid experiment-model approach, steady-state temperature differences across Positive-Electrolyte-Negative and along fuel flow direction were captured. Additionally, the speed of temperature difference change was estimated in two dimensions, which is crucial when estimating transient thermal stresses. Several thermal measures were used to evaluate the thermal dynamics of solid oxide fuel cells. The impact of the operating voltage regime on solid oxide fuel cell thermal dynamics was studied using the varying operating voltage (Voltage Interrupted Measurement) characterisation approach. The outcomes revealed that optimising the performance of solid oxide fuel cells requires a trade-off between thermal management and fuel utilisation due to the exponential effect of fuel utilisation on steady-state temperature differences. The effects of fuel humidity and oxygen content of the oxidant flow on solid oxide fuel cell thermal dynamics were also examined. The results shed light on the new aspects of fuel cell thermal dynamics that are key in designing future smart controllers.

Performance evaluation of solar still integrated with thermoelectric heat pump system

<abstract> <p>This research presents a method for improving a conventional solar still to produce potable water during adverse conditions where there is low or no solar radiation. Summer and winter conditions in the Western Cape province of South Africa were considered. A comparative experimental study was conducted between a conventional solar still and the developed solar still. The developed solar still incorporated a photovoltaic powered thermoelectric heat pump. The purpose of the thermoelectric (TE) heat pump was to accelerate convection inside the developed solar still assembly. The coefficient of performance (COP) of the thermoelectric heat pump installed in the developed solar still ranged from 0.4 to 1.9 at an input current of 5 A. The results indicated that the developed solar still was able to produce 2300 mL per day of drinkable water during a good day in the winter, but the conventional solar still was only able to produce 650 mL per day. The developed solar still produced 2180 mL per day, whereas the ordinary solar still produced 1050 mL per day, during a mild summer day. The developed still had an accumulated water production of 1180 mL during a night with mild temperatures. This significant improvement in yield of the developed solar still system is due to the change in temperature difference between the glazing and the water surface within the developed solar still. This is a significant contribution to the technology of solar water purification.</p> </abstract>