Rate Of Heat Production Research Articles

In-depth characterization of FSP-enhanced aluminum metal matrix: A study in materials modeling and computational techniques

The production of aluminum metal-matrix composites (AMM) involves reinforcing aluminum and its alloys with various powders, with the addition of ceramic reinforcements expected to enhance the mechanical properties, corrosion resistance, and the wear resistance behaviour. However, suboptimal production techniques often result in reduced ductility and toughness when incorporating non-deformable ceramic reinforcements. To address this, friction stir processing (FSP) was employed as a novel surface modification process, using Ti–6Al–4V particles to reinforce 1100 Aluminum Alloy. Microstructures of the composites were analyzed through Scanning Electron Microscopy (SEM), revealing a mean particle size of 2.69 × 103μm for a one-pass FSP at X155 magnification. Notably, the two-pass sample with a particle size of 2.69 × 103μm displayed fewer spherical structures and more irregular structures, indicating a change in the flow mechanism. The three-pass sample exhibited a mean particle size of 1.36 × 103μm, indicating a more uniform distribution and significant size reduction compared to one and two passes.Additionally, a torque-based predicted heat-input analysis indicated that higher temperatures resulting from increased heat production rate and power input led to a decrease in the torque with rising rotational speed. The threaded taper tool generated more heat, potentially facilitating plastic deformation. Finite Element Analysis (FEA) using ABAQUS predicted how this heat affected composite quality, closely aligning with experimental data, with less than a 10 °C difference between processing temperatures in experimental and simulated data. The peak temperature increased as the tool rotated at various tool speeds in line with the projected temperature history of FSP. This study is a significant contribution to enhancing aluminium metal matrix composite through the FSP technology.

Hormonal intrauterine devices and heat exchange during exercise.

Synthetic progestins in oral contraceptives are thought to blunt heat dissipation by reducing skin blood flow and sweating. However, whether progestin-releasing intrauterine devices (IUDs) modulate heat loss during exercise-heat stress is unknown. We used direct calorimetry to measure whole-body total (dry + evaporative) heat loss in young, physically active women (mean (SD); aged 24(4)years, 39.3(5.3) ml/kg/min) with (IUD; n=19) and without (Control; n=17) IUDs in the follicular and luteal phases of the menstrual cycle during light- and moderate-intensity exercise at fixed rates of heat production (∼175 and ∼275W/m2 ) in 30°C, ∼21% relative humidity. Between-group and -phase differences were evaluated using traditional hypothesis testing and statistical equivalence testing within pre-determined bounds (±11W/m2 ; difference required to elicit a ±0.3°C difference in core temperature over 1h) in each exercise bout. Whole-body total heat loss was statistically equivalent between groups within ±11Wm-2 (IUD-Control [90% CIs]; Light: -2 [-8, 5] W/m2 , P=0.007; Moderate: 0 [-6, 6] W/m2 , P=0.002), as were dry and evaporative heat loss (P ≤ 0.023), except for evaporative heat loss during moderate-intensity exercise (equivalence: P=0.063, difference: P=0.647). Whole-body total and evaporative heat loss were not different between phases (P≥0.267), but dry heat loss was 3 [95% CIs: 1, 5] W/m2 greater in the luteal phase (P≤0.022). Despite this, all whole-body heat loss outcomes were equivalent between phases (P≤0.003). These findings expand our understanding of the factors that modulate heat exchange in women and provide valuable mechanistic insight of the role of endogenous and exogenous female sex hormones in thermoregulation. KEY POINTS: Progestin released by hormonal intrauterine devices (IUDs) may negatively impact heat dissipation during exercise by blunting skin blood flow and sweating. However, the influence of IUDs on thermoregulation has not previously been assessed. We used direct calorimetry to show that IUD users and non-users display statistically equivalent whole-body dry and evaporative heat loss, body heat storage and oesophageal temperature during moderate- and high-intensity exercise in a warm, dry environment, indicating that IUDs do not appear to compromise exercise thermoregulation. However, within IUD users and non-users, dry heat loss was increased and body heat storage and oesophageal temperature were reduced in the luteal compared to the follicular phase of the menstrual cycle, though these effects were small and unlikely to be practically meaningful. Together, these findings expand our understanding of the factors that modulate heat exchange in women and have important practical implications for the design of future studies of exercise thermoregulation.

Petrogenesis of high heat producing granites and their contribution to geothermal resource in the Huangshadong geothermal field, South China

The Huangshadong geothermal field (HGF), situated in the contact zone between Mesozoic granites and NE-striking dominant faults in South China, has great geothermal potential. Petrogenesis of reservoir rock plays an important role in understandings its genetic mechanism and assessing geothermal potential. However, due to the lack of rock sample at depth collected from the geothermal reservoir, the petrogenesis of granites in the geothermal reservoirs of the HGF, remains an enigma. This study elucidated the petrogenetic characteristics of these granites sampled directly from geothermal reservoir at the depth of ∼3,000 km and their geothermal implications through zircon U-Pb dating, geochemical analysis, and Hf isotopic analysis. The zircon U-Pb ages indicate that the magmatism evolution of HGF contains three eras, namely, Cretaceous (135 ± 4 to 143.6 ± 2.8 Ma), Jurassic (152.7 ± 2.7 to 176.7 ± 1.8 Ma), and Permian granites (251 ± 9.1 to 251 ± 5 Ma) from the youngest to oldest. The reservoir granites were emplaced during the latest stage of Cretaceous intrusion, as indicated by the zircon U-Pb ages (135 ± 4 Ma and 135.3 ± 2.4 Ma) of rock samples from the deep part of well HR-1. These Cretaceous rocks are highly fractionated I-type granites, featuring high SiO2, K2O, and Na2O contents, high Rb/Sr ratios, low Zr/Hf, Nb/Ta, and Th/U ratios, and A/CNK values of 1.05–1.13. Compared to other Cretaceous granites outcropping on the margin of the HGF, these granites have undergone the strongest fractional differentiation. The Cretaceous granites in the HGF are high-heat-producing rocks (>5 μW/m3), with an average heat production rate of 6.63 μW/m3. Notably, the Cretaceous reservoir granites (as reservoir rocks) serve as an important heat source for the formation of geothermal resources in the HGF. In addition, the zircon Hf isotopic composition indicates that the reservoir Cretaceous granites originated from Meso-to Paleo-Proterozoic lower crustal materials (TDM2: 1,385 to 1907 Ma).

Silurian barrier reef in Lithuania: Reservoir properties and low enthalpy geothermal heat potential

The Silurian barrier reef zone in Lithuania extends for hundreds of kilometres in the narrow zone in Middle Lithuania continuing from the Saukenai reef in the north to the Vilkupiai reef in the south. After prolific Cambrian sandstone reservoirs, they are considered a secondary oil target in Lithuania. However, drilling data showed that the detected reefogenic bodies are either “dry" or saturated with water and/or viscous oil thus practically no valuable oil supply has been obtained. This study illustrates a review of the existing geological and geophysical data, acquired during oil and gas explorations since the 1960s, specifically re-analysed for geothermal purposes.The heat production rates of well doublets within the Silurian reefs range from 0.000044 to 0.24 MWh. Within the area of the Kudirka structure, 6 well doublets could be arranged from the existing 16 exploration wells, at the average distance between the producing-injecting wells of around 700 m. Kudirka has the largest reservoir volume and hence the largest reservoir heat potential (250 GWh). At the smallest distance between the doublet wells of 486 m, the thermal breakthrough would be reached after around 30 years of production-injection. Pavasaris reef shows the best geothermal capacity of a well doublet (0.241 MWh). Reservoir properties are especially good in the partially open fracture zone interval. Pavasaris reef has got 2 wells penetrating the reef, thus one doublet could be arranged within the structure. However, the available thermal energy is limited due to hydrogeological closure and small reservoir size (11.2 × 103 MWh). Other reefs (Saukenai, Vilkupiai, North Bliudziai and a reef in the north of the Vadzgirys reef belt) are small isolated structures, thus their heat potential is low. Moreover, they show low flow rates and hence thermal energy that can be extracted at their wellheads in 30 years is well below 1 × 103 MWh. The study indicates that even though the thickness of the reefal build-ups may reach up to c.90 m, the effective thickness of the reservoirs rarely reaches 20 m. Analysis of the well logs and the core sections show a high heterogeneity of the structures, and hence low recovery factors of the doublets. The distribution of effective layers is usually associated with processes such as stylolitisation and secondary fracturing with enhanced dissolution. For measured low flow rates (<9 m3/h), reusing the existing wells shows low economic viability due to the narrow diameters of the boreholes. Therefore, Silurian reefs show low potential for the application of geothermal energy in Middle Lithuania, although small geothermal projects could be achieved in the Kudirka and Pavasaris sites.

Experimental study on flame spreading over locally wetted thin combustibles

This study proposed a better fire-extinguishing strategy by investigating the effectiveness of wetting operations. It also serves as a first step toward developing physical-based discrete fuel flame spread models using a newly developed small-scale test device. This study examined downward flame spread through a dry narrow path sandwiched by wetted zones formed with thin paper, with different levels of wetting and dried layer width. The dynamic flame behavior and the effect of the presence of adjacent wetting zones were studied both experimentally and numerically. The experimental observations revealed three burning patterns, namely unburned, partially burned, and burned-out regions, depending on various locally wetting fuel arrangements. Additionally, the accelerating flame spread of the wetting case was experimentally reported for the first time. One-dimensional computational simulations suggest that this accelerating phenomenon could be attributed to the chemical reaction triggered by the introduction of water. The reaction rates of OH + CO ↔ H + CO2 and H + O2 + H2O ↔ HO2 + H2O increased due to the water vapor, thereby increasing the heat production rate to further promote the preheating of the downward unburned region and flame spread rate. These findings and conclusions shed more light on the physical and chemical effects of water on flame spreading, highlighting another possibility of water accelerating flame propagation.

Phenotypic flexibility in metabolic adjustments and digestive function in white-shouldered starlings: responses to short-term temperature acclimation.

Changing the intrinsic rate of metabolic heat production is the main adaptive strategy for small birds to cope with different ambient temperatures. In this study, we tested the hypothesis that the small passerine the white-shouldered starling (Sturnus sinensis) can modulate basal metabolism under temperature acclimation by changing the morphological, physiological and biochemical state of its tissues and organs. We measured the effects of temperature on body mass, basal metabolic rate (BMR), wet mass of various internal organs, state 4 respiration (S4R) and cytochrome c oxidase (CCO) activity in the pectoral muscle and organs, metabolites in the pectoral muscle, energy intake, histological dynamics and the activity of duodenal digestive enzymes. Warm acclimation decreased BMR to a greater extent than cold acclimation. At the organ level, birds in the cold-acclimated group had significantly heavier intestines but significantly lighter pectoral muscles. At the cellular level, birds in the cold-acclimated group showed significantly higher S4R in the liver and heart and CCO activity in the liver and kidney at both the mass-specific and whole-organ levels. A metabolomic analysis of the pectoral tissue revealed significantly higher lipid decomposition, amino acid degradation, ATP hydrolysis, and GTP and biotin synthesis in cold-acclimated birds. Acclimation to cold significantly increased the gross energy intake (GEI), feces energy (FE) and digestive energy intake (DEI) but significantly decreased the digestive efficiency of these birds. Furthermore, cold-acclimated birds had a higher maltase activity and longer villi in the duodenum. Taken together, these data show that white-shouldered starlings exhibit high phenotypic flexibility in metabolic adjustments and digestive function under temperature acclimation, consistent with the notion that small birds cope with the energy challenges presented by a cold environment by modulating tissue function in a way that would affect BMR.

Numerical simulation of thermal performance of H2O-EGS and CO2-EGS based on thermal-hydraulic-mechanical coupling method

The use of hydrothermal geothermal methods in Enhanced Geothermal Systems (EGS) presents challenges like reduced thermal storage life and high external energy consumption. Due to its stable heat production time and lower external energy demand, CO2 has the potential to be substituted for H2O. The research zone for this study was chosen to be located in the HDR reservoir in the Gonghe Basin of Qinghai. A three-dimensional discrete fracture model based on a thermal-hydraulic-mechanical coupling method is established, where numerical simulations are conducted using COMSOL software. The discussion focuses on the comparison of heat production effects between H2O-EGS and CO2-EGS in different injection and extraction scenarios are discussed. The results indicate that by lowering the injection temperature and increasing the injection rate, the EGS net heat production rate can be increased, but it also accelerates the heat breakthrough time and shortens the reservoir life. Although CO2-EGS has a lower heat extraction rate in the early stage of thermal recovery than H2O-EGS, it has a longer stable heat production time and a more energy-efficient heat production process. Therefore, compared to H2O-EGS, CO2-EGS has more economic and social benefits.

Study of thermal effects in ammonia-fueled solid oxide fuel cells

Ammonia is regarded as a promising alternative to hydrogen because of its high hydrogen content, ease of transportation and storage, and other favorable properties. However, in ammonia-fueled solid oxide fuel cell (SOFC), the intense heat absorption and excretion of ammonia decomposition and electrochemical reactions can lead to inhomogeneous temperatures inside the cell, which restricts long-life operation. For this reason, a three-dimensional tubular solid oxide fuel cell thermo-electrochemical model is established to explore the thermal characteristics when using ammonia as the fuel. The errors between the power density and voltage obtained from the numerical model and the experimental data in the literature are less than 5 %, which proves the accuracy of the model in this paper. Further parametric simulations reveal that the electrochemical performance and heat production rate are strongly affected by the operating voltage. And a peak power density of 66.4 mW/cm2 is obtained at an operating voltage of 0.45 V. Additionally, increasing the inlet temperature and increasing the fuel flow rate are beneficial for improving cell efficiency, although achieving temperature uniformity remains a challenge. The ammonia pre-reforming degree can be adjusted to effectively improve the temperature distribution uniformity within the cell and improve its internal heat balance. The maximum temperature difference in 96 % pre-reformed SOFC is only 22 K, while it reaches 167 K in direct ammonia SOFC. The temperature and electrochemical performance laws revealed in this study provide a theoretical basis for the optimization of ammonia-fueled SOFC.

Study on the temperature rise characteristics of aging lithium-ion batteries under different cooling methods

Lithium-ion batteries have been widely used in electric vehicles and electrochemical energy storage power stations. With the increase of service time, the single cells in the battery module will age to varying degrees, resulting in inhomogeneous heat generation and even safety accidents. Considering that there is currently limited research on the cooling effect of battery cooling technology on aging batteries, this article adopts a new non-destructive method to study the uneven aging characteristics and the temperature rise characteristics under different cooling conditions of different cells in small aging lithium-ion battery modules. The results show that the irreversible heat generation power of cell 1, cell 2 and cell 3 during 1 C discharge is 1.23 W, 1.33 W and 1.15 W, respectively, showing different degrees of aging. However, the maximum temperature rise under natural heat dissipation conditions has the same change trend and the average temperature rise on the surface of three cells at the end of discharge is about 20 °C. The temperature rise at the edge of cell 2 and cell 1 with more serious aging is higher, while the temperature rise at the center of cell 3 with the smallest aging degree is higher. The temperature distribution at different positions on the surface of the three cells was slightly different. The maximum temperature difference at different positions on the surface of cell 2 (2.3 °C) was greater than that of cell 1 (1.5 °C) and cell 3 (1.6 °C). Then, a simple OCV test method and SEM characterization technique were used to analyze the aging characteristics of the electrode position corresponding to the external temperature monitoring position of cell 2, and the relationship between temperature distribution and aging characteristics was established. The cooling and uniform temperature ability of thermal pad, semiconductor cooling and liquid cooling plate/semiconductor composite cooling are improved in turn. Among them, the liquid cooling plate/semiconductor composite cooling is an efficient temperature control strategy which can make the temperature of cell 3 basically stable at 23 ° C during 1C discharge by reasonably regulating the cooling power, and the maximum surface temperature difference is maintained at 0.4 ° C. It is suggested that when the large cell is put into use, it should be equipped with an independent sub-regional precise temperature control system that can adjust the cooling power in real time according to the heat production rate of the battery, so as to improve the safety and promote the development of sustainable energy.

Thermal runaway behaviour and heat generation optimization of the marine battery cabinet based on module thermal analysis

Currently, the application of lithium-ion batteries in electric vehicles has become common in recent years. Considering the adjustment and transformation of the future energy structure, the use of electric ships is increasing; however, the problem of heat production from the battery cabinet of electric ships must be solved. Therefore, in this study, the multi-scale and multi-domain solution method was used to analyse the heat production and heat transfer of a module-level battery to calibrate the basic calculation model in this study. A double-layer cooling arrangement was proposed to optimise the heat production of the model, which controlled the heat production rate of the battery module to be within 0.00497 K/s. Based on the thermal runaway (TR) module, a three-layer marine battery cabinet was visually analysed for the first time, and the influence of TR on the upper and lower layers and the thermal spread behaviour of the battery pack in the middle layer were studied. The results indicated that the temperature change in the battery in the first layer was more significant than that in the third layer. Furthermore, the proposed double-layer cooling scheme controlled the temperature of the battery in direct contact with the heat source to within 324.4 K. The findings of this study provide insights into the TR behaviour of a marine battery cabinet and its influence on heat generation as well as guidance for the thermal management of electric marine battery cabinets.

Influence of Biological Sex and Fitness on Core Temperature Change and Sweating in Children Exercising in Warm Conditions.

This study aimed to investigate the associations of biological sex and aerobic fitness (i.e., V̇O 2peak ) on the change in gastrointestinal temperature (∆ Tgi ) and whole-body sweat rate (WBSR) of children exercising in warm conditions. Thirty-eight children (17 boys, mean ± SD = 13.7 ± 1.2 yr; 21 girls, 13.6 ± 1.8 yr) walked for 45 min at a fixed rate of metabolic heat production (8 W·kg -1 ) in 30°C and 40% relative humidity. Biological sex and relative V̇O 2peak were entered as predictors into a Bayesian hierarchical generalized additive model for Tgi . For a subsample of 13 girls with measured body composition, body fat percent was entered into a separate hierarchical generalized additive model for Tgi . Sex, V̇O 2peak , and the evaporative requirement for heat balance ( Ereq ) were entered into a Bayesian hierarchical linear regression for WBSR. The mean ∆ Tgi for boys was 0.71°C (90% credible interval = 0.60-0.82) and for girls 0.78°C (0.68-0.88). A predicted 20 mL·kg -1 ·min -1 higher V̇O 2peak resulted in a 0.19°C (-0.03 to 0.43) and 0.24°C (0.07-0.40) lower ∆ Tgi in boys and girls, respectively. A predicted ~13% lower body fat in the subsample of girls resulted in a 0.15°C (-0.12 to 0.45) lower ∆ Tgi . When Ereq was standardized to the grand mean, the difference in WBSR between boys and girls was -0.00 L·h -1 (-0.06 to 0.06), and a 20-mL·kg -1 ·min -1 higher predicted V̇O 2peak resulted in a mean difference in WBSR of -0.07 L·h -1 (-0.15 to 0.00). Biological sex did not independently influence ∆ Tgi and WBSR in children. However, a higher predicted V̇O 2peak resulted in a lower ∆ Tgi of children, which was not associated with a greater WBSR, but may be related to differences in body fat percent between high and low fitness individuals.

Biophysical, thermo-physiological and perceptual determinants of cool-seeking behaviour during exercise in younger and older women.

Women continue to be under-represented in thermoregulatory research despite their undergoing unique physiological changes across the lifespan. This study investigated the biophysical, thermo-physiological, and perceptual determinants of cool-seeking behaviour during exercise in younger and older women. Eleven younger (25±5years; 1.7±0.1m; 63.1±5.2kg) and 11 older women (53±6years; 1.7±0.1m; 65.4±13.9kg) performed a 40-min incremental cycling test in a thermoneutral environment (22±1.7°C; 36±4% relative humidity). Throughout the test, participants freely adjusted the temperature of a cooling probe applied to their wrists to offset their thermal discomfort. We continuously recorded the probe-wrist interface temperature to quantify participants' cool-seeking behaviour. We also measured changes in participants' rate of metabolic heat production, core and mean skin temperatures, and skin wetness. Finally, we body-mapped participants' skin heat, cold and wetness sensitivity. Our results indicated that: (1) older and younger women exhibited similar onset and magnitude of cool-seeking behaviour, despite older women presented reduced autonomic heat-dissipation responses (i.e., whole-body sweat losses); (2) older women's thermal behaviour was less determined by changes in core temperature (this being a key driver in younger women), and more by changes in multiple thermo-physiological and biophysical parameters (i.e., physical skin wetness, temperature and heat production); (3) older women did not present lower regional skin thermal and wetness sensitivity than younger women. We conclude that predictions of female cool-seeking behaviours based on thermo-physiological variables should consider the effects of ageing. These findings are relevant for the design of wearable cooling systems and sports garments that meet the thermal needs of women across the lifespan.

Contributions of 238U, 232Th, and 40K to the radiogenic heat production in selected river sediment samples of South Africa

In this study, 16 sediment samples were collected from Bree, Klein-Brak, Bakens and uMngeni rivers of South Africa and were prepared, analysed and evaluated for the activity concentration of 238U, 232Th and 40K concerning its radiogenic heat production using a high-purity germanium detector. The results show that 238U is the prevalent radionuclide in radiogenic heat production, with 232Th and 40K emerging as trace elements. The mean activity concentrations are 28.97%, 63.69% and 7.34% for uranium, thorium and potassium, respectively, from all sampling locations. This shows that a high radioactive concentration of a specific radionuclide does not necessarily imply its increased contribution to radiogenic heat production. The radionuclide contributions to radiogenic heat production at all sampled locations are 59.39%, 35.11% and 5.50% for uranium, thorium and potassium, respectively. The mean radiogenic heat production rate in the study area ranged from 0.0180 μW m − 3 in sediment samples from the Bree River in Western Cape to 0.0072 μW m − 3 in sediment samples of uMgeni River in KwaZulu-Natal. All values obtained for this study are five times lower than the average continental radiogenic heat production of 1 μW m − 3 . This study provides insight into the radiogenic heat production rate due to the presence of radionuclides in all river samples.

Moisture content effects on self-heating in stored biomass: An experimental study

Biomass is essential for modern bioenergy applications, but long-term storage of large volumes of it can pose challenges to plant safety due to the intrinsic self-heating characteristics of biomass piles. In recent years, serious fire accidents have occurred because of self-heating. However, little research has been conducted on this concern. The effects of different initial moisture contents (range of 20–95 %) on the self-heating characteristics of rice and wheat straw, which are two different agricultural biomass residues, are investigated in this study. Biomass samples with different initial moisture contents are stored in a well-insulated container, and the temperature and oxygen levels within the stored biomass samples are monitored. Based on the tests, the heat production rate, oxygen consumption rate and microorganism growth rate are derived, and the impacts of the initial moisture contents on the self-heating characteristics of the stored biomass samples are analysed. The highest temperatures in the stored rice straw and wheat straw are attained under initial moisture contents of 50 % and 20 %, respectively, while the largest heat production rates for both straw types are attained under an initial moisture content of 95 %. An increase in the initial moisture content greatly enhances the overall biological reactivity and oxygen consumption rate. The heat production and oxygen consumption levels exhibit a clear positive correlation. Under identical storage conditions, wheat straw is more susceptible to self-heating than rice straw, as shown by its higher heat generation, faster oxygen consumption, and shorter temperature peaking time. This study contributes to a quantitative understanding of the underlying processes and provides valuable experimental data for model development to guide safe biomass storage systems.

Simulating Muscle-Level Energetic Cost Savings When Humans Run with a Passive Assistive Device.

Connecting the legs with a spring attached to the shoelaces, called an exotendon, can reduce the energetic cost of running, but how the exotendon reduces the energetic burden of individual muscles remains unknown. We generated muscle-driven simulations of seven individuals running with and without the exotendon to discern whether savings occurred during the stance phase or the swing phase, and to identify which muscles contributed to energy savings. We computed differences in muscle-level energy consumption, muscle activations, and changes in muscle-fiber velocity and force between running with and without the exotendon. The seven of nine participants who reduced energy cost when running with the exotendon reduced their measured energy expenditure rate by 0.9 W/kg (8.3%). Simulations predicted a 1.4 W/kg (12.0%) reduction in the average rate of energy expenditure and correctly identified that the exotendon reduced rates of energy expenditure for all seven individuals. Simulations showed most of the savings occurred during stance (1.5 W/kg), though the rate of energy expenditure was also reduced during swing (0.3 W/kg). The energetic savings were distributed across the quadriceps, hip flexor, hip abductor, hamstring, hip adductor, and hip extensor muscle groups, whereas no changes were observed in the plantarflexor or dorsiflexor muscles. Energetic savings were facilitated by reductions in the rate of mechanical work performed by muscles and their estimated rate of heat production. By modeling muscle-level energetics, this simulation framework accurately captured measured changes in whole-body energetics when using an assistive device. This is a useful first step towards using simulation to accelerate device design by predicting how humans will interact with assistive devices that have yet to be built.

Gender and age effects on metabolic rates of office work, housework, and different walking speeds

Metabolic rate is an essential factor in determining human thermal comfort. Existing metabolic rates for common activities in the current standards are based on mean adult values and do not include values for the middle-aged and the elderly. This study examines the metabolic rate of 151 Chinese male and female subjects aged 20 ∼ 69 during eighteen activities (reclining, 7 types of office work including seated and standing, 5 types of housework, and 5 walking speeds) using an indirect calorimeter in lab studies. The results show that women exhibited lower metabolic heat production rates (6–9% for sedentary and standing activities, 9–13% for household activities, and 4–9% for walking activities) than men across all activities, regardless of age. No age-related declines in metabolic heat production during lower activities (reclining, sedentary, standing, and household). Rather, metabolic heat production rates increased at a rate of 5–7 W/m2 per decade with age, which is contrary to popular beliefs. Women demonstrated a distinct pattern of changes compared to men, with significant declines observed in sitting and standing activities, at a rate of 2–3 W/m2 per decade. The ISO and ASHRAE standards tended to overestimate the metabolic rate for standing position activities and significantly underestimate the metabolic rate during walking. Some simple household activities, such as folding cloth, wiping windows, and vacuuming, had a moderate metabolic rate level, significantly higher than standing quiet. These findings could inform the development of interventions to promote healthy ageing and the design of more effective strategies for managing thermal comfort in different populations. It is suggested that the metabolic rate reference table or prediction method in international standards needs modification when applied to the Chinese population.

ANALYSIS OF HEAT RELEASE RATE IN ENGINE ROOM FIRES OF 300 GT FERRY RO-RO PASSENGER BY USING WATER MIST SYSTEM AND CO2 SYSTEM

Based on statistical data in recent years, there are still quite a number of ship accidents due to fires, including on passenger ships. The water mist system is a fire suppression system that allows it to be used in the engine room with the advantage that it can keep the heat production rate low during the extinguishing process and can be operated earlier than the CO2 system. The research is conducted by using fire dynamic simulator in the engine room of a 300 GT ferry ro-ro passenger to compare the heat release rate of fire without an extinguishing system, an existing CO2 system, and a water mist system. The result shows that the CO2 fire suppression system reduces the heat release rate more rapidly to the decay phase at 375 seconds while the water mist takes more than 900 seconds. However, the fully developed phase of the water mist suppression system occurs more quickly than CO2 because the sprinklers are activated shortly after a fire occurs. Unlike water mist, the CO2 system is activated at 60 seconds so that the pre-combustion, growth, flashover, and fully developed phases are at the same HRR and time as the natural one.

Continuous Monitoring of Entropy Production and Entropy Flow in Humans Exercising under Heat Stress.

Complex living systems, such as the human organism, are characterized by their self-organized and dissipative behaviors, where irreversible processes continuously produce entropy internally and export it to the environment; however, a means by which to measure human entropy production and entropy flow over time is not well-studied. In this article, we leverage prior experimental data to introduce an experimental approach for the continuous measurement of external entropy flow (released to the environment) and internal entropy production (within the body), using direct and indirect calorimetry, respectively, for humans exercising under heat stress. Direct calorimetry, performed with a whole-body modified Snellen calorimeter, was used to measure the external heat dissipation from the change in temperature and relative humidity between the air outflow and inflow, from which was derived the rates of entropy flow of the body. Indirect calorimetry, which measures oxygen consumption and carbon dioxide production from inspired and expired gases, was used to monitor internal entropy production. A two-compartment entropy flow model was used to calculate the rates of internal entropy production and external entropy flow for 11 middle-aged men during a schedule of alternating exercise and resting bouts at a fixed metabolic heat production rate. We measured a resting internal entropy production rate of (0.18 ± 0.01) W/(K·m2) during heat stress only, which is in agreement with published measurements. This research introduces an approach for the real-time monitoring of entropy production and entropy flow in humans, and aims for an improved understanding of human health and illness based on non-equilibrium thermodynamics.

Simulating of human physiological supersystems: interactions of cardiovascular, thermoregulatory and respiratory systems

Special quantitative model of the human thermoregulatory system (MTS) functioning with cardiovascular and lung systems is created. These systems form a human physiological supersystem (HPSS). MTS describes thermoregulatory responses to alterations of both external environmental physical characteristics and internal biological characteristics. Algorithms provide designing of scenarios including simulation of either short-time or long-time (hours or days) observations. Input data include different combinations of environmental variables (air or water temperature, air humidity, wind or water flow speed, light intensity, infrared radiation) for a naked or wear human, as well as for given dynamics of biological characteristics (rate of heat production including its components associated with metabolism and ATP molecules leasing during mental and physical activities). Human body is presented by a core, blood, and a skin compartments. Skin and lung evaporation are under hypothalamic control based on afferent impulse patterns from internal, and skin heat and cold receptors. Dynamic output data include blood, hypothalamic, and skin temperatures, hemodynamic parameters like heart rate, cardiac output, regional blood flows, vascular resistances, blood pressures, and regional blood volumes. Serotonin and melatonin concentrations modulating biological heat production rate are associated with a day/night light intensity. Currently, the PCbased simulator is autonomous software to be used both for educational purposes and for providing of special computer research. In a near future, this simulator has to be widened by models of kidneys, and a mechanism of liverpancreas interaction.

Agreement between the ventilated capsule and the KuduSmart® device for measuring sweating responses to passive heat stress and exercise.

The present study assessed agreement between a wireless sweat rate monitor (KuduSmart® device) and the ventilated capsule (VC) technique for measuring: (i) minute-averaged local sweat rate (LSR), (ii) sweating onset, (iii) sudomotor thermosensitivity, and (iv) steady-state LSR, during passive heat stress and exercise. It was hypothesized that acceptable agreement with no bias would be observed between techniques for all assessed sweating characteristics. On two separate occasions for each intervention, participants were either passively heated by recirculating hot water (49 °C) through a tube-lined garment until rectal temperature increased 1 °C over baseline (n=8), or a 60 min treadmill march at a fixed rate of heat production (∼500W, n=9). LSR of the forearm was concurrently measured with a VC and the KuduSmart® device secured within ∼2cm. Using a ratio scale Bland-Altman analysis with the VC as the reference, the KuduSmart® device demonstrated systematic bias and not acceptable agreement for minute-averaged LSR (1.17 [1.09, 1.27], CV=44.5%), systematic bias and acceptable agreement for steady-state LSR (1.16 [1.09,1.23], CV=19.5%), no bias and acceptable agreement for thermosensitivity (1.07 [0.99, 1.16], CV=23.2%), and no bias and good agreement for sweating onset (1.00 [1.00, 1.00], CV=11.1%). In total, ≥73% of all minute-averaged LSR observations with the KuduSmart® device (n=2743) were within an absolute error of<0.2mg/cm2/min to the VC, the reference minimum detectable change in measurement error of a VC on the forearm. Collectively, the KuduSmart® device may be a satisfactory solution for assessing the sweating response to heat stress where a VC is impractical.