scholarly journals A revised method to predict skin’s thermal resistance

2018 ◽  
Vol 22 (4) ◽  
pp. 1795-1802
Author(s):  
Lijuan Wang ◽  
Ding Chong ◽  
Yuhui Di ◽  
Hui Yi
Keyword(s):  
Heat Flux ◽  
High Temperature ◽  
Low Temperature ◽  
Thermal Resistance ◽  
Ambient Temperature ◽  
Skin Temperature ◽  
Heat Loss ◽  
Human Body ◽  
New Formula ◽  
Sweat Evaporation

Human body can adjust heat loss by vasoconstriction, vasodilatation, and other methods. The purpose of this research is to investigate whether the thermal resistance of skin reflects vasoconstriction and vasodilatation. For this aim, the ambient temperature was controlled as 18.1, 21.6, 24.9, 27, and 30.5?C, respectively. In each temperature, the skin temperature and heat flux in the forearm were recorded. Based on tested data, the thermal resistance was calculated by a common method. The results showed that the thermal resistance at low temperature was less than that at high temperature, which was contrary to the rule of vasoconstriction and vasodilatation. So a new formula for thermal resistance was presented based on skin diffusion, sweat evaporation, and mass transformation. The results showed that the new method could predict vasoconstriction and vasodilatation. The revised equation is a useful index for physiological thermoregulation.

Wind Chill*

1948 ◽  
Vol 29 (10) ◽  
pp. 487-493 ◽  
Author(s):  
Arnold Court
Keyword(s):  
Low Temperature ◽  
Heat Loss ◽  
Convective Heat ◽  
Human Body ◽  
Empirical Formula ◽  
Heat Removal ◽  
The Body ◽  
Total Heat ◽  
Wind Chill ◽  
Convective Heat Loss

The rate of heat removal from the human body by wind and low temperature was termed Wind Chill by Siple and expressed by an empirical formula. This paper discusses the formula critically, pointing out that this measure of the convective heat loss may be less than three-quarters of the total heat lost by the body. Siple's formula is compared with those of others, and the use of the formula is discussed.

A mechanism by which helium increases metabolism in small mammals

1960 ◽  
Vol 199 (2) ◽  
pp. 243-245 ◽  
Author(s):  
H. A. Leon ◽  
S. F. Cook
Keyword(s):  
Thermal Conductivity ◽  
Oxygen Consumption ◽  
Ambient Temperature ◽  
Skin Temperature ◽  
Heat Loss ◽  
Small Mammals ◽  
Thermal Gradient ◽  
Oxygen Mixture ◽  
Ambient Temperatures ◽  
Long Evans

The oxygen consumption of male Long-Evans rats was determined at three different ambient temperatures in air and in an equivalent helium-oxygen mixture. It was found that when the ambient temperature is near the skin temperature of the rat, the effect of helium is insignificant. If the ambient temperature is lowered, helium induces an increased metabolism over air at the same temperature. Since helium has a thermal conductivity about six times greater than nitrogen, it is concluded that the accelerated metabolism is in response to the greater heat loss in the presence of helium and the magnitude of this response is proportional to the thermal gradient between the animal and the environment.

scholarly journals PERUBAHAN SUHU LINGKUNGAN TERHADAP WAKTU TRIP PADA MINI CIRCUIT BREAKER 6A TIPE C

2020 ◽  
Vol 5 (1) ◽  
pp. 6-13
Author(s):  
Dhelvian Gading Primadhika ◽  
Parjiman ◽  
Djaohar Mochammad ◽  
Himma Firdaus
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Ambient Temperature ◽  
Temperature Effect ◽  
Temperature Change ◽  
Research Result ◽  
Circuit Breaker ◽  
Reference Temperature ◽  
Voltage Source ◽  
Circuit Breakers

ABSTRACT The purpose of this research is to know about the effect of current rate increasing and ambient temperature change on tripping time miniature circuit breakers 6A type C. In this research using an experimental method approach with the quantitative method. The research subject used five samples new miniature circuit breakers produced by Asian and European brand. The research data collection is carried out by testing using PLN voltage source, linier load and temperature change on chamber to know five samples miniature circuit breakers characteristics tripping time refer to SPLN 108:1993. The research result showed that, current rate increasing to ± 2.55 In and ambient temperature change have an effect on five samples miniature circuit breakers characteristics tripping time, where on reference temperature, different characteristics tripping time for each other however were still within the standard limits SPLN 108:1993. Next on low temperature testing, five samples miniature circuit breakers have change tripping time to be slowed rather than reference temperature testing with deviation MCB A 1.75 until 497.90 second, MCB B 3.81 until 114.89 second, MCB C 2.04 second until 637.42 second, MCB D 0.33 until 1647.96 second, dan MCB E 2.89 until 234.49 second. Last on high temperature testing five samples miniature circuit breakers have change tripping time to be faster rather than reference temperature testing with deviation MCB A 2.63 until 396.93 second, MCB B 2.78 until 251.96 second, MCB C 5.79 second until 775.25 second, MCB D 8.27 until 339.49 second, dan MCB E 3.86 until 95.02 second. Based on this research result, each increase current rate flow through miniature circuit breakers, than miniature circuit breakers tripping time to be faster. When miniature circuit breakers was given low temperature effect, than miniature circuit breakers have change tripping time to be slowed rather than reference temperature. While miniature circuit breakers was given high temperature effect, than miniature circuit breakers have change tripping time to be faster rather than reference temperature.   ABSTRAK Tujuan dari penelitian ini adalah untuk mengetahui pengaruh kenaikan besar arus listrik yang disertai dengan perubahan suhu lingkungan terhadap waktu trip pada mini circuit breaker 6A Tipe C. Metode yang digunakan adalah metode eksperimen dengan pendekatan metode kuantitatif. Subjek penelitian yang akan diteliti adalah MCB yang dalam kondisi baru berjumlah 5 sampel produksi asia maupun eropa. Pengumpulan data penelitian dilakukan dengan pengujian menggunakan sumber tegangan PLN, beban linier dan perubahan suhu di chamber pengujian untuk mengetahui karakteristik waktu trip 5 MCB yang mengacu pada SPLN 108:1993. Hasil penelitian menunjukan bahwa, peningkatan besar arus hingga ±2.55 In dan perubahan suhu mempunyai pengaruh terhadap karakteristik waktu trip 5 sampel MCB, dimana pada suhu refrensi masing-masing memiliki perbedaan karakteristik waktu trip namun masih dalam batas standar SPLN 108:1993. Lalu pada pengujian dengan suhu rendah, 5 sampel MCB masing-masing mengalami perubahan waktu trip yang lebih lambat dari pengujian pada suhu refrensi dengan deviasi MCB A 1.75 hingga 497.90 detik, MCB B 3.81 hingga 114.89 detik, MCB C 2.04 detik hingga 637.42 detik, MCB D 0.33 hingga 1647.96 detik, dan MCB E 2.89 hingga 234.49 detik. Sedangkan pada pengujian dengan suhu tinggi 5 sampel MCB masing-masing mengalami perubahan waktu trip yang lebih cepat dari pengujian pada suhu refrensi dengan deviasi MCB A 2.63 hingga 396.93 detik, MCB B 2.78 hingga 251.96 detik, MCB C 5.79 detik hingga 775.25 detik, MCB D 8.27 hingga 339.49 detik, dan MCB E 3.86 hingga 95.02 detik. Dari hasil pengujian yang telah dilakukan di dapatkan hasil semakin besar arus yang melewati MCB maka akan lebih cepat MCB akan trip. Lalu dengan di beri pengaruh suhu rendah, maka MCB akan lebih lambat untuk trip. Sedangkan dengan di beri pengaruh suhu tinggi, maka MCB akan lebih cepat untuk trip.

Thermoregulation properties of composite phase change materials in high temperature environmental conditions

2018 ◽  
Vol 30 (4) ◽  
pp. 507-516 ◽  
Author(s):  
Kai Yang ◽  
Mingli Jiao ◽  
Sifan Wang ◽  
Yuanyuan Yu ◽  
Quan Diao ◽  
...  
Keyword(s):  
High Temperature ◽  
Phase Change ◽  
Skin Temperature ◽  
Human Body ◽  
Environmental Conditions ◽  
Phase Change Materials ◽  
Content Type ◽  
Temperature Conditions ◽  
Composite Phase Change Materials ◽  
C 50

Purpose The purpose of this paper is to investigate thermoregulation properties of different composite phase change materials (PCMs), which could be used in the high temperature environmental conditions to protect human body against the extra heat flow. Design/methodology/approach Three kinds of composite PCM samples were prepared using the selected pure PCMs, including n-hexadecane, n-octadecane and n-eicosane. The DSC experiment was performed to get the samples’ phase change temperature range and enthalpy. The simulated high temperature experiments were performed using human arms in three different high temperature conditions (40°C, 45°C, 50°C), and the skin temperature variation curves varying with time were obtained. Then a comprehensive index TGP was introduced from the curves and calculated to evaluate the thermoregulation properties of different composite PCM samples comprehensively. Findings Results show that the composite PCM samples could provide much help to the high temperature human body. It could decrease the skin temperature quickly in a short time and it will not cause the over-cooling phenomenon. Comparing with other two composite PCM samples, the thermoregulation properties of the n-hexadecane and n-eicosane composite PCM is the best. Originality/value Using the n-hexadecane and n-eicosane composite PCM may provide people with better protection against the high temperature conditions, which is significative for the manufacture of functional thermoregulating textiles, garments or equipments.

Update of model to predict sensible heat loss in broilers

2017 ◽  
Vol 57 (9) ◽  
pp. 1877
Author(s):  
Marcos José Batista dos Santos ◽  
Nilva Kazue Sakomura ◽  
Edney Pereira da Silva ◽  
Juliano César de Paula Dorigam ◽  
Alex Sandro Campos Maia
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Wind Speed ◽  
Thermal Resistance ◽  
Heat Loss ◽  
Air Temperature ◽  
Contact Area ◽  
Sensible Heat ◽  
Volume Factor ◽  
Thermal Discomfort

The present study was conducted to adjust and adapt some parameters of the model of production and heat loss by convection and conduction, so as to predict the actual feed intake (aFI) of broilers reared in sheds. The re-parameterised models were the sensible heat loss by convection from surface (HS) and by conduction (HC) in birds. The HS model was re-parameterised to calculate the heat loss of poultry reared in sheds and the parameters of thermal resistance of feathers (RF) and skin (RS) of poultry were inserted. The HC model was re-parameterised for birds in sheds and the RF, RS and the thermal resistance of the litter (R) were inserted. The re-parameterised HS model was HS = [A × QV × (TB – TA)]/[(TB – 17) × (RF + RS)], where TA is the air temperature, QV is the volume factor, TB is the surface temperature of the bird (°C) and A was estimated to be 11.94 watts (W). The values found in the model ranged from 0.75 W for birds with 100 g BW subjected to 33°C TA, 50% HU, 0.1 m/s wind speed (V) and 12.53 W for birds with 4100 g subjected to 33°C TA, 80% HU and 0.1 m/s V. The values found in the re-parameterised HC model (HC = [(TB – TC) × k × AR × QA]/[L × (RF + RS + R)], where K is the thermal conductivity of the litter, AR is the contact area of bird with the litter and QA is the area factor, and L is the litter height) ranging from 0.017 W to chickens with 100 g BW in comfortable conditions and 0.17 W for birds with 4100 g in thermal discomfort condition. The present study showed that the re-parameterisation of heat-loss equations is more accurate to predict the heat flux in broilers under different environmental conditions.

Influence of heating rate on control of heat loss from the tail in mice

1983 ◽  
Vol 244 (6) ◽  
pp. R778-R784
Author(s):  
C. J. Gordon
Keyword(s):  
Ambient Temperature ◽  
Skin Temperature ◽  
Heating Rate ◽  
Heat Loss ◽  
Heat Load ◽  
Whole Body ◽  
Heat Absorption ◽  
Heat Gain ◽  
Microwave Exposure ◽  
Body Heat

Although heating rate is important for stimulating thermoregulatory reflexes, it is not known if the control system differentiates between total heat gain and rate of heat gain. Exposing animals to microwaves inside a waveguide permits continuous monitoring of whole-body heat absorption. Tail skin temperature of restrained mice was recorded during whole-body exposure to 2,450-MHz microwave radiation at specific absorption rates (SAR) of either 11.5, 21.7, or 43.5 W . kg-1 and whole-body heat loads of 0.3-14 J . g-1. The integration of tail skin temperature with time, defined as the skin temperature index (STI), was measured as a function of absorbed heat load. At ambient temperatures of 20 and 25 degrees C the STI, averaged with respect to heat load, increased significantly with SAR. Depending on SAR, the sensitivity of heat loss from the tail to microwave exposure increased 32-71% per 1 degree C elevation in ambient temperature. The data indicate that heat loss from the tail increases with the whole-body heat load accrued from microwave exposure. When heat loss is averaged with respect to heat load, the rate of heat absorption and ambient temperature increase the sensitivity of thermoregulatory centers that control peripheral heat loss from the tail of mice.

The Ratio of Sunflower Pollens Foraged by Apis mellifera Is More Than That of Apis cerana Does During Sunflower Blooming

Sociobiology ◽  
2020 ◽  
Vol 67 (2) ◽  
pp. 256
Author(s):  
Huipeng Yang ◽  
Jia Sun ◽  
Peng Tang ◽  
Changsheng Ma ◽  
Shudong Luo ◽  
...  
Keyword(s):  
High Temperature ◽  
Apis Mellifera ◽  
Low Temperature ◽  
Ambient Temperature ◽  
Honey Bee ◽  
Apis Cerana ◽  
Pollen Foraging

Bias foraging of pollen is general in different pollinators since various nutrition demanding, co-evolution and interaction of insect-plant. To clarify the preference of pollen foraging during sunflower blooming, the pollen foraging behaviors of Apis mellifera Linnaeus and Apis cerana Fabricius were observed. Our results displayed that two summits of pollen foraging occurred in the morning before the ambient temperature climbed up to thirty-one degree centigrade and in the afternoon after the ambient temperature decreased below thirty-one degree centigrade, respectively. Notably, the first foraging summit of Apis cerana emerged one hour earlier than that of Apis mellifera. These results imply that Apis mellifera is less resistant to low temperature but more resistant to high temperature than Apis cerana does. The colonies were surrounded by sunflowers with sporadic weeds, while only few maize dispersed over two hundred meters away. However, no more than forty percent of total pollens foraged by Apis mellifera was from sunflower, and which was no more than twenty percent in Apis cerana group. These results suggest that sunflower pollens are not the prior choice for both honey bee species, while the ratio of sunflower pollens foraged by Apis mellifera is more than that of Apis cerana does.

Ambient Temperature Operation of a Platinum-Free Direct Formate Fuel Cell

2015 ◽  
Vol 12 (1) ◽  
Author(s):  
Tien Q. Nguyen ◽  
Daniel Minami ◽  
Chau Hua ◽  
Austin Miller ◽  
Kevin Tran ◽  
...  
Keyword(s):  
High Temperature ◽  
Fuel Cell ◽  
Low Temperature ◽  
Ambient Temperature ◽  
Power Density ◽  
Second Generation ◽  
Cathode Catalyst ◽  
Maximum Power Density ◽  
Direct Formate Fuel Cell ◽  
Fuel Stream

Several reports have been made recently of the direct formate fuel cell (DFFC) operating at high-temperature and using Pt cathode catalyst. In the present work, we demonstrate a Pt-free DFFC employing ACTA HypermecTM 4020 Fe–Co second-generation cathode catalyst operating at low-temperature. We report a maximum power density (PD) of 45 mW cm−2 at ambient temperature (20 °C), when the fuel stream was 1 M HCOOK and 2 M KOH with oxygen used at the cathode. When air was used at the cathode, the maximum PD was 35 mW cm−2. When hydroxide was removed from the fuel stream and oxygen used at the cathode, the maximum PD at 20 °C was 18 mW cm−2. This low-temperature, KOH-free operation is important to development of a practical DFFC.

Study on subjective sensation and physiological reaction with high physical activity influenced by air temperature of stadium

2019 ◽  
Vol 29 (10) ◽  
pp. 1336-1345
Author(s):  
Yongqiang Xiao ◽  
Yaping Gao ◽  
Yi Wang
Keyword(s):  
Physical Activity ◽  
High Temperature ◽  
Ambient Temperature ◽  
Human Body ◽  
Physiological Response ◽  
Thermal Environment ◽  
Thermal Sensation ◽  
Quantitative Relationship ◽  
High Physical Activity ◽  
Subjective Sensation

As the main venue for sports training and competition, the thermal environment of a stadium directly could affect the comfort and health of a moving body and sports performance. In this study, the quantitative relationship between ambient temperature and subjective sensation evaluation was established by monitoring the actual thermal sensation evaluation, fatigue sensation cognition and physiological response with high physical activity, under different conditions of ambient temperature. The results show that 90% of subjects can actually accept an ambient temperature range of 18.6°C–26°C. This is 2°C higher than the maximum recommended range in the ISO 7730:2005 thermal comfort standard, reflecting a strong tolerance of the moving human body to low or high temperature environments. A high temperature environment could cause exercise fatigue to occur prematurely. Moreover, the study suggests that the critical point for early occurrence of fatigue sensation in a moving human body is 28°C. The relationship between the environmental temperature and the physiological response was evaluated by mean skin temperature, blood pressure and heart rate of the human body. These are used as evaluation indexes of physiological parameters. Ambient temperature has a significant effect on the objective physiological response of the moving human body, which coincides with the subject’s definition of subjective sensory evaluation to the ambient temperature.

scholarly journals Human transient response under local thermal stimulation

2017 ◽  
Vol 21 (suppl. 1) ◽  
pp. 19-24
Author(s):  
Lijuan Wang ◽  
Yudong Wang ◽  
Guohua Tian ◽  
Yuhui Di
Keyword(s):  
Heart Rate ◽  
Heat Flux ◽  
High Temperature ◽  
Transient Response ◽  
Human Body ◽  
Thermal Sensation ◽  
Whole Body ◽  
Local Part ◽  
Hot Environment ◽  
Different Temperatures

Human body can operate physiological thermoregulation system when it is exposed to cold or hot environment. Whether it can do the same work when a local part of body is stimulated by different temperatures? The objective of this paper is to prove it. Twelve subjects are recruited to participate in this experiment. After stabilizing in a comfort environment, their palms are stimulated by a pouch of 39, 36, 33, 30, and 27?C. Subject?s skin temperature, heart rate, heat flux of skin, and thermal sensation are recorded. The results indicate that when local part is suffering from harsh temperature, the whole body is doing physiological thermoregulation. Besides, when the local part is stimulated by high temperature and its thermal sensation is warm, the thermal sensation of whole body can be neutral. What is more, human body is more sensitive to cool stimulation than to warm one. The conclusions are significant to reveal and make full use of physiological thermoregulation.

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