Evaporative Heat Loss Research Articles

Increased Air Velocity Reduces Thermal and Cardiovascular Strain in Young and Older Males during Humid Exertional Heat Stress

Older adults have been reported to have a lower evaporative heat loss capacity than younger adults during exercise when full sweat evaporation is permitted. However, it is unclear how conditions of restricted evaporative and convective heat loss (i.e., high humidity, clothing insulation) alter heat stress. to the purpose of this study was to examine the heat stress responses of young and older males during and following exercise in a warm/humid environment under two different levels of air velocity. Ten young (YOUNG: 24±2 yr) and 10 older (OLDER: 59±3 yr) males, matched for body surface area performed 4×15-min cycling bouts (15-min rest) at a fixed rate of heat production (400 W) in warm/humid conditions (35°C, 60% relative humidity) under 0.5 (Low) and 3.0 (High) m·s−1 air velocity while wearing work coveralls. Rectal (Tre) and mean skin (MTsk) temperatures, heart rate (HR), local sweat rate, % max skin blood flow (SkBF) (recovery only), and blood pressure (recovery only) were measured. High air velocity reduced core and skin temperatures (p < 0.05) equally in YOUNG and OLDER males (p > 0.05) but was more effective in reducing cardiovascular strain (absolute and % max HR; p < 0.05) in YOUNG males (p < 0.05). Greater increases in local dry heat loss responses (% max SkBF and cutaneous vascular conductance) were detected across time in OLDER than YOUNG males in both conditions (p < 0.05). Local dry heat loss responses and cardiovascular strain were attenuated during the High condition in YOUNG compared to OLDER (p < 0.05). High air velocity reduced the number of males surpassing the 38.0°C Tre threshold from 90% (Low) to 50% (High). Despite age-related local heat loss differences, YOUNG and OLDER males had similar levels of heat stress during intermittent exercise in warm and humid conditions while wearing work coveralls. Increased air velocity was effective in reducing heat stress equally, and cardiovascular strain to a greater extent, in YOUNG and OLDER males, and may be useful for mitigating heat stress in all workers.

Higher oesophageal temperature at rest and during exercise in humans with patent foramen ovale.

Respiratory system cooling occurs via convective and evaporative heat loss, so right-to-left shunted blood flow through a patent foramen ovale (PFO) would not be cooled. Accordingly, we hypothesized that PFO+ subjects would have a higher core temperature than PFO- subjects due, in part, to absence of respiratory system cooling of the shunted blood and that this effect would be dependent upon the estimated PFO size and inspired air temperature. Subjects were screened for the presence and size of a PFO using saline contrast echocardiography. Thirty well-matched males (15 PFO-, 8 large PFO+, 7 small PFO+) completed cycle ergometer exercise trials on three separate days. During Trial 1, subjects completed a V̇(O2max) test. For Trials 2 and 3, randomized, subjects completed four 2.5 min stages at 25, 50, 75 and 90% of the maximum workload achieved during Trial 1, breathing either ambient air (20.6 ± 1.0°C) or cold air (1.9 ± 3.5°C). PFO+ subjects had a higher oesophageal temperature (T(oesoph)) (P < 0.05) than PFO- subjects on Trial 1. During exercise breathing cold and dry air, PFO+ subjects achieved a higher T(oesoph) than PFO- subjects (P < 0.05). Subjects with a large PFO, but not those with a small PFO, had a higher T(oesoph) than PFO- subjects (P < 0.05) during Trial 1 and increased T(oesoph) breathing cold and dry air. These data suggest that the presence and size of a PFO are associated with T(oesoph) in healthy humans but this is explained only partially by absence of respiratory system cooling of shunted blood.

A novel personal cooling system (PCS) incorporated with phase change materials (PCMs) and ventilation fans: An investigation on its cooling efficiency

Personal cooling systems (PCS) have been developed to mitigate the impact of severe heat stress for humans working in hot environments. It is still a great challenge to develop PCSs that are portable, inexpensive, and effective. We studied the performance of a new hybrid PCS incorporating both ventilation fans and phase change materials (PCMs). The cooling efficiency of the newly developed PCS was investigated on a sweating manikin in two hot conditions: hot humid (HH, 34°C, 75% RH) and hot dry (HD, 34°C, 28% RH). Four test scenarios were selected: fans off with no PCMs (i.e., Fan-off, the CONTROL), fans on with no PCMs (i.e., Fan-on), fans off with fully solidified PCMs (i.e., PCM+Fan-off), and fans on with fully solidified PCMs (i.e., PCM+Fan-on). It was found that the addition of PCMs provided a 54∼78min cooling in HH condition. In contrast, the PCMs only offered a 19–39min cooling in HD condition. In both conditions, the ventilation fans greatly enhanced the evaporative heat loss compared with Fan-off. The hybrid PCS (i.e., PCM+Fan-on) provided a continuous cooling effect during the three-hour test and the average cooling rate for the whole body was around 111 and 315W in HH and HD conditions, respectively. Overall, the new hybrid PCS may be an effective means of ameliorating symptoms of heat stress in both hot-humid and hot-dry environments.

Effect of sweating set rate on clothing real evaporative resistance determined on a sweating thermal manikin in a so-called isothermal condition (T manikin = T a = T r).

The ASTM F2370 (2010) is the only standard with regard to measurement of clothing real evaporative resistance by means of a sweating manikin. However, the sweating set-point is not recommended in the standard. In this study, the effect of sweating rate on clothing real evaporative resistance was investigated on a 34-zone "Newton" sweating thermal manikin in a so-called isothermal condition (T manikin = T a = T r). Four different sweating set rates (i.e., all segments had a sweating rate of 400, 800, 1200 ml/hr ∙ m(2), respectively, and different sweating rates were assigned to different segments) were applied to determine the clothing real evaporative resistance of five clothing ensembles and the boundary air layer. The results indicated that the sweating rate did not affect the real evaporative resistance of clothing ensembles with the absence of strong moisture absorbent layers. For the clothing ensemble with tight cotton underwear, a sweating rate of lower than 400 ml/hr ∙ m(2) is not recommended. This is mainly because the wet fabric "skin" might not be fully saturated and thus led to a lower evaporative heat loss and thereby a higher real evaporative resistance. For vapor permeable clothing, the real evaporative resistance determined in the so-called isothermal condition should be corrected before being used in thermal comfort or heat strain models. However, the reduction of wet thermal insulation due to moisture absorption in different test scenarios had a limited contribution to the effect of sweating rate on the real evaporative resistance.

Temperature of Ingested Water during Exercise Does Not Affect Body Heat Storage.

The objective of this study was to examine the effect of ingested water temperature on heat balance during exercise as assessed by direct calorimetry. Ten healthy males (25 ± 4 yr) cycled at 50% V˙O2peak (equivalent rate of metabolic heat production (M-W) of 523 ± 84 W) for 75 min under thermocomfortable conditions (25°C, 25% relative humidity) while consuming either hot (50°C) or cold (1.5°C) water. Four 3.2 mL·kg⁻¹ boluses of hot or cold water were consumed 5 min before and at 15, 30, and 45 min after the onset of exercise. Total heat loss (HL = evaporative heat loss (HE) ± dry heat exchange (HD)) and M-W were measured by direct and indirect calorimetry, respectively. Change in body heat content (ΔHb) was calculated as the temporal summation of M-W and HL and adjusted for changes in heat transfer from the ingested fluid (Hfluid). The absolute difference for HL (209 ± 81 kJ) was similar to the absolute difference of Hfluid (204 ± 36 kJ) between conditions (P = 0.785). Furthermore, the difference in HL was primarily explained by the corresponding changes in HE (hot: 1538 ± 393 kJ; cold: 1358 ± 330 kJ) because HD was found to be similar between conditions (P = 0.220). Consequently, no difference in ΔHb was observed between the hot (364 ± 152 kJ) and cold (363 ± 134 kJ) conditions (P = 0.971) during exercise. We show that ingestion of hot water elicits a greater HL relative to cold water ingestion during exercise. However, this response was only compensated for the heat of the ingested fluid as evidenced by similar ΔHb between conditions. Therefore, our findings indicate that relative to cold water ingestion, consuming hot water does not provide a thermoregulatory advantage. Both hot and cold water ingestion results in the same amount of heat stored during prolonged moderate-intensity exercise.

Older firefighters are susceptible to age-related impairments in heat dissipation.

The aging-induced reduction in whole-body heat loss (HL) capacity generates concerns regarding the continued participation of older workers in occupations such as firefighting. We compared HL and change in body heat storage (S) during intermittent exercise in warm/dry and warm/humid conditions among older male firefighters (OLDER, n = 9, age = 54.7 ± 2.1 yr), older (age-matched) nonfirefighters (NON-FF, n = 9, age = 52.8 ± 1.2 yr), and young firefighters (YOUNG, n = 6, age = 26.7 ± 0.8 yr). We measured evaporative heat loss and dry heat exchange via the Snellen whole-body direct calorimeter while participants performed four 15-min bouts of cycling at 400 W of metabolic heat production separated by 15-min recovery periods in warm/dry (35 °C, 20% relative humidity) and warm/humid (35 °C, 60% relative humidity) conditions. We found no differences (P > 0.05) in HL or cumulative S (ΔS) between OLDER and NON-FF in the warm/dry (ΔS: OLDER = 233 ± 26 kJ, NON-FF = 270 ± 29 kJ) or warm/humid (ΔS: OLDER = 548 ± 24 kJ, NON-FF = 504 ± 47 kJ) conditions. The OLDER and NON-FF had lower HL than the YOUNG during exercise in both environmental conditions (P < 0.05). The OLDER stored 40% (P > 0.05) and 46% (P = 0.004) more heat than YOUNG in the warm/dry and warm/humid conditions, respectively. The NON-FF stored 63% (P = 0.016) and 34% (P = 0.025) more heat than the YOUNG in the dry and humid conditions, respectively. Older firefighters and age-matched nonfirefighters demonstrate similar HL and S during work in the heat. Moreover, HL is significantly reduced in older compared to younger firefighters during exercise in both warm/dry and warm/humid conditions. Consequently, older firefighters may be more susceptible to thermal injury while on duty than their younger counterparts.

Estimation of human heat loss in five Mediterranean regions

This study investigates the effects of seasonal weather differences on the human body's heat losses in the Mediterranean region of Turkey. The provinces of Adana, Antakya, Osmaniye, Mersin and Antalya were chosen for the research, and monthly atmospheric temperatures, relative humidity, wind speed and atmospheric pressure data from 2007 were used. In all these provinces, radiative, convective and evaporative heat losses from the human body based on skin surface and respiration were analyzed from meteorological data by using the heat balance equation. According to the results, the rate of radiative, convective and evaporative heat losses from the human body varies considerably from season to season. In all the provinces, 90% of heat loss was caused by heat transfer from the skin, with the remaining 10% taking place through respiration. Furthermore, radiative and convective heat loss through the skin reached the highest values in the winter months at approximately between 110 and 140W/m2, with the lowest values coming in the summer months at roughly 30–50W/m2.

Correction of the heat loss method for calculating clothing real evaporative resistance

In the so-called isothermal condition (i.e., Tair [air temperature]=Tmanikin [manikin temperature]=Tr [radiant temperature]), the actual energy used for moisture evaporation detected by most sweating manikins was underestimated due to the uncontrolled fabric ‘skin’ temperature Tsk,f (i.e., Tsk,f<Tmanikin). Thus, it must be corrected before being used to compute the clothing real evaporative resistance. In this study, correction of the real evaporative heat loss from the wet fabric ‘skin’–clothing system was proposed and experimentally validated on a ‘Newton’ sweating manikin. The real evaporative resistance of five clothing ensembles and the nude fabric ‘skin’ calculated by the corrected heat loss method was also reported and compared with that by the mass loss method. Results revealed that, depending on the types of tested clothing, different amounts of heat were drawn from the ambient environment. In general, a greater amount of heat was drawn from the ambient environment by the wet fabric ‘skin’-clothing system in lower thermal insulation clothing than that in higher insulation clothing. There were no significant differences between clothing real evaporative resistances calculated by the corrected heat loss method and those by the mass loss method. It was therefore concluded that the correction method proposed in this study has been successfully validated.

Physiological Responses and Lactation to Cutaneous Evaporative Heat Loss in Bos indicus, Bos taurus, and Their Crossbreds.

Cutaneous evaporative heat loss in Bos indicus and Bos taurus has been well documented. Nonetheless, how crossbreds with different fractional genetic proportions respond to such circumstances is of interest. A study to examine the physiological responses to cutaneous evaporative heat loss, also lactation period and milk yield, were conducted in Sahiwal (Bos indicus, n = 10, 444±64.8 kg, 9±2.9 years), Holstein Friesian (Bos taurus, HF100% (n = 10, 488±97.9 kg, 6±2.8 years)) and the following crossbreds: HF50% (n = 10, 355±40.7 kg, 2±0 years) and HF87.5% (n = 10, 489±76.8 kg, 7±1.8 years). They were allocated so as to determine the physiological responses of sweating rate (SR), respiration rate (RR), rectal temperature (RT), and skin temperature (ST) with and without hair from 06:00 h am to 15:00 h pm. And milk yield during 180 days were collected at days from 30 to 180. The ambient temperature-humidity-index (THI) increased from less than 80 in the early morning to more than 90 in the late afternoon. The interaction of THI and breed were highly affected on SR, RR, RT, and ST (p<0.01). The SR was highest in Sahiwal (595 g/m2/h) compared to HF100% (227 g/m2/h), and their crossbreds both HF50% (335 g/m2/h) and HF87.5% (299 g/m2/h). On the other hand, RR was higher in HF87.5% (54 bpm) and both HF100% (48 bpm) and HF50% (42 bpm) than Sahiwal (25 bpm) (p<0.01). The RT showed no significant differences as a result of breed (p>0.05) but did change over time. The ST with and without hair were similar, and was higher in HF100% (37.4°C; 38.0°C) and their crossbred HF50% (35.5°C; 35.5°C) and HF87.5% (37.1°C; 37.9°C) than Sahiwal (34.8°C; 34.8°C) (p<0.01). Moreover, the early lactation were higher at HF100% (25 kg) and 87.5% (25 kg) than HF50% (23 kg) which were higher than Sahiwal (18 kg) while the peak period of lactation was higher at HF100% (35 kg) than crossbreds both HF87.5% and HF50% (32 kg) which was higher than Sahiwal (26 kg) (p<0.05). In conclusion, sweating and respiration were the main vehicle for dissipating excess body heat for Sahiwal, HF and crossbreds, respectively. The THI at 76 to 80 were the critical points where the physiological responses to elevated temperature displayed change.

Detrimental Reductions In Evaporative Heat Loss During Cycling Following Ice Slurry Ingestion In The Heat

PURPOSE: To compare the magnitude of reduction in evaporative heat loss from the skin (Esk) with different levels of internal heat loss (Hint) induced by ice slurry and 1.5°C fluid ingestion relative to 37°C fluid ingestion during cycling in a hot environment. METHODS: Nine men RESULTS: All data are expressed relative to the NEU trial. Hprod was similar to NEU in both trials (COL: +34±154 kJ; P=0.52, ICE +17±210 kJ; P=0.81). Hint was progressively lower in the COL (-105±18 kJ) and ICE (-200±20 kJ) trials relative to NEU. In parallel, Esk was also progressively lower in the COL (-137±165 kJ; P=0.037) and ICE (-381±199 kJ; P<0.001) trials. However while evaporative reductions were equal to Hint in the COL trial (P=0.64), they were greater than Hint in the ICE trial (P=0.05), leading to a greater heat storage with ICE ingestion. Mean local sweat rates (COL: -0.06 ±0.09 mg•min-1•cm-2; P=0.09, ICE: -0.16±0.14 mg•min-1•cm-2; P=0.009) and whole-body sweat losses (COL: -56±69 g; P=0.04, ICE: -191±122 g; P<0.001) were lower compared to NEU. Conversely, changes in Tre (COL: +0.04±0.24°C; P=0.63, ICE: +0.07±0.12°C; P=0.11), Tsk (COL: -0.07±0.35°C; P=0.55, ICE: -0.04±0.38°C; P=0.74) and local skin blood flow (COL: -2.9±10.9%max, P=0.45; ICE: -6.8±13.7%max, P=0.18) were similar to the NEU trial. CONCLUSIONS: The greater internal loss with 1.5°C fluid, relative to 37°C fluid, was balanced by an equal reduction in Esk. However the internal heat loss with ice slurry ingestion, relative to 37°C fluid, was paralleled by a disproportionately greater reduction in Esk. These results indicate that the temperature of an ingested fluid has no net influence on human heat balance, but ice slurries should potentially be avoided.

Whole-body heat exchange during heat acclimation and its decay.

The purpose of this study was to quantify how much whole-body heat loss increases during heat acclimation and the decay in these improvements after heat acclimation. Ten males underwent a 14-d heat acclimation protocol that consisted of 90 min of cycling in the heat (40°C, 20% relative humidity) at approximately 50% of maximum oxygen consumption. Before (day 0), during (day 7), and at the end (day 14) of the heat acclimation protocol as well as 7 and 14 d after heat acclimation (days 21 and 28), whole-body heat exchange (evaporative and dry) was measured using direct calorimetry during three bouts of 30-min exercise at 300 (Ex1), 350 (Ex2), and 400 W·m (Ex3), each separated by 10 and 20 min of recovery, respectively, at 35°C and 16% relative humidity. Concurrent measurements of metabolic heat production (indirect calorimetry) allowed for the direct calculation of change in body heat content (ΔHb). After accounting for an increase in net dry heat gain, increases in whole-body evaporative heat loss were evident for Ex2 and Ex3 on day 7 (Ex2, 4.9 ± 5.6%; Ex3, 9.0 ± 6.0%; both P ≤ 0.05) and all heat loads on day 14 (Ex1, 7.6 ± 8.3%; Ex2, 7.7 ± 5.5%; Ex3, 11.2 ± 4.6%; all P ≤ 0.05) relative to day 0 (Ex1, 494 ± 27 W; Ex2, 583 ± 21 W; Ex3, 622 ± 36 W). As a result, a lower cumulative ΔHb was measured on day 7 (-18 ± 8%, P ≤ 0.001) and day 14 (-26 ± 10%, P ≤ 0.001) compared with that measured on day 0 (1062 ± 123 kJ). Most of these improvements were retained after 2 wk of nonexposure to the heat. This is the first study to quantify how much 14 d of heat acclimation can increase whole-body evaporative heat loss, which can improve by as much as approximately 11%.

A comprehensive study on autothermal thermophilic aerobic digestion process of waste activated sludge in a continuous stirred digester

In this research autothermal thermophilic aerobic digestion (ATAD) of a typical waste activated sludge (WAS) was investigated in a continuous stirred digester, precisely. Volatile solids (VS) reduction, energy audit, pathogen inactivation and sludge dewaterability during aerobic digestion were studied. Two processes with air and pure oxygen sparging were performed and their results were compared. In a continuous ATAD system working with WAS, feeds concentrated preliminary more than 30 g/L can provide stable temperatures above 40°C in aerobic digester. Similarly, sludge feeds concentrated initially above 20 g/L can provide stable temperatures above 43°C in an oxygen sparged aerobic digester. Sludge feeds with total solids concentrations of 60 and 10 g/L demonstrated the highest (57°C) and the lowest (24°C) reactor temperature, respectively. Feed sludges having thickest concentrations of 60 and 50 g/L which caused the thermophilic temperatures of 57°C and 51°C in the reactor, provided moderately dewaterable sludges. In oxygen sparged process, evaporation heat loss was reduced and temperature profiles were higher and also, pathogen removal was sensibly improved in compared with air sparged system.

Effect of Environmental Heat Stress on Reproduction Performance of Dairy Cows- A Review

Stress is the condition where there is undue demand for physical and mental energy due to excessive and aversive environmental factors (stressors) and cause deformations those are identifiable through physiological disequilibrium. Temperature stress imparts physical and economical losses to livestock production in temperate, subtropical and tropical regions of the world. Each species, breed or animal with its physiological state, has a comfort zone, in which the energy expenditure of the animal is minimal, constant and independent of environmental temperature. When environmental temperatures move out of the thermo-neutral zone (or comfort zone) dairy cattle begin to experience heat stress. Thermo-neutral zone depends on the age, breed, feed intake, diet composition, previous state of temperature acclimatization, production, housing and stall conditions, tissue (fat, skin) insulation and external (coat) insulation, and the behaviour of the animal. The ranges of thermo-neutral zone are from lower critical temperature (LCT) to upper critical temperature (UCT). LCT is the environmental temperature at which an animal needs to increase metabolic heat production to maintain body temperature. UCT is the environmental temperature at which the animal increases heat production as a consequence of a rise in body temperature resulting for inadequate evaporative heat loss. Heat stress negatively impacts a variety of dairy parameters including milk yield and reproduction and therefore is a significant financial burden in many dairy-producing areas of the world. Advances in management (i.e. cooling systems) and nutritional strategies have alleviated some of the negative impact of thermal stress on dairy cattle, but production continues to decrease during the summer. In this review an attempt has been made to bring forth the effect of heat stress and to discuss their impact on dairy cows.

Aging impairs heat loss, but when does it matter?

Aging is associated with an attenuated physiological ability to dissipate heat. However, it remains unclear if age-related impairments in heat dissipation only occur above a certain level of heat stress and whether this response is altered by aerobic fitness. Therefore, we examined changes in whole body evaporative heat loss (HE) as determined using whole body direct calorimetry in young (n = 10; 21 ± 1 yr), untrained middle-aged (n = 10; 48 ± 5 yr), and older (n = 10; 65 ± 3 yr) males matched for body surface area. We also studied a group of trained middle-aged males (n = 10; 49 ± 5 yr) matched for body surface area with all groups and for aerobic fitness with the young group. Participants performed intermittent aerobic exercise (30-min exercise bouts separated by 15-min rest) in the heat (40°C and 15% relative humidity) at progressively greater fixed rates of heat production equal to 300 (Ex1), 400 (Ex2), and 500 (Ex3) W. Results showed that HE was significantly lower in middle-aged untrained (Ex2: 426 ± 34; and Ex3: 497 ± 17 W) and older (Ex2: 424 ± 38; and Ex3: 485 ± 44 W) compared with young (Ex2: 472 ± 42; and Ex3: 558 ± 51 W) and middle-aged trained (474 ± 21; Ex3: 552 ± 23 W) males at the end of Ex2 and Ex3 (P < 0.05). No differences among groups were observed during recovery. We conclude that impairments in HE in older and middle-aged untrained males occur at exercise-induced heat loads of ≥400 W when performed in a hot environment. These impairments in untrained middle-aged males can be minimized through regular aerobic exercise training.

Computational estimation of body temperature and sweating in the aged during passive heat exposure

This study discusses the difference in temperature elevation and sweating between younger and older adults during ambient heat exposure. The bioheat equation is solved computationally in an anatomically based human body model to track the variation in the temperature and sweating in the time domain. Our computational code is improved by introducing different blood temperatures in different body regions and taking into account the maximum possible evaporative heat loss. The reduced thermal sensitivity of the hypothalamus in the aged adults (mean age of 73.9 years) is also estimated from literature data and taken into account in a revised formula for the thermoregulatory response. For ambient heat exposure (a temperature of 40 °C and relative humidity of 42%), our computational results are in good agreement with measurement data in the literature for both younger adults (mean age of 23.5 years) and the elderly (67.8 years old), suggesting the effectiveness of our improved bioheat modeling. The reduction in the thermal sensitivity of the hypothalamus is estimated as 0.6 ± 0.2 °C for the aged (mean age of 73.9 years), although it was not significant for the elderly (67.8 years). For an ambient temperature of 35 °C and relative humidity of 60%, the computed core temperature elevation in the model corresponding to the thermophysiological response of the aged is 0.92 °C, which is higher than those for the younger adults, 0.25 °C, and for the elderly, 0.45 °C. This difference in the core temperature elevation is attributable mainly to the decline in the thermal sensitivity of the hypothalamus. The total perspiration at ages of 67.8 years and 73.9 years was 904 g and 645 g, respectively, which is smaller than that of the younger adults, 1090 g.

HSPF 유역모델을 이용한 낙동강유역 실시간 수온 예측

A watershed model was constructed using Hydrological Simulation Program Fortran to predict the water temperature at major tributaries of Nakdong River basin, Korea. Water temperature is one of the most fundamental indices used to determine the nature of an aquatic environment. Most processes of an aquatic environment such as saturation level of dissolved oxygen, the decay rate of organic matter, the growth rate of phytoplankton and zooplankton are affected by temperature. The heat flux to major reservoirs and tributaries was analyzed to simulate water temperature accurately using HSPF model. The annual mean heat flux of solar radiation was estimated to <TEX>$150{\sim}165W/m^2$</TEX>, longwave radiation to <TEX>$-48{\sim}-113W/m^2$</TEX>, evaporative heat loss to <TEX>$-39{\sim}-115W/m^2$</TEX>, sensible heat flux to <TEX>$-13{\sim}-22W/m^2$</TEX>, precipitation heat flux to <TEX>$2{\sim}4W/m^2$</TEX>, bed heat flux to <TEX>$-24{\sim}22W/m^2$</TEX> respectively. The model was calibrated at major reservoir and tributaries for a three-year period (2008 to 2010). The deviation values (Dv) of water temperature ranged from -6.0 to 3.7%, Nash-Sutcliffe efficiency(NSE) of 0.88 to 0.95, root mean square error(RMSE) of <TEX>$1.7{\sim}2.8^{\circ}C$</TEX>. The operational water temperature forecasting results presented in this study were in good agreement with measured data and had a similar accuracy with model calibration results.

The impact of super-absorbent materials on the thermo-physiological properties of textiles

The use of appropriate protective clothing systems in high-risk environments is absolutely essential. Such protective clothing may not provide the desired wearer comfort due to the complexities associated with the system. These constraints are largely due to the multiple layers involved in the protective ensemble. Firefighters’ protective clothing systems, in particular, have limited or no water vapor permeability. This prevents evaporative heat loss and leads to thermal strain and sweat accumulation. This accumulated sweat on the skin and on the internal layer close to the body causes considerable discomfort to the user due to the sensation of wetness. Extensive research has been done to improve the comfort properties of such protective clothing. This research adds yet another dimension where a new inner-layer construction has been developed with high liquid and vapor-absorption capacity that could assist in keeping the moisture and vapor away from the skin and, in addition, retain a dry microclimate close to the skin. The developed materials were tested for their biophysical properties that included tests such as thermal and water vapor resistance, air permeability and moisture management properties. Experimental results in this study indicated that super-absorbent materials, when incorporated into a woven textile material, showed enhanced wearer comfort. It was observed that these super-absorbent materials have the capability to quickly wick the moisture away from the body and, in doing so, have the tendency to keep the skin dry.

Daily regulation of body temperature rhythm in the camel (Camelus dromedarius) exposed to experimental desert conditions.

In the present work, we have studied daily rhythmicity of body temperature (Tb) in Arabian camels challenged with daily heat, combined or not with dehydration. We confirm that Arabian camels use heterothermy to reduce heat gain coupled with evaporative heat loss during the day. Here, we also demonstrate that this mechanism is more complex than previously reported, because it is characterized by a daily alternation (probably of circadian origin) of two periods of poikilothermy and homeothermy. We also show that dehydration induced a decrease in food intake plays a role in this process. Together, these findings highlight that adaptive heterothermy in the Arabian camel varies across the diurnal light–dark cycle and is modulated by timing of daily heat and degrees of water restriction and associated reduction of food intake. The changed phase relationship between the light–dark cycle and the Tb rhythm observed during the dehydration process points to a possible mechanism of internal desynchronization during the process of adaptation to desert environment. During these experimental conditions mimicking the desert environment, it will be possible in the future to determine if induced high‐amplitude ambient temperature (Ta) rhythms are able to compete with the zeitgeber effect of the light–dark cycle.

Increasing Humidity Affects Thermoregulation During Low-Intensity Exercise in Women

Women increasingly occupy manual labor jobs. However, research examining women working under hot-humid conditions is lacking. Therefore, the purpose of our study was to assess how increasing relative humidity (RH) affects women's thermoregulation during low-intensity exercise characteristic of 8 h self-paced manual labor. There were 10 women (age: 23 ± 2 yr; body-surface area: 1.68 ± 0.13 m²; Vo2max: 46 ± 6 ml · kg⁻¹ · min⁻¹) who walked 90 min at 35% Vo2max in 35°C at 55% RH (55RH), 70% RH (70RH), and 85% RH (85RH). Investigators obtained: 1) rectal temperature (Tre), mean-weighted skin temperature (Tsk), and heart rate every 5 min; and 2) respiratory measures every 30 min. Heat production (H) and required rate of evaporative cooling (Ereq) remained constant among trials; each RH increment significantly decreased evaporative heat loss (E), but increased heart rate and sweat rate. All other calorimetric and thermometric variables were similar between 55RH and 70RH, but significantly greater in 85RH. Tre only exceeded 38°C in 85RH after walking ∼80 min. Combined, dry and respiratory heat losses only compensated for <30% of the decreases in E. Women exercising at low intensities in 35°C experienced most statistically significant physiological changes after 70RH. As H and Ereq remained constant across trials, heat storage increased with each 15% rise in RH because dry and respiratory heat losses minimally offset decreased E. Higher Tre, Tsk, and resultantly higher sweat rates reflected heat storage increases as E decreased in each trial. Overall, at 35°C Ta, we found women exercising for 90 min at low intensities remained at safe rectal temperatures up to 70% RH.

Building simulation model of infant-incubator system with decoupling predictive controller

This paper introduces theoretical modelling working on the thermal behavior of the premature infant. This study aims at developing a model useful for the prediction and design of the appropriate controller in objective to reduce evaporative heat loss. A calculation code has been developed to simulate the thermal response of a premature baby to climatic solicitation inside the incubator system. The model allows us to take into consideration radiative, conductive, convective, and evaporative heat transfers inside the incubator system. The air temperature and the humidity rate, which play a salient part in the convective and evaporative exchanges, are calculated by a coupled transfer function. At present, the environmental conditions (temperature and humidity) inside incubator are controlled with a classical Proportional Integral Differential (PID). In this work, we proposed a decoupling Generalized Predictive Controller (DGPC) based on the model described below to achieve an optimal thermal conditions (36.5–37.5) for immature newborn infants (birthweight <1000grams). Real and simulations results prove the feasibility and effectiveness of the proposed model and controller.