scholarly journals Evaporative cooling and cutaneous surface temperature of Holstein cows in tropical conditions

2011 ◽  
Vol 40 (5) ◽  
pp. 1143-1147 ◽  
Author(s):  
Roberto Gomes da Silva ◽  
Alex Sandro Campos Maia
Keyword(s):  
Heat Loss ◽  
Coat Colour ◽  
Holstein Cows ◽  
Coefficient Of Determination ◽  
Evaporative Heat Loss ◽  
Exponential Relationship ◽  
Body Regions ◽  
Tropical Conditions ◽  
Three Body ◽  
Cutaneous Evaporation

The effects of skin temperature (T S) on the rate of heat loss by cutaneous evaporation (E S) in Holstein cows chronically exposed to sun, considering hair coat colour were studied. Sixteen purebred cows were measured for E S and T S at 01:00 p.m. after 6 hours of exposure to sun, on three body regions (flank, neck and gluteus) and considering dark and white spots separately. Sweating rate (S) and E S were measured by means of a ventilated capsule. Black skin areas presented mean S (138.9 ± 8.5 gm-2 h-1), E S (93.3 ± 5.7 Wm-2), and T S (33.1 ± 0.2°C) higher than those in the white areas (109.5 ± 9.7 gm-2h-1), 73.6 ± 6.5 Wm-2 and 32.6 ± 0.2°C, respectively). There is an exponential relationship among cutaneous temperature and cutaneous evaporation, which can be represented by the equation: E S = 31.5 + exp{(T S - 27.9)/2.19115}, with coefficient of determination r² = 0.68. Cutaneous evaporative heat loss remains almost constant around 48 Wm-2 until T S reaches nearly 31°C.

Thermal sweating in different body regions of sheep

1979 ◽  
Vol 92 (2) ◽  
pp. 511-512 ◽  
Author(s):  
A. K. Rai ◽  
B. S. Mehta ◽  
M. Singh
Keyword(s):  
Thermal Stress ◽  
Ambient Temperature ◽  
Heat Loss ◽  
Evaporative Cooling ◽  
Sweat Glands ◽  
Evaporative Heat Loss ◽  
Body Regions ◽  
Time Period ◽  
Sweat Production ◽  
Thermal Sweating

Although sheep combat thermal stress mainly by panting, a sizeable amount (40%) of total evaporative heat loss, is from sources other than panting (Hales & Brown, 1974). The frequency of sporadic discharge of sweat glands increases with increase in ambient temperature and is accompanied by a decline in respiration rate (Bligh, 1961). The wool coat can reduce evaporative cooling but sweating may have cooling value in sheep breeds with open fleeces (Rai, Singh & More, 1978). In sheep, the number and size of the sweat glands (Waites & Voglmayr, 1962) and the quantum of sweat production in a particular time period (Ghoshal et al. 1977) varies in different body regions. In view of the possible significance of surface evaporative cooling, thermal sweating in different body regions of sheep was investigated.

The effect of garment combinations on thermal comfort of office clothing

2019 ◽  
Vol 89 (21-22) ◽  
pp. 4425-4437 ◽  
Author(s):  
Hande G Atasağun ◽  
Ayşe Okur ◽  
Agnes Psikuta ◽  
René M Rossi ◽  
Simon Annaheim
Keyword(s):  
Thermal Comfort ◽  
Heat Loss ◽  
Heat Dissipation ◽  
Moisture Transfer ◽  
The Body ◽  
Raw Material ◽  
Upper Body ◽  
Thermal Manikin ◽  
Evaporative Heat Loss ◽  
Body Regions

Clothing and the enclosed air layers highly affect heat dissipation from the body and thus, are crucial factors when it comes to thermal comfort. The heat and moisture transfer is affected by the variation of the size and the shape of air gaps between the garment and the human body. In addition, the fabric and garment design properties can affect the amount of heat loss from different body parts. In this study, we investigated the effect of fabric properties (different raw materials and weave types) and the garment fit on the heat loss through the garment combinations (undershirt and shirt) for the different parts of the upper body (trunk, chest, and back) using a sweating thermal manikin. The undershirt fit and the raw material of the shirts showed strong effects on the dry thermal resistance of the garment combinations. Moreover, the undershirt properties affected the evaporative heat loss from garment combinations, and the magnitude of these effects varied over different body regions. Whilst the undershirt fit had a significant impact on the evaporative heat loss of the back region, the influence of the undershirt raw material was more important in the chest region. The findings of this study provide fundamental knowledge to improve the thermal comfort of garment combinations for office wear.

scholarly journals Latent heat loss of Holstein cows in a tropical environment: a prediction model

2008 ◽  
Vol 37 (10) ◽  
pp. 1837-1843 ◽  
Author(s):  
Alex Sandro Campos Maia ◽  
Roberto Gomes da Silva ◽  
Cintia Maria Battiston Loureiro
Keyword(s):  
Heat Loss ◽  
Latent Heat ◽  
Air Temperature ◽  
Holstein Cows ◽  
Tropical Region ◽  
Weight Class ◽  
Air Temperatures ◽  
Latent Heat Loss ◽  
Cutaneous Evaporation ◽  
Respiratory Evaporation

Nine lactating Holstein cows with average 526 ± 5 kg of BW, five predominantly black and four predominantly white, bred in a tropical region and managed in open pasture were observed to measure cutaneous and respiratory evaporation rates under different environmental conditions. Cows were separated in three weight class: 1 (<450 kg), 2 (450-500 kg) and 3 (>500 kg). Latent heat loss from cutaneous surface was measured using a ventilated capsule; evaporation in the respiratory system was measured using a facial mask. The results showed that heaviest cows (2 and 3 classes) presented the least evaporation rates. When air temperature increased from 10 to 36ºC the relative humidity decreased from 90 to 30%. In these conditions the heat loss by respiratory evaporation increased from 5 to 57 Wm-2, while the heat loss by cutaneous evaporation increased from 30 to 350 Wm-2. The results confirm that latent heat loss was the main way of thermal energy elimination under high air temperatures (>30ºC); cutaneous evaporation was the main mechanism of heat loss, responding for about 85% of the heat loss. A model was presented for the prediction of the latent heat loss that was based on physiological and environmental variables and could be used to estimate the contribution of evaporation to thermoregulation; a second, based on air temperature only, should be used to make a simple characterization of the evaporation process.

Cutaneous Water Loss at Rest and Exercise in Two Species of Marsupials

1983 ◽  
Vol 31 (1) ◽  
pp. 93 ◽  
Author(s):  
CJ Bell ◽  
RV Baudinette ◽  
SC Nicol
Keyword(s):  
Heat Loss ◽  
Brushtail Possum ◽  
Evaporative Heat Loss ◽  
Tasmanian Devil ◽  
Ambient Temperatures ◽  
Marsupial Species ◽  
Gland Function ◽  
A Minor ◽  
Cutaneous Evaporation ◽  
And Function

The relative roles of heat storage, evaporative, and non-evaporative heat loss were examined in the brushtail possum, Trichosurus vulpecula, and the Tasmanian devil, Sarcophilus harrisii, during exercise. Rates of water conductance across the skin were also measured at rest and while running at two ambient temperatures. Evaporative heat loss from the general body surface in S. harrisii is a minor contribution to the overall heat balance, and sweat gland function is not apparent. T. vulpecula relies more on heat loss mediated by cutaneous evaporation than from respiratory routes, but changes in cutaneous blood flow are more important than glandular activity in augmenting this response. These results and earlier reports in the literature suggest that the occurrence and function of cutaneous evaporation varies among marsupial species.

Changes in serotonin contents in brain affect metabolic heat production of rabbits in cold

1978 ◽  
Vol 235 (1) ◽  
pp. R41-R47
Author(s):  
M. T. Lin ◽  
I. H. Pang ◽  
S. I. Chern ◽  
W. Y. Chia
Keyword(s):  
Blood Flow ◽  
Amino Acid ◽  
Heat Loss ◽  
Acid Decarboxylase ◽  
Evaporative Heat Loss ◽  
Decarboxylase Inhibitor ◽  
Ambient Temperatures ◽  
Amino Acid Decarboxylase ◽  
Metabolic Heat ◽  
Normal Limits

Elevating serotonin (5-HT) contents in brain with 5-hydroxytryptophan (5-HTP) reduced rectal temperature (Tre) in rabbits after peripheral decarboxylase inhibition with the aromatic-L-amino-acid decarboxylase inhibitor R04-4602 at two ambient temperatures (Ta), 2 and 22 degrees C. The hypothermia was brought about by both an increase in respiratory evaporative heat loss (Eres) and a decrease in metabolic rate (MR) in the cold. At a Ta of 22 degrees C, the hypothermia was achieved solely due to an increase in heat loss. Depleting brain contents of 5-HT with intraventricular, 5,7-dihydroxytryptamine (5,7-DHT) produced an increased Eres and ear blood flow even at Ta of 2 degrees C. Also, MR increased at all but the Ta of 32 degrees C. However, depleting the central and peripheral contents of 5-HT with p-chlorophenylalanine (pCPA) produced lower MR accompanied by lower Eres in the cold compared to the untreated control. Both groups of pCPA-treated and 5,7-DHT-treated animals maintained their Tre within normal limits. The data suggest that changes in 5-HT content in brain affects the MR of rabbits in the cold. Elevating brain content of 5-HT tends to depress the MR response to cold, while depleting brain content of 5-HT tends to enhance the MR response to cold.

Evaporative Heat Loss Mechanisms of the Newborn Calf, Bos Taurus

1968 ◽  
Vol 124 (2) ◽  
pp. 83-88 ◽  
Author(s):  
J.R.S. Hales ◽  
J.D. Findlay ◽  
D. Robertshaw
Keyword(s):  
Heat Loss ◽  
Bos Taurus ◽  
Evaporative Heat Loss ◽  
Loss Mechanisms

Thermoregulation during rest and exercise in different postures in a hot humid environment

1980 ◽  
Vol 48 (6) ◽  
pp. 999-1007 ◽  
Author(s):  
K. Kabayashi ◽  
S. M. Horvath ◽  
F. J. Diaz ◽  
D. R. Bransford ◽  
B. L. Drinkwater
Keyword(s):  
Time Course ◽  
Work Load ◽  
Skin Surface ◽  
Bicycle Ergometer ◽  
Whole Body ◽  
Evaporative Heat Loss ◽  
Humid Environment ◽  
Supine Posture ◽  
Three Body ◽  
Rest And Exercise

The time course of whole-body sweating and thermal regulation during rest and exercise in a hot humid environment was investigated in three body postures. After 45 min rest in the upright, low-sit, or supine posture, five unacclimatized men exercised for 45 min on a bicycle ergometer in the same posture in an environment of 49.5 degrees C, 28.9 Torr. Exercise was performed at two different work loads, corresponding to about 30 and 45% of VO2max. During exercise auditory canal temperature, rectal temperature, and mean skin temperature increased linearly being highest in the supine and lowest in the upright posture. Percentage of evaporated sweat from the skin to secreted sweat was 65% in upright, 52% in the low-sit, and only 46% in the supine posture during the last 20 min of exercise regardless of work load. The time course of the rate of body heat storage was different from predictions based on the thermal balance equation. Evaporative heat loss was not 100% effective in cooling the skin surface.

Effects of environmental temperature and humidity on evaporative heat loss through firefighter suit materials made with semi-permeable and microporous moisture barriers

2021 ◽  
pp. 004051752110265
Author(s):  
Huipu Gao ◽  
Anthoney Shawn Deaton ◽  
Xiaomeng Fang ◽  
Kyle Watson ◽  
Emiel A DenHartog ◽  
...  
Keyword(s):  
Heat Loss ◽  
Environmental Temperature ◽  
Moisture Absorption ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Evaporative Resistance ◽  
Environmental Testing ◽  
Permeable Barrier ◽  
Moisture Condensation ◽  
Moisture Barriers

The goal of this research was to understand how firefighter protective suits perform in different operational environments. This study used a sweating guarded hotplate to examine the effect of environmental temperature (20–45°C) and relative humidity (25–85% RH) on evaporative heat loss through firefighter turnout materials. Four firefighter turnout composites containing three different bi-component (semi-permeable) and one microporous moisture barriers were selected. The results showed that the evaporative resistance of microporous moisture barrier systems was independent of environmental testing conditions. However, absorbed moisture strongly affected evaporative heat loss through semi-permeable moisture barriers coated with a layer of nonporous hydrophilic polymer. Moisture absorption in mild environment (20–25°C) tests, or when testing at high humidity (>85% RH), significantly increased water vapor transmission in semi-permeable turnout systems. It was also found that environmental conditions used in the total heat loss (THL) test (25°C and 65% RH) produced moisture condensation in bi-component barrier systems, making them appear more breathable than could be expected when worn in hotter environments. Regression models successfully qualified the relationships between moisture uptake levels in semi-permeable barrier systems and evaporative resistance and THL. These findings reveal the limitations in relying on THL, the heat strain index currently called for by the NFPA 1971 Standard for Structural Firefighter personal protective equipment, and supports the need to measure turnout evaporative resistance at 35°C (Ret), in addition to THL at 25°C.

Respiratory water and heat loss of the black duck during flight at different ambient temperatures

1971 ◽  
Vol 49 (5) ◽  
pp. 767-774 ◽  
Author(s):  
M. Berger ◽  
J. S. Hart ◽  
O. Z. Roy
Keyword(s):  
Heat Loss ◽  
Water Loss ◽  
Pulmonary Ventilation ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Ambient Temperatures ◽  
Black Duck ◽  
Respiratory Heat Loss ◽  
Metabolic Water ◽  
Expired Air

Pulmonary ventilation and temperature of expired air and of the respiratory passages has been measured by telemetry during flight in the black duck (Anas rubripes) and the respiratory water and heat loss has been calculated.During flight, temperature of expired air was higher than at rest and decreased with decreasing ambient temperatures. Accordingly, respiratory water loss as well as evaporative heat loss decreased at low ambient temperatures, whereas heat loss by warming of the inspired air increased. The data indicated respiratory water loss exceeded metabolic water production except at very low ambient temperatures. In the range between −16 °C to +19 °C, the total respiratory heat loss was fairly constant and amounted to 19% of the heat production. Evidence for the independence of total heat loss and production from changes in ambient temperature during flight is discussed.

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