scholarly journals Heat loss from deer mice (Peromyscus): evaluation of seasonal limits to thermoregulation

1986 ◽  
Vol 126 (1) ◽  
pp. 249-269 ◽  
Author(s):  
K. E. Conley ◽  
W. P. Porter
Keyword(s):  
Heat Transfer ◽  
Heat Loss ◽  
Heat Production ◽  
Mechanistic Model ◽  
Production Capacity ◽  
Deer Mice ◽  
Clear Night ◽  
Winter Conditions ◽  
Seasonal Adaptations ◽  
Air Temperatures

This paper investigates the influence of seasonal adaptations to thermoregulatory heat loss for deer mice (Peromyscus) during summer and winter. A general, mechanistic model of heat transfer through fur was evaluated for the structural properties of the fur of deer mice. The model was validated against heat production determined from mice exposed to a range of radiative (wall) temperatures (tr) at air temperatures (ta) of 15, 27 and 34 degrees C. Calculated heat loss from the appendages was subtracted from the measured heat production to yield heat loss from the furred torso. This calculated torso heat loss agreed closely with the predicted fur heat loss for all conditions, as shown by a regression slope near 1 (0.99). Simulations using models of fur and appendage heat loss reveal that the winter increase in thermogenic (heat production) capacity has a greater effect than changes in fur properties in expanding the limits to thermoregulation. Both wind and a clear night sky increase heat loss and can limit thermoregulation to air temperatures above those found in deer mice habitats during winter (−25 degrees C). Thus, despite seasonal adaptations, these simulations indicate that thermoregulation is not possible under certain winter conditions, thereby restricting deer mice to within the protected environment of the leaf litter or snow tunnels.

Skinfolds and resting heat loss in cold air and water: temperature equivalence

1975 ◽  
Vol 39 (1) ◽  
pp. 93-102 ◽  
Author(s):  
R. M. Smith ◽  
J. M. Hanna
Keyword(s):  
Heat Transfer ◽  
Water Temperature ◽  
Heat Loss ◽  
Air Temperature ◽  
Indirect Calorimetry ◽  
Cold Water ◽  
Heat Conductance ◽  
Air Temperatures ◽  
Body Core ◽  
Male Subjects

Fourteen male subjects with unweighted mean skinfolds (MSF) of 10.23 mm underwent several 3-h exposures to cold water and air of similar velocities in order to compare by indirect calorimetry the rate of heat loss in water and air. Measurements of heat loss (excluding the head) at each air temperature (Ta = 25, 20, 10 degrees C) and water temperature (Tw = 29–33 degrees C) were used in a linear approximation of overall heat transfer from body core (Tre) to air or water. We found the lower critical air and water temperatures to fall as a negative linear function of MSF. The slope of these lines was not significantly different in air and water with a mean of minus 0.237 degrees C/mm MSF. Overall heat conductance was 3.34 times greater in water. However, this value was not fixed but varied as an inverse curvilinear function of MSF. Thus, equivalent water-air temperatures also varied as a function of MSF. Between limits of 100–250% of resting heat loss the followingrelationships between MSF and equivalent water-air temperatures were found (see article).

Energy exchanges of veal calves in relation to body weight, food intake and air temperature

1976 ◽  
Vol 23 (1) ◽  
pp. 35-42 ◽  
Author(s):  
A. J. F. Webster ◽  
J. G. Gordon ◽  
J. S. Smith
Keyword(s):  
Body Weight ◽  
Heat Loss ◽  
Heat Production ◽  
Live Weight ◽  
Milk Replacer ◽  
Total Heat Loss ◽  
Direct Calorimetry ◽  
Veal Calves ◽  
Air Temperatures ◽  
Energy Retention

SUMMARY1. Two series of energy balance trials were conducted with British Friesian veal calves. In the first, calves were given a milk replacer diet at three different planes of nutrition. In the second, calves were raised from about 80 to 180 kg at four air temperatures, 5°, 10°, 15° and 20°.2. The net efficiency of utilization of the milk replacer diet for growth was 0·72. The effect of body size on heat production in growing calves was best expressed by an exponent of body weight slightly but not significantly below W0·75.3. Measurements of heat production estimated from respiratory exchange and heat loss measured by direct calorimetry agreed exactly at all planes of nutrition. Heat production at zero energy retention was 675 kJ/kg W0·75 per 24 hr.4. Average daily live-weight gain and total heat loss were the same at all air temperatures. Changes during growth in the partition of heat loss into its sensible and evaporative components indicated that calves acclimated progressively to the air temperatures to which they were exposed.

Influence of air humidity on the partition of heat exchanges of cattle

1972 ◽  
Vol 78 (2) ◽  
pp. 303-307 ◽  
Author(s):  
J. A. McLean ◽  
D. T. Calvert
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Air Temperature ◽  
Heat Production ◽  
Total Heat ◽  
Evaporative Heat Loss ◽  
Air Humidity ◽  
Total Heat Loss ◽  
Air Temperatures ◽  
Heat Exchanges

SUMMARYThe balance between heat production and heat loss and the partition of heat exchanges of cattle in relation to air humidity has been studied at two different air temperatures using a direct (gradient-layer) calorimeter.Increasing humidity at 35 °C air temperature caused no significant change in heat production or in the level of total heat loss finally attained, but body temperature and respiratory activity were both increased.Increasing humidity at 15 °C air temperature caused a small reduction in heat loss by evaporation but had no effect on sensible heat loss, body temperature or respiratory frequency.Heat loss by evaporation amounted to 18% of the total heat loss at 15 °C and to 84% at 35 °C.Heat loss by respiratory evaporation amounted to 54% of the total evaporative heat loss at 15 °C and to 38% at 35 °C.

Heat Loss and the Body Temperatures of Flying Insects

1960 ◽  
Vol 37 (1) ◽  
pp. 171-185
Author(s):  
NORMAN STANLEY CHURCH
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Water Loss ◽  
Schistocerca Gregaria ◽  
The Body ◽  
Body Temperatures ◽  
Dry Air ◽  
Flying Insects ◽  
Air Temperatures ◽  
Temperature Excess

1. Comparative measurements of body temperatures and water loss in Schistocerca gregaria showed that evaporation dissipates relatively little of the heat generated by the wing muscles during flight. 2. In perfectly dry air at 30° C, evaporation reduces the temperature excess of the pterothorax by less than 10%, or about 0.5° C. Even at 40° C, which is the highest temperature that will permit continuing flight, the reduction is only about 20%, or 1.2° C, in dry air. 3. A flying locust has no special mechanism, except cessation of flight, to protect it from overheating. Breathing is not markedly increased at high temperatures, nor is the rate of heat production reduced. 4. Very little heat is dissipated from the pterothorax by evaporation through the cuticle. The cuticle becomes permeable enough to allow substantial cooling only at temperatures well above the highest that permit flight. 5. Temperature measurements in Triphaena pronuba and Bombus lapidarius supported the idea that evaporative cooling during flight is not much more important in other well-waterproofed insects. Large changes in the humidity produced changes of less than 1° C. in the temperature excess, even at the highest air temperatures at which the insects could fly. 6. The reactions of the insects to moist and dry air are adapted to the conservation of their water rather than to rapid cooling.

Applied Heat Transfer in the Development of the New Wind Chill Temperature Chart

2004 ◽  
Author(s):  
Maurice Bluestein
Keyword(s):  
Heat Transfer ◽  
Air Temperature ◽  
The United States ◽  
Wind Chill ◽  
Wind Speeds ◽  
Clear Night ◽  
Air Temperatures ◽  
Tissue Resistance ◽  
The U.S

In November, 2001, the national weather services of the United States and Canada, recognizing inaccuracies in the original, adopted a revised Wind Chill Temperature (WCT) chart. This revision was developed by the authors under a mandate from a joint action group for temperature indicies (JAG/TI) formed by the U.S. Office of the Federal Coordinator for Meteorology. This new chart provides, for a given air temperature and recorded wind speed, that air temperature, the WCT, which would result in the same rate of heat loss from exposed human skin in still air. Values of the WCT are given for a range of air temperatures from −45°F to 40°F and a range of wind speeds from 5 mph to 60 mph. For Canada, the ranges are from −50°C to 10°C and 10 km/hr to 80 km/hr. The new chart was developed using principles of heat transfer, including conduction, forced convection and radiation. Skin tissue resistance was obtained from human studies. This paper describes the application of these principles and will show how these same principles have been used to demonstrate the errors in the original chart developed over 60 years ago by our military in Antarctica and adopted by the U.S. Weather Service in 1973. As was the case for the original chart, a clear night sky has been assumed, thus ignoring any direct solar radiation that would otherwise tend to elevate the WCT. The new chart is unlikely to be the final version long term and this paper will also discuss possible future modifications.

Accidental Hypothermia

PEDIATRICS ◽  
1979 ◽  
Vol 63 (6) ◽  
pp. 926-928
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Weather Conditions ◽  
Accidental Hypothermia ◽  
Good Judgment ◽  
Hand Coordination ◽  
Body Heat ◽  
Unfavorable Weather

Pediatricians may be able to bring the dangers of accidental hypothermia to the attention of their patients at the time of a sports, camp, or college "physical." People who spend time outdoors must learn to recognize hypothermia-producing weather and water; to know that shivering indicates heat loss exceeding available insulation and body heat production; and to understand that loss of good judgment and hand coordination soon follow uncontrollable shivering. They must not go into areas in which, without proper gear, unfavorable weather conditions or dangerous water may develop, and they must understand that most tragedies from cold result from failure to make camp or to return to safety when weather conditions become unfavorable.

External work in level and grade walking on a motor-driven treadmill

1960 ◽  
Vol 15 (5) ◽  
pp. 759-763 ◽  
Author(s):  
J. W. Snellen
Keyword(s):  
Heat Loss ◽  
Heat Production ◽  
Total Energy Expenditure ◽  
The Body ◽  
External Work ◽  
Thermal Exchange ◽  
Level Walking ◽  
The Subject ◽  
Set Up ◽  
Physical Laws

When studying a walking subject's thermal exchange with the environment, it is essential to know whether in level walking any part of the total energy expenditure is converted into external mechanical work and whether in grade walking the amount of the external work is predictable from physical laws. For this purpose an experiment was set up in which a subject walked on a motor-driven treadmill in a climatic room. In each series of measurements a subject walked uphill for 3 hours and on the level for another hour. Metabolism was kept equal in both situations. Air and wall temperatures were adjusted to the observed weighted skin temperature in order to avoid any heat exchange by radiation and convection. Heat loss by evaporation was derived from the weight loss of the subject. All measurements were carried out in a state of thermal equilibrium. In grade walking there was a difference between heat production and heat loss by evaporation. This difference equaled the caloric equivalent of the product of body weight and gained height. In level walking the heat production equaled heat loss. Hence it was concluded that in level walking all the energy is converted into heat inside the body. Submitted on April 26, 1960

Physical fitness and thermoregulatory reactions in a cold environment in men

1988 ◽  
Vol 65 (5) ◽  
pp. 1984-1989 ◽  
Author(s):  
J. H. Bittel ◽  
C. Nonotte-Varly ◽  
G. H. Livecchi-Gonnot ◽  
G. L. Savourey ◽  
A. M. Hanniquet
Keyword(s):  
Physical Fitness ◽  
Cold Stress ◽  
Heat Production ◽  
Ambient Air ◽  
Metabolic Heat Production ◽  
Adult Males ◽  
Fitness Level ◽  
Metabolic Heat ◽  
Air Temperatures ◽  
Thermoregulatory Reactions

The relationship between the physical fitness level (maximal O2 consumption, VO2max) and thermoregulatory reactions was studied in 17 adult males submitted to an acute cold exposure. Standard cold tests were performed in nude subjects, lying for 2 h in a climatic chamber at three ambient air temperatures (10, 5, and 1 degrees C). The level of physical fitness conditioned the intensity of thermoregulatory reactions to cold. For all subjects, there was a direct relationship between physical fitness and 1) metabolic heat production, 2) level of mean skin temperature (Tsk), 3) level of skin conductance, and 4) level of Tsk at the onset of shivering. The predominance of thermogenic or insulative reactions depended on the intensity of the cold stress: insulative reactions were preferential at 10 degrees C, or even at 5 degrees C, whereas colder ambient temperature (1 degree C) triggered metabolic heat production abilities, which were closely related to the subject's physical fitness level. Fit subjects have more efficient thermoregulatory abilities against cold stress than unfit subjects, certainly because of an improved sensitivity of the thermoregulatory system.

THE COEFFICIENT OF HEAT TRANSFER FOR VERTICAL SURFACES IN STILL AIR

1937 ◽  
Vol 15a (7) ◽  
pp. 109-117
Author(s):  
R. Ruedy
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Heat Loss ◽  
Temperature Difference ◽  
Plane Surface ◽  
Vertical Plane ◽  
Black Body ◽  
Average Temperature ◽  
Fourth Root

For a vertical plane surface in still air the coefficient of heat transfer, valid within the range of temperatures occurring in buildings, depends on the temperature and the height of the surface. If black body conditions are assumed for the heat lost by radiation, the coefficient is equal to 1.39, 1.50, 1.62, and 1.73 B.t.u. per sq. ft. per ° F. at 32°, 50°, 68°, and 86° F. respectively, the height of the heated surfaces being 100 cm. Convection is responsible for about one-third, and radiation, mainly in the region of 10 microns, for about two-thirds of the heat loss. Convection currents depend on the temperature difference, while radiation depends on the average temperature. When attempts are made to stop convection currents by placing obstacles across the surface, the loss of heat due to natural convection varies inversely as the fourth root of the height, providing that the nature of the flow of air remains unchanged.

Development of a Heat Transfer Coefficient Model via Experimental Validation

2008 ◽  
Vol 3 (1) ◽  
Author(s):  
Adel A. Al-Hemiri ◽  
Nada Sadoon Ahmedzeki
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Standard Deviation ◽  
Transfer Coefficient ◽  
Bubble Column ◽  
Mechanistic Model ◽  
Bubble Column Reactor ◽  
Ann Model ◽  
Liquid Bubble ◽  
The Heat Transfer Coefficient

Knowledge of the heat transfer coefficient is an essential prerequisite for any industrial gas/liquid bubble column reactor design. In this paper, experiments were carried out in a laboratory scale bubble column using air–water and 10wt% glycerin–air solution systems. Experimental values of the heat transfer coefficient were compared with some of the previous published correlations and were also compared with the model predicted by ANN in our previous work (Ahmedzeki, 2007). The ANN model was found to be better than all previous published correlations. %AARE was 8.2 and %standard deviation was 7.85. A mechanistic model was also developed to analyze the system. The resulting correlation was a %AARE of 17.5 and %standard deviation of 15. Both the above models and the experimental results compared well with the previous published correlations.

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