Temperature regulation and heat dissipation during flight in birds

1976 ◽  
Vol 65 (2) ◽  
pp. 471-482 ◽  
Author(s):  
J. R. Torre-Bueno
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Skin Temperature ◽  
Core Temperature ◽  
Heat Dissipation ◽  
Sturnus Vulgaris ◽  
The Body ◽  
Ambient Temperatures ◽  
Flow Through ◽  
Animal Skin

Core and skin temperature were measured by radiotelemetry in starlings (Sturnus vulgaris) during 30 min flights in a wind tunnel. Core temperature was independent of ambient temperature from 0 to 28 degrees C. The temporal mean of the monitored core temperature during flight was 42-7 degrees C in one bird and 44-0 degrees C in another. These temperatures are 2-4 degrees C higher than the resting temperature in starlings, and are among the highest steady-state temperatures observed in any animal. Skin temperature on the breast was within a few degrees of core temperature. In some locations skin temperature was higher at low ambient temperatures than at intermediate ambient temperatures. An analysis of the data shows that a high core temperature does not function as an aid to head dissipation. On the contrary, insulation is adjusted to maintain a high temperature, presumably because it is necessary for flight. The increase in skin temperature at low ambient temperatures is believed to be a result of a decrease in heat flow through the breast feathers brought about by feather adjustments, to compensate for an unavoidable increase in heat flow in unfeathered or poorly feathered parts of the body.

scholarly journals Human Machine and Thermoelectric Energy Scavenging for Wearable Devices

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Vladimir Leonov
Keyword(s):  
Thermal Properties ◽  
Heat Flow ◽  
Thermal Resistance ◽  
Wearable Devices ◽  
The Body ◽  
Energy Scavenging ◽  
Wearable Electronics ◽  
Ambient Temperatures ◽  
Thermoelectric Energy ◽  
Temperature Heat

Thermal properties of humans were studied in the case where a small-size energy scavenger is placed on the body. In such a case, the human being serves as a heat source for the thermopile of the scavenger, but the latter serves as a thermally insulating object. As a result, the body properties, namely, the skin temperature, heat flow, and thermal resistance locally change. This is the result of redirection of heat flow inside the body to colder zones because of thermal insulation provided by the scavenger. Increased thermal resistance of human body, in turn, affects the design of the scavenger. The analysis of such scavenger performed for ambient temperatures of 0°C to 25°C shows that it could reach competitive performance characteristics and replace batteries in low-power wearable electronics. A simulated power of up to 60 μW/cm2 at 0°C has been validated by using wearable thermoelectric modules.

Performance Indicators for Steady-State Heat Transfer Through Fin Assemblies

1996 ◽  
Vol 118 (2) ◽  
pp. 310-316 ◽  
Author(s):  
A. S. Wood ◽  
G. E. Tupholme ◽  
M. I. H. Bhatti ◽  
P. J. Heggs
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Heat Flow ◽  
Performance Indicators ◽  
Physical Parameters ◽  
State Heat ◽  
Extended Surface ◽  
Flow Through ◽  
Steady State Heat ◽  
Steady State Heat Transfer

A comparative study is presented of several models describing steady-state heat flow through an assembly consisting of a primary surface (wall) and attached extended surface (fin). Attention is focused on the validity of four performance indicators. The work shows that the augmentation factor is the only indicator capable of correctly predicting the behavioral trends of the rate of heat flow through the assembly as the influencing physical parameters are varied.

scholarly journals Steady-state heat flow through hollow clay bricks

2020 ◽  
Vol 834 ◽  
pp. 012021
Author(s):  
H Ghailane ◽  
M A Ahamat ◽  
M Md Padzi ◽  
S Beddu
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Clay Bricks ◽  
State Heat ◽  
Flow Through ◽  
Steady State Heat

scholarly journals Thermal Bridge Modeling and a Dynamic Analysis Method Using the Analogy of a Steady-State Thermal Bridge Analysis and System Identification Process for Building Energy Simulation: Methodology and Validation

Energies ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 4422
Author(s):  
Heegang Kim ◽  
Myoungsouk Yeo
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Dynamic Analysis ◽  
Building Energy ◽  
Energy Simulation ◽  
Building Energy Simulation ◽  
Analysis Method ◽  
Identification Process ◽  
Thermal Bridge ◽  
Flow Through

It is challenging to apply heat flow through a thermal bridge, which requires the analysis of 2D or 3D heat transfer to building energy simulation (BES). Research on the dynamic analysis of thermal bridges has been underway for many years, but their utilization remains low in BESs. This paper proposes a thermal bridge modeling and a dynamic analysis method that can be easily applied to BESs. The main idea begins with an analogy of the steady-state analysis of thermal bridges. As with steady-state analysis, the proposed method first divides the thermal bridge into a clear wall, where the heat flow is uniform, and the sections that are not the clear wall (the thermal bridge part). For the clear wall part, the method used in existing BESs is applied and analyzed. The thermal bridge part (TB part) is modeled with the linear time-invariant system (LTI system) and the system identification process is performed to find the transfer function. Then, the heat flow is obtained via a linear combination of the two parts. This method is validated by comparing the step, sinusoidal and annual outdoor temperature response of the finite differential method (FDM) simulation. When the thermal bridge was modeled as a third-order model, the root mean square error (RMSE) of annual heat flow with the FDM solution of heat flow through the entire wall was about 0.1 W.

Heat loss responses in rats acclimated to heat loaded intermittently

1990 ◽  
Vol 68 (1) ◽  
pp. 66-70 ◽  
Author(s):  
O. Shido ◽  
T. Nagasaka
Keyword(s):  
Skin Temperature ◽  
Heat Loss ◽  
Core Temperature ◽  
Thermal Conductance ◽  
Heat Acclimation ◽  
The Body ◽  
Body Core Temperature ◽  
Acclimation Temperature ◽  
Hypothalamic Temperature ◽  
Direct Body

The present study examined the heat loss response of heat-acclimated rats to direct body heating with an intraperitoneal heater or to indirect warming by elevating the ambient temperature (Ta). The heat acclimation of the rats was attained through exposure to Ta of 33 or 36 degrees C for 5 h daily during 15 consecutive days. Control rats were kept at Ta of 24 degrees C for the same acclimation period. Heat acclimation lowered the body core temperature at Ta of 24 degrees C, and the core temperature level was lowered as acclimation temperature increased. When heat was applied by direct body heating, the threshold hypothalamic temperature (Thy) for the tail skin vasodilation was also lower in heat-acclimated rats than in the control rats. However, the amount of increase in Thy from the resting level to the threshold was the same in all three groups. When heat was applied by indirect warming, threshold Thy was slightly higher in heat-acclimated than in control rats. The amount of increase in Thy from the resting level to the threshold was significantly greater in heat-acclimated rats. In addition, Ta and the skin temperature at the onset of skin vasodilation were significantly higher in heat-acclimated rats. The results indicate that heat-acclimated rats were less sensitive to the increase in skin temperature in terms of threshold Thy. The gain constant of nonevaporative heat loss response was assessed by plotting total thermal conductance against Thy.(ABSTRACT TRUNCATED AT 250 WORDS)

Thermoregulatory heat production in cold-reared and warm-reared pigs

1983 ◽  
Vol 244 (2) ◽  
pp. R273-R278 ◽  
Author(s):  
M. Heath ◽  
D. L. Ingram
Keyword(s):  
Heat Flow ◽  
Skin Temperature ◽  
Heat Production ◽  
O2 Consumption ◽  
Nonshivering Thermogenesis ◽  
Ambient Temperatures ◽  
Ad Libitum

Pigs were reared from 2 wk of age in either 10 or 35 degrees C and fed ad libitum. At 8 wk of age they were tested for the presence of regulatory nonshivering thermogenesis by administration of norepinephrine (NE) and propranolol. In addition, an electromyogram and carotid temperature, as well as a heat flow and skin temperature from one site, were monitored while the pigs were at ambient temperatures of 10, 15, 20, 25, and 30 degrees C. Cold-reared pigs showed a heightened response to NE in cold compared to thermally neutral environments. This was not observed in warm-reared pigs. Propranolol depressed O2 consumption more in cold-reared than in warm-reared pigs. Pigs reared in the cold also showed a higher intensity of shivering, tissue conductance, and skin temperature than warm-reared littermates. The shivering response of cold-reared pigs was more sensitive to changes in skin temperature than in warm-reared pigs.

SUBCUTANEOUS FAT AND SKIN TEMPERATURE

1954 ◽  
Vol 32 (4) ◽  
pp. 354-358 ◽  
Author(s):  
Jacques LeBlanc
Keyword(s):  
Steady State ◽  
Individual Differences ◽  
Skin Temperature ◽  
Subcutaneous Fat ◽  
The Body ◽  
Regional Variations ◽  
The Individual ◽  
Thermal Steady State

The subcutaneous fat explains to a large extent the individual differences, as well as the regional variations in the skin temperature, observed on the body. The insulation of the fat layer is 0.41 Clo per inch after one hour's exposure at 70° F., 1.18 at 60° F., and 1.96 at 50° F. The significance of these results, with reference to the thermal steady state of the body, is discussed.

Thermoregulatory responses to hyperinsulinemic hypoglycemia and euglycemia in humans

1994 ◽  
Vol 267 (5) ◽  
pp. R1266-R1272 ◽  
Author(s):  
D. G. Maggs ◽  
A. R. Scott ◽  
I. A. MacDonald
Keyword(s):  
Blood Flow ◽  
Skin Temperature ◽  
Core Temperature ◽  
Heat Dissipation ◽  
Human Subjects ◽  
Skin Surface ◽  
Placebo Control ◽  
Hyperinsulinemic Hypoglycemia ◽  
Evaporative Heat Loss ◽  
Healthy Human

Hypoglycemia induces physiological changes that influence thermoregulatory mechanisms. We studied such responses in a group of healthy males (mean age 23.5 yr, body mass index 23.7 kg/m2) during hyperinsulinemic euglycemia (E; 4.5 mmol/l) and hypoglycemia (H; 2.5 mmol/l) and under placebo control conditions (P; saline). Plasma epinephrine (P < 0.0001) and norepinephrine (P < 0.01) levels increased during H and were unchanged during P and E. During H, early increases in metabolic rate (P < 0.05), forearm blood flow (P < 0.01), and sweating (P < 0.01) were followed by a fall in skin temperature (from -1.2 to -2.6 degrees C) and blood flow (P < 0.01). Core temperature fell after 40 min of H and continued to fall thereafter (-0.34 +/- 0.08 degrees C). E and P had minimal effect on skin temperature and blood flow. In summary, in healthy human subjects, H causes a fall in core temperature by heat dissipation at the skin surface through evaporative heat loss and conduction of heat to the periphery, despite an increase in metabolic heat production.

The Effect of Coatings on the Steady-State and Short Time Constriction Resistance for an Arbitrary Axisymmetric Flux

1985 ◽  
Vol 107 (1) ◽  
pp. 33-38 ◽  
Author(s):  
J. R. Dryden ◽  
M. M. Yovanovich ◽  
A. S. Deakin
Keyword(s):  
Thermal Properties ◽  
Steady State ◽  
Heat Flow ◽  
Contact Spot ◽  
One Dimensional ◽  
Constriction Resistance ◽  
Transient Heat Flow ◽  
Flow Through ◽  
Short Time ◽  
Short Times

The effect of a coating upon the short-time and steady-state constriction resistance is analyzed for an arbitrary axisymmetric contact spot flux. At very short times the expression obtained for R is identical to the expression for one-dimensional transient heat flow through a two-layer wall. At steady-state, the results of the analysis predict that the effect of the coating are mainly dependent on the relative thermal properties of the coating and substrate. The limiting cases, where the coating thickness approaches either zero or infinity, are discussed.

Laminate Delamination Due to Thermal Gradients

1995 ◽  
Vol 117 (4) ◽  
pp. 386-390 ◽  
Author(s):  
J. W. Hutchinson ◽  
T. J. Lu
Keyword(s):  
Steady State ◽  
Heat Flow ◽  
Thermal Stresses ◽  
Temperature Gradients ◽  
Thermal Gradients ◽  
Steady State Analysis ◽  
Flow Through ◽  
Laminate Thickness ◽  
Fail Safe ◽  
Delamination Cracks

Flaw-induced delamination of orthotropic laminates subject to through-thickness temperature gradients is analyzed. A crack-like flaw impedes heat flow through the laminate, producing thermal stresses and crack tip stress intensities. The focus is on delamination cracks which propagate under steady-state conditions. The steady-state analysis becomes accurate for a crack whose length is about one laminate thickness. Moreover, the analysis provides realistic fail-safe criteria for excluding delamination.

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