scholarly journals Mechanisms of Body-Temperature Regulation in Honeybees, Apis Mellifera: II. Regulation of Thoracic Temperature at High Air Temperatures

1980 ◽  
Vol 85 (1) ◽  
pp. 73-87
Author(s):  
BERND HEINRICH
Keyword(s):  
Heat Transfer ◽  
Body Temperature Regulation ◽  
Free Flight ◽  
Anterior Portion ◽  
Lethal Temperatures ◽  
Primary Mechanism ◽  
Thoracic Temperature ◽  
Air Temperatures ◽  
A Minor ◽  
Production Mechanisms

1. Honeybees could remain in continuous free flight at extremely high air temperatures (up to at least 46 °C). 2. The metabolic rate in free flight, 80–85 ml O2g body weight−1 h−1, was independent of air temperature (TA) over a span of at least 22 °C. 3. The bees' ability to fly at high TA was due to their ability to maintain thoracic temperature (TTh) near TA despite prodigious rates of heat production. Mechanisms of preventing TTh from overheating at high TA were investigated. 4. Bees in flight at high TA regurgitated fluid from their honeycrop and large droplets sometimes spread over the anterior portion of the thorax. 5. Bees without the first two sets of legs, or without a ‘tongue’, maintained as low TH and TTh as intact bees. 6. The abdomen serves only a minor function as a heat exchanger. In tethered bees, heating of the thorax to 45–50 °C resulted in significant, yet relatively little, temperature increase of the abdomen above that of dead or non heat-stressed animals. Similarly, in free flight abdominal temperatures (TAb) were close to TA at all TA. 7. Thoracic heating to near lethal temperatures did not result in droplet extrusion from the mouth nor in significant physiologically facilitated heat transfer to the head. Furthermore, it resulted in no, or in relatively small, changes in pulsation of the aorta and the heart. 8. However, the bees prevented the head from overheating, and the head served as a heat sink for excess heat from the thorax. Keeping TH < TA resulted in keeping TTh near TA. 9. It is concluded that during flight at high TA regulation of TH by evaporative cooling is the primary mechanism of reducing TTh.

scholarly journals Heat Transfer in Dragonflies: ‘Fliers’ and ‘Perchers’

1978 ◽  
Vol 74 (1) ◽  
pp. 17-36 ◽  
Author(s):  
BERND HEINRICH ◽  
TIMOTHY M. CASEY
Keyword(s):  
Heat Transfer ◽  
Heat Input ◽  
Blood Circulation ◽  
Behavioural Thermoregulation ◽  
Direct Sunlight ◽  
Experimental Conditions ◽  
Anterior Portion ◽  
Warm Up ◽  
Anax Junius ◽  
Air Temperatures

1. Both ‘perchers’ (Libellula saturata) and ‘fliers’ (Anax junius and Aeshna multicolor) remained active in the field in sunshine at air temperatures from at least 24 °C to 36 °C. 2. The percher basked at low air temperatures and regulated exogenous heat input by postural adjustments. It markedly reduced flight activity at high air temperatures but flew nearly continuously at intermediate temperatures. 3. In direct sunlight, the abdomen of L. saturata heated faster than the thorax, but this percher exhibited little or no capacity to transfer heat between abdomen and thorax. 4. In contrast, the fliers gave no evidence of behavioural thermoregulation, but both showed impressive capacities for heat transfer from thorax to abdomen. 5. When heated exogenously on the thorax the temperature of the entire abdomen of both fliers increased uniformly, but with endogenous heat production during pre-flight warm-up there was only a slight temperature increase near the anterior portion of the abdomen. 6. Removal of abdominal air sacs or immobilizing the abdomen with wax to prevent all abdominal pumping did not significantly alter the capacity to transfer heat from thorax to abdomen. 7. Ligation of the heart anywhere along the length of the abdomen abolished heat transfer. Given sufficient exogenous heat input, fliers that can regulate their thoracic temperature by transferring the excess heat to the abdomen died in about 2 min due to overheating when the heart was occluded. Under our experimental conditions the fliers appeared to thermoregulate exclusively via a control of blood circulation.

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).

scholarly journals A New Test Facility for Testing of Cooled Gasturbine Components

1998 ◽  
Author(s):  
Ulf R. Rådeklint ◽  
Christer S. Hjalmarsson
Keyword(s):  
Heat Transfer ◽  
Gas Turbine ◽  
Temperature Fields ◽  
Test Facility ◽  
Operating Point ◽  
Ir Camera ◽  
Turbine Cooling ◽  
Air Temperatures ◽  
Turbine Vanes ◽  
Conventional Instrumentation

A high pressure hot test facility for cooled gas turbine components has been developed for use in turbine cooling research. In this facility, heat transfer tests for a sector of real turbine vanes can be performed under continuous operation. The heat transfer tests are performed at an operating point that is scaled down from the real engine operating point. The compressor can deliver air at the rate of up to 10 kg/s at 20 bars. Air temperatures of up to 1170 K can be achieved by using an oil-fired combustor. Besides conventional instrumentation such as thermocouples and pressure probes, the facility is equipped with an IR-camera to map two-dimensional wall temperature fields. Hot wire anemometry and an LDV system are used to determine mean and fluctuating velocity components. This paper describes design and performance of the test facility as well as the control and measurement equipment. The test and evaluation procedures used for testing of cooled gas turbine vanes are also presented.

Energy Efficient Refrigerators: The Effect of Door Gasket and Wall Insulation on Heat Transfer

2003 ◽  
Author(s):  
Mir-Akbar Hessami ◽  
Arnd Hilligweg
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Energy Efficiency ◽  
Power Consumption ◽  
Thermal Efficiency ◽  
Air Temperatures ◽  
Insulation Thickness ◽  
Two Stages ◽  
Experimental Rig ◽  
The Doors

The energy efficiency of refrigerators not only depends on the efficiency of the various components used in the cycle but also on their thermodynamics cycle efficiency as well the thermal efficiency of the cabinet housing the components. Efficiency improvements to the thermodynamics cycle and refrigerator components have been the subject of various papers published in the open literature. Not many researchers have looked at reducing the heat leakage into the refrigerator cabinet with the explicit objective of reducing the power consumption of the unit and hence improving its thermal efficiency. This paper is based on an experimental study of this topic, and includes information on the experimental rig used and the results obtained. This research was performed in two stages: The first stage was focused on improving the energy efficiency by changing wall insulation while the second stage was to study the heat transfer through the doors’ gaskets. For the first part, a domestic refrigerator was instrumented with many thermocouples and heat flux meters to measure the inside and outside air temperatures and the heat transfer through the wall of the unit, respectively. These measurements were taken under different environmental conditions as well as different insulation thickness in the walls of the cabinet. For the second part, using a specially designed and manufactured experimental rig, various door gaskets were placed between a warm and a cold chamber and heat transfer through the gasket was measured. The results showed that by adding 30 mm polystyrene insulation to the walls of the refrigerator, the heat transfer through the walls reduced by around 35%. The power consumption data agreed very well with the measured heat flux through the walls. The percentage heat transfer through the doors’ gaskets was confirmed to be about 13% of the total heat transferred into the unit.

scholarly journals A Heat-Balance Study on Sørbreen, Jan Mayen

1965 ◽  
Vol 5 (42) ◽  
pp. 793-803
Author(s):  
P. C. Dibben
Keyword(s):  
Heat Transfer ◽  
Heat Balance ◽  
Summer Rainfall ◽  
Weather Conditions ◽  
Meteorological Station ◽  
Sensible Heat ◽  
Balance Study ◽  
Statistical Comparison ◽  
Air Temperatures ◽  
Frontal Activity

AbstractThe techniques and results of a heat-balance programme on Sørbreen, Jan Mayen, are presented and discussed. Estimates of 24 hr. heat-transfer totals under frontal and non-frontal weather conditions are then made. Transfer is found to be higher during frontal conditions, due to an increase in latent and to a lesser extent sensible heat transfer. Consideration of upper air temperatures and humidities suggests this higher transfer is experienced by the glacier as a whole. It is then proposed that summer rainfall totals will provide an index of frontal activity which may be used to indicate relative ablation from one summer to another. A statistical comparison of ablation measured on the glacier and rainfall recorded at the Jan Mayen meteorological station supports this suggestion.

scholarly journals Analysis of the Thermal Characteristics of Surrounding Rock in Deep Underground Space

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Liu Chen ◽  
Jiangbo Li ◽  
Fei Han ◽  
Yu Zhang ◽  
Lang Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Thermal Characteristics ◽  
Surrounding Rock ◽  
Underground Space ◽  
Human Society ◽  
Distribution Characteristics ◽  
Air Temperatures ◽  
Rock Temperature ◽  
Deep Underground

With the development of society, the economy, and national security, the exploitation of deep underground space has become an inevitable trend in human society. However, high-temperature-related problems occur in deep underground spaces. The high temperature of deep underground space is essentially influenced by the thermal characteristics of the surrounding rock. According to the mathematical model of heat transfer of the surrounding rock in deep underground space, similar criteria numbers are established. Experiments were carried out to investigate the thermal characteristics of the surrounding rock. The distribution characteristics of temperature were determined by the Fourier number (Fo) and Biot number (Bi), and the effects of heat transfer time, airflow velocities, and air temperature and radial displacement on the distribution characteristics of temperature were studied. The results indicate that the surrounding rock temperature decreases with long heat transfer times, high airflow velocities, and low air temperatures.

Effect of cold exposure on resistance to hemorrhage in dogs

1959 ◽  
Vol 196 (4) ◽  
pp. 715-718 ◽  
Author(s):  
Leslie A. Kuhn ◽  
Lot B. Page ◽  
John K. Turner ◽  
Julian Frieden
Keyword(s):  
Blood Pressure ◽  
Arterial Blood Pressure ◽  
Mean Arterial Blood Pressure ◽  
Cold Exposure ◽  
Normal Range ◽  
Arterial Blood ◽  
Air Temperatures ◽  
The Mean ◽  
A Minor

Effects of progressive hemorrhage during severe cold exposure were studied in 17 unanesthetized dogs. The amount of blood required to be withdrawn to reduce the mean arterial blood pressure to 50 mm Hg by a standardized bleeding procedure was determined in the same animals at air temperatures of +25°C and –25°C. Cold-exposed dogs showed a statistically significant increased ‘resistance’ to hemorrhage in that an average withdrawal of 20% more blood was required to reduce mean arterial blood pressure to shock levels in the cold than in the same dogs at comfortable temperature. In six animals it was necessary to draw a minor, but measurably greater, amount of blood from a given dog to produce hypotension during cold exposure than when the procedure was performed at a comfortable temperature and, in two animals, a minor, but measurably less, amount of blood was withdrawn during cold exposure. In seven animals a significantly greater amount of blood was drawn in the cold than in a neutral environment, but in some of these animals the control bleeding was apparently substandard. In two animals the control bleedings were in the normal range and bleedings were substandard in the cold. Cortisone administration did not alter resistance to hemorrhage during cold exposure.

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