Limit Heat Loss Research Articles

Thermoregulation in babies immediately after birth.

The fall in body temperature that occurs in babies soon after birth is influenced by the baby's weight and its environmental conditions. The rate of oxygen consumption 1 1/2 hours after birth was unrelated to body temperature and only slightly raised, indicating a limited thermogenic capacity. A radiant heater effectively prevented cooling in babies kept with their mothers in the delivery room. Washing soon after birth caused a significant cooling. Healthy term babies were found to have a limited thermogenic response to a cool environment over the first 12 hour of life and efforts to limit heat losses should be concentrated on this period.

Northern fur seal thermoregulation: Thermal responses to forced activity on land

1. 1.|Temperatures from 11 different sites representing core, trunk periphery, and hindflippers were measured in 86 harvested northern fur seals after they had been forcibly driven overland under a variety of terrestrial conditions. This has enabled an assessment of their thermal responses to various extrinsic and intrinsic heat loads. 2. 2.|Hyperthermia resulted from forced terrestrial activity, but the level of hyperthermia varied with ambient conditions. Solar radiation led to overheating, and rain or condensation on vegetation that wet the fur, aided heat loss and helped prevent overheating. 3. 3.|The present investigation quantitatively confirms previous suggestions that the effectiveness of fur insulation over the seals' trunk requires that the large bare flippers, with thine xpandable webbing, assume the major role of dissipating heat. Due to their limited heat loss capability on land, the fur seal's primary response to forced terrestrial activity is involuntary heat storage and tolerance of hyperthermia to approximately 43°C.

On the 10-year static vacuum integrity of vacuum foil insulation for an implantable artificial heart

Vacuum multifoil insulation systems are being developed for an implantable artificial heart. These insulation systems are thermally efficient and physically compact, being able to limit heat losses to less than 0.024 W/cm2 with an 832 °C temperature gradient across a 0.5-cm insulation thickness. The maintenance of a 10−3-Torr static vacuum for 10 yr is critical to the success of the implantable artificial heart. The determination of the maximum allowable pressure for satisfactory vacuum foil insulation performance is reported. Also, the outgassing characteristics of several Ti and Nb–1Zr insulation packages were evaluated after 300 h of thermal testing and about 3600 h after final fabrication. The only gas found in the system was hydrogen, and possible sources of hydrogen are considered. Finally, outgassing characteristics of specific vacuum foil insulation material such as electroplated Ni, as well as procedures used to eliminate gas loads from this material are reported.

Performance characteristics of rectangular honeycomb solar-thermal converters

An array of rectangular cells, properly shaped with highly reflecting specular walls absorbing to infrared radiation, is shown to be an effective device to limit heat losses when placed over a solar absorber. Theoretical relationships are presented which permit the prediction of the performance of closed-cell and air transpiration systems. The theory rests on analytical and experimental studies of radiant transmission through cells with specularly reflecting, polarizing walls coated with an absorbing film and studies of the suppression of natural convection in cells heated from below. Good agreement was obtained between theory and experiments for the air transpiration system. Three experimental honeycombs of different geometries were tested over a 1-sq ft blackened fiberglass porous absorber, assembled in a well-insulated and glazed housing mounted on a tilting platform to permit any desired orientation. Experiments over a 1-yr period, and theoretical predictions, indicated that the thermal efficiency could be given as a linear function of the ratio of temperature difference between the average temperature of the working fluid and ambient air to the incident solar power, virtually independent of flow, angle of tilt and time of collection. For the best honeycomb tested, the thermal efficiency ranged from 82 to 63 per cent for values (T av − T a) G s equal to 0·10 and 0·30°F/ (B.t.u./hr ft 20, respectively. The honeycomb-porous bed solar-air heater is shown to perform as well as the best previously reported solar-air heater at moderate temperatures. At higher temperatures, of the order of 200°F, it is greatly superior.