Convective Heat Transfer in Hypobaric Environments
Abstract
This study examined the relationship between convective heat transfer and barometric pressure (P sub b), specifically, how hypobaric pressure affects the convective heat transfer coefficient (H sub c). Five environmental conditions were simulated at elevation of 0 (sea level), 1520 m (5000 ft), 3050 m (10,000 ft), 4570 m (15,000 ft), and 6100 m (20,000 ft). In the chamber, constant temperature (30 C) and wind speed (0.5m/s) were maintained. The convective heat transfer coefficient was determined using the naphthalene sublimation technique. Circular naphthalene disks were affixed to six sites on a stationary copper manikin. The amount of naphthalene weight loss through sublimation was translated to H sub c using the Chilton-Colburn j-factor analogy between heat and mass transfer. As elevation increases, P sub b decreases; H sub c should decrease accordingly, pointing to a diminished convective heat transfer mechanism. Hitherto, the relationship between H sub c and P sub b was thought to be a nonlinear power function. Our results showed that convective transfer indeed decreased at higher elevation, but H sub c and P sub b exhibit a linear relationship. A linear relationship was also obtained from a theoretical derivation. These results suggest that in a hypobaric environment, the convective transfer process becomes even more diminished, and the potential convective heat loss is smaller than the original nonlinear theory would predict. Keywords: Convective heat transfer coefficient; Barometric pressure; Heat mass transfer analogy; Chilton-Colburn j-factor.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1989
- Accession Number
- ADA212060
Entities
People
- Richard R. Gonzalez
- Stephen K. Chang
Organizations
- United States Army Research Institute of Environmental Medicine