Screening Study to Identify Phase Change Coolants for Portable Life Support Systems.
Abstract
A literature search to identify coolant candidates to be considered for replacing the ice-water system in a portable life support unit led to the following considerations: CO2, an NH3-CO2 mixture, and a salt such as potassium acid fluoride incorporated into ice. In the CO2 system, solid CO2 will sublimate and the resultant gases warm to 4 C, then be expelled from the suit. The heat absorption for this process is 153.0 Kcal/kg. To achieve 504 Kcal (2000 Btu) of cooling, 3.3 Kg (7.3 lbs) of CO2 is needed. This is an 83% improvement over the heat absorption of ice melting and warming to 4 C, or a 45% reduction in the weight of ice needed. The CO2 system appears to be completely safe. In the NH3-CO2 system, the CO2 will sublimate, the NH3 vaporize, and the resultant gases warm to 4 C, then with mixing be expelled from the suit. This system might be flammable, so should be examined in the laboratory. The heat absorption for this system is an impressive 198.5 Kcal/kg for an 0.8 mole ratio of NH3 to CO2. To achieve 504 Kcal (2000 Btu) of cooling, 2.5 Kg (5.6 lbs) of total coolant is needed. This is a 137% improvement over the heat absorption of ice melting and warming to 4 C, or a 58% reduction in the weight of ice needed. In the potassium acid fluoride-ice system, the heat of solution of the salt is added to the heat of fusion of ice. Over the temperature range of about -15 to 5 C, this system yield 121 Kcal/kg. To achieve 504 Kcal (2000 Btu) of cooling, 4.12 Kg (9.2 lbs) of total coolant is needed. This is a 45% improvement over the ice alone system.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1977
- Accession Number
- ADA038504
Entities
People
- Sandra S. Donovan