Heater Testing 



Laboratory bench tests of the heater were conducted to determine 

 overall performance. Electrolyte temperature, temperatures across the 

 diver load, and suit-water flowrate were recorded. The diver load was 

 simulated by immersing a copper tubing heat exchanger into a refriger- 

 ated bath. The heater's power output was calculated using the flowrate 

 and the suit -water temperatures. A typical power curve for an 8-hour 

 test is shown in Figure 30. Power output for the 16-kW-hr heater is 

 shown in Figure 31. 



In late May 1975 the heater was first integrated with the heat 

 distribution garment and thermal protection suit developed by NCSL. 

 Previous tests with a diver had established a base line power require- 

 ment and typical skin and rectal temperature trends. 



For the integrated test, the heater was carried on the diver's 

 back and suit-water flow and electrolyte and suit-water temperatures 

 were monitored. The diver's rectal temperature was used as the absolute 

 indicator of the heater's effectiveness. During the first 4 hours of 

 the test, the rectal temperature exhibited the typical slow decline. 

 However, just after 4 hours, it began to rise (Figure 32) and continued 

 to rise during the next hour. The test was considered successful since 

 the temperature rise indicated that the diver was returning to a stable, 

 normal condition. 



Human Considerations 



Since the end product of this development effort will be hardware 

 carried by free-swimming divers, a human factors study was initiated to 

 determine man/equipment interface problems (the appendix). The objective 

 of the study was to determine what size and shape the heater could 

 attain without restricting the free-swimming diver's mobility. Discus- 

 sions were held with cognizant tactical diver-oriented personnel, and 

 then mock-ups of potential diver heating units based on available free- 

 body space were built and tested. The testing involved diver/swimmer 

 drag measurements and diver subjective analysis. 



The results of the human factors analysis showed that a chest mock- 

 up (Figure 33) was preferred over the others tested. The divers favored 

 the chest-worn unit, because they would prefer to retain the heater and 

 stay warm in the water if they should have to ditch their breathing 

 equipment. 



16 



- -J 



