ENGINEERING EVALUATION 319 



canisters. The design flow capacity of the CO 2 scrubber was approximately 60 cfm. At this 

 flow rate, complete circulation of the atmosphere (4000 cu ft) would require 66 minutes. The 

 charcoal filter consisted of two units containing approximately 1400 cu in. of charcoal each. 

 The filters were rechargeable and were sized to operate for approximately ten days before re- 

 placement. Six filtei units were supplied. The design flow capacity of the charcoal filter was 

 250 cfm. Complete circulation of the atmosphere through this filter would require 16 minutes. 

 Of this total flow, tO cfm was drawn through the CO2 filter. The remaining 190 cfm was drawn 

 through the water-closet compartment and generally from the galley area. This arrangement 

 served to control odors in the water-closet compartment (where the sanitary drains were 

 vented) and to remove any hydrocarbons produced in cooking. 



Atmosphere circulation was accomplished with a centrifugal blower powered by a 1/2- 

 horsepower electrical motor. The normal power input to the fan was doubled because of the 

 increased density of the ambient atmosphere, approximately twice that of standard air. Dis- 

 tribution was accomplished through a single fore-and-aft duct, with one overhead grill in each 

 of the four areas. 



Make-up gas mixing was provided for by introducing make-up helium or air into the vent 

 plenum upstream of the blower. Make-up oxygen was introduced into the discharge duct at the 

 point of highest velocity (see "Oxygen System," later in this chapter). 



Although specified in the "air conditioning package," time and budget did not allow integra- 

 tion of the humidity control system. Three dehumidifiers were installed in Sealab II, each hav- 

 ing a rated capacity, at standard conditions, of 47 pints per day, and one portable unit of like 

 capacity was provided as a back-up. Two of the three installed units were located for intake of 

 wet atmosphere from the entry area and discharge into the lab area. The third unit was located 

 in the galley area to remove moisture produced in cooking and washing. A design control level 

 of 70 percent relative humidity was selected to insure reliable operation of the "Krasberg" 

 oxygen partial-pressure sensors for the total test period, based on manufacturer's recom- 

 mendations. 



Heating System 



The heating equipment specified as a part of the air-conditioning system was omitted be- 

 cause of space limitations. The living space was heated by means of electrical convection 

 heaters mounted on the shell, radiant deck heating, and overhead radiant heaters. A total of 

 26.65 kw of electrical heating capacity was provided, based on extrapolation of data obtained 

 from Sealab I and the heat-loss calculations shown in Appendix B. The capacity of the heating 

 system was increased to provide approximately 50 percent more heat input than indicated by the 

 heat-loss calculations. Further, it was anticipated that as much as 20 kw of sensible heat might 

 be realized from operating equipment in Sealab such as lights, electronics, motors, pumps, 

 and fans. This overdesign was considered to be extremely desirable in the event of possible 

 failure of portions of the heating system. 



The convection heating system was designed for connection to the 450-volt, three-phase 

 line. Two commercial 240-volt baseboard heaters were connected in series, and three such 

 groups were then connected in delta to the three-phase power. Separate banks were installed 

 in the berthing, galley, and lab areas and were controlled by individual thermostats. Of the 

 total heating capacity, 16.7kw was provided by the convection heaters. 



The radiant heating of the deck was provided by embedding mineral insulated heating cable 

 in the concrete deck in the berthing, galley, and lab areas. The entire system was controlled 

 by a single thermostat with its sensing element embedded in the concrete deck. A total of 

 4.95 kw of the heating capacity was provided by this system. 



Four 1250-watt overhead radiant heaters were installed in the entry area and in the after 

 end of the lab area. These units provided quick heat for warming up after showers and outside 

 sorties. The heaters were controlled by individual off-on switches. 



