b. Problem 2.
(1) The purpose of this problem is to illustrate the load calculation procedures, tunnel air
tempering, and the shortcut method for holding operation. Assume there is an underground rectangular
space of 1,000 feet long, 720 feet wide, 12.5 feet high, having bare walls, in which a communication center
is installed and operated under normal conditions by 300 personnel engaged in light work. The structure
is supported by 178 cylindrical pillars of original limestone averaging 550 square feet cross-section per
pillar.
(2) Assume that 600 days (t= 14,400 h) have elapsed since the beginning of a holding period at 70 F
and 50 percent RH. At this condition there is steady evaporation from the rock at 0.7 grains/ ft2 h. The
original rock temperature is 56
rectangular 4 ft by 6 ft rock tunnel that is 4,500 ft long. The outside annual air amplitude is 40 0 F. The
internal heat load included lighting at 3 W/ft2 , 250 hp ventilation fan motors at 91 percent overall
efficiency, and 6,000 kW maximum equipment load including the air-conditioning. From table 3-1,
(3) Exposed areas, rounded to the nearest 1000 ft2 , are estimated as follows:
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