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Two examples have been developed to demonstrate the conversion. Case I is for a
sealed room, with no air turnover. Case II is for a room with a known air turnover.
Case I: Sealed room 15 m x 10 m x 3 m
high
1. How much R-22 (in kg) is necessary to
cause a measurement of 25 ppm?
Given 25 ppm R-22 in the sealed room:
Volume of R-22 = parts per million / million x room
volume
R(cubic meter) = [25(ppm)/1,000,000] x [15 x 10 x 3](cubic meter)
R(cuft) = .01125 cubic meter of R-22 in the sealed room
Given .01125 cubic meter R-22, calculate
weight in kg:
Weight = volume(cubic meter) x density(kg/cubic meter)
Weight = R(cubic meter) x RD22(kg/cubic meter)
Weight = .01125(cubic meter) x 3.59(kg/cubic meter)
Weight = .040 kg
2. If the leak rate is 150 kg/yr, how long will
it take to reach 25 ppm?
Given the same refrigerant in the same
room, 25 ppm weighs .040 kg:
Time(hr) = weight of R-22(kg) / [weight(kg)/time(yr)] x
[time(hr)/time(yr)]
Time(hr) = .040(kg) / [150(kg)/1(yr)] x [8760(hr)/1(yr)]
Time(hr) = 2.34 hrs
Case II: 10 m x 15 m x 3 m high room with
fresh air makeup of 225 cubic meter/hr
1. How much R-22 (in kg/yr) is necessary to
cause a measurement of 25 ppm?
Given air turnover of 225cubic meter/hr,
calculate the leak rate that is required to
maintain a measurement of 25 ppm:
Leak rate min (cubic meter/hr) = parts per million/million x fresh
volume(cubic meter/hr)
Leak rate min (cubic meter/hr) = [25(ppm)/1.000.000] x 225(cubic
meter/hr)
Leak rate min(cubic meter/hr) = .005625 cubic meter/hr
Given .005625 cubic meter/hr, calculate the
leak rate in kg/yr needed to reach 25 ppm:
Leak rate(kg/yr) = leak rate(cubic meter/hr) x density(kg/cubic
meter) x [8760(hr) / 1(yr)]
Leak rate(kg/yr) = .005625(cubic meter/hr) x 3.59(kg/cubic meter)
x 8760(hr/yr)
Leak rate(kg/yr) = 176.9 kg/yr, therefore the leak rate must be
GREATER THAN 177 kg/yr.
2. If the leak rate is 300 kg/yr, how long will
it take to reach 25 ppm?
Calculate LR in cubic meter/hr:
LR(cubic meter/hr) = [leak rate(kg/yr) / density(kg/cubic meter)] /
8760(hr/yr)
LR(cubic meter/yr) = 300(kg/yr) / 3.59(kg/cubic meter) /
8760(hr/yr)
LR(cubic meter/yr) = .009539 cubic meter/hr
Calculate time in hr:
Time(hr) = [Room volume(cubic meter)/Air flow(cubic meter/hr)] x
ln[LR(cubic mete/hr) / [LR(cubic meter/hr) – Leak rate min(cubic
meter/hr)]]
Time(hr) = [450(cubic meter)/225(cubic meter/hr)] x
ln[.009539(cubic meter/hr)/[.009539(cubic meter/hr)-
.005625(cubic meter/hr)]
Time(hr) = 2(hr) x ln[2.437] Time(hr) = 1.78 hr
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