TM
5-858-7
postattack because of the increasing vulnerability
sink volume can also be reduced by use of ice-water
mixtures.
of the AES and the rapid increase in the require-
ment for parasitic power to transport the air via
c. Heat-sink volume requirements are greatly
the AES.
influenced by the power system's efficiency and
maximum heat-rejection temperatures. Some ap-
b. Reduce the necessary AES air-handling ca-
proximations useful for preliminary design esti-
pacity by restricting use of atmospheric air to that
mates of water-filled heat sinks are given in table
required for personnel and air-breathing power
32. The heat-sink volumes given in the table are
generators. About 20 percent of the facility waste
based on the assumptions indicated for waste-heat
heat can be rejected via engine exhaust through
distribution and heat-rejection temperatures. All
the AES outlet duct for a diesel-generator power
waste heat is treated as power-system dependent,
system. For preattack, reject the rest of the facili-
with the total electrical power converted to low-
ty waste heat by water transport system to a
temperature waste heat.
surface-located, unhardened water-cooling tower.
For postattack, reject the balance of waste heat to
d. To attain the greatest possible heat-sink us-
a closed heat sink. (The cooling tower will be used
age with the least possible heat-sink volume, strive
preattack to maintain the heat sink unreadiness at
for the smallest feasible differential between the
the required temperature, and must be sized
maximum heat-rejection temperature and the max-
accordingly. )
imum heat-sink temperature. The minimum differ-
c. The AES for a moderately hardened facility
could also be used to reject high-temperature
with direct water-cooing or substantially larger-
than-normal counterflow heat exchangers. How-
waste heat via ebullient cooling. Use of this meth-
ever, the minimum practical differential achievable
od of waste-heat rejection would decrease the heat-
sink storage volume by factors from 10 to 25 for
that fraction of the heat rejected as steam from
ample, if air cooling of personnel shelters is the
controlling requirement, the maximum heat-sink
ebullient cooling.
mechanical refrigeration is used.
3-5. Superhard facilities.
e. The waste-heat distribution for the closed-
a. During the preattack period, the waste heat
cycle diesel system, as shown in table 32, allows
of a superhard facility would be rejected to the at-
for a 25 percent increase in total waste heat in the
mosphere via, for example, a water transport sys-
low temperature range for carbon dioxide absorp-
tem to a surface-located, unhardened water-cooling
tion. The assumed overall thermal efficiencies for
tower, sized to maintain the closed heat sink at the
the diesel and Stirling engine systems are inten-
required temperature condition. However, super-
tionally conservative because the closed-system ef-
hard facilities are deeply buried, and during
ficiency and heat balance are the least clearly de-
postattack will require completely closed waste-
fined for these systems. For 7 of the 10 cases
heat rejection and air-reconstitution systems. De-
listed, the low-temperature cooling requirement
sign considerations for the closed-air reconstitution
limits the maximum heat-sink temperature, i.e.,
system are discussed in chapter 4. Factors to be
the final water temperature cannot approach the
considered in the design of closed heat sinks are
maximum reject temperature. The assumption of
discussed below.
90 percent heat-sink efficiency may or may not be
b. In closed-system waste-heat rejection, the to-
conservative. Unquestionably, there will be some
tal waste heat is rejected to a closed heat sink,
mixing of cold heat-sink water with warm return
which is generally a water-filled cavity. Heat sink
water and some conductive heat transfer within
volume depends on the initial water temperature
the heat sink. Such mixing and conductive transfer
and the maximum allowable final water tempera-
will reduce the effective heat-sink capacity to some
ture. The maximum final water temperature will
degree.
depend on the type of electric power supply system
f. The last column in table 3-2 compares heat-
used and the design of the waste-heat transport
sink volume required per unit of electrical power
system. Without allowance for heat-sink inefficien-
produced by different power systems, based on the
cies and heat load from geologic media, the heat-
assumed system efficiencies and heat-sink condi-
sink volume in cubic feet per magawatt-hour of
tions. Substantial reductions in heat-sink volume
t h e r m a l energy is approximately equal to
57,000/∆Τ, where ∆Τ is the water temperature rise
are possible by reducing the initial heat-sink tem-
in "F. When ebullient cooling is used, the water
storage volume is less than 55 ft3/MWh. The heat-
frigeration to raise the rejection temperature of
3-3
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