Page 355 - HVAC Pump Handbook

Rishel_CH12.qxd 20/4/06 6:39 PM Page 352

Pumps for Process Cooling

352 Pumps for Open HVAC Cooling Systems

heat transferred (Btu/h)
Flow (gal/min)
( /7.48) 60 T (°F)
heat transferred (Btu/h)
(12.1)
8.02 T (°F)
where is the specific weight of water at cooling tower return water
temperature

12.3 Energy Recovery
Some industrial processes operate with higher return water tempera-
tures to the cooling towers. This increases the possibilities of energy
recovery, as discussed in Chap. 11 on cooling towers and as will be
reviewed in Chap. 16 on closed condenser water systems.

12.4 Gas Stream Cooling
Gas stream cooling with cooling towers or special spray towers is lim-
ited mostly to those gases which are exhausted to the atmosphere.
Typical of these are gas turbine, boiler, and incinerator exhausts.
Many of these processes also scrub the gases, so the water from them
will contain chemicals that may be abrasive or corrosive to pumps.
This is particularly so if scrubbers are used to clean the gases and to
absorb specific chemicals that are known to exist in the gases.
Specific attention should be paid to the metallurgy of the pumps for
scrubbers. Erosion also may be a problem, necessitating the use of
rubber-lined pumps to provide a useful life of the volute. Most pumps
for such services are end-suction pumps to simplify the construction
and repair capabilities. Special mechanical seals with flushing equip-
ment may be required to keep the pumpage out of the seal cavities.
Ease of maintenance, not efficiency, is often the prerequisite for these
pumps, which is the opposite of that for most HVAC pumps.
The water flow rates should be determined by the user or manufac-
turer of the cooling equipment. The actual water flow is determined
not only by cooling rates but also by flushing or filtering requirements.

12.5 Bibliography
James B. Rishel, The Water Management Manual, SYSTECON, Inc., West Chester,
Ohio, 1992.

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