Page 30 - HVAC Pump Handbook

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Physical Data for HVAC System Design

Physical Data for HVAC System Design 27

Figure 2.6 Freezing points of heat transfer fluids. (From Engineering Data for Ethylene
Glycol–Based Heat Transfer Fluids, Union Carbide Corporation, Danbury, Conn., 1993,
p. 10.)

where c specific heat of ethylene glycol heat-transfer solution at
p
constant pressure
T differential temperature
specific weight of water

Note. All these values must be at the operating temperature of the
solution. For many glycol installations, this calculation should be run
at several different operating temperatures. For example, assume
that an ethylene glycol based heat-transfer fluid has a heating load of
5 million Btu/h at 30°F with a differential temperature of 12°F. The
pumps will be operating with a 40% glycol solution. From Fig. 2.7, the

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