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TRG-TRC016-EN 21
period one
Types of Water Chillers
notes
The temperature difference (∆T) through the chiller and the water flow rate are
related. For a given load, as the flow rate is reduced, the ∆T increases, and vice
versa.
where,
n Q = load, Btu/hr [W]
n flow rate = water flow rate through the chiller, gpm [L/s]
n ∆T = temperature difference (leaving minus entering) through the chiller,
ºF [°C]
Realize that 500 [4,184] is not a constant! It is the product of density, specific
heat, and a conversion factor for time. The properties of water at conditions
typically found in an HVAC system result in this value. Other fluids, such as
mixtures of water and antifreeze, will cause this factor to change.
Density of water = 8.33 lb/gal [1.0 kg/L]
Specific heat of water = 1.0 Btu/lb°F [4,184 J/kg°K]
Flow Rates and Temperatures
equation for water only
Q
Btu/hr
= 500 × flow rate ×∆
∆∆
∆T
[ Q
W
= 4,184 × flow rate ×∆T ]
Figure 24
Q 500 flow rate ∆T××=
Q 4,184 flow rate ∆T××=[]
8.33 lb/gal 1.0 Btu/lb° F 60 min/hr 500=××
1.0 kg/L 4,184 J/kg° K4,184=×[]