period one
Types of Water Chillers
notes
Flow Rates and Temperatures
QBtu/hr = 500 ⋅ flow rate ⋅ ∆T
[QW = 4,184 ⋅ flow rate ⋅ ∆T ]
equation for water only | Figure 24 |
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.
Q = 500 ⋅ flow rate ⋅ ∆T
[Q = 4,184 ⋅ flow rate ⋅ ∆T]
where,
nQ = load, Btu/hr [W]
nflow 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]
8.33 lb/gal ⋅ 1.0 Btu/lb° F ⋅ 60 min/hr = 500 [1.0 kg/L ⋅ 4,184 J/kg° K = 4,184]
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