Parameters
Presets
Water flow rate ṁ_w
10.0 kg/s
Hot inlet temperature T_in
45.0 °C
Cold outlet temperature T_out
30.0 °C
Wet-bulb temperature T_wb
24.0 °C
Dry-bulb temperature T_db
32.0 °C
Air flow rate Q_air
15.0 m³/s
T_out ≤ T_wb: physically impossible condition
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Range (T_in − T_out) [K]
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Approach (T_out − T_wb) [K]
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Effectiveness η [%]
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Heat duty Q [kW]
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Evaporation rate [%]
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NTU [-]
Theory
Cooling effectiveness (wet-bulb basis):
$$\eta_{approach}=\frac{T_{in}-T_{out}}{T_{in}-T_{wb}}\times 100\%$$NTU (Merkel method):
$$NTU=\int_{T_{out}}^{T_{in}}\frac{dT_w}{T_w-T_{wb,local}}$$Heat duty: $Q=\dot{m}_w \cdot c_p \cdot (T_{in}-T_{out})$ [kW]
Evaporation approx.: $\dot{m}_{evap}\approx 0.00085\,\dot{m}_w\,(T_{in}-T_{out})$ [kg/s]
Engineering applications: HVAC & industrial cooling system design · Data center liquid cooling infrastructure · Power plant cooling water analysis · CFD packing flow boundary condition setup. Merkel number is the basis of ASHRAE Handbook cooling tower design.