A dryer recycles10 m³/s exhaust at 70°C,30% RH, humidity ratio .06335 kg/kg dry air. It mixes with 20 m³/s ambient air at 30°C,60% RH, humidity ratio .016. Find mixed humidity ratio in kg/kg dry air, to three decimals.
At common pressure, dry-air mass flow is proportional to $\dot V/[T_K(1+1.6078w)]$. The relative mass rates are $10/[343.15(1+1.6078(.06335))]=.02645$ and $20/[303.15(1+1.6078(.016))]=.06432$. Mass-weighting humidity gives $w_m\approx.02980$, or **.030 kg/kg dry air**. Direct volume weighting is less accurate because stream densities differ.
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