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MoistAirTab™ Example 2 - Mixing Streams

Example 2

A stream of 2 m3/s of outdoor air at 4°C dry-bulb temperature and 2°C wet-bulb temperature is mixed with 6.25 m3/s of recirculated air at 25°C dry-bulb and 50% relative humidity. What is the dry-bulb, wet-bulb temperatures and relative humidity of the mixed stream?

Solution

The solution is presented below as a table generated from Excel. The gray shaded areas represent the input data.

Soution:UnitsSteam-1Stream-2Mixture
Total pressurebar1.013251.013251.01325
Moist air volumetric flow ratem3/s2.006.258.25
Dry bulb temperature°C4.0025.0019.67
Wet bulb temperature°C2.0017.8814.58
Relative humidity%71%50%58%
Obtain the mixed stream's humidity ratio:
Specific volume (dry air)m3/kgdry air0.78480.84440.8293
Mass flow rate (dry air)kgdry air/s2.557.409.95
Humidity ratiokgw/kgdry air0.00360.00990.0083
Moisture flowrate kgw/s0.010.070.08
Obtain the mixed stream's specific humidity:
Specific enthalpy of moist airkJ/kgdry air12.9750.4240.83
Enthalpy flowkJ/s33.06373.20406.26