1. A moist airstream with a pressure of 100 kPa has an initial dry bulb of 30 °C and a wet bulb of 24 °C. Use the 100 kPa psychrometric chart provided to calculate the end dry/wet bulb to this original airstream when subjected to the following processes:
(a) Heating at constant moisture content, raising the specific enthalpy by 8 kJ/kg.
(b) Enthalpy increase of 8 kJ/kg, moisture content increases to 19 g/kg.
(c) Constant dry bulb cooling to a moisture content of 0.01 kg/kg.
(d) Constant dry bulb heating to a relative humidity of 90 %.
(e) Constant wet bulb (and sigma heat) process to a relative humidity of 30 %.
(f) Constant wet bulb process to saturation.
(g) Constant moisture content process to saturation.
2. The following two airstreams mix at the junctions of two roadways. The first airstream has a mass flow of 10 kg/s and a dry/wet bulb of 20/10 °C, the second airstream has a mass flow of 20 kg/s and a dry /wet bulb of 30/19 °C. The pressure is 100 kPa. Determine the dry/wet bulb temperatures of the mixed airstream.
If the mass flows were 20 kg/s for the first airstream and 10 kg/s for the second airstream, what would be the dry/wet bulb of the new mixed airstream?
3. For the following psychrometric combinations, calculate the dry/wet bulb temperature assuming a pressure of 100 kPa:
• 100 % relative humidity, 0.02 kg/kg dry air moisture content.
• Enthalpy of 70 kJ/kg, relative humidity of 20 %
• Sigma heat of 60 kJ/kg, moisture content of 0.0125 kg/kg dry air.
4. The radon daughter concentration leaving a mine section is 0.2 WL when the airflow is 20 m3/s. A temporary obstruction caused by stocked materials reduces the airflow to 5 m3/s. Determine the effect on the radon daughter concentration.
5. A mine opening is ventilated by an airflow of 15 m3/s. The exit concentration of radon daughters is 1.0 WL. If this is to be reduced to 0.33 WL, determine the required airflow.