4. In a humidifier, air at a dry bulb temperature of 40 oC and relative humidity of 10% is humidified to a relative humidity of 40%. Determine the amount of moisture added in the humidifier per kg of dry air.

0.0141 kg/kg.

Explanation:

So, we are given the following parameters or information from the problem above:

The relative humidity = 10% was humidified to 40%, the temperature = 40°C.

From the chart, at temperature = 40°C and relative humidity = 10%, the weight of dry air = a1 = 0.0046 kg/kg, volume = 0.89 m³/kg.

Also, from the chart  at temperature = 40°C and relative humidity = 40%, the weight of dry air = a2 = 0.00187 kg/kg, volume = 0.913 m³/kg.

Therefore, the amount of moisture added in the humidifier per kg of dry air = 0.0046 kg/kg - 0.00187 kg/kg = 0.0141 kg/kg.