Question

An infection control room in a hospital has dimensions 4m x 6m x 3m. The temperature in the room is 20 C. The relative humidity in the room 80%. Overnight, the temperature of the window surfaces drops to 14 C.

A) what is the moisture content in the room?

B) What is the minimum of water that a dehumidifier must remove such that condensation will not occur on the windows overnight?

Answer 1

(A) Saturation vapour density at 20⁰ C = 17.3 g/m³

Putting the values

80/100 = Actual vapour density/17.3

Actual vapour density (moisture content) = 13.84 g/m³

(B) At 14⁰ C the saturation vapour density = 12.07 g/m³. For the condensation to not occur the minimum excess moisture = 13.84 - 12.07 = 1.77 g/m³ has to be removed from the room.

Hence the minimum water to be removed from the room = 1.77 g/m³ x (4m x 6m x 3m)

= 127.44 g