1. The problem statement, all variables and given/known data The air emerging from a hot aqueous process at a temperature of 45°C, passes over a surface which is gradually cooled. It is found that the first traces of moisture appear on this surface when it is at 40°C. Estimate the relative humidity of the air leaving the dryer. 2. Relevant equations None. 3. The attempt at a solution I'm just wondering, is it possible using the psychometric chart I've attached to answer the above problem? To me, it just seems like the wet bulb line ends at 30 C and you can't read off the value of 40 C.