On a cool day in April a scantily clothed runner is known to lose heat at a rate of 500 W because of convection to the surrounding air at T∞ = 10oC. The runner's skin remains dry and at a temperature of Ts = 30°C. Three months later, the runner is moving at the same speed, but the day is warm and humid with a temperature of Too = 30°C and a relative humidity of ϕ∞ = 60%. The runner is now drenched in sweat and has a uniform surface temperature of 35°e. Under both conditions constant air properties may be assumed with v = 1.6 x 10-5 m2/s, k = 0.026 W/m ∙ K, Pr = 0.70, and DAB (water vapor-air) = 2.3 X 10-5 m2/s.

(a) What is the rate of water loss due to evaporation on the summer day?

(b) What is the total convective heat loss on the summer day?