An air-cooled steam condenser is operated with air in cross flow over a square, in-line array of 400 tubes (N_L = N_T = 20), with an outside tube diameter of 20 mm and longitudinal and transverse pitches of SL = 60 mm and ST = 30 mm, respectively. Saturated steam at a pressure of 2.455 bars enters the tubes and a uniform tube outer surface temperature of T_s = 390 K maybe assumed to be maintained as condensation occurs within the tubes.

(a) If the temperature and velocity of the air upstream of the array are T_i = 300 K and V = 4 m/s, what is the temperature T_o of the air that leaves the array? As a first approximation, evaluate the properties of air at 300 K.

(b) If the tubes are 2 m long, what is the total heat transfer rate for the array? What is the rate at which steam is condensed in kg/s?

(c) Assess the effect of increasing N_L by a factor of 2, while reducing S_L to 30 mm. For this configuration, explore the effect of changes in the air velocity.