Forced Convection (Tube bundle) - University of Jordan
Transcription
Forced Convection (Tube bundle) - University of Jordan
UNIVERSITY OF JORDAN CHEMICAL ENGINEERING DEPARTMENT PROCESS HEAT TRANSFER (0905343) Forced Convection (Tube bundle) Instructor: Dr. Ali Al-Shawabkeh In-class tutorial 4P Problem 1: A preheater involves the use of condensing steam at 100°C on the inside of a bank of tubes to heat air that enters at 1 atm and 25°C. The air moves at 5 m/s in cross flow over the tubes. Each tube is 1 m long and has an outside diameter of 10 mm. The bank consists of 196 tubes in a square, aligned array for which ST = SL = 15 mm. Ts = 100°C N = 196 S L = S T = 15 mm Air Ti = 25°C To = ? υ = 5 m/s L =1m D = 10 mm a)- What is the total rate of heat transfer to the air? b)- What is the pressure drop associated with the airflow? Problem 2: Air is flowing over a 5-row tube bank. The air enters the enclosing duct at a temperature of 288 K, and it leaves at 312 K. The air flow is 0.236 m3/s, and is at atmospheric pressure. The staggered tubes have an outside diameter of 0.025 m, and a length of 1.22 m. The outside surface temperature Ts = 381 K SL S = T = 2 .0 D D + + + Air 0 . 236 m 3 /s Ti = 288 K + + + + + + + + L = 1 .22 m + + + + + + + + + To = 312 K + + + D = 2 .5 cm + + of the tubes is maintained at a uniform temperature of 381 K. The longitudinal and transverse S S pitches for the bundle are given by L = T = 2.0 . If the minimum free flow cross-sectional area D D is 0.155 m2, calculate the average heat transfer coefficient.