Question

(3.9) Aheat exchanger consists of two E-shells connected in series and contains a total of 488 tubes arranged for four passes (two per shell). The tubes are 1-in. OD, 16BWG with a length of 10 ft. The heat exchanger was designed to cool a hot fluid from 250? to 150°F using a cold fluid entering at 100°E. When the exchanger was first placed in service, the hot fluid outlet

Answer 1

Given that a heat exchanger consist of two e-shells connected in series and contains a total of 488 tubes the tubes are 1-in, OD 16 BWG with a length of 10 ft number of tubes N = 488 OD of tubes L = 10 ft heat transfer surface of each tube A_t = pi DL A_t = 3.14 times 1/12 times 10 A_t = 2.618 ft^2 D = 1/12 L = 10 pi = 3.14 total heat transfer surface A = NA_t = 488 times 2.618 A = 1278 ft^2 because A_t = 2.618 hot fluid outlet temperature T_2h = 130 degree F cold fluid temperature rise Delta T_c = mh (ph (T_1h - T_2h)/m_c cp_c = 130000 times 0.55 times (250 - 130)/(0.66 times 190000) = 130000 times 0.55 (120)/(0.66 times 190000) Delta T_c = 82.1 degree F cold fluid temperature T_c2 = T_c1 + Delta T_c = 100 + 82.1 because T_c1 = 100 = 182.1 degree f we assume the flow is counterflow design LMTD = Delta T_1 - Delta T_2/ln (Delta T_1/Delta T_2)