Question

Hot water with the mass flow rate of 3 kg/s and temperature of 90 C enters a 2 inch copper pipe with the length of 3 m. The pipe is exposed to cold air at the constant temperature of 1C and wind velocity is 5 m/s. Find the outlet temperature of water and the rate of heat loss from the pipe. P2: 20%

Answer 1

Toi f Прыретво an evetuated at bulk mean temperaturen Internal pape flow Tw=constant wall (u temperature oTo We don't know the exit temperature (To) To-Titto So, we cannot determine To , which is the temperature at which properties are to be evaluated. and So, evaluate properties of water at inlet temperature Calculation if necessary using the propertics at the eramated bulk sean temperature, At 90°C. p = 964045 kg/m² M 3.07058104 kg/m3 4074.7 JlIgl Pr repeat the 1.8506 K 0.67606 W/mk number (Re) 20= 0.854m Calculate Reynolds me PAV 20= 0.0508m v 3Kg/5 1.5347 m/s 964: 45x Trapx 050P 9641458 1,53474 0.0508 244883 M 3.0705 X 10-4 Re > Reia e 2300 > Flow is TURBULENT Re = vvd

by n= Calculate Convective heat transton Coefficient (6) wang Dittus Belter correlation Nuo 0.023 Rear Pan I for cooling Nu = hd 0.023 (Re) && P h 0.023 (2448*3)*% (1,8506)09 K x 0.6 to 6 0.0508 76 76.32 W/m²K Calculate ent temperature CO) To-To-Cas-Ti) exp h adh ( m C -7476.32 TX 0.0508% 3 =1C-(1-90) eap B x 4074.7 67.407°C difference (Om ) man temperature To-To 90-67.407 Calculate leganithonic Om ls (Isole los ( - 67. 407 1- 90 Is-li - 77.1557°C Calculate rate of heat loss (Q) Q = h As Om 7476.237 2X0.0508 x 3y77.1557 Q -276.175 kW