Question

To maximize production and minimize pumping costs, crude oil is heated to reduce its viscosity during transportation from a production field. (1) Consider a pipe-in-pipe configuration consisting of concentric steel tubes with an intervening insulating material. The inner tube is used to transport warm crude oil through cold ocean water. The inner steel pipe ks 45 W/m-K) has an inside diameter of Di,1 150 mm and wall thickness t = 20 mm while the outer steel pipe has an inside diameter of Di,2= 250 mm and wall thickness to = ti . Determine the maximum allowable crude oil temperature to ensure the polyurethane foam insulation kp 0.0675 W/m-K) between the two pipes does not exceed its maximum service temperature of Тр, p, max 70°C. The ocean water is at -5°C and provides an external convection heat transfer coefficient of he 500 W/m2-K. The convection coefficient associated with the flowing crude oil is hi= 450 W/m2-K (2) It is proposed to enhance the performance of the pipe-in-pipe device by replacing a thin ta 10 mm) section of polyurethane located at the outside of the inner pipe with an aerogel insulation material ( ka 0.012 W/m-K). Determine the maximum allowable crude oil temperature to ensure maximum polyurethane temperatures are below Тр. 70°C max Physical Properties Mathematical Functions Step 1 Your answer is correct. Determine the convection heat transfer resistance on the inside of the pipe per unit length, in m-K/W. 1,corv m.K/W 0.004716 Attempts: 2 of 3 used Step 2 Your answer is correct. Determine the conduction resistance of the polyurethane per unit length without the aerogel, in m-K/W. R'1,cord.p m-K/W 0.647 Attempts: 2 of 3 used Step 3 Your answer is incorrect. Determine the conduction resistance of the polyurethane per unit length when aerogel is used, in m-K/W. R',cord.pae m-K/W i 1.328 Attempts: 1 of 3 used Save for Later Check Answer Step 4 Determine the maximum crude oil temperature if no aerogel is used, in °C Т. °C i Attempts: 0 of 3 used Save for Later Check Answer Step 5 Determine the maximum crude oil temperature if aerogel is used, in °C. Т., ае co, ae °C i eTextbook and Media

Answer 1

Pipe Jnsulaon K = pipe (STeel) Di2z25amm Di= 15om m t20 mm 0 Rconvectio 450x XDxL O.O041 450x AX0.15 X1 Payure thane Cnduction Resiskan ce (4m) Diz/2 R'tcond p P = 2LKP 2 K LKP 25 75+20 n (m-K O. 647 W 2xR x 1X0.675 125mm 2omm I 75mmir Y2 ln/Y2 /25 Inner Pipe 75 +20t1 2LK 2*RX X0.á 675 6. 4I a erogel

Outer pipe Conduction. Jesi'stance 12520 2 5 Re O O o o 525mK W 2.7LK inner pipe Res is kance Ri= ln(75+20 구5 m k W O ooo83 2RXX 5 outer conduction Resic^an ce Convection Rocom hoDoL 5oXX0 2x1 hoAo mK W O-90236 Tp-700c Tmax Ricontr Rin.cond Recondp Rocind Ro canvec Hence T0-(-5) Tmax 구。 O(4 O.000525 + o a o23 6 O.Go4 o-00003 Tmax 7 HOIE2 115.4 5.54x3 Thaek 70-6400

ln(1o5 95 Rcondu aeroge 324 mk W 2*x 1Xo 01 2 o C Tmax Rgconr Rocond Rincond. Rcand.aerqal Kpoly Cυηy. Rinconv 70-(-5) Tmax 70 O 64to.00o52.5 0-00 23 O.0041t0.aa0936 +1326 Tmax 15:41 T-33 Tmax 223.9C