Question

3.2A horizontal 4-inch outer diameter (OD) tube is surrounded by saturated steam at 2 psia. The tube is maintained at 64°F. What is the average heat-transfer coefficient. Assume filmwise condensation and laminar flow. Use SI units during your calculations. (12) NB: Table for properties for saturated steam: Properties of saturated water Volume Expansion ent Enthalpy Specific Thermal Prandt en Dynamic Density C ity Nu Hea me Pressure Vaporization emp. P kPa Liquid Vapor A kkg Liquid Vapor Liquid Vapor Liquid Vapor Liquid Vapor Liquid 1.00-0.068 x 10 11.2 1.00 0.015 x 10 0.561 13.5 0.0171 0.0173 1.519 x 10 0.01 999.8 0.6113 0.8721 999.9 0.0048 2501 2490 421 1854 1857 1.792 x 10 0.922 x 10 0.934 x 10 0.0068 420 0.571 1863 1.00 0.195 x 10 1.00 0.247x 10 0.973 x 10 20 2.339 99яо 0.0173 2454 4182 1867 0.598 0.0182 1.002 x 10 7.01 3.169 0.0231 2442 4180 1870 0.607 0.0186 0.891 x 10 0.987 x 10 6.14 25 997.0 0.623 0.0192 0.720 x 10 1.016 x 10% 0.631 0.0196 0.653 35 1.00 0.337 x 10 5.628 994 0 0.0397 2419 4178 1880 4.83 4.32 100 0.377 x 10- 1.031 x 10-1 40 7,384 992.1 0.0512 2407 4179 1885 10- 93 2383 4181 0 644 0.0204 0647 10 1908 0.649 0.0208 0.504 1062 x 10 1.00 0.451 x 10- 1.00 0.484 x 10- 12.35 овя 1 3.55 0,0831 1900 55 15.76 985.2 0.1045 2371 4183 10- 3.25 1.077 x 10-5 4197 2346 0659 0.0216 0433 x 10- 1110 1o- 0.663 0.0221 0.404 x 10 1.126 x 10 2.55 1.00 0.578 x 10 d.667 0.0225 0.378 x 10 1.142 x 10 100 9 548 0.1614 1926 70 31.19 977.5 0.1983 2334 4190 1936 2321 2.38 1.00 0.607 x 10 4193 75 0.2421 1948 2.08 0,673 0,0235 0.333 x 10- 1.176 x 1o- 0.675 0.0240 0.315 x 10- 1.00 0,670 x 10- 1.00 0.702 x 10- 57.83 968.1 0.3536 0.4235 2296 4201 1977 1.193 x 10- 70.14 965.3 2283 4206 1993 1.96 967 9 1 227 x 10- 1.75 1.00 0.750 x 10-* 1.00 0.798 x 10- 100 0.858 x 10 0.679 0.0251 0.282 x 10 0.682 0.0262 0.255 x 10 0.683 0.0275 0.232x 10 1.296 x 10 100 101 33 0.5978 2257 2029 4217 110 143.27 950.6 2230 2071 2120 1.261 x 10- 1.58 1.44 0.8263 4229 120 198.53 943.4 1.121 2203 4244 2145 4286 0.683 0.0301 0.197 x 10 1.365 x 10 1 02 0.970 x 10! 140 361.3 921.7 1,965 2244 1.24 SR8888339289

Answer 1

3.2 Satuoated steann Given 2psia 13 T89 51456 Pa at OD= inch 10.16 cm 3.789 KPa The temparoatuve of satusated steam at this poessure O 1016 m 52.1C is Tube temparoatuoe 64F17-7773

A ssuming filmwise condensat ion & laminar flow 3 ece-e)g heg K h 0.725 - E upieme SY cf Tat Tw Jod TE Te is flm tempasatuoe 2. S2.1+ 178 Jvtotoo ste2 Jos s to sudo Spors 34.95 C

(r-P) 22 e= 994 Kg/m heg=heg o68cCT-T - 2373 K10 JI heg C 4178 JIkg Specific heat at film tem parature T=17.8 C Ta S21C 2475448 31ka heg= Ke O 623 W/mk 072 xIO Kms d o1016 m 994 x9.8x 2475448x O 623 h 0-725 3 O.72X10x 0 (oi6x (52-1-17 8 S026.2 W/m

The average value of heat transfer coefficient is calculated considering the modification to energy balance to include additional energy to cool the film below the saturation temperature , considering the nonlinear temperature profile using h'_fg

as proposed by Rohsenow