# Problem 15-2 - Example 15-2 A shell-and-tube heat exchanger must be designed to heat 2.5 kg/s of water from 15 to 85oC Hot engine oil c p = 2350

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Example 15-2 A shell-and-tube heat exchanger must be designed to heat 2.5 kg/s of water from 15 to 85 o C. Hot engine oil ( o 2350J/kg C p c = ) at 160 o C enters the shell side of the exchanger. The oil provides a heat coefficient of 400 W/m 2 K on the outside of the tubes. Ten tubes pass the water through the shell. Each tube is thin-walled, of diameter D= 25 mm, and makes eight passes through the shell. If the oil leaves at 100 o C, what is its flow rate? How long must each tube be? Oil 160 Oil 100 °C Water 15 °C Water 85 °C One Pass (8 tube passes in total) Shell Side (one shell pass) One Tube (9 other tubes not shown ) Solution: () ,, , H pC Co Ci Qm c T T =− ± ± o kg J 2.5 4181 85-15 C sk g K ⎛⎞ = ⎜⎟ ⎝⎠ 5 7.317 10 W ,,, H pH Hi Ho c T T ± ± H pH Q m cT T = ± ±

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For the oil , o J 2350 kg C pH c = () 5 o o 7.317 10 W kg 5.19 s J 2350 160 100 C kg C H m × == ⎛⎞ ⎜⎟ ⎝⎠ ± , LM cf QU A F T =∆ ± io ln 11 1 2 o i D D UA h A kL h A π =+ + In this case A A DD 1 Uh h To find h i Re D D ρ µ = V 2 4 D mA ρπ ± 2 44 Re D mD m ππ ±± The total water flow rate is 2.5 kg/s. Dividing this among 10 tubes give a per tube flow rate of 0.25 kg/s 6 kg 40 . 2 5 s Re 23,234 kg 0.025m

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## This homework help was uploaded on 04/07/2008 for the course MANE 4010 taught by Professor Kaminski during the Spring '08 term at Rensselaer Polytechnic Institute.

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Problem 15-2 - Example 15-2 A shell-and-tube heat exchanger must be designed to heat 2.5 kg/s of water from 15 to 85oC Hot engine oil c p = 2350

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