# PS_90 - 315C, and its surface temperature is suddenly...

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ChBE421 Problem Set # 9 Fall 2009 1. A shell and tube heat exchanger having two shell passes and eight tube passes is used to heat kerosene from 20 °C to 75 °C. The kerosene (C P = .49 kcal/kg °C) enters at a rate of 950 kg/hr. Water at 98 °C flows through the shell side at a rate of 675 kg/hr. The overall heat transfer coefficient is 135 kcal/m 2 hr °C. Find the area required for the heat exchanger. **NOTE: For this chart: 1. ‘S’ is the value ‘Y’ from lecture 2. ‘R’ is the value ‘Z’ from lecture 3. ‘T’ corresponds to the shell temperature (‘T S ‘ in lecture) 4. ‘t’ corresponds to the tube temperature (‘T t ‘ in lecture) 2. Steam at 250 psi, 625 °F flows through a steel pipe (4.3" OD, 2.8" ID) at a rate of 1200lbm/hr. Estimate the value of h on the inside surface. 3. A very long rectangular aluminum bar has a cross-section 8 cm x 14 cm. The bar is initially at

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Unformatted text preview: 315C, and its surface temperature is suddenly reduced to 75 C: How long will it take for the center to reach 120 C? What is the temperature of the surface of the bar at that point? 4. The aluminum bar of problem 3 is initially at 240 C. It is placed in air (T = 25 o C) with an outside heat transfer coefficient of h o = 21 kcal/hr m 2 K. How long will it take its center to reach 135 C? 5. An object of a specific shape with negligible internal resistance to heat transfer requires a certain time to cool to a specific temperature. How does the cooling time change if: (i) the thermal conductivity of the solid is tripled; (ii) the external heat transfer coefficient is doubled. Cylinder Slab...
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## This note was uploaded on 03/18/2010 for the course CHBE 421 taught by Professor 1` during the Spring '10 term at University of Illinois, Urbana Champaign.

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PS_90 - 315C, and its surface temperature is suddenly...

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