Chemical Engineering 3453 University of Utah Fall 2007 Homework Assignment 9 Prof. Geoff Silcox Due 2007 October 26 at the beginning of class To ensure that you receive full credit for your solutions, write out all equations in symbolic form, give numerical values for all variables and constants in the equations, and write answers to conceptual problems in complete sentences. If you use Excel, MATLAB, or other software to solve equations, attach a printout that includes results and all equations. Problem 1.0 The following questions are all based on the article by Rajiv Mukherjee (R. Mukherjee, "Effectively Design Shell-and-Tube Heat Exachangers," Chemical Engineering Progress, February 1998, p. 21-37). a) What is the chief advantage of a U-tube heat exchanger? b) What is the chief disadvantage of a U-tube heat exchanger? c) List the key design data needed before heat exchanger design can begin. d) With regard to tube-side design, how does h (the heat transfer coefficient) vary with µ (viscosity)? e) How does h vary with k (thermal conductivity)? f) Show that the tube-side pressure drop will increase with the number of tube passes cubed. g) Which tube diameters are most popular in the chemical process industry? h) What is the most common shell type? i) What tube layout pattern is commonly used for dirty shell-side services? j) What is the minimum tube pitch recommended by TEMA for a triangular tube pattern? k) What is the minimum tube pitch recommended by TEMA for a square tube pattern? l) Define baffle spacing and comment on its importance in shell and tube heat exchanger design. m) Define baffle cut. n) Mukherjee states that "an important limitation for 1-2 shells (one shell pass and two or more tube passes) is that the outlet temperature of the cold stream cannot exceed the outlet temperature of the hot stream." Why? o) What causes temperature profile distortion? Problem 2.0 Problem 11.10, p. 709 of text. Approximate answer: 30 W/(m2 K).Problem 3.0 In a coal-fired power plant, steam leaves a turbine and is piped to a condensing unit. After condensation occurs, it is further desired to cool the (distilled) water by means of a shell-and-tube exchanger. The water enters the heat exchanger at 110 F with a flow rate of 170,000 lb/hr. The heat will be transferred to raw water from a nearby river. The raw water is available at 65 F and the mass flow rate is 150,000 lb/h. It is proposed to use a heat exchanger that has a 17 and 1/4-in-ID shell and 3/4-in-OD, 0.049-in-wall tubes that are 16 ft long. The tubes are laid out on a 15/16-in triangular pitch. The tube fluid will make two passes. There are 238 tubes. Fouling can be neglected on both the shell and the tube side as can the resistance of the tube wall. The shell contains baffles that are spaced 1 ft apart. There is one shell pass. Determine the outlet temperature of the distilled water and the pressure drop for each stream. Note that the distilled water should be run through the shell. To evaluate properties in the shell correlation, assume a distilled water outlet temperature of 90