EML4147C HW3

# EML4147C HW3 - Homework 11.32) A single-pass, cross-flow...

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Homework 11.32) A single-pass, cross-flow heat exchanger uses hot exhaust gases (mixed) to heat water (unmixed) from 30 to 80 °C at a rate of 3 kg/s. The exhaust gases, having thermophysical properties similar to air, enter and exit the exchanger at 225 and 100 °C, respectively,. If the overall heat transfer coefficient is 200 W/m 2 ∙K, estimate the required surface area. 11.50) The chief engineer at a university that is constructing a large number of new student dormitories decides to install a counterflow concentric tube heat exchanger on each of the dormitory shower drains. The thin-walled copper drains are of diameter D i = 50 mm. Wastewater from the shower enters the heat exchanger at T h,i = 38 °C while fresh water enters the dormitory at T c,i = 10 °C. The wastewater flows down the vertical wall of the drain in a thin, falling film , providing h h = 10,000 W/m 2 ·K. (a) If the annular gap is d = 10 mm, the heat exchanger length is L = 1 m, and the water flow rate is m = 10 kg/min, determine the heat transfer rate and the outlet temperature of the warmed

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## This note was uploaded on 02/15/2012 for the course EML 4147C taught by Professor Abbitt during the Spring '11 term at University of Florida.

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EML4147C HW3 - Homework 11.32) A single-pass, cross-flow...

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