
#1
Dec2312, 04:14 PM

P: 1

This question is from my textbook: Thermodynamics an Engineering Approach 7ed SI Units, cengel. It is problem 10129 and I can't seem to figure it out.
Design the condenser of a steam power plant that has a thermal efficiency of 40 percent and generates 10 MW of net electric power. Steam enters the condenser as saturated vapour at 10kPa, and it is to be condensed outside horizontal tubes through which cooling water from a nearby river flows. The temperature rise of the cooling water is limited 8 degC, and the velocity of the cooling water in the pipes is limited to 6 m/s to keep the pressure drop at an acceptable level. From prior experience, the average heat flux based on the outer surface of the tubes can be taken to be 12,000 W/m^2. Specify the pipe diameter, total pipe length and the arrangement of the pipes to minimize the condenser volume. I found h4 and h1 from the steam property tables and I know that the surface area will be dependent on the heat flow out of the system divide by the heat flux per m^2 but cant seem to put it all together any help is appreciated. 



#2
Dec2312, 04:35 PM

Mentor
P: 10,864

What are h4 and h1?
Based on your numbers, you can calculate the steam flow (in m^3/s) and the total surface of the pipes. For a pipe with diameter d and length l, you can calculate the surface of this pipe and the power  and find a constraint for the length (or diameter) based on the flow velocity and maximal temperature difference. This just leaves the question how exactly you want to design the whole thing. 


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