NEM 445 Exam 2 January 9, 2013 • • •
You You have 2 hours to finish the exam. Ceary !rite "o!n a the assum#tions you ma$e. %he fi&ures an" 'onstants you !ou" nee" are a re &iven. 1. (20) Draw the boiling curve and clearly mark the x axis and y axis, mark the
temper temperatur atures es and heat heat trans transfer fer regime regimes. s. What What is the expecte expected d flow flow patter pattern n (drawing of voids and liquid phase) and for the !" condition for a #W$ and %W$& Draw a picture of the void (steam) distribution. ') (30) n the #enntate*s $od %undle !eat +ransfer xperiment bundle, there are - cylindrical rods with outer diameter of /.01- in. +he bundle is surrounded by a square square inconnel can which which is 0.2 in. in one side. side. 3ne of the single single phase flow flow experiments performed at '/// psia showed that the flow velocity in the bundle is '4 ft5s. +he bundle has a power shape defined as6
* in ' h e s
+ (* )-+ av
/
/
7
'.-
'--
/
where q8av 9 2./ kW5ft. •
:ssuming that the inlet temperature is 0;/ o", calculate the clad outside surface temperature at '//./ inch location.
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alculate the frictional pressure drop for the bundle. (:ssume the rods and the can have the same relative roughness as the drawn tubing).
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f the the q8(<)5q8 q8(<)5q8av value is decreased to '.7, how the !"$ margin changes (increase or decrease)&
Constants an" remin"ers +he moody chart you would need is attached. :t
'///./ psia, = 9 2-.17 lbm5ft0, > 9 /.02' lbm5hr ft, gc 9 07.'1 lbm ft5lbf s7,
c p9
'./4'' %tu5lbm o", k 9 /.0' btu5hr ft o", #r 9 c p >5k, +sat 92// o", for turbulent flow, ?u 9 /./70$e/.;#r /.00 ?u9 h x De5k ' kW is 0-'7 %tu5hr 7) (15) "or a #W$ fuel pin with pellet radius of /.';2 in. and fuel radius of /.7'2 in., calculate the maximum linear power in kW5ft that can be obtained from the pellet such that the centerline temperature does not exceed 77// o". +he coolant temperature is 2;2.2 o" and the coolant heat transfer coefficient is 2///./ %tu5hr ft7 o". "uel conductivity6 1.7; %tu5hr ft o" lad conductivity -2./ %tu5hr ft o", the clad thickness is /./772 in. !elium heat transfer coefficient, '/// %tu5hr@ft7@o", the gap thickness is /.//12 in. Constants an" emin"ers6 :ssume the flux depression factor is './
0) (10) "or a boiling water flow in annular flow regime, in 4;'./ psia tube, at a particular region, the thickness of the liquid film on each side of the tube is 0./ in. f the tube flow area is ' f t7, calculate two phase density of the flow for the described flow section which is ' in. tall. Constants an" emin"ers6 / 1 #sia, Af 9 /./7/- ft05lbm, Ag 9 /.41-; ft05lbm, ' feet is '7 inches
-) (20) %riefly answer below questions6 a. Describe the $oss and toute model for the gap heat transfer coefficient. b. Describe how to calculate the wall superheat for the nucleate boiling. c. "or the below figure briefly list the components of pressure drop between points6 a and a*, aB and b, and e and f.
d. 3n the below figure clearly mark the wall and coolant temperatures and the location of single phase heat transfer, subcooled boiling and nucleate boiling regions, sketch the change in void fraction.
