Summer2022-VM335 Homework 6
机械工程作业代写 where x is the distance measured from the tube inlet.Fluid at an inlet temperature Tm,i flows through the tubeat a rate of m.
8.7
Velocity and temperature profiles for laminar filow in atube of radius r, = 10 mm have the form
with units of m/s and K, respectively. Determine thecorresponding value of the mean (or bulk) temperature.Tm, at this axial position.
8.12 Water enters a tube at 27°C with a flow rate of 450kg/h. The heat transfer from the tube wall to thefluid is given as q’s(W/m) = ax, where the coefficient ais 20 W/m2 and x (m) is the axial distance from the tubeentrance. 机械工程作业代写
(a) Beginning with a properly defined differential control volume in the tube, derive an expression for thetemperature distribution Tm(x) of the water.
(b) What is the outlet temperature of the water for aheated section 30 m long?
(c)Sketch the mean fluid temperature, Tm(x), and the(c)tube wall temperature, Ts(x), as a function of dis.tance along the tube for fully developed and devel-oping flow conditions.
(d)What value of a uniform wall heat filux, q”s(insteaddof q’s = ax), would provide the same fluid outlettemperature as that determined in part (b)? For thistype of heating, sketch the temperature distribu-tions requested in part (c).
8.23 机械工程作业代写
An experimental nuclear core simulation apparatusconsists of a long thin-walled metallic tube of diameterD and length L, which is electrically heated to producethe sinusoidal heat flux distribution
where x is the distance measured from the tube inlet.Fluid at an inlet temperature Tm,i flows through the tubeat a rate of m. Assuming the flow is turbulent and fully developed over the entire length of the tube, developexpressions for:
(a) the total rate of heat transfer, q, from the tube to thefluid; 机械工程作业代写
(b) the fluid outlet temperature, Tm,0
(c) the axial distribution of the wall temperature, Ts(x);and
(d) the magnitude and position of the highest walltemperature.
8.26 Engine oil filows through a 25-mm-diameter tube at arate of 0.5 kg/s. The oil enters the tube at a temperatureof 25°C, while the tube surface temperature is main-tained at 100°C.
(a) Determine the oil outlet temperature for a 5-m andfor a 100-m long tube. For each case, compare thelog mean temperature difference to the arithmeticmean temperature difference.
9.4 机械工程作业代写
To assess the efficacy of different liquids for cooling bynatural convection, it is convenient to introduce a fure
of merit, FN, which combines the influence of all perti-nent fluid properties on the convection coefficient. If theNusselt number is governed by an expression of the form.NuL~ Ran, obtain the corresponding relationship between FN and the fluid properties. For a representative value of n = 0.33, calculate values of FN for air (k = 0.026W/m·K，B = 0.0035 K-1,v = 1.5 X 10-5m2/s, Pr =0.70),water (k = 0.600 W/m·K，β = 2.7 × 10-4K-1,v = 10-6m/s，Pr = 5.0), and a dielectric liquid(k = 0.064 W/m·K，β = 0.0014 K-1,v= 10-6 m2/s.Pr = 25). What fluid is the most effective cooling agent?
9.18
During a winter day, the window of a patio door with aheight of 1.8 m and width of 1.0 m shows a frostline near its base. The room wall and air temperaturesare 15°C.
(a) Explain why the window would show a frost layerat the base rather than at the top.
(b) Estimate the heat loss through the window due tofree convection and radiation. Assume the windowhas a uniform temperature of o°C and the emissiv-ity of the glass surface is 0.94. If the room has elec-tric baseboard heating, estimate the correspondingdaily cost of the window heat loss for a utility rateof 0.18 $/kw.h.
更多代写：加拿大宏观经济代考 gre代考被抓 加拿大网课代上推荐 留学Essay代写推荐 金融类学术论文代写 学术论文翻译
