Engineering, 19.09.2019 00:30 leannehounschell
Ayoung engineer is asked to design a thermal protection barrierfor a sensitive electronic device that might be exposed toirradiation from a high-powered infared laser. having learned as astudent that a low thermal conductivity material provides goodinsulating characteristics, the engineer specifies use of ananostrutured aerogel, characterized by a thermal conductivity ofka = 0.005 w/m-k, for the protective barrier. the engineer'sboss questions the wisdom of selecting the aerogel because it has alow thermal conductivity. consider the sudden laserirradiation of (a) pure aluminum, (b) glass, and (c) aerogel. the laser provides irradiation of g = 10x10^6 w/m^2. theabsortivities of the materials are alpha = 0.2, 0.9, and 0.8 for the aluminum, glass, andaerogel, respectively, and the initial temperature of the barrieris ti = 300 k. explain why the boss is concerned. hint: all materials experience thermal expansion (or contraction), andlocal stresses that develop within a material are, to a firstapproximation, proportional to the local temperature gradient. kglass = 1.4 w/m-kkaluminum = 237 w/m-k
Answers: 1
Engineering, 03.07.2019 14:10
If the thermal strain developed in polyimide film during deposition is given as 0.0044. assume room temperature is kept at 17.3 c, and thermal coefficient of expansion for the film and the substrate are 54 x 10^-6c^-1 and 3.3 x 10^-6c^-1respectively. calculate the deposition temperature.
Answers: 3
Engineering, 04.07.2019 18:10
Aloaded platform of total mass 500 kg is supported by a dashpot and by a set of springs of effective stiffness 72 kn/m. it is observed that when the platform is depressed through a distance x = 12.5 cm below its equilibrium position and then released without any initial velocity; it reaches its equilibrium position in the shortest possible time without overshoot. find the position and velocity of the loaded platform 0.10 sec. after its release. if a further load of 400 kg is added to the platform, find, i) the frequency of damped vibrations, and i) the amplitude of vibration after 2 complete oscillations, given that the initial amplitude is 15 cm.
Answers: 1
Engineering, 04.07.2019 18:10
An air conditioning system consist of a 5 cm diameter pipe, operating at a pressure of 200 kpa. the air initially enters the pipe at 15°c with a velocity of 20 m/s and relative humidity of 80%. if the heat supply throughout the process is 960 w, determine the relative humidity and the temperature at the outlet
Answers: 3
Engineering, 04.07.2019 18:20
Air is compressed isentropically from an initial state of 300 k and 101 kpa to a final temperature of 1000 k. determine the final pressure using the following approaches: (a) approximate analysis (using properties at the average temperature) (b) exact analysis
Answers: 1
Ayoung engineer is asked to design a thermal protection barrierfor a sensitive electronic device tha...
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