Engineering, 06.10.2019 11:00 kcopeland210
The boiling temperature of nitrogen at atmospheric pressure at sea level (1 atm pressure) is −196°c. therefore, nitrogen is commonly used in low-temperature scientific studies, since the temperature of liquid nitrogen in a tank open to the atmosphere will remain constant at -196°c until it is depleted. any heat transfer to the tank will result in the evaporation of some liquid nitrogen, which has a heat of vaporization of 198 kj/kg and a density of 810 kg/m3 at 1 atm. consider a 4-m-diameter spherical tank that is initially filled with liquid nitrogen at 1 atm and − 196°c. the tank is exposed to 20° c ambient air and 55 km/h winds. the temperature of the thin-shelled spherical tank is observed to be almost the same as the temperature of the nitrogen inside. disregarding any radiation heat exchange, determine the rate of evaporation of the liquid nitrogen in the tank as a result of heat transfer from the ambient air if the tank is (a) not insulated, (b) insulated with 5-cm-thick fiberglass insulation (k =0.035 w/m·k), and (c) insulated with 2-cm-thick superinsulation that has an effective thermal conductivity of 0.5 w/m·k.
Answers: 1
Engineering, 04.07.2019 18:10
At 12 noon, the count in a bacteria culture was 400; at 4: 00 pm the count was 1200 let p(t) denote the bacteria cou population growth law. find: (a) an expression for the bacteria count at any time t (b) the bacteria count at 10 am. (c) the time required for the bacteria count to reach 1800.
Answers: 1
Engineering, 04.07.2019 18:10
Courses that are developed by subject matter experts, internal or extemal to the college or university. these programs are marketed by the school (clo2) marks a)-vocational schools b)-vendor training c)-colleges & universities d)-continuing education programs
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Engineering, 04.07.2019 18:20
Asimple rankine cycle uses water as the working fluid. the water enters the turbine at 10 mpa and 480c while the condenser operates at 6 kpa. if the turbine has an isentropic efficiency of 80 percent while the pump has an isentropic efficiency of 70 percent determine the thermal efficiency
Answers: 1
Engineering, 04.07.2019 19:10
Agas contained within a piston-cylinder assembly e end nation about same energy states, 1 and 2, where pi 10 bar, v undergoes two processes, a and b, between the sam 0.1 m3, ui-400 kj and p2 1 bar, v2 1.0 m2, u2 200 kj: process a: process from 1 to 2 during which the pressure- volume relation is pv constant process b: constant-volume process from state 1 to a pressure of 2 bar, followed by a linear pressure-volume process to +20 0 state 2 kinetic and potential energy effects can be ignored. for each of the processes a and b, (a) sketch the process on p-v coordinates, (b) evaluate the work, in kj, and (c) evaluate process the heat transfer, in kj
Answers: 2
The boiling temperature of nitrogen at atmospheric pressure at sea level (1 atm pressure) is −196°c....
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