Avolcanic plume puts ash into the atmosphere to altitude of 1m. the characteristic ash particle is a sphere with a diameter of 40 um and has a density of 1000 kg/m^3. consider a single ash particle in isolation that is travelling vertically at its terminal velocity (i. e. no acceleration). assume the density and kinematic viscosity of the air are independent of altitude and is given ,ρ=07kg/m3 and v= 1.5 x 10° m2/s. the drag coefficient is given by stokes' relation: cd =24/re. which of the following answers is closest to the length of time it takes for the particle to settle to the ground? a) 2 hours b) 53 hours c) 33 hours d) 21 hours

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?

Athin walled concentric tube exchanger is used to cool engine oil from 160°c to 60°c with water that is available at 25°c acting as a coolant. the oil and water flow rates are each at 2 kg/s, and the diameter of the inner tube is 0.5 m and the corresponding value of the overall heat transfer coefficient is 250 w/m2. oc. how long must the heat exchanger be to accomplish the desired cooling? cpwater=4.187 kj/kg-candcpengine el=2.035 kj/kg·°c, oil . 120]

What is creep? what is stress relaxation?