Problem: An oven door consists of a layer of asbestos sandwiched between a layer of steel on the inner surface and a layer of wood on the outer face. The thickness of the steel is 20mm and that of the wood 12mm. The adhesive used to bond the wood to the asbestos has a maximum safe working temperature of 93 degrees C(when bonded to the wood). The temperature of the inside surface of the door is 537 degrees C and that of the outside 15.5 degrees C. Determine the minimum allowable thickness of asbestos, ignoring the thickness and resistance of the adhesive.
Assue the following thermal conductivities:
k-steel = 41.5W/mK, k-asbestos = 0.19w/mK, k-wood = 1.9 W/mK
Not sure how to approach the question. Where do I begin?© BrainMass Inc. brainmass.com October 24, 2018, 6:07 pm ad1c9bdddf
By Fourier's law:
qx" = -k dT/dx
Now we have for all three materials:
qx" = ...
Solution includes formula's and calculations and directions for solving for he minimum width of the asbestos.
Rankine Cycle Problem
Rankine Cycle Problem. See attached file for full problem description.
A supply of geothermal hot water is to be used as the energy source in an ideal Rankine cycle, with R-134a as the cycle working fluid. (See the diagrams below) Saturated vapor R-134a leaves the boiler at a temperature of 85°C, and the condenser temperature is 40°C. Calculate the heat transfers in kJ/kg at the boiler and condenser.
Calculate the work in kJ/kg at the pump and turbine thermal efficiency of this cycle