A nonmetal plate (k = 0.05 W/m•K) and an ASME SA-240 stainless steel plate (k = 15 W/m•K) are bolted together by ASTM B21 naval brass bolts. Both plates have a thickness of 38 mm, and the brass bolts are bolted through both plates. The bottom steel plate surface (surface 1) is subjected to a uniform heat flux of 200 W/m2. The top nonmetal plate surface (surface 2) is exposed to convection at an air temperature of 20°C and a convection heat transfer coefficient of 5 W/m2•K. Also, thermal radiation exchange occurs between the upper plate surface and the surrounding surface temperature of 30°C. The emissivity of the plate surface and the bolts is 0.3. The ASME Boiler and Pressure Vessel Code (ASME BPVC.IV-2015, HF-300) limits the maximum use temperature to 260°C for the SA-240 steel
plate. The ASME Code for Process Piping (ASME B31.3-2014) limits the maximum use temperature of B21 bolts to 149°C. Determine whether both ASME codes are being complied with under these conditions
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A nonmetal plate and an ASME SA-240 stainless steel plate are bolted together by ASTM B21 naval brass bolts. The bottom surface is subjected to uniform heat flux. The top surface is exposed to convection and radiation heat transfer. Determine whether the ASME Boiler and Pressure Vessel Code and the ASME Code for Process Piping are being complied.
Assumptions1 Heat transfer is steady. 2 One dimensional heat conduction through the plates. 3 Uniform heat flux on bottom surface. 4 Uniform surface temperatures. 5 No contact resistance at the interface.
Properties The thermal conductivities for the steel plate is given as k1 = 15 W/m•K and for the nonmetal plate as k2 = 0.05 W/m•K.
Analysis The uniform heat flux subjected on the bottom plate surface is transferred by conduction through the plates, and by convection and radiation on the top surface:
where
Combining the equations to solve for T1, T2, and Ti, we have
Solving for the top surface temperature T2 using Eq. (3), yields
Solving for the interface temperature Ti using Eq. (2), yields
Solving for the bottom surface temperature T1 using Eq. (1), yields
DiscussionThe ASME SA-240 stainless steel plate has an average temperature of 203.6°C, which complies with the ASME Boiler and Pressure Vessel Code (ASME BPVC.IV-2015, HF-300) which requires a temperature of less than 260°C. However, the ASTM B21 naval brass bolts are used in a steel plate that its temperature exceeds the maximum use temperature of 149°C required by the ASME Code for Process Piping (ASME B31.3-2014). Another type of bolts should be considered for use under these conditions. For example, the ASTM A193 B8M steel bolts have a maximum use temperature of 538°C (ASME B31.3-2014).
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