Conductive thermal resistance is proportional to (with t = thickness, ρ = density, and A = cross-sectional area normal to heat flow) ?
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Answer: D. All A., B. & C.
Explanation
Conductive thermal resistance increases with material thickness and decreases with cross-sectional area and thermal conductivity. Fourier law shows thermal resistance is directly proportional to wall thickness and inversely proportional to area. Material density relates indirectly to thermal conductivity, making all listed geometric factors affect conductive resistance. Thermal resistance measures a material resistance to heat flow under steady-state conduction conditions. Thicker insulation layers increase resistance, reducing heat transfer through building walls and industrial pipes. Larger cross-sectional areas provide more pathways for heat flow, thereby lowering overall conductive thermal resistance.
Pipeline insulation sizing requires calculating thermal resistance to prevent freezing and maintain fluid temperatures. Electronic cooling heatsink designs maximize cross-sectional area to enhance conductive heat dissipation away from chips. Architects select wall thicknesses based on thermal resistance requirements to improve building energy efficiency. Stating that resistance is proportional only to thickness ignores the inverse effect of cross-sectional area. Focusing solely on inverse area leaves out the critical role of material thickness in conduction calculations. Neglecting material density and conductivity variations would yield inaccurate thermal resistance predictions in walls.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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