ENVE 4105 Lecture Notes - Lecture 4: Mass Flow Rate, Aerogel, Transmittance

• School: Carleton University
• Department: Environmental Engineering
• Course: ENVE 4105
• Professor: Liam O' Brien

Document Summary

Heat transfer through solid (for our purposes)materials (e. g. , through an opaque wall) Heat transfer resulting from air (or other fluids) movement (e. g. , between a wall and the adjacent air) Longwave: h heat transfer between surfaces that can see each other (e. g. , between a cold window and. Heat always transfers from the higher to lower temperature substance. There needs to be a temperature difference between substances for heat transfer to occur. A greater temperature difference causes a heat transfer rate. Examples in building: through walls (insulation, thermal bridging), doors, ground conduction, between rooms. We generally assume that heat transfer through walls is 1-dimensional (in the direction of the surface normal; no heat transfer across a wall) Assume heat transfer is perpendicular to the wall. 1d assumption becomes much less valid when geometry is irregular or low and high-conductivity materials are in parallel. The lower the number the better [see table in ppt] E. g. air is one of the best insulators.