Discussion Overview
The discussion revolves around the concept of characteristic length in the context of natural convection from a hollow cylindrical object, specifically a thermal circuit involving a vertical hot plate shaped like a DVD. Participants seek clarification on how to define the characteristic length for calculating the Grashoff number and the convection coefficient.
Discussion Character
- Exploratory
- Technical explanation
- Debate/contested
Main Points Raised
- One participant inquires whether to use the outer diameter (OD), inner diameter (ID), or the average of both as the characteristic length for their thermal circuit.
- Another participant requests a sketch to better understand the problem setup.
- A different participant describes their scenario involving a hollow, isothermal cylinder and seeks to calculate the convection coefficient, emphasizing the need for the characteristic length.
- One response suggests using the largest length scale of the fluid for the characteristic length, depending on the heat source's location, and mentions the possibility of nondimensionalizing governing equations to determine the proper length.
- Another participant points out that the cylinder itself is the heat source due to copper losses in a cylindrical winding.
Areas of Agreement / Disagreement
Participants express differing views on how to define the characteristic length, with no consensus reached on the appropriate choice. The discussion remains unresolved regarding the best approach to determine the characteristic length in this context.
Contextual Notes
Participants have not fully defined the assumptions regarding the heat source's location or the flow characteristics, which may influence the choice of characteristic length. There is also a lack of clarity on the governing equations relevant to the problem.