What is the standard direction of heat flow?
The direction of heat flow in a small element within a solid only depends on the temperature of its neighboring elements. Heat within the solid will flow from hot to cold. It will cheerfully flow downward if it is cooler down there.
What is heat flux in thermodynamics?
Heat flux (W/m2) is the rate of thermal energy flow per unit surface area of heat transfer surface, e.g., in a heat exchanger. Heat flux is the main parameter in calculating heat transfer. A generalized classification distinguishes between heat fluxes by convection, heat conduction, and radiation.
What is the symbol for heat flux?
Heat flux or thermal flux, sometimes also referred to as heat flux density, heat-flow density or heat flow rate intensity is a flow of energy per unit of area per unit of time. In SI its units are watts per square metre (W/m2)….
| Heat flux | |
|---|---|
| Heat flux through a surface. | |
| Common symbols | |
| SI unit | W/m2 |
| Other units | Btu/(h⋅ft2) |
Is heat flow in positive or negative?
Heat, presented by the symbol Q and unit Joule, is chosen to be positive when heat flows into the system, and negative if heat flows out of the system (see Figure 17.1). Heat flow is a results of a temperature difference between two bodies, and the flow of heat is zero if TS = TE.
Can you have negative heat flux?
it depends in which context, a heat flux is defined w.r.t. a “normal vector” so a negative heat flux is onlyshowing that the flow direction is opposite to the normal vector direction.
What does positive heat flux mean?
Sensible and latent heat fluxes cannot be directly measured, but they can be calculated using the temperature and moisture content of the air at the Earth’s surface and just above it along with the wind speed just above the surface. A positive sensible heat flux means heat is flowing from the atmosphere to the surface.