Can Heat Transfer Coefficient Be Negative?

In addition, with traditional definition of convective heat transfer coefficient, which is based on the temperature difference of an interior surface and room air, the coefficient value can be negative.

What does negative heat transfer coefficient mean?

In case of constant wall temperature, using adiabatic wall temperature as reference temperature can result in negative heat transfer coefficient, which means the heat flux has a different direction with the defined driving temperature difference.

Can you have a negative heat transfer rate?

The minus sign is there because the rate of heat flow is always negative—heat flows from the side at higher temperature to the one at lower temperature, not the other way around.