Overall Heat Transfer. Heat is first transferred from the hot fluid to the wall by convection through the wall by conduction and from the wall to the cold fluid again by convection. Ce n т t.
H in is heat transfer coefficient for fluid flowing in pipe and h air is heat transfer coefficient due to air flowing outside the pipe. E wall thickness in m. U overall heat transfer coefficient in wm2c.
There are thus three heat transfer operations that need to be described.
Terminology of heat exchanger for question 7. A heat transfer surface area m 2 ft 2 u overall heat transfer coefficient w m 2 c btu hr ft 2 f δt lm logarithmic mean temperature difference c f from this equation it can be seen that the u value is directly proportional to q the heat transfer rate. Where k pipe k insulation are thermal conductivity of pipe and insulation. Ce n т t.