heat exchangers

Enumerate the three modes by which heat can be transferred from one place to another. Which is the
slowest of all ?
How do you define the thermal conductivity of a material ?
What do you understand by the terms ‘convective heat transfer co-efficient’ and ‘overall heat transfer
co-efficient’.
Derive an expression for heat loss in kJ/m 2 -hr through a composite wall of layers (i) without considering
convective heat transfer co-efficients and (ii) considering the convective heat transfer co-efficients.
Classify the heat exchangers according to the flow directions of fluid and give few examples of each in
actual field of application.