Write down a mathematical expression for the thermal resistance for a cylindrical tube wall that separates the inner and outer fluid in a double-pipe heat exchanger. How could this resistance be reduced?

Plot schematically the tensile stress versus strain curves for a typical thermoplastic material at a temperature below its glass transition temperature (tg and at a temperature above its tg, respectively. do the same for a typical thermosetting material. list in a table any differences or similarities between the two materials at t> tg and t < tg, respectively, and relate them to the structures of the two types of polymers