1. Refrigerant-134a is being transported at 0.1 kg/s through a Teflon tube of inside diameter Di = 25 mm

is to maximize qc" while maintaining the heat sink at an acceptable temperature. Subject to prescribed and outside diameter Do = 28 mm, while atmospheric values of L = 12 mm and Tm,i = 290 K and the constraint that Ts,max 50°C, explore the effect on qc" of variations in heat sink design and operating conditions.

2. One way to cool chips mounted on the circuit boards of a computer is to encapsulate the boards in metal frames that provide efficient pathways for conduction to sup- porting cold plates. Heat generated by the chips is then dissipated by transfer to water flowing through pas- sages drilled in the plates. Because the plates are made from a metal of large thermal conductivity (typically aluminium or copper), they may be assumed to be at a temperature, Ts,cp. air at V = 25 m/s and 300 K is in cross flow over the tube. What is the heat transfer per unit length of tube to Refrigerant-134a at 240 K?