In: Physics
An electrical machine dissipates 2.5 kW. All cooling of the unit takes place through one exposed surface, measuring 120 mm × 190 mm. All other surfaces of the unit are insulated. 50 fins are mounted on the exposed surface. The fins are made of aluminium alloy 2024-T6, and each one measures 120 mm × 2 mm in cross-section and 80 mm in length (normal to the surface they are mounted on). The fins and base surface are exposed to fan-driven air at 15°C with a convection heat transfer coefficient of 60 W m–2 K–1. Calculate the steady-state temperature of the power supply’s exposed surface. (b) To increase the heat transfer rate through a set of fins, without changing the base temperature, would it be more effective to increase the number of fins by 20%, or to increase the length of each fin by 20%? Explain your answer.