Electronic components mouted on a flat plate are cooled by convection to the surroundings and by liquied water circulating through a U-tube bonded to the plate. At steady state, water enters the tube at 20 degree C and a velocity of 0.4m/s and exits at 24 degree C with a negligible change in pressure. The electrical components receive 0.5kW of electrical power. The rate of energy transfer by convection from the plate-mounted electronics is estimated to be 0.08 kW. Kinetic and potential engerfy effects can be ignored. Determine the tube diameter, in cm.