Nak (55%/44%), which is an alloy of sodium and potassium, is used to cool fast neutron nuclear reactors. the nak flows at a rate of latex: \dot{m} = 0.8 kg/sm ˙ = 0.8 k g / s through a d=40-mm-diameter tube that has a surface tube at t­m, i = 335 k and exits at an outlet temperature of tm, o =397 k. deter- mine the tube length l and the local convective heat flux at the tube exit.