Interstage cooling is used to reduce the compression work required in a multistage compressor of a helium cooled nuclear reactor. in one such cooler, 2.5 kg/s of helium at 2.5 bar is cooled from 400 k to 310 k by 5 kg/s of cooling water at 300k. it is proposed to have a single pass of helium through a in, 18 gage cooper tubes at a velocity of 30 m/s, with the water in counterflow on the shell side. if the shell side heat transfer coefficient is 8000 w/m2k, determine the number of tubes required and the exchanger. also calculate the helium pressure drop