Hot air flowing through a counter-flow double-pipe heat exchanger at a rate of 0.5 kg/s must be cooled from 250°c to about 100°c by water in the annulus initially at 15°c. the thermal resistance of the heat exchanger is 1.845x10 k/w. the specific heat capacities of the air and water may be taken as 1050 and 4190 j/kgk respectively. will this exchanger do the job when cooling water flow is 1.2 kg/s. use the ntu-effectiveness method.