Geothermal water, t_hi-95 c, is to be used in a double pipe counter-flow heat exchanger to heat cold water, tci-12 c, c,-41 80 j/kg-k flowing at l .2 kg/s to tc,-50 c for household use. the cold water will flow through the inner tube of the copper thin-walled heat exchanger, di 0.03761 m (1%"type k tubing). for safety reasons the size of the heat exchanger is to be limited in order to limit the outlet temperature of the cold water. assuming chot> ccold (note: c-m cp) and that the heat transfer coefficients on the hot and cold sides are approximately equal (hc -hh) what is the maximum allowable length of the heat exchanger? density of both streams is p 1000 kg/m', kter 0.615 w/m-k, h-0.798 x 10 kg/m-s, pr 5.4 (12.0 m)