8-10. Performance tests have been performed on a brine/water tubular heat exchanger for geothermal energy utilization. The tubes are 2 m long and have a 10.26 mm inside diameter. Brine at 350 K is supplied at 0.134 kg/s per tube. Silica is found to deposit at a rate of 6.6 10-7 g/cm min. If the initial overall heat transfer coefficient is 5000 W/m K, and the effect of scale roughness is to in- crease the inside heat transfer coefficient by 60%, determine the overall heat transfer coefficient after 1000 hours of operation. Take the density and thermal conductivity of silica scale as 2200 kg/m and 0.6 W/m K, respectively.