The outlet cold temperature found to decrease by 5 C due to the deposition of solids on the tube surface after 3 years of operations. Evaluate the new outlet temperature of the hot stream.

Geothermal water (c=4250 J/kg-C) is to be used to heat fresh water (c=4180 J/kg-C) in a one shell pass and 4 tube passes heat exchanger. Geothermal water flow through the shell at 70 C and leave at 40 C with a heat transfer coefficient, ho = 2.5 kWm2K. The fresh water enters the thin tube at 20 C and leave at 45 C. The heat transfer surface area is 50 m2. The inner convection heat transfer coefficient is to be estimated twice the outer convection heat transfer coefficient