1. (25 pts) Exergy LLC produces commercially available tube-in-tube heat exchangers. Consider their model #AS-00448, with specifications and flow conditions listed below: Overall length: L =6 m, all 316 stainless steel construction, surface roughness of 0.5 m Inner tube: ID; = 7.1 mm, OD = 9.5 mm Outer tube: ID. = 16.7 mm, OD. = 19.1 mm Cold water enters the inner tube at: V = 10 L min and Ti,in = 20C Counterflow warm water enters the outer tube at: Vo = 30 L min and To.in = 50C a. (6 pts) Calculate the frictional pressure drop for the tube-side and annulus-side water flows. (Hint: pressure drop curves are available from the manufacturer) b. (9 pts) Calculate the overall UA for this heat exchanger at the listed operating conditions. c. (5 pts) Find the effectiveness of this heat exchanger for the listed operating conditions. Could the heat transfer rate be significantly improved by increasing the heat exchanger length? d. (5 pts) Often, there is a "limiting" resistance in a heat transfer system that is more significant than others. Is there a specific heat transfer stage in this heat exchanger that contributes a "limiting" resistance? If so, suggest a strategy to improve the overall performance. Pressure Drop 50 psi 40 30 10 00413 &00459-1 Typical Inner Tube Pressure Drop for Water 10 15 20 2 00448 & 00536-1 00528 & 00644-1 4 Water Flow Rate 6 25 Ipm gpm 8 kPa 300 250 200 150 100 50 Pressure Drop 25, psi 20 15 10 5 00413 & 00459-1 Typical Outer Tube Pressure Drop for Water 20 30 40 10 4 00448 & 00536-1 00528 &00644-1 8 Water Flow Rate 12 50 Ipm kPa 150 125 100 75 50 25 gpm 16