A double pipe heat exchanger is made of an 8-nom sch 20 commercial steel outer pipe and a 4-std type M copper inner tube. The fluid in the annular space is liquid water that has a volumetric flow rate of 120 m3/h and an average temperature of 50°C. The fluid in the inner tube is liquid ammonia at an average temperature of –20°C and flowing at 60 m3/h. Determine the friction factor in the

a. Tube

b. Annulus