A double pipe heat exchanger is constructed with a 5-nom sch 40 commercial steel outer pipe and a 2½-std type M copper inner tube. The heat exchanger is 2-m long.
Water flows in the tube at an average temperature of 30°C and a flow rate of 5 kg/s.
A 30% ethanol-water solution flows in the annulus with an average temperature of 5°C and a mass flow rate of 12 kg/s. For a clean heat exchanger, determine the,

a. UA product of the heat exchanger (W/K)

b. Pressure drop through the tube and annulus (kPa)
In an effort to increase the heat transfer rate with a heat exchanger of the same footprint, it is proposed to replace the single 2½-std type M inner tube with three 1-std type M tubes in a triangular arrangement as shown in Figure P5.42. The water flow rate is split evenly between the three tubes. For this modified design, determine the

c. UA product of the heat exchanger (W/K)

d. Percent increase in the UA product in the modified design compared to the original design

e. Pressure drop through the tubes and annulus (kPa)

f. Percent increase in the pressure drop through the inner tubes and annulus in the modified design compared to the original design

Transcribed Image Text:

2 std type M copper O Original design 5 nom sch 40 commercial steel FIGURE P5.42 Original and modified heat exchanger designs. Modified design _1 std type M copper