ABSTRACT
1.1 Benefits of Enhancement. (a) An existing four-row finned-tube refrigerant evaporator has 551 fins/m on 12.7-mm-diameter tubes located on 31.8-mm equilateral triangular pitch. The fins are plain and the tube inside surface is smooth. The air- and refrigerant-side heat transfer coefficients are 400 and 3000 W/m2-K, respectively. The heat exchanger has Ao/A fr N = 21.6 and Ai /A fr N = 1.19, where N is the number of tube rows. If the Figure 1.3e air-side surface geometry is employed, the air-side heat transfer coefficient will be increased 80%. To obtain the same UA value, how many tube rows would be required? [Ans. 0.83N]
