Heat Transfer in a Rectangular Duct with Thin Plates Inserted in Staggered Arrangement

摘要

This paper investigates how the local heat transfer coefficients and the friction facter are affected by the pitch and the clearance between thin plate and duct wall when thin plates (thickness: 5 mm, length: 20 mm) are set in a staggered arrangement in a rectangular duct in order to augment heat transfer from the duct wall.Average heat transfer coefficient in fully developed region increases with a decreasing pitch and attains a maximum at P=4 (P: pitch), and its value is two times of that in smooth duct; the friction facter $lambda$, on the other hand, increases five times at P=4, two times at P=12 in comparison with value of smooth duct.The degree of augmentation is also analysed taking account of pressure loss. In the low-Reynolds number turbulent regime, $eta$, which is the ratio of the average heat transfer for the present system to that for a smooth duct under the condition of equivalent pumping power, is larger than unity.