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representation of diagram of U-tube heat exchanger is shown in the Fig. 1b, c.
The twisted tapes were made of 1.00 mm thick aluminum strips, the width of the
strip being 1 mm less than the inside diameter of the test section tube and the
dimensions are shown in Table 1. The strips were twisted on a lathe by manual
rotation of the chuck. Twisted strips were heated periodically by flame to relax
the stresses to prevent them from buckling and untwisting when they are removed
from the lathe. The schematic of this twisted tape used in the section is shown in
Fig. 1d
2.2 Experimental Procedure
In this study, the centrifugal pump was switched on, and the water flow rate
to the test section was adjusted using the by-pass valve. The hot water at a
particular flow rate is allowed to flow through jacket side to maintain con-
stant wall temperature until steady state is attained. First the plain tube double
pipe heat exchanger (i.e., without turbulator) was tested. At the beginning of
series of tests, the cold water was circulated through inner tube and hot water
through annulus tube in parallel flow and counter-flow configuration. The flow
rate of hot water is maintained constant. The cooling water flowing in the heat
exchanger was at room temperature. First the cold water flow rate was fixed
to 2 l/min (0.033 kg/sec). A prescribed heat input was given to the water in
hot water tank in sufficient state. Usually, 30 min was required for the attain-
ment of steady state for a run. Once the steady state was reached readings
were taken for the flow rates of hot and cold water, temperatures at inlet and
outlet section of hot and cold fluid and U-tube manometer. The flow rate of hot
water was kept constant, and the above procedure was repeated for different
flow rates of cold fluid.
Experiments were first conducted for the plain tube heat exchanger and sub-
sequently with twisted tape inserts by inserting the straight full twist insert with
H/D ratios of 6, 10, 15, and 20. Full-length twisted tape was inserted into the both
straight legs (2.3 m each) of the u-tube. The two tapes were inserted into the tube
by pushing from both ends of the tube. Cold water was circulated inside the
tube and hot water through annulus in counter flow arrangement and then the data
was observed and readings were tabulated.利用内置扭带强化双U型管式换热器管内的
传热特性和压降特性
摘要： 把一条扭带插入双U型管式换热器以产生涡流，从而提高流体流动时的传热速率。有人提出了一个关于U型管套管换热器的典型试验段的强化传热和摩擦系数变化的实验研究，这个U型套管换热器带有一个圆形钢管全长插入。本次实验的流体是从雷诺数为3000到31000变化下的强制对流。论文网从实验数据来看，我们把传热系数，摩擦因数和内置扭带的热性能的数据结果进行了分析计算，并与光滑管的数据相应做比较。结果表明，传热系数，摩擦系数都有明显的增加，与此同时我们还发现光滑管热性能优于全长扭带的热性能2–2.2倍。
关键词：加强换热；换热器；摩擦系数；性能比；扭曲比