Table 3 and Fig. 4 show the various arrangements of the tubes in
the heat exchanger. In the beginning, smooth tubes were employed
as the inner and outer tubes of the heat exchanger. In the next step,
corrugated tube was used only for inner tube of heat exchanger.
And finally, both of the inner and outer tubes were corrugated.
Various arrangements of convex and concave corrugated tubes
were studied as shown in Fig. 4. Tests were performed with various
Reynolds numbers for each arrangement. Hot water (inner tube)
inlet temperature and Reynolds number were kept constant at
around 40 C and 5500 respectively. The inlet temperature of cold
water (outer tube)was maintained at around 8 C, and experiments
were performed over the Reynolds number range of 3500e18,000 based on the hydraulic diameter of the annular space between the
two tubes. During the tests, inlets and outlets bulk temperature,
pressure drop and value of the volume flow rate, were recorded at
steady state condition.