الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Energy is an essential matter for development and progress, one of the most important devices which deal with energy are heat exchangers. The need to increase the thermal performance of heat exchangers, thereby effecting energy, material , cost savings have led to development , use of many techniques termed as heat transfer augmentation. The thesis aims to study the effect of changing the mass flow rates and variable speed of the inner tube on heat exchanger effectiveness, Also the effect of the heat exchanger flow arrangement (parallel or counter flow) on the performance characteristics of a double-pipe heat exchanger with rotating inner tube. To perform this task a test rig had been built with facilities to measure temperatures, mass flow rate and rotating speed. An electric circuit is added to control the inner tube rotation speed. And water circuit is used to control both of parallel and counter flow, there are two flow water circuits, one fluid circuit is for warm water and one for cold water. Water was used as working fluid in both the hot and cold sides. The tested heat exchanger has the radius ratio is 0.5, an inner pipe has a 30 mm ID, and 2 mm thickness, The outer pipe has a 60 mm ID, and 2.5 mm thickness ,and same lengths (L=H=100cm). The outer surface of the test section was insulated to minimize convective heat losses and necessary precautions were taken to prevent leakages in the system by rubber . This experimental study was done on at working the inner pipe at speeds are of range for 0 ≤ N ≤ 1000 R.P.M, and 0.005 ≤ mc ≤ 0.09 kg/s and 0.005 ≤ mh ≤ 0.09 kg/s. The hot-water temperature at the inlet was kept constant at 60°C by using an electrical heater. The experimental effectiveness data were presented with curves as a function of the NTU for different heat capacity ratio. In addition to the usual heat transfer calculations. The results showed that the effectiveness for both parallel and counter flow has minimum value at heat capacity ratio equal to unity but with higher values else. Also as the rotation speed increases the Reynolds number increases and hence heat transfers rate and the NTU and effectiveness values. Also that at equal heat capacity the NTU values are minimum values. The NTU value is constant after the minimum value until if one of the hot or cold fluids increases.