Controlling the heat transfer and pressure drop within economical working conditions for a movable flat tube bundle

The present work consists of three stages; in first stage, a heat exchanger with a bundle of movable flat tubes is designed to investigate experimentally the variation of Nusselt number and non-dimensional pressure drop with both the air incident angle and the Reynolds number. The Reynolds number is expressed as a function of the maximum air velocity and the air incident angle. The aspect ratio for the flat tubes equals 3/7. In the second stage, the experimental data from the first stage, for the heat transfer and pressure drop are supplied into a controlling unit. This unit is guided by a written program, and can vary the incident angle in order to give a prescribed thermal behavior with time, without the need to change the air inlet conditions. In the third stage, A numerical model is prepared and verified by both the previous work and present experimental results. This model is used to simulate additional future cases without the need to additional experimental costs and effort. Both the experimental and numerical results showed that, the Nusselt number and the non-dimensional pressure drop increase slightly with the incident angle within the range of incident angle from 0° to 20°, and increase considerably from 20 to about 70°. For every experiment with a certain incident angle value, the percentages of increase for both, the Nusselt number and the non-dimensional pressure drop, over those of the horizontal tube case, are checked to get the most economical case, which is observed when the Reynolds number is 902 RR with incident angle of 20°.