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. |
