This paper presents a comparative experimental study on the performance characteristics of the
circulating air coolers for the generators of the hydro-power plant of the High Dam in Aswan. The
study considers two different air-water cooler designs of cross flow finned tubes heat exchangers
working under varying operating conditions. The circulating air temperatures and the cooling water
pressures for twelve coolers in each of the twelve units of the hydro-power plant were measured and
analyzed to obtain useful results describing the cooler performance. The experimental results are
based on measurements over total time duration of 1008 operating hours covering 42 summer days.
The results are discussed to investigate the effects of time variation of the generated power, and the
locations of the coolers and the power units on the performance of both cooler designs. The results
of the actual fouling factor indicate that both coolers were designed with excess surface area to
work well for long periods. The agreement of the experimental results with the commonly used
effectiveness empirical relation indicates the proper performance of the working coolers. On the
other hand, the discussion of the results showed the malfunction of some coolers due to the
blockage of their damaged tubes. The overall performance of the air coolers in most power units of
the plant maintains good flow behaviour of the hot air and uniformity of its temperature at levels
sufficiently below the normal design temperature range for the generators of most power units.