Authors
Abstract
In this research, an experimental study for the effect of forced vibrations on
pool boiling heat transfer coefficient has been made in a glass of chamber
cylindrical shape (75 mm bore and 300 mm length) and an electrical heater inside it
(12 mm diameter and 80 mm length) to heat the distilled water at different values
of heat flux (27.521 kW/m2-53.08 kW/m2) utilized to perform this work. The
experimental study is carried out at a range of frequencies (2-40 Hz) and at a range
of amplitude (1.8-3.5 mm).
The result obtained showed that the pool boiling heat transfer coefficient is
increasing with increasing the vibration frequency within a range of (2-14 Hz),
compared with that heat transfer without frequency. And, the maximum
enhancement ratio is about 250% at 5 Hz and q"=27.521 kW/m2, 231% at 6 Hz and
q"=36.727 kW/m2, 181% at 6 Hz and q"=41.83 kW/m2 and 93% at 8 Hz and
q"=53.08 kW/m2. In general, it is found that the difference in the temperature has
been maintained at the highest value of vibration frequency range of (14-40 Hz),
and the value of heat transfer coefficient is significantly increasing with increasing
the vibration Reynolds number (Rev).
The effect of vibration frequency has improved not only the boiling heat
transfer coefficient, but also led to improve the amount of heat drawn by the
cooling water (condensation) by increasing the amount of falling drops.
The following empirical relations have been obtained between the experimental
heat transfer coefficient with vibration (hv) and some of important parameters, such
as excess temperature (ΔTexsses) in oC, input heat flux (q") in (W/m2), and vibration
frequency (f) in Hz:
hv = 0.246912 × f0.16534 × ΔT-0.92429 × q"1.0727 nd, the second correlation is (hv)
with Reynolds vibration effect (Rev) and input heat flux (q") in
(kW/m2)hv=499.747×Rev0.3576×q"-2.14
)
