Yield efficiency is defined as the amount of product per unit
energy required for the reaction. The overall production costs of
biodiesel are strongly dependent on the consumption of total energy
in addition to the cost of raw material. The performance of the
cavitation reactor in terms of yield efficiency with different orifice
plate geometries is presented in Fig. 8. One of the important parameters
in the selection of the orifice plate is based on the yield
efficiency performance. It was observed that the yield efficiency
increased with the increase in the inlet pressure. Plate 2 produced
the highest yield efficiency compared to other plates. The yield
efficiency of plate 2 at 2 bar was 12.5 104 g/J and it was greatly
increased by about 42% compared to 1 bar of inlet pressure with the
yield efficiency value of 8.8 104 g/J. The yield efficiency of plate 2
was marginally lower by about 4% compared to the case of inlet
pressure of 3 bar with 12.6 104 g/J. It was found that the yield
efficiency could be significantly improved by optimising the geometry
of the orifice plate with a different pattern of the distribution
of the holes. Many researchers did not report the whole
pattern used in their studies. Although Ghayal et al. (2013) presented
a table of orifice plate parameters, they did not report the
spacing between holes nor the pattern of hole distribution. The
yield efficiency was shortened in the order of plate 1, plate 4, plate 3
and plate 2. At inlet pressure of 2 bar, plate 2 produced about 2.7, 2.1
and 1.4 times more yield efficiency compared to plate 1, plate 4 and
plate 3. The inlet pressure was greatly affecting the yield efficiency
based on different orifice plate geometries. The yield efficiency for
plate 2 at 2 bar was about 4.5 times higher than plate 1 at 1 bar. The
optimised yield efficiency in the present study was about 1.4 times
the yield efficiency reported by Gole et al. (2013) for biodiesel
production using hydrodynamic cavitation. However, the yield ef-
ficiency was almost the same with this study as reported by Ghayal
et al. (2013) with a value of 12.8 104 g/J.