Theoretically, surface tension is an important variable for boiling. The rate of nucleus formation is proportional to e{sup}(-σ{sup}3) Thus, small decreases inσ should cause large increases in the number of nuclei. The cavitation theory predicts that the force required to rupture a liquid in tension is proportional toσ{sup}(3/2) Thus, liquid with large surface tensions should be difficult to fracture. detailed discussions of these theories are available (Westwater, 1956). On the other hand,considering the equation of state only, no reason is apparent why a surfactant should affect the metastable state. Therefore, on nucleation theoretical grounds only, a increase inσ by surfactant additive may have no effect or it may increase the rate ofheat transfer. It cannot decrease the heat flow. Surface tension also affects different fundamental processes in nucleate boiling differently, such as bubble growth, bubble departure, bubble shape, etc. However, the way through which nucleate boiling heat transfer may be varied by the changes in these processes is not so obvious.
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