To predict gasoline losses fr om evaporation from tanks that are not equipped with means to reduce them, it is necessary to have reliable methods for assessing mass transfer from its surface. By now, many such methods are known, starting with simplified empirical formulas or graphs and ending with criterion equations. The use of simplified empirical formulas can significantly simplify the calculations. However, this is achieved at the cost of a high calculation error. When predicting the concentration of hydrocarbons in the gas space of reservoirs at the time of the beginning of "exhalation" for several decades, graphs of the increase in the relative concentration of gasoline vapors over time are also used. The curves on them have the form of a parabola and differ only in the value of its exponent. However, the monotonic nature of the increase in the relative concentration over several tens of hours contradicts the foundations of the theory of losses from "small breaths", according to which the concentration of hydrocarbons in the HZ reservoirs is minimal in the morning, then increases with sunrise, reaches a maximum in the afternoon, after which, again at according to the behavior of the sun, decreases. The use of criterion equations is most preferable since mass transfer from the surface of gasoline in tanks is a thermodynamic process, the rate of which is determined by many factors: temperature, pressure of saturated vapors, concentration of hydrocarbons above the surface of an evaporating liquid, intensity of its mixing, speed of air flow around the surface of gasoline, etc. In the known criterion equations, these factors are taken into account in the form of dimensionless similarity criteria of Sherwood, Schmidt, Reynolds, Prandtl and Grashof. However, they have a number of disadvantages, including insufficient consideration of the real conditions of these processes (filling level of tanks, intensity of mixing gasoline, etc.), inconsistency with the requirement of the lim it transition at low rates of filling and emptying tanks, etc. In addition, when calculating the similarity criteria, the value of the average concentration of hydrocarbons above the surface of gasoline is used, this makes the calculation of mass transfer iterative. The article presents the criterion equations for mass transfer, which allow performing calculations without numerous iterations.

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