Determination of critical boiling conditions within the whole steam content range for internal pipe flow

The article describes a method for the determination of the critical boiling conditions in evenly heated vertical pipes at upwards flow. By combining suitable equations for the boiling crisis of the 1. kind (film boiling) and the 2. kind (drying-out of the heating surface), it becomes possible to include the whole steam content range. The method was checked by 3044 test points, with an average value of 0.99 and a standard variation of 0.16 for the relative heat flow density in the range of the boiling crisis of the 1. kind, and an average variation of 0.04 and a standard variation of 0.10 for the variation of the steam content in the range of the boiling crisis of the 2. kind. (orig.)