The design of boilers and evaporators requires a means for calculating the heat transfer coefficients of boiling fluids. The practical importance of this problem is evident from the fact that hundreds of correlations for such calculations have been proposed, including one by the author himse1f(25). However. most of them are not reliable beyond the range of data on which they were based. Only the correlation of Chen(6) can at all be considered as general. However, its application is limited to vertical flows.

The author's efforts have resulted in the development of the CHART correlation, a graphical method of solution, which appears to be considerably superior to any other available predictive technique in range of applicability and ease of computation. It has been compared with about 800 data points from 18 independent experimental studies. These data include most of the common refrigerants in their entire range of application. Also included are data for boiling water between 15 to 2500 psia pressure, which covers practically the entire range of boiler operation. Almost all common pipe materials. horizontal and vertical orientations, circular and annular flow channels, upward and downward flow, as well as a very wide range of heat and mass flux are covered. Hence from the evidence in hand, the CHART appears to be applicable to saturated boiling inside· pipes of all Newtonian fluids (except metallic fluids) over the· entire practical range.

The objective of this paper is to present the CHART correlation, explain its use, and demonstrate the agreement of its predictions with experimental data. Some suggestions regarding the design of refrigeration evaporators using the CHART as well as other correlations are also made.