scope:

ESDU 94041 provides correlations in vapour shear-controlled annular and gravity-controlled stratified flows for the local heat transfer coefficient at a specified vapour mass flow fraction. A flow regime map defines the regions where those conditions occur as predicted from the available data. The range of data extracted from the literature that was used to develop the correlations is tabulated and the correlation achieved is illustrated with a sketch that shows most of the predicted values falling within 30 per cent of the experimental values. A step-by-step calculation procedure is set out and illustrated with a worked example. The effect of sub-cooling is discussed and practical design details such as the use of multi-pass units, condensate drainage and venting are considered.