Further studies in filmwise condensation of steam on horizontal finned tubes

Abstract

Over the years, there has been significant variation in the filmwise steam condensation data at NOS on horizontal low0integral finned tubes. With a view to increasing the accuracy of the data, inserts were used inside the tubes to reduce inside thermal resistance; however, significant discrepancies then occurred in the calculated outside coefficient when compared to data taken without an insert. These discrepancies arose due to the data reduction technique which assumes a known inside-heat-transfer resistance and subtracts this from a measured overall resistance. If the assumed value on the inside is inaccurate, then the outside value is equally inaccurate. The present work used an instrumented smooth tube to obtain accurate inside heat-transfer correlations both with and without inserts and uses these to obtain accurate outside coefficients for a family of uninstrumented finned tubes with a view to finding an optimum fin spacing for steam condensation.