Condensation in horizontal tubes, part 1: two-phase flow pattern map

Improved flow pattern map for accurate prediction of the heat transfer coefficients during condensation of R-134a in smooth horizontal tubes and within the low-mass flux range

“…A total of 74 data points were obtained in this range. This test matrix is shown overlaid on the Thome-El Hajal flow pattern map [12] in Fig. 2.…”

“…El Hajal et al [12] adapted the flow-boiling two-phase flow pattern map, originally developed by Kattan et al, for condensation inside horizontal tubes. Due to the high reduced pressures during condensation and because of the sensitivity of flow pattern transitions, heat transfer coefficients and pressure drop to void fraction, El Hajal et al [12] and Collier and Thome [13] proposed a new log-mean method for predicting void fractions for pressures ranging from atmospheric up to near the critical pressure.…”

“…The Thome-El Hajal flow pattern map [12] is a modification of the Steiner [14] map, which in turn is a modification of the original Taitel and Dukler [15] map. El Hajal et al [12] simplified the implementation of the map by bringing the Rouhani and Axelsson [16] void fraction equation into the method to eliminate its iterative solution scheme.…”

“…El Hajal et al [12] simplified the implementation of the map by bringing the Rouhani and Axelsson [16] void fraction equation into the method to eliminate its iterative solution scheme. Also, the changes proposed by Zürcher et al [17] were implemented to ensure better prediction of the transition curves from annular to stratified-wavy flow, and from stratified-wavy to stratified flow.…”

“…For flow condensation, saturated vapour enters a condenser tube and forms either a thin liquid film around the perimeter of the tube as an annular flow or a liquid layer in the bottom of the tube and a gravity-controlled condensing film around the upper perimeter as a stratified or stratified-wavy flow [12,18]. At very high mass fluxes, it is also possible that the flow goes into mist flow, in which liquid droplets are entrained in a largely gaseous flow.…”