1. By convention, pressure drop is treated as a positive value. Therefore, Eq. (11) should be as follows, i.e., without the negative sign on the right-hand side:

 
Uinterface=dP/dxf/b4μLRtube2Rbubble2
(5)

2. The expression for pressure drop due to the film-slug transition, Eq. (19) had a factor of 2 in the denominator, which should be removed, as shown below:

 
ΔPonetransition=ρL1RbubbleRtube2UslugUfilmUbubbleUfilm
(6)

3. The value of the coefficient, a, in Eq. (21), currently listed as 2436.9 in the text following the equation, should be changed to a=2.4369. For Eq. (24), the coefficient should be: a=0.9965 instead of 996.5.