This paper presents an improved model to calculate the slug liquid holdup. This variable is a key parameter to closure the slug flow modeling in pipes. The main of the idea of the closure relationship is an energy balance between the bubble surface energy and the turbulent kinetic energy in the slug body. In order to complete the balance, the authors determined two parameters from a large experimental database.
The paper is properly written and contributes to multiphase flow area, especially for oil and gas industry due to the large range of fluid properties and pipes diameters used to generate the closure coefficients.
Minor revisions:
• The authors wrote on page 2, line 70: “Only three mechanistic models are available in the literature review based on the entrainment mechanism”. Four references are cited on this sentence (17, 18, 19 and 20), but only three of them presents models. The reference 18, does not present a mechanistic model to obtain the slug liquid holdup, on this paper, the authors used the Gregory correlation (10) to calculate the slug liquid holdup.
• Page 4, line 79 and 80. The paper has sections not chapters.
• Table 1. Could the authors modify the column “description”? Please split this column into its natural sub-columns to improve readably (measurement technique, density, etc). Please apply the same idea to tables 2 and 3.
• Table 4. The slip velocity is not a dimensionless parameter; it has units [L/t].
• Table 5. Some equations were modified form its original from to dimensionless form, some other do not. Also, some parameters such as “B” on Barnea and Brauner (1985) line correspond to well know parameters such the Brodkey (1967) diameter. Please standardize and correct this.
• Some nomenclature used is not defined. For example, the “lambda” used on the RHS of the equation 8 and on the line before equation 8, the parameter “xi”.
• The propose model will be implemented on pipeline simulators for slug body holdup calculation, but has three clear discontinuities with respect to inclination angle. Can the authors suggest how to treat this problem?
Based on these comments, I would accept this paper with minor corrections on the prestigious Canadian Journal of Chemical Engineering. The authors should improve their manuscript and resubmit.

This paper version incorporates the most of the reviewers’ comments, concerns, and questions. At this point, I have not further observations or concerns. Accordingly, I consider this paper ready for publication on the prestigious Canadian Journal of Chemical Engineering.