Next Article in Journal
Collective Strategy Condensation: When Envy Splits Societies
Previous Article in Journal
Linear Response of General Observables in Spiking Neuronal Network Models
Previous Article in Special Issue
Lognormality in Turbulence Energy Spectra
Article

Entropy Generation for Negative Frictional Pressure Drop in Vertical Slug and Churn Flows

State Key Laboratory of Multiphase Flow in Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China
*
Author to whom correspondence should be addressed.
Entropy 2021, 23(2), 156; https://doi.org/10.3390/e23020156
Received: 24 December 2020 / Revised: 18 January 2021 / Accepted: 23 January 2021 / Published: 27 January 2021
(This article belongs to the Special Issue Entropy Production in Turbulent Flow II)
It is widely accepted that the frictional pressure drop is impossible to be negative for pipe flow. However, the negative frictional pressure drops were observed for some cases of two-phase slug and churn flows in pipes, challenging the general sense of thermodynamic irreversibility. In order to solve this puzzling problem, theoretical investigations were performed for the entropy generation in slug and churn flows. It is found that the frictional pressure drop along with a buoyancy-like term contributes to the entropy generation due to mechanical energy loss for steady, incompressible slug and churn flows in vertical and inclined pipes. Experiments were conducted in a vertical pipe with diameter as 0.04 m for slug and churn flows. Most of the experimental data obtained for frictional pressure drop are negative at high gas–liquid ratios from 100 to 10,000. Entropy generation rates were calculated from experimental data. The results show that the buoyancy-like term is positive and responsible for a major part of entropy generation rate while the frictional pressure drop is responsible for a little part of entropy generation rate, because of which the overall entropy generation due to mechanical energy loss is still positive even if the frictional pressure drop is negative in vertical slug and churn flows. It is clear that the negative frictional pressure drops observed in slug and churn flows are not against the thermodynamics irreversibility. View Full-Text
Keywords: entropy generation; two-phase flow; slug flow; churn flow; frictional pressure drop; thermodynamic irreversibility entropy generation; two-phase flow; slug flow; churn flow; frictional pressure drop; thermodynamic irreversibility
Show Figures

Figure 1

MDPI and ACS Style

Liu, L.; Liu, D.; Huang, N. Entropy Generation for Negative Frictional Pressure Drop in Vertical Slug and Churn Flows. Entropy 2021, 23, 156. https://doi.org/10.3390/e23020156

AMA Style

Liu L, Liu D, Huang N. Entropy Generation for Negative Frictional Pressure Drop in Vertical Slug and Churn Flows. Entropy. 2021; 23(2):156. https://doi.org/10.3390/e23020156

Chicago/Turabian Style

Liu, Lei, Dongxu Liu, and Na Huang. 2021. "Entropy Generation for Negative Frictional Pressure Drop in Vertical Slug and Churn Flows" Entropy 23, no. 2: 156. https://doi.org/10.3390/e23020156

Find Other Styles
Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Article Access Map by Country/Region

1
Back to TopTop