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Research Papers: Multiphase Flows

# Modeling and Experimental Studies on the Absorption of Entrained Gas and the Influence on Fluid Compressibility

[+] Author and Article Information
Hao Tian

Department of Mechanical Engineering,
University of Minnesota,
Minneapolis, MN 55455
e-mails: tianx156@umn.edu;
tianhao@dlmu.edu.cn

James D. Van de Ven

Department of Mechanical Engineering,
University of Minnesota,
Minneapolis, MN 55455
e-mail: vandeven@umn.edu

1Present address: Transportation Equipment and Ocean Engineering College, Dalian Maritime University, No. 1 Linghai Road, Dalian 116026, China.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received August 26, 2016; final manuscript received April 5, 2017; published online July 10, 2017. Assoc. Editor: Mark R. Duignan.

J. Fluids Eng 139(10), 101301 (Jul 10, 2017) (8 pages) Paper No: FE-16-1551; doi: 10.1115/1.4036711 History: Received August 26, 2016; Revised April 05, 2017

## Abstract

The bulk modulus of hydraulic fluid is dependent on the quantity of entrained gas in the fluid. In this paper, an effective fluid bulk modulus model that captures dynamic gas absorption during pressure transients is derived from the overall mass transfer theory. Optical measurement of a microgas bubble volume is used to determine the interfacial mass transport. Compared to traditional models, the proposed model is able to capture the 10% gap in the pressure profile between the first and second cycles, when simulating multiple compression cycles of an oil sample with 0.65% entrained gas by volume at 8 MPa.

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## Figures

Fig. 1

A gas bubble entrained in hydraulic oil under thermal equilibrium state

Fig. 3

Aeration, compression, and bubble visualization system schematic

Fig. 2

Computed time constant until thermal equilibrium for different density and bubble sizes at 421 K

Fig. 12

Experimental and simulation results of pressure volume relationship during volumetric compression processes with 0.655% of N2 entrained as gas bubbles. The average diameter used in the model was 225 μm.

Fig. 4

Circuit diagram of the aeration system

Fig. 5

The in-house designed oil compressor

Fig. 8

The pressure volume plot of the oil–gas mixture with entrained bubble for three compression cycles, the initial entrained gas to oil ratio is 0.0032

Fig. 9

The measured tangential bulk modulus for three compression cycles, the initial entrained gas to oil ratio is 0.0032

Fig. 10

Experimentally determined mass transfer rate as a function of time at 124.6 bar using linear least square fit

Fig. 11

Experimental measured relationship between Δpρ(wgE−wgE0) and the mass flux qm, the bulk mass transport coefficient is determined to be 1.3×10−6

Fig. 13

Experimental and simulation results of pressure volume relationship during volumetric compression processes with 0.258% of N2 entrained as gas bubbles. The average diameter used in the model was 130 μm.

Fig. 14

Experimental and simulation results of pressure volume relationship during volumetric compression processes with 0.601% of N2 injected in bulk. The average diameter used in the model was 2000 μm.

Fig. 6

Captured oil with entrained nitrogen bubbles image before the first compression

Fig. 7

The histogram of the bubbles of different sizes within a frame

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