Phase Frictional Pressure Drop Research Articles

Transient CFD Modelling of Air–Water Two-Phase Annular Flow Characteristics in a Small Horizontal Circular Pipe

The liquid film formed around the inner walls of a small horizontal circular pipe often exhibits non-uniform distributions circumferentially, where the film is thinner at the top surface than the bottom one. Even with this known phenomenon, the problem remains a challenging task for Computational Fluid Dynamics (CFD) to predict the liquid film formation on the pipe walls, mainly due to inaccurate two-phase flow models that can induce an undesirable ‘dry-out’ phenomenon. Therefore, in this study, a user-defined function subroutine (ANNULAR-UDF) is developed and applied for CFD modelling of an 8.8 mm diameter horizontal pipe, in order to capture transient flow behaviour, flow pattern formation and evolving process and other characteristics in validation against experiments. It is found that CFD modelling is able to capture the liquid phase friction pressure drop about maximum of 30% in deviation, consistent to the correlated experimental data by applying an empirical correlation of Chisholm. Due to the gravity effect, the liquid film is generally thicker at the bottom wall than at the top wall and this trend can be further enhanced by increasing the superficial air–water velocity ratios. These findings could be valuable for HVAC industry applications, where some desirable annular flow features are necessary to retain to achieve high efficiency of heat transfer performance.

Flow boiling heat transfer and two-phase flow phenomena of CO2 in macro- and micro-channel evaporators: Fundamentals, applications and engineering design

• Comprehensive review of fundamentals and applications of CO 2 flow boiling. • Analysis of flow boiling heat transfer data and physical mechanisms. • General CO 2 flow pattern maps, mechanistic model for heat transfer and pressure drop. • CO 2 flow boiling and two phase flow in enhanced tubes and mechanisms. • Analysis of the oil effect on CO 2 flow boiling and two phase pressure drop. • Engineering applications of CO 2 flow boiling and two phase flow. • Discussion of CO 2 evaporator simulation and engineering design. • Future research needs in CO 2 flow boiling and potential practical applications. The paper presents a comprehensive review of fundamentals and engineering applications of CO 2 flow boiling heat transfer, flow patterns and two-phase pressure drops in macro- and micro-channel evaporators. First, distinctions of macro- and micro-channels are discussed. Second, the review addresses the extensive experimental studies on CO 2 flow boiling heat transfer and two-phase flow in macro- and micro-channels. The effects of the physical properties on flow boiling heat transfer, flow patterns and pressure drops are analysed by simulations using various physical property packages. Furthermore, analysis of the existing experimental studies of flow boiling heat transfer is presented and the physical mechanisms are discussed. Next, generalized CO 2 flow pattern map and flow pattern based mechanistic flow boiling heat transfer and two phase pressure drop models specially developed for CO 2 are discussed. New experimental database of flow boiling heat transfer and diabatic two phase frictional pressure drop have been set up to evaluate the models. Comparative results of the flow pattern map, heat transfer and pressure drop models to the experimental database are analysed. In addition, studies of CO 2 flow boiling in enhanced channels are summarized. The oil effects on the flow boiling heat transfer and two phase frictional pressure drop are analyzed and simulated as well. According to the extensive analysis, the physical mechanisms and prediction models of the CO 2 flow boiling heat transfer and two phase flow phenomena in evaportaors have been well understood. In the aspect of engineering application, comparisons of simulation results and the experimental data in the real thermal systems are discuseed. Furthermore, research need of CO 2 evaporators is discussed. Some practical design methods of CO 2 evaporators are recommended according to the analysis. Finally, the potential application of CO 2 for high heat flux cooling, thermal and power systems are also discussed. Future research needs in flow boiling heat transfer and two phase flow of CO 2 in evaporators and engineering applications are discussed and recommended according to this comprehensive review.

Condensing two-phase pressure drop and heat transfer coefficient of propane in a horizontal multiport mini-channel tube: Experimental measurements

This article reports the condensing flow heat transfer coefficient and pressure drop results of propane (R290) flowing through a square section horizontal multiport mini-channel tube made of aluminium having an internal diameter of 1.16 mm and a condensing length of 259 mm. Pressure drop and two phase flow experiments were performed at saturation temperatures of 30, 40 and 50 °C. Heat flux was varied from 15.76 to 32.25 kWm−2 and mass velocity varied from 175 to 350 kg m−2 s−1. The results show that the two-phase friction pressure gradient increases with the increase of mass velocity and vapour quality and with the decrease of saturation temperature. The heat transfer coefficients showed to increase with increases of vapour quality and mass velocity while increases of saturation temperature were observed to reduce heat transfer coefficient. The two phase frictional pressure drop correlations of Sun and Mishima and Agarwal and Garimella, and the two-phase flow heat transfer correlations of Koyama et al. and Wang et al. predicted well the experimental results.

Boiling heat transfer and pressure drop of NH3/LiNO3 and NH3/(LiNO3 + H2O) in a plate heat exchanger

This paper presents the experiments carried out to determine the flow boiling heat transfer coefficient and associated frictional pressure drop in a plate heat exchanger which uses the binary fluid mixture ammonia/lithium nitrate and the ternary fluid mixture ammonia/(lithium nitrate + water) with a water content in the absorbent of 20% by weight. The effects on the flow boiling heat transfer coefficient and two phase frictional pressure drop are analysed with a heat flux range of 5–20 kW m−2, a mass flux of 50–100 kg m−2 s−1 and a mean vapour quality of 0–0.2.The mass flux greatly influenced the flow boiling heat transfer coefficient, whereas the addition of water only produced a slight increase. The measurements taken experimentally indicated that the parameters with a pronounced effect on the frictional pressure drop were vapour quality followed by mass flux. Finally, the correlations proposed in Táboas et al. [1] used to predict the flow boiling heat transfer coefficient and frictional pressure drop were well in agreement with the experimental results.

Experimental research on the thermal hydraulic characteristics of sodium boiling in an annulus

Thermal hydraulic characteristics of sodium boiling are significant in the safety analysis for the sodium cooled fast reactor, one of the Generation IV reactors. However, the knowledge on the mechanism of sodium boiling is quite limited. In this study, boiling experiments on sodium flowing through an annulus are performed. The annulus is of 1000mm length, 8mm inner diameter and 12mm outer diameter. The heat flux varies from 80 to 500kW/m2, with inlet subcooling from 63 to 285°C, inlet flow velocity from 0.02 to 0.5m/s and system pressure from 3.67 to 103kPa. The boiling phenomena, two phase friction pressure drop and boiling heat transfer coefficient are investigated. Correlations for the two-phase friction multiplier factor ϕl2 and boiling heat transfer coefficient are proposed, respectively. Predicted results show good agreement with the experimental data.

Experiments and updated model for two phase frictional pressure drop inside minichannels

The objective of this work is to investigate frictional pressure drop during adiabatic liquid–vapor flow inside minichannels. New experimental pressure drop data, relative to two-phase flow inside circular and noncircular horizontal channels with hydraulic diameters ranging from 0.96mm to 2mm, is presented. By analyzing this data the present authors updated the two-phase frictional pressure drop model presented by Cavallini et al. (2009) [16,17], developing a new equation to calculate the effects of surface roughness on the frictional pressure drop as a function of the liquid-only Reynolds number. The present updated model is validated against experimental data and compared with other available correlations.

Two Phase Frictional Pressure Drop of Carbon Dioxide in Horizontal Micro Tubes

Two Phase Frictional Pressure Drop of Carbon Dioxide in Horizontal Micro Tubes

Investigation of two phase heat transfer and pressure drop of propane in a vertical circular minichannel

This article reports the flow boiling heat transfer and pressure drop results of propane in a vertical circular stainless steel minichannel having an internal diameter of 1.70mm and a heated length of 245mm. Two phase heat transfer and pressure drop experiments have been performed at saturation temperatures of 23, 33 and 43°C. Heat flux is varied from 5 to 280kW/m2 and mass flux is varied from 100 to 500kg/m2s. The results show that the two phase frictional pressure drops, as expected, are increased with the increase of mass flux, vapour qualities and with the decrease of saturation temperature. The heat transfer coefficients are showed to increase with the increase of heat flux and saturation temperature while the influence of mass flux and vapour quality is observed as insignificant. After incipience of dryout, the decrease in heat transfer coefficient and also the two phase frictional pressure drop, especially at higher mass fluxes, is observed. The two phase frictional pressure drop correlations of Müller-Steinhagen and Heck and Friedel and two phase flow heat transfer correlations of Cooper and Liu and Winterton well predicted the experimental results.

Flow boiling of ammonia in vertical small diameter tubes: Two phase frictional pressure drop results and assessment of prediction methods

Two phase pressure drops were measured for ammonia at a wide range of test conditions in two sizes of vertical mini channels. The test sections were made of stainless steel (AISI 316) tubes with internal diameter of 1.70 mm and 1.224 mm and a uniformly heated length of 245 mm. Experiments were conducted at three saturation temperatures of 23 °C, 33 °C and 43 °C, the heat flux ranging from 15 to 355 kW/m2 and the mass flux ranging from 100 to 500 kg/m2s. The effect of the heat flux, the mass flux, the vapour quality, the saturation temperature and the internal diameter on the two phase pressure drop are presented in this article. Some generalized two phase pressure drop correlations suggested for macro and micro scale channels are examined by comparing them with our experimental data. None of the examined correlations agreed well with the test data. A new correlation (modified form of Tran et al. correlation) is proposed which is able to predict the experimental data with MAD of 16% and 86% of the data is within ±30% range.

Numerical investigation on frictional pressure loss in a perfect square micro channel with roughness and particles

A numerical study is performed to investigate the effect of inner surface roughness and microparticles on adiabatic single phase frictional pressure drop in a perfect square micro channel. With the variation of particles sizes (0.1 to 1 μm) and occupied volume ratio (0.01 to 10%) by particles, the Eulerian multi-phase model is applied to a 100 μm hydraulic diameter perfect square micro channel in laminar flow region. Frictional pressure loss is affected significantly by particle size than occupied volume ratio by particles. The particle properties like density and coefficient of restitution are investigated with various particle materials and the density of particle is found as an influential factor. Roughness effect on pressure drop in the micro channel is investigated with the consideration of roughness height, pitch, and distribution. Additionally, the combination effect by particles and surface roughness are simulated. The pressure loss in microchannel with 2.5% relative roughness surface can be increased more than 20% by the addition of 0.5 μm diameter particles.

Horizontal Well Gas/Water Shutoff-Field Results

Abstract Many horizontal wells have been drilled to control gas or water coning. However, after breakthrough, attempts to control inflow location along these wells have been expensive and frequently unsuccessful in reducing GOR and WOR. Cemented casing, casing with ECPs, open hole packers, selective stimulation and formation plugging agents have all been tried. Husky's experience with slightly inclined wells, over the past several years, suggested a "new" technique, which has recently been proven successful. Simply lowering tubing in a well, slightly inclined from horizontal, resulted in doubling of oil production rate and reducing gas production by 50%. Details of well configuration, field production results and a simple analytical model, explaining why it works, are presented in this paper. Special reservoir conditions which must exist for this technique are also discussed. Introduction One of the most successful applications of horizontal wells has been the reduction of gas or water coning(1–6), while at the same time improving areal drainage(7. 8). However, because of reservoir heterogeneity and pressure gradients across a reservoir, caused by production and injection operations, breakthrough of gas or water often occurs in one small part of a horizontal well. The resulting production of large amounts of gas or water with the oil increases processing cost and depletes reservoir energy. Therefore many attempts have been made to control inflow from along horizontal wells. Cemented casing, casing with ECPS(9), open hole packers(7), selective stimulation(5) and formation plugging agents(4) have all been tried, often without success. While experimenting with slightly inclined wells, a possible "new" way to control excess gas and water production was discovered. Husky has drilled slightly inclined wells in the Black, Rainbow, and Rainbow South Fields to eliminate uncertainty of oil/water contact location(9), and to drain oil from a moving oil bank in waterflooded pools with a gas cap, but no gas injection. There are several other possible reasons to drill a slightly inclined well, including to drain multiple porosity stringers and to allow the end of the well to be plugged off when excess gas or water production occurs. Production logs have shown that horizontal wells can act as good horizontal separators(3. 11). Also, drawdowns in many horizontal wells have been shown to be very low, in the range detectable only by quartz or sensitive strain gauges(7). These factors suggest that it might be possible to control the type of fluid being produced from some wells by simply changing the tubing inflow points. Although many authors have explored the effects of pressure drops in horizontal wells(12. 13), the specific use of variable tubing inflow points to control producing GOR or WOR has not been clearly stated. Analytical Model A simplified spreadsheet model was built to evaluate wellbore pressure changes and fluid inflow along a slightly inclined wellbore. The model incorporates the effects of productivity, gravity, momentum and single phase friction pressure drop. The tubing inflow location to achieve maximum flow of oil without gas or water production was evaluated.

Some aspects of two phase flow through porous media

In this paper results of experiments conducted on two phase flow through porous layers formed of non heated glass particles (nominal diameter 3–19 mm) are reviewed. The porous layers were 30–70 cm deep and were formed in a 21 cm inside diameter plexiglass pipe. Experiments were conducted with water and air in both co and counter current modes. Data for the average void fraction and two phase friction pressure drop were taken. A flow regime map for two phase flow through porous media, a semi-theoretical model for void fraction, an empirical correlation for counter current flooding and empirical correlations for relative permeability multipliers under co-flow conditions are reported. The interaction between the overlying liquid layer and the porous layer under counter current flow conditions is discussed.