Performance model evaluation of turbine flow meter in vertical gas-liquid two-phase flows

Aiming at the need for flow measurement of gas-liquid flows in domestic gas well production, this paper proposes a measurement method based on the combination of the turbine flow meter (TFM) and a rotating electric field conductance sensor (REFCS). In experiments, the REFCS is used for the measurement of the gas holdup. To verify the applicability of the TFM models investigated in the previous study, for the modeling part, the mass, momentum and torque models are evaluated in vertical upward gas-liquid two-phase flows. In our model test, the meter factor model of TFM considers the effects of the slip ratio between the gas and liquid phases and flow patterns. In particular, the gas holdup involved in calculating the slip ratio in the model evaluation is obtained from the REFCS measurements. Model test results show the torque model has better volumetric flow rate prediction accuracy than the mass and momentum models. In the present study, the ranges of the liquid and gas phases are Q_w = 2–30 m³/d and Q_g = 1–16 m³/d, it was found that the average absolute deviation (AAD) in the predicted volume flow rate is equal to 1.23 m³/d and the average absolute percentage deviation (AAPD) is equal to 7.69%. The evaluated results presented in this paper will allow better estimates of the volumetric flow rates of gas-liquid flows based on the combined TMF and REFCS measurements during the monitoring of gas well production.     

An experimental study on dryout pattern of two-phase flow in helically coiled tubes

Experimental results are presented for the effects of coil diameter, system pressure and mass flux on dryout pattern of two-phase flow in helically coiled tubes. Two tubes with coil diameters of 215 and 485 mm are used in the present study. Inlet system pressures range from 0.3 to 0.7 MPa, mass flux from 300 to 500 kg/m2s, and heat flux from 36 to 80 kW/m2. A partial dryout region exists because of the geometrical characteristics of the helically coiled tube. The length of the partial dryout region increases with coil diameter and system pressure. On the other hand, it decreases with increasing mass flux. The critical quality at the tube top side increases with mass flux, but decreases with increasing system pressure. This tendency is more notable when the coil diameter is larger. When the centrifugal force effect becomes stronger, dryout starts at the top and bottom sides of the tube. However, when the gravity effect becomes stronger, dryout is delayed at the tube bottom side. In some cases when the mass flux is low, dryout occurs earlier at the outer side than at the inner side of the tube because of film inversion.     

Statistical experimental study for verifying thermal characteristics of insulated double pipe

Journal of Mechanical Science and Technology - This study investigates the heat transfer characteristics of an insulated double pipe in accordance with the degree of vacuum and the working fluid...     

An approach for transition correlation of laminar pulsatile pipe flows via frictional field characteristics

Transition of laminar pulsatile pipe flow into turbulence is one of the current research topics in flow dynamics. Despite the existence of a considerable number of theoretical and experimental studies, the physical mechanism of transition is not well defined. Furthermore, there is almost no information on the start and the end of the transition in terms of pulsatile flow parameters.

In this paper, an approach which consists of attempts to correlate the governing flow parameters is presented to reveal the transition process with particular emphasis on the frictional field. The experimental data collected in slightly compressible, Newtonian, one-dimensional laminar pulsatile pipe flow without a flow reversal were compiled for this purpose. The common oscillation parameters, dimensionless frequency parameter and velocity amplitude ratio A₁ were the main variables of the experimental study covering the ranges of and 0.05≤A₁≤0.8. The time history of local static pressure gradient and axial velocity field were accumulated and the data were expressed through pulsatile flow, instantaneous λ_u(t) and time-averaged λ_u,ta friction factors using momentum-integral equation. A reference friction factor ratio λ_R, whose definition was based on the concept of steady flow friction was introduced. The start and the end of transition were predicted through the functional relationships of λ_R with time-averaged and oscillating Reynolds numbers, Re_ta and Re_os by means of a trial–error procedure. The proposed correlations and determined approximate critical limits of transition are only valid in the corresponding ranges of 2000≤Re_ta≤60 000, 620≤Re_os≤18 800 and the analysis is open to discussion.     

An experimental study on the thermal performance of a concentric annular heat pipe

Concentric annular heat pipes (CAHP) were fabricated and tested to investigate their thermal characteristics. The CAHPs were 25.4 mm in outer diameter and 200 mm in length. The inner surface of the heat pipes was covered with screen mesh wicks and they were connected by four bridge wicks to provide liquid return path. Three different heat pipes were fabricated to observe the effect of change in diameter ratios between 2.31 and 4.23 while using the same outer tube dimensions. The major concern of this study was the transient response as well as isothermal characteristics of the heat pipe outer surface, considering the application as uniform heating device. A better performance was achieved as the diameter ratio increased. For the thermal load of 180 W, the maximum temperature difference on the outer surface in the axial direction of CAHP was 2.3°C while that of the copper block of the same outer dimension was 5.9°C. The minimum thermal resistance of the CAHP was measured to be 0.04°C/W. In regard to the transient response during start-up, the heat pipe showed almost no time lag to the heat source, while the copper block of the same outer dimensions exhibited about 25 min time lag.     

An experimental study on the transition criteria of open channel natural convection flows

Natural convection experiments were carried out for a wide range of the Grashof number from 10⁴ to 5 × 10⁹ or for the Rayleigh number from 10⁷ to 10¹³ in order to seek the proper transition criteria from laminar to turbulent. Using the analogy concept, heat transfer systems were simulated by corresponding mass transfer systems. The copper sulfate electroplating system was chosen as the mass transfer system. The experimental results closely reproduced the McAdams’s correlation for laminar and Fouad’s for turbulent. The Sherwood numbers obtained from the experiment were proportional to the 1/4 power of Rayleigh number or Grashof number at laminar region and the near 1/3 power at turbulent region as the well known theory. This paper concludes that the proper transition criteria of the natural convection should be the Grashof number of 10⁹. The originality of this paper comes from the fact that the study deals with very large value of Schmidt number and that by using the analogy experiment methodology, high values of Rayleigh number and Grashof number were achieved with a relatively short test facility.

     

Independent component analysis of interface fluctuation of gas/liquid two-phase flows — experimental study

It is important to understand the behaviour of two-phase flows in industry. This paper presents a study of the interface fluctuation between gas/liquid two-phase flows in a horizontal pipeline. Having obtained the data of a gas/liquid flow by electrical resistance tomography (ERT), an independent component analysis (ICA) method can be applied not only to extract the flow regime information but also the interface fluctuation of the flow. The efficiency of ICA with the ERT data has been assessed by experiment. The independent components have been interpreted by comparing the obtained independent components with the reconstructed images by ERT, showing that ICA is not only effective in extracting flow regime information, but also provides the fluctuation of each individual phase and the interface between the two phases. Without modelling the forward problem, this method can be applied to other electrical tomography modalities.     

Tomographic reconstruction of two-phase flows

Tomography has been investigated to observe bubble behaviors in two-phase flows. A bubbly flow and an annular flow have been reconstructed by tomography methods such as an algebraic reconstruction technique (ART) and a multiplicative algebraic reconstruction technique (MART). Computer synthesized phantom fields have been used to calculate asymmetric density distributions for limited cases of 3, 5, and 7 projection angles. As a result of comparison of two tomography methods, the MART method has shown a significant improvement in the reconstruction accuracy for analysis of the two-phase flows.     

An experimental study on the ultrasonic machining characteristics of engineering ceramics

Engineering ceramics have many unique characteristics both in mechanical and physical properties such as high temperature hardness, high thermal, chemical and electrical resistance. However, its machinability is very poor in conventional machining due to its high hardness and severe tool wear. In the current experimental study, alumina (Al₂O₃) was ultrasonically machined using SiC abrasives under various machining conditions to investigate the material removal rate and surface quality of the machined samples. Under the applied amplitude of 0.02 mm, 27 kHz frequency, three slurry ratios of 1:1, 1:3 and 1:5 with different tool shapes and applied static pressure levels, the machining was conducted. Using the mesh number of 240 abrasive, slurry ratio of 1:1 and static pressure of 2.5 kg/cm², maximum material removal rate of 18.97 mm³/min was achieved. With mesh number of 600 SiC abrasives and static pressure of 3.0 kg/cm², best surface roughness of 0.76 pm Ra was obtained.     

An experimental study on the ignition and emissions characteristics of wallpapers

The combustion characteristics of wallpaper and the toxicity of gas produced from wallpaper fires were analyzed to evaluate the fire risk of wallpaper used in living spaces. Ash content was measured with a high-temperature electric furnace, and thermal analysis was carried out with thermogravimetric analysis (TGA). Combustion time and smoke concentration were measured with a cone heater and a combustion gas analyzer. The smoke density of samples was measured using the smoke chamber ASTM E 662. Pyrolysis in silk wallpaper began at a lower temperature than the other samples. This means that silk wallpaper can be ignited at a low heat flux and will have a greater fire risk than other kinds of wallpaper. Heat by radiation flux caused silk wallpaper to ignite in the shortest time compared to the other samples, so the time for evacuation in this situation may also be reduced. Silk wallpaper also released the highest carbon monoxide concentration, so the toxicity and harmful effects to consciousness were stronger than any other wallpaper. The smoke densities of silk wallpaper and fire retardant-treated silk wallpaper were very high due to their vinyl coatings.     

An experimental study of a two-phase closed loop thermosyphon with dual evaporator in parallel arrangement

A Two-phase Closed Loop Thermosyphon(TCLT) has been applied to many industrial fields as a waste heat recovery system, a telecommunication cooling system and other heat transport devices for the last 2 decades. It is common to design aTCL T to consist of one evaporator, one condenser and 2 separated lines of condensate liquid and vapor of working fluid. The present study was conducted in search of the new possibility of connecting multiple evaporators in parallel to the evaporator section. There has been little information about this so far. It is expected that aTCLT with multi-evaporator would provide a new solution to designing a compact telecommunication cooling system where lots of heat generating circuit boards are connected in parallel arrangement. In the present study aTCLT with two evaporators was prepared and given to a series of operational performance tests. The study was focused on investigating its operational problems and collecting information about its performances. Some important findings are as follows. The main source of operational instability was an occurrence of a hot dried patch on the heated surface when the rate of heat input was raised to a certain limit. For a single evaporator mode of the presentTCLT model, the maximum allowable heat transport rate was about 650W. For dual evaporator mode of operation, this instability problem was found to be closely related not only to the quantity of heat flux but also the difference in heat input rate to each evaporator. For all those problems, it was found that aTCLT with multi-evaporator could operate in a proper way when the thermal loads were evenly distributed to all the evaporator or the maximum power gap were contained under about ±5-7% of the average power input     

An experimental study on turbulent characteristics of an impinging split-triplet injector

This paper presents turbulent characteristics of an impinging F-O-O-F type injector in which fuel and oxidizer impinge on each other to atomize under the different momentum ratio. Water was used as an inert simulant liquid instead of fuel and oxidizer. The droplet size and velocity in the impinging spray flow field were measured using a PDPA. The gradient of the spray half-width(b₂) along the long-axis direction declined throughout the entire spray flow field with increasing the momentum ratio from 1.19 to 6.48. However, the gradient of the half-width(b₁) along the short-axis direction decreased with increasing the momentum ratio. The turbulence intensity and turbulent kinetic energy were converged into the center of the initial region with increasing the momentum ratio. As the momentum ratio increased from MR=1.19 to MR=6. 48, the turbulent shear stress decreased. The results of this study can be used for the design of an impinging type injector for liquid rockets.     

An experimental study of developing and fully developed flows in a wavy channel by PIV

An experimental study is presented for a flow field in a two dimensional wavy channels by PIV. This flow has two major applications such as a blood flow simulation and the enhancement of heat transfer in a heat exchanger. While the numerical flow visualization results have been limited to the fully developed cases, existing experimental results of this flow were simple qualitative ones by smoke or dye streak test. Therefore, the main purpose of this study is to produce quantitative flow data for fully developed and developing flow regimes by the Correlation Based Correction PIV (CBC PIV) and to conjecture the analogy between flow characteristics and heat transfer enhancement with low pumping power. Another purpose of this paper is to examine the onset position of the transition and the global mixing, which results in transfer enhancement. PIV results on the Fully developed and developing flow in a wavy channel at Re=500, 1000 and 2000 are obtained. For the case Reynolds Number equals 500, the PIV results are compared with the finite difference numerical solution.     

An experimental investigation on the pressure characteristics of high speed self-resonating pulsed waterjets influenced by feeding pipe diameter

The destructive power of a continuous waterjet issuing from a nozzle can be greatly enhanced by generating self-resonance in the nozzle assembly to produce a Self-resonating pulsed waterjet (SRPW). To further improve the performance of SRPW, effects of feeding pipe diameter on the pressure characteristics were experimentally investigated by measuring and analyzing the axial pressure oscillation peaks and amplitudes. Four organ-pipe nozzles of different chamber lengths and three feeding pipes of different diameters were employed. Results show that feeding pipe diameter cannot change the feature of SRPW of having an optimum standoff distance, but it slightly changes the oscillating frequency of the jet. It is also found that feeding pipe diameter significantly affects the magnitudes of pressure oscillation peak and amplitude, largely depending on the pump pressure and standoff distance. The enhancement or attenuation of the pressure oscillation peak and amplitude can be differently affected by the same feeding pipe diameter.

     

An experimental investigation on heat transfer performance of pulsating heat pipe

Journal of Mechanical Science and Technology - Heat input and inclination angle are essential factors influencing heat transfer performance of a pulsating heat pipe (PHP). The heat transfer...     

An experimental study on spray and combustion characteristics of LPG for application in direct-injection

As an alternative fuel that can be used in SI engines, LPG is a clean fuel with larger H/C ratio compared to gasoline, low CO₂ emission, and small amount of pollutants such as sulfur compounds. In the Spark-ignition (SI) engine, Direct injection (DI) technology can significantly increase the engine volumetric efficiency and decrease the need for a throttle valve. DI allows engine operation with the stratified charge, which enables a relatively higher combustion efficiency. Stratified charge can be supplied to nearby spark plugs to allow for overall lean combustion, which improves thermal efficiency and can cope with problems regarding emission regulations. In this study, a visualization experiment system that consists of visualization combustion chamber, air supply control system, emission control system, LPG fuel supply system, electronic control system and image data acquisition system was designed and manufactured. For all cases for which ignition was successful, flame propagation image was digitally recorded using ICCD camera, and the recorded flame propagation characteristics were examined. This study, in its results, is expected to make a contribution in terms of important data for the design and optimization of a Spark-ignited direct injection (SIDI) LPG engine.

     

An experimental study on the machining characteristics in ductile-mode milling of BK-7 glass

Glass is considered as one of the most challenging materials to machine because of its high hardness coupled with high brittleness. The challenge, in machining such a brittle material, lies in achieving the material removal through plastic deformation rather than characteristic brittle fracture. It has already been established that every brittle material, no matter how brittle it is, can be machined in ductile mode under certain critical conditions. The critical conditions are material specific, and hence, every material tends to show unique behavior in terms of critical conditions during machining process. This paper outlines the results of an experimental study to determine the critical chip thickness for ductile–brittle transition, chip morphology, and the effect of cutting speed on the critical conditions in peripheral milling process of BK-7 glass. It is established experimentally that the cutting speed affects the chip morphology, machined surface quality, and critical conditions due to possible thermal effects in such a way that ductile–brittle transition phenomenon is facilitated at high cutting speeds.     

Application of dual-plane ERT system and cross-correlation technique to measure gas–liquid flows in vertical upward pipe

The progress of process tomography provides a new method for two-phase flow measurement. The dual-plane electrical resistance tomography (ERT) is combined with the correlation measurement technique to carry out the two-phase flow measurement in which the continuous phase is conductive liquid. The method of the estimation of void fraction and the disperse phase velocity by extracting the eigenvalue of the dual-plane ERT boundary measured data is presented. This method is applied to the transient flow-rate measurement of the air–water two-phase flow in vertical pipe. The information of disperse phase void fraction and distribution variation with time change can be considered adequately, and the estimated value of disperse phase void fraction and velocity can be gained fairly accurately in this method, which provides the data for the calculation of the transient flow-rate. The experiment results indicate that this kind of measurement method is valid when the distance between the upstream and downstream measured cross section is short enough.     

An experimental study of ultrasonic vibration-assisted grinding of polysilicon using two-dimensional vertical workpiece vibration

An experimental study of polysilicon grinding with ultrasonic vibration assistance was presented. The two-dimensional (2D) vertical vibration was applied on the workpiece directly and vibrated perpendicular to both the workpiece and grinding wheel. The grinding forces were measured using a three-component dynamometer, and the surface conditions were examined using a surface profilometer and a laser microscope. The experimental results showed that the grinding force and surface roughness with ultrasonication were much less than those in conventional grinding. In the case of ultrasonication, the wheel speed and worktable feed rate would have a more positive effect on the grinding force decrement/increment, especially for the tangential force while the wheel depth of cut had a negative effect. The surface condition of the ground polysilicon surface was improved with the assistance of ultrasonication. This research indicated that the 2D ultrasonic vibration-assisted grinding technique can be an effective method for the high-efficiency machining of hard brittle polysilicon material.     

An experimental study on three dimensional heat transfer characteristics of simulated electronic chips

Naphthalene sublimation technique is employed to investigate three dimensional heat transfer characteristics of the simulated electronic chips. Experiments are performed for a single chip and chip arrays. In case of a single chip, local heat transfer coefficients on four surfaces of the chip are measured for various gap sizes and air velocities. Dramatic change of local heat transfer is seen on each surface of the chip, and gap size between chip and base plate is found to affect heat transfer significantly. In case of chip arrays, heat transfer characteristics from two-dimensional array of rectangular modules and three-dimensional array of hexahedral modules are investigated. Chip location, gap between chip and base plate and streamwise chip without gap. Fully developed behavior is found from the third row, but it slightly depends on flow conditions. Local and average heat transfer coefficients of three-dimensional modules are a little bit greater than those of two-dimensional modules. The differences in magnitude decrease as the longitudinal chip spacing decreases.