The effect of capillary tube diameter on microhematocrit value

Transfusion ◽  
1986 ◽  
Vol 26 (2) ◽  
pp. 199-202 ◽  
Author(s):  
HM Solomon ◽  
AJ Grindon
Keyword(s):  
Capillary Tube ◽  
Tube Diameter

Numerical Study on Choked Flow of CO2 Refrigerant in Helical Capillary Tube

2018 ◽  
Vol 26 (03) ◽  
pp. 1850027 ◽  
Author(s):  
Pravin Jadhav ◽  
Neeraj Agrawal
Keyword(s):  
Fluid Dynamics ◽  
Present Model ◽  
Capillary Tube ◽  
Numerical Study ◽  
Fundamental Principle ◽  
Tube Diameter ◽  
Published Data ◽  
Flow Conditions ◽  
Pressure Drops ◽  
Choked Flow

This paper presents a numerical study on an adiabatic helical capillary tube employing homogenous and choked flow conditions of a CO2 transcritical system. The theoretical model is based on the fundamental principle of fluid dynamics and thermodynamics. The result of the present model validates with the previously published data. The influence of operating and geometric parameters on the performance of the capillary tube has been evaluated. Flow characterizations of choked and unchoked flow conditions are determined. As the evaporator pressure drops, from unchoked condition to choked state, the percentage change in mass flow rate is minimal. A simulation graph is developed which has been helpful for the design of the helical capillary tube. The choked flow condition in a capillary tube is avoided by either increasing tube diameter of the fixed length tube or decreasing the length of the fixed tube diameter.

Capillary Flow of Yield-Stress Fluids in Microchannels

2006 ◽  
Author(s):  
V. Bertola
Keyword(s):  
Yield Stress ◽  
Flow Regime ◽  
Capillary Flow ◽  
Capillary Tube ◽  
Plug Flow ◽  
Wall Slip ◽  
Critical Distance ◽  
Tube Diameter ◽  
Force Balance ◽  
Theoretical Argument

The wicking of a model yield-stress fluid (hair-gel solution in water) in a capillary tube is studied experimentally. By changing the hair-gel concentration in the solution, the yield stress varied from 5 to 20 Pa. A simple force balance between capillary and viscous forces suggests that the fluid should stop flowing as soon as the wall shear stress reaches the yield value, at a critical distance from the inlet which is independent of the tube diameter. However, this theoretical argument is not confirmed by experiments, which show that the fluid moves well beyond the critical distance determined theoretically, and that there is a well-defined effect of the tube diameter. It is proposed that such behavior may be determined by wall slip, which causes the flow to switch from the Poiseuille flow regime to the plug flow regime.

scholarly journals Movement of gas slug in annular channels with different diameter ratios

2021 ◽  
Vol 2119 (1) ◽  
pp. 012060
Author(s):  
O.N. Kashinsky ◽  
A.S. Kurdumov
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
High Speed ◽  
Capillary Tube ◽  
Tube Diameter ◽  
Outer Tube ◽  
Rise Velocity ◽  
Stress Measurements ◽  
Annular Channels ◽  
Wall Shear

Abstract The motion of gas slugs in annular channels was studied experimentally. The outer tube diameter was 32 mm. The inner tube diameter varied from 4 to 25 mm. The gas slugs were produced by injecting air through a capillary tube. The shapes of gas slugs were studied by high-speed videos. The paper presents data on the rise velocity of gas slugs in the channels, and wall shear stress measurements, performed by electrodiffusional technique. The probes were mounted on both walls of the channel. The evolution of wall shear stress during slug passage was recorded.

Helical Capillary Tube Sizing Charts for All Mixture Ratios of R125, R134a and R32

2016 ◽  
Vol 24 (04) ◽  
pp. 1650022 ◽  
Author(s):  
Worachest Pirompugd ◽  
Somchai Wongwises
Keyword(s):  
Experimental Data ◽  
Gravitational Force ◽  
Flow Model ◽  
Capillary Tube ◽  
Tube Diameter ◽  
Tube Size ◽  
Mixture Ratio ◽  
Size Correction ◽  
Ratio Correction ◽  
Comparison With Experimental Data

This research presents two helical capillary tube sizing charts for R407C and R410A, two correction charts for another tube size, and a correction chart for all mixture ratios of R125, R134a and R32. These charts are obtained from the homogeneous flow model including the effect of gravitational force. It is verified by comparison with experimental data obtained from the published literature. From the model, the sizing charts for a diameter of 1.63[Formula: see text]mm, length of 2.03[Formula: see text]m, and helix diameter of 500[Formula: see text]mm are developed. Two charts for size correction are also developed. The first one is for tube diameter of 0.5–5[Formula: see text]mm and length of 0.25–10[Formula: see text]m. The second one is for helix diameter of 20–1000[Formula: see text]mm. Finally, one more chart for mixture ratio correction is proposed. This chart can be applied to all mixture ratios of R125, R134a and R32.

Comparative Study on a Straight and Helical Capillary Tube for CO2 and R22 Refrigerant

2020 ◽  
Vol 13 (2) ◽  
Author(s):  
Pravin Jadhav ◽  
Neeraj Agrawal
Keyword(s):  
Numerical Model ◽  
Comparative Study ◽  
Capillary Tube ◽  
Tube Diameter ◽  
Tube Length ◽  
Percentage Reduction ◽  
Basic Principles ◽  
Conservation Of Mass ◽  
Coil Diameter ◽  
Mass Flowrate

Abstract A comparative study has been carried out on the adiabatic straight and helical capillary tube, using a CO2 and R22 refrigerant. The numerical model for CO2 and R22 is developed using the basic principles of conservation of mass, momentum, and energy. The effect of coiling in the helical capillary tube is compared with a straight capillary tube for CO2 and R22 refrigerant. Compared with the straight capillary tube, the percentage reduction in mass flowrate in the helical capillary tube is calculated with a change in coil diameter, tube diameter, and length. As the coil diameter increases from 30 mm to 150 mm, the percentage reduction in mass is from 5.8% to 2.2% in CO2, and 5% to 1.6% in R22. For helical capillary tube with 50 mm coil diameter, as the tube diameter increases from 1 to 1.5 mm, the percentage reduction in mass flowrate with CO2 refrigerant is from 2.65% to 4.96%, however, for R22 it is from 2.43% to 4.24%. Similarly, as the capillary tube length increases from 1.3 m to 1.8 m, the percentage reduction in mass with CO2, with 50 mm coil diameter is 4.44–4.55%. However, the percentage reduction in mass with R22 is 3.71–3.85%. Moreover, compared with the straight capillary tube, the percentage reduction in length in a helical capillary tube with coil diameter 50 mm is 16% for CO2 and 9% for R22 refrigerant.

Choked Flow Behavior of CO2 Refrigerant Flowing Through the Spiral Capillary Tube

2020 ◽  
Vol 28 (03) ◽  
pp. 2050024
Author(s):  
Pravin Jadhav ◽  
Neeraj Agrawal
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Graphical Representation ◽  
Capillary Tube ◽  
Flow Behavior ◽  
Tube Diameter ◽  
Tube Length ◽  
Flow Conditions ◽  
Choked Flow

The flow characteristics of CO2 refrigerant are numerically studied for an adiabatic spirally coiled capillary tube employing choked flow conditions. The mass, momentum and energy conservation equations are used to develop a numerical model. The existing model is verified with the published results. The choked flow behavior at various geometric parameters viz. tube diameter and spiral pitch is studied. Similarly, the influence of these parameters on the mass flow rate through the tube is observed. A significant change in mass flow rate is due to a change in tube diameter, whereas a minimal variation is observed with the change in surface roughness and spiral pitch. Moreover, it is observed that the coiling effect has a significant influence on the flow behavior of the spiral capillary tube. As the pressure decreases, from unchoked to the choked pressure in the evaporator by 63.46%, the mass flow rate increases by 9.46% only. The capillary tube choking is circumvented by increasing spiral pitch, tube diameter and decreasing the length of the tube. A unique nomogram is developed that gives the best understanding of choked and unchoked flow conditions, that graphical representation is useful to design the spirally coiled capillary tube. By using that, the choked length is identified for the known mass flow rate, even more, the choked mass flow rate is known for a given tube length. Moreover, for the given tube length and evaporator temperature, a nomogram is useful to the known choked values of mass flow rate and exit values of the evaporator pressure and quality of refrigerant.

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