Related Experiment Video
Updated: Jul 5, 2026

08:01
The Diffusion of Passive Tracers in Laminar Shear Flow
Published on: May 1, 2018
Characterization of two-phase flow regimes in horizontal tubes using 81mKr tracer experiments
Jean Oriol1, Jean Pierre Leclerc, Philippe Berne
1LPAC, CEA Grenoble, 17, rue des Martyrs, 38054 Grenoble Cedex 9, France.
Summary
This study demonstrates tracer experiments for diagnosing flow mal-distribution in two-phase heat exchangers. Gas tracer (81m)Kr and scintillators accurately characterized flow regimes and velocities.
Area of Science:
- Chemical Engineering
- Fluid Dynamics
- Process Monitoring
Background:
- Non-intrusive techniques are crucial for diagnosing heat exchanger faults during operation.
- Tracer experiments offer a viable method for online fault diagnosis in heat exchangers.
- Applying tracer experiments to multi-phase systems presents unique challenges.
Purpose of the Study:
- To evaluate the feasibility of tracer experiments for diagnosing flow mal-distribution in multi-phase heat exchangers.
- To investigate the application of tracer experiments in a simplified two-phase flow system.
- To characterize two-phase flow regimes and measure phase velocities using tracer techniques.
Main Methods:
- Utilized Krypton-81m ((81m)Kr) as a gas tracer.
- Employed collimated Sodium Iodide (Thallium-activated) [NaI(Tl)] crystal scintillators as detectors.
- Analyzed tracer response signals to determine flow characteristics.
Main Results:
- The specific shape of the tracer response successfully characterized two-phase flow regimes.
- Accurate estimation of gas and liquid phase average velocities was achieved.
- Volumetric void fraction was successfully determined.
- Results showed good agreement with previous liquid tracer experiments and literature correlations.
Conclusions:
- Tracer experiments, using (81m)Kr gas, are effective for diagnosing flow mal-distribution in two-phase horizontal tube flows.
- This method allows for characterization of flow regimes and accurate measurement of phase velocities and void fraction.
- The findings support the potential of tracer experiments for online monitoring of multi-phase heat exchangers.
Related Concept Videos
Steady, Laminar Flow in Circular Tubes
Hagen-Poiseuille flow describes a viscous fluid's steady, incompressible flow through a cylindrical tube with a constant radius R. This flow profile is often applied to understand fluid transport in narrow channels, such as capillaries. It serves as a foundational example of laminar flow. In this model, cylindrical coordinates (r,θ,z) are used to describe the radial (r), angular (θ), and axial (z) dimensions within the tube. For Hagen-Poiseuille flow, the velocity profile is purely axial,...
Steady, Laminar Flow Between Parallel Plates
Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.
General Characteristics of Pipe Flow II
When fluid enters a pipe, it first passes through the entrance region, where the velocity profile adjusts due to viscous effects. In this region, a boundary layer forms along the pipe walls and grows until it fully occupies the pipe's cross-section. Once the boundary layer merges, the flow becomes fully developed, with a steady velocity profile that remains consistent along the pipe's length.
The distance to reach a fully developed flow is called the entrance length and depends on the flow...
The distance to reach a fully developed flow is called the entrance length and depends on the flow...
General Characteristics of Pipe Flow I
Pipe flow refers to the movement of fluids within fully enclosed conduits, typically cylindrical in shape, such as water pipes or hydraulic hoses. These conduits are designed to withstand high-pressure gradients that drive fluid movement, contrasting with open-channel flows, where gravity is the primary driving force. Rectangular conduits, like air conditioning and heating ducts, generally operate at lower pressures and are less suited for high-pressure applications.
The classification of fluid...
The classification of fluid...
Poiseuille's Law and Reynolds Number
Any fluid in a horizontal tube can flow due to pressure differences—fluid flows from high to low pressure. The flow rate (Q) is the ratio of pressure difference and resistance through a horizontal tube. The greater the pressure difference, the higher the flow rate. The flow resistance is expressed as:

