Mixing of Fluids with Different Momentum ratio

Abstract

The problem concerned with the mixing of mutually soluble liquids in turbulent flow in the pipe. In this problem, we use the momentum ratio that decides the velocity of fluids. Hot fluid at 30C and cold fluid at 10C at different velocities. In this, we observe the variation of the temperature of the fluid along the length, diffusion nature of the fluid and mixing efficiency.

Introduction

Mixing can be defined as an operation which reduces the degree of nonuniformity of all properties of a system, single or multiphase with one or many components. During such motion, because of convective transfer of matter with velocity varying across the diameter of the pipe, and turbulent diffusion, mixing of the liquids and formation of a mixture region.

Three basic mechanisms, either singly or in combination, can be available in a mixing operation; molecular diffusion, eddy diffusion, and bulk or convective flow. Molecular diffusion is spontaneous, driven by the gradients of concentration and temperature and can be found in the mixing of miscible liquids of low viscosities and all gases. In most practical operations it is a slow process and eddy diffusion must be superimposed on it to speed up mixing. Eddy diffusion results from Turbulence in the flow of fluids and requires greater energy input. In the mixing of fluids thus, Viscosity is the prevailing property of the system resisting mixing and the lower it is the easier the turbulent, conditions can be achieved and the quicker the mixing operation. 

Momentum Ratio

Momentum Ratio = Cold Fluid Velocity/Hot Fluid Velocity

Heat gain by cold Fluid = Heat loss by Hot Fluid

Conservation of Energy

Mixing Tee

Mixing Tees utilizes a specifically engineered internal geometry to efficiently mix two fluid streams into one combined stream. Mixing Tees are ideal for microbore or analytical gradient HPLC. These mixing tees are specifically designed for high-pressure applications.

Short Pipe with Momentum Ratio 2

Hot and Cold air mixes in a T-type junction. Air enters the main pipe from a hot inlet at 3m/s at 30-degree centigrade. It mixes with cold air coming through a smaller pipe, with inlet 6 m/s and temperature of 10-degree centigrade.

Short Pipe with Momentum Ratio 4

Hot and Cold air mixes in a T-type junction. Air enters the main pipe from a hot inlet at 3m/s at 30-degree centigrade. It mixes with cold air coming through a smaller pipe, with inlet 12 m/s and temperature of 10-degree centigrade.

Comparison of Short Pipe with Different Momentum Ratio

Long Pipe with Momentum Ratio 2

Hot and Cold air mixes in a T-type junction. Air enters the main pipe from a hot inlet at 3m/s at 30-degree centigrade. It mixes with cold air coming through a smaller pipe, with inlet 6 m/s and temperature of 10-degree centigrade.

Comparision of Short and Long Pipe with the Same Momentum Ratio

Conclusion

1. Increasing the length of the pipe is not most affecting the outlet average temperature.
2. Increasing the velocity of the cold air makes the better and we can see an appreciable temperature difference in the outlet temperature in comparison to low velocity.
3. Increase in flow velocity helps in mixing nature.