Definition
A homogenizer is a type of laboratory equipment used to achieve uniform dispersion, mixing, or emulsification of materials in a liquid medium. It converts immiscible phase states (such as oil-water, solid-liquid) into a homogeneous suspension or emulsion by applying shear, impact, and turbulent effects. This equipment is widely used in sample preparation and process simulation in food, chemical, environmental protection, materials and other fields to ensure the reproducibility and stability of experimental results.
Principle
The core working principle of the homogeneous agitator is based on the conversion of mechanical energy and hydrodynamic effects. A narrow gap is formed between the rotating rotor and the stator, and when the material passes through these gaps, it is subjected to a combination of high-speed shear, hydraulic shear, cavitation effect and turbulent mixing. Rotor speeds typically reach thousands to tens of thousands of revolutions per minute, inducing high velocity gradients locally in the material. In this process, droplets or solid particles are broken down to smaller sizes, typically down to the millimeter or nanometer level, allowing for homogenization. Energy transfer follows the laws of momentum conservation and energy dissipation, with Reynolds number (Re) and power standard (Np) used to quantify flow state and mixing efficiency.
Example formula: Shear rate γ The calculation can be approximated as: γ = (π × d × n) / h, among them d is the rotor diameter,n is the rotational speed,h It is the gap between the rotor and the stator.
Measurement method
The performance evaluation of homogeneous agitators often relies on the following measurement methods:
Particle size distribution analysis: Laser diffraction or dynamic light scattering technology is used to determine the size distribution of particles or droplets in the treated sample to evaluate the homogenization effect. Common indicators include D10, D50, D90, and span values.
Rheological measurements: Changes in viscosity, energy storage modulus and loss modulus of samples are detected by rotating or oscillating rheometers, reflecting mixing uniformity and structural stability.
Microscopic observation: Optical microscope or electron microscope directly observes the morphological differences before and after homogenization, especially suitable for emulsions or suspensions.
Stability testing: Leave the sample for a certain period of time (e.g., 24 hours or 7 days) to record the degree of stratification, precipitation, or flocculation to quantify the durability of the homogenization effect.
Influencing factors
The use of homogenizers is subject to a variety of parameters, including:
rotor speed and linear speed: The higher the speed, the greater the shear force, which can break up particles or droplets more effectively, but it can also cause excessive heating or foaming.
Gap between rotor and stator: Smaller gaps increase local shear gradients, contributing to finer homogenization but potentially exacerbating equipment wear or clogging.
Material properties: Viscosity, surface tension, density difference and initial particle size directly affect the difficulty of homogenization. High viscosity systems require greater torque support.
Processing time and temperature: The effect is insufficient when the homogenization time is insufficient, and too long time may cause the degradation of heat-sensitive substances. Increasing temperature can reduce viscosity, but it needs to be controlled within a reasonable range.
Probe or container geometry: The shape of the bottom of the container, the immersion depth and position of the probe affect the flow field distribution, which in turn changes the mixing efficiency.
Application:
Homogeneous agitators play a key role in several laboratory sectors:
Food Science: Prepare stable emulsions (such as dairy products, sauces), suspensions (such as beverages) and gel systems to ensure the taste and texture of the product.
Chemicals & Materials: Synthetic nanomaterials, polymer dispersions or coatings, etc., to improve material properties through uniform dispersion.
Environmental Testing: Used for the homogenization of particulate matter in soil or water samples, or for demulsification studies of grease and emulsified wastewater.
Biotechnology (non-medical field): Homogenization of nutrient solutions in cell fragmentation, enzymatic hydrolysis reactions, or microbial cultures to enhance mass transfer efficiency.
R&D of daily chemical products: In the production of shampoos, skin care products, etc., the homogenization process ensures the uniform distribution of active ingredients and the stability of the system.
Selection
The selection of homogenized agitators should be combined with actual experimental needs, focusing on the following aspects:
Handling volume and container fit: Choose a probe or stirring head with the corresponding power according to the sample volume (from milliliters to liters), and ensure that the probe is immersed in no less than one-third of the diameter of the container.
Speed range and control accuracy: A wide speed adjustment range (e.g. 1000 to 20000 rpm) accommodates different viscosity systems, and the digital display and speed feedback function improve reproducibility.
Material and corrosion resistance: The probe should be made of corrosion-resistant materials such as stainless steel or titanium alloys to meet the requirements of food contact, acid-base, or organic solvent experiments.
Noise and heat dissipation design: Low-noise motor and effective heat dissipation structure help maintain operating comfort and equipment longevity during long runs.
Safety and ease of cleaning: It has an anti-splash cover, overload protection and a detachable probe for maintenance and cross-contamination prevention and control.