With its powerful motor and continuous high torque output, the overhead stirrer is the ideal stirring tool for mixing, homogenizing, and high viscosity media handling tasks. It is commonly used in many industries such as environmental analysis, biology, new materials, food, paints and coatings, pharmaceuticals, petrochemicals, and polymer research.
In order to achieve the ideal mixing effect, in addition to selecting the appropriate torque of the overhead stirrer, the user should choose the appropriate stirring paddle and motor according to the characteristics of different materials and the purpose of mixing. When the overhead stirrer is in operation, the sample flows in the right direction and at the right speed to achieve the ideal processing results.
Types of Paddles for Overhead Stirrer
Common stirring paddles for overhead stirrers can be categorized as vane, spiral, radial flow, and anchor stirring paddles.
Radial stirring paddles can provide two radial flows for the sample above and below their paddles, which can provide better dispersion due to the larger shear force generated, and are very suitable for gas-liquid dispersion, solid-liquid suspension, and other applications.
Blade mixing paddle structure is relatively simple, its paddle is usually composed of 1 to 4 blades. According to the different shapes and angles of its blades, it can be divided into fan blade type, cross type, flat type, rotating around the axis, half-moon mixing paddle. If the container used by the user is a fine-mouthed bottle, you can also choose to fold or tilt the blade type stirring paddle. The main flow direction of the vane stirring paddle is tangential, the stirring effect is more gentle, and is widely used in the mixing of mutually soluble liquids, dispersion of immiscible liquids or solid-liquid phase suspension applications.
When the spiral stirring paddle is stirred, the sample flows axially according to the direction of rotation of the paddle, forming a circulation in the vessel. Recommended for homogenization or suspension processing in liquids.
Anchor paddles have larger blade diameters to minimize sample deposition on the vessel wall and are suitable for low-speed mixing tasks with medium to high viscosity samples.
In addition to these common stirring paddles, Scitek offers the VISCO JET® stirring paddle, which utilizes the cone principle to create turbulence at the cone end through acceleration, displacement, and hysteresis, and agitates the sample to allow fluid flow.
Overhead stirrer motor: How to choose
What is the difference between different motors when choosing an overhead stirrer?
Overhead stirrer is an experimental equipment for liquid mixing and stirring, which is suitable for the experimental fields of health products, food, biology, physical and chemical, cosmetics, reagents and so on. Speed range, control accuracy, maximum mixing viscosity, maximum torque, maximum mixing volume, motor input/output power, and motor type are all key to evaluating the performance of an overhead stirrer. Among them, the motor type usually has two kinds of brushless motor and brushed motor, so what is the difference between these two kinds of motors, and which kind of motor should we choose when picking an overhead stirrer for an overhead stirrer?
1. Structural differences
Brushed motor: A brushed motor consists of a rotating part (rotor) and a fixed part (stator), in which the rotor makes electrical contact with the brushes on the stator through brushes.
Brushless motor: Brushless motor consists of rotor and stator, but without brush and gun structure.
2. Principle of operation
Brushed motor: powered by DC power supply, the current passes through the brushes and lances into the stator coil, generating a magnetic field that interacts with each other to cause the rotor to rotate.
Brushless motors: Brushless motors are controlled by electronic speed controller (ESC) to input alternating current (AC) or direct current (DC) power into the rotor coil, and the rotor movement is realized through induction and driving circuit.
3. Maintenance
Brushed motors: Brushed motors have wear and tear contact parts (brushes and lances) that require regular replacement and maintenance.
Brushless motors: Brushless motors do not have brushes and lances and therefore have fewer wear parts and require less maintenance.
4. Efficiency
Brushed motors: Brushed motors are usually less efficient due to the friction and energy loss caused by the contact between the brushes and the rotor.
Brushless motors: Brushless motors have higher efficiency due to the reduction of energy loss through precise control of how the rotor coils are powered by an electronic speed controller.
5. Speed range
Brushed motors: Brushed motors are usually suitable for lower speed applications. This is because contact between the brushes and the rotor can cause problems at high speeds.
Brushless motors: Brushless motors allow for a higher speed range due to the lack of brush contact.
6. Control Complexity
Brushed motors: Brushed motors can be controlled by simple circuits, such as using a varistor to vary the supply voltage for speed regulation.
Brushless motors: Brushless motors require an electronic governor (ESC) for precise speed and torque control, and therefore have higher control complexity.
7. Noise and Vibration
Brushed motors: Brushed motors are prone to noise and vibration due to the friction and mechanical contact between the brushes and the lance.
Brushless motors: Brushless motors usually have less noise and vibration because they have no contact parts.
To sum up, it is obvious that brushless motor will be better than brushed motor, and we can give priority to the type of brushless motor when selecting the overhead mixer.
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