How Does a Hot Air-Drying Oven Work
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How Does a Hot Air-Drying Oven Work

Views: 100     Author: Site Editor     Publish Time: 2023-09-20      Origin: Site

Hot air-drying ovens play a pivotal role in various industries and laboratories. They are essential for processes like drying, sterilization, and heat treatment. If you want to get into hot air-drying oven, it's important to know how it works. This article will take you to understand how it works from three aspects: important components of hot air-drying oven, hot air-drying oven working principles, and how to control the temperature and humidity of hot air-drying oven.

Main work components

The equipment usually consists of a heater, circulation fan, control system, and oven.

The heater generates heat and transfers it to the air in the oven.

Heater/Heat source

The heater/heating source generates heat and transfers it to the air in the oven.

The heating elements/heating sources of hot air drying ovens usually have the following types:

1. Resistance wire heater: This is the most common type and uses resistance wire, heating tubes, or other electrical heating elements to generate heat. It includes one or more resistance wires. When current passes through, the resistance wires will generate heat and transfer the heat to the box, thereby increasing the temperature and achieving drying.

2. Heating tube: A heating tube is a tubular element that usually contains a resistance wire or heating element that generates heat by passing an electric current inside the heating tube.

3. Infrared radiation heater: This type of heating element uses infrared radiation to heat the sample rather than transferring heat by conduction or convection. They generally heat items more quickly.

4. Microwave heating system (in some cases): Some hot air drying ovens may use microwave heating technology to heat items through microwave radiation to remove moisture more effectively.

5. Steam heating: Some hot air drying chambers can be heated by introducing steam into the chamber. Steam provides uniform heating and does not introduce oxygen during drying, helping to maintain the chemical properties of the sample.

6. Natural gas or liquefied petroleum gas (LPG) heating: Some industrial drying ovens use natural gas or LPG as the heating source. These gases can be burned to produce high-temperature hot air for drying items.

7. Oil heating: Some hot air drying ovens use hot oil as the heating medium. After the hot oil is heated, the heat is transferred to the hot air through the heat exchanger and then sent into the box.

The selection of these heating elements and heating sources depends on the design and application requirements of the hot air drying oven. Different heating elements may vary in temperature control, heating speed, and energy efficiency.

Circulation fan

Circulation fan is used to force circulation and ventilate the air within the box. This function has the following important functions:

1. Temperature uniformity: Forced ventilation ensures a more even distribution of air temperature inside the box. This helps prevent hot or cold spots with uneven temperatures inside the hot air drying chamber, ensuring that samples are treated equally throughout the drying process.

2. Humidity Uniformity: Ventilation also helps distribute humidity evenly within the chamber, avoiding the occurrence of humidity gradients. This is important for drying moisture-sensitive samples as it reduces the impact of humidity differences on sample properties.

3. Fast Drying: Forced ventilation removes moisture from the heated air more quickly, speeding up the drying process. This is important for applications that require rapid drying.

4. Air circulation: The ventilation function ensures that air is not trapped in the hot air drying box, thus helping to maintain the freshness of the air inside the box and preventing the accumulation of odors or harmful gases.

In short, the forced ventilation function can improve the drying efficiency of the hot air drying oven and ensure that samples are processed evenly and quickly. This is important for many laboratory and industrial applications.

The control system

Can control the temperature of the heater and the speed of the circulating fan to achieve the required temperature and drying time.

Hot Air Drying Oven 1

The principle of hot air drying

The overall working principle

The air around the heat source is heated by the fan of the heating equipment, and the heated hot air is sent into the drying equipment, where the hot air comes into contact with the material. Hot air is used to heat and evaporate the surface moisture of the material to achieve the purpose of drying. The evaporated moisture is then discharged by the exhaust system in the drying equipment. Adjusting the hot air volume and heating temperature can improve the efficiency of hot air drying.Adjust the wind direction so that the wind direction is towards the object being heated, which is more conducive to drying.

Need to pay attention to:

The hot air speed cannot be lower than the required speed, otherwise, poor heat dissipation on the surface of the air duct will burn out the hot air heater.

The wind speed should not be too high, because some energy will be lost during the wind circulation process. Only by appropriately selecting the fan pressure and air volume can the best drying effect be achieved.

Working principle breakdown

Hot air control system

The fan adopts frequency converter speed control, and the thermostat is used to collect the temperature in the hot air drying box to adjust the frequency of the frequency converter to control the running speed of the fan, forming a closed-loop control mode. (The low frequency of the fan is not less than 10Hz)

The hot air heater uses a heating tube to heat the air, and a temperature sensor is set at the air outlet. The temperature control meter collects temperature signals to control the thyristor power regulator.

The thyristor power regulator controls the power adjustment of the hot air heater to keep the temperature of the hot air outlet stable. When the temperature in the drying box does not reach the set temperature, the fan speed increases, and the control part of the hot air heater, the thyristor controller, adjusts the electric heating power to increase the output.

When the temperature reaches the required temperature, the fan speed gradually slows down. In the control part of the hot air heater, the thyristor controller adjusts the electric heating power and reduces the output.

Hot air circulation drying oven air circulation system

The fan self-priming circulation air supply method is adopted to ensure uniform and efficient air circulation.

The air source is driven by a circulating air supply motor (using a frequency converter to adjust the speed) to drive the wind wheel through the heater to send the hot air out, and then to the inner chamber of the oven through the air duct. The used air is then sucked into the air duct to become an air source for recirculation. Use with heat. Ensure indoor temperature uniformity.

When the temperature value swings due to the door opening and closing action, the air supply circulation system quickly returns to the operating state until it reaches the set temperature value. The hot air circulation drying box is equipped with observation holes and lighting devices, and a hot air exhaust valve is installed on the upper part of the hot air circulation drying box.

How to control the temperature and humidity of the hot air dryer

Use a steam humidifier

A steam humidifier sprays steam inside the oven to increase the humidity in the air. The humidity inside the oven can be controlled by setting the switch and spray time of the humidification device. In addition, the temperature and humidity sensors of the humidification device can automatically detect the humidity and temperature inside the oven and make automatic adjustments.

Use a temperature control device

The temperature control device can automatically adjust the power of the heater according to the temperature inside the oven, thereby controlling the temperature inside the oven. The temperature inside the oven can be controlled by setting the temperature range and accuracy of the temperature controller.

Use a circulating fan

The circulating fan in the hot air circulation oven can circulate the air, thereby improving the uniformity of temperature and humidity inside the oven. The airflow inside the oven can be controlled by setting the speed and air volume of the circulation fan.

Install the exhaust vent

The exhaust vent can remove the humid air inside the oven, thereby keeping the humidity and temperature inside the oven stable. The humidity and temperature inside the oven can be controlled by adjusting the size and position of the exhaust port.

To sum up, the above methods are commonly used methods to control humidity and temperature in hot air circulation ovens. In actual use, these methods need to be used in a reasonable combination according to the different properties and drying requirements of the materials to achieve the best drying effect and quality.

Understanding how a hot air drying oven works can be helpful as you choose between the different types. If you want to know other information about it, welcome to contact us.




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