Radiant tubes are critical heat-transfer components used in industrial furnaces and heat treatment systems. They are designed to transfer heat indirectly to the furnace atmosphere and processed materials while isolating the combustion process from the heating chamber. Our radiant tubes are manufactured by centrifugal casting using high-temperature heat-resistant alloys. Typical materials include Cr-Ni heat-resistant steels and other customized alloy grades selected according to the operating temperature and furnace atmosphere. Compared with fabricated tubes, centrifugally cast radiant tubes offer superior high-temperature strength, oxidation resistance, carburization resistance, and longer service life. Depending on the furnace design and operating conditions, radiant tubes can be supplied in straight, U-type, W-type, P-type, or customized configurations.
What is Radiant Tube
Definition and Function
Radiant tubes are tubular heating elements designed to emit radiant heat. They are typically made of durable material such as stainless steel, ensuring high-temperature resistance as well as longevity. Used in extremely demanding environments, radiant tubes are leak-proof and corrosion-resistant, among other unique features. Radiant tubes are primarily used in heating systems, where their ability to transfer heat through radiation plays a crucial role.
Exceptional Temperature Capability
Radiant tubes are seamless tubes that are made up of heat-resistant materials like iron-chromium-aluminium alloys, nickel-based alloys, etc. Stainless steel tubes are commonly used due to their excellent heat resistance and durability. Operating temperatures of up to 1100 °C are supported by these alloys. Radiant tubes can function independently or in conjunction with bundle rod heaters. When used with bundle rod heaters, they can be used for temperatures up to 1400 °C and have superior performance.
Benefits of Radiant Tubes
Outstanding Energy Cost Savings
Radiant tubes offer significant reductions in running costs. Not only can they continue to heat the space even when turned off, but they are also a low-energy heating option. You may save up to 65% on your future fuel costs and reduce your carbon footprint. Although radiant tubes are a low-energy heating system, they provide very even heat coverage throughout the desired space.
Consistent Infrared Heat Distribution
Unlike other heating systems, radiant tubes do not directly heat the air. Instead, they operate similarly to the sun by heating via infrared waves. These waves travel through the air and dissipate as heat onto people and objects in the room, creating a consistent room temperature. This makes radiant tubes ideal for areas with high air infiltration, such as warehouses with open bay doors.
Rapid Thermal Recovery Speed
Radiant tubes heat the room to the desired temperature within just a few minutes, minimizing energy wasted during warm-up times. If the room is exposed to a colder temperature, such as when a door is opened, the system can quickly recover and reheat the space. Because the tubes direct heat downward towards the desired space and its occupants, heat loss through the roof is minimized compared to other systems.
Simple Installation and Maintenance
This type of system is very easy to install, though it is advisable to use a professional heating specialist to ensure safe and correct installation. Once installed, it is a low-maintenance system that operates without the need to bleed radiators or check water pressure, unlike more traditional heating systems. Radiant tube systems are also easy to control, allowing you to quickly adjust the temperature for different areas. You can set operating times to ensure that the space is warm for employees as soon as they arrive, and set it to switch off an hour before the end of the working day, knowing that the space will remain at the correct temperature.
Radiant Tubes Uses
Controlled Atmosphere Heat Treatment
Radiant tubes are used for heat treatment processes where a protective atmosphere is required.
Uniform Furnace Temperature Distribution
They provide uniform temperature distribution in a furnace, allowing for precise control over both heating and cooling temperatures.
Combustion Gas Material Separation
Radiant tubes are beneficial in situations where the material being heated needs to be separated from combustion gases and where there are significant air changes.
Liquid And Salt Heating
They are used for heating liquids and as a heat source in salt melting furnaces.
High Operational Cost Efficiency
Ideal for applications requiring low operating costs, high efficiency, and minimal noise.
Slender Component Precision Heating
Suitable for heating slender components with a small number of burners, such as in roller furnaces and small pusher furnaces.
Heating Efficiency of Radiant Tubes
Core Heating Efficiency Principles
The heat energy in heating furnaces is generally provided by the combustion of combustible gases such as natural gas. However, the harmful gases generated during this combustion can negatively affect the environment required for heat treatment in the furnace. To address this, the radiant tube was invented to burn combustible gas within the tube itself.
Thermal energy is then radiated into the furnace by the radiant tube, preventing harmful gases from contaminating the furnace environment. Since the radiant tube heats the workpiece through tube wall radiation, its heating efficiency directly impacts the effectiveness of heat treatment. Thus, the heating efficiency of the radiant tube is a key characteristic.
Historical Tube Design Evolution
The earliest radiant tube, invented and used in Germany in the 1930s, was a single-layer straight tube that passed horizontally or vertically through the furnace. U-shaped radiant tubes were introduced in the early 1950s. To improve heating efficiency, the W-type radiant tube was developed from the U-type.
With technological advancements, the P-type radiant tube, a typical example, emerged. Further innovations aimed at increasing heating efficiency led to the creation of hemp-surfaced radiant tubes. These tubes, compared to smooth-surfaced radiant tubes, increased the heating area by more than 30%, significantly enhancing heating efficiency. The evolution of radiant tubes generally follows two technological routes:
Evolution of Geometric Shapes
The evolution of geometric shapes involves coordination between subsystems and supersystems. The path includes: straight lines → 2D curves → 3D curves → complex curves. Currently, the system is at the 2D curve stage. Designing radiant tubes as 3D curves, such as corrugated tubes, can further improve heating efficiency.
Evolution of Surface Shape
The evolution of surface shape follows: smooth surface → convex surface → rough surface → active material. The system is currently evolving with raised surfaces. Increasing the number of surface protrusions or designing the surface as rough can enhance heating efficiency.
Uniformity of Temperature Distribution on the Surface of the Radiant Tube
The uniformity of temperature distribution on the surface of a radiant tube is a crucial performance indicator. It affects the heating capacity, quality, and service life of the tube. Currently, U-type and W-type radiant tubes are the most commonly used. In the original design, radiant tubes were equipped with a burner at one end, causing significant temperature differences between the two ends. To improve temperature uniformity, core blocks were added to the tube to fill it with high-temperature gas, enhancing convective heat transfer and increasing the temperature at the tail. Later, to further improve temperature uniformity, burners were installed at both ends, and pulse combustion technology was introduced. Additionally, by adjusting the combustion reversing time of the burners at both ends, temperature uniformity could be further improved.
Temperature uniformity is closely related to the length of the flame. Initially, burners could only perform single-stage combustion. Two-stage burners, which allow the control of primary and secondary air ratios, were developed to adjust flame length and improve temperature uniformity. The advent of regenerative combustion technology has significantly enhanced temperature uniformity. Experiments have shown that as the air preheating temperature increases, the maximum temperature difference on the surface of the radiant tube decreases, and the temperature unevenness coefficient also drops.
There are two technological evolution routes in this process:
Evolutionary Path to Supersystem
The path involves transitioning from a single system → dual system → multiple systems. According to this route, the system is in the final stage of evolution, with heat storage bodies replacing control systems.
Frequency-Coordinated Evolutionary Path of a Single Object (Flame)
The path involves continuous motion → pulse → periodic action → increased frequency → resonance. Currently, the system is in the cyclical stage of evolution. Further improvement can be achieved by enhancing the combustion cycle of burners on both sides or by increasing the frequency of alternating nozzles on both sides to improve temperature distribution uniformity.
7 Things to Consider When Choosing and Installing Radiant Tube Heaters
Radiant tube heaters are an efficient and cost-effective solution for heating industrial spaces, warehouses, and commercial buildings. However, making the wrong choices during selection and installation can lead to suboptimal performance, energy wastage, and safety hazards. In this article, we'll delve into the common pitfalls to avoid when dealing with gas tube heaters.
Incorrect Sizing
Mistake: Choosing an infrared heater that's too small or too large for your space can result in inefficient heating. An undersized heater won't provide adequate warmth, while an oversized one may waste energy and cause discomfort.
Solution: Calculate the required heat output based on the dimensions of your area, insulation levels, and desired temperature rise.
Neglecting Clearance Distances
Mistake: Failing to maintain proper clearance distances between radiant tube heaters and combustible materials (such as walls, ceilings, and stored items) can lead to fire hazards.
Solution: Follow manufacturer guidelines for minimum clearance distances. Install heat shields or protective barriers where necessary.
Poor Placement
Mistake: Incorrect placement of infrared heaters can lead to uneven heating, cold spots, and discomfort for occupants.
Solution: Position heaters strategically to achieve uniform heat distribution. Consider factors like ceiling height, obstructions, and airflow patterns.
Ignoring Ventilation Requirements
Mistake: Radiant tube heaters require adequate ventilation to ensure complete combustion and prevent the buildup of harmful gases.
Solution: Provide sufficient fresh air intake and exhaust vents. Regularly inspect and clean the burner assembly and flue system.
Skipping Regular Maintenance
Mistake: Neglecting routine maintenance can reduce efficiency, increase energy consumption, and shorten the lifespan of your gas tube heater.
Solution: Schedule annual inspections, clean the reflectors, check gas connections, and replace worn-out components promptly.
Incorrect Gas Supply
Mistake: Using the wrong gas type or inadequate gas pressure can affect heater performance and safety.
Solution: Verify the correct gas type (natural gas or propane) and ensure proper pressure levels. Consult a licensed gas technician if needed.
DIY Installation Errors
Mistake: Improper installation by inexperienced individuals can compromise safety and functionality.
Solution: Hire a qualified HVAC technician for installation. They'll ensure proper alignment, secure mounting, and adherence to safety standards.
How to Choose a Radiant Tube for Your Furnace and Budget
Determine Your Furnace Needs
Before exploring the various options available, it's important to assess your specific furnace requirements. Consider the type of fuel your furnace uses, the desired heat output, and the size of the heating space. Additionally, evaluate any industry regulations or safety standards that may apply. By understanding these factors, you can clearly define the type and specifications of the radiant tube needed for your furnace.
Consider Tube Material and Design
Radiant tubes are typically made from stainless steel, alumina, or ceramic materials. Each material has unique properties, so it's essential to choose one that meets your furnace's requirements and fits your budget. Stainless steel is popular due to its durability and suitability for high-temperature applications. Alumina and ceramic tubes offer excellent heat resistance but tend to be more expensive. Assess the temperature range your furnace operates within and select a material that balances cost and performance effectively.
Additionally, pay attention to the design of the radiant tube. The shape, size, and placement of the burner ports, as well as the arrangement of the fins or baffles, are crucial for efficient heat transfer. Opting for a well-designed radiant tube can maximize heat transfer, improve fuel efficiency, and reduce long-term maintenance costs.
Set a Realistic Budget
While investing in a quality radiant tube for your furnace is important, setting a realistic budget is equally crucial. Start by researching prices and product reviews to understand the market range. Consider factors such as initial purchase cost, installation expenses, and long-term maintenance requirements. Remember that a higher upfront investment may save you money in the long term by providing better performance, energy efficiency, and durability.
Partner with Trusted Global Suppliers
China Welong was founded in 2001, which is a professional international integrated supply chain service provider. We are concentrating on the industrial customized metal products, aiming at empowering the world with the finest supply chain of China. Since its establishment, we have been offering Supplier Development & Management, Purchasing Supervision, and ISO 9001:2015 certified Quality Control services in China to many leading enterprises in the fields of International Industrial Manufacturing, Oil Drilling, aerospace, and high-end medical treatment.Welong is ready to meet your exact specifications. Contact our team today at metal@welongpost.com to discuss your radiant tube requirements, your material selection, or your custom manufacturing project.
Conclusion
Radiant tubes are essential for optimizing industrial furnace performance. Their material selection, manufacturing process, and design evolution ensure high efficiency, uniform temperature distribution, longevity, and low operating costs. Proper selection, installation, and maintenance maximize the benefits of radiant tubes, improving operational efficiency and reliability in high-temperature industrial processes.
FAQ
Q1: What does a radiant tube heater do?
A: A radiant tube heater offers a highly efficient solution for warming large areas. Its capacity to conserve energy enhances its appeal, making it a favoured option in diverse settings, including commercial, industrial and outdoor environments.
Q2: How do radiant tubes work?
A: When power is supplied to the heater, heat is generated because of the joule's heating. This heat is transferred from the electric heater to the radiant tube by radiation. And then on, from the radiant tube to the material being heated. The material gets heated up by irradiation from the radiant tube.
Q3: What is the difference between convection and radiant tubes?
A: Radiant heat warms objects and surfaces without heating the air in between. Those objects warm up directly and radiate back. Convection warms the air, which is a triple inefficiency.
Q4: What is meant by radiant tubes?
A: The performance of a heating system depends not only on the furnace burner, but also on the radiant tubes. The aim of the radiant tubes is to transfer heat to the load through irradiation. Heat exchange occurs when the combustion fumes are generated by the burner and then are conveyed through the tube.
