What is A Radiant Heater?
A radiant heater is a device that generates heat through radiation, typically infrared radiation. It consists of a heating element that emits radiant energy when supplied with electricity or fuel. The key components are:
- Heating element: Often made of tungsten filaments, carbon fibers, or quartz tubes filled with gas.
- Reflector: Focuses and directs the radiant heat towards the desired area.
- Housing: Encloses the heating element and reflector, with a transparent or open front to allow radiant heat to pass through.
How Does A Radiant Heater Work
Operating Principle
Radiant heaters convert electrical or combustion energy into radiant heat, which is electromagnetic radiation in the infrared spectrum. The key components are:
- A heating element or burner that generates high temperatures (up to 1800°C )
- A reflector or cavity to direct the radiant heat in the desired direction
Heat Transfer Mechanism
Unlike convection heaters, radiant heaters do not rely on heating the air. Instead, they emit infrared radiation that directly heats objects and surfaces that absorb this radiation. This allows for more efficient and targeted heating without heating the surrounding air unnecessarily.
Radiant Heater vs. Infrared Heater: What’s The Difference?
Radiant heaters and infrared heaters are often used interchangeably, but they have distinct differences in their operating principles and applications.
Heating Mechanism
- Radiant heaters emit electromagnetic radiation in the infrared spectrum, which directly heats objects and surfaces in their path without significantly warming the surrounding air. This process is known as radiant heat transfer.
- Infrared heaters, on the other hand, rely on the principle of convection heating. They heat the surrounding air, which then transfers heat to objects and surfaces through air circulation.
Energy Efficiency
- Radiant heaters are generally more energy-efficient as they directly heat the desired objects or surfaces without wasting energy on heating the entire air volume. This makes them suitable for targeted heating applications.
- Infrared heaters may be less efficient as they heat the air, which can lead to heat losses through ventilation or drafts.
Heating Speed and Distribution
- Radiant heaters provide rapid and direct heating of surfaces and objects, resulting in a faster heating response.
- Infrared heaters take longer to heat the surrounding air, leading to a slower heating response and less uniform heat distribution.
Applications
- Radiant heaters are widely used in industrial settings for processes like drying, curing, and material processing. They are also used for outdoor heating applications like patio heaters.
- Infrared heaters are commonly used for space heating in residential and commercial buildings, as well as in some industrial processes.
Environmental Impact
- Radiant heaters can be powered by various energy sources, including electricity, natural gas, or hydrogen, allowing for the potential use of renewable energy sources.
- Infrared heaters powered by fossil fuels may have a higher environmental impact due to emissions.
Benefits of Using A Radiant Heater
Radiant heaters convert energy into electromagnetic radiation, typically infrared, to provide warmth. They offer several advantages over conventional heating systems:
- Higher efficiency: Radiant heaters directly heat objects and surfaces, minimizing energy losses through air heating and convection.
- Targeted heating: Radiant heat can be directed to specific areas, allowing for localized heating and energy savings.
- Improved comfort: Radiant heating mimics the natural warmth of the sun, providing a more comfortable and evenly distributed heat.
Applications of Radiant Heaters
Heating Applications
- Room and Outdoor Area Heating: Radiant heaters are widely used for temperature control and heating of rooms and outdoor facilities. They provide instant warmth and high radiation intensity without irritation to the skin compared to quartz lamp heaters.
- Vehicle Interior Heating: Radiant heaters are mounted in vehicle interiors, such as under the dashboard, steering column, or front seat backrests, to directly heat passengers, especially their legs, providing quick heating.
- Brooding in Poultry Houses: Radiant heaters are the preferred method for providing supplemental heat in poultry houses, creating a suitable microclimate for chicks by allowing a range of thermal comfort options.
Radiant Heating Systems
- Radiant Floor Heating: Thermally sprayed resistive heating layers can be bonded directly onto sub-floors, overlays, or concrete substrates, with a finished floor surface installed over the heater.
- Ceiling and Wall Heating: Radiant heating panels or profiles can be installed on ceilings or walls, using water or electrical heating elements to emit infrared radiation.
- Combination Systems: Radiant heating can be combined with small air systems to improve indoor air quality and thermal comfort by introducing ventilation air and removing latent loads.
Application Cases
| Product/Project | Technical Outcomes | Application Scenarios |
|---|---|---|
| Infrared Radiant Heaters for Room Heating | Provide instant warmth and high radiation intensity without skin irritation compared to quartz lamp heaters. | Heating rooms and outdoor facilities for temperature control. |
| Radiant Heaters for Vehicle Interiors | Mounted under dashboards, steering columns, or front seat backrests to directly heat passengers, especially their legs, providing quick heating. | Heating vehicle interiors for passenger comfort. |
| Radiant Brooder Heaters for Poultry Houses | Create a suitable microclimate for chicks by allowing a range of thermal comfort options, preferred over other heating methods. | Providing supplemental heat in poultry houses for brooding chicks. |
| Radiant Floor Heating Systems | Thermally sprayed resistive heating layers bonded directly onto sub-floors, overlays, or concrete substrates, with a finished floor surface installed over the heater. | Heating floors in residential and commercial buildings for efficient and comfortable heating. |
| Infrared Radiant Heaters for Industrial Processes | Provide precise and controllable heating for various industrial processes, such as drying, curing, and heat treatment of materials. | Industrial applications requiring controlled and targeted heating, such as in manufacturing and processing facilities. |
Latest Technical Innovations of Radiant Heater
Semiconductor-based Radiant Heaters
A key innovation is the use of semiconductor components like LEDs as the heating source in radiant heaters. These emit infrared radiation in the wavelength range >0.7 μm for heating purposes. The advantages include:
- Higher efficiency compared to traditional radiant heaters by reducing convection and conduction losses.
- Targeted heating of specific areas while minimizing energy input in other zones.
- Lower operating temperatures (around 100°C) reduce fire hazards.
The semiconductor components are partially surrounded by heat sinks to dissipate excess heat. Thermal insulation is used on the non-radiating side to improve efficiency.
High-temperature Rapid Response Heaters
Researchers have developed radiant heaters using incandescent tungsten filaments enclosed in evacuated ceramic envelopes. Key features:
- Rapid heating/cooling rates up to 400 K/min and temperatures exceeding 1800 K.
- High surface and volumetric power densities are comparable to infrared gold image furnaces.
- Low cost of ~$0.05/W, less than 0.03% of infrared gold furnaces (>$2/W).
The modular design with chemically inert ceramic envelopes enables robust performance over 10,000 demanding thermal cycles.
Combustion-based Radiant Heaters
Innovations in combustion-based radiant heaters include:
- Radiant heating screens with an upper screen of larger diameter enclosing the combustion area. This improves heating efficiency and stability.
- Use of solid combustible materials like charcoal instead of gas, making them portable and eco-friendly.
- Annular cylindrical radiant burners with a conical reflector to refocus the omnidirectional radiant flux. This achieves 70-75% radiation efficiency.
Novel Heating Element Designs
Advances have been made in the heating element design for improved radiant heat transfer:
- Coiled heating elements are partially embedded in a concave cavity surface in a helical pattern. A lens focuses the radiant heat output.
- Tubular assembled heating elements with grooved/micro-protuberance surfaces to enhance heat transfer.
- Incorporation of thermal inertia heating elements that store heat for gradual release, improving temperature regulation.
Energy-efficient Controls and Applications
Other innovations aim to improve energy efficiency and broaden applications:
- Use of radiant heating panels made from recycled stone waste, containing integrated heating elements.
- Thin-film radiant heaters with low heat capacity for rapid transient heating in EVs to extend range.
- Hybrid systems combining radiant and convective heating for better indoor climate control.
- Optimized control strategies for radiant heating accounting for thermal comfort and air quality.
Technical Challenges
| Semiconductor-based Radiant Heaters | Integrating semiconductor components like LEDs as the heating source in radiant heaters to emit infrared radiation for heating purposes, offering higher efficiency, targeted heating, lower operating temperatures, and reduced fire hazards compared to traditional radiant heaters. |
| High-temperature Rapid Response Radiant Heaters | Developing radiant heaters using incandescent tungsten filaments enclosed in evacuated ceramic envelopes, enabling rapid heating/cooling rates up to 400 K/min, high surface and volumetric power densities, and low cost compared to infrared gold image furnaces. |
| Radiant Heater Efficiency Improvements | Improving the efficiency of radiant heaters by using radiants (separate from the walls) made of ceramic or alloy with a continuous surface, high melting point, and creep/deformation properties similar to the furnace tubes, to enhance heat transfer and reduce emissions. |
| Integrated Ballast in Radiant Heaters | Integrating the necessary ballast into radiant heaters with semiconductor components, allowing the heat loss from the ballast to be utilised as thermal radiation at the heating location and minimising the convective portion of the total heat emission. |
| Radiant Heaters for Laser Sintering | Developing radiant heaters with flat heat-emission elements made of materials with low thermal inertia, high thermal diffusivity, and thickness less than or equal to 2 mm, for heating the building material in laser sintering devices used in manufacturing three-dimensional objects. |
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