Convection and Radiation Heat Recovery Systems

How does a convection and radiation heat recovery unit work?

A heat recovery unit using both convection and radiation is a device designed to maximize the efficiency of heat transfer between two streams of air or gases at different temperatures without mixing. They allow the reheating of combustion air by gases at very high temperatures (up to 1500ºC).

The heat transfer process can occur in two ways:

Convection (500 to 1000ºC): Heat is transferred through smooth steel tubes by convection from the hot gases to the surfaces of the recuperator. This process involves the transfer of thermal energy from part of the gas to the cold air.
Thermal radiation (900 to 1500ºC): When hot gases, such as flue gases, flow through the recuperator, they emit energy in the form of electromagnetic waves due to their high temperature. This radiant energy is absorbed by the surfaces of the recuperator, heating them.

The surfaces heated by these two mechanisms transfer the heat to the cold air circulating on the opposite side of the recuperator, raising its temperature for later use.

Installation of the radiant section of a heat recovery unit

How is a heat recovery unit designed?

Depending on the needs of the process and the available space, we design the equipment adapted to the customer’s needs. All types of heat exchangers are manufactured under ASME or EN standards.

The main factors to take into account when designing an exchanger are the following:

Geometry of the equipment: Once the case and the balance of the process have been studied, the configuration and dimensions of the tubes are analyzed, since these factors have a direct impact on the efficiency of the heat exchange process, it is adapted to the customer’s needs, considering possible space limits. In the design we look for:
- Allow uniform flow and minimize scale buildup, which could adversely affect heat transfer.
- Design according to an adequate fluid flow velocity and direction, seeking to avoid dead zones or excessive turbulence that may decrease the efficiency of the recuperator.
Materials: Proper selection is essential to ensure chemical compatibility and corrosion resistance. In addition, materials must have thermal properties that promote heat transfer and withstand temperatures.

In addition, these exchangers can be designed according to two types:

Cross flow recuperators: In these exchangers the air and gas flows cross perpendicularly.
Counterflow recuperators: In this type of exchanger, gas and air flows cross in parallel, which maximizes heat transfer.

Not sure which one you need? Our team of experts can analyze your process and recommend the best solution.

At AITESA we are experts in heat recovery design.

Seccion convectiva de un recuperador de calor

Convective section of a heat recovery unit

Key factors in choosing the right flow recuperator

Sizing and capacity

Heat exchanged
Space limitations
Adaptability to existing installations

Process conditions

Flow rate of both fluids
Temperature of both fluids

Physical properties:

Viscosity: Affects the fluid flow resistance.
Density: Affects heat capacity.
Thermal conductivity: Affects heat transfer efficiency.

Ease of maintenance and durability:

Maintenance: Easy-to-maintain equipment extends the useful life of the equipment
Durability: The right choice of materials also prolongs the life of the equipment.

Compliance with international regulations

Mechanical calculation following different standards:
- ASME VIII Div.1
- EN-13445

Compliance with customer specifications

Design and supply of equipment adapted to the specific requirements of each customer and each project.

At AITESA we are experts in the design of convection and radiation heat recovery systems.

Key benefits for your industry

Adaptation to industry capacity needs

Due to the types of recuperators that exist and the flexibility they present, their design can be adapted to the production needs and capacities of the industry.

Ruggedness

Their mechanically solid construction provides them with high resistance to extreme operating conditions such as high temperatures and corrosive media. This makes them especially suitable for demanding industrial environments.

Simplicity of operation

The operating principle of the heat recovery units is simple and reliable. This reduces the need for complex control systems, minimizes the possibility of operational failures and facilitates integration into existing plants without the need for major modifications.

Ease of maintenance

They allow periodic inspections, cleaning and repairs to be carried out easily, minimizing downtime as much as possible, which favors continuous and cost-effective operation.

Long service life

If properly maintained and materials are correctly selected according to the type of fluid and operating conditions, this equipment can operate efficiently for a very long period of time.

Reduced operating costs

Thanks to their thermal efficiency, low maintenance and long service life, heat recovery units help to reduce energy consumption and operating costs in the long term. In addition, their design flexibility allows them to avoid unnecessary oversizing and to adapt to future expansions or process changes.

Energy savings

By harnessing waste heat, the need for additional power generation is reduced, which reduces greenhouse gas emissions and contributes to a more sustainable operation, translating directly into lower operating costs.

Montaje de la seccion radiante de un recuperador de calor

Installation of the radiant section of a heat recovery unit

Industrial sectors in which radiation and convection heat recovery units are used

Glass industries

Glass melting furnaces generate waste heat at high temperatures. This heat can be recovered to preheat raw materials or generate steam, improving the energy efficiency of the process.

Ceramic industry

During the firing of ceramic products, a significant amount of heat is released. The recovery of this heat allows it to be reused in other stages of the process, such as the drying of parts, optimizing energy consumption.

Metallurgical industry

Smelting and heat treatment processes generate waste heat that can be recovered to preheat combustion air, improving process efficiency.

Chemical industry

Chemical reactions and distillation processes release heat that can be reused in other process steps, optimizing overall energy consumption.

Paper industry

Paper production involves drying processes that generate waste heat. This heat can be recovered and reused in the same process or in other processes, such as steam generation.

Why choose an AITESA heat recovery unit?

More than 5000 projects in strategic sectors

40 years of experience designing heat recovery units
Adaptation to demanding environments such as refineries, petrochemical and industrial plants, where every degree of efficiency optimizes profitability.

Maximum efficiency and minimum emissions

Proven and optimized designs: our experience allows us to guarantee robust and safe solutions for every industry.
Reduced environmental impact with minimum heat loss and maximum thermal efficiency.
Reduction of operating costs through heat recovery systems and precise selection of materials.
Adaptation to demanding environments such as combined cycle, refineries and industrial plants, where every degree of efficiency optimizes profitability.

Comprehensive technical support and maintenance

Maximum availability thanks to preventive and corrective maintenance plans and field inspection services.
Fast response, guaranteed spare parts and continuous support to minimize unscheduled downtime.
Technical assistance for incidents, redesigns or adaptations to new processes.

At AITESA we not only manufacture heat exchangers, we develop efficient thermal solutions that boost your production, optimize costs and guarantee regulatory and environmental compliance.

Transporte de los tubos de la seccion radiante de un recuperador

Transport of the tubes of the radiant section of a recuperator

Frequently Asked Questions

What information do I need to provide to get a quotation for an exchanger suitable for my process?

You must indicate the gas with which you wish to heat, inlet temperatures, heat exchanged, flow rates, operating pressure, type of installation, space limitations, and possible material restrictions due to corrosion or regulations.

How is the number of steps determined?

The number of steps refers to the number of times the fluid changes direction inside the recuperator.

To determine it, it is adjusted according to the customer’s needs: Pressure drop, speed and space.

How is the recuperator maintained?

Maintenance includes:

Cleaning: To remove incrustations or deposits in the tubes.
Inspection: To check for leaks, corrosion or wear.
Seals and gaskets: Over time they may degrade and lose effectiveness.

How long does it take to amortize the investment in a heat recovery unit?

The payback period depends on factors such as initial cost, energy savings, and operation and maintenance costs. In many cases, the investment can be recovered within 1 to 3 years, although this period may vary depending on the specific conditions of each installation.

How do I know if my process would benefit from a heat recovery unit?

At AITESA we evaluate each case independently, making an exhaustive study in order to recommend the best possible type of heat exchanger for the process.

What advantages does it have over other types of exchangers?

Ease of maintenance, versatile design, compatibility with dirty or corrosive fluids, high thermal capacity and fast return on investment.

Success stories

Design and supply of a convection recuperator in a steel plant

AdminAitesa | Case Study - Steel | No Comments

AITESA was responsible for the design, supply and assembly supervision of a convection recuperator for a walking beam furnace at a steel plant in Gijón (Spain). Heat recuperators allow the…

EPC of a radiant recuperator for a steel plant

AdminAitesa | Case Study - Steel | No Comments

In 2017, the project for the design and supply of a radiation recuperator for a major steel company manufacturing steel using blast furnaces in France began. The aim of the…