Views: 0 Author: Site Editor Publish Time: 2026-02-04 Origin: Site
Air-to-air flue gas exhaust heat recovery systems are widely applied in industrial facilities to reclaim low- to medium-grade waste heat from exhaust air streams and reuse it for preheating fresh intake air. This approach significantly reduces fuel consumption, lowers operating costs, and cuts carbon emissions.
In applications involving corrosive or contaminated exhaust gases, stainless steel (SS) heat exchangers are the preferred solution due to their durability, corrosion resistance, and long service life.
This project focuses on an air-to-air flue gas heat recovery heat exchanger constructed from stainless steel, designed for continuous industrial operation with high airflow and moderate exhaust temperatures.
Key operating conditions:
Exhaust (hot air) flow rate: 24,500 m³/h
Exhaust air inlet temperature: 90 °C
Fresh air inlet temperature: 39 °C
Target fresh air outlet temperature: 75 °C
The system recovers thermal energy from the 90 °C flue gas exhaust and transfers it to the incoming fresh air stream, raising its temperature by approximately 36 °C without any direct air mixing.
The air-to-air heat exchanger operates on an indirect heat transfer principle:
Hot exhaust air flows through one side of the stainless steel heat exchanger.
Fresh intake air passes through a separate channel on the opposite side.
Heat is transferred across the SS heat transfer surfaces via conduction and convection.
The exhaust air is cooled before discharge, while the fresh air is preheated to the required 75 °C.
This closed-loop heat exchange ensures:
No cross-contamination between flue gas and fresh air
Stable thermal performance
Safe operation even with slightly contaminated exhaust streams
Using stainless steel in flue gas exhaust heat recovery applications provides several technical advantages:
Excellent corrosion resistance against acidic condensates and contaminants
High temperature tolerance, suitable for continuous operation at 90 °C and above
Smooth surface finish, reducing fouling and simplifying maintenance
Long service life, even in harsh industrial environments
Common grades such as SS304 or SS316 are typically selected based on exhaust gas composition and corrosion risk.
By increasing the fresh air temperature from 39 °C to 75 °C, the recovered heat can be directly reused for:
Combustion air preheating
Process air supply
Space heating in industrial workshops
Make-up air units (MAU) and AHU systems
This reduces the demand on downstream heaters (gas, steam, or electric), delivering:
Lower fuel consumption
Faster system payback
Reduced CO₂ emissions
Boiler and furnace exhaust heat recovery
Drying ovens and curing lines
Textile, food, and chemical process ventilation
Waste air systems with medium-temperature flue gas
Industrial AHU fresh air preheating
To match specific site requirements, the air-to-air SS heat exchanger can be customized with:
Counterflow or crossflow configuration
Modular or skid-mounted design
Insulated casing to minimize heat loss
Easy-access panels for inspection and cleaning
Flange connections compatible with existing ductwork
An air-to-air flue gas exhaust heat recovery heat exchanger made of stainless steel is a highly efficient and reliable solution for reclaiming waste heat from 90 °C exhaust air. With an airflow of 24,500 m³/h, the system successfully increases fresh air temperature from 39 °C to 75 °C, delivering substantial energy savings, improved system efficiency, and long-term operational reliability.
