Drying is one of the most energy-intensive processes in industries such as food processing, agriculture, textiles, paper, wood, lithium battery manufacturing, and chemical production. During operation, large volumes of hot exhaust air are discharged from dryers, carrying valuable thermal energy. Recovering this waste heat is an effective way to reduce fuel consumption, lower operating costs, and improve overall energy efficiency.
A waste heat recovery system typically uses an air-to-air plate heat exchanger to transfer heat from the hot exhaust air to the incoming fresh air without mixing the two air streams. The preheated air then enters the drying system, reducing the load on gas burners, electric heaters, steam systems, or heat pumps. Depending on the application, different heat exchanger materials such as aluminum foil, hydrophilic aluminum foil, epoxy-coated aluminum, or stainless steel can be selected to suit various temperatures and corrosive environments.
Drying waste heat recovery is widely used in tea, fruits, vegetables, seafood, herbs, mushrooms, nuts, textile stenters, printing and coating lines, lithium battery coating machines, sludge dryers, and wood drying kilns. In many continuous drying processes, the system can significantly reduce energy consumption while improving temperature stability and production efficiency.
As energy prices continue to rise, waste heat recovery has become an essential upgrade for modern drying equipment. A well-designed heat recovery system not only reduces operating costs and carbon emissions but also extends equipment life and supports sustainable, energy-efficient manufacturing.
Related: Industrial Drying Heat Recovery
Before You Start
A successful Drying Waste Heat Recovery: A Smart Solution for Energy Savings project begins with measurement. Record the supply and exhaust airflow rates, the temperatures on each side, and the hours the system runs per year. Note any contaminants in the exhaust and the available space for the core and ductwork. These figures decide both the type of exchanger and whether the payback makes sense.
Step-by-Step
First, choose the exchanger type from the air cleanliness and recovery target. Second, size the core using the measured airflow and the log-mean temperature difference, leaving margin for fouling. Third, lay out the duct path so the exhaust is filtered before the core and the supply side has drainage if it may condense. Fourth, add a bypass for free cooling and wire the fans to a simple control. Finally, commission the unit and record baseline temperatures.
Verification
After startup, compare the pre- and post-installation supply temperatures at the same outdoor condition. A steady recovery of 50 percent or more confirms correct sizing. Re-check each season and clean the exhaust side when the recovered temperature begins to fall, because fouling quietly erodes performance over time.
Frequently Asked Questions
Do I need a bypass? In most climates yes, so the system can free-cool when outdoor air is mild. How is sizing done? From measured airflow and the log-mean temperature difference, not from estimates.