Heat-Exchange Cores for Fresh-Air Systems

2025-06-26 16:21:21

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“ Heat-exchange cores recover sensible or total heat between exhaust and supply air. Learn about common materials, performance metrics, applications, maintenance and selection. ”

Operating Principle

The heat-exchange core is the key component that enables energy-saving ventilation in a fresh-air system. It transfers heat between stale indoor exhaust air and fresh outdoor supply air, reducing the energy required to condition the incoming air. There are two main types:

Sensible heat exchange

A metal core, such as aluminum foil, or a plastic core transfers heat through the temperature difference. It exchanges temperature, or sensible heat, only and does not exchange moisture.

This type is suitable where humidity control is not a priority. Its advantages are a simple structure and low cost.

Total heat exchange

A core made of a special material, such as treated paper or a polymer membrane, exchanges both temperature and moisture, or latent heat. Moisture from the indoor air is used to pre-humidify or pre-dry the incoming fresh air.

This type is suitable where both temperature and humidity must be balanced, such as homes and offices, and it offers better energy-saving performance.

Common Types and Characteristics

Type | Material | Structural Features | Advantages and Disadvantages | Applications

Sensible heat-exchange core | Aluminum foil or stainless steel | Corrugated layered structure with cross-flowing air streams | Strong corrosion resistance and long service life, but no humidity control; low airflow resistance and well suited to large temperature differences | Industrial workshops, warehouses and hot regions

Paper total-heat-exchange core | Specially treated paper | Porous honeycomb structure that increases contact area | Low cost and high moisture-transfer efficiency, but poor moisture resistance; susceptible to dampness and mold and requires regular replacement | Homes, offices and general commercial premises

Polymer-membrane total-heat-exchange core | Polyethylene or polypropylene membrane | Multilayer composite membrane that passes air but not liquid water | Moisture resistant, antibacterial, highly efficient at moisture transfer and long lasting, but more expensive and slightly higher in airflow resistance | Premium homes, hospitals and laboratories

Silicone total-heat-exchange core | Silicone-coated material | Flexible sheet structure that can be folded for installation | Resistant to aging and to high and low temperatures, making it suitable for extreme climates, but relatively expensive and bulky | Cold regions and outdoor equipment

Key Performance Parameters

Heat-exchange efficiency

This measures heat-transfer capability and is calculated as: (supply-air temperature - outdoor temperature) / (indoor temperature - outdoor temperature) × 100%. A high-performance core can reach 70%-90%.

Moisture-exchange efficiency for total-heat-exchange cores

This measures moisture-transfer capability and is calculated as: (supply-air humidity - outdoor humidity) / (indoor humidity - outdoor humidity) × 100%. A high-quality total-heat-exchange core can reach 60%-80%.

Air-leakage rate

This is the proportion of supply and exhaust air that mixes. Excessive leakage reduces heat-exchange efficiency, so the usual requirement is no more than 5%.

Air resistance

This is the pressure drop as air passes through the core. Lower resistance reduces fan energy consumption; it is generally controlled within 50-150 Pa.

Temperature and Moisture Resistance

The core's allowable temperature range, such as -20°C to 70°C, and humidity range, such as no more than 95% RH, affect its service life.

Applications

Homes and residences

When fresh air is introduced in winter, the core retains indoor heat. In summer, it reduces the loss of cooling energy. Total heat exchange also helps keep indoor humidity comfortable, reducing air-conditioning energy use.

Office buildings and commercial premises

High occupancy requires continuous ventilation. A heat-exchange core reduces the air-conditioning load and is particularly suitable for centralized fresh-air systems.

Hospitals and laboratories

These facilities require stable temperature and humidity. A total-heat-exchange core helps maintain a stable indoor environment while preventing the incoming fresh air from introducing outdoor pollutants.

Cold or hot and humid regions

Total-heat-exchange cores reduce heat loss in cold regions. Sensible heat-exchange cores are used in hot and humid regions to avoid introducing excessive moisture with the fresh air.

Maintenance and Selection Recommendations

Maintenance: paper cores should be replaced once or twice a year to prevent dust accumulation and mold. Metal cores can be cleaned regularly, but corrosive cleaners should be avoided.

Selection: choose the material and type according to climate, such as total heat exchange in northern regions and sensible heat exchange in southern regions; building requirements, such as comfort in homes and durability in industry; and the available budget.

Through efficient heat recovery, a heat-exchange core allows a fresh-air system to ventilate a building while greatly reducing energy consumption, making it an important energy-saving component in modern buildings.

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Heat-Exchange Cores for Fresh-Air Systems

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