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Application of Heat Exchangers in Ventilation Systems

Heat exchangers play a key role in ventilation systems by improving air handling efficiency, reducing energy consumption, and enhancing indoor air quality. Below is a detailed explanation of their functions and common applications.

I. Functions of Heat Exchangers in Ventilation Systems

  1. Energy Saving
    Heat exchangers recover thermal energy (or cooling energy) from exhaust air and transfer it to the incoming fresh air. This reduces the energy required to heat or cool fresh air, making it ideal for both winter heating and summer cooling.

  2. Improving Fresh Air Quality and Comfort
    While ensuring sufficient ventilation, heat exchangers help preheat or precool the fresh air, minimizing temperature differences between indoor and outdoor air, and improving occupant comfort.

  3. Boosting System Efficiency (COP)
    By recovering both sensible and latent heat from exhaust air, the system’s energy efficiency is significantly improved.

  4. Assisting Temperature and Humidity Control
    In environments such as cleanrooms, laboratories, or temperature-controlled workshops, heat exchangers serve as pre-conditioning units to stabilize incoming air conditions.

II. Common Types of Heat Exchangers in Ventilation Systems

  1. Plate Heat Exchanger (Sensible Heat)

    • Uses aluminum or plastic plates to separate exhaust and supply air streams while transferring heat across the plates.

    • Commonly used in commercial buildings, schools, and office ventilation.

    • Efficiency typically ranges from 50% to 70%.

  2. Total Heat Recovery Unit (Sensible + Latent Heat)

    • Uses a special membrane that allows both heat and moisture exchange.

    • Ideal for residential buildings, hospitals, hotels, and environments with humidity control needs.

    • Provides better comfort and energy savings.

  3. Heat Pipe Heat Exchanger

    • Features a simple structure with no moving parts; transfers heat via heat pipes while keeping airflow streams completely separate.

    • Suitable for server rooms, preheating/precooling fresh air, and drying systems.

    • Performs well in high-temperature exhaust air environments.

  4. Rotary Wheel Heat Exchanger

    • A rotating wheel with hygroscopic coating simultaneously contacts both fresh and exhaust air, transferring both heat and moisture.

    • High efficiency (up to 70%–85%), but with a potential risk of cross-contamination.

    • Suitable for scenarios where energy efficiency is prioritized and cross-contamination is not critical.

  5. Indirect Evaporative Cooling Heat Exchanger

    • Uses exhaust air evaporation to cool incoming air without adding humidity.

    • Ideal for hot, dry environments such as industrial workshops and warehouses.

III. Typical Application Scenarios

  • Industrial Facilities: Improve temperature and humidity control while lowering fresh air energy consumption.

  • Cleanrooms and Operating Rooms: Stabilize airflow and temperature for controlled environments.

  • Commercial Buildings and Offices: Precondition fresh air and improve HVAC efficiency.

  • Public Spaces (Subways, Airports, Schools): Ensure good ventilation while saving energy.

  • Data Centers and Server Rooms: Recover waste heat for air preheating during winter.

  • Livestock Houses and Greenhouses: Balance ventilation with temperature and humidity stability to support growth.

IV. Conclusion

The application of heat exchangers in ventilation systems has become an essential part of modern HVAC design. By recovering thermal energy, enhancing indoor comfort, and improving air quality, heat exchangers are a core component in green buildings, energy-saving solutions, and intelligent ventilation systems.

The role of intermediate wall heat exchangers in coal mine ventilation shaft return air waste heat utilization projects

In the coal mine ventilation shaft exhaust heat utilization project, the intermediate wall-type heat exchanger is a critical piece of equipment for safely transferring heat. Its role is not only about heat exchange efficiency but also about ensuring system safety and operational reliability. The specific functions of the intermediate wall-type heat exchanger are as follows:

To achieve the objectives of shaft freeze protection and winter heating in the auxiliary shaft area, the intermediate wall-type heat exchanger is responsible for safely isolating high-temperature return air from fresh air or clean media while enabling efficient heat exchange. Its primary functions include:

Efficient recovery and utilization of return air waste heat

Utilizing the significant sensible heat carried by return air, the heat is stably transferred to fresh air or hot water systems through the metal intermediate wall, raising the temperature of incoming fresh air into the shaft to above 2°C, meeting freeze protection requirements.

Ensuring cleanliness and safety during heat exchange

Return air contains dust, moisture, and even trace harmful gases, which cannot directly enter the fresh air system. The intermediate wall structure effectively isolates hot and cold media, preventing cross-contamination and ensuring underground air quality and operational safety.

Enhancing the operational reliability of the heating system

The heat exchanger has a robust structure and stable operation, continuing to output heat even under extreme cold conditions. This ensures the continuity and reliability of winter heating in the auxiliary shaft, reducing the operational burden and risks associated with traditional electric heating and boiler systems.

Promoting energy conservation, emissions reduction, and green mine development

Through efficient heat exchange, heating energy consumption and operational costs are significantly reduced, lowering carbon emissions. This provides technical support for coal mines to achieve clean production and green transformation.

 

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Ethylene Glycol Heat Recovery Ventilation Unit

An ethylene glycol heat recovery ventilation unit is an air handling device that uses ethylene glycol solution as a heat transfer medium to recover heat or cooling energy from exhaust air, improving the energy efficiency of air conditioning systems. It is widely used in places requiring strict separation of fresh and exhaust air, such as hospitals, laboratories, and industrial facilities.

Working Principle

The ethylene glycol heat recovery ventilation unit achieves energy recovery through a heat exchanger and ethylene glycol solution:

  1. Exhaust Side: The cooling or heating energy in the exhaust air is transferred to the ethylene glycol solution via a heat exchanger, altering the solution's temperature.
  2. Fresh Air Side: A circulation pump delivers the cooled or heated ethylene glycol solution to the fresh air side's heat exchanger, adjusting the fresh air temperature to reduce the operating load and energy consumption of the air conditioning system.
  3. Heat Recovery Efficiency: The heat recovery efficiency of the ethylene glycol solution can reach about 50%, depending on system design and operating conditions.

System Components

  • Fresh Air Side: Fresh air section, primary/medium efficiency filter section, ethylene glycol heat exchanger, and supply fan section.
  • Exhaust Side: Return air section, primary efficiency filter section, ethylene glycol heat exchanger, and exhaust fan section.

Applications

  • Suitable for scenarios requiring complete isolation of fresh and exhaust air, such as hospitals and cleanrooms.
  • Ideal for industrial or commercial buildings needing efficient energy recovery, such as factories and transportation facilities.

Advantages

  • High Energy Efficiency: Reduces air conditioning system energy consumption through heat recovery, lowering operating costs.
  • Flexibility: Adjusts fresh air temperature based on varying climate conditions, adapting to diverse environments.
  • Safety: Ethylene glycol solution prevents heat exchanger freezing in low-temperature environments.

Considerations

  • Maintenance: Regular checks on the ethylene glycol solution concentration and circulation pump operation are necessary.
  • Design Requirements: System design must consider the layout of fresh and exhaust air ducts to ensure efficient heat exchange and prevent cross-contamination.

Heat Recovery Fresh Air Unit

The heat recovery fresh air unit is an energy-efficient ventilation system that introduces fresh outdoor air while recovering heat from the exhaust air. It uses a heat exchanger—typically a plate-type or rotary wheel exchanger—to transfer thermal energy between incoming and outgoing airstreams without mixing them, significantly reducing heating or cooling loads.

Constructed with high-efficiency filters, fans, and a heat exchanger core (commonly aluminum or enthalpy material), the system ensures a continuous supply of fresh air while maintaining indoor temperature stability and improving air quality. It helps reduce energy consumption, enhance indoor comfort, and comply with modern building energy-saving standards.

These units are ideal for applications in offices, factories, schools, hospitals, and other facilities requiring reliable ventilation and temperature control with reduced operating costs.

how does air to air heat exchanger work in fresh air system

An air-to-air heat exchanger in a fresh air system transfers heat between incoming fresh air and outgoing stale air without mixing the two streams. Here’s how it works:

  1. Structure: The exchanger consists of a core with thin, alternating channels or plates, often made of metal or plastic, that separate the incoming and outgoing airflows. These channels allow heat transfer while keeping air streams isolated.
  2. Heat Transfer:
    • In winter, warm indoor air (being exhausted) transfers its heat to the colder incoming fresh air, pre-warming it.
    • In summer, cooler indoor air transfers its "coolness" to the warmer incoming air, pre-cooling it.
    • This process occurs through conduction across the exchanger’s walls, driven by the temperature difference.
  3. Types:
    • Cross-flow: Air streams flow perpendicularly, offering moderate efficiency (50-70%).
    • Counter-flow: Air streams flow in opposite directions, maximizing heat transfer (up to 90% efficiency).
    • Rotary (enthalpy wheel): A rotating wheel absorbs and transfers both heat and moisture, ideal for humidity control.
  4. Benefits:
    • Reduces energy loss by recovering 50-90% of the heat from exhaust air.
    • Maintains indoor air quality by supplying fresh air while minimizing heating/cooling costs.
  5. Operation in Fresh Air System:
    • A fan draws stale air from the building through the exchanger while another fan pulls fresh outdoor air in.
    • The exchanger ensures the incoming air is tempered (closer to indoor temperature) before distribution, reducing the load on HVAC systems.
  6. Moisture Control (in some models):
    • Enthalpy exchangers also transfer moisture, preventing overly dry or humid indoor conditions.

The system ensures ventilation efficiency, energy savings, and comfort by recycling heat while maintaining air quality.

heat pump fresh air ventilator system in china

A heat pump fresh air ventilator system combines ventilation and energy recovery, using a heat pump to manage the temperature of incoming fresh air while simultaneously removing stale air from a space. This type of system is especially energy-efficient, as it not only improves indoor air quality but also recycles the thermal energy from the exhaust air.

Here’s how it typically works:

  1. Fresh Air Intake: The system draws in fresh air from the outside.

  2. Heat Pump Operation: The heat pump extracts heat from the exhaust air (or vice versa depending on the season) and transfers it to the incoming fresh air. In the winter, it can warm up the cold outside air; in the summer, it can cool the incoming air.

  3. Ventilation: As the system works, it also ventilates the space by removing stale, polluted air, maintaining a constant flow of fresh air without wasting energy.

The benefits include:

  • Energy Efficiency: The heat pump reduces the need for additional heating or cooling, saving on energy costs.

  • Improved Air Quality: Constantly introducing fresh air helps remove indoor pollutants, ensuring better air quality.

  • Temperature Control: It can help maintain comfortable indoor temperatures year-round, whether heating or cooling is needed.

These systems are commonly used in energy-efficient buildings, homes, and commercial spaces where both air quality and energy savings are priorities.

The utilization of air-to-air heat exchangers in ventilation and energy-saving engineering

The core function of an air-to-air heat exchanger is to transfer the residual heat carried in the exhaust air (indoor exhaust air) to the fresh air (outdoor intake air) through heat exchange, without directly mixing the two airflows. The entire process is based on the principles of heat conduction and energy conservation, as follows:

Exhaust waste heat capture:
The air expelled indoors (exhaust) usually contains a high amount of heat (warm air in winter and cold air in summer), which would otherwise dissipate directly to the outside.
The exhaust air flows through one side of the heat exchanger, transferring heat to the heat conducting material of the heat exchanger.
Heat transfer:
Air to air heat exchangers are usually composed of metal plates, tube bundles, or heat pipes, which have good thermal conductivity.
Fresh air (air introduced from outside) flows through the other side of the heat exchanger, indirectly contacting the heat on the exhaust side, and absorbing heat through the wall of the heat exchanger.
In winter, fresh air is preheated; In summer, the fresh air is pre cooled (if the exhaust air is air conditioning cold air).
Energy recovery and conservation:
By preheating or pre cooling fresh air, the energy consumption of subsequent heating or cooling equipment is reduced. For example, in winter, the outdoor temperature may be 0 ° C, with an exhaust temperature of 20 ° C. After passing through a heat exchanger, the fresh air temperature may rise to 15 ° C. This way, the heating system only needs to heat the fresh air from 15 ° C to the target temperature, rather than starting from 0 ° C.
Airflow isolation:
Exhaust and fresh air flow through different channels in the heat exchanger to avoid cross contamination and ensure indoor air quality.
technological process
Exhaust collection: indoor exhaust gas is guided to the air-to-air heat exchanger through a ventilation system (such as an exhaust fan).
Fresh air introduction: Outdoor fresh air enters the other side of the heat exchanger through the fresh air duct.
Heat exchange: Inside the heat exchanger, exhaust and fresh air exchange heat in isolated channels.
Fresh air treatment: Preheated (or pre cooled) fresh air enters the air conditioning system or is directly sent into the room, and the temperature or humidity is further adjusted as needed.
Exhaust emission: After completing heat exchange, the exhaust temperature decreases and is finally discharged outdoors.
Types of air-to-air heat exchangers
Plate heat exchanger: composed of multiple layers of thin plates, with exhaust and fresh air flowing in opposite or intersecting directions in adjacent channels, resulting in high efficiency.
Wheel heat exchanger: using rotating heat wheels to absorb exhaust heat and transfer it to fresh air, suitable for high air volume systems.
Heat pipe heat exchanger: It utilizes the evaporation and condensation of the working fluid inside the heat pipe to transfer heat, and is suitable for scenarios with large temperature differences.
advantage
Energy saving: Recovering 70% -90% of exhaust waste heat, significantly reducing heating or cooling energy consumption.
Environmental Protection: Reduce energy consumption and lower carbon emissions.
Enhance comfort: Avoid direct introduction of cold or hot fresh air and improve indoor environment.

Mine exhaust heat extraction box with built-in air-to-air heat exchanger

The built-in air-to-air heat exchanger in the mine exhaust heat extraction box is a device specifically designed to recover waste heat from mine exhaust air. Mine exhaust refers to the low-temperature, high humidity waste gas discharged from a mine, which usually contains a certain amount of heat but is traditionally discharged directly without being utilized. This device uses a built-in air-to-air heat exchanger (i.e. air-to-air heat exchanger) to transfer heat from the exhaust air to another stream of cold air, thereby achieving the goal of waste heat recovery.

Working principle
Lack of air input: The mine's lack of air is introduced into the heat extraction box through the ventilation system. The temperature of the exhaust air is generally around 20 ℃ (the specific temperature varies depending on the depth of the mine and the environment), and the humidity is relatively high.
Function of Air to Air Heat Exchanger: The built-in air to air heat exchanger usually adopts a plate or tube structure, and the exhaust air and cold air exchange heat through a partition type in the heat exchanger. The heat from the lack of wind is transferred to the cold air, while the two airflows do not mix directly.
Heat output: After being heated by heat exchange, the cold air can be used for anti freezing of mine air inlet, heating of mining area buildings, or domestic hot water, while the exhaust air is discharged at a lower temperature after releasing heat.
Characteristics and advantages
Efficient and energy-saving: Air to air heat exchangers do not require additional working fluids and directly utilize the heat transfer from air to air. They have a simple structure and low operating costs.
Environmental friendliness: By recycling exhaust heat and reducing energy waste, it meets the requirements of green and low-carbon development.
Strong adaptability: The equipment can be customized and designed according to the flow rate and temperature of the mine exhaust, suitable for mines of different scales.
Easy maintenance: Compared to heat pipe or heat pump systems, air-to-air heat exchangers have a relatively simple structure and require less maintenance.
Application scenarios
Anti freezing at the wellhead: Use the recovered heat to heat the mine air intake and avoid freezing in winter.
Building heating: providing heating for office buildings, dormitories, etc. in the mining area.
Hot water supply: Combined with the subsequent system, provide a heat source for domestic hot water in the mining area.
precautions
Moisture treatment: Due to the high humidity of the exhaust air, the heat exchanger may face the problem of condensation water accumulation, and a drainage system or anti-corrosion materials need to be designed.
Heat transfer efficiency: The efficiency of an air-to-air heat exchanger is limited by the specific heat capacity and temperature difference of the air, and the recovered heat may not be as high as that of a heat pump system, but its advantage lies in its simple structure.

Application of Air-to-Air Heat Recovery Exchanger in Livestock Ventilation

The Air-to-Air Heat Recovery Exchanger plays a vital role in the livestock ventilation industry by enhancing energy efficiency and maintaining optimal indoor conditions. Designed to recover waste heat from exhaust air, this exchanger transfers thermal energy from the warm, stale air expelled from livestock facilities to the incoming fresh, cooler air without mixing the two streams. In poultry houses, pig barns, and other breeding environments, where consistent temperature control and air quality are critical, it reduces heating costs in winter by pre-warming fresh air and mitigates heat stress in summer through effective thermal regulation. Typically constructed with corrosion-resistant materials like aluminum or stainless steel, it withstands the humid and ammonia-rich conditions common in livestock settings. By integrating into ventilation systems, the exchanger not only lowers energy consumption but also supports sustainable farming practices, ensuring animal welfare and operational efficiency. Its application is particularly valuable in large-scale breeding operations aiming to balance cost-effectiveness with environmental responsibility.

Air-to-Air Heat Recovery Exchanger

Fully automatic non partition air filter production line

Fully automatic non partition air filter production line

The fully automatic non partition air filter production line is a highly automated production system, typically used to produce high-performance air filters, widely used in industrial, commercial, and household air purification equipment. Its core feature is the use of a non partition design to improve the filtration efficiency of the air filter and reduce the resistance of air flow.

Main features:
Partition free design: Traditional air filters typically use partitions to separate the filter material layer, while partition free design can effectively reduce obstacles to air flow, thereby improving filtration efficiency and reducing energy consumption.
Fully automated operation: From raw material cutting, filter material assembly, to finished product packaging, the production line achieves full automation, reduces manual intervention, and improves production efficiency and consistency.
High precision control system: By integrating advanced automation control systems and sensors, it ensures precise control of the production process and achieves high-quality filter products.
Fast switching and flexibility: The production line supports the production of filters of different specifications and types, and can quickly switch production modes to meet the needs of different customers.
Efficient production capacity: Design efficient processes and modular systems that can meet large-scale production requirements and ensure stable product quality.

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