Air-to-Air vs. Wrap-Around Heat Pipe Exchangers: Key Differences for HVAC Systems
In heating, ventilation, and air conditioning (HVAC) systems, heat exchangers play a vital role in transferring heat energy efficiently. They are integral components that facilitate the exchange of heat between two mediums without mingling them together, maximizing energy use and minimizing waste.
In this blog post, we’ll explore the differences between the two primary types of heat pipe heat exchangers: Air-to-Air Heat Pipe Exchangers vs Wrap-Around Heat Pipe Exchangers.
What are Air-to-Air heat Pipe Heat Exchangers (AAHX)
Air-to-Air heat pipe heat exchangers, also known as air-to-air heat recovery ventilators (HRVs) or energy recovery ventilators (ERVs), are designed to transfer heat between two air streams. They operate on a simple yet effective principle: as warm air flows through the exchanger, it gives up its heat to the cooler air flowing in the opposite direction. This process allows for efficient heat recovery, significantly reducing the energy required to heat or cool incoming air. These systems are commonly used in commercial and industrial buildings such as semiconductor plants to ensure efficient ventilation while conserving energy.
How Do AAHX’s Work?
Air-to-Air heat pipe heat exchangers consist of a heat exchanger core that separates the incoming and outgoing air streams. This cores are typically made with copper tubes wrapped with aluminum fins. In some applications the fins can be made of copper. As the fresh outdoor air and stale indoor air pass through the heat exchanger, heat energy is transferred from the warmer air to the cooler air without the two streams mixing. Other technologies like energy recovery wheels can mix up to 15% of exhaust smells or contaminates into the incoming air stream.
ACT-AAHX systems are 100% intake to exhaust air isolated. This process helps to preheat or precool incoming air, depending on the season, thereby reducing the workload on heating and cooling systems.
Need help deciding if a air-to-air heat pipe exchanger will work for you? Try our AAHX selection tool below with your exact specifications.
What Are Wrap-Around heat Pipe Heat Exchangers (WAHX)
Wrap-around heat pipe heat exchangers, also known as run-around loop heat exchangers, are innovative systems designed to boost a dedicated 100% Chilled water DOAS air handler enhance its latent capabilities by precooling incoming air, which equates to tonnage saving for the chilled water plant and provides more pounds of water removal. On the opposite side of the chilled water, the WAHX reheat coil provides passive reheat in the mega BTU’s range. The reheating also provides comfortable dry neutral air to be supplied to the building.
How do WAHX’s WOrk?
Wrap-around heat exchangers use a common low global warming potential R-134a refrigerant to transfer heat between precool coil and the reheat coil. The WAHX system consists of these two coils connected by piping wrapped around the cooling coil. The wrap-around design allows for flexible installation, since the coils don’t need to be adjacent. This makes it ideal for retrofits, new AHU installs at the OEM factory or at ACT.
Need assistance with designing a wrap-around heat pipe exchanger? Our WAHX selection tool is built for HVAC design engineers in the proper selection of a WAHX.
Air-to-Air Heat Pipe Exchangers vs Wrap-Around Heat Pipe Exchangers
AAHX Systems
WAHX Systems
- Energy Efficiency: By recovering heat from exhaust air, air-to-air heat exchangers can significantly reduce heating and cooling loads, leading to energy savings.
- Improved Indoor Air Quality: These systems help maintain a constant supply of fresh air while expelling stale air, contributing to better indoor air quality.
- Cost Savings: Lower energy consumption translates to reduced utility bills over time, making air-to-air heat exchangers a cost-effective solution for HVAC systems.
- Fast Payback: A typical WAHX systems can offer payback periods in under two years.
- Space Savings: Because of the tonnage savings smaller chilled water plants can be specified and in some applications, the entire AHU tonnage (smaller air handler) can be reduced to provide more room in tight utility rooms.
- Alternative Technology: Additionally, they can be designed as an alternative to run-around glycol loops.
Typical Applications for each system
AAHX Systems
WAHX Systems
- Commercial buildings: High-rise office buildings, universities, and retail spaces benefit from the energy savings and improved air quality.
- Residential buildings: AAHX systems are particularly effective in well-insulated and air-tight homes.
- Industrial facilities: Heat recovered from manufacturing processes can be used to pre-heat incoming air – Healthcare facilities: AAXH systems help maintain high air quality standards while managing energy costs.
- Laboratories: enhanced dehumidification makes WAHX systems ideal for environments where air quality and high humidity are a concern.
- Large Commercial buildings: WAHX systems are ideal for large commercial and industrial installations where a high-level of air exchanges are needed for healthy building air quality. In industrial applications there might be oil mist or other manufacturing airborne VOCs that need to be exchanged for fresh air. More frequent air exchanges require more cooling or heating which in turn, adds to operational costs.
- High humidity climates: Places like indoor swimming pools and greenhouses can benefit from the increased humidity control and air quality that WAHX’s can provide.
AAHX compared to WAHX
In conclusion, both air-to-air and wrap around heat pipe heat exchangers play crucial roles in HVAC systems, albeit in different applications. While air-to-air heat exchangers excel in ventilation and energy recovery, wrap-around heat exchangers offer versatile chilled water air handler tonnage and reheat savings with the added benefit of enhanced dehumidification.
The choice between the two types depends on factors such as building design, climate conditions, and specific heating and cooling requirements. By understanding the differences and advantages of each type, HVAC designers, facilities engineers and building owners can make informed decisions to optimize comfort, energy efficiency, and indoor air quality.
