ACT Thermal Passive Valve

Innovative Heat Pipe Based Energy Recovery Systems With The ACT-TPV (Thermal Passive Valve)

Key Benefits of ACT-Thermal Passive Valves:

Passively controls the amount of valuable reheat in a
WAHX system as outside air temperatures change
Allows for a more effective WAHX (increased energy savings)
without overheating the supply air
A 4 row WAHX with ACT-TPVs can achieve 52% more
energy savings versus a standard 2 row WAHX
Significantly increases energy recovery under part-load conditions

An HVAC industry first concept This patent pending development greatly enhances the energy recovery capabilities of ACT’s Wrap-Around Heat Pipe Heat Exchanger (WAHX) by up to 70%. The ACT-TPV incorporates a phase change actuated valve mechanism. The phase change valve mechanism opens and closes based on the heat pipes refrigerant temperature. This allows ACT’s WAHX with Thermal Passive Valves to automatically modulate the heat exchanger effectiveness as the temperature increases and decreases to maximize pre-cool and re-heat savings across a wide range of operating temperatures without overheating the supply air.

WAHX energy recovery units are typically used for new or retrofit dedicated outside air system (DOAS) projects. The design of the WAHX system, for example the number of rows and the fin density, is selected based on the maximum expected outside air temperature and the maximum supply air temperature desired. This results in a WAHX that is operating at its full potential at the highest expected outside air temperature. At lower outside air temperatures, the pre-cool and re-heat savings are proportionally less. A WAHX with ACT-TPVs allows for maximum savings over a significantly wider operating range, resulting in energy savings increases of 50 to 70%.

So how does the ACT-TPV Work?

Wrap Around Heat Pipe with thermal passive valves

WAHX Energy Recovery with ACT-TPVs

ACT’s new Passive Thermal Control Valve allows the WAHX to work optimally at the average or typical conditions without overheating the supply air as the outdoor temperature increases. ACT’s WAHX with Thermal Passive Valves automatically modulates the WAHX effectiveness as the temperature increases and decreases to maximize pre-cool and re-heat savings across a wide range of operating temperatures without overheating the supply air above the maximum desired supply air temperature. Even on part-load days, ACT-TPVs maximize energy recovery dollars saved. This all happens without temperature sensors, controllers, algorithms and the associated maintenance issues. It just works!

ACT-TPV Benefits:

For many applications, a 2-Row WAHX system is selected. This provides the maximum allowable supply air temperature at the maximum expected outside air temperature. The energy savings are only optimal at the design point. The table below shows the added energy recovery benefits as more rows of heat pipes are added to the initial 2-Row WAHX system.

WAHX Energy Recovery systems are selected by the energy transfer that is derived by the number of heat pipe rows needed to meet the specified engineering requirement. The chart above shows the added energy recovery benefits as more and more rows of heat pipes are added to the initial 2-Row WAHX system. Each additional row allows for significant energy savings, while the ACT-TPVs prevent the supply air temperature from exceeding the maximum desirable temperature. The additional rows and the ACT-TPVs do increase the initial cost; however, this is quickly compensated for by 50 to 70% increased energy savings.

For the WAHX described in the table above (Fort Lauderdale, Florida) the payback periods in every case are 2 years or less. For this particular installation, a 4-Row WAHX will increase savings by 52% and payback in 1.6 years and a 6 – Row WAHX will increase savings by 70% and payback in 2 years. Every installation area is different so a quick performance evaluation by the ACT Energy Recovery team can identify the best approach.