A dehumidifier’s heat recovery system can leverage “energy rich” exhaust air to provide cost-effective sensible heating to the indoor pool environment.
When deciding on a heat recovery system, natatoriums generally consider either the glycol runaround loop method or the flat plate heat exchanger method.
The glycol runaround loop heat recovery system makes use of multi-row finned tube coils and circulates a glycol fluid for heat exchange between exhaust and outdoor airstreams. The flat plate heat exchanger method is comprised of several heat plates with multiple channels through which liquid can flow.
There are several key considerations when determining which approach to specify…
In cold climates, heat recovery is needed most in winter. This poses a problem for indoor pools located in these regions, as the heat recovery system must not be vulnerable to the potentially destructive effects of low outdoor temperatures.
Flat plate heat exchangers frequently experience difficulties with draining away condensate, leading to a high risk that the condensate will freeze in the device if the installation is located in a colder climate. This requires that air be bypassed to prevent the plates from freezing, reducing its effectiveness when you need it most.
However, with the glycol runaround loop approach, there is no risk of the condensate freezing and therefore no need to bypass air, making this a far more efficient approach for cold weather applications.
Flat plate heat exchangers are typically not coated or otherwise protected from corrosion, whereas glycol loops use natatorium-grade coated coils. With the former approach, there is an annual de-rate as the coil oxidizes and corrodes, but with the glycol approach, this is no longer a concern.
Dectron coils are fully dipped for maximum corrosion protection.
Plate heat recovery devices require special and complicated air paths within the unit, increasing the unit size and weight. However, with the glycol runaround loop approach, the heat recovery coil set fits directly onto the outdoor air and exhaust air openings already provided on the unit and does not increase the cabinet size. This is an important consideration on applications where roof loads are a concern.
Effectiveness may be the most important consideration of all.
Plate heat exchangers force air down into different, complicated paths, creating a very high static pressure loss. This in turn requires the use of more fan horsepower, which raises energy costs 24/7. However, the introduction of the glycol heat recovery coils into the existing air streams offers a substantially lower overall airside pressure drop, providing a lower operating cost and increased heat recovery effectiveness.
Given that the glycol method meets all the key criteria, Dectron’s dehumidification veterans recommend this approach over the flat plate heat exchanger for the indoor pool environment.