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Electrical equipment latent/radiant fraction heating impact

asked 2017-10-14 09:08:20 -0500

MA_Meilleur gravatar image

updated 2017-10-15 18:39:35 -0500


I'm fine tuning my residential home model, and I noticed something strange while playing with the radiant/latent fraction in the electrical equipment objects:

Adding latent and radiant heat to the object must contribute in reducing the heating load, but it seams to do the opposite, it increases the heating load and reduces the cooling load.

Am I understanding this wrong ? Thank you for your help !

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answered 2017-10-14 20:12:52 -0500

For the ElectricEquipment object, the electricity consumption is converted into heat additions to the zone through four pathways:

$F_{convective} = 1 - ( F_{latent} + F_{radiant} + F_{lost})$

If you keep the fraction lost the same and increase the latent and radiant fractions, the convective fraction will reduce according to this equation.

From the Engineering Reference,

Convective gains are instantaneous additions of heat to the zone air. Radiant gains are distributed on the surfaces of the zone, where they are first absorbed and then released back into the room (with some fraction conducted through the surface) according to the surface heat balances. {See Surface Heat Balance Manager / Processes in this document}. Latent gains must be handled by ventilation or air conditioning equipment.

So, the combination of reduced convective gains and increased radiant gains are resulting in increased heating loads. This is because there is less instantaneous heat addition to the zone air from the convective portion, and the increased radiant gains to the surfaces are likely not fully released back to the room.

The increased latent gains must be handled by air conditioning equipment, which would normally result in increased cooling loads IF the system can dehumidify. For a sensible cooling system, less heat generated by electric equipment will result in decreased cooling loads.

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Asked: 2017-10-14 09:08:20 -0500

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Last updated: Oct 14 '17