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ZoneMixing:Design Flow Rate Value

asked 2018-07-31 06:18:23 -0500

Siv's avatar

updated 2019-06-06 13:18:50 -0500

I was wondering if there any standards or any specific values for ZoneMixing: Design Flow Rate experts use while sizing zones ? I was able to get values for infiltrations from Spitler Jeffrey, but I was unable to get anything on ZoneMixing. Do, experts even consider it while sizing zones because it appears to be a very small value compared to the other loads and it is negative too. So, please share your idea regarding the concept of ZoneMixing.

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answered 2018-08-05 20:24:13 -0500

updated 2018-08-06 20:18:00 -0500

ZoneMixing can be used for a variety of reasons, but one common reason might be to account for transfer air between zones. In this case, yes, designers would account for the impacts of transfer air on zone sizing. But this is all hard-sized, so you have to tell EnergyPlus how much transfer air is coming from Zone 1 into Zone 2. It won't do that calculation for you.

Common uses of transfer air are for restrooms, where they have no supply air, only exhaust air transferred from adjacent spaces. Other uses are in spaces like kitchens, which have exhaust airflow rates that exceed the supply airflow rate. In this case, a designer would use transfer air to minimize or eliminate bringing in outside air above the minimum requirement (also called makeup air).

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Thank you for your response. And thank you for the information regarding where and how it is used. However, since this is hard-sized, could you please tell me what is the ideal value of zone mixing that is usually used in the industry ? Or what is the maximum allowable ZoneMixing:Design Flow Rate value ?

Siv's avatar Siv  ( 2018-08-05 23:26:05 -0500 )edit

There isn't really an answer to that. It depends on your exhaust flow rate requirements, which vary based on application or on the local code requirements. Just like there isn't an answer to how much air is supplied to a zone to meet the cooling load. The answer is.. it can be anything, depending on a variety of parameters.

There are other applications for ZoneMixing that I am not too familiar with, such as to model natural ventilation.

Anna Osborne Brannon's avatar Anna Osborne Brannon  ( 2018-08-06 20:17:43 -0500 )edit

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Asked: 2018-07-31 06:18:23 -0500

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Last updated: Aug 07 '18