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E+ PMV-PPD calculation mismatch

asked 2016-02-11 10:38:22 -0500

Peter Horvath gravatar image

updated 2016-02-11 10:58:30 -0500

hi all!

Currently i'm investigating the PMV-PPD outputs of a DesignBuilder simulation. I exported the hourly PMV-PPD values and the ones which correstpond them (air temperature, radiant temperature, air velocity (0,137), rel.humidity, metabolic rate, clo value) When i calculate the PMV values from the 6 variables in excel i get more than 60% differnce between my calculation and the DB (e+) calculation.

Can anyone help me finding the reason of the difference? Have anyone faced this problem before?

thanks a lot, Peter

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answered 2016-02-12 08:20:32 -0500

Archmage gravatar image

I would suggest getting a copy of ASHRAE standard 55 and comparing your spreadsheet calculations to the sample calculations in the appendix. This questioning of EnergyPlus's PMV calculations has come up many times over the years and they have been checked and rechecked again and again. Note that the averaging when using hourly values may be misleading -- it is better to use timestep frequency data.

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I've checked my spreadsheet, comparing to ASHRAE 55, it works correctly. As you written, the problem should be caused by averaging the timestep data. Unfortunately i can only access the hourly data, so if anyone tells me how to get the timestep data i will check them!

Peter Horvath gravatar image Peter Horvath  ( 2016-02-24 03:41:02 -0500 )edit

Use "Timestep" frequency in the Output:Variable input objects.

Archmage gravatar image Archmage  ( 2016-02-26 10:02:03 -0500 )edit

I would suggest using the CBE online Comfort Tool to Calculate both PPD and PMV at all your different conditions.

simmonds gravatar image simmonds  ( 2017-01-18 19:53:06 -0500 )edit

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Asked: 2016-02-11 10:38:22 -0500

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Last updated: Feb 12 '16