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why there are two adaptive thermal comfort model equations?

asked 2015-07-03 12:06:15 -0600

oat gravatar image

updated 2015-11-12 15:34:21 -0600

I found two different adaptive thermal comfort model equations from de Dear et al's two papers.

1) Comfort operative temperature = 18.9 + 0.255*[mean outdoor daily effective temperature]

... from the paper

de Dear, R., & Brager, G. S. (1998). Developing an adaptive model of thermal comfort and preference. ASHRAE Transactions, 104(1), 145-167.

2) Tcomf = 0.31*[Ta,out] + 17.8

... where Tcomf means indoor comfortable temperature, and Ta,out means mean outdoor air temperature,

... from the paper

de Dear, R., & Brager, G. S. (2002). Thermal comfort in naturally ventilated buildings: revisions to ASHRAE Standard 55. Energy and Buildings, 34, 549-561.

I don't have access to the latest ASHRAE Standard 55-2013 now, so I don't know which one is actually adopted by ASHRAE.

So, can anybody know about adaptive thermal comfort model kindly advise?

Thank you!

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answered 2015-07-03 12:39:48 -0600

The second one is in the Standard.

It is not the transient outdoor temperature that is the independent variable, though. It is the "prevailing mean outdoor air temperature," which is a moving average with a window of at least 7 days and at most 30 days (or more if you use a more complex weighting scheme).

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Thanks, Adams!

Do you know why de Dear decided to "update" the regression equation from the one shown in his 1998 paper?

oat gravatar image oat  ( 2015-07-04 08:07:49 -0600 )edit

From de Dear and Brager's 2002 E&B article: "The outdoor climatic environment for each building was characterized in terms of mean outdoor dry bulb temperature Ta,out, instead of the ET* index that was originally proposed in the first publication of the ACS [5]. The reason for the downgrade to a simpler outdoor temperature expression is that the theoretically more adequate thermal indices such as ET* require both specialized software and expertise that most practicing HVAC engineers are unlikely to possess."

Adams Rackes gravatar image Adams Rackes  ( 2015-07-06 14:42:11 -0600 )edit

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Asked: 2015-07-03 12:06:15 -0600

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Last updated: Jul 03 '15