Question-and-Answer Resource for the Building Energy Modeling Community
Get started with the Help page
Ask Your Question
2

Thickness of internal mass material

asked 2018-04-29 08:12:27 -0500

arnodiels's avatar

updated 2018-04-29 10:50:34 -0500

Hi everyone

I have a rather simple question, but I haven't been able find the right answer yet. I am doing some research on internal thermal mass and would be using the "InternalMass" section in EnergyPlus.

In the 'engineering reference' I found that for internal mass object that "if both faces are within the zone, this situation can be modeled either by creating another internal mass surface with the reverse construction, or, for symmetric constructions, simply doubling the area of the surface." (3.7 Adiabatic Boundary Conditions)

My question now is, which thickness do I use when such an object has its both faces within the zone? When doubling the area of the surface, do I use the full thickness or only half of the thickness?

edit retag flag offensive close merge delete

1 Answer

Sort by ยป oldest newest most voted
1

answered 2018-05-04 14:32:31 -0500

Half. Since you are doubling the area, if you want the correct total mass for the internal mass material, the thickness should be divided in half.

edit flag offensive delete link more

Comments

Yes, I would think that too, but in search of the answer I performed some simulations on a very basic model. A space of 3m x 3m x 3m, no insulation, only subjected to varying outside boundary conditions.

Out of these simulations I calculated the average diurnal temperature range and how increasing the amount of internal mass decreases the average diurnal temperature range within the test cell. I did these simulations using two different methods for entering the internal mass.

arnodiels's avatar arnodiels  ( 2018-05-06 03:53:38 -0500 )edit

The first method used the 'ZoneCapacitanceMultiplier:ResearchSpecial' object in which I increased the 'temperature capacity multiplier' in according with the amount of internal mass. The second method used the 'InternalMass' object in which I performed simulations using the full thickness and half of the thickness.

When analysing these results I found that the results when using the full thickness approximates the results of the capacitance multiplier method better than when using only half of the thickness.

arnodiels's avatar arnodiels  ( 2018-05-06 03:58:40 -0500 )edit

Your Answer

Please start posting anonymously - your entry will be published after you log in or create a new account.

Add Answer

Careers

Question Tools

Stats

Asked: 2018-04-29 08:12:27 -0500

Seen: 436 times

Last updated: May 04 '18