[BLDG-SIM] Thermal mass walls

[Christian Struck]

Nothing to rectify at all, but a small addendum.
A large thermal mass causes the heat transfer to slow down due to its
thermal resistivity. Nevertheless, if you have constant conditions of either
side of the wall you will still have a steady heat transfer. The temperature
difference between inside and outside (wind not taken into account) governs
the exchange. By comparing a wall with no thermal mass to a wall with large
thermal mass in equilibrium you will find the same rate of heat transferred.
Thermal mass is only beneficial to the internal climate under varying
internal and external conditions due to the storage capacity (time lag) of
the building fabric.

Interestingly that the point, the industry started thinking about,
activating the thermal mass of buildings further by embedding water powered
pipework into the neutral axis of ceiling slabs or walls. That allows coolth
to be stored at night by running i.e. a water to air heat exchanger to be
available for passive conditioning during the summer day. Same principle
applies for heating. 

The principle is dead simple, but its benefits difficult to assess. Here we
go again, its our game, building simulation in order to assess the systems
energetic benefits.

Check the link to Tarmac for Thermocast. (http://www.tarmacprecast.co.uk/)

Christian



> -----Original Message-----
> From:	Callan, David [SMTP:dcallan at syska.com]
> Sent:	25 June 2003 15:16
> To:	BLDG-SIM at GARD.COM
> Subject:	[BLDG-SIM] Thermal mass walls
> 
> I agree.  I assuming that the refrigerator is inside a larger facility
> shaded from the sun.  My understanding of thermal mass leads me to believe
> that it will have little effect on this refrigeration process.   Thermal
> mass plays a part when the loads change with time.  The thermal mass
> stores
> the heat to be radiated later.  This is obviously advantageous for
> building
> design in hot climates because the instantaneous solar load effect can be
> delayed to a time when the conduction load due to temperatures decreases.
> Hence reducing the peak sensible load slightly.  In the refrigeration
> process, the loads are more or less constant and direct solar would not be
> an issue.  
> 
> If anyone can elaborate on, or correct my explanation, I would appreciate
> it.  
> 
> David P. Callan, MS, PE, CEM
> Syska Hennessy Group, Inc.
> 
> -----Original Message-----
> From: Habaza11 at cs.com [mailto:Habaza11 at cs.com] 
> Sent: Wednesday, June 25, 2003 9:41 AM
> To: BLDG-SIM at GARD.COM
> Subject: [BLDG-SIM] Thermal mass walls
> 
> Yes, I am with eQuest results and your guts!. DOE also funded research on
> thermal mass which showed that thermal mass may have significant effect,
> minimal effect or adverse effect on cooling/heating  load. In theory,
> thermal mass in walls is like the balance wheel, which I don't think will
> help in reducing the cooling load in your case. Other factors such as
> infiltration, mechanical system sizing/operation, etc. may be!.
> Hussein Abaza, Ph.D.
> Assistant Professor
> ECU.
> 
> 
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