Hi, Jean
I think, you are not quite correct to say that the conductivity changes with temperature.
The heat conducted through the floor depends on the conductivity and temperature difference between the surfaces..
This is another reason why you should not use radiant floor for heating. It is not energy saving nor capital cost saving.
You should simply add insulation below the floor, and install the heating on the top of the floor.
=======================
Before the digital computing was made available, we use a slide rule and the basic formulae for this type of calculation. The model is a number of RC cascaded sections, as shown in the EPlus Engineering manual. Using a determinant or matrix method, the answer is in the form of a number of exponential with different CR values, or a single RC section as a lumped equivalent.
What you are trying to get is a steady state solution with two different temperature values across the floor.
When you change the value on one side, the value at the other side will change with a time delay. This time delay is causing problem with the simulation, when the digital calculating engine tries to force a result at a shorter computation time. (I.e. using less storage registers during computation.)
There is no thickness restriction when using analogue calculatation.
I believe that EPlus has a number of ways to do the CTF calculation. A different algorithm in Eplus may find the heat transfer across a thick slab.
===============================
Now you know the heat transfer value, you can add a component in the zone using the other equipment object and vary the amount according the difference between the garage temperature to 32°C (the interior temperature), when the heating is on with a schedule. The heat transfer condition can then remain as adiabatic.
Otherside Coefficient Schedule may not help, because the values are changing on both side of the thick slab during simulation.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Wed, 14 Dec 2011 10:38:34 +0000
Subject: [EnergyPlus_Support] Re: Easy question - Very thick massive external floor
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
![]()
__,_._,___
I think, you are not quite correct to say that the conductivity changes with temperature.
The heat conducted through the floor depends on the conductivity and temperature difference between the surfaces..
This is another reason why you should not use radiant floor for heating. It is not energy saving nor capital cost saving.
You should simply add insulation below the floor, and install the heating on the top of the floor.
=======================
Before the digital computing was made available, we use a slide rule and the basic formulae for this type of calculation. The model is a number of RC cascaded sections, as shown in the EPlus Engineering manual. Using a determinant or matrix method, the answer is in the form of a number of exponential with different CR values, or a single RC section as a lumped equivalent.
What you are trying to get is a steady state solution with two different temperature values across the floor.
When you change the value on one side, the value at the other side will change with a time delay. This time delay is causing problem with the simulation, when the digital calculating engine tries to force a result at a shorter computation time. (I.e. using less storage registers during computation.)
There is no thickness restriction when using analogue calculatation.
I believe that EPlus has a number of ways to do the CTF calculation. A different algorithm in Eplus may find the heat transfer across a thick slab.
===============================
Now you know the heat transfer value, you can add a component in the zone using the other equipment object and vary the amount according the difference between the garage temperature to 32°C (the interior temperature), when the heating is on with a schedule. The heat transfer condition can then remain as adiabatic.
Otherside Coefficient Schedule may not help, because the values are changing on both side of the thick slab during simulation.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jeannieboef@xxxxxxxxx
Date: Wed, 14 Dec 2011 10:38:34 +0000
Subject: [EnergyPlus_Support] Re: Easy question - Very thick massive external floor
Just a follow up post. I have made some (simplified) sums. Turns out the conductivity of this very thick slab is (obviously) dependant on the Temperature at my radiant floor internal source (32 deg C) and the outside external floor surface area (ceiling of underground parking open to outdoor air, somewhere between -12 and 18 deg C).
At the -12 deg C scenario, results in steady state conduction of about 9 W/m2.
At the more likely 18 deg C scenario, results in steady state conduction of about 3 W/m².
My conclusion is that heat transfer is not adiabatic enough to use this solution (applicable better when the dT is almost zero).
I'm running a simulation ATM (with the conversion errors) and reporting the inside temp after the main insulation layers to see if a pattern for the Temp here emmerges that i can use for the otherside coeff solution path.
Will report back when I find some time.
At the -12 deg C scenario, results in steady state conduction of about 9 W/m2.
At the more likely 18 deg C scenario, results in steady state conduction of about 3 W/m².
My conclusion is that heat transfer is not adiabatic enough to use this solution (applicable better when the dT is almost zero).
I'm running a simulation ATM (with the conversion errors) and reporting the inside temp after the main insulation layers to see if a pattern for the Temp here emmerges that i can use for the otherside coeff solution path.
Will report back when I find some time.
__._,_.___
Primary EnergyPlus support is found at:
http://energyplus.helpserve.com or send a message to energyplus-support@xxxxxxxx
The primary EnergyPlus web site is found at:
http://www.energyplus.gov
The group web site is:
http://groups.yahoo.com/group/EnergyPlus_Support/
Attachments are currently allowed but be mindful that not everyone has a high speed connection. Limit attachments to small files.
EnergyPlus Documentation is searchable. Open EPlusMainMenu.pdf under the Documentation link and press the "search" button.
Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe
Change settings via the Web (Yahoo! ID required)
Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured
Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe
__,_._,___