To further Ned’s explanation, below are the units connected with each term where Value 1 & 2 are “Heat Capacity” or “Thermal Capacitance” and the term “SpecificHcombine” would
probably be more appropriately represented as “Total (or combined) Heat Capacity” with units of J/K:
|
Heat Capacity or Thermal Capacitance
(Transient Conduction) |
|
The energy required to raise the temperature of the layer is given by: |
|
Cth = Mcp =
pVcp |
|
|
|
Cth = Heat Capacity or thermal capacitance of the wall or roof layer (J/K) |
|
M = Mass of a wall or roof layer (kg) |
|
cp = specific heat of the wall or roof layer material (J/kgK) |
|
p
= density of the wall or roof layer material (lbm/ft3) or (kg/m3) |
|
V
= Volume of the wall or roof layer (ft3) or (m3) |
Jerry Phelan
Codes and Standards Advocate
Bayer MaterialScience
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Saturday, March 14, 2015 8:21 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: RE: [EnergyPlus_Support] Fw: Specific heat
First you have to assume that what you are blending is evenly mixed, then this should make sense:
Volume1 x Density1 x SpecificH1 = Value1
Volume2 x Density2 x SpecificH2 = Value2
SpecificHcombine = (Value1+Value2)/(VolumeCombine x DensityCombine)
Ned Lyon, P.E. (MA, WV)
Staff Consultant
SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct
617.285.2162 mobile
781.907.9009 fax
www.sgh.com
From:
EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Saturday, March 14, 2015 6:30 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Fw: Specific heat
Can anybody please tell me how to calculate combined specific heat of a compound material from two or more values of specific heat of its components.
For example, to calculate specific heat of fly ash brick masonry from value of specific heat of fly ash brick suppose 'x' & value of specific heat of cement mortar suppose 'y'.
Thanks in advance !!!!
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Posted by: Jerry Phelan <jerry.phelan@xxxxxxxxx>
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