Based on information of a certain room, like room's volume in m3, dry air specific heat and dry air density. How can one calculate the temperature if we know how much thermal energy is present in the room.
Information needed to study HVAC systems.
Dear Mohammed,
I do not think there is a connection between Joule (or BTU) and degrees Celsius. Joules or BTU can be converted to Celsius heat unit. The Celsius heat unit is the energy required to increase the temperature of one pound of water by one degree Celsius (or 1.8 degrees Fahrenheit) at a constant pressure of one atmosphere. One Celsius heat unit is equal to 1.8 British thermal units. 1 CHU = 1.8 BTU .
Regards
Bachir ACHOUR
as it is known joul/sec= watt, by the other hand Q(watt)= mc(dT)=m(u2-u1).
u=internal energy at desierd temperature( you can find them in thermodynamic tables)
Mr. Mohammed Farhan
greeting
there is a method to calculating heating and cooling load depending on temperature. this method calls (VBDD: variable base degree method)
you can get more details from hand book and papers). also you can read the paper attached.
Hello,
I think that you know how much energy is introduced or retired from the house by your system and you want to know the resulting temperature.
The temperature in the house varies with thermal properties of the materials used in the walls, roof , ground, etc. You must know also if the house is thermally insulated or not and also meteorological conditions outside the house (air temperature, humidity , wind, etc ). In addition to these parameters the temperature inside the house is related with the number of people in the house, furniture…….
There are different methods of calculating the heating and cooling load (energy required to obtain a certain temperature in the house ) but you must have more information about your problem .
If you want to solve only a simplified version of the problem considering only dry air in the room you can use the method presented by Babak Arjmand, 4 days ago.
Maria Rosa Duque
University of Evora, Portugal
Hello everyone,
This is for a simulation model that mimics the process of an HVAC system in an office space.
I currently use this calculation to know how much energy is present in a room any second as --> considering the temperature is 23 degree Celsius.
Energy U= cPmΔT
(dry air specific heat) cP=1.00J/g K (dry air density) ρ =1275g/m3 (room area) A=30m2 (room height) h=3m (mass of air) m= ρAh
U= (1) (1275)(30)(3)(23)=2639250 Joules.
So this joules need to be converted to BTU/second.
Later,, a different BTU/second is used to convert back to joules/second and used in the same U formula to calculate the corresponding temperature of that energy.
Please advice if this is correct ..
Hello,
It seems that your problem is related with Units used. If you use the SI system of units you must use the unity of Kg for mass.
If you want to make the conversion of power units you can used the relation 1BTU =1055.056 J. I think that this will be enough but I do not know why do you need to change you unity system. Do you have any problem in working with W (Watt = Joule/ s) ?
Maria Rosa Alves Duque The HVAC community understands the BTU units. It was easier to keep the system in BTU. But the calculations are mostly in Joules..
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