No need to dig too deep into the EPlus algorithm without understanding why you are doing the simulation.
The EPlus is designed to calculate the property of the building with the sun radiation, outdoor air temperature and humidity, ground temperature, and site shading as the boundary condition.
I have not look up the manual. If 's' is surface and 'i' is interior, then Tsi is the zone mean air temperature at the start of the next calculation step. It changes during the calculation, and finally at the new zone mean air temperature for the next cycle.
The EPlus calculate the demand and following calculation convert them into supply capacity, and loses efficient all the way. (fans, compressors, pumps, coils, heat exchanges, i.e. system and plants.)
If you need x watts to heat a zone, a baseboard heater, as an example, should have the same power. If less than x, under sized. If larger than x, use PLR to adjust.
If the heat balance is to be provided with air, then the temperature difference and flow rate would provide the capacity information to match. Fan motor efficiency is to be added. The DX coil and the compressor motor and condenser fan etc. all add to the power equipment. So a constant COP value is used to simplify the calculation, if the exact performance curve is not available. With the performance curve, the COP is varied for each time step to match the demand.
When you have equipment in cascade, the preceding equipment is the demand. The tower in the condenser loop will treat the condenser coil condition as the demand.
You may threat these as post processing with table look up at each internal time step after the zone demand is known..
"So in the first step, we get an estimate of the air system energy required to balance the equation with the zone air temperature, how can we get this as a demand and determine the actual supply capability? "
First step is to get the zone demand, if you require HVAC.
The HVAC power needed to maintain the set point zone temperature at the thermostat provides the demand value. . Without HVAC, the zone will have the natural temperature at that exterior conditions, i.e. no HVAC demand, which is the most energy saving condition.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: bokelai1989@xxxxxxxxx
Date: Thu, 16 Aug 2012 20:58:09 +0000
Subject: [EnergyPlus_Support] Hi, questions about solving ODES in Energy Plus
__._,_.___
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.
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The EPlus is designed to calculate the property of the building with the sun radiation, outdoor air temperature and humidity, ground temperature, and site shading as the boundary condition.
I have not look up the manual. If 's' is surface and 'i' is interior, then Tsi is the zone mean air temperature at the start of the next calculation step. It changes during the calculation, and finally at the new zone mean air temperature for the next cycle.
The EPlus calculate the demand and following calculation convert them into supply capacity, and loses efficient all the way. (fans, compressors, pumps, coils, heat exchanges, i.e. system and plants.)
If you need x watts to heat a zone, a baseboard heater, as an example, should have the same power. If less than x, under sized. If larger than x, use PLR to adjust.
If the heat balance is to be provided with air, then the temperature difference and flow rate would provide the capacity information to match. Fan motor efficiency is to be added. The DX coil and the compressor motor and condenser fan etc. all add to the power equipment. So a constant COP value is used to simplify the calculation, if the exact performance curve is not available. With the performance curve, the COP is varied for each time step to match the demand.
When you have equipment in cascade, the preceding equipment is the demand. The tower in the condenser loop will treat the condenser coil condition as the demand.
You may threat these as post processing with table look up at each internal time step after the zone demand is known..
"So in the first step, we get an estimate of the air system energy required to balance the equation with the zone air temperature, how can we get this as a demand and determine the actual supply capability? "
First step is to get the zone demand, if you require HVAC.
The HVAC power needed to maintain the set point zone temperature at the thermostat provides the demand value. . Without HVAC, the zone will have the natural temperature at that exterior conditions, i.e. no HVAC demand, which is the most energy saving condition.
Dr. Li
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: bokelai1989@xxxxxxxxx
Date: Thu, 16 Aug 2012 20:58:09 +0000
Subject: [EnergyPlus_Support] Hi, questions about solving ODES in Energy Plus
Hi, Dr. Li,
Sorry to bother you..... I have some difficulties in studying the engineering manuals of the Energy Plus. So I would like to ask you in your inconvenience.
I am studying how Energy Plus does the calculation in getting the zone temperature. I have two questions about the engineering manual of Energy Plus:
1. As to the equation (6) On page 8, to get an estimate of Q(sys), we need to know all the temperatures. The outside door temperature and the ground temperature are provided, and T(z) is the setpoint temperature but how about the T(si)? How can we know the surface temperature?
2. On page 11, in the "Summary of predictor-corrector procedure", it mentions that the second step is "With that quantity as a demand, the air system is simulated to determine its actual supply capability at the time of the simulation. This will include a plant simulation if necessary."
So in the first step, we get an estimate of the air system energy required to balance the equation with the zone air temperature, how can we get this as a demand and determine the actual supply capability? How does this work?
Thanks!
Best,
Na
Sorry to bother you..... I have some difficulties in studying the engineering manuals of the Energy Plus. So I would like to ask you in your inconvenience.
I am studying how Energy Plus does the calculation in getting the zone temperature. I have two questions about the engineering manual of Energy Plus:
1. As to the equation (6) On page 8, to get an estimate of Q(sys), we need to know all the temperatures. The outside door temperature and the ground temperature are provided, and T(z) is the setpoint temperature but how about the T(si)? How can we know the surface temperature?
2. On page 11, in the "Summary of predictor-corrector procedure", it mentions that the second step is "With that quantity as a demand, the air system is simulated to determine its actual supply capability at the time of the simulation. This will include a plant simulation if necessary."
So in the first step, we get an estimate of the air system energy required to balance the equation with the zone air temperature, how can we get this as a demand and determine the actual supply capability? How does this work?
Thanks!
Best,
Na
__._,_.___
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.
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