Unmet Hours - RSS feedhttps://unmethours.com/questions/Question-and-Answer Resource for the Building Energy Modeling CommunityenWed, 13 Oct 2021 20:57:33 -0500How to simulate a certain floor of a buildinghttps://unmethours.com/question/62968/how-to-simulate-a-certain-floor-of-a-building/Hello.
(This may be basic question,)
I would like to ask you two questions about simulating a certain floor of an office building using EnergyPlus.
(1) How to model ceiling and floor of a room adjacent to conditioned rooms.
I came up with the following two ideas.
1. Set the boundary condition: adiabatic
2. Enter the same model on the upper and lower floors
I think 1. is the simplest, but I am worried that the heat capacity of the ceiling and floor slabs is properly added. Please let me know if there is an officially recommended way.
(2) How to model ceiling and floor of a room adjacent to unconditioned rooms.
In our country, we use “adjustment factor” to roughly give the temperature of the next room in the load calculation.
Is it possible to set such boundary condition in EnergPlus?
(I also thought about entering zones as (1)-2., but I’m not sure how appropriate the ambient temperature of the unconditioned room will be. )
Also, I would like to run this simulation with a simple model as much as possible.R-FujiwaraWed, 13 Oct 2021 20:57:33 -0500https://unmethours.com/question/62968/Is it possible to change the units of an output report?https://unmethours.com/question/62064/is-it-possible-to-change-the-units-of-an-output-report/ For example, i want to change the units of the report "Zone Windows Total Gain Rate", which appears in [W] and i want in [W/m2]. My case study is a single house family.
ThanksRicardoCordeiroMon, 27 Sep 2021 10:57:46 -0500https://unmethours.com/question/62064/How do I simulate Barra-Costantini system (passive solar system) with energyplus?https://unmethours.com/question/60231/how-do-i-simulate-barra-costantini-system-passive-solar-system-with-energyplus/ Hello, I want to simulate Barra-Costantini system (passive solar system) with energyplus. This system is similar to Trombe wall except that the heated air moves into the ceiling. And between the wall and the glass is a metal plate. How do I do this simulation so that I can output the rate of air exchange and energy consumption?As well as the zone temperature and the temperature inside the ceiling?
h.aSun, 29 Aug 2021 07:00:22 -0500https://unmethours.com/question/60231/Window heat transferhttps://unmethours.com/question/53163/window-heat-transfer/ Hello all,
I already looked at previous questions but I still can not find an answer:
For a simple energy plus model, a room with one southside two pane glass window ( no frame, no divider, etc...)just glass:
(Surface Window Heat Loss Energy) is not equal to (Window Inside Face Net Surface Thermal Radiation Heat Gain Energy) and (Window Inside Face Convection Heat Gain Energy).
The calculation is for 1 am, so there is no solar radiation. There is no light and internal heat, so heat loss through inside window face should be only by convection and radiation. The difference is small but I wonder what cause this difference.
(Surface Window Heat Loss Energy) is a little higher than the sum of (Window Inside Face Net Surface Thermal Radiation Heat Gain Energy) and (Window Inside Face Convection Heat Gain Energy). This is also the same for single glass window, Why?
Thank you,
asroThu, 18 Mar 2021 12:06:44 -0500https://unmethours.com/question/53163/blind can not stop heat escapehttps://unmethours.com/question/55962/blind-can-not-stop-heat-escape/Hello, I am modeling a automatic interior venetian blind for a small office. I notice when I use "OnNightAndOnDayIfCoolingAndHighSolarOnWindow" and "OffNightAndOnDayIfCoolingAndHighSolarOnWindow" to calculate annual energy consumption, the results show no difference at all. I was expected the blind can stop heat escape in some degree when it is fully deployed at winter night but the results show opposite.
My supervisor told me that this is the limitation for the energy simulation software. Currently no software includes R-value correction from slat. My questions are:
1. Does OpenStudio take R-value correction into consideration when the blind is fully deployed?
2. If not, what is the best way to fix it/work around it to get more accurate result?
Thank you.TouispeidThu, 24 Jun 2021 00:03:48 -0500https://unmethours.com/question/55962/Heat transfer between floors placed at different heightshttps://unmethours.com/question/52630/heat-transfer-between-floors-placed-at-different-heights/In order to check compliance with a thermal comfort standard, we need to model and analyze temperature and thermal loads of 3 different floors of a building: ground floor, top floor and a floor at mid-height.
The standard recommends not to consider any surfaces adiabatic, accounting for heat transfer between all adjacent surfaces, so that the effect of the adjacent floors are considered.
We have come up with the following procedure:
1. The floors are modeled all adjacent and we solve the adjacencies between them to establish the correspondent floor and ceiling surfaces as boundary condition objects of each other.
2. In the ‘BuildingSurface:Detailed’ object, we edit the Z-coordinates to place each floor at its real height (since we account for natural ventilation and neighboring surfaces shading in these simulations, we considered we should keep the floors at the proper heights).
3. We remove Sun/Wind exposure and the View Factor to Ground from the formerly-adjacent floors and ceilings.
**The fenestration surfaces of each floor also have their Z-coordinates edited
Is this procedure technically solid? Is there a more correct or efficient way to model this?
Thank you!
Elisa MatarFri, 05 Mar 2021 14:53:18 -0600https://unmethours.com/question/52630/Modelling enclosure losses from a packaged or built-up RTUhttps://unmethours.com/question/50233/modelling-enclosure-losses-from-a-packaged-or-built-up-rtu/I need to model the impact of increased enclosure insulation on the energy used by a roof top unit. I was planning making a small zone with the an exterior boundary condition wall having UA equal to that of the purposed RTU and using that space as a supply plenum. Depending on the size of unit and the location of the coils, I would also perhaps do the same with a return plenum to capture any gain/losses driven by the return air delta T.
Assuming I can come up with a reasonable UA approximation, would this work? Is there a better way.
Concerns I have about this approach
- Appropriately modelling the inside convective heat transfer
- Accounting for the variation of air temperature as it move though the RTU / estimating the area of enclosure that is subject to the return or supply air temperatures (or even something in between like the air between the fan and heating coil on a blow through unit).
**UPDATE**
Applying the above approach to enclosure losses before the coils (via dummy return air plenum) fails to account for the mixed air temperature after outdoor air has been introduced. For this I'm hoping that i can use an EMS program to calculate the mixed air temperature accounting for jacket losses and then reset the air temperature at the coil inlet node to this calculated value.
Concerns I have about this approach
- accurately calculating the losses/gains at the mixing box
- not sure if it is possible to just reset the air temperature at the coil inlet node using EMS
Using EnergyPlus, currently 9.0 but could update if necessary.
Any advice on how best to model this would be appreciated.willyJohanMon, 28 Dec 2020 18:15:29 -0600https://unmethours.com/question/50233/Conduction Time Series (CTS) factorshttps://unmethours.com/question/51810/conduction-time-series-cts-factors/I'd like to simulate any arbitrary construction type using energy plus, I'd like to able to get the CTF coefficient's of the construction, and the CTS (Conduction Time Series) as well as RTS(Radiant Time Series) factors.
Ashrae provides CTS and RTS coefficients of various wall and roof types but I'd like to be able to generate my own for custom material arrangement's.
Need help generating an IDF file where the user specifies material layer properties and energy plus provides the Conduction Time Series factors.
Thanks in advance.OgeeThu, 18 Feb 2021 12:57:25 -0600https://unmethours.com/question/51810/How do I view the total heat transfer coefficient through surfaces in OpenStudio/EnergyPlus?https://unmethours.com/question/49264/how-do-i-view-the-total-heat-transfer-coefficient-through-surfaces-in-openstudioenergyplus/I would like to find out what the heat transfer coefficient for my floor is in my OpenStudio/EnergyPlus model in W/m2K. I have been advised to look at the EnergyPlus timeseries outputs related to surface heat gain. I have had a look at these and cannot seem to find one that relates to *total* heat flow - it seems that heat transfer is split into conduction, radiation, and convection. E.g "Surface Outside Face Conduction Heat Transfer Rate per Area [W/m2]".
Is there any way of finding out what the total heat transfer rate is in terms of W/m2K of a surface (especially the ground floor)?
Additionally to this, when trying to use the 'Add Output Variable' measure that is available on BCL, the measure seems to run successfully, stating that an output variable has been added to the simulation, however I cannot seem to find this in the output files? I was under the impression I would be able to see this in the .sql file but it does not seem to be there. Any help would be very appreciated! :) jaklloydMon, 30 Nov 2020 07:39:53 -0600https://unmethours.com/question/49264/