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[EnergyPlus_Support] Re: Design day Vs weather file
YuanLu Li
Thank you so much.
I posted some messages on this forum, but this is the only time someone really took the time to answer. so... Thank you.
I will check the information tonight.
--- In EnergyPlus_Support@xxxxxxxxxxxxxxx, YuanLu Li <yli006@...> wrote:
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> Hi, Chris I have added my reply with your mail below.
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> Dr. Li P.S. Linda, Please make necessary corrections, if I have provided wrong information.
> To: EnergyPlus_Support@xxxxxxxxxxxxxxx
> From: robin.cris@...
> Date: Sun, 3 Jul 2011 09:33:46 +0000
> Subject: [EnergyPlus_Support] Design day Vs weather file
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> Hello
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> In most of my project till last week I used design day and last week I used for the first time the weather file.
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> I live in a country that got a lot of different weather areas but only 3 got a weather file.You can ask for weather file for the different locations from EPlus support. If you use a weather file for a site on the same latitude, the result will be very similar. The latitude controls the solar altinude angle. Inland, sea coast location would change the weather file data.
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> From what I understood, the use of weather file put the heat load on the building day by day and when I check the result on a specific date, I get the result according to that day and the effect of the previous days is shown as well. Am I right? Yes, you are right. A cool night before would have a cooler morning temperture.
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> What Happen in Design days simulation?Usually the worst conditions would be used. However, you can use any reasonable data values for other purposes.
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> Is it check the building for only that day? Yes.The DesignDay would expand the conditions you specified for a 24 hour period from mid-night to mid-night. The sumulation will run using the same data until the condition at the two ends are the same.
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> Is it duplicate that day for a week and give me the last day? No.The date chooses the solar day, the day type chooses the schedules related to that day type, etc. There are many fields that can be customized.When running, each day is simulated on its own for up to 25 times maximum, to get a converged result The final result is given as output.The next design day object will have another repeated simulation. You can watch this on the DOS screen with warm-up number in the square bracket.The object name must be different, the content may be the same.I use the CustomDay1 and CustomDay2 for Spring and Autem using the equinox dates, to study solar beam into the windows for four seasons.
> What is really happen?
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> Can I create a weather file? You can request a special one from EPlus. You can modify an existing one.What do I need for it? To create a situation which you think is a worst case, or to add some recent local conditions. You can run the weather file for a shorter period than one year. There are two modes, sizingPeriod and runPeriod. Sizing period would use the weather file for sizing information.Run period is the normal weather file simulation.The EPlus simulation assumes 23°C as the starting point for run peiod simulation. The first three day data output may not be stabilized. For your one week simulation, you should start three days before, or do a multple run to verify the first day result.
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> My last question...
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> I need to check an Hotel room.
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> If I want to use the design day simulation....You can if you do not want to care too much on night cooling conditions. If you make the previous day cool, there will be a step at midnight. If you then change the temperature profile multiplier to lower the end values, the previous day result would appear to be preserved. It can be done.
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> This room is occupied only 2 night a week and I want to simulate window opening the night before the first day the guest arrived to show how the room will be in the 2 days after that.There are wind speed and direction in the DesignDay object.It may be easier to customize the weather file, or to select a group of days from the weather file.
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> What do i need to do?
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> Do a runPeriod simulatin of weather file for, say 10 days, 6+2+2. The two days in the middle iare the occupied days. Because weather file is seasonal, when the temperature is maximum, the sun and the wind may not be in the position you want. That is why you may need to go back to the DesignDay simmulation, which is easier to change. The main difference is that the weather file can give you a range of different conditions which are already there. You can shift the day along the week by changing the first day of the year at the beginning of the EPW weather data.Output:Variable,*,DayType Index,hourly; !- Zone Average []would conform the day schedule in use in the displayed.output.
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