Re: [EnergyPlus_Support] Re: Design Day V.S. Schedule

Regards,

Qianmin

On Sat, Jul 16, 2011 at 9:59 PM, Jia Hu <hujia06@xxxxxxxxx> wrote:

Hi:

Just for your convenience.

The following is from the I/O ref.,

· For a window without an interior shading device, this heat flow is equal to:

[Window transmitted solar ]

+ [Convective heat flow to the zone from the zone side of the glazing]

+ [Net IR heat flow to the zone from zone side of the glazing]

?[Short-wave radiation from zone transmitted back out the window]

+ [Conduction to zone from window frame and divider, if present]

Here, short-wave radiation is that from lights and diffuse interior solar radiation.

·         For a window with an interior shading device, this heat flow is equal to:

   [Window transmitted solar]

+ [Convective heat flow to the zone from the air flowing through the gap between glazing

and shading device]

+ [Convective heat flow to the zone from the zone side of the shading device]

+ [Net IR heat flow to the zone from the zone side of the glazing]

+ [Net IR heat flow to the zone from the zone side of the shading device]

? [Short-wave radiation from zone transmitted back out the window]

+ [Conduction to zone from window frame and divider, if present]

The total window heat flow can also be thought of as the sum of the solar and conductive

gain from the window glazing.

On Fri, Jul 15, 2011 at 8:07 PM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

You need to look at the name carefully.

If Zone average [ ] is included, it is for all the windows in that zone.

Zone with individual window name is for that window only.
============================

zone window heat gain is not for just the radiation energy.

When the outdoor air temperture is higher than the zone, there will be a heat gain. I.e., there is window heat gain, when the zone is cooled.

Your can turn off the skyclearness in the DesignDay object to observe this.
====================
WinterDesignDay object usually has the skyclearance set to zero.
======================
If there is blind installed and closed, part of the radiation portion is there, if not reflected..

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: zqianmin@xxxxxxxxx

Date: Fri, 15 Jul 2011 16:53:20 -0700

Subject: Re: [EnergyPlus_Support] Re: Design Day V.S. Schedule

question about output variable: zone window heat gain

Does it include all the Solar radiation from window in a zone? Thanks.

On Fri, Jul 15, 2011 at 1:55 PM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

May comments below in red.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: zqianmin@xxxxxxxxx

Date: Fri, 15 Jul 2011 08:29:33 -0700

Subject: Re: [EnergyPlus_Support] Re: Design Day V.S. Schedule

Dr. Li,

Thank you. I have questions about design day and sizing.

In energyplus, the system will be sized on design day, and shown in hvac sizing summary. It will take the solar information from weather file and use the weather temperature from whatever we input in SizingPeriod:DesignDay, is it right?

No.
When you use the sizing DesignDay, the weather file need not be present. Therefore, none of the information in the weather file is used.

If you use sizingPeriod:weatherfile, then the information in the weather file are used.
You can run both the sizingPeriod:DesignDay and sizingPerid:weather file. The latter can be in one day, one week, one month or one year period, or any period, and repeated a few times to make sure the result have been stabilized. I think, I mentioned this in an earlier reply.

When I run the simulation for a full year, and looked at the report, Space Gain Component at cooling peak month, the maximum zone/sys sensible cooling rate [W] happened on July 10th, 07:15, not on my design day July 21th. Since I use school schedule, there is no occupancy on July 10th.

The SummerDesignDay is always on July 21. This is based on the TMY convention for all the weather files in the Northen Hemisphere.
That was why I said that you need not worry too much about the schedule. It is only the first step to get some feel about the building ahd NHAC conditions. Your zone sizing and system sizing objects have some limiting conditions. These are taken account. July 21 is used to calculate the solar angle at your location.

================
The temperature is one which is statically high enough 0.4% is the percentange of days in the year which may statistically exceed the temperature given. The wet-bulb sets the humidity ratio at the max temperature and is constant for the whole day.

The profile is fixed to give you a fixed 24 hourly curve, which has a miximum at 2 pm and a minum at 5 am with a value = Max - difference.
If the summerDesignDay is listed in the schedule as a separate item, the sizing will use those schedule values.

Because you want to have the maximum demand for the system, therefore, the schedule for sizing is usually the weekdays.
You need not use the 1.2 multiplier for sizing, because that is probably included for those people who are not using EPlus for bulding design.

To size the unit, I want to get the maximum cooling load. I feel like if I change my design day to July 10th in sizing period, I may get a larger calculated design load, but, it's not true. When I change it, the cooling load in hvac sizing summary didn't increase.

If you use the DesignDay sizing, the largest load will be on June 21, the longest day of the year. However, statistically, the temperature on that day is lower and a max. on July 21, because the groud need time to warm up. It is not the actual temperature of the current year or every year..

The peak value in the result may be changed by the internal load. However, you only have one day of cooling values in the Zsz.csv. If you change the lights, people, etc. the value will change.

Changing the date, only change the solar angle. The schedule is not changed. The ..Zsz.csv should be different. The summary report should not have any values in the monthly section.If you change the 'SummerDesignDay' field to Monday, the Monday schedule will be used for sizing.

The value listed in report of space gain components at cooling peak month, are they the maximum number during each month or they are the averaged number again? zone people total hat gain is zero in Jan, Feb, July, Nov, and Dec, which is totally different from my occupancy schedule, I have people in building during these months. How should I understand this report? Thanks a lot.

Report html will have monthly averaged values only when you do the annual simulation using runPeriod. The maximum value date and time shows you when the maximum value occured at that month, which is in the .csv or .eso file.

If you use annual sizing simmulation, I do not know what would be liste,d as I have not done that way myself, because you do not know what data is used for sizing.
If your schedule have an error or listed in the error file as not used, they will not be used.

Therefore, all those fields will be zero. If the people is calculated to less than one, it will be zero as well. You can view these by turning on the report on schedule values as in one of mine IDF.

Qianmin

On Fri, Jul 15, 2011 at 7:46 AM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

Sorry, I did not sent you any attachments.

The file names meant to be examples to show the Ssz and Zsz.

You would have these files in your simulations runs.

However, I have resent the IDF which has the unused material and construction removed.
The report variable section is different from the skilight version.
======================
It is also not necessary to have completed long schedules with four or more sections.

For sizing, SummerDesignDay is for Cooling set point schedule. WinterDesignDay is for heatingDesignDay set point. All the schedules are for holidays and working days. Only you do want the DesignDays to be in some working days and in some holidays, then you need to list tem in a separated time period. Because, it is for sizing, it should be in the two worst case condition.

If you really wanted to enter a complicated and exact occupancy or usage conditions, you can set up a spread sheed and called it a unique schedule file, with a row for each hour of the year. Each column can be specified for use by rhe relevant schedule object. I am not suggesting that you should do this. However, it is an available EPlus option.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: zqianmin@xxxxxxxxx

Date: Thu, 14 Jul 2011 17:07:51 -0700

Subject: Re: [EnergyPlus_Support] Re: Design Day V.S. Schedule

huh,,I didn't see any attachment.

On Thu, Jul 14, 2011 at 3:52 PM, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

For sizing maximum, there are csv files with sz in the file name.

QMZ_DD_skylightSsz.csv   for system sizing.QMZ_DD_skylightZsz.csv   for zone sizing.

Dr. Li

To: EnergyPlus_Support@xxxxxxxxxxxxxxx
From: zqianmin@xxxxxxxxx
Date: Thu, 14 Jul 2011 15:45:34 -0700

Subject: Re: [EnergyPlus_Support] Re: Design Day V.S. Schedule

Oh, got it! So this number is kind of useless to size the hvac system. I didn't realize they are averaged number before. What I want to look at are the number in .csv file. Thank you!
Qianmin