Re: [EnergyPlus_Support] HVAC System for a Prototyp Supermarket

Hi,

The following is the E+ example file for Accra (max goes to 30K W heat gain)

whereas your idf for Accra is 60K.

So definitely there is much heat gain in your idf, and need to look one by one where this comes from.

Now analyzing:

For supermarket_detailed.idf (E+ example file)

>Variable Name Refrigeration System Total Cases and Walk Ins Heat Transfer Rate Â SELFCONTAINEDSYSTEM

Total Maximum 9,359.61W
Total Minimum 7,210.25W
Total Average 8,356.58W

>Variable Name Refrigeration System Total Cases and Walk Ins Heat Transfer Rate Â MEDIUMTEMPSYSTEM

Total Maximum 36,319W
Total Minimum 6,391.47W
Total Average 21,240.2W

>Variable Name Refrigeration System Total Cases and Walk Ins Heat Transfer Rate Â LOWTEMPSYSTEM

Total Maximum 16,608.4W
Total Minimum 2,888.07W
Total Average 9,726.39W

Roughly total:Â supermarket_detailed.idf

Total Maximum 9,359.61+ 36,319Â +Â 16,608.4Â =62,287W
Total Minimum 7,210.25+ 6,391.47Â +Â 2,888.07Â =16,490W
Total Average 8,356.58Â Â + 21,240.2Â +Â 9,726.39Â = 39,323W

Similarly for Supermarket_Prototyp2.idf
>Variable Name Refrigeration System Total Cases and Walk Ins Heat Transfer Rate Â LOWTEMPSYSTEM
Total Maximum 8,479.86W
Total Minimum 1,704.07W
Total Average 6,256.2W
>Variable Name Refrigeration System Total Cases and Walk Ins Heat Transfer Rate Â MEDIUMTEMPSYSTEM
Total Maximum 42,083.2W
Total Minimum 3,107.71W
Total Average 16,787.9W

Roughly total:Â Supermarket_Prototyp2.idf

Total MaximumÂ 8,479.86Â +Â Â 42,083.2Â =50,563W

Total MinimumÂ 1,704.07Â Â +Â 3,107.71Â Â Â =4,811W
Total AverageÂ 6,256.2Â +16,787.9Â Â = 23,044W

So what does this show, just even seeing the average there is almost 39.3-23.0=16.3kW more refrigeration inÂ supermarket_detailedÂ versusÂ Supermarket_Prototyp2.idf, which means you do not need an AC for the amount of 16.3kW since the fridges inside are doing it for you. The other I will leave for you to analyze is to switch OFF all the fridges in both the above files and see how much is the total AC load difference, that you would found out maybe proportional to the floor area. So I am not sure if you have that much time left to analyze such detailed things, but that is what research is - need to go one by one to see where the exaggerated difference is coming from. The other is that I have advised you in one of my emails that, do incremental changes to the original file to trace where the exaggerated change is coming from. You can still do that. I will leave such type of debugging to you and will get back to you for the HVAC performance curves hopefully tomorrow.

If what I said above is not clear let me know.

Best wishes,

Tilek

On Mon, Jul 1, 2019 at 1:40 AM Tilek Aberra <tilek.aberra@xxxxxxxxx> wrote:

Hi,

I start to look at your question in regards the HVAC, this area is not my expertise (so no quick resp[onse)Â - but I am looking into it. What I did in the IDF I sent is to get the simulation to continue, yes if I doubled capacity and I should have done the same to the flow and others that vary hand in hand. Definitely, there is too much heat gain in the model, but it needs to investigate where this is coming from. You need request more output for plotting and inspect.

For instance, add these (or more from .rdd files)

Output:Variable,*,Zone Air System Sensible Heating Rate,timestep;
Output:Variable,*,Zone Air System Sensible Cooling Rate,timestep;
Output:Variable,*,Zone Air Heat Balance Internal Convective Heat Gain Rate,timestep;
Output:Variable,*,Zone Air Heat Balance Surface Convection Rate,timestep;
Output:Variable,*,Zone Air Heat Balance Interzone Air Transfer Rate,timestep;
Output:Variable,*,Zone Air Heat Balance Outdoor Air Transfer Rate,timestep;
Output:Variable,*,Zone Air Heat Balance System Air Transfer Rate,timestep;
Output:Variable,*,Zone Air Heat Balance System Convective Heat Gain Rate,timestep;
Output:Variable,*,Zone Air Heat Balance Air Energy Storage Rate,timestep;
Output:Variable,*,Zone Exfiltration Heat Transfer Rate,timestep;
Output:Variable,*,Zone Exfiltration Sensible Heat Transfer Rate,timestep;
Output:Variable,*,Zone Exfiltration Latent Heat Transfer Rate,timestep;
Output:Variable,*,Zone Exhaust Air Heat Transfer Rate,timestep;
Output:Variable,*,Zone Exhaust Air Sensible Heat Transfer Rate,timestep;
Output:Variable,*,Zone Exhaust Air Latent Heat Transfer Rate,timestep;

And what I see the sales floor has about 60K and backroom 30K Watts convective heat gain? I am not sure why, maybe the local weather has created this - so try it in the original US location and see whether it reduces. So roughly 114W/m^2 - and actually this makes sense since in AUS the assumption is 118W/m^2 (the quick estimate for house air conditioning), not as you said 50W/m2 - maybe this is true in GER or the original IDF file where it is the case.

So it needs too much debugging.

I will look at the curves question when I get time this week, sorry for the delay.

Best wishes,

Tilek

On Sun, Jun 30, 2019 at 12:15 AM Tilek Aberra <tilek.aberra@xxxxxxxxx> wrote:
I will look at it, but you can take a linear function for part load. Like at 1/4 part load the capacity will also be 1/4 of the max capacity, so forth. Only thing sometimes efficiency varies with load %age and power input can be different. Tomorrow I will respond.

Good night!

On Sun, 30 Jun 2019 at 12:08 am, larateutsch@xxxxxx [EnergyPlus_Support] <EnergyPlus_Support@xxxxxxxxxxxxxxx> wrote:

Â

Thanks a lot!Â

The File I am using in EnergyPlus does also need the Part Load Fraction Correlation Curve. But the Excel Tool (CurveFitTool) does not calculate this curve. How can I do this?Â
Â
I attached an Excel File where I put my calculations under the sheet "Prototyp". My Building is a 800 mÂ² Supermarket which is located in Ghana (all year Cooling).
But I cant find a way to calculate theÂ Part Load Fraction Correlation Curve.

Thank you for your help.Â
Kind regards