Rehan Khalid's profile - activity

I see. Ok I will look into that. Thank you for the help

I understand Sir. Comment followed and email sent highlighting the problem.

Sir, if you look at the output file, doing the above switches off the mass-flow rate within the zone, which causes CPU CPU/Fan power to go to zero and the PUE values to shoot up. This was not happening previously; however, then the evaporative cooler was not functioning properly.

Thank you Sir. I get your point and understand what I had been doing wrong.

Thank you Sir. That is good insight into the problem. I will explore further from here.

Thank you for offering the help Sir. I will email you the file.

The transient scheme pertains to how the exit air temperature is calculated. Currently EP calculates the exit air temperature using a steady-state equation: T_a_ex = T_a_in + (Q/m_dot*c_p_air)

We are calculating the exit air temperature taking into account the server thermal mass (capacitance and time constant, for which various empirical correlations have been developed), server temperature and the exit temperature at previous time steps.

We believe that the time constant should produce a lag in exit temperature and hence would affect the cooling load and demand. However, that is not to be.

Hi,

I am modeling a hybrid DX-Evaporative Cooler system with the location set to Phoenix Arizona. However, my evaporator turns off during the peak summer months of July and August, when the outdoor Dry-bulb is 42 deg. C and the wetbulb is around 22 C.

I have no limits on the operation of the evaporative cooler; however, the outdoor air controller is set to have a maximum of 27 C for the economizer mode and the OA mixing box inlet node is set to have a setpoint that varies between 15 and 35 deg C. Can anyone offer a possible explanation and a fix. I'd greatly appreciate the help.

I am trying to study the effect of mass flow rate and deltaT (input-output temperature difference) on the performance of IT equipment and data centers using two schemes, a steady-state one built into E+ and a transient scheme for servers developed experimentally. The goal is to characterize the difference in CRAC performance and mechanical PUE when comparing the two schemes. The cooling system used is DX Cooling (DXCoolingCoil:SingleSpeed).

However, what I have found is that there is no difference in facility total power, facility building power (quotient of which gives PUE), the CRAC power, DX cooling coil power and system flow rate when I implement the two schemes.

1) My understanding is that a higher deltaT and hence higher exit temperature would result in greater power savings in terms of the HVAC system but E+ does not report any difference in any of the above parameters.

2) Hard Sizing the DX coil to produce changes in mass flow rate and inlet air temperatures does not seem to work. Either errors are reported that there is a mismatch in sizing of various components or that zone temperatures are too high. Auto-sizing the coil (rated capacity, rated flow rate and SHR) seems to produce optimum results in terms of cooling system power consumed and PUE; however, that technique does not work with my transient scheme where E+ reports the supply side air flow rate to be around 2.8 kg/s and the ITE mass flow rate to be around 22kg/s, which does not make physical sense, even taking re-circulation into account.

Has anyone seen such a situation or can shed some light as to how to go about this and characterize the performance. Doing it experimentally is one thing but simulation should support those results. I would highly appreciate any insight into this situation.

Thank You Sir. Your reply from a previous post also helped in clearing out the issue, specifically copy energyplus.exe and energyplusapi.dll into the root directory folder where IDF editor is located, Thank you once again ! That helped me resolve the issue and solve my problem.

Hi,

I downloaded the source code and followed the instructions given on https://github.com/NREL/EnergyPlus.

If I use the "run without debugging" or the "debug" option from within Visual Studio, I get the following error: "Unable to start Program: C:\Users\Rehan\Documents\Github\EnergyPlus\Buildd\Debug\All-Build. Access is denied".

Secondly, point # 8 on the link given above says to "manually set the target to EP in visual studio". I am not able to do that. Maybe that is what is causing the issue.

My code builds in both debug and release mode but if I run it using EP launch as well, it does not respond to the changes I made. Rather follows the original installation that I have.

Can anyone suggest what may be happening and a possible fix to the issue.

Hi,

Can anyone here help me with getting started on how to access and get started with energyplus source code.

I want to add two actuators to the object ElectricEquipment:ITE:AirCooled, in order to control the mass flow rate and exit air temperature through the equipment. Currently, there is only one actuator available for controlling the power dissipated within the equipment.

Any help would be much appreciated.

Thank you for that answer, I appreciate it. Can you give me any guidelines on how to access the source code and make changes (to add an actuator). I would like to work with the source code from v8.4, which is available in C++. Thanks.

Hi,

I am trying to modify the "Server exit air temperature" as calculated by EnergyPlus. Basically EnergyPlus uses a steady-state equation to compute this temperature and I am trying to incorporate a transient scheme using EMS. The variable that I am trying to map for this purpose is "ITE Outlet Dry-Bulb Temperature". I have declared this as an EMS Sensor object and created the variable Taex for this purpose. However, no matter what I do, I cannot access this variable and modify its value using my code. I tried to use an EMS actuator but cannot find a suitable one that will control temperature. How can I accomplish this. Any help would be greatly appreciated.

Thank you for that help. I appreciate it !

I have created a user defined variable in EMS and want to manipulate it. How can I define its initial condition i.e. set the first value of the variable to be used by later timesteps.

My equation is: set Ts = aa@TrendValue Temp_s 1 + bb(@TrendValue Temp_a_in 1 +cc)

here Ts is the variable I created and am trying to calculate and Temp_s is the trend variable associated with it. The initial condition I want to specify is: Ts (1) = Tain (1) + deltaTss/effectiveness

aa, bb, cc and dd have been calculated using a subroutine.

I'd appreciate any help.

Answer deleted. I had already posted it as a comment. Thank you for pointing it out.

Thank You so much ! That worked ! I had already consulted those files before working on this.

However, I don't understand why my choice of variables does not work. Can you kindly explain.

Thank you once again !

Thank You so much ! That worked ! I had already consulted those files before working on this.

However, I don't understand why my choice of variables does not work. Can you kindly explain.

Thank you once again !

Hi, I am trying to control data center IT equipment using EMS in EnergyPlus. When I try to get the temperature of air at the server Inlet, Ta_in and the server power dissipation, Qs_dot, I get an error that unique key name for these output variables are not found. Here is what I am currently using:

EnergyManagementSystem:Sensor,
    Tain,                    !- Name
    Zone Equipment Inlet Node ,  !- Output:Variable or Output:Meter Index Key Name
    ITE Air Inlet Dry-Bulb Temperature;  !- Output:Variable or Output:Meter Name

EnergyManagementSystem:Sensor,
    Q_dot_s,                 !- Name
    Whole Building,          !- Output:Variable or Output:Meter Index Key Name
    ITE Total Heat Gain to Zone Rate;  !- Output:Variable or Output:Meter Name

The errors that I get are:

   **   ~~~   ** Severe  ** Invalid Output:Variable or Output:Meter Index Key Name =ZONE EQUIPMENT INLET NODE
   **   ~~~   ** For Output:Variable or Output:Meter = ITE AIR INLET DRY-BULB TEMPERATURE
   **   ~~~   ** Entered in EnergyManagementSystem:Sensor=TAIN
   **   ~~~   ** Unique Key Name not found.
   ** Severe  ** Invalid Output:Variable or Output:Meter Index Key Name =WHOLE BUILDING
   **   ~~~   ** For Output:Variable or Output:Meter = ITE TOTAL HEAT GAIN TO ZONE RATE
   **   ~~~   ** Entered in EnergyManagementSystem:Sensor=Q_DOT_S
   **   ~~~   ** Unique Key Name not found.

Can someone please help me identify what the unique key name should be for these. I have tried a bunch of combinations but none seem to work.

Thanks in advance.

Hi, I'm trying to model data centers and want to know how to incorporate a server's thermal mass within EP (thermal capacitance and effectiveness) and how does EP currently model ITE equipment. Thanks

No help available on thermal mass of electric equipment or ITE equipment. Closest is internal mass for interior partitions or maybe furniture.