HVAC Modelling Open Studio

asked 2017-10-04 04:30:21 -0500

vkalfou's avatar

updated 2017-10-05 02:35:24 -0500

I'm pretty new to OpenStudio modelling and I do have a question.

I am currently modelling the cooling system of a Data Room which is pretty different than conventional HVACs. In my case cooling is divided into various stages. The unit shall be equipped with an air-to-air epoxy coated aluminium plate heat exchanger. Furthermore, the Unit shall be equipped with an evaporative system consisting of:

  • A rack with several nozzles placed at the exit of the heat exchanger, on the outdoor air (process) side, which shall spray water on the surface of the heat exchanger creating a thin water film, which through evaporation shall maximize the cooling effect.

  • A submersible stainless steel recirculating pump for the rack, able to provide water to the rack at a maximum pressure of 3bar. The pump shall suck water from the Unit’s drain pan.

  • A UV lamp, integrated into the Unit and installed on the recirculating pump discharge to reduce bacteria content.

  • A droplet separator, which shall be placed on the outdoor air (process) outlet, between the heat exchanger and the fans.

Last but not least the Unit shal be equipped with a direct expansion (DX) back-up system comprised of two circuits with modulating capacity.

The unit will operate in different modes depending on the external air conditions:

  • Dry mode: During the cold season (winter operation), IT Room return air shall be cooled down, leveraging the heat exchange process with outdoor cold air. There shall not be need to run the evaporative system and the fans speed shall be controlled by the outdoor air temperature.

  • Wet mode: During the warm season (summer operation) the evaporative system shall run in order to saturate the air. This shall enable the Unit to cool the IT Room return air even with high outdoor air temperature.

  • DX Integration mode: In the case of extreme external conditions, the direct expansion (DX) system shall provide additional cooling.

At the moment I've added an Air-to-Air module, an Evaporative Cooler, a Direct Expansion (DX:SingleSpeed) and a fan and the model doesn't seem to be working properly in terms of energy efficiency. I suppose I haven't managed to model the three operating modes.

So, my question is how can I model the three different operating modes? Note that I do have the operating curves of the unit.

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@vkalfou did you have any luck getting this modeled and operating as expected? We're trying to model a very similar system in EnergyPlus and would love to hear about about the approach you ended up going with.

willyJohan's avatar willyJohan  ( 2018-06-08 15:56:52 -0500 )edit