Process water heat reclaim modeling problem

asked 2020-01-23 13:40:28 -0500

Frederic Leveille gravatar image

updated 2020-01-24 08:04:36 -0500

I am having difficulties modeling a heat reclaim for a process water loop. I am currently modeling a research site with many growth cabinets (for plant cultivation) using OpenStudio V2.8. Many of these cabinets are water cooled with a process water loop. Below is a schematic of the loop as it is operated.

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The desired supply temperature for the process water loop is around 24°C and the return temperature is often around 30°C. The first step in the cooling of the loop is to try to reclaim some heat through a heat exchanger that will heat a glycol loop used for preheating coils in AHUs. The supply and return temperature of this glycol loop are 35°C and 20°C respectively. The heat reclaim Hx is located on the return of both loop with a bypass on each side. When heating is needed, flow is admitted in the Hx. If the output temperature of the Hx on the process loop side is still higher than 24°C, then the second cooling step is the cooling tower. If the temperature at the output of the cooling tower is still higher than 24°C, then the third cooling step is another Hx that is connected to a chiller. Each of these cooling steps has a bypass for when they are not needed or can’t be applied (No heating need in the heat reclaim for example). One problem I’m having is that I don’t know if I can or how I can have multiple parallel equipment and bypass in series on the supply side of the loop. Maybe there is a workaround with SetpointManager and/or Load Distribution Scheme? The other problem I have is with theHeatExchanger:FluidToFluid. I would normally put it on both supply side of both loop since one is a cooling loop and the other is a heating loop. When I’m supplying cooling of one loop, I’m also supplying heating of the other at the same time. However, the E+ documentation is very clear that the Hx object must be on one supply side and one demand side of any two loops.

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I assume those Hx could have a HeatingSetpointOnOff and CoolingSetpointModulated control type.

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There is maybe a way to code everything with EMS but I’m not familiar with this tool. Is there a way to achieve what I'm trying to do within OS?

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