Hi Jon,
Sorry about my last few messages, they were sent from my phone, and I was at training when you called, I could hear you but you couldn't hear me!
I shall upload another latest one soon, I think the longer outlets were helping with said re circulation, although sometimes the corner ones' velocity vector seems to point downward.
I wanted to know about the resistances to try and force more extraction so the overall CO value doesn't get unreasonably high.
In reality? There is a mixture of Air/CO that is leaving the exhaust ports at an increased rate to what air is being pumped into the space.
Usually when we design systems for these sort of problems, we have deemed-to-satisfy conditions the car park must adhere to, usually this is by doing a calculation which yields the Carbon monoxide generation rate, and in-turn a Flow rate needed as exhaust from the space - This is the 93 000 (note that number is actually for a car park double the space). The flow rate in is a percentage of the airflow in, understanding that air isn't entering/leaving at the same rate or at least this is how the fans are sized up.
In this case, we have:
8730 g/h, or 2.12 L/s Carbon monoxide generation.
The exhaust that was calculated using the deemed to satisfy clauses is 93 000, this number is rather arbitrary, It should be half of this to exhaust the amount of CO desired. I'm working with the larger number to try and get this model to work.
In reality I guess it is hard to tell what each flow rate will ACTUALLY be, but the fans would be sized for 93 000 exhaust and 73 000 Supply, I have never been involved with commissioning these systems or anything so I'm not sure how close the installed flow rates are compared to the theoretical.
If what you mean by realistic flowrate is my CO generation, then 2.12 L/s is this value (that would be scalar of 1 I assume), some of the other other ones I have split into multiple inlets and just divided the scalar by 500, hence the total CO generation would be 1060.
In regards to the mass flow, how are we to assign a flow rate out of the system that ensures balance? we have too many unknowns, the equation being as follows:
x(73 000) + y(2.12) = FLOWRATE OUT(x + y)
note that the volume of the entire space I have calculated as 54 400, so just roughly, the max concentration would be (2.425g/544000) or 44ppm.
I have noticed the first iteration of the scalar reads a 80 or so ppm reading. Could this be right as an initial value?
In terms of mass flow, I thought we were going to assign the large flow inwards, and have pressure = 0 outlets only to ensure flow leaves the volume through these outlets.
When you say pulling air out, do you mean you assigned a flow rate leaving the system through the exhaust extrusions? Doesn't this mean that the mass balance isn't going to be balanced? Referring back to my equation with the unknowns. If you did have a flow rate out, how did you make sure it balanced? Would it be better to assign outlets as having a leaving flow (say, the exhaust flow rate of 93 000), and have the inlets as the pressure value instead? This way it will balance the flow at the inlets to whatever it needs to be (less than exhaust), and more importantly, would allow a fixed amount of exhaust to leave the system.
Hope to hear from you guys soon, thanks.
Jack.
