Martin Griffith

Hi Ivan, 

The order you select the airways on the track has no effect on the track's direction (or rather if it has an effect, it is a random effect). 

If you want to specify the direction of the track, add all the airways. Then move your view so that you can see the airway at which you want to begin the track. Then click the button "Set start" on the Activity Track form. Then click on the airway at the track start. The track will now begin from this airway and the direction is set. Vehicles will enter the track here. 

If you have selected "Bi-directional" option, then the vehicles will run the length of the track and then come back again along the same length. If you leave "Bi-directional" unchecked then the vehicles will exit the other end of the track and reenter at the start.

If you want to check where your track begins, then click on "Go to start" and the viewer will zoom to the beginning of the track.  

Hi Ivan, 

This warning indicates that the airways associated with the warning have a Date Mined setting which is further into the future than the year specified in Settings | Simulation | Environment | Current Year.

If you set a Date Mined value on your airway, then each Heat Simulation, Ventsim will calculate the age of the airway based on the difference between the Current Year setting and the Date Mined value. If the Current Year is earlier than the Date Mined, this age is negative and Ventsim throws the warning. 

So the fix is to make sure the Current Year setting is correct and the Date Mined setting on the airway is correct. You can find the Date Mined property on the Heat Tab of the Airway Edit Box.

Hope this helps.

Hi Kelvin, 

If you click on the error message, zoom to the airway, click on it with the Edit tool and select close end, that should fix it. The Close End option is retained and doesn't have any effect if the airway is connected at both ends.

Hi Robin, 

Correct you can import DXF files into Ventsim. Typically, for mine ventilation models, these DXF's are generated by a mine planning software, such as Deswik or Datamine; but DXF is a common format, so there are lots of softwares that can generate them (including Ventsim).

In Ventsim, a reference graphic can be used to represent just about anything, including surface topography, ore-bodies, stopes, airway centrelines....

Another option is to alter the Ventsim file yourself. If you save the Ventsim file as a text file, you can open it in Excel and do some conversions yourself. If you need a hand with this send us an email at ventsim.support@howden.com.

Hi Matthew, 

Sorry you've had this problem. From the Ventsim perspective, all Ventsim files are saved in SI units. If you are using Ventsim in Imperial units, the unit conversion is happening only at the user interface level. Therefore the file exported from Deswik must be in SI units. 

I don't know how to do this in Deswik, it's more a question for them. I imagine you need to convert your Deswik model to SI units and then export. Once you have loaded your Ventsim model in Ventsim, you can change the units to Imperial in the Unit Settings.

Let us know how you go. 

Hi David, 

Natural ventilation pressure is calculated on each airway according to the difference in air density between the air in an airway and the air at the same elevation outside the mine. You can turn this on with the Natural Ventilation Pressure option in the settings.

The density in the mine is highly dependent on the heat, therefore to have a simulation using natural ventilation pressure, then you need to have a properly configured Heat Simulation. To properly set up a Heat Simulation, you need to carefully configure your Environment Settings and make sure Heat sources in the mine are included and correctly set up. 

There are a few threads on the forum around setting up a Heat Simulation: 

It would also be worth checking out the Heat webinar on our website: https://ventsim.com/webinars/

What is important is that the Surface Datum of MineGrid setting corresponds to the Z coordinate in your model at which the surface barometric pressure was measured. 

To check this, after you have set up your Heat Simulation, if you check the Barometric Pressure in your model at the elevation you entered for Surface Datum of Minegrid, you should get the Surface Barometric Pressure. Example below:

Hi Xiao, 

Thanks for your message. 

The surface elevation above sealevel and the reference barometric pressure are linked, so if you change one, then the other will update. This is hard-coded in Ventsim to represent standard relation between air pressure and elevation. But this can vary locally (and seasonally) as it seems to at your site.

The barometric pressure is the important one. I would advise that you set the correct barometric pressure and then ignore the elevation above sealevel. The elevation above sealevel is only used as a reference in the settings, as a way to calculate the barometric pressure and to calculate the airway elevation above sealevel on the Info tab of the Edit Box. 

So for this problem, set the barometric pressure and ignore the resulting elevation above sealevel. And we will have a think about how to better handle this in the settings. 

Hi, 

The new version is now available on the website, version 5.4.7.3: https://ventsim.com/download/minor-releases/

Please install and get back to us with any problem. 

Apologies again and thank you for getting in touch. 

Hi,

Thanks for the message. Apologies, this looks like a bug in the addition of the diesel and sensible heat sources on the tracked airways. We are putting out a patch later today, we will try to fix this in that version. 

For now, to get around it, place the heat source for the secondary fans on the airways (via the Heat tab of the Edit Box) rather than on the track. 

A couple of things to note, if you have fans included in your model, then Ventsim will automatically add the heat from the fan in the Heat Simulation. You would only add heat in this way if you weren't including the secondary fans in your Air Simulation model.

Thanks again, I will post here again when the fix is available.

Hi, 

When you run a model, you need to tell Ventsim if an unconnected airway is closed or is open to surface. The no entry connection indicates that you have unconnected airways that you haven't specified. Feel free to email us a screenshot or your model to ventsim.support@howden.com

Martin

Hi, 

A piston pump is a positive displacement pump, so there are a few options. 

Often setting a fix flow is sufficient for such pumps. You can start there. 

You can also define positive displacement pumps in the Pump database, as in the image below. 

If your pump has a pump curve, you can enter it as a standard pump on the first tab of the Pump database. But there is also an option there to mark the pump as positive displacement, whereby the pump pressure will not change depending on the pump PRM

There is a rundown of paste fill modelling in this thread: 

Hi Roy, 

We don't have an exact copy of that button in the new Edit Box. 

We added a tool called Apply to Specific Stages, in the Tools menu of the Edit Box. You can use this in a similar way. If you want to make an edit to some airways that only apply to the current stage, without affecting the other stages, you can make the edit in the Edit Box, then instead of clicking the Apply button, go to Tools | Apply to Specific Stages and apply only to the current stage. The airways will now be unique to the current stage (with the new changes you've made). 

Does this do what you want? 

We have a plan soon to add the Apply to Specific Stages button as a dropdown option to the main Apply button. 

Hi Sam, 

Thanks for starting the discussion. I'm not aware of any research papers on this, although I know there are some network fluid solvers that incorporate inertia. 

We've tried at looking at this in Ventsim a few times, incorporating the inertia of the ventilation into the simulation is something we'd like to do somehow in Ventsim, but we haven't managed it yet. 

One approach you can do is to make an estimate of the total kinetic energy of the airflow in the mine at the moment that you turn the fans off. You can then make an estimate of the resistance of the mine and calculate the rate of energy loss to friction and to surface exhaust as a function of flow rate. You can get a rough estimate this way of the time to go to zero flow. I did this once a few years ago, I'll try to find it in my notes and post it here. 

But this doesn't incorporate natural ventilation pressure resulting from heat and density changes. Again, you can do these things roughly; you can simulate the steady state condition where fans are off and calculate the time to reach that total energy state, rather than an energy state of zero.

Another factor is the change in rock strata heat transfer. This heat transfer depends strongly on airflow rates. If you change the airflow rate, the heat transfer will change; but rock strata can take a very long time to reach steady-state, probably much longer than the airflows. If you switched off all ventilation, it could take a long time for the rock walls to heat back up to the VRT, and therefore to reach a steady state.

Hi John, thank you for the bug report, much appreciated, we will fix that in the next version. 

Hi Roy, 

This appears to be an issue updating the Friction Factor dropdown on the old Edit Box after re-sorting. I will try to fix this for the next version and will let you know when it's available. 

In the meantime, I think you've found how to get around the problem (restart Ventsim). You could also switch to the new Edit Box which doesn't seem to have this problem.

If you are worried about what friction factor is being used by the simulation, you can change the property to Attributes | Friction Factor. The value shown in the viewer on the airway is the value being used in the simulation. 

I'll post here again when a fix for this available. 

more information here: 

Just a note on the above, we have now added the BEV heat source to the Heat Presets, as Craig foreshadowed at the end of the 5th paragraph of his post. This means that following the example above, for a total CPO of a truck of 500 kW with 25% utilisation, you can enter this as follows in the Heat Presets: 

Then there are 2 settings in Settings | Simulation | Heat which set the electric vehicle efficiency and also set the breakup of the vehicle heat output into sensible and latent heat (default setting is 50:50) as explained in the 6th paragraph of Craig's post.  

Any feedback, please let us know!

Hi Adrian, 

That sounds like a big model. Investigating, I suspect the graphics updating during the build process is slowing it down considerably. 

I believe I have a fix for it. I am uploading a test version of Ventsim which should do this much quicker. I have your email, I will email you a link. 

Martin

Hi, 

It looks like that is a PDF file. Ventsim can import a PDF file as a graphical reference, but you can't open it as a Ventsim file. 

Or is this a Ventsim file that you changed the file extension on? 

Hi Renier, 

Thank you for your message.

LiveView has been replaced now with the base level of Ventsim CONTROL, which gives some improvements over LiveView. If you want to know more please email us at ventsim@howden.com and we help you get set up. Please let us know how you are/were using LiveView and we will work out a solution for you.

Hi Alfonso, 

Sorry it didn't work for you. I think it best if you send us the file and we will work out what is going wrong; we haven't seen a .inp file in a while. If you email me at ventsim.support@howden.com we can work it out. If the file is > 10mb you can also send it to me through this forum's direct messaging feature. 

Martin

Hi Prag, 

The flow is calculated using the Darcy Weisbach equation, with the density calculated with the Ideal Gas law. The temperature, specific heat and the gas constant need to be set by the user. Pumpsim cant calcualte these for mixtures. The users needs to configure the mixtures themselves and determine the properties themselves. Including gas mixing in the Pumpsim solver is something we are working on for the future. 

The Free Air Quantity is the flow rate, but with the gas at standard density, rather than the local density in the pipe. This is sometimes useful with compressible gas flows where the quantity is changing along the pipe with the change in pressure and density. The Free Air Quantity is similar to a mass flow, it will only change where flows meet at an intersection, so can be more "readable".

Hi Prag, 

You can look at the property Flow | Free Air Quantity instead of Flow | Quantity. This will give the flow rate standardised to the set standard pressure.

You can set the temperature and surface pressure in the settings