Martin Griffith

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

Hi, Thanks for your message. Please email us at ventsim@howden.com and we should be able to help you with this request.

Since the release of Ventsim 5.4 we've been busy adding new features to help with your underground ventilation modelling. On top of what came out in the original Ventsim 5.4 release (https://ventsim.com/2020/02/18/whats-new-in-ventsim-5-4/) the below is a list of what's new: Heaters & Coolers Instead of setting a heating or cooling source in your airway, you can define Heaters and Coolers with target temperatures. This works in a similar way to using a fixed temperature, but provides additional information on energy, water and fuel use, as well has having some really cool interactions with the Annual Thermal Flywheel Simulation. Just recently we've added the ability to set a maximum capacity to a cooler, making it behave more realistically. Parallel Fan Stall Predictor Use this tool to scan over your model and assess the risk of stalled fans in parallel configurations. This helps to deal with the problem where in parallel fan configurations, one of more fans will be in stall, while the others are operating normally. Traffic Features We've added new ways to deal with the number of vehicles on an Activity Track varying throughout the day. You can now set a time to a stage, and have a different amount of traffic every hour of the day. We've also improved the UI around setting a track's starting location. Advanced Message Boxes We've seen lots of models adorned with many detailed and bespoke Advanced Message Boxes, showing simulation data in new and useful ways. If you want a particular piece of information from your model, there's probably a way you can do it with the Message Box. As users have provided feedback we've added new properties as well, so just ask if there is something you need. Also available are a number of new averaging techniques, which allow you to obtain more representative averages. For example, this message box below gives an average temperature, but weighted for flow and length, rather than each airway having equal weight. This example here tells you how many fans in a particular section of the mine you have on: Diesel Simulation: Fresh Air Surplus When you run a Diesel Simulation, Ventsim now calculates a new property Diesel | Air Surplus, which keeps a track of how much fresh air you have through the mine. This is often handled globally in the model, by summing the Diesel Power of all the machines in the mine and calculating a required air flow, generally following a regulation specifying a required airflow per kW of diesel power (often something around 0.06 (m3/s)/Kw). This property will calculate this locally. The fresh air consumed is calculated using the air flow requirement specified in the Diesel Settings, or adding a machine specific flow requirement in the Presets. If the Air Surplus drops below zero and you have a diesel machine in the area, you'll get a warning with your Diesel Simulation. Fan Identifier The Fan Identifier tool lets you keep track of individual fans, rather than just fan types. Set up your Fan Identifiers, and then assign them to airways. In the Fan Identifier, you can even keep fans that aren't being used. The tool will tell you the status of each fan, where it is, and will even let you control it from the Fan Identifier database. Auto-Regulators Auto-regulators are a new resistance option for an airway. They use the same Regulator presets as the regular Regulator option, but instead of setting the opening, you set the Target flow rate, and Ventsim works out the opening; much like a control regulator would do it. If the target airflow can't be achieved you'll get a warning which tells you how much you've missed the target by. For people use to using Fixed Flows with the Restrict Only option on, autoregulators are a great option, since they won't simulate a flow as if the regulator is adding pressure; instead, the regulator will just be fully open. Electric Vehicles In the Heat, Moisture, Diesel Presets, we've added an Electric Power column. This brings the Ventsim treatment of Electric Vehicles in line with how we treat Diesel Vehicles, namely by the (more readily available) motor output, rather than heat released. This also allows users to easily compare the use of Diesel and Electric vehicles in Ventsim. That's it for now, but you'll find many other smaller improvements in Ventsim 5.4 if you update to the latest version. As always, any questions, you can respond here or contact us at ventsim.support@howden.com. We rely a lot on your feedback to make the software better, so please tell us if there is something you would like to see in Ventsim.

Hi, I believe I've sent you an email from our support email regarding this model. The problem can be fixed by addressing the fixed lengths in the model. Let me know if you haven't received it. Martin

Hi Jorge, Sorry you've had this problem. Could you please give me some more details? Is there an error message that appears? If so, can you send me a screenshot? Are you using the Convert Centreline tool, or are you doing the conversion on the DXF import window? One thing to look out for: check if the count of the number of pipes at the bottom of the Pumpsim window goes up after you use the tool. If the count goes up, but you can't see the pipes, it may be because they are being created in a Primary or Secondary Layer, or Level, that it currently not visible. Right-click | Show All should make them appear. We are looking to launch Pumpsim 4 early next year. This will be a big change from Pumpsim 3, bringing with it many of the changes that you've identified in Ventsim that are needed in Pumpsim, and more. You will be sure to hear about its availability, either here on the forum, or through messages in the software.