Martin Griffith

Thanks John, from the next version out this week, models opened in older versions will still lose the Utilization Factor, but the total heat will be adjusted.

Hi John, Very strange. Is there a chance that the file was saved in a version earlier than 5.4.3.3 after you sent it? If the file was opened and saved in a version earlier than 5.4.3.3, then opened again in version 5.4.4.0, then the Utilization Factors would all reset to 1 and that would explain what you've shown. In this way the Utilization Factors are not backwards compatible, we might have to do something about that. However, you say they are the same file and indeed I can see the Utilization Factors are the same in the last 2 images. So it's difficult to see how the results would be different. So I would get you to verify that the files are indeed the same (and the images shown above are from the same file) and have at no point been saved in an earlier version. Otherwise, if possible, I'd ask that you send us the file for debugging, which we would treat confidentially, but understand if this is not possible. If the problem continues, I would suggest you both upgrade to version 5.4.4.3 here: https://ventsim.com/download/minor-releases/ , or both reinstall version 5.4.4.0 from here: https://ventsim.com/download/currentdownloads/ . Then please let me know how it goes.

Hi John, there is a new version of Ventsim, 5.4.4.3, available here: https://ventsim.com/download/minor-releases/ This should remove the problems you originally reported. In this latest version, if you save your file while the Stage Lock is on, the model will be re-StageLocked after the save is complete. However, when the stage is unlocked at the time you save, there will be no report of airways that have changed, as there is if you unlock the stage yourself the normal way. When you later unlock the stage yourself, the message showing changes will only show changes going back to when you saved. We want to think more about this and improve it in a future version. Will keep you posted.

Hi John, I'll have a look at this today. A problem we have is that we have to unlock the stage to save the model or to create a new stage. We introduced code to re-lock the stage afterwards (rather than leaving it to the user to remember), but it appears to be causing problems here. Will keep you posted.

Hi Andrzej, This error is probably due to an error made building the model that the Pumpsim error reporting hasn't been able to identify. In these circumstances, you can send us the model and we will work out what is going wrong. We can fix it for you and then perhaps add a new error message so that the problem is more easily resolved in the future. Send us the model at ventsim.support@howden.com Otherwise, you can save your model and then start removing sections of it and testing, to try to detect what component of the model is causing the problem. But if it is not quickly apparent, then please contact us at the support email.

Hi, Thank you for the suggestion. Up until now, to simulate rainfall entering the mine in Pumpsim, we set a fixed flow. This means that you need to calculate the flow rate of water entering yourself. Are you imagining a calculator which calculates the rate for you?

Hi Xiao, We've just released a new version of Ventsim DESIGN, version 5.4.4.1, which has this strange behaviour on the gradient field fixed. You can find the new version here: https://ventsim.com/download/minor-releases/ Thanks for getting in contact, please let us know if you have any issues.

Hi Xiao, Thanks for your message. The behaviour when you change from Up to Down is strange, we will investigate that and fix it in a new version. However, it is important to remember that airways do not have a direction, unless they have a fixed flow or fan in them. For open airways, the direction of the flow is determined by the Air Simulation. If you do want to reverse the direction of a vertical airway, it is probably better to use the Reverse Tool, rather than use the Gradient property. Nevertheless, I will fix the strange behaviour and post here again when the new version is available.

There is some further discussion in the Ventsim manual about the NO2:NOx ratio setting: "Diesel exhaust gas and particulate matter emissions are normally quoted by regulatory agencies in terms of grams produced per kW engine output per hour (g/kWh). Engine emission standards have been improved over time. For example, a Tier 3 Diesel engine may have an Oxides of Nitrogen (NOx) output of 9.2 g/kWh and CO 3.5 and PM 0.12, while a Tier 4 Diesel engine has a considerably reduced NOx requirement of only 0.4 g/kWh NOx. A useful source of information on engine output is available from the EPA United States Webpage. A complicating part of measuring and modelling NOx gases is that this is a composite of 7 different forms of nitrogen / oxygen molecules. The main health concern is the NO2 component which has a limit for exposure of around 2- 3ppm, however the presence of NO2 is highly dependent of the presence of Ozone (O3) which is responsible for much of the formation of NO2 gas from NOx. Typically in urban environments, the ratio of NO2/NOx may be between Chapter 22 Tier Standards - Gas Emissions 10% and 30%, however in underground mining, away from the atmosphere and sunlight, the ratio may drop to only 2%. To provide an indicative NO2 value for modelling and design improvement purpose, VentSim assumes a ratio of 5%, however this is highly subjective and should not be used for designing critical airflows or diesel equipment calculations without calibration with measured results. The ratio can be adjusted in the VentSim settings – simulation > Diesel. settings – simulation > Diesel. http://www.atmos-chem-phys-discuss.net/5/12723/2005/acpd-5-12723-2005.pdf "

Hi Alex, Thank you for your post, I've been investigating. It took me awhile but I think much of the problem comes about here because the fixed flow in the gas part of the model is not Q = 0.1 m3/s, it's in fact 0.13 m3/s. This is an easy mistake to make when dealing with smaller than usual numbers. To fix it, go to Settings | Units, click on Contaminants PPM and Quantity and increase the number of decimal places. Further to this, I think there is some inconsistency between yourself and Ventsim about how concentrations are converted between mg/m3 and PPM. In Ventsim Diesel Simulation, only the CO, NOx and CO2 products are made (the three yield rates available in the Heat, Moisture, Diesel Presets), then a factor of 5% is used to calculate the fraction of NO2 in NOx. From your measurements you have a much higher ratio of NO2:NOx than 5%. You can change this setting in Settings | Simulation | Diesel | DieselNO2NOxratio. From your measured data, you want about 72%. I've attached a revised model (which makes the changes above) which gets the 2 simulation methods to agree. I've also attached a spreadsheet which shows how I went from the measured values in mg/m3 to PPM. If there is something about this that you don't agree with, or another way to calculate the concentrations, please let us know and we can discuss further. dieseldata.xlsx newDiesel.vsm

You could try setting the shock as Auto High, this should calculate the shock as a function of the 90 degree turn and of the change of area, so should come out greater than 1, Otherwise, the flow will go out there if that is the path of least resistance; so it would pay to have a think about if there is any flow resistance in the shaft that you haven't account for in the model.

Hi Kevin, probably the easiest way to finetune, would be to add a custom shock loss to the shaft, on the first tab of the Edit box. This custom shock loss would account for the change of direction of flow needed for air to flow through the exit and for the change in area. This will increase the resistance in the shaft, reducing the flow out of it.

We've just released Ventsim DESIGN 5.4.4.0. You may be prompted to upgrade the next time you open Ventsim. You can also download the installer directly from our website: https://ventsim.com/download/currentdownloads/ Among many bug fixes and minor improvements, the following is a list of features you might find useful. Thank you to everyone who has logged issues on the forum and sent us emails though the support email, we're very appreciative. Many of the improvements we make to Ventsim come from users getting in contact with us about what they'd like to see. So if you have any problems with anything or have feedback or suggestions of what you'd like to see in Ventsim, please get in contact! Add Howden Fan We’ve added a new feature with which you can directly look up a database of Howden Fans. On the Fan database form, just click the Add Howden Fan and you have access to dozens of fan curves. We’ll be adding more soon. Convert To Overpass Many users have been making use of the new Construct Overpass Tool. One request we’ve had is for an option to convert an existing overpass intersection to an overpass. We’ve now added this option below the existing option. Just select the airway to convert and click on Convert to Overpass. Orientation Axis We’ve added a standard CAD feature to the view in Ventsim, some orientation arrows. These aren’t on automatically though. Go to Settings | Graphics | Rendering | Show the Orientation Arrows and switch to Yes to show them. Export All Monitor Data We introduced an option to Export All Monitor Data at once. This will put on the clipboard data from every Dynamic Monitor in your model. You’ll see the data format if you paste it into Excel. Let us know if this is useful to you or if you’d want a different format to the data. Visibility Manager Layout Some users like to have the Visibility Manager open all the time. Now you can customize its shape, depending on how you like to display it. Underground Fan Shock Loss – Automatic option For fans at the surface, Ventsim automatically handles shock loss from the fan discharge (using fan discharge area, evase), but one question that has been coming up is how Ventsim handles shock loss from underground fans installed in bulkheads. The answer is that this is not automatically handled by Ventsim. If you want to consider this shock loss, it’s tricky to add. With this version we’ve added an option to automatically add the shock loss from underground fans, calculating it from the fan discharge area and the area of the airway the fan is venting into. To enable it, check the box on the Fans information page in the Fan Database. Any shock added will be viewable in the Fan Info box on the Edit Box as Fan Losses. Stage Graph From the Edit Box, go to Tools | Open Stage Graph, to generate a graph of 2 parameters on an airway across the stages. Utilisation Factor The Heat, Moisture and Diesel Presets now have an inbuilt Utilisation Factor you can edit. This means that you can enter, for example, the maximum power of a truck and directly enter your utilisation factor, instead of accounting for it directly in the truck power and noting it in the title. (Alternatively, leave it at 1 if you prefer to keep using it as you are!) Activity Track Graphics If you’re a fan of using lots of Activity Tracks and Stages in your model, then you’ve probably seen a few weird things happen with the display of the ribbons representing the Tracks. We’ve fixed them now, so that the offset of the Track with its airways is based on the visible airways, so ribbons should always appear above the airways.

Hi Roy, there are two settings Size Icons and Maximum Size Icons. Size Icons relates to the value on the slider in Scale Manager. You need to adjust Maximum Size Icons. This is a bit confusing. What we will do in the next version is, if you adjust Size Icons in the settings to a value greater than the Maximum Size Icons settings, you will be prompted about whether you want the maximum adjusted as well.

Hi DJL, Sorry you're having a problem. Could you please email me at ventsim.support@howden.com, telling us your license number and which version (Help | About) of the software you are using and we will work out what is happening. Martin

There has been a fair bit of work on the Caving Air Blast simulation since the last update given here. Now hte form has more options and output. You can play with the simulation timestep (which might be important if you're dealing with a collapsing stope or a sub-level caving event) and you can choose whether you want seals to fail during your simulation, or just to give warnings. Additionally, there is now a graph showing the variation over time of the cave pressure and the air velocity in each cave connections. Let us know of any experience or feedback you have for the tool.

Hi Ariexi, Exposed water surfaces will affect the Heat Simulation; however in a steady-state sense any puddle of water will evaporate with time. So to include heat and moisture from exposed water surfaces in the Heat Simulation, it only makes sense if there is a flow of water. You have the option of creating waterways in Ventsim, where you specify the flow rate, temperature and dimension of exposed water. There is a description of this feature on the forum: Any questions please let us know.

Hi Roy, Seems to be working alright for me. What version are you using (Help | About)? The fix we made for this is only available from version 5.4.3.3 onwards. Is it possible you've installed the latest official release 5.4.3.0? If so, you will need to install the latest patch from here: https://ventsim.com/download/minor-releases/

Hi Felipe, We don't have that reference, but I think it's probably the same. Pumpsim uses the equation for slow-valve closure for incompressible flow, given at the following Wikipedia page: https://en.wikipedia.org/wiki/Water_hammer#Slow_valve_closure;_incompressible_fluid The safety factor of 5 is used. Any suggestions or feedback you have on this is welcome.

If they are two separate doors, then probably best to split the airway and add the appropriate resistance to each. Use the Insert Node tool (circled in red) to click on an airway and split it. Then add the appropriate resistance to each.

Hi Martin, If a portion of the airway is obstructed by water on the ground, then probably the most straightforward way to represent this would be simply to add an obstruction to the airway. On the Edit form, you can add an Obstruct Area; enter in the cross-sectional area of the water obstruction and Ventsim will adjust the resistance of the airway to account for the reduced area. If an area is fully flooded, you can represent this by obstructing the entirety of the airway, or alternatively setting a Resistance Type as Blocked.

Hi Roy Thanks, we've had multiple requests for such a feature. We are working on it to add to a future version of Ventsim. Will keep you posted.

HI John, I can't find anything online. You may have to contact or visit a library directly. The link below seems good for searching for locations with the journal. https://www.worldcat.org/title/journal-of-the-chemical-metallurgical-mining-society-of-south-africa/oclc/2395223

Thanks Calen, this has been done in the new version of Ventsim available here: https://ventsim.com/download/minor-releases/ Thank you for getting in touch.

Hi Calen, the new version is available with this fixed: https://ventsim.com/download/minor-releases/ Thanks and let us know if you have anymore problems.