Martin Griffith Posted March 1, 2019 Report Share Posted March 1, 2019 There are two ways to model jet fans in Ventsim. 1) The first way mimics what happens in some mines, where a ventilation engineer will re-purpose a spare fan as a jet fan, placing it in an airstream to provide an additional boost of pressure. Ventsim has a similar functionality, whereby an existing fan in your Fan Database can be switched from the default closed circuit configuration to a jet fan configuration. To do so, add the fan to an airway as you normally would. Then check the small box with the jet fan icon, located to the right of the Fan Model drop down box, indicated here by the red square. Click Apply, and your fan icon should turn from green to purple. You now have a jet fan in place. Ventsim works out the operating point of the re-purposed jet fan by finding the fan duty point corresponding to zero static pressure; this will be down the bottom right of your fan curve, typically in a region of very low efficiency. Since the fan is freestanding in the airstream, not in closed circuit, only the velocity pressure addition of the fan is possible. Several factors affect the calculated Induced Pressure; the velocity factor account for the loss from the difference in the airway air speed and the fan outlet velocity; the installation factor relates to the distance the jet fan is located from the wall (a jet stream running along a wall will lose more energy in wall friction than one placed away from a wall) 2) The second way to add a jet fan is designed more for when a purpose-built jet fan is being installed, with specified parameters. Go to your Fan database, and there is a second tab, called ‘Jet Fans’. Here, you can enter the jet fan, choosing to specify it by Thrust, Quantity or Velocity. You will also need to specify the diameter of the jet fan. The Fan to Ceiling distance will be used to calculate the installation factor. The air density field is similar to the density field for the normal fans, ie., it refers to the density at which the specifications of the fan were determined. The power consumption of the jet fan can be added too. If you place a fan created in this way into an airway you will again see a purple fan icon. There is no need to check the jet fan box on the edit form when using this method. If you’ve been using the jet fan feature, please let us know how you find it. And if you have any questions about jet fans, don't hesitate to ask! Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.