Customer Posted April 5, 2018 Report Share Posted April 5, 2018 I have a question on how the heat release rate is calculated in the Fire module. I have a Mucker with 25% Diesel, 25% Rubber and 50% PVC rubber. The burning period is 50 minutes with exponent factor of 1.0, indicating a linear build up. The burning rate goes from zero to 5000 lb/hours. The graph shows a bi-linear trend. Is there any assumption in calculating the heat release rate? Link to comment Share on other sites More sharing options...
Craig Stewart Posted April 5, 2018 Report Share Posted April 5, 2018 If a fire in Ventsim becomes oxygen constrained (as in lack of available oxygen supply), Ventsim will automatically throttle and reduce the fire size. Picture 1 below shows the Heat Release Rate (HRR) of a fire in Ventsim which is not oxygen constrained. If oxygen levels fall below 15% then Ventsim will start to constrain the fire size by preventing the full specified amount from being burned. This is shown in picture 2 If oxygen levels fall below 5% then Ventsim will extinguish the fire until more oxygen flows over the fire zone. This can create a 'flaring' behaviour as shown in Picture 3. Examples of this flaring behaviour can be observed in underground fire experiments such as Swedish Fire Tunnel Experiments The % limits at which the fire becomes constrained can be changed or removed in the settings. Picture 1 : No oxygen restrictions Picture 2 : Oxygen falls to < 15% Picture 3 : Oxygen falls to <5% occasionally Link to comment Share on other sites More sharing options...
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