Luca Finardi

Vito, you can create a simple python script coupling the pressure increase in the vessel through the EOS and the power absorbed by the compressor and then integrate in discrete times to find the energy required. Here DWSIM can be of help in getting the thermodynamic properties and in the calculation of compressor power. Hope it helps. Luca

Hi Tanatip, if you enable the calculate Heat Exchange Profile, run the model and look at the Evaporator Q vs t profile (see screenshot) you see a temperature cross. Moreover this profile is always in co-current, regardless if a countercurrent flow direction is selected. I tried to chart the cold stream temperatures data in reverse order, but still a T cross appears. I am not sure whether this is a bug in the program due to phase change in the exchanger, but I suspect that the results could not be...

Hello Tanatip, I had a look to your ORC model ... I found something strange in the evaporator. The heat and temperature profiles have a temperature cross that I can't understand ... even changing the data in countercurrent configuration (apparently DWsim only makes the profile only in co-current) the cold stream becomes hotter that the hot stream ... Isn't there something wrong? Hope it helps. Luca

Hello! See attached model. Now it works, I added another recycle and made some other adjustments. With 2 simulatneous recycle blocks seems unstable, so my recommendation is to let them non-active and activate one at a time. Hope it helps. Luca

Hello Phakin, attached my deaerator model's attemp. It includes a cooler to simulate the steam condensing and an heater to simulate the condensate heating. The two exchangers are energy-linked so that the condensing steam transfers heat to the condensate. Finally the two streams are mixed together as boiler feedwater. A controller adjusts the amount of superheated steam in order to have the BFW at saturation point. A splitter simulates the vent from deaerator, here set at 2% of the inlet steam. As...

Hi Joe, if you want to include your feedwater heater in a thermodynamic model, you can simulate it with a cooler and an heater coupled through a specification block. You can either model as a single couple and set directly the temperature difference on the steam side or as two coupled cooler-heater if you want to have control of the degree of subcooling on the drain side. See the attached model with both options. Hope it helps. Luca

Looks that in rel 8.6.8 works.

Hello Daniel, I came across the same error pointed out in this post: the compressor model seems not to work when the Calculation Type is 'Performance Curves'. Checking the UnitOperations/Compressor.vb code, from line 436 there are several interpolations made by calling MathNet.Numerics.Interpolate.Linear. I presume there is something wrong here since the simulation error returned (The given array is too small. It must be at least 2 long) is the same I replicated passing a void array to MathNet.Numerics.Interpolate.Linear....