I have attached an image of a square throat elbow whose aspect ratio is around 1:8. (Width 32in, height 4in). Contractor has used 2 of these elbows to cross a beam. and there is some length of straight duct section of these dimensions too (around 6-7ft). i want to know HOW MUCH bad it is? As per my rough calculations the duct friction loss came out to be 1.53, equivalent dia 13in and equivalent length 39ft. However, i need someone more expert in design to vet these parameters as standard charts and tables are not telling much beyond aspect ratio of 1:4. After that, I am a bit confused on how to interpret these parameters to convert these into simple pressure drop loss, cfm loss, AHU energy consumption increase or any other parameter which I dont know. Can somebody help me through this in order to quantify the damage this elbow will bring?