Understood the below links gives K-value for some of the fitting however, it doesn't show the assumed value for different default bends and tees . Please could you be able to post the k vale for the default connection fittings. i want to verify the pressure loss is correct and is inline with CIBSE guide C.
I'm afraid we don't have this data in a digestible form at present. For many fittings there isn't a single K-value but a range which can be based on diameter and in some cases selected by velocity, direction of flow etc. This makes the data complex and difficult to display in a meaningful way. For future software we re looking to display the K-value used directly in the software so every section can be evaluated.
Steve Brown | Technical Support Manager
Hi Steve, display the K-value in the output is important for ducting design. We are currently looking to apply different type of bends trying to reduce the system pressure loss for varies large ducting system. Without knowing what the K-value for fittings (short bend, long bend, mitre bend.. etc.) used in the calculation, it is not possible for us to optimise the pressure loss and design the ducting system. Also, it appears that Hevacomp does not have bends with vanes for us to choose. I've probably missed something. Is it possible to apply bends with vanes in Hevacomp calculation?
Thanks in advance for helping.
Hi Carmen, there are many bend types with vanes available in the software - if you go to Fittings > Default bends/tees you can find them as follows:
Alternatively, you can go to Fittings > Fix bend/tee:
Shane Regan | Senior Building Performance Support Engineer
Hi Shane, thanks for your swift response. Yes, sorry we noticed that vanes can be selected for the mitre bends. However, there is only one option for the short radius bend with single vane. Does the software have more options of vanes as in the following figure in CIBSE. Without the k factor allowance for the bends from the software we cannot tell if the bend we want to use is equivalent to what simulates in Hevacomp model. Can you help how we can dictate the k factor?
The options you mention are the only ones available. As Steve mentioned above, we do not have a breakdown of K-values for each bend in the software, as the software calculation method involves iteratively calculating the loss of section inclusive of all fittings in that section - a breakdown showing the contribution of each bend is not possible. However simple fittings losses can be found here.
If you wish to compare your hand calculations to the software then I would firstly advise inspecting all the fittings results for each section eg as in image below. An explanation of what is what can be found here.