tdh and effects of bends
Posted: Sun Sep 19, 2010 8:06 pm
Hi all,
As part of my pond design for next year I'm currently looking at the returns to the pond. I plan on using an airlift from the last filtration section into a small bay/sump from which there will then be 4 gravity return pipes into the pond itself. As I'd like to return these 4 pipes each to a corner, so that they all contribute to a general circular flow, I've recognised that pipe diameter, flowrate and bends will all contribute to the tdh restriction on each pipe run and I want to avoid creating "dead" flow in one any individual pipe. I have looked at calculations for tdh and, allowing for different pipe sizes (and therefore the proportion of total flow they can take) and their length and have come up with a solution that has each pipe's tdh ending up within 50% of each other. Not bad, I thought!
However this doesn't take into account the effect of bends - the 4 runs will have either 1,2 or 3 90 degree bends. Some but not all of these can be replaced by 90 deg. curved sections or sweeps rather than bends per se, but I wanted to ask if anyone knows what sort of effects these bends would actually have on tdh?
There are some (horrificly
) complex formulae online to work them out but if someone has some simpler ideas I'd be very grateful! Is their effect minimal by comparison??
Cheers, Mark
As part of my pond design for next year I'm currently looking at the returns to the pond. I plan on using an airlift from the last filtration section into a small bay/sump from which there will then be 4 gravity return pipes into the pond itself. As I'd like to return these 4 pipes each to a corner, so that they all contribute to a general circular flow, I've recognised that pipe diameter, flowrate and bends will all contribute to the tdh restriction on each pipe run and I want to avoid creating "dead" flow in one any individual pipe. I have looked at calculations for tdh and, allowing for different pipe sizes (and therefore the proportion of total flow they can take) and their length and have come up with a solution that has each pipe's tdh ending up within 50% of each other. Not bad, I thought!
However this doesn't take into account the effect of bends - the 4 runs will have either 1,2 or 3 90 degree bends. Some but not all of these can be replaced by 90 deg. curved sections or sweeps rather than bends per se, but I wanted to ask if anyone knows what sort of effects these bends would actually have on tdh?
There are some (horrificly
) complex formulae online to work them out but if someone has some simpler ideas I'd be very grateful! Is their effect minimal by comparison??Cheers, Mark