KANN
Mechanical
- Sep 17, 2002
- 63
At what depth does the fluid level in a pipe produce waves resulting in slug flow? It seems to me that a thin film of fluid on the bottom of a pipe can not result in wave formation. But for a given high velocity at some point there is enough fluid (liquid hold-up, void fraction) to produce a "dangerous wave". Can a fluid depth of 1/4 inch produce a wave higher that twice that depth? Does the fluid depth, need to approach 1/2 the pipe diameter for slug flow to be a possibility? The occurance of a wave producing slug flow would seem also to depend on the length of the pipeline, shallow depths could present more slugging behavior as the length of the pipeline increases I would suppose.
Example 1: Steam distribution pipeline, 12 inch S40 pipe, with 125 psig saturated steam, good quality (above 90%), pipe sloped 1" in 20 ft down in the direction of flow (co-current two-phase flow), drips spaced every 500 ft (on the long side, but not uncommon), during warm-up the condensate rate is about 4.1 gpm (~60 fpm) at the dripleg, the condensate depth is about 1/2 inch, the steam flow is near maximum and at 12-15,000 fpm velocity. At running load about 0.08 gpm (17 fpm) and condensate depth of 3/32 inch.
Will slug flow be a possibility? What wave height could be generated? Will the outcome be some small waves which crest and disperse more moisture into the steam?
Example 2: Same as above, but now the slope is up in the direction of flow and we have counter-current flow. What happens in terms of slugging, waves, moisure level?
My understanding is that the flow regime is not annular given the low fluid volume and the relatively low velocity for multiphase flow. So, we are probably dealing with stratified smooth, stratified wavy, slug, and dispersed regimes and transitions.
I've found some help through papers by Sze-Foo Chien, E&P Technology Div., Texaco, published by SPE, in his study of wet-steam flow regimes in horizontal pipes. Unfortunately these works do not seem to address high quality steam with low liquid hold-up.
I've been chewing on these nuts for a while, and would like to get them as digested as possible...
Example 1: Steam distribution pipeline, 12 inch S40 pipe, with 125 psig saturated steam, good quality (above 90%), pipe sloped 1" in 20 ft down in the direction of flow (co-current two-phase flow), drips spaced every 500 ft (on the long side, but not uncommon), during warm-up the condensate rate is about 4.1 gpm (~60 fpm) at the dripleg, the condensate depth is about 1/2 inch, the steam flow is near maximum and at 12-15,000 fpm velocity. At running load about 0.08 gpm (17 fpm) and condensate depth of 3/32 inch.
Will slug flow be a possibility? What wave height could be generated? Will the outcome be some small waves which crest and disperse more moisture into the steam?
Example 2: Same as above, but now the slope is up in the direction of flow and we have counter-current flow. What happens in terms of slugging, waves, moisure level?
My understanding is that the flow regime is not annular given the low fluid volume and the relatively low velocity for multiphase flow. So, we are probably dealing with stratified smooth, stratified wavy, slug, and dispersed regimes and transitions.
I've found some help through papers by Sze-Foo Chien, E&P Technology Div., Texaco, published by SPE, in his study of wet-steam flow regimes in horizontal pipes. Unfortunately these works do not seem to address high quality steam with low liquid hold-up.
I've been chewing on these nuts for a while, and would like to get them as digested as possible...
