Pressure drop in fluid flowing between flat plates
Pressure drop in fluid flowing between flat plates
(OP)
Hello,
I was wondering if anyone can help. I'm looking for a formula to estimate the pressure drop in a fluid as it flows in the gap between two flat parallel plates.
I'm using a formula to calculate the velocity of a fluid as it flows between two parallel plates. This needs to know the change in pressure over distance, dP/dx.
At the start of the gap there is a 1 bar driving pressure. I've assumed that the pressure drop is 1 bar divided by the distance the fluid has travelled.
However this doesn't seem to agree with some CFX modelling and some experimental results.
Is there a better approximation for the pressure drop?
Thanks
George
I was wondering if anyone can help. I'm looking for a formula to estimate the pressure drop in a fluid as it flows in the gap between two flat parallel plates.
I'm using a formula to calculate the velocity of a fluid as it flows between two parallel plates. This needs to know the change in pressure over distance, dP/dx.
At the start of the gap there is a 1 bar driving pressure. I've assumed that the pressure drop is 1 bar divided by the distance the fluid has travelled.
However this doesn't seem to agree with some CFX modelling and some experimental results.
Is there a better approximation for the pressure drop?
Thanks
George





RE: Pressure drop in fluid flowing between flat plates
deltaP = f*L*rho*V^2/(Dh*2)
being in your specific case the hydraulic diameter Dh = 2d (where d is distance between parallel plates)
RE: Pressure drop in fluid flowing between flat plates
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RE: Pressure drop in fluid flowing between flat plates
Thanks for the replies. I'm trying to model the flow of a viscous (10 Pa.s) epoxy resin flowing between two parallel plates, under atmospheric pressure, i.e. the two plates are in a vacuum tank and outside the vacuum tank the resin is admitted through a feed through. This provides almost 1 bar of pressure to push the resin through the parallel plates. I'm using this formula to calculate the fluid velocity.
velocity = 1/(2*viscosity) * (dP/dx)*(y^2-h^2)
where x is the distance travelled
h is the half gap between the plates
I've been assuming that the dP/dx term is given by the driving pressure (~1 bar) divided by the distance the resin has travelled. This doesnt' agree with some CFD modelling carried out on the problem. The CFD modelling is ~25% faster than the text book solution.
I've tried to include Darcy Weisbach equation as suggested but I've got something wrong somewhere and it's making the resin speed up over time not slow down.
The gap is 1mm and the plates are ~300mm wide and 800mm long, the viscosity is 10Pa.s and the pressure is ~1 bar, the flow is laminar.
I'm hoping to benchmark the CFD modelling against the text book answer or find a reason why they're out by ~25%.
Many thanks
George
RE: Pressure drop in fluid flowing between flat plates
Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso
RE: Pressure drop in fluid flowing between flat plates
Thanks
George
RE: Pressure drop in fluid flowing between flat plates
RE: Pressure drop in fluid flowing between flat plates
RE: Pressure drop in fluid flowing between flat plates
The equation says that when y=h, velocity is 0.
Isn't the y term describing the y value in an (x,y) cartesian flow field and h (parallel to y) is relating the head at that point (over x) to dP across the total length of the field.
In that case, when y = h you have no flow, where in the hydraulic system you describe, velocity would be maximum midway between the two plates.
You seem to be using a groundwater flow through a porous medium equation to describe flow between plates, if I'm not wrong.
Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso