4 replies to this topic

[narra]

hii everyone
As part of a project I was expected o design a transport system for a suspension of CNTs in epoxy resin.I have performed some calculations and here they are
specifications:
Flow rate,q : 3 l/min (180LPH)
viscosity ,m : 1800 cPs
sp.gravity : 1.5

equipment selections:
pipe material : acylic
pipe size : 1/2" schedule 40
total pipe length = 3m
fittings : 4 long radius 90elbows
pump type : internal gear

calculations:

Re = 4.4 (laminar)
head to be developed by pump : 46.5 m ( very high!!)
power (P= rho*q*g*h) = 65W

Due to laminar flow the friction losses in pipes and fittings [ Δh = λ (l / d_h) (v² / 2g )]
came to be very high.And due to very less flow rate the power calculated is very low..
Can anyone tell me if there are any mistakes in my calculations or selections?

regards

[ankur2061]

narra,

As per my calculations some data is as follows:

Total pipe length: Pipe Straight length + Equivalent length of 4, 90 deg elbows = 3 + 0.2*4 = 3.8 m

Assuming that your head calculation of 46.5 m is right then the power consumption I calcualte is below:

P = Q*H*rho*g / (3600*eta)

where:

Q = 0.18 m3/h
H = 46.5 m
rho = 1500 kg/m3
g = 9.81 m/s2
eta = pump efficiency = 0.5

Absorbed power = 68 W

The key factor in power calculations besides the usual flow, head and specific gravity is the pump efficiency. Recheck what effciency is required for your pump.

Also recalculate the head based on total pipe length i.e. straight length plus the equivalent length.

Hope this helps.

Regards,
Ankur.

[narra]

Mr.ankur
thanks for the reply.So according to you my calculations are correct.But I wonder if I selected the equipment accurately,i.e, do you concur with the pipe size (its actually 3/8" not 1/2" as mentioned before) I selected?
Regards

[ankur2061]

narra,

3/8" (0.375 inch) Sch. 40 pipe corresponds to an inside diameter of 0.493 inch. Re-do your calculations for total differential head considering this pipe inside diameter and check. I haven't done your head calculations. I can check your calculations if you present them.

Regards,
Ankur.

[Dazzler]

Hi Nara
Aside from calculations, for epoxy resins and even more so when there are additives I would be very wary of the possibility of chosing a pump that does not have enough power. I would be generous with power selection for resin applications, just in case the viscosity is non-neutonian or you have to start or run the pump under cooler temperatures when the viscosity could be much higher. Be sure also that a positive desplacement pump type has a relief valve in case too much presure is developed by the pump.

I've attached below an abstract I just found on line that mentions viscosity and epoxy resin. You might be able to find other info.

"Abstract:
Epoxy nanocomposites were fabricated using two kinds of nanofiller, amino-functionalized multi-walled carbon nanotubes (CNTs) and non-treated long carbon nanofibers (CNFs). The non-cured mixtures were analysed through viscosity measurements. The effect of the nanoreinforcement on the curing process was determined by differential scanning calorimetry. Finally, the characterisation of cured nanocomposites was carried out studying their thermo-mechanical and electrical behaviour. At room temperature, the addition of CNTs causes a viscosity increase of epoxy monomer much more marked than the introduction of CNFs due to their higher specific area. It was probed that in that case exists chemical reaction between amino-functionalized CNTs and the oxirane rings of epoxy monomer. The presence of nanoreinforcement induces a decrease of curing reaction rate and modifies the epoxy conversion reached. The glass transition temperature of the nanocomposites decreases with the contents of CNTs and CNFs added, which could be related to plasticization phenomena of the nanoreinforcements. The storage modulus of epoxy resin significantly increases with the addition of CNTs and CNFs. This augment is higher with amino-functionalized CNTs due, between other reasons, to the stronger interaction with the epoxy matrix. The electrical conductivity is greatly increased with the addition of CNTs and CNFs. In fact, the percolation threshold is lower than 0.25 wt% due to the high aspect ratio of the used nanoreinforcements."

Dazzler