Velocity from 8m³ Tank

The answer may be obtained by looking at typical discharge co-efficients for the hole, which may be found in such publications as Perry, "The Chemical Engineer's Handbook", and Welty, Wicks & Wilson, "Fundamentals of Heat, Mass and Momentum Transfer". Clearly, at the beginning of the operation the velocity will be at its maximum and as the level in the tank falls, so will the velocity. Velocity will be affected by temperature, as temperature affects viscosity, which will in turn affect the flow through the hole. Other factors include the shape of the hole, the profile of the piercing, the length of any spout projecting from it and the distance the resulting jet has to travel before impacting any surface; the inclination of the surface to the direction of the jet will also have a weak effect.

At a guess the tank will be practically empty within 2 minutes. One hopes that the local drainage arrangements are sufficient to prevent damage or loss to the building, its contents and the occupants when this occurs.

Don't forget the pressure head!

You'll have to know what you coefficient is, also what type of penetration.

there is basic software for this called Engineering Power Tools. It uses imperial units, but still does the job, the software predetermines the coeffiencent.

Keep in mind your water column also changes.....

You want to know, or does your teacher want to know if you have absorbed enough knowledge from previous discussions to calculate? From MANY of the posts in the various areas of CR4, it seems many people have graduated, and gotten jobs where they are making decisions that they have no knowledge or experience to make. This is a sad state. No wonder China's development is accelerating. At what point are you measuring the velocity?

Full to zero. Take the average.

Homework at home

I'm a plumber, have fixed hundreds of tanks and respective pipelines. Pressure, yes, I know, though not by values but by feel. But, velocity, yes, heard of this during schooling, and what is that ?

You said

I pierce a hole to the bottom of tank

is this hole at the true bottom,? so it is horizontal

Or it is at the lowest part of the tank´s wall?

It is a circle 100 mm diameter , or a 100 mm side square?

Yes friend

hole is 100Diameter, from horizontal area of bottom of tank.

Best regards

Dear Friend,

The Pressure and Velocity is linked by the equation V^2 = 2 x g x H or V = Sq.Rt of 2 x g x H where V is the THEORITICAL VELOCITY of the Water, g is the acceleration due to gravity, H is the Head of water.

We have to multiply the Theoritical Velocity by a factor called Cv which is 0.8 for water - Refer any standard Hydraulic s Book.

The Pressure given by you is 2000 Kg/M^2 which is equal to 0.2 Metre, of water column.

The theoritical velocity will work out to 14 Metres, by using the above equation and multiplying this theoritical velocity by Cv i.e. 0.8, the Actual Velocity will be 14 x 0.8 = 11.2 Metres/Sec.

The hole size has nothing to do with the velocity but for discharge calculation hole size is required.

DHAYANANDHAN.S

At a pressure of 2000 kgf/m2 , equivalent to 0.2 kgf/cm2 which is related to 2m of head. Not 0.20m. In which case the final velocity is about 5m/sec .

Tq.

Dear Mr. Satish Menon,

You are absolutely right. Pressure of 2000 Kg/m^2 is equal to 0.2 Kg/cm^2 is equivalent to 2.15 Metres of Water Column.

It is a mistake on my part, and for this 2.15 Metre Head of water will give a theoritical velocity of Sq.Rt of 2 x9.81 x 2.15 = Sq.Rt of 42.183 = 6.494 and After Cv correction it will be 5.19 M/Sec.

Thanks for your correction. To other CR4 Members, the error is regretted.

DHAYANANDHAN.S

Dear Mr dhayanandha,

Please can you explain me to this error as amplify? I kindly request because, i am poor to knowledge.

Please let me know, how to get the value of (velocity coefficient of water).

very thank

Best regards

Start Here:

http://engineering.wikia.com/wiki/Orifice_equation

Whom ever confirm my previous post , no the OP, off course.

I pierce a hole to the bottom of tank

is this hole at the true bottom,? so it is horizontal

Or it is at the lowest part of the tank´s wall? so it is vertical

It is a circle 100 mm diameter , or a 100 mm side square?

With out it specification, all previous said by other poster have no value , just guessing