The derivation is does not consider the friction between the balls and also between the balls and drum...May be the we can go beyond critical speed to some extent by considering friction...Thank you
A lot...may it depends on be the capacity of machine to turn the drum. If we keep lot of steel balls, we need to compromise in rpm as it becomes very heavy...
When determining the Critical Speed of a Ball Mill, a dimensionless number in the equation is used as a Constant with no name. For me to be able to understand something, I have to be able to follow the path laid out. Then, I can know how it works and dive deep into it; I need to know how it works. I prefer to avoid answering a question and being unable to follow it up with more, so I need to understand this particular equation for critical speed. This Number, which eludes me, is 76.6. The equation Nc = 76.6/(D0.5) That last Number is supposed to be an exponent, but I'm trying to figure out where that 76.6 came from. I thought it was a derivation of the Reynolds number, but the chat says it has nothing to do with Reynolds, which seems like it, so I don't know why, but I need help finding out how to fix it. Re=uL/V=puL/μ . Where: ρ is the density of the fluid (SI units: kg/m3) u is the flow speed (m/s) L is a characteristic length (m) μ is the dynamic viscosity of the fluid (Pa·s or N·s/m2 or kg/(m·s)) ν is the kinematic viscosity of the fluid (m2/s). This started out as a simple curiosity for me many hours later. Now I have to know. Not that I care whether or not the chat and I can figure out whether or not this Number has an etymology. I also can't find exactly what it is or why it's there. Other than it's a balance of forces that makes sense to me. I still think it has something to do with Reynolds's Number, but I could be wrong. Thank you
Hi paul...let me clarify your doubt. It is the same equation which I have derived in the lecture. They have used two things to arrive to the conclusion 1.simplification 2. Units......simplification is when the ball radius is small compared to the drum radius (R>>>r) then (R-r)= R = D/2...therefore ,√(R-r)=√D /√2.....use g in ft/min^2...= 32 ft/s^2 = 116127.15 ft/min ^2...therefore the equation becomes Nc (rpm) = (√2*√116127.15)/(2*pi*√D)=76.7/√D......***use always the value of D in ft as g used in this equation is in ft/min^2....for example critical speed of ball mill with drum radius of 3 ft is =76.7/√3= 44 rpm...All the best
For a fixed rpm and ball radius, you can calculate maximum height (size) of a drum R using critical speed of ball mill. Nc = 1/2 pi sqrt (g/R-r). From this formula, if you know Nc, g, r then you can find R
Wah sir just i wached your video once and understood full so tanks sir❤
Most welcome
Sir ur explanation is good
Thanks and welcome
Thanks sir bhut achha samjhaya
Excellent presentation.
Thanks for watching
A very nice explanation given by you sir ❤❤❤ thanku so much 🙏
So nice of you
Sir what if we consider friction between the drum and ball
The derivation is does not consider the friction between the balls and also between the balls and drum...May be the we can go beyond critical speed to some extent by considering friction...Thank you
Thanks, Sir.
So normally, what is the percentage of ball in the ball mill?
A lot...may it depends on be the capacity of machine to turn the drum. If we keep lot of steel balls, we need to compromise in rpm as it becomes very heavy...
Thank you for a well explained lecture,
You are welcome!
Thanks and Welcome
Superb 🎉 explanation
Glad you liked it
Hello sir, in which book I get details and derivations about ball mill?
It is available in many books...unit operations of chemical engineering in MCcabe smith
When determining the Critical Speed of a Ball Mill, a dimensionless number in the equation is used as a Constant with no name.
For me to be able to understand something, I have to be able to follow the path laid out. Then, I can know how it works and dive deep into it; I need to know how it works. I prefer to avoid answering a question and being unable to follow it up with more, so I need to understand this particular equation for critical speed. This Number, which eludes me, is 76.6.
The equation Nc = 76.6/(D0.5)
That last Number is supposed to be an exponent, but I'm trying to figure out where that 76.6 came from. I thought it was a derivation of the Reynolds number, but the chat says it has nothing to do with Reynolds, which seems like it, so I don't know why, but I need help finding out how to fix it.
Re=uL/V=puL/μ .
Where:
ρ is the density of the fluid (SI units: kg/m3)
u is the flow speed (m/s)
L is a characteristic length (m)
μ is the dynamic viscosity of the fluid (Pa·s or N·s/m2 or kg/(m·s))
ν is the kinematic viscosity of the fluid (m2/s).
This started out as a simple curiosity for me many hours later. Now I have to know. Not that I care whether or not the chat and I can figure out whether or not this Number has an etymology. I also can't find exactly what it is or why it's there. Other than it's a balance of forces that makes sense to me. I still think it has something to do with Reynolds's Number, but I could be wrong. Thank you
Hi paul...let me clarify your doubt. It is the same equation which I have derived in the lecture. They have used two things to arrive to the conclusion 1.simplification 2. Units......simplification is when the ball radius is small compared to the drum radius (R>>>r) then (R-r)= R = D/2...therefore ,√(R-r)=√D /√2.....use g in ft/min^2...= 32 ft/s^2 = 116127.15 ft/min ^2...therefore the equation becomes Nc (rpm) = (√2*√116127.15)/(2*pi*√D)=76.7/√D......***use always the value of D in ft as g used in this equation is in ft/min^2....for example critical speed of ball mill with drum radius of 3 ft is =76.7/√3= 44 rpm...All the best
Thanks for your lecture!
You are welcome!
thankyou so much
Most welcome
how to calculate the maxiumu height of the ball
For a fixed rpm and ball radius, you can calculate maximum height (size) of a drum R using critical speed of ball mill. Nc = 1/2 pi sqrt (g/R-r). From this formula, if you know Nc, g, r then you can find R
Hello Sir, how can I contact u for one of my query?
surendra.sasikumar@sot.pdpu.ac.in