Answer:
Explanation:
Given that
We know that
Rex=ρvx/μ
So
All other quantities are constant only x is a variable in the above equation .so lets take all other quantities as a constant C
We also know that
Nux=hx/K
m is the constant
This is local heat transfer coefficient
The average value of h given as
---------1
The value of local heat transfer coefficient at x=L
-----------2
From 1 and 2 we can say that
Answer:
The time required is 10.078 hours or 605 min
Explanation:
The formula to apply here is ;
K=(d²-d²₀ )/t
where t is time in hours
d is grain diameter to be achieved after heating in mm
d₀ is the grain diameter before heating in mm
Given
d=5.5 × 10^-2 mm
d₀=2.4 × 10^-2 mm
t₁= 500 min = 500/60 =25/3 hrs
t₂=?
n=2.2
First find K
K=(d²-d²₀ )/t₁
K={ (5.1 × 10^-2 mm)²-(2.4 × 10−2 mm)² }/ 25/3
K=(0.051²-0.024²) ÷25/2
K=0.000243 mm²/h
Re-arrange equation for K ,to get the equation for d as;
d=√(d₀²+ Kt) where now t=t₂