Answer: 383.22K
Explanation:
L = 3m, w = 1.5m
Area A = 3 x 1.5 = 4.5m2
Q' = 750W/m2 (heat from sun) ,
& = 0.87
Q = &Q' = 0. 87x750 = 652.5W/m2
E = QA = 652.5 x 4.5 = 2936.25W
T(sur) = 300K, T(panel) = ?
Using E = §€A(T^4(panel) - T^4(sur))
§ = Stefan constant = 5.7x10^-8
€ = emmisivity = 0.85
2936.25 = 5.7x10^-8 x 0.85 x 4.5 x (T^4(panel) - 300^4)
T(panel) = 383.22K
See image for further details.
Answer:
b). False
Explanation:
Lumped body analysis :
Lumped body analysis states that some bodies during heat transfer process remains uniform at all times. The temperature of these bodies is a function of temperature only. Therefor the heat transfer analysis based on such idea is called lumped body analysis.
Biot number is a dimensionless number which governs the heat transfer rate for a lumped body. Biot number is defined as the ratio of the convection transfer at the surface of the body to the conduction inside the body. the temperature difference will be uniform only when the Biot number is nearly equal to zero.
The lumped body analysis assumes that there exists a uniform temperature distribution within the body. This means that the conduction heat resistance should be zero. Thus the lumped body analysis is exact when biot number is zero.
In general it is assume that for a lumped body analysis, Biot number 0.1
Therefore, the smaller the Biot number, the more exact is the lumped system analysis.
Answer :
The force needed to move the cylinder is 25.6 N
<h2>Further explanation </h2>Given that,
Length of the cylinder, l = 0.5 m
Outer diameter of the cylinder, d = 8 cm = 0.08 m
Outer radius of the cylinder,
Inside diameter of the pipe, d = 8.5 cm = 0.085 m
Inside radius of the pipe,
Specific gravity of the oil,
Density of oil,
Kinematic viscosity of the oil,
Velocity of the cylinder, u = 1 m/s
We need to find the force needed to move the cylinder. Let the force is F.
Specific gravity is defined as the ratio of the density of the substance to the density of water.
Kinematic viscosity is the acquired resistance of a fluid when there is no external force is acting except gravity. It is denoted by v.
Absolute viscosity is given by :
Where, = density of oil
And (density of oil = specific gravity × density of water )
So,
..............(1)
The separation between the cylinder and pipe is given by :
are diameter of pipe and cylinder respectively.
The mathematical expression for the Newton's law of viscosity can be written as:
..........(2)
Where
= Shear stress,
............(3)
= viscosity
= rate of shear deformation
On rearranging equation (1), (2) and (3) we get :
...............(4)
A is the area of the cylinder,
Equation (4) becomes :
..............(5)
Now, equation (5) becomes :
F = 25.6 N
<h2>Learn more </h2>Kinematic viscosity : brainly.com/question/12947932
<h2>Keyword : </h2>Specific gravity, Kinematic viscosity, Area of cylinder, fluid mass density.