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3 years ago

What does self-consolidating concrete not need?

Engineering

1 answer:

Klio2033 [76]3 years ago

6 0

Answer:

Self-consolidating concrete does not need: Vibrating Given a proper gradation of satisfactory aggregates, the strength of cured concrete is primarily dependent on the amount of cement in the mix and on the water-cement (w-c or W/C) ratio. The higher the water-cement ratio the higher concrete strength. False

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A plane wall of thickness 0.1 m and thermal conductivity 25 W/m·K having uniform volumetric heat generation of 0.3 MW/m3 is insu

Contact [7]

Answer:

T = 167 ° C

Explanation:

To solve the question we have the following known variables

Type of surface = plane wall ,

Thermal conductivity k = 25.0 W/m·K,

Thickness L = 0.1 m,

Heat generation rate q' = 0.300 MW/m³,

Heat transfer coefficient hc = 400 W/m² ·K,

Ambient temperature T∞ = 32.0 °C

We are to determine the maximum temperature in the wall

Assumptions for the calculation are as follows

Negligible heat loss through the insulation
Steady state system
One dimensional conduction across the wall

Therefore by the one dimensional conduction equation we have

$k\frac{d^{2}T }{dx^{2} } +q'_{G} = \rho c\frac{dT}{dt}$

During steady state

$\frac{dT}{dt}$ = 0 which gives $k\frac{d^{2}T }{dx^{2} } +q'_{G} = 0$

From which we have $\frac{d^{2}T }{dx^{2} } = -\frac{q'_{G}}{k}$

Considering the boundary condition at x =0 where there is no heat loss

$\frac{dT}{dt}$ = 0 also at the other end of the plane wall we have

$-k\frac{dT }{dx } =$ hc (T - T∞) at point x = L

Integrating the equation we have

$\frac{dT }{dx } = \frac{q'_{G}}{k} x+ C_{1}$ from which C₁ is evaluated from the first boundary condition thus

0 = $\frac{q'_{G}}{k} (0)+ C_{1}$ from which C₁ = 0

From the second integration we have

$T = -\frac{q'_{G}}{2k} x^{2} + C_{2}$

From which we can solve for C₂ by substituting the T and the first derivative into the second boundary condition s follows

$-k\frac{q'_{G}L}{k} = h_{c}( -\frac{q'_{G}L^{2} }{k} + C_{2}-T∞)$ → C₂ = $q'_{G}L(\frac{1}{h_{c} }+ \frac{L}{2k} } )+T∞$

T(x) = $\frac{q'_{G}}{2k} x^{2} + q'_{G}L(\frac{1}{h_{c} }+ \frac{L}{2k} } )+T∞$ and T(x) = T∞ + $\frac{q'_{G}}{2k} (L^{2}+(\frac{2kL}{h_{c} }} )-x^{2} )$

∴ Tmax → when x = 0 = T∞ + $\frac{q'_{G}}{2k} (L^{2}+(\frac{2kL}{h_{c} }} ))$

Substituting the values we get

T = 167 ° C

4 0

4 years ago

If a cylindrical part with a length of 20 mm and a diameter of 20 mm is to be machined to a cylindrical part with 18 mm in diame

bulgar [2K]

Answer:

Titanium Alloy

Explanation:

Length ( L ) = 20 mm

D1 = 20 mm

d2 = 18 mm

l = 20 mm

Mechanical efficiency = 50%

power = 80 kW

cutting rake angle = 0°

cutting speed ( v ) = 10 m/s

<u>Determine the material to be for the cylinder </u>

In order to choose a material for the cylinder we have to calculate the cutting force

P = Fc * V

80 = Fc * 10 m/s

therefore Fc = 80 / 10 = 8 N

Hence the material we can use is Titanium Alloy due to low cutting force value

3 0

3 years ago

Explain three (3) modes of heat transfer in air conditioning system.

LenKa [72]

Answer:

1. Conduction

2. Convection

3. Radiation

Explanation:

The 3 modes of heat transfer i an air conditioning system:

1. Conduction:

The transfer of heat by conduction takes place in solid and is when the conduction takes place as a result of direct contact in between the interacting material which transfer the heat energy from particle to particle thus conducting the heat through out the system.

2. Convection:

The other mode for the transfer of heat which takes place especially in fluids - gases and liquids is through the technique of convection in which the transfer of heat takes place by the circular motion of the atoms and molecules of the fluid which carries the heat energy and results in the distribution of the heated fluid in the entire system thus transferring all the heat energy in the entire system.

3. Radiation:

The third mode of heat transfer in the air conditioning system is through radiation. This method transfers the heat by making use of the electro-magnetic radiation in the infra red spectrum where the waves of the spectrum transfers the heat energy with the help of a medium or without any medium at all.

Thus making the radiation method of heat transfer as the only method out of the three methods which does not require the material medium for the transfer of heat energy.

4 0

3 years ago

In the ______ phase of the organizational life cycle, the organization is usually very small and agile, focusing on new products

Vlad [161]

Answer:

Entrepreneurship

Explanation:

Different phases of organizational life cycles can be observed depending on the stage of the company. These cycles are,

Entrepreneurship
Survival and Early Success
Sustained Success
Renewal (or Decline)

In the initial stage which is Entrepreneurship Phase, all of the founders take part in various activities, no formality is formed between founders and employees. Generally lots of ideas are present and company is actively searching to define correct market and products to focus on.

5 0

3 years ago

A priority encoder circuit has four inputs,X3-0. The circuit has three outputs: Z,Y1-0. If any of X3-0is 1, then Zis 1, and Y re

sladkih [1.3K]

Answer:

Detailed solution is given below:

3 0

3 years ago