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Bogdan [553]
3 years ago
13

The Reynolds number is the major parameter that relates fluid flow momentum to friction forces. How is the Reynolds number defin

ed? How does the boundary layer thickness vary with Reynolds number?
Engineering
1 answer:
fiasKO [112]3 years ago
8 0

Answer:

Reynolds number determines whether a flow is laminar or turbulent flow.

Explanation:

Reynolds number is defined as ratio of inertia force to the viscous force. it is a dimension less  number. Reynolds number is used to describe the type of flow in a fluid whether it is laminar flow or turbulent flow. Reynolds number is denoted by Re.

When Reynolds number is in the range of 0 to 2000, the flow is considered to be laminar.

When Reynolds number is in the range of 2000 to 4000, the flow is considered to be transition.

And when Reynolds number is more than 4000, the flow is turbulent flow.

                     The boundary layer thickness for a fluid is given by

                                      δ = \frac{5\times x}{\sqrt{Re}}

where δ is boundary layer thickness

           x is distance from the leading edge

           Re is Reynolds number

Thus from the above boundary layer thickness equation, we can see that the boundary layer thickness varies inversely to square root of reynolds number.

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The components of an electronic system dissipating 180 W are located in a 1-m-long horizontal duct whose cross section is 16 cm
oee [108]

Answer:

a) The exit temperature is 39.25°C

b) The highest component surface is 132.22°C

c) The average temperature for air equal to 35°C is a good assumption because the air temperature at the inlet will increase due to the result in the heat gain produced by the duct and whose surface is exposed to a flow of hot.

Explanation:

a) The properties of the air at 35°C:

p = density = 1.145 kg/m³

v = 1.655x10⁻⁵m²/s

k = 0.02625 W/m°C

Pr = 0.7268

cp = 1007 J/kg°C

a) The mass flow rate of air is equal to:

m=\rho *V = 1.145*0.65=0.7443kg/min=0.0124kg/s

The exit temperature is:

T=T_{i} +\frac{Q}{m*c_{p} } =27+\frac{0.85*180}{0.0124*1007} =39.25°C

b) The mean fluid velocity is:

V_{m} =\frac{V}{A} =\frac{0.65}{0.16*0.16} =25.4m/min=0.4232m/s

The hydraulic diameter is:

D_{h} =\frac{4A}{p} =\frac{4*0.16*0.16}{4*0.16} =0.16m

The Reynold´s number is:

Re=\frac{VD_{h} }{v} =\frac{0.4232*0.16}{1.655x10^{-5} } =4091.36

Assuming fully developed turbulent flow, the Nusselt number is:

Nu=0.023Re^{0.8} *Pr^{0.4} =0.023*4091.36^{0.8} *0.7268^{0.4} =15.69

h=\frac{k*Nu}{D_{h} } =\frac{0.02625*15.69}{0.16} =2.57W/m^{2} C

The highest component surface temperature is:

T=T_{e} +\frac{\frac{Q}{A} }{h} =39.2+\frac{0.85*\frac{180}{4*0.16*1} }{2.57} =132.22°C

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3 years ago
ceramics must be heated in order to harden the clay and make it durable. the equipment used to heat the clay
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Ceramics must be heated in order to harden the clay and make it durable. The tool used to heat the clay is called a Kiln.

<h3>What happens when ceramic is heated?</h3>

Cristobalite is a silica polymorph that is used in ceramics. Quartz particles in porcelain can change into cristobalite during burning. This has effects on the fired matrix's thermal expansion. When there is a high level of vitrification or a shape is unstable during the firing of ceramic ware, warping occurs.

Ceramic items are porous, brittle, and rigid. They are thus employed in the production of glass, ceramics, cement, and bricks. Additionally, ceramics are employed extensively in gas turbine engines. Artificial bones and dental implants are both made of bio-ceramics.

Any of the several tough, fragile, heat- and corrosion-resistant materials created by sculpting and then heating an inorganic, nonmetallic material like clay to a high temperature are known as ceramics.

In order to solidify the clay and make ceramics durable, heat must be applied. A kiln is the name of the device used to heat clay.

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Answer:

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Explanation:

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<h3>What is a Manufacturing Revolution?</h3>

This refers to the process of change from a handicraft economy to industry production-based production.

Hence, we can see that Mr. Scalabre believes we are not growing in productivity because there has not been enough automation to perform the tasks needed.

The effect of robotics is making an impact on productivity because a lot of complex, difficult tasks are done by machines.

3D printing has made an impact on productivity because there is a reduction in the pressing cycle and errors due to negligence are reduced.

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