Answer:
23.3808 kW
20.7088 kW
Explanation:
ρ = Density of oil = 800 kg/m³
P₁ = Initial Pressure = 0.6 bar
P₂ = Final Pressure = 1.4 bar
Q = Volumetric flow rate = 0.2 m³/s
A₁ = Area of inlet = 0.06 m²
A₂ = Area of outlet = 0.03 m²
Velocity through inlet = V₁ = Q/A₁ = 0.2/0.06 = 3.33 m/s
Velocity through outlet = V₂ = Q/A₂ = 0.2/0.03 = 6.67 m/s
Height between inlet and outlet = z₂ - z₁ = 3m
Temperature to remains constant and neglecting any heat transfer we use Bernoulli's equation
[tex]\frac {P_1}{\rho g}+\frac{V_1^2}{2g}+z_1+h=\frac {P_2}{\rho g}+\frac{V_2^2}{2g}+z_2\\\Rightarrow h=\frac{P_2-P_1}{\rho g}+\frac{V_2^2-V_1^2}{2g}+z_2-z_1\\\Rightarrow h=\frac{(1.4-0.6)\times 10^5}{800\times 9.81}+\frac{6.67_2^2-3.33^2}{2\times 9.81}+3\\\Rightarrow h=14.896\ m[/tex]
Work done by pump
[tex]W_{p}=\rho gQh\\\Rightarrow W_{p}=800\times 9.81\times 0.2\times 14.896\\\Rightarrow W_{p}=23380.8\ W[/tex]
∴ Power input to the pump 23.3808 kW
Now neglecting kinetic energy
[tex]h=\frac{P_2-P_1}{\rho g}+z_2-z_1\\\Righarrow h=\frac{(1.4-0.6)\times 10^5}{800\times 9.81}+3\\\Righarrow h=13.19\ m\\[/tex]
Work done by pump
[tex]W_{p}=\rho gQh\\\Rightarrow W_{p}=800\times 9.81\times 0.2\times 13.193\\\Rightarrow W_{p}=20708.8\ W[/tex]
∴ Power input to the pump 20.7088 kW
Atmospheric pressure is measured to be 14.769 psia. a. What would be the equivalent reading of a water barometer (inches of H20)? b. What would be the equivalent reading of a Mercury barometer (mm of Hg)?
Answer:
(a) water height =408.66 in.
(b) mercury height=30.04 in.
Explanation:
Given: P=14.769 psi ( 1 psi= 6894.76 [tex]\frac{N}{m^2}[/tex] )
we know that [tex]P=\rho\times g\timesh[/tex]
where [tex]\rho =Density,g=9.81\frac{m}{s^2}[/tex]
h=height.
Given that P=14.769 psi ⇒P= 101828.6 7[tex]\dfrac{N}{m^2}[/tex]
(a) [tex]P=\rho_{w}\times g\times h_{w}[/tex]
[tex]\rho_{w}=1000\frac{Kg}{m^3}[/tex]
⇒101828.67=[tex]1000\times 9.81\times h_{w}[/tex]
[tex]h_{w}[/tex]=10.38 m
So water barometer will read 408.66 in. (1 m=39.37 in)
(b) [tex]P=\rho_{hg}\times g\times h_{hg}[/tex]
[tex]\rho_{hg}[/tex]=13600
So 101828.67=[tex]13600\times 9.81\times h_{hg}[/tex]
[tex]h_{hg}[/tex]=0.763 m
So mercury barometer will read 30.04 in.
What is the maximum thermal efficiency possible for a power cycle operating between 600P'c and 110°C? a). 47% b). 56% c). 63% d). 74%
Answer:
(b) 56%
Explanation:
the maximum thermal efficiency is possible only when power cycle is reversible in nature and when power cycle is reversible in nature the thermal efficiency depends on the temperature
here we have given T₁ (Higher temperature)= 600+273=873
lower temperature T₂=110+273=383
Efficiency of power cycle is given by =1-[tex]\frac{T2}{T1}[/tex]
=1-[tex]\frac{383}{873}[/tex]
=1-0.43871
=.56
=56%
What is Euler's equation?
Answer:
[tex]e^{ix} = cosx + i sinx[/tex]
Explanation:
In mathematics, Euler's formula is an equation in complex analysis, that gives a relationship between an exponential factor and the trigonometric functions.
The Euler equation is:
[tex]e^{ix} = cosx + i sinx[/tex]
Here,
e - base of the natural logarithm
i - imaginary unit
x - argument given in radians
sin , cos - trigonometric functions sine and cosine respectively.
Convert 0.025 in into mm.
Answer: 0.025 in = 0.065 mm
Explanation: To convert the value in inches to mm we have to multiply the inches by the conversion factor 25.4.
So, 0.025 × 25.4 = 0.065 mm (millimeter)
Conversion formula for calculation in (inch) into mm is:
Value in mm = Value in in × 25.4
One inch is equal to the 25.4 mm.Answer:
.025 inch = 0.635 mm
Explanation:
We know that 1 inch = 2.54 cm
also we know that 1 cm = 10 mm
Thus 1 inch = 2.54 x 10 mm
=> 1 inch = 25.4 mm
Hence 0.025 inch = 25.4 x .025 mm
Thus .025 inch = 0.635 mm
Heat transfer by is the fastest mode of heat transfer that requires no intervening medium. a)-conduction b)-convection c)-radiation d)-conduction and convection
Answer:
C. Radiation
Explanation:
Heat transfer through Conduction is a slow process and both Conduction and convection require material medium
Answer:
C radiation
Explanation:
Explain the Otto cycle of a 4 stroke engine.
Answer:
Otto cycle for 4 stroke engine:
Assumptions:
1.Air is a working fluid it will behave like ideal gas.
2.Mass of air is constant(close system)
3.All process is reversible process.
4.Specific heat of air does not depends on temperature.
4 stroke engine is an internal combustion engine.It works on 4 processes like intake ,compression,power and heat exhaust.To complete one cycle ,piston moves from top dead center to bottom dead center two times.
From the Otto cycle
Process 1-2 is isentropic compression.
Process 2-3 is heat addition.
Process 3-4 is isentropic expansion.
Process 4-1 is heat rejection.
Petrol engine works on Otto cycle.
Efficiency of cycle [tex]\eta[/tex]
[tex]\eta=\dfrac{W_{net}}{Q_{supply}}[/tex]
The Otto cycle is a four-step thermodynamic cycle used in four-stroke internal combustion engines to convert heat into work. It consists of the intake, compression, power, and exhaust strokes. The cycle helps in understanding engine efficiency and performance.
Explanation:The Otto cycle is a thermodynamic cycle that is used in four-stroke internal combustion engines. It consists of four processes: intake, compression, power, and exhaust.
The intake stroke is when the mixture of fuel and air is drawn into the combustion chamber. The compression stroke compresses the mixture adiabatically, increasing its temperature and pressure. During the power stroke, the mixture is ignited, creating a rapid increase in pressure that pushes the piston down. Finally, the exhaust stroke expels the burnt gases from the combustion chamber.
The Otto cycle is an idealized representation of the processes that occur in an engine and it describes the thermodynamic changes that are involved in converting heat into work. It helps in understanding the efficiency and performance of four-stroke engines.
How is entropy defined on a differential basis? (use an equation)?
Answer:
Differential entropy differ's from the normal entropy as in case of differential entropy random variable needs not to be discrete.
The differential concept of entropy is as follows
Let X be a random variable which is continuous
Let[tex]f(x)[/tex] be it's probability distribution function
We have differential entropy h(X) defined as
[tex]h(X)=-\int _{X}f(X)log[f(X)]dx[/tex]
The random variable 'X' need not to be discrete and it is continuous.
Assume that light of wavelength 6000A is coming from a star. What is the limit of resolution of a telescope whose objective has a diameter of 100 inch?
Answer:
θ=0.0288 radian
Explanation:
resolution limit is the minimum angular separation of two sources that can be viewed distinctly by telescope
[tex]\theta =\frac{1.22\times \lambda}{D}[/tex]
[tex]\lambda=6000\times 10^{-8} cm=6 \times 10^{-5} cm[/tex]
[tex]d=100 inch=100\times 2.54=254cm[/tex]
[tex]\theta = \frac{1.22 \times 6 \times 10^{-5}}{254}[/tex]
θ=0.0288 radian
Explain very briefly the traditional casting and non-traditional casting process.
Answer:
traditional casting -- sand casting
non traditional casting - investment casting
Explanation:
Traditional casting is related to sand casting in which liquid is poured into mold cavity. once the poured material cool and solidify the casting is removed.
traditional casting is cheaper than non traditional casting . Mold use in traditional casting is very cheap .
non traditional casting include investment casting, die casting , wax casting. In this casting fix dimension is provided unlike sand casting.
Maximum iorsional shear siress.? Select one: a)- occurs at the center of a shaft. b)- occurs at the outer surface of a shaft c)- occurs at the inner surface of a shaft.
Answer:
b). Occurs at the outer surface of the shaft
Explanation:
We know from shear stress and torque relationship, we know that
[tex]\frac{T}{J}= \frac{\tau }{r}[/tex]
where, T = torque
J = polar moment of inertia of shaft
τ = torsional shear stress
r = raduis of the shaft
Therefore from the above relation we see that
[tex]\tau = \frac{T.r}{J}[/tex]
Thus torsional shear stress, τ is directly proportional to the radius,r of the shaft.
When r= 0, then τ = 0
and when r = R , τ is maximum
Thus, torsional shear stress is maximum at the outer surface of the shaft.
Sam promises to pay Sandy $2,000 in four years and another $3,000 four years later for a loan of $2,000 from Sandy today. What is the interest rate that Sandy is getting? Assume interest is compounded monthly. A. 14.75% B. 16.72% C. 15.10% D. 18.08%
Answer:
the interest rate that Sandy is getting is (C.) 15.10%
Explanation:
Given data
in 4 year cash pay (p1) = $2000
in 8 year cash pay (p2) = $3000
time period (t1) = 4 years
time period (t2) = 8 years
loan value = $2000
To find out
interest rate
solution
first we know amount will be paid in first 4 year is
$2000 [tex](1+r/100)^{12t}[/tex]
$2000 [tex](1+r/100)^{48}[/tex] ...................1
now we calculate the next payment will paid after 4 year i.e.
$2000 [tex](1+r/100)^{12t}[/tex] - $2000
$2000 [tex](1+r/100)^{48}[/tex] - $2000 ..................2
after full time period of payment total amount will be paid by equation 1 and 2 i.e.
$3000 = $2000 [tex](1+r/100)^{48}[/tex] ×$2000 [tex](1+r/100)^{48}[/tex] - $2000
$3000 = $2000 ( [tex](1+r/100)^{48}[/tex] × [tex](1+r/100)^{48}[/tex] - 1 ) .....3
now we have solve [tex](1+r/100)^{48}[/tex] this eqution
so we consider [tex](1+r/100)^{48}[/tex] = A
so new equation will be by equation 3
$3000/$2000 = ( A - 1 ) × A
3/2 = A² - A
solve this equation we get 2A² - 2 A - 3 = 0 so A = 1.823
now we compute A again in [tex](1+r/100)^{48}[/tex] = A
[tex](1+r/100)^{48}[/tex] = 1.823
so rate (r) = 1.258 % / month
and rate yearly = 1.258 ×12
the interest rate that Sandy is getting yearly 15.10 %
An inventor claims to have devised a cyclical power engine that operates with a fuel whose temperature is 750 °C and radiates waste heat to a sink at 0 °C. He also claims that this engine produces 3.3 kW while rejecting heat at a rate of 4.4 kW. Is this claim valid?
Answer:
Yes
Explanation:
Given Data
Temprature of source=750°c=1023k
Temprature of sink =0°c=273k
Work produced=3.3KW
Heat Rejected=4.4KW
Efficiency of heat engine(η)=[tex]\frac{Work produced}{Heat supplied}[/tex]
and
Heat Supplied [tex]{\left (Q_s\right)}=Work Produced(W)+Heat rejected\left ( Q_r \right )[/tex]
[tex]{Q_s}=3.3+4.4=7.7KW[/tex]
η=[tex]\frac{3.3}{7.7}[/tex]
η=42.85%
Also the maximum efficiency of a heat engine operating between two different Tempratures i.e. Source & Sink
η=1-[tex]\frac{T_ {sink}}{T_ {source}}[/tex]
η=1-[tex]\frac{273}{1023}[/tex]
η=73.31%
Therefore our Engine Efficiency is less than the maximum efficiency hence the given claim is valid.
Atmospheric air at 25 °C and 8 m/s flows over both surfaces of an isothermal (179C) flat plate that is 2.75m long. Determine the heat transfer rate per unit from the plate for 3 width different values of the critical Reynolds number: 100,000; 500,000; and 1,000,000
Answer:
Re=100,000⇒Q=275.25 [tex]\frac{W}{m^2}[/tex]
Re=500,000⇒Q=1,757.77[tex]\frac{W}{m^2}[/tex]
Re=1,000,000⇒Q=3060.36 [tex]\frac{W}{m^2}[/tex]
Explanation:
Given:
For air [tex]T_∞[/tex]=25°C ,V=8 m/s
For surface [tex]T_s[/tex]=179°C
L=2.75 m ,b=3 m
We know that for flat plate
[tex]Re<30\times10^5[/tex]⇒Laminar flow
[tex]Re>30\times10^5[/tex]⇒Turbulent flow
Take Re=100,000:
So this is case of laminar flow
[tex]Nu=0.664Re^{\frac{1}{2}}Pr^{\frac{1}{3}}[/tex]
From standard air property table at 25°C
Pr= is 0.71 ,K=26.24[tex]\times 10^{-3}[/tex]
So [tex]Nu=0.664\times 100,000^{\frac{1}{2}}\times 0.71^{\frac{1}{3}}[/tex]
Nu=187.32 ([tex]\dfrac{hL}{K_{air}}[/tex])
187.32=[tex]\dfrac{h\times2.75}{26.24\times 10^{-3}}[/tex]
⇒h=1.78[tex]\frac{W}{m^2-K}[/tex]
heat transfer rate =h[tex](T_∞-T_s)[/tex]
=275.25 [tex]\frac{W}{m^2}[/tex]
Take Re=500,000:
So this is case of turbulent flow
[tex]Nu=0.037Re^{\frac{4}{5}}Pr^{\frac{1}{3}}[/tex]
[tex]Nu=0.037\times 500,000^{\frac{4}{5}}\times 0.71^{\frac{1}{3}}[/tex]
Nu=1196.18 ⇒h=11.14 [tex]\frac{W}{m^2-K}[/tex]
heat transfer rate =h[tex](T_∞-T_s)[/tex]
=11.14(179-25)
= 1,757.77[tex]\frac{W}{m^2}[/tex]
Take Re=1,000,000:
So this is case of turbulent flow
[tex]Nu=0.037Re^{\frac{4}{5}}Pr^{\frac{1}{3}}[/tex]
[tex]Nu=0.037\times 1,000,000^{\frac{4}{5}}\times 0.71^{\frac{1}{3}}[/tex]
Nu=2082.6 ⇒h=19.87 [tex]\frac{W}{m^2-K}[/tex]
heat transfer rate =h[tex](T_∞-T_s)[/tex]
=19.87(179-25)
= 3060.36 [tex]\frac{W}{m^2}[/tex]
Explain the difference between thermal equilibrium and thermodynamic equilibriurm.
Answer:
A body is said to be in thermal equilibrium where all the system temperatures are the same.
A body is said to be in thermodynamic equilibrium if all three requirements of equilibrium are met
Explanation:
A body is said to be in thermal equilibrium where all the system temperatures are the same. In this case, there will be no temperature gradient between the system and the environment.
while, A body is said to be in thermodynamic equilibrium if all three requirements of equilibrium are met, i.e. mechanical equilibrium, chemical equilibrium and thermal equilibrium.
Define the work Envelope for a Robot
For all substances, Cp>C. Why is that?
A system that is not influence anyway by the surroundings is called a)- control mass system b)- Isothermal system c)-- isolated system d)- open system
Answer:
Isolated system
Explanation:
By definition of a closed system it means that a system that does not interact with it's surroundings in any manner
The other options are explained as under:
Isothermal system : It is a system that does not allow it's temperature to change
Control Mass system : It is a system whose mass remains conserved which means the mass entering the system equals the mass leaving the system
Open system: It is a system that allows transfer of mass and energy across it's boundary without any opposition i.e freely.
If you know that the change in entropy of a cup of coffee where heat was added is 20 J/K, and that the temperature of the coffee is 250 K. what is the amount of heat added to the cup of coffee? a)-15 J b)-125J c)-600J d)-5000J d)-6000J
Answer:
5000J
Explanation:
Given in the question that
Heat added to the coffee cup is, ΔS = 20 J/K
The temperature of the coffee, T = 250 K
Now, using the formula for the entropy change
[tex]\bigtriangleup S=-\frac{\bigtriangleup H}{T}[/tex] ...........(1)
Where,
ΔS is the entropy change
ΔH is the enthalpy change
T is the temperature of the system
substituting the values in the equation (1)
we get
[tex]20=-\frac{\bigtriangleup H}{250}[/tex]
ΔH=250×20
ΔH=5000 J
In solid rocket motor terminology, a sliver is: A. A basic geometric shape B. Leftover propellant C. A test article for propellant characterization D. A type of igniter
Answer:
In the question given out of the four options
option B. Leftover propellant
is correct.
Explanation:
Solid rocket motors have rocket engines that uses solid fuels or propellants such as HTPB and PBAN as the most commonly used binders.
These rockets always have the propellant in adequate amount can be powered for long enough without much fuel degradation and therefore are reliable and mostly used in military applications.
Since these have fuel or propellant storage and therefore to indicate it, solid rocket motor identifies the left over propellant as ' a silver' .
An inventor claims to have invented a heat engine that operates between the temperatures of 627°C and 27°C with a thermal efficiency of 70%. Comment on the validity of this claim.
Answer Explanation:
the efficiency of the the engine is given by=1-[tex]\frac{T_2}{T_1}[/tex]
where T₂= lower temperature
T₁= Higher temperature
we have given efficiency =70%
lower temperature T₂=27°C=273+27=300K
higher temperature T₁=627°C=273+627=900K
efficiency=1-[tex]\frac{T_2}{T_1}[/tex]
=1-[tex]\frac{300}{900}[/tex]
=1-0.3333
=0.6666
=66%
66% is less than 70% so so inventor claim is wrong
How does the thermal efficiency of an ideal cycle, in general, compare to that of a Carnot cycle operating between the same temperature limits?
Answer:
Rankine cycle less efficient as compare to Carnot cycle operating betwwen same temperature limit.
Explanation:
We know that Carnot's cycle is an ideal cycle for all heat engine which operating between same temperature.It is a reversible cycle which have all process reversible that is why it have maximum efficiency.
On the other hand Rankine cycle is a practical working cycle so it is impossible to make all process reversible .In practical there will be always loss due to this any process can not make 100 % reversible.That is why Rankine cycle have low efficiency as compare to Carnot cycle operating between same temperature limits.
A plate clutch has a single friction surface 9-in OD by 7-in ID. The coefficient of friction is 0.2 and the maximum pressure is 1.5 in-kip. Find the torque capacity using the uniform-pressure assumption.
Answer:
the torque capacity is 30316.369 lb-in
Explanation:
Given data
OD = 9 in
ID = 7 in
coefficient of friction = 0.2
maximum pressure = 1.5 in-kip = 1500 lb
To find out
the torque capacity using the uniform-pressure assumption.
Solution
We know the the torque formula for uniform pressure theory is
torque = 2/3 × [tex]\pi[/tex] × coefficient of friction × maximum pressure ( R³ - r³ ) .....................................1
here R = OD/2 = 4.5 in and r = ID/2 = 3.5 in
now put all these value R, r, coefficient of friction and maximum pressure in equation 1 and we will get here torque
torque = 2/3 × [tex]\pi[/tex] × 0.2 × 1500 ( 4.5³ - 3.5³ )
so the torque = 30316.369 lb-in
Define the isentropic efficiency for each of the following 3. a. i. Adiabatic turbine ii. Adiabatic compressor iii. Adiabatic nozzle
Answer:
a)[tex]\eta_{st}=\dfrac{\Delta h_{actual}}{\Delta _{ideal}}[/tex]
b)[tex]\eta_{sc}=\dfrac{\Delta h_{ideal}}{\Delta _{actual}}[/tex]
c)[tex]\eta_{sn}=\dfrac{\Delta h_{actual}}{\Delta _{ideal}}[/tex]
Explanation:
a)
Adiabatic turbine
Adiabatic turbine means turbine can not reject or take heat from surrounding.
Isentropic efficiency of turbine can be define as the ratio of actual work out put to the Ideal or isentropic work out put.Ideal means when turbine will give maximum work and there is no any friction losses we can say when process is isentropic.
Isentropic efficiency of turbine=(Actual work output)/(Ideal work output)
[tex]\eta_{st}=\dfrac{\Delta h_{actual}}{\Delta _{ideal}}[/tex]
b)
Adiabatic compressor
Isentropic efficiency of compressor can be define as the ratio of ideal or isentropic work in put to the actual work in put.
Isentropic efficiency of turbine=(Ideal work input)/(actual work input)
[tex]\eta_{sc}=\dfrac{\Delta h_{ideal}}{\Delta _{actual}}[/tex]
c)Adiabatic nozzle
We know that nozzle is device which used to accelerate the fluid.
Basically it covert pressure energy to kinetic energy.
Isentropic efficiency of nozzle can be define as the ratio of actual enthalpy drop put to the Ideal or isentropic enthalpy drop.
[tex]\eta_{sn}=\dfrac{\Delta h_{actual}}{\Delta _{ideal}}[/tex]
_________ items are similar to the free issue items, but their access is limited. (CLO5) a)-Bin stock items free issue b)-Bin stock controlled issue c)-Critical or insurance spares d)-Rebuildable spares
e)-consumables
Answer:
a)-Bin stock items free issue
Explanation:
Bin stock items free issue items are similar to the free issue items, but their access is limited.
Bin stock items free issue items are similar to the free issue items, but their access is limited.
Describe how the diesel engine works.
Answer:
Diesel engine's working is based on internal combustion. Diesel engine can be categorized as two stroke diesel engines and 4 stroke diesel engines.
Let us look into the working of a 4 stroke diesel engine:
In a four stroke diesel engine the operation continues by rotating in cycle of 4 strokes or stages. In these 4 stages the piston moves up and down the crankcase twice or the crankshaft rotates twice. the four strokes are listed below:
1) Inlet: In this, the air mixture is made to enter through the inlet valve as the piston moves downwards.
2) Compression: Inlet valve is closed and the air mixture is compressed and the piston moves up. Fuel is injected into the heated air mixture through central injection valve and ignition takes place without the need of spark plug.
3) Expansion or Power: After ignition, mixture burns and due to expansion of gas, piston moves down, it drives the crankshaft to send power to the wheel.
4) Exhaust: This is the last stroke which results in the piston moving up to let out the exhaust gases
Moreover, in 2 stroke diesel engine, there is only one rotation of crankshaft and one stroke includes inlet and compression and the other includes expansion and exhaust
Cutting and abrasive machining are the two major material processes. List the differences between Cutting tool and Abrasive machining tool.
Answer:
Explained
Explanation:
Cutting tools:
1. Cutting tools can either be single point or multi point.
2. Cutting tools can have variety of material depending on use like ceramics, diamonds, metals, CBN, etc.
3.Cutting tools have definite shapes and geometry.
Abrasive machining tools
1. Abrasive tools are always multi point tools.
2. Abrasive tools composed of abrasives bounded in medium of resin or metal.
3. They do not have definite geometry of shape
Cutting tools engage materials with a sharp edge for aggressive material removal, while abrasive machining tools employ hard particles to wear away material for high precision and smoothness in finishing operations.
Explanation:The differences between cutting tools and abrasive machining tools are fundamental in the processes they are used for and their operational principles. Cutting tools are typically used in operations like turning, milling, and drilling where the tool itself engages the material to be cut with a sharp edge, removing materials in the form of chips. These tools are often made of high-speed steel, carbide, ceramics, or other hard materials and are precisely shaped according to the specific cutting operation.
On the other hand, abrasive machining tools, which include grinding wheels, sandpaper, and abrasive belts, remove material through the action of hard, abrasive particles that are either bonded to the tool's surface or are used as loose grains. Abrasive machining is used for finishing surfaces to a high degree of smoothness, precision, and complex shapes that cutting tools cannot achieve. These tools are made of materials like aluminum oxide, silicon carbide, diamond, or cubic boron nitride.
To summarize, cutting tools use a sharp edge to remove material in a defined shape, while abrasive tools use hard particles to wear away material for finishing and shaping. Moreover, cutting tools are applied in more aggressive material removal processes and quicker operations like shaping or roughing out material, whereas abrasive machining is associated with finishing operations that require high precision and smoothness.
The Reynolds number is the major parameter that relates fluid flow momentum to friction forces. How is the Reynolds number defined? How does the boundary layer thickness vary with Reynolds number?
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 = [tex]\frac{5\times x}{\sqrt{Re}}[/tex]
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.
Why/how is a paperclip able to float on water?
Answer:
Water surface tension
Explanation:
The water around the paperclip forms a kind of elastic surface, deforming, in which the clip can stay afloat.
This is because the molecules that are on the surface of the water, already in contact with the air, try to cling to those that are next to them and those that are immediately below.
If we added even if it were just a drop of soap in the water, the clip would go to the bottom, because the soap has the ability to decrease the surface tension of the water.
What is the quality of a two-phase liquid-vapor mixture of H20 at 20 °C with a specific volume of 10 m^3/kg?
Answer:
Quality of vapor is equal to 17.3%.
Explanation:
We know that if we know only one property in side the wet region then we will find the other property by using steam property table.
So pressure at saturation temperature 20°C
[tex]v_f= 0.001\frac{m^3}{Kg} ,v_g= 57.76\frac{m^3}{Kg}[/tex]
So specific volume v
[tex]v=v_f+x(v_g-v_f)\frac{m^3}{Kg}[/tex]
Where x is quality of mixture
Now putting the values ,given that [tex]v=10m^3/kg[/tex]
[tex]10=0.001+x(57.76-0.001)\frac{m^3}{Kg}[/tex]
x=0.173
So quality of vapor is equal to 17.3%.
In an apartment the interior air temperature is 20°C and exterior air temperatures is 5°C. The wall has inner and outer surface temperatures of 16°C and 6°C, respectively. The inner and outer convection heat transfer coefficients are 5 and 20 W/m2.K, respectively. Calculate the heat flux from the interior air to the wall, from the wall to the exterior air, and from the wall to the interior air. Is the wall under steady-state conditions?
Answer:
20 W/m², 20 W/m², -20 W/m²
Yes, the wall is under steady-state conditions.
Explanation:
Air temperature in room = 20°C
Air temperature outside = 5°C
Wall inner temperature = 16°C
Wall outer temperature = 6°C
Inner heat transfer coefficient = 5 W/m²K
Outer heat transfer coefficient = 20 W/m²K
Heat flux = Concerned heat transfer coefficient × (Difference of the temperatures of the concerned bodies)
q = hΔT
Heat flux from the interior air to the wall = heat transfer coefficient of interior air × (Temperature difference between interior air and exterior wall)
⇒ Heat flux from the interior air to the wall = 5 (20-6) = 20 W/m²
Heat flux from the wall to the exterior air = heat transfer coefficient of exterior air × (Temperature difference between wall and exterior air)
⇒Heat flux from the wall to the exterior air = 20 (6-5) = 20 W/m²
Heat flux from the wall to the interior air = heat transfer coefficient of interior air × (Temperature difference between wall and interior air)
⇒Heat flux from the wall and interior air = 5 (16-20) = -20 W/m²
Here the magnitude of the heat flux are same so the wall is under steady-state conditions.