All categories

3 years ago

Which dimensionless parameter tells whether flow disturbances will be attenuated or amplified? a. Pr b. Re C G d. St e. Fe

Engineering

1 answer:

Aleonysh [2.5K]3 years ago

7 0

Answer:

b. Re

Explanation:

Reynolds number describe the type of flow of fluid. If Reynolds number has a high value then it is called turbulent flow and if Reynolds number is low then it is called laminar flow. Reynolds number given as follows:

$Re=\dfrac{\rho VD}{\mu }$

For internal pipe flow, if Reynolds number greater than 4000 then, it is called turbulent flow and if Reynolds number less than 2000 then it is called laminar flow. The Reynolds number between 2000 to 4000 the flow is called transition flow.

You might be interested in

HELP<br><br><br>the overall width of a part is dimensioned as 3.00 ± 0.02. what is the tolerance

MariettaO [177]

Answer:

Not knowing the units the tolerance is 0.02. I would presume mm but hopefully your question has more detail.

Explanation:

The tolerance is the portion after the main dimension (+/- 0.02). In our case we have bilateral tolerance since there is tolerance in both directions (positive and negative). If you were building a part the acceptable range would be 2.98 to 3.02 based on the tolerance provided.

3 0

3 years ago

Read 2 more answers

The statement that is NOT true about the concept of a boundary layer on an object is: a. the Reynolds number is greater than uni

Ilya [14]

Answer:

Option E

Explanation:

All the given statements are true except the velocity gradients normal to the flow direction are small since these are not normally small. It's true that viscous effects are present only inside the boundary layer and the fluid velocity equals the free stream velocity at the edge of the boundary layer. Moreover, Reynolds number is greater than unity and the fluid velocity is zero at the surface of the object.

5 0

3 years ago

Describe, in a general form, the equation, in time domain, that tells the voltage across a inductor, L, as a function of time wh

love history [14]

Answer:

a) V(t) = Ldi(t)/dt

b) If current is constant, V = 0

Explanation:

a) The voltage, V(t), across an inductor is proportional to the rate of change of the current flowing across it with time.

If V represents the Voltage across the inductor

and i(t) represents the current across the inductor in time, t.

V(t) ∝ di(t)/dt

Introducing a proportionality constant,L, which is the inductance of the inductor

The general equation describing the voltage across the inductor of inductance, L, as a function of time when a current flows through it is shown below.

V(t) = Ldi(t)/dt ..................................................(1)

b) If the current flowing through the inductor is constant i.e. does not vary with time

di(t)/dt = 0 and hence the general equation (1) above becomes

V(t) = 0

4 0

4 years ago

If a heat engine has an efficiency of 30% and its power output is 600 W, what is the rate of heat input from the combustion phas

jarptica [38.1K]

Answer:

The heat input from the combustion phase is 2000 watts.

Explanation:

The energy efficiency of the heat engine ( $\eta$ ), no unit, is defined by this formula:

$\eta = \frac{\dot W}{\dot Q}$ (1)

Where:

$\dot Q$ - Heat input, in watts.

$\dot W$ - Power output, in watts.

If we know that $\dot W = 600\,W$ and $\eta = 0.3$ , then the heat input from the combustion phase is:

$\eta = \frac{\dot W}{\dot Q}$

$\dot Q = \frac{\dot W}{\eta}$

$\dot Q = \frac{600\,W}{0.3}$

$\dot Q = 2000\,W$

The heat input from the combustion phase is 2000 watts.

8 0

3 years ago

How much cornfield area would be required if you were to replace all the oil consumed in the United States with ethanol from cor

zaharov [31]

Answer:

2377.35 km

Explanation:

Given the following;

1. A cornfield is 1.5% efficient at converting radiant energy into stored chemical potential energy;

2. The conversion from corn to ethanol is 17% efficient;

3. A 1.2:1 ratio for farm equipment to energy production

4. A 50% growing season and,

5. 200 W/m2 solar insolation.

As per our assumptions,1.2/1 is the ratio for farm equipment to energy production,

So USA need around 45.45% (1/(1+1.2) replacement of fuel energy production which is nearly about = 0.4545*10^{20} J/year = \frac{0.4545*10^{20}}{365*24*3600}=1.44121*10^{12} J/sec

Growing season is only part of year ( Given = 50%),

Net efficiency = 1.5%*17%*50%=0.015*0.17*0.5=0.001275 = 0.1275%

Hence , Actual Energy replacement (Efficiency),

=\frac{1.44121*10^{12}}{0.001275} = 1.13*10^{15} J/sec=1.13*10^{15} W

As per assumption (5),

\because 200 W/m2 solar insolation arequired,

So USA required corn field area = 1.13*10^{15}/200 = 5.65*10^{12} m^{2}

Hence, length of each side of a square,

= (5.65*10^{12} )^{0.5} = 2377.35 km

4 0

4 years ago