Convert 580,000 kW to [GW] with correct number of significant digits.

Air at 400 kPa, 980 K enters a turbine operating at steady state and exits at 100 kPa, 670 K. Heat transfer from the turbine occ

shusha [124]

Answer:

A)W'/m = 311 KJ/kg

B)σ'_gen/m = 0.9113 KJ/kg.k

Explanation:

a).The energy rate balance equation in the control volume is given by the formula;

Q' - W' + m(h1 - h2) = 0

Dividing through by m, we have;

(Q'/m) - (W'/m) + (h1 - h2) = 0

Rearranging, we have;

W'/m = (Q'/m) + (h1 - h2)

Normally, this transforms to another equation;

W'/m = (Q'/m) + c_p(T1 - T2)

Where;

W'/m is the rate at which power is developed

Q'/m is the rate at which heat is flowing

c_p is specific heat at constant pressure which from tables at a temperature of 980k = 1.1 KJ/kg.k

T1 is initial temperature

T2 is exit temperature

We are given;

Q'/m = -30 kj/kg (negative because it leaves the turbine)

T1 = 980 k

T2 = 670 k

Plugging in the relevant values;

W'/m = -30 + 1.1(980 - 670)

W'/m = 311 KJ/kg

B) The Entropy produced from the entropy balance equation in a control volume is given by the formula;

(Q'/T_boundary) + m(s1 - s2) + σ'_gen = 0

Dividing through by m gives;

((Q'/m)/T_boundary) + (s1 - s2) + σ'_gen/m = 0

Rearranging, we have;

σ'_gen/m = -((Q'/m)/T_boundary) + (s2 - s1)

Under the conditions given in the question, this transforms normally to;

σ'_gen/m = -((Q'/m)/T_boundary) - c_p•In(T2/T1) - R•In(p2/p1)

σ'_gen/m is the rate of entropy production in kj/kg

We are given;

p2 = 100 kpa

p1 = 400 kpa

T_boundary = 315 K

For an ideal gas, R = 0.287 KJ/kg.K

Plugging in the relevant values including the ones initially written in answer a above, we have;

σ'_gen/m = -(-30/315) - 1.1(In(670/980)) - 0.287(In(100/400))

σ'_gen/m = 0.0952 + 0.4183 + 0.3979

σ'_gen/m = 0.9113 KJ/kg.k

6 0

3 years ago

An unknown immiscible liquid seeps into the bottom of an open oil tank. Some measurements indicate that the depth of the unknown

barxatty [35]

Answer:

The specific weight of unknown liquid is found to be 15 KN/m³

Explanation:

The total pressure in tank is measured to be 65 KPa in the tank. But, the total pressure will be equal to the sum of pressures due to both oil and unknown liquid.

Total Pressure = Pressure of oil + Pressure of unknown liquid

65 KPa = (Specific Weight of oil)(depth of oil) + (Specific Weight of unknown liquid)(depth of unknown liquid)

65 KN/m² = (8.5 KN/m³)(5 m) + (Specific Weight of Unknown Liquid)(1.5 m)

(Specific Weight of Unknown Liquid)(1.5 m) = 65 KN/m² - 42.5 KN/m²

(Specific Weight of Unknown Liquid) = (22.5 KN/m²)/1.5 m

Specific Weight of Unknown Liquid = 15 KN/m³

4 0

3 years ago

According to the Bureau of Labor Statistics, which occupation employed 4.2 million people – more than any other occupation – in

Ludmilka [50]

Answer:

Retail Salespersons

Explanation:

The Bureau of Labor Statistics or the BLS in short is the federal unit or agency of the United States Labor Department. It is the main stats finding agency of the United States federal government in the field of statistics and labor economics.

According to a publication published by the Labor Statistics Bureau, the retail salesperson sector of occupation employed the most people in the U.S. in the year 2010. It provided employment to about 4.2 million people.

5 0

3 years ago

A tubular reactor has been sized to obtain 98% conversion and to process 0.03 m^3/s. The reaction is a first-order irreversible

Zolol [24]

Answer:

The conversion in the real reactor is = 88%

Explanation:

conversion = 98% = 0.98

process rate = 0.03 m^3/s

length of reactor = 3 m

cross sectional area of reactor = 25 dm^2

pulse tracer test results on the reactor :

mean residence time ( tm) = 10 s and variance (∝2) = 65 s^2

note: space time (t) =

t = $\frac{A*L}{Vo}$ Vo = flow metric flow rate , L = length of reactor , A = cross sectional area of the reactor

therefore (t) = $\frac{25*3*10^{-2} }{0.03}$ = 25 s

since the reaction is in first order

X = 1 - $e^{-kt}$

$e^{-kt}$ = 1 - X

kt = In $\frac{1}{1-X}$

k = In $\frac{1}{1-X}$ / t

X = 98% = 0.98 (conversion in PFR ) insert the value into the above equation then

K = 0.156 $s^{-1}$

Calculating Da for a closed vessel

; Da = tk

= 25 * 0.156 = 3.9

calculate Peclet number Per using this equation

0.65 = $\frac{2}{Per} - \frac{2}{Per^2} ( 1 - e^{-per})$

therefore

$\frac{2}{Per} - \frac{2}{Per^2} (1 - e^{-per}) - 0.65 = 0$

solving the Non-linear equation above( Per = 1.5 )

Attached is the Remaining part of the solution

3 0

3 years ago

What is the difference between erratic error and zero error

Slav-nsk [51]

The negative mark is balanced by a positive mark on the set key scale while the jaws are closed.

It is common practice to shut the jaws or faces of the system before taking some reading to guarantee a zero reading. If not, please take care of the read. This read is referred to as "zero defect."

There are two forms of zero error:

zero-mistake positive; and

Non-null mistake.

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Hope this helps!

Brainliest would be great!

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With all care,

07x12!

5 0

3 years ago