Which of the following is a common use for commas?

The steady-state data listed below are claimed for a power cycle operating between hot and cold reservoirs at 1200K and 400K, re

Anni [7]

Answer:

a) W_cycle = 200 KW , n_th = 33.33 % , Irreversible

b) W_cycle = 600 KW , n_th = 100 % , Impossible

c) W_cycle = 400 KW , n_th = 66.67 % , Reversible

Explanation:

Given:

- The temperatures for hot and cold reservoirs are as follows:

TL = 400 K

TH = 1200 K

Find:

For each case W_cycle , n_th ( Thermal Efficiency ) :

(a) QH = 600 kW, QC = 400 kW

(b) QH = 600 kW, QC = 0 kW

(c) QH = 600 kW, QC = 200kW

- Determine whether the cycle operates reversibly, operates irreversibly, or is impossible.

Solution:

- The work done by the cycle is given by first law of thermodynamics:

W_cycle = QH - QC

- For categorization of cycle is given by second law of thermodynamics which states that:

n_th < n_max ...... irreversible

n_th = n_max ...... reversible

n_th > n_max ...... impossible

- Where n_max is the maximum efficiency that could be achieved by a cycle with Hot and cold reservoirs as follows:

n_max = 1 - TL / TH = 1 - 400/1200 = 66.67 %

And, n_th = W_cycle / QH

a) QH = 600 kW, QC = 400 kW

- The work done by cycle according to First Law is:

W_cycle = 600 - 400 = 200 KW

- The thermal efficiency of the cycle is given by n_th:

n_th = W_cycle / QH

n_th = 200 / 600 = 33.33 %

- The type of process according to second Law of thermodynamics:

n_th = 33.333 % n_max = 66.67 %

n_th < n_max

Hence, Irreversible Process

b) QH = 600 kW, QC = 0 kW

- The work done by cycle according to First Law is:

W_cycle = 600 - 0 = 600 KW

- The thermal efficiency of the cycle is given by n_th:

n_th = W_cycle / QH

n_th = 600 / 600 = 100 %

- The type of process according to second Law of thermodynamics:

n_th = 100 % n_max = 66.67 %

n_th > n_max

Hence, Impossible Process

c) QH = 600 kW, QC = 200 kW

- The work done by cycle according to First Law is:

W_cycle = 600 - 200 = 400 KW

- The thermal efficiency of the cycle is given by n_th:

n_th = W_cycle / QH

n_th = 400 / 600 = 66.67 %

- The type of process according to second Law of thermodynamics:

n_th = 66.67 % n_max = 66.67 %

n_th = n_max

Hence, Reversible Process

7 0

3 years ago

The larger the Bi number, the more accurate the lumped system analysis. a)-True b)- False

mrs_skeptik [129]

Answer:

b). False

Explanation:

Lumped body analysis :

Lumped body analysis states that some bodies during heat transfer process remains uniform at all times. The temperature of these bodies is a function of temperature only. Therefor the heat transfer analysis based on such idea is called lumped body analysis.

Biot number is a dimensionless number which governs the heat transfer rate for a lumped body. Biot number is defined as the ratio of the convection transfer at the surface of the body to the conduction inside the body. the temperature difference will be uniform only when the Biot number is nearly equal to zero.

The lumped body analysis assumes that there exists a uniform temperature distribution within the body. This means that the conduction heat resistance should be zero. Thus the lumped body analysis is exact when biot number is zero.

In general it is assume that for a lumped body analysis, Biot number $\leq$ 0.1

Therefore, the smaller the Biot number, the more exact is the lumped system analysis.

7 0

3 years ago

What is the ratio between driver gear A with 60 teeth and driven gear B with 180 teeth?

Anna71 [15]

The ratio between a and b is 1/3

3 0

3 years ago

For a steel alloy it has been determined that a carburizing heat treatment of 7 hour duration will raise the carbon concentratio

Aliun [14]

Answer:

18.6h

Explanation:

To solve this Duck's second law in form of Diffusion will be used.

Also note that since the temperature is constant D (change) will also be constant.

Please go through the attached files for further explanation and how the answer Is gotten.

6 0

3 years ago

La viscosidad de un liquido es igual a 0.04 N s/m^2 . Este valor en Dinas s/cm^2 se encuentra en el literal

nadezda [96]

Answer:

0.4 Dinas*s/cm^2

Explanation:

Tenemos una viscosidad:

V = 0.04 N*s/m^2

Y queremos reescribir esto en Dinas*s/cm^2

Primero transformemos la unidad del denominador, es decir, tenemos que pasar de 1/m^2 a 1/cm^2

Para ello, usamos que:

1m = 100cm

entonces:

(1m/100cm) = 1

Si elevamos ambos lados al cuadrado, obtenemos:

(1m/100cm)^2 = 1

Ahora podemos multiplicar el valor de la viscosidad por esto (que es igual a 1)

V = 0.04 N*s/m^2*((1m/100cm)^2 = 0.00004 N*s/cm^2

Ahora debemos convertir de Newtons a Dinas

Sabemos que:

1 N = 100,000 dinas

1 = (100,000 dinas/1N)

Entonces, de vuelta podemos multiplicar nuestra viscosidad por (100,000 dinas/1N), que es igual a 1 (asi que no cambia el valor, solo sirve para cambiar las unidades)

0.00004 N*s/cm^2 = (100,000 dinas/1N)*(0.00004 N*s/cm^2)

= (100,000 dinas)*(0.00004 s/cm^2)

= 0.4 Dinas*s/cm^2

5 0

3 years ago