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22 days ago

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8. When supplying heated air for a building, one often chooses to mix in some fresh outside air with air that has been heated fr

om the building as it passes through the furnace. An insulated mixing chamber is used to combine two streams of air to be used in a building. One stream of air, brought from the outside, enters at 2 kg/s, at a pressure of 120 kPa, and a temperature of 5oC. The second stream of air, coming from the building’s furnace, has a mass flow rate of 8 kg/s, a pressure of 120 kPa, and a temperature of 35oC. The combined stream is then delivered to the warm space at 120 kPa. Determine the rate of entropy generation for this mixing chamber.

1 answer:

pantera1 [306]22 days ago

5 0

Refer to the explanation for a detailed breakdown.

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A copper-constantan thermocouple is to be used to measure temperatures between 0 and 200°C. The e.m.f. at 0°C is 0 mV, at 100°C

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What is the magnitude of the maximum stress that exists at the tip of an internal crack having a radius of curvature of 3 × 10-4

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The maximum stress at the tip of the internal crack is calculated as 2872.28 MPa. Explanation: Details provided include the curvature radius of 3 × 10^-4 mm, a crack length of 5.5 × 10^-2 mm, and an applied tensile stress of 150 MPa. The equation used determines maximum stress based on these inputs.

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1 month ago

The rate of flow of water in a pump installation is 60.6 kg/s. The intake static gage is 1.22 m below the pump centreline and re

mote1985 [299]

Answer:

The power of the pump is 23.09 kW.

Explanation:

Parameters

gravitational constant, $g = 9.81 m/s^2$

mass flow rate, $\dot{m} = 60.6 kg/s$

flow density, $\rho = 1000 kg/m^3$

efficiency of the pump, $\eta = 0.74$

output gauge pressure, $p_o = 344.75 kPa$

input gauge pressure, $p_i = 68.95 kPa$

cross-sectional area of output pipe, $A_o = 0.069 m^2$

cross-sectional area of input pipe, $A_i = 0.093 m^2$

height of discharge, $z_o = 1.22 m - 0.61 m = 0.61 m$ (evaluated at pump’s maximum height of 1.22 m)

input height, $z_i = 0 m$

hydraulic power of the pump, $P =? kW$

Initially, the volumetric flow (Q) needs to be determined

$Q = \frac{\dot{m}}{\rho}$

$Q = \frac{60.6 kg/s}{1000 kg/m^3}$

$Q = 0.0606 m^3/s$

Next, compute the velocity (v) for both input and output

$v_o = \frac{Q}{A_o}$

$v_o = \frac{0.0606 m^3/s}{0.069 m^2}$

$v_o = 0.88 m/s$

$v_i = \frac{Q}{A_i}$

$v_i = \frac{0.0606 m^3/s}{0.093 m^2}$

$v_i = 0.65 m/s$

Subsequently, the total head (H) can be calculated

$H = (z_o - z_i) + \frac{v_o^2 - v_i^2}{2 \, g} + \frac{p_o - p_i}{\rho \, g}$

$H = (0.61 m - 0 m) + \frac{{0.88 m/s}^2 - {0.65 m/s}^2}{2 \, 9.81 m/s^2} + \frac{(344.75 Pa-68.95 Pa)\times 10^3}{1000 kg/m^3 \, 9.81 m/s^2}$

$H = 28.74m$

Finally, the computation of pump power is done as follows

$P = \frac{Q \, \rho \, g \, H}{\eta}$

$P = \frac{0.0606 m^3/s \, 1000 kg/m^3 \, 9.81 m/s^2 \, 28.74m}{0.74}$

$P = 23.09 kW$

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2 months ago

Three return steam lines in a chemical processing plant enter a collection tank operating at steady state at 1 bar. Steam enters

alex41 [359]

Response:

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b) 99.61 °C

Rationale:

Refer to the pictures provided.

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22 days ago

A 90-hp (shaft output) electric car is powered by an electric motor mounted in the engine compartment. If the motor has an avera

pantera1 [306]

Answer:

Heat supply rate is measured at 8.901 horsepower.

Explanation:

Energy efficiency of the electric vehicle, as per Thermodynamics ( $\eta$ ), is the proportion of translational mechanical power ( $\dot E_{out}$ ), expressed in horsepower, and electrical energy ( $\dot E_{in}$ ), also in horsepower. The heat supply rate ( $\dot E_{l}$ ), indicated in horsepower, that the motor delivers to the engine bay under full load can be determined by subtracting the translational mechanical energy from the electric energy. This is expressed as:

$\eta = \frac{\dot E_{out}}{\dot E_{in}}$ (1)

$\dot E_{l} = \dot E_{in}-\dot E_{out}$ (2)

$\dot E_{l} = \left(\frac{1}{\eta}-1\right)\cdot \dot E_{out}$ (3)

If we have the values of $\eta = 0.91$ and $\dot E_{out} = 90\,hp$ , the heat supply rate can be calculated as:

$\dot E_{l} = \left(\frac{1}{0.91}-1 \right)\cdot (90\,hp)$

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The heat supply rate amounts to 8.901 horsepower.

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1 month ago