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Vanyuwa [196]
4 years ago
10

A 5-cm-diameter shaft rotates at 4500 rpm in a 15-cmlong, 8-cm-outer-diameter cast iron bearing (k = 70 W/m·K) with a uniform cl

earance of 0.6 mm filled with lubricating oil (μ = 0.03 N·s/m2 and k = 0.14 W/m·K). The bearing is cooled externally by a liquid, and its outer surface is maintained at 40°C. Disregarding heat conduction through the shaft and assuming one-dimensional heat transfer, determine (a) the rate of heat transfer to the coolant, (b) the surface temperature of the shaft, and (c) the mechanical power wasted by the viscous dissipation in oil.

Engineering
1 answer:
-BARSIC- [3]4 years ago
5 0

Answer:

(a) the rate of heat transfer to the coolant is Q = 139.71W

(b) the surface temperature of the shaft T = 40.97°C

(c) the mechanical power wasted by the viscous dissipation in oil 22.2kW

Explanation:

See explanation in the attached files

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A nozzle receives an ideal gas flow with a velocity of 25 m/s, and the exit at 100 kPa, 300 K velocity is 250 m/s. Determine the
Margaret [11]

Given Information:

Inlet velocity = Vin = 25 m/s

Exit velocity = Vout = 250 m/s

Exit Temperature = Tout = 300K

Exit Pressure = Pout = 100 kPa

Required Information:

Inlet Temperature of argon = ?

Inlet Temperature of helium = ?

Inlet Temperature of nitrogen = ?

Answer:

Inlet Temperature of argon = 360K

Inlet Temperature of helium = 306K

Inlet Temperature of nitrogen = 330K

Explanation:

Recall that the energy equation is given by

$ C_p(T_{in} - T_{out}) = \frac{1}{2} \times (V_{out}^2 - V_{in}^2) $

Where Cp is the specific heat constant of the gas.

Re-arranging the equation for inlet temperature

$ T_{in}  = \frac{1}{2} \times \frac{(V_{out}^2 - V_{in}^2)}{C_p}  + T_{out}$

For Argon Gas:

The specific heat constant of argon is given by (from ideal gas properties table)

C_p = 520 \:\: J/kg.K

So, the inlet temperature of argon is

$ T_{in}  = \frac{1}{2} \times \frac{(250^2 - 25^2)}{520}  + 300$

$ T_{in}  = \frac{1}{2} \times 119  + 300$

$ T_{in}  = 360K $

For Helium Gas:

The specific heat constant of helium is given by (from ideal gas properties table)

C_p = 5193 \:\: J/kg.K

So, the inlet temperature of helium is

$ T_{in}  = \frac{1}{2} \times \frac{(250^2 - 25^2)}{5193}  + 300$

$ T_{in}  = \frac{1}{2} \times 12  + 300$

$ T_{in}  = 306K $

For Nitrogen Gas:

The specific heat constant of nitrogen is given by (from ideal gas properties table)

C_p = 1039 \:\: J/kg.K

So, the inlet temperature of nitrogen is

$ T_{in}  = \frac{1}{2} \times \frac{(250^2 - 25^2)}{1039}  + 300$

$ T_{in}  = \frac{1}{2} \times 60  + 300$

$ T_{in}  = 330K $

Note: Answers are rounded to the nearest whole numbers.

5 0
3 years ago
The 1000-lb elevator is hoisted by the pulley system and motor M. The motor exerts a constant force of 500 lb on the cable. The
klemol [59]

The power that must be supplied to the motor is 136 hp

<u>Explanation:</u>

Given-

weight of the elevator, m = 1000 lb

Force on the table, F = 500 lb

Distance, s = 27 ft

Efficiency, ε = 0.65

Power  = ?

According to the equation of motion:

F = ma

3(500) - 1000 = \frac{1000}{32.2} * a

a = 16.1 ft/s²

We know,

v^2 - u^2 = 2a (S - So)\\\\v^2 - (0)^2 = 2 * 16.1 (27-0)\\\\v = 29.48m/s

To calculate the output power:

Pout = F. v

Pout = 3 (500) * 29.48

Pout = 44220 lb.ft/s

As efficiency is given and output power is known, we can calculate the input power.

ε = Pout / Pin

0.65 = 44220 / Pin

Pin = 68030.8 lb.ft/s

Pin = 68030.8 / 500 hp

     = 136 hp

Therefore, the power that must be supplied to the motor is 136 hp

5 0
4 years ago
A cyclic tensile load ranging from 0 kN to 55 kN force is applied along the length of a 100 mm long bar with a 15 mm x 15 mm squ
Yuliya22 [10]

Answer:

square cross section. The bar is made of a 7075-T6 aluminum alloy which has a yield strength of 500 MPa, a tensile strength of 575 MPa, and a fracture toughness of 27.5 MPaâm.

Required:

a. What is the nominal maximum tensile stress on the bar?

b. If there were an initial 1.2 mm deep surface crack on the right surface of the bar, what would the critical stress needed to cause instantaneous fast fracture of the bar be?

7 0
3 years ago
How do you determine when a truss will fail?<br> (Yield Stress)
Marat540 [252]

Answer:

If a truss buckles or overturns, it is usually because of the failure of an adjacent truss or its bracing. A steel truss in a fire may buckle and overturn because of expansion or weakening from the heat. Most truss failures are the result of broken connections. Photo 1 shows a set of parallel-chord wood trusses supporting a plywood floor deck.

Explanation:

7 0
3 years ago
If the tank is designed to withstand a pressure of 5 MPaMPa, determine the required minimum wall thickness to the nearest millim
dmitriy555 [2]

Answer: hello some aspects of your question is missing below is the missing information

The gas tank is made from A-36 steel and has an inner diameter of 1.50 m.

answer:

≈ 22.5 mm

Explanation:

Given data:

Inner diameter = 1.5 m

pressure = 5 MPa

factor of safety = 1.5

<u>Calculate the required minimum wall thickness</u>

maximum-shear-stress theory ( σ allow ) = σγ / FS

                                                  = 250(10)^6 / 1.5  = 166.67 (10^6) Pa

given that |σ| = σ allow  

3.75 (10^6) / t = 166.67 (10^6)

∴ t ( wall thickness ) = 0.0225 m   ≈ 22.5 mm

4 0
3 years ago
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