1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
frez [133]
2 years ago
12

As part of a heat treatment process, cylindrical, 304 stainless steel rods of 100-mm diameter are cooled from an initial tempera

ture of 500 C by suspending them in an oil bath at 30 C. If a convection coefficient of 500 W/m2 K is maintained by circulation of the oil, how long does it take for the centerline of a rod to reach a temperature of 50 C, at which point it is withdrawn from the bath
Engineering
1 answer:
saveliy_v [14]2 years ago
5 0

Answer:

Explanation:

Given that:

diameter = 100 mm

initial temperature = 500 ° C

Conventional coefficient = 500 W/m^2 K

length  = 1 m

We obtain the following data from the tables A-1;

For the stainless steel of the rod \overline T = 548 \ K

\rho = 7900 \ kg/m^3

K = 19.0 \ W/mk \\ \\ C_p = 545 \ J/kg.K

\alpha = 4.40 \times 10^{-6} \ m^2/s \\ \\  B_i = \dfrac{h(\rho/4)}{K} \\ \\  =0.657

Here, we can't apply the lumped capacitance method, since Bi > 0.1

\theta_o = \dfrac{T_o-T_{\infty}}{T_i -T_\infty}} \\ \\ \theta_o = \dfrac{50-30}{500 -30}} \\ \\ \theta_o = 0.0426\\

0.0426 = c_1 \ exp (- E^2_1 F_o_)\\ \\ \\  0.0426 = 1.1382 \ exp (-10.9287)^2 \ f_o   \\ \\ = f_o = \dfrac{In(0.0374)}{0.863} \\ \\ f_o = 3.81

t_f = \dfrac{f_o r^2}{\alpha} \\ \\ t_f = \dfrac{3.81 \times (0.05)^2}{4.40 \times 10^{-6}} \\ \\  t_f= 2162.5 \\ \\ t_f = 36 mins

However, on a single rod, the energy extracted is:

\theta = pcv (T_i - T_{\infty} )(1 - \dfrac{2 \theta}{c} J_1 (\zeta) )  \\ \\ = 7900 \\times 546 \times 0.007854 \times (500 -300) (1 - \dfrac{2 \times 0.0426}{1.3643}) \\ \\  \theta = 1.54 \times 10^7 \ J

Hence, for centerline temperature at 50 °C;

The surface temperature is:

T(r_o,t) = T_{\infty} +(T_1 -T_{\infty}) \theta_o \ J_o(\zeta_1) \\ \\ = 30 + (500-30) \times 0.0426 \times 0.5386 \\ \\ \mathbf{T(r_o,t) = 41.69 ^0 \ C}

You might be interested in
Air at atmospheric pressure and at 300K flows with a velocity of 1.5m/s over a flat plate. The transition from laminar to turbul
Savatey [412]

Answer:3.47 m

Explanation:

Given

Temperature(T)=300 K

velocity(v)=1.5 m/s

At 300 K

\mu =1.846 \times 10^{-5} Pa-s

\rho =1.77 kg/m^3

And reynold's number is given by

Re.=\frac{\rho v\time x}{\mu }

5\times 10^5=\frac{1.77\times 1.5\times x}{1.846\times 10^{-5}}

x=\frac{5\times 10^5\times 1.846\times 10^{-5}}{1.77\times 1.5}

x=3.47 m

5 0
3 years ago
A 1000 kg turbine has a rotating unbalance of 0.1 kg.m. The turbine operates at a speed between 500 to 750 rpm. What is the maxi
raketka [301]

Answer:

maximum isolator stiffness k =1764 kN-m

Explanation:

mean speed of rotation =\frac{N_1 +N_2}{2}

Nm = \frac{500+750}{2} = 625 rpm

w =\frac{2\pi Nm}{60}

  =65.44 rad/sec

F_T = mw^2 e

F_T = mew^2

       = 0.1*(65.44)^2

F_T =428.36 N

Transmission ratio =\frac{300}{428.36} = 0.7

also

transmission ratio = \frac{1}{[\frac{w}{w_n}]^{2} -1}

0.7 =\frac{1}{[\frac{65.44}{w_n}]^2 -1}

SOLVING FOR Wn

Wn = 42 rad/sec

Wn = \sqrt {\frac{k}{m}

k = m*W^2_n

k = 1000*42^2 = 1764 kN-m

k =1764 kN-m

3 0
3 years ago
Energy transfer in mechanical systems: During steady-state operation, a mechanical gearbox receives 70 KW of input power through
Degger [83]

Answer:

Heat transfer rate(Q)= 1.197kW

Power output(W)=68.803kW

3 0
2 years ago
If a worksite includes more than one set of management and workers, who should have access to the information, training, and con
Elden [556K]

Answer:

In a work site with more than one set of management and workers the Health and  safety officers in each set  should have access to the information, training and controls needed to avoid workplace accidents

Explanation:

The primary aim of a health and  safety officer in a workplace is to prevent accidents,injuries and work-related sickness from occurring in the work site by creating and implementing health and safety policies according to international standards and also ensure that these policies are implemented  by the sets of management and workers/staffs of the work site.  to achieve these they therefore should have access to the information,training and controls needed to avoid workplace accidents

4 0
3 years ago
Read 2 more answers
Acertain foundation will experience a bearing capacity failurewhen it is subjected to a downward load of 2200 kN. Using ASD with
ehidna [41]

Answer:

Um...

Explanation:

This is what I like to see teachers giving out.

7 0
2 years ago
Other questions:
  • The steel water pipe has an inner diameter of 12 in. and a wall thickness of 0.25 in. If the valve A is closed and the water pre
    10·1 answer
  • At the instant shown, slider block B is moving with a constant acceleration, and its speed is 150 mm/s. Knowing that after slide
    13·1 answer
  • The elastic settlement of an isolated single pile under a working load similar to that of piles in the group it represents, is p
    8·1 answer
  • The velocity of a point mass that moves along the s-axis is given by s' = 40 - 3t^2 m/s, where t is in seconds. Find displacemen
    7·1 answer
  • Steam flows steadily through an adiabatic turbine. The inlet conditions of the steam are 10 MPa, 450°C, and 80 m/s, and the exit
    11·1 answer
  • Air at 300 K and 100 kPa steadily flows into a hair dryer having electrical work input of 1500 W. Because of the size of the air
    6·2 answers
  • The organic acid, ACOOH, reacts reversibly with the alcohol BOH, to form the ester ACOOB according to the stoichiometric equatio
    6·1 answer
  • How do you connect several springs to increase the equivalent stiffness? What is one example from industry or other real-life si
    7·1 answer
  • The current at resonance in a series L-C-R circuit is 0.2mA. If the applied voltage is 250mV at a frequency of 100 kHz and the c
    9·1 answer
  • Can somebody help me with that
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!