In the field of construction, welding is

Annealing is a process by which steel is reheated and then cooled to make it less brittle. Consider the reheat stage for a 100-m

kodGreya [7K]

Complete question is;

Annealing is a process by which steel is reheated and then cooled to make it less brittle. Consider the reheat stage for a 100 mm thick plate (ρ = 7830 kg/m3, Cp = 550 J/kg K, k = 48 W/m K). The plate initially is at 200 °C and is to be heated to a minimum temperature of 550 °C. Heating is effected in a gas-fired furnace where the products of combustion at T∞ = 800 °C maintain a convection heat transfer coefficient of h = 250 W/m.K on both surfaces of the plate. How long should the plate be left in the furnace?

Answer:

860 seconds

Explanation:

We are given;

Initial Temperature; Ti = 200 °C

Minimum Temperature; T_i = 550 °C

T∞ = 800 °C

convection coefficient; h = 250 W/m².K

ρ = 7830 kg/m³

Cp = 550 J/kg K

k = 48 W/m K

Plate thickness = 100mm

Thus,L = 100/2 = 50mm = 0.05 m

Let's find the biot number from the formula;

Bi = hL/K

Bi = (250 × 0.05)/48

Bi = 0.2604

Now, lowest temperature in the slab is given as;

θ_o = (T_o - T∞)/(T_i - T∞)

θ_o = (550 - 800)/(200 - 800)

θ_o = 0.4167

Now, from online tables calculation, we can find the root of the biot number.

Thus, root of the biot number Bi = 0.2604 is;

ζ1 = 0.488 rad

Also, C1 is gotten as 1.0396

Now,formula for thermal diffusivity is;

α = k/ρc

α = 48/(7830 × 550)

α = 1.115 × 10^(-5) m²/s

Also, from online tables, f(ζ1) = 0.401

Thus, we can find the time the plate should the plate be left in the furnace from;

-(ζ1)²(αt/L²) = In 0.401

-(ζ1)²(αt/L²) = -0.9138

t = (-0.9138 × 0.05²)/-(0.488² × 1.115 × 10^(-5))

t ≈ 860 s

8 0

3 years ago

Consider a mixing tank with a volume of 4 m3. Glycerinflows into a mixing tank through pipe A with an average velocity of 6 m/s,

Svetach [21]

This question is incomplete, the complete question as well as the missing diagram is uploaded below;

Consider a mixing tank with a volume of 4 m³. Glycerin flows into a mixing tank through pipe A with an average velocity of 6 m/s, and oil flow into the tank through pipe B at 3 m/s. Determine the average density of the mixture that flows out through the pipe at C. Assume uniform mixing of the fluids occurs within the 4 m³ tank.

Take $p_o$ = 880 kg/m³ and $p_{glycerol$ = 1260 kg/m³

Answer:

the average density of the mixture that flows out through the pipe at C is 1167.8 kg/m³

Explanation:

Given that;

Inlet velocity of Glycerin, $V_A$ = 6 m/s

Inlet velocity of oil, $V_B$ = 3 m/s

Density velocity of glycerin, $p_{glycerol$ = 1260 kg/m³

Density velocity of glycerin, Take $p_o$ = 880 kg/m³

Volume of tank V = 4 m

from the diagram;

Diameter of glycerin pipe, $d_A$ = 100 mm = 0.1 m

Diameter of oil pipe, $d_B$ = 80 mm = 0.08 m

Diameter of outlet pipe $d_C$ = 120 mm = 0.12 m

Now, Appling the discharge flow equation;

$Q_A + Q_B = Q_C$

$A_Av_A + A_Bv_B = A_Cv_C$

π/4 × ( $d_A$ )² $v_A$ + π/4 × ( $d_B$ )² $v_B$ = π/4 × ( $d_C$ )² $v_C$

we substitute

π/4 × (0.1 )² × 6 + π/4 × (0.08 )² × 3 = π/4 × (0.12)² $v_C$

0.04712 + 0.0150796 = 0.0113097 $v_C$

0.0621996 = 0.0113097 $v_C$

$v_C$ = 0.0621996 / 0.0113097

$v_C$ = 5.5 m/s

Now we apply the mass flow rate condition

$m_A + m_B = m_C$

$p_{glycerin}A_Av_A + p_0A_Bv_B = pA_Cv_C$

so we substitute

1260 × π/4 × (0.1 )² × 6 + 880 × π/4 × (0.08 )² × 3 = p × π/4 × (0.12)² × 5.5

1260 × 0.04712 + 880 × 0.0150796 = p × 0.06220335

59.3712 + 13.27 = 0.06220335p

72.6412 = 0.06220335p

p = 72.6412 / 0.06220335

p = 1167.8 kg/m³

Therefore, the average density of the mixture that flows out through the pipe at C is 1167.8 kg/m³

4 0

3 years ago

Explain all the characteristics of computer<br>

Sedaia [141]

They are as follows-

Speed
Accuracy
Storage
Versatility
Diligence
Automation
Reliability
Power of Remembering

Let us understand each characteristic in brief:-

Speed – Speed of a computer means the time it takes to complete any given task. The computer works at a very lightning speed. For example, a computer takes a second to calculate 3 million calculations rather than a human which takes years. Hence nowadays the speed of the computer is measured in terms of microseconds, Nanoseconds, and even in Pico seconds instead of seconds or milliseconds.

Accuracy – The computers are programmed and designed in such a manner that their results are almost 100% accurate. It performs all the tasks with the same accuracy. There are very few chances of uncertainty in results and even though an error occurs, it can happen either due to wrong input data or unreliable programs by a programmer. Such errors are referred to as Garbage In Garbage Out (GIGO) which means, if you provide wrong instructions to the computer then you get wrong results.

Versatility – Along with being accurate and diligent a computer is also a versatile device. It can perform several types of tasks at a time if they are reduced to a certain set of logical steps. A computer can be used for many purposes at different places such as booking air and rail tickets, weather forecasting, listening to music, and playing games. Also at a time, one can pay his utility bills and can make a monthly budget too. It can prepare documents, data sheets and also can make models of houses, dams, etc.
Diligence – The ability of a computer to perform tasks without getting tired is known as diligence. Computers are highly reliable, they do not get fed up, exhausted, or lack concentration. They can work for hours and hours unlike humans and can give accurate or error-free results. For example, humans will start feeling tired after 2 -3 hours and will lack concentration whereas a computer will keep on working until the results are achieved.
Automation – Automation means working automatically. A computer can work on its own without the intervention of the person using it. Programs can be made for the computer to perform the task and based on the sequence it executes the tasks and gives accurate results. In case an error occurs, it gives error messages too and registers the logs.
Reliability – High reliability of a computer depends on low failure rate and easy maintenance. The results given out by the computer are reliable as the accuracy is almost 100%.
Power of Remembering – The computer has the power of storing data or information for several years. It cannot lose the data on its own. A person can retrieve the data whenever required and the data remains the same after a number of years also. It gives the freedom to the user to decide on how much data to store and how much to remove.

5 0

3 years ago

How could you nonverbally express interest while speaking to a customer in person? Check all of the boxes that apply.

JulijaS [17]

Answer: B,D,E, and G or 2,4,5,7

Explanation: Hope this helps Trust the answer I took the test!

5 0

3 years ago

The constant A in Equation 17.2 is 12π4 R/5(θD) 3 where R is the gas constant and θD is the Debye temperature (K). Estimate θD f

kirill115 [55]

Answer:

The Debye temperature for aluminum is 375.2361 K