All categories

2 years ago

In homes today, what is behind the reason for flashover fires occurring much more rapidly than in the past generations?

Engineering

1 answer:

garik1379 [7]2 years ago

6 0

Answer:

One of the reasons why flashover fires are more prevalent today than it was in the past is that homes and furniture today are made from materials that are far more combustible than those of previous years.

Explanation:

A flashover fire is the rapid ignition and combustion of all flammable materials in an enclosed vicinity in a very short period of time.

Thirty years ago, the average escape time from a house that was on fire is about sixteen and fifty seconds...that would be approximately seventeen minutes. Presently that figure is down to four minutes.

One of the reasons identified is that the internal and external appurtenances especially furniture in use today are more combustible than those of previous years. That is, as they burn, they produce more heat and disintegrate faster.

The reason identified for this is, old houses were made of more natural materials such as real wood etc whilst the furniture and curtains in modern houses are mostly from synthetic materials.

Cheers

You might be interested in

Determine the nature of the following cycle (reversible, irreversible, or impossible): a refrigeration cycle draws heat from a c

vlabodo [156]

Answer:

Impossible.

Explanation:

The ideal Coefficient of Performance is:

$COP_{i} = \frac{250\,K}{300\,K-250\,K}$

$COP_{i} = 5$

The real Coefficient of Performance is:

$COP_{r} = \frac{950\,kJ-70\,kJ}{70\,kJ}$

$COP_{r} = 12.571$

Which leads to an absurds, since the real Coefficient of Performance must be equal to or lesser than ideal Coefficient of Performance. Then, the cycle is impossible, since it violates the Second Law of Thermodynamics.

6 0

2 years ago

Anaircraft component is fabricated from an aluminum alloy that has a plane-strain fracture toughness of 40 MPa 1/2.It has been d

navik [9.2K]

Answer:

Yes, fracture will occur since toughness (42.4 MPa) is greater than the toughness of the material, 40MPa

Explanation:

Given

Toughness, k = 40Mpa

Stress, σ = 300Mpa

Length, l = 4mm = 4 * 10^-3m

Under which fracture occurred (i.e., σ= 300 MPa and 2a= 4.0 mm), first we solve for parameter Y (The dimensionless parameter)

Y = k/(σπ√a)

Where a = ½ of the length in metres

Y = 40/(300 * π * √(4/2 * 10^-3))

Y = 1.68 ---- Approximated

To check if fracture will occur of not; we apply the same formula.

Y = k/(σπ√a)

Then we solve for k, where

σ = 260Mpa and a = ½ * 6 * 10^-3

So,.we have

1.68 = k/(260 * π * √(6*10^-3)/2)

k = 1.68 * (260 * π * (6*10^-3)/2)

k = 42.4 MPa --- Approximately

Therefore, fracture will occur since toughness (42.4 MPa) is greater than the toughness of the material, 40 MPa

7 0

2 years ago

Read 2 more answers

"geophysical exploration definition"

Strike441 [17]

Answer:

Exploration geophysics is an applied branch of geophysics and economic geology, which uses physical methods, such as seismic, gravitational, magnetic, electrical and electromagnetic at the surface of the Earth to measure the physical properties of the subsurface, along with the anomalies in those properties

7 0

2 years ago

Read 2 more answers

Can someone write a 2 page essay about Engineering

xxMikexx [17]

Answer:

In the 21st if we are to look around in our society, we will see most of it displays several marvels of engineering, which shows why it is an important discipline. The field of engineering consists of a vast sea of knowledge whose boundary is infinite. And through the discoveries and breakthroughs made by engineers almost every day, the expertise and information keep growing. Society has given engineers various nicknames like problem solvers, organizers, designers, human calculators, and communicators because of the highly creative activities. The most amusing fact about the engineering discipline is that the evidence of its applications dates back to the ancient stone ages. The discoveries made in those primitive days were like the invention of wheels, carts, the building of huts, pulleys, etc.

There has been a significant role in engineering since when human civilization had started. The evidence from ancient Harappa and Mohenjodaro civilizations show that it had a planned layout of the street grids along with equal-sized buildings, structural city division for commercial purposes, well-planned drainage system, etc., which are all considered to be very advanced civil engineering activities for the period of the civilization.As we proceed further down the timeline, we have witnessed several other civil engineering wonders like the great pyramids, Great Wall of China, Taj Mahal, etc. Engineers from places like Japan, where earthquakes are common, found a way to withstand natural disasters by building shock-proof structures, and such inventions have saved a million lives. Ancient Greeks made machines for civilians, military, and as well as commercial purposes.

Transportation is another great wonder in the contributions of engineering made to humankind. Using transportation devices, we have voyaged into outer space and reached the moon as well. And vehicles are such inventions which have certainly made the commute a whole lot easier.

Earlier, the engineering field only consisted of core branches that specialized in individual departments of work, and the divisions were Mechanical, Electrical, and Civil. But eventually, with much more advanced and discoveries in the field of technology and a combination of engineering with other areas of study, some more branches of course under the engineering field became popular. Among them, a few Engineering branches to name are Computer, Aerospace, IT, Electronics and Communication, Electronics and Instrumentation, Biomedical, Chemical, Textile, Petroleum, Food Technology, etc.

In an age where society is highly dependent on technology, especially on electronic devices and the internet, a modern-day software engineer is expected to be tech-savvy and able to solve a range of various problems related to commuting programs. They are also likely to help verify designs and predict structures/devices’ behavior in different environments.

The main objective of engineers and engineering is to benefit humankind by making life and living easier. The contributions of engineering cannot be summed up into a few words. Still, the right way to respect their immense role in society is by recognizing and using their inventions responsibly. Engineering always has and will continue to strive to lift our living standards through sustainable developments and considering conditions to protect our Earth’s environment at all costs.

Explanation:

3 0

2 years ago

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

saveliy_v [14]

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:

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

5 0

2 years ago