All categories

3 years ago

Explain the new Beryllium Standard

1 answer:

5 0

The new rule lowers the Permissible Exposure Limits (PELs) and requires that employers use feasible engineering controls – such as ventilation along with work practice controls – to reduce workers' inhalation exposure to beryllium

You might be interested in

A square isothermal chip is of width w = 5 mm on a side and is mounted in a substrate such that its side and back surfaces are w

adelina 88 [10]

Answer:

Maximum allowable chip power is 0.35 W

Explanation:

This question is incomplete. The complete question is

A square isothermal chip is of width w = 5 mm on a side and is mounted in a substrate such that its side and back surfaces are well insulated; the front surface is exposed to the flow of a coolant at t[infinity] = 15°c. from reliability considerations, the chip temperature must not exceed t = 85°c. f the coolant is air and the corresponding convection 200 w/m2 k, what is the maximum allowable chip power?

<u>ANSWER:</u>

The heat transfer through convection, we have the equation:

q = hA(T - T∞)

where,

q = power transfer through convection = ?

h = convection coefficient = 200 W/m²K

A = Area of convection surface = (0.005 m)² = 0.000025 m²

T = Chip surface temperature = 85° C

T∞ = Fluid temperature = 15° C

Therefore,

q = (200 W/m².K)(0.000025 m²)(85° C - 15° C)

Since, difference in temperature is same on both Celsius and kelvin scale. Therefore, Celsius is written as kelvin for difference and they shall be cancelled.

3 0

4 years ago

An automobile tire with a volume of 0.8 m3 is inflated to a gage pressure of 200 kPa. Calculate the mass of air in the tire if t

saveliy_v [14]

Answer:

2.83 kg

Explanation:

Given:

Volume, V = 0.8 m³

gage pressure, P = 200 kPa

Absolute pressure = gage pressure + Atmospheric pressure

= 200 + 101 = 301 kPa = 301 × 10³ N/m²

Temperature, T = 23° C = 23 + 273 = 296 K

Now,

From the ideal gas equation

PV = mRT

Where,

m is the mass

R is the ideal gas constant = 287 J/Kg K. (for air)

thus,

301 × 10³ × 0.8 = m × 287 × 296

m = 2.83 kg

3 0

4 years ago

Air at 400 kPa, 980 K enters a turbine operating at steady state and exits at 100 kPa, 670 K. Heat transfer from the turbine occ

AURORKA [14]

Answer:

a) $w_{out} = 281.55\,\frac{kJ}{kg}$ , b) $s_{gen} = 0.477\,\frac{kJ}{kg\cdot K}$

Explanation:

a) The process within the turbine is modelled after the First Law of Thermodynamics:

$-q_{out} - w_{out} + h_{in}-h_{out} = 0$

$w_{out} = h_{in} - h_{out}-q_{out}$

$w_{out} = c_{p}\cdot (T_{in}-T_{out})-q_{out}$

$w_{out} = \left(1.005\,\frac{kJ}{kg\cdot K}\right)\cdot (980\,K-670\,K)-30\,\frac{kJ}{kg}$

$w_{out} = 281.55\,\frac{kJ}{kg}$

b) The entropy production is determined after the Second Law of Thermodynamics:

$-\frac{q_{out}}{T_{surr}} + s_{in}-s_{out} + s_{gen} = 0$

$s_{gen} = \frac{q_{out}}{T_{surr}}+s_{out}-s_{in}$

$s_{gen} = \frac{q_{out}}{T_{surr}}+c_{p}\cdot \ln\left(\frac{T_{out}}{T_{in}} \right)$

$s_{gen} = \frac{30\,\frac{kJ}{kg} }{315\,K} + \left(1.005\,\frac{kJ}{kg\cdot K} \right)\cdot \ln\left(\frac{980\,K}{670\,K} \right)$

$s_{gen} = 0.477\,\frac{kJ}{kg\cdot K}$

3 0

3 years ago

You should be extra careful during the hours of sunrise, sunset, and nighttime because _____. A. of increased law enforcement ac

torisob [31]

Answer:

B, its the only valid answer

5 0

4 years ago

The objective of a properly proportioned concrete mix are: a.__________________________________________________________ b.______

sukhopar [10]

Answer:

The objective of a properly proportioned concrete mix are:

To produce the combination of cementitious material, water, and aggregate that meets the requirements of a particular structure, portion of a structure, or series of structures at least cost.
To produce concrete of the specified properties.
To produce a satisfactory of end product, such as beam, column or slab as economically as possible.

Cheers!

4 0

3 years ago

Read 2 more answers