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4 years ago

What is a ton of refrigeration?

Engineering

1 answer:

AURORKA [14]4 years ago

6 0

Explanation:

The unit refrigeration is generally is given in terms of tons.In refrigeration compressor consume some amount of work to produce the cooling effect with the help of evaporator and condenser.

In the simple words ton is the cooling load of refrigeration system.

1 ton = 3.5 KW

1 ton = 12,000 BTU/hr

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This is an essential safety procedure that protects workers from injury while working on or near electrical circuits and equipme

Mice21 [21]

Answer:

Option B

Lockout/ Tagout

Explanation:

lockout and tagout is a safety procedure used in most industries and work places. This ensures that during any maintenance work, that dangerous machines are properly shut off and not able to be started up again prior to the completion of maintenance or repair work.

The procedure includes:

1. Turns off and disconnects the machinery or equipment from its energy source(s) before performing service or maintenance.

2. The authorized employee(s) either lock or tag the energy-isolating device(s) to prevent the release of hazardous energy.

8 0

4 years ago

Air at 1 atm enters a thin-walled ( 5-mm diameter) long tube ( 2 m) at an inlet temperature of 100°C. A constant heat flux is ap

alexdok [17]

Answer:

heat rate = 7.38 W

Explanation:

Given Data:

Pressure = 1atm

diameter (D) = 5mm = 0.005m

length = 2

mass flow rate (m) = 140*10^-6 kg/s

Exit temperature = 160°C,

At 400K,

Dynamic viscosity (μ) = 22.87 *10^-6

Prandtl number (pr) = 0.688

Thermal conductivity (k) = 33.65 *10^-3 W/m-k

Specific heat (Cp) = 1.013kj/kg.K

Step 1: Calculating Reynolds number using the formula;

Re = 4m/πDμ

= (4*140*10^-6)/(π* 0.005*22.87 *10^-6)

= 5.6*10^-4/3.59*10^-7

= 1559.

Step 2: Calculating the thermal entry length using the formula

Le = 0.05*Re*Pr*D

Substituting, we have

Le = 0.05 * 1559 * 0.688 *0.005

Le = 0.268

Step 3: Calculate the heat transfer coefficient using the formula;

Nu = hD/k

h = Nu*k/D

Since Le is less than given length, Nusselt number (Nu) for fully developed flow and uniform surface heat flux is 4.36.

h = 4.36 * 33.65 *10^-3/0.005

h = 0.1467/0.005

h = 29.34 W/m²-k

Step 4: Calculating the surface area using the formula;

A = πDl

=π * 0.005 * 2

=0.0314 m²

Step 5: Calculating the temperature Tm

For energy balance,

Qc = Qh

Therefore,

H*A(Te-Tm) = MCp(Tm - Ti)

29.34* 0.0314(160-Tm) = 140 × 10-6* 1.013*10^3 (Tm-100)

0.921(160-Tm) = 0.14182(Tm-100)

147.36 -0.921Tm = 0.14182Tm - 14.182

1.06282Tm = 161.542

Tm = 161.542/1.06282

Tm = 151.99 K

Step 6: Calculate the rate of heat transferred using the formula

Q = H*A(Te-Tm)

= 29.34* 0.0314(160-151.99)

= 7.38 W

the Prandtl number using the formula

5 0

3 years ago

Select three types of lines that engineers use to help represent the shape of a design in a sketch.

Vikki [24]

Hidden lines

Used to describe the in shown lines (like diagonals inside cubes)

Extension lines:-

Used to explain the expansion of structures like building

Object lines

Used to describe the structure of objects and the lining to show borders

7 0

3 years ago

An uncharged capacitor is connected to a resistor and a battery. Choose what happens to current, potential difference and charge

Ilya [14]

Answer:

The charge on the plates will increase with time

The potential difference across the capacitor starts with zero and then increases gradually to a maximum value

The current through the circuit starts high and then drops exponentially

Explanation:

<u>Case : An uncharged capacitor is connected to a resistor and a battery in a closed circuit.</u>

The charge on the plates will increase with time

applying this equation : Q = $Q_{0} [ 1 - e^{\frac{-t}{RC} } ]$ as the value of (t) increases the value of Q increases i.e. charge on the plates

The potential difference across the capacitor starts with zero and then increases gradually to a maximum value

applying this equation : V = $V_{0} [ 1 - e^{\frac{-t}{RC} } ]$

The current through the circuit starts high and then drops exponentially

current : I = $I_{0} e^{\frac{-t}{RC} }$

6 0

3 years ago

A 220-V electric heater has two heating coils that can be switched such that either coil can be used independently or the two ca

Nana76 [90]

Answer:

The resistances of both coils are 131.7 Ω and 29.64 Ω.

Explanation:

Since, there are two coils, they can be used independently or in series or parallel. The power is given as:

Power = P = VI

but, from Ohm's Law:

V = IR

I = V/R

therefore,

P = V²/R

R = V²/P

Hence, the resistance (R) and (P) are inversely proportional. Therefore, the maximum value of resistance will give minimum power, that is, 300 W. And the maximum resistance will be in series arrangement, as in series the total resistance gets higher than, any individual resistance.

Therefore,

Rmax = V²/Pmin = R1 + R2

R1 + R2 = (220 V)²/300 W

R1 + R2 = 161.333 Ω ______ en (1)

Similarly, the minimum resistance will give maximum power. And the minimum resistance will occur in parallel combination. Because equivalent resistance of parallel combination is less than any individual resistance.

Therefore,

(R1 R2)/(R1 + R2) = (220 V)²/2000 W

using eqn (1), we get:

(R1 R2) / 161.333 Ω = 24.2 Ω

R1 R2 = 3904.266 Ω²

R1 = 3904.266 Ω²/R2 _____ eqn (2)

Using this value of R1 in eqn (1), we get:

3904.266/R2 +R2 = 161.333

(R2)² - 161.333 R2 +3904.266 = 0

Solving this quadratic eqn we get two values of R2 as:

R2 = 131.7 Ω OR R2 = 29.64 Ω

when ,we substitute these values in eqn (1) to find R1, we get get the same two values as R2, alternatively. This means that the two coils have these resistance, and the order does not matter.

<u>Therefore, the resistance of both coils are found to be 131.7 Ω and 29.64 Ω</u>

7 0

3 years ago