What’s the answer please help

What does the air change rate represent?

Juli2301 [7.4K]

Answer and Explanation:

The removal or addition of air volume to the space is the air change rate
The rate of air change is positive when air volume is added to the space and the rate of air change is negative when air volume is removed from the space.
The standard built home has a 0.5 to 1 of air change rate.
The rate of air change is dependent on the building (how the building form)

3 0

3 years ago

A Carnot refrigeration cycle absorbs heat at -12 °C and rejects it at 40 °C. a)-Calculate the coefficient of performance of this

tresset_1 [31]

Answer:

a)COP=5.01

b) $W_{in}=2.998$ KW

c)COP=6.01

d) $Q_R=17.99 KW$

Explanation:

Given

$T_L$ = -12°C, $T_H$ =40°C

For refrigeration

We know that Carnot cycle is an ideal cycle that have all reversible process.

So COP of refrigeration is given as follows

$COP=\dfrac{T_L}{T_H-T_L}$ ,T in Kelvin.

$COP=\dfrac{261}{313-261}$

a)COP=5.01

Given that refrigeration effect= 15 KW

We know that $COP=\dfrac{RE}{W_{in}}$

RE is the refrigeration effect

So

5.01= $\dfrac{15}{W_{in}}$

b) $W_{in}=2.998$ KW

For heat pump

So COP of heat pump is given as follows

$COP=\dfrac{T_h}{T_H-T_L}$ ,T in Kelvin.

$COP=\dfrac{313}{313-261}$

c)COP=6.01

In heat pump

Heat rejection at high temperature=heat absorb at low temperature+work in put

$Q_R=Q_A+W_{in}$

Given that $Q_A=15$ KW

We know that $COP=\dfrac{Q_R}{W_{in}}$

$COP=\dfrac{Q_R}{Q_R-Q_A}$

$6.01=\dfrac{Q_R}{Q_R-15}$

d) $Q_R=17.99 KW$

5 0

3 years ago

HEY Y'ALL!!! WILL GIVE BRAINLEST AND THANKS+A LOT OF POINTS!!!!! So in class our teacher wants to help us think out of the box m

Elden [556K]

Answer:

2) phone

3) snake

Explanation:

NO EXPLANATION

5 0

3 years ago

Read 2 more answers

State two main consumers of electricity transmitted at low frequency Calculate the primary voltage of a transformer if the prima

bagirrra123 [75]

Answer:

1) a. Customers requiring AC electric power transmission for powering remote devices which may include a subsea transmission system where power is distributed to subsea devices

b. Customers that utilize commutator-type motors

2) The primary voltage is 150 volts

Explanation:

The parameters given are;

Number of primary winding, $N_p$ = 50 turns

Number of secondary winding, $N_s$ = 150 turns

Voltage in secondary winding, $V_s$ = 450 volts

Voltage in primary winding = $V_p$

The relation between $N_p$ , $N_s$ , $V_s$ and $V_p$ is as follows;

$\dfrac{V_p}{V_s} = \dfrac{N_p}{N_s}$

Which gives;

$V_p = \dfrac{N_p \times V_s}{N_s}$

From which we have;

$V_p = \dfrac{50\times 450}{150} = 150 \ volts$

The primary voltage = 150 volts.

7 0

3 years ago

Read 2 more answers

A helical compression spring is to be made with oil-tempered wire ol 4 mm diameter with a spring index of C = 10 The spring is t

oee [108]

Answer:

a) the spring rate is 3.333 N/mm

b) the minimum hole diameter for the compression spring is 44 mm

c) the total number of coils needed is 11.6

d) the solid length is 50.4 mm

Explanation:

a)

to calculate the mean spring coil diameter, we take a look at the expression from the relation;

D = Cd

where C is the spring index ( 10 ) and d is the diameter of helical compression spring (4 mm)

so we substitute

D = 10 × 4 = 40 mm

Torsional stiffness G for the tempered wire with diameter 4 mm is 77.2 Gpa ( 77.2 × 10³ Mpa) ( obtained from Table: Mechanical properties of spring wires).

so when the spring is compressed, the spring force is given by the following expression(realtion)

Fs = k × ys

where ys is the deflection of the spring (15 mm) and k is the spring rate, Fs is the force (50N)

so we substitute

50N = k × 15mm

k = 50N / 15mm

k = 3.333 N/mm

∴ the spring rate is 3.333 N/mm

b)

to calculate the minimum hole diameter for the compression spring

Now the entire spring is within a hole in the ground, therefore the hole should have a diameter equal to the outer diameter of the spring.

so D₀ = D + d

and from our initial equations, the mean spring coil diameter D = 40mm and the diameter of the helical compression spring d = 4mm

we substitute

D₀ = 40 + 4

D₀ = 44 mm

the minimum hole diameter for the compression spring is 44 mm

c)

Consider the following relation to calculate the total number of coils needed

Na coils are actually working to support the springs structure and its all dependent on the cut at the edge (end). ( from the table, Nt elates to Na)

Na = (d⁴G) / 8D³k

where the mean spring coil diameter D = 40mm and the diameter of the helical compression spring d = 4mm, G is the torsional stiffness (77.2 × 10³ Mpa), the the spring rate k is 3.333 N/mm

so we substitute

Na = (4⁴(77.2 × 10³)) / ( 8(40³)(3.333))

Na = 19,763,200 / 1,706,496

Na = 11.6

the total number of coils needed is 11.6

d)

As the number of active coils and total number of coils are the same, we get the following relation;

Na = Nt

Nt which is also total number of coils

Now to calculate the solid length

Ls = d ( Nt + 1 )

so we substitute

Ls = 4 ( 11.6 + 1 )

Ls = 50.4 mm

the solid length is 50.4 mm

3 0

3 years ago