Ask question

Ask question

All categories

1 month ago

12

Q1) A vapor-compression refrigeration system operates on the cycle of Fig. 9.1. The refrigerant is 1,1,1,2-Tetrafluoroethane. Gi

ven that the evaporation T = 4°C, the condensation T = 34°C, η(compressor) = 0.76, and the refrigeration rate = 1200 kJ⋅s−1, determine the circulation rate of the refrigerant, the heat-transfer rate in the condenser, the power requirement, the coefficient of performance of the cycle, and the coefficient of performance of a Carnot refrigeration cycle operating
between the same temperature levels.

1 answer:

alisha [2.9K]1 month ago

4 0

Answer:

i) 0.5071 kg/s

ii) -1407.1 kJ/kg

iii) 204.05 kW

iv) 5.881

v) 9.238

Explanation:

Given Data:

evaporation temperature (T) = 4°C = 277.15 K

Condensation Temperature (T) = 34°C = 307.15 K

n (compressor efficiency) = 0.76

refrigeration rate = 1200 kJ/s

i) to find the circulation rate of the refrigerant

m = $\frac{Q}{H2 - H1}$ = $\frac{Q}{H2 - H4\\}$ ------- 1

Q = 1200 kJ/s

H2 = entropy at step 2 = 2508.9 (kJ/kg) (obtained from Table F)

H4 = entropy at step 4 = 142.4 (kJ/kg)

back to equation 1

m (circulation rate of refrigerant) = 0.5071 kg/s

ii) heat transfer rate in the condenser

Q = m (H4 - H3)

= 0.5071 (142.4 - 2911.27)

= -1407.1 kJ/kg

where H3 = H2 + ΔH23 = 2911.27 (kJ/kg) (as calculated)

iii) power requirement

w = m * ΔH23

= 0.5071 (kg/s) * 402.37 (kJ/kg) = 204.05 kW

where: ΔH23 = $\frac{H'3 - H2 }{0.76}$ = $\frac{2814.7-2508.9}{0.76}$ = 402.37 (kJ/kg)

iv) coefficient of performance of a cycle

W = Qc / w

= 1200 kJ/s / 204.05 kW

= 5.881

v) coefficient of performance of a Carnot refrigeration cycle

$w_{carnot} = \frac{T2}{T4 - T2}$

= 277.15 / (307.15 - 277.15)

= 9.238

You might be interested in

How many atoms of Mg are present in 97.22 grams of Mg?

VMariaS [2998]

Answer: The correct choice is (b).

Explanation:

We have the mass of Magnesium at 97.22 g, and the molar mass of Magnesium is 24.305 g/mol.

Therefore, the calculation for the number of moles is as follows.

Number of moles = $\frac{mass given in grams}{Molar mass}$

= $\frac{97.22 g}{24.305 g/mol}$

= 4 mol

Additionally, it is known that one mole contains $6.023 \times 10^{23}$ atoms/mol. Thus, we calculate the total number of atoms in 4 moles as follows.

$4 mol \times 6.023 \times 10^{23} atoms/mol$

= $24.08 \times 10^{23}$ atoms

or, = $2.408 \times 10^{23}$ atoms

Hence, we conclude that in 97.22 grams of Magnesium, there are $2.408 \times 10^{23}$ atoms.

7 0

2 months ago

One tank of gold fish is fed the normal amount of food once a day. A second tank is fed twice a day. A third tank is fed four ti

Tems11 [2777]

The inquiry is incomplete; here is the full question:

One tank of goldfish receives the standard amount of feeding once daily, a second tank is given two feedings a day, and a third tank is fed four times daily throughout a six-week experiment. The body fat of the fish is recorded every day.

Independent Variable-

Dependent Variable-

Constants

Control Group-

Answer:

A) The quantity of food given to the goldfish

B) The body fat of the goldfish

C) -Type of fish in the experiment (goldfish)

Time period for feeding the fish (six weeks)

Shape and size of the tanks

D) group of goldfish receiving the standard feeding amount

Explanation:

The objective of the experiment is to assess how the quantity of food affects the body fat of goldfish. Consequently, the amount of food serves as the independent variable while the body fat acts as the dependent variable.

The control group is the one given the standard feeding amount (once daily). All subjects are goldfish, fed over a six-week duration, with all tanks being the same shape and size, establishing the constants in the research.

4 0

2 months ago

Which of the following statements describe physical properties and which describe chemical properties? (a) Iron has a tendency t

Anarel [2989]

Answer:

Explanation:

a) Iron has the tendency to undergo rusting -- this is a chemical property as it involves a reaction with water and air.

b) Precipitation in industrialized areas often has an acidic nature -- this is also a chemical property due to its interaction with bases or metals.

c) Hemoglobin is red in color -- this is a physical property since it doesn't entail any chemical reactions.

d) When water is left out in sunlight, it evaporates gradually -- this is a physical property because the process can easily be reversed, classifying it as a physical change.

e) During photosynthesis, plants convert carbon dioxide into more complex molecules -- this demonstrates a chemical property since it involves chemical reactions.

8 0

2 months ago

The metallic radius of a potassium atom is 231 pm. What is the volume of a potassium atom in cubic meters?

Anarel [2989]

1 pm equals 10^{-10} cm. Therefore, 230 pm can be converted to 2.3 × 10^{-8} cm. Atoms are spherical in shape, and the volume of a sphere can be calculated using the formula 4/3πr³. Consequently, the atom's volume is calculated as 4/3π(2.3 × 10^{-8})³. Evaluating this gives 4/3 × (3.142 × 12.167 × 10^{-24}), which simplifies to approximately 5.096 × 10^{-23} cm³. Since 1 m³ is equal to 1,000,000 cm³, we find that the volume of the atom is 5.096 × 10^{-29} m³.

8 0

2 months ago

A solution is prepared by adding 1.43 mol of kcl to 889 g of water. the concentration of kcl is ________ molal. a solution is pr

VMariaS [2998]

A mixture is created by dissolving 1.43 mol of potassium chloride (KCl) in 889 g of water. The concentration of KCl works out to be 1.61 molal.
The amount of KCl is 1.43 mol
Water weighs 889 g
The molality can be calculated using the formula:
molality = moles of solute divided by kilograms of solvent
Since 1 kg equals 1000 g, 889 g is 0.889 kg.

Therefore, m = 1.43/0.889 = 1.61 molal.

7 0

2 months ago