Refrigeration and Air Conditioning Technology (MindTap Course List)
8th Edition
ISBN: 9781305578296
Author: John Tomczyk, Eugene Silberstein, Bill Whitman, Bill Johnson
Publisher: Cengage Learning
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Textbook Question
Chapter 42, Problem 11RQ
If a wall is made up of four different materials, all layered one on top of the other, how will the total R-value of the wall be determined?
A. By the one material with the highest R-value
B. By the one material with the lowest R-value
C. By averaging the R-values of the materials
D. By adding the R-values of the materials together
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Children asked their parent for an ice cream after dinner. They eat their ice cream as long as it does not melt and its structure is solid. The parent drove to buy an ice cream in the grocery store. The ice cream is sold in family sized package. The store keeps the ice cream packages in the freezer until it is sold. The packages are made from polystyrene material and their size is 0.2´0.1´0.07 m3 . The store freezer temperature is kept at -10o C. The ice cream has a solid structure (not melting) as long as its temperature remains below 0o C. The time it takes to reach back from the store is 20 minutes Will the kids eat the ice cream at home? Ice cream properties: k = 2.2 W/mo C, C = 1800 J/kgo C, r = 900 kg/m3 and h = 10 W/m2oC.
- Please select the correct answers according to the given figure for the elastic behaviour of steel and aluminium
I. The elastic modulus of steel is about three times higher than the aluminum
II. Aluminum deforms elastically three times as much as does steel
III. Steel will show much smaller changes in dimensions
IV. Steel is three times stiffer than the aluminum
V. Aluminum is three times stiffer than the steel
50,000
40,000
Steel
Aluminum
30,000
20,000
10,000
0.
0.001
0.002
0.003
0.004
0.005
Engineering strain e (in./in.)
Engineering stress S (psi)
Which of the following statements are true?
Select one or more:
a.
Dislocations and defects make thermal transfer easy due to plastic deformation
b.
Starting at room temperature, the heat conductivity of ceramics goes generally up with increasing temperature
c.
Starting at room temperature, the heat conductivity of ceramics goes generally down with increasing temperature
d.
Dislocations and defects make thermal transfer difficult due to phonon scattering
e.
Heat transfer in solids occurs mainly by waves of atoms vibrating
f.
Heat transfer in solids occurs mainly by phonons
Chapter 42 Solutions
Refrigeration and Air Conditioning Technology (MindTap Course List)
Ch. 42 - An oversized air-conditioning system will A. cost...Ch. 42 - Methods used to calculate the heat gain and heat...Ch. 42 - An exterior wall A. separates a conditioned...Ch. 42 - A partition wall A. separates a conditioned...Ch. 42 - As the temperature differential across a panel...Ch. 42 - The typical indoor design temperature used for...Ch. 42 - The typical indoor design temperature used for...Ch. 42 - If a heating system was being designed for use in...Ch. 42 - If an air-conditioning system was being designed...Ch. 42 - If the R-value of a construction material is 2.0,...
Ch. 42 - If a wall is made up of four different materials,...Ch. 42 - Prob. 12RQCh. 42 - All of the following are taken into account on a...Ch. 42 - How much heat is lost through a 3' 5' single-pane...Ch. 42 - Which of the following is(are) true regarding a...Ch. 42 - Which of the following is(are) true regarding the...
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- If the R-value of a construction material is 2.0, what isits U-value? A. 0.25 B. 0 50 C. 1.0 D. 2.0arrow_forwardChoose the wrong statement. Heat transfer by conduction depends on thickness of the material temperature difference of the material type of material cross-sectional area of the material none of the abovearrow_forward7. Which of the following is false: a. The coefficient of thermal expansion is larger if the bond energy is smaller b. Ceramics are generally ionic bonding c. Van der Waals bonding is generally stronger than covalent bonding d. The free electrons in metallic bonding is reason for electrical conductivity 8. Which of the following is true: a. Polymers are generally denser than ceranmics b. Young's modulus of ceramics are similar to polymers c. Composites have higher tensile strength than metals d. Ceramics have low resistance to fracture than metalsarrow_forward
- PLS ANSWER THIS QUESTION HERE ARE THE CHOICES: A. 1.008 cm b. 0.751 cm c. 1.725 cm d. 0.623 cm e. none of the abovearrow_forwardPlease answer this question. Make sure to explain your answer step-by-step so that I can understand it clearly, and Please note that this is not a marked question,arrow_forwardinclude diagram.arrow_forward
- Two wires of equal lengths, one Aluminum, and the other steel, were stretched the same amount under an applied load P. The modulus of elasticity for Aluminum and steel are 80 GPa, 200 GPa respectively, what is the diameter ratio of the Aluminum wire with respect to steel? Aluminum alloy wire Steel wire 'P P Select one: a. 2.50 b. 1.63 O c. 0.40 O d. 1.58 O e. 0.63 O f. Nonearrow_forwardPlease answer these three questions. Thank you! A material has a Poisson’s ratio of -0.2 . Which of the following is true? a. Strain is always compressive regardless of the force applied. b. Lateral and longitudinal strains will have the same sign c. Lateral strain is five times the longitudinal strain. d. The material is ductile and has a high modulus of elasticity. Consider a rod that can carry a maximum stress equal to 200 MPa. If it is to be designed to have a factor of safety against failure equal to 1.5, then the maximum stress that the rod should experience when loaded is nearest to ______ a. 133 MPa b. 150 MPa c. 300 MPa d. 267 MPa Which of the following statements is FALSE? A. The modulus of elasticity of a material can vary between axes. B. The modulus of rigidity can be determined from the shear stress-strain diagram. C. The Poisson’s Ratio can be used in calculating the new diameter in the Necking Region of the stress strain diagram. D. Most materials…arrow_forwardANSWER ASAAAP EVERYTHINGarrow_forward
- For problems 1 and 2, refer to the figure below 3.5m 12.0m 6m -3.5m 1. A room is shown in the figure above. Dark gray shaded wall are made up of plaster 25.4 mm thick W with k = 0.42 and light gray shaded are m-'c' W building brick 76 mm thick with k = 0.4 m-°C The temperatures are: T1-34°C, T2=31°C, and T3-20°C. Film conductance of air moving outside W is h = 25 Determine the total heat m² - °C transfer between the walls only. (Assume no radiative heat transfer)arrow_forwardTwo wires of equal lengths, one Aluminum, and the other steel, were stretched the same amount under an applied load P. The modulus of elasticity for Aluminum and steel are 70 GPa, 210 GPa respectively, what is the diameter ratio of the Aluminum wire with respect to steel? Aluminum alloy wire Steel wire P Select one: a. 0.58 O b. 3.00 Ос. 1.73 O d. 0.33 O e. 1.64 O f. Nonearrow_forwardThe resistance offered by a material to maintain the equilibrium is also called as Young’s modulus Strain Stress Internal energyarrow_forward
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