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A phase change, or transition, occurs when a substance undergoes a change in state on a molecular level. In most substances, changes in temperature or pressure result in a substance phase change. There are several processes of phase changes, including fusion, solidification, vaporization, condensation, sublimation and physical vapor deposition. A vapour compression cycle is used in most household refrigerators, refrigerator-freezers and freezers. The performance of the refrigerators heavily depends on the phase change properties of the refrigerant used. Thus, it is of primary importance to any industrial designer to have a good understanding of the phase change behaviour of substances which will allow them for design modifications and optimisations. In our problem, a cylinder is initially filled with saturated liquid-vapour mixture of R-134a (a common refrigerant) at a specified pressure, 250 kPa and vapour quality of 0.25. A constant heat input, Q, is transferred to the cylinder until the refrigerant vaporizes completely at constant pressure. By clearly stating your assumptions throughout, 1. Analytically describe the Fluid Mechanics and Thermodynamics working principles of refrigerators operating using a vapour compression cycle; 2. Determine the initial volume; 3. Determine the work done; 4. Determine the total heat transfer; 5. Show the process on a P-v diagram; 6. Discuss the desired properties of substances that are used as refrigerants in the industry and potential problems arising. Share your view on the potential usage of CO₂ as a refrigerant in commercial refrigerators.

A phase change, or transition, occurs when a substance undergoes a change in state on a molecular level. In most substances, changes in temperature or pressure result in a substance phase change. There are several processes of phase changes, including fusion, solidification, vaporization, condensation, sublimation and physical vapor deposition. A vapour compression cycle is used in most household refrigerators, refrigerator-freezers and freezers. The performance of the refrigerators heavily depends on the phase change properties of the refrigerant used. Thus, it is of primary importance to any industrial designer to have a good understanding of the phase change behaviour of substances which will allow them for design modifications and optimisations. In our problem, a cylinder is initially filled with saturated liquid-vapour mixture of R-134a (a common refrigerant) at a specified pressure, 250 kPa and vapour quality of 0.25. A constant heat input, Q, is transferred to the cylinder until the refrigerant vaporizes completely at constant pressure. By clearly stating your assumptions throughout, 1. Analytically describe the Fluid Mechanics and Thermodynamics working principles of refrigerators operating using a vapour compression cycle; 2. Determine the initial volume; 3. Determine the work done; 4. Determine the total heat transfer; 5. Show the process on a P-v diagram; 6. Discuss the desired properties of substances that are used as refrigerants in the industry and potential problems arising. Share your view on the potential usage of CO₂ as a refrigerant in commercial refrigerators.

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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R-134a 250 kPa Q Figure 4. Schematic of the liquid-vapour mixture vapourisation process at a constant pressure and heat input, Q.
Transcribed Image Text:R-134a 250 kPa Q Figure 4. Schematic of the liquid-vapour mixture vapourisation process at a constant pressure and heat input, Q.
A phase change, or transition, occurs when a substance undergoes a change in state on a molecular level. In most substances, changes in temperature or pressure result in a substance phase change. There are several processes of phase changes, including fusion, solidification, vaporization, condensation, sublimation and physical vapor deposition. A vapour compression cycle is used in most household refrigerators, refrigerator-freezers and freezers. The performance of the refrigerators heavily depends on the phase change properties of the refrigerant used. Thus, it is of primary importance to any industrial designer to have a good understanding of the phase change behaviour of substances which will allow them for design modifications and optimisations. In our problem, a cylinder is initially filled with saturated liquid-vapour mixture of R-134a (a common refrigerant) at a specified pressure, 250 kPa and vapour quality of 0.25. A constant heat input, Q, is transferred to the cylinder until the refrigerant vaporizes completely at constant pressure. By clearly stating your assumptions throughout, 1. Analytically describe the Fluid Mechanics and Thermodynamics working principles of refrigerators operating using a vapour compression cycle; 2. Determine the initial volume; 3. Determine the work done; 4. Determine the total heat transfer; 5. Show the process on a P-v diagram; 6. Discuss the desired properties of substances that are used as refrigerants in the industry and potential problems arising. Share your view on the potential usage of CO2 as a refrigerant in commercial refrigerators.
Transcribed Image Text:A phase change, or transition, occurs when a substance undergoes a change in state on a molecular level. In most substances, changes in temperature or pressure result in a substance phase change. There are several processes of phase changes, including fusion, solidification, vaporization, condensation, sublimation and physical vapor deposition. A vapour compression cycle is used in most household refrigerators, refrigerator-freezers and freezers. The performance of the refrigerators heavily depends on the phase change properties of the refrigerant used. Thus, it is of primary importance to any industrial designer to have a good understanding of the phase change behaviour of substances which will allow them for design modifications and optimisations. In our problem, a cylinder is initially filled with saturated liquid-vapour mixture of R-134a (a common refrigerant) at a specified pressure, 250 kPa and vapour quality of 0.25. A constant heat input, Q, is transferred to the cylinder until the refrigerant vaporizes completely at constant pressure. By clearly stating your assumptions throughout, 1. Analytically describe the Fluid Mechanics and Thermodynamics working principles of refrigerators operating using a vapour compression cycle; 2. Determine the initial volume; 3. Determine the work done; 4. Determine the total heat transfer; 5. Show the process on a P-v diagram; 6. Discuss the desired properties of substances that are used as refrigerants in the industry and potential problems arising. Share your view on the potential usage of CO2 as a refrigerant in commercial refrigerators.
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