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An application requires R-12 at −140°C. The triple-point temperature is −157°C. Find the pressure of the saturated vapour at the required condition.
- a)0.0058 kPa
- b)0.0098 kPa
- c)0.0068 kPa
- d)0.0088 kPa
Correct answer is option 'B'. Can you explain this answer?
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Verified Answer
An application requires R-12 at −140°C. The triple-point tem...
The lowest temperature for R-12 is -90°C, so it must be extended to -140°C using the Clapeyron equation.
at T1= -90°C = 183.2 K, P1 = 2.8 kPa
R = 8.3145/120.914 = 0.068 76 kJ/kg K
ln P/P1 = (hfg/R)(T-T1)/(T*T1)
= (189.748/0.068 76)[(133.2 – 183.2)/(133.2 × 183.2)] = -5.6543
P = 2.8 exp(-5.6543) = 0.0098 kPa.
at T1= -90°C = 183.2 K, P1 = 2.8 kPa
R = 8.3145/120.914 = 0.068 76 kJ/kg K
ln P/P1 = (hfg/R)(T-T1)/(T*T1)
= (189.748/0.068 76)[(133.2 – 183.2)/(133.2 × 183.2)] = -5.6543
P = 2.8 exp(-5.6543) = 0.0098 kPa.
Most Upvoted Answer
An application requires R-12 at −140°C. The triple-point tem...
The beginning of the process to ensure proper functioning. The R-12 refrigerant is used in various applications, such as air conditioning systems, refrigerators, and automotive air conditioning.
R-12, also known as dichlorodifluoromethane, is a type of chlorofluorocarbon (CFC) refrigerant. It has been widely used in the past for its excellent cooling properties and stability. However, due to its harmful effects on the environment, its production and use have been phased out in many countries.
If an application requires R-12, it is important to consider the following:
1. Availability: R-12 is no longer produced or readily available in most countries due to its harmful impact on the ozone layer. It has been replaced by more environmentally friendly refrigerants, such as R-134a or R-410A. Finding R-12 can be difficult and expensive.
2. Alternatives: If R-12 is not available or too expensive, it is recommended to explore alternative refrigerants that are compatible with the application. These alternatives should be approved by the manufacturer or a professional in the field to ensure proper functioning and safety.
3. Retrofitting: In some cases, it may be possible to retrofit the application to use a different refrigerant. This process involves modifying the system to accommodate a different refrigerant that is more readily available and environmentally friendly. Retrofitting can be complex and should be done by a qualified professional.
4. Legal requirements: It is essential to comply with local regulations and laws regarding the use of refrigerants. In many countries, the use of R-12 is prohibited or heavily regulated due to its harmful effects. Violating these regulations can result in fines or legal consequences.
In conclusion, if an application requires R-12, it may be challenging to find and use this refrigerant due to its environmental impact and restricted availability. Exploring alternative refrigerants or retrofitting the system may be necessary to ensure compliance with regulations and proper functionality.
R-12, also known as dichlorodifluoromethane, is a type of chlorofluorocarbon (CFC) refrigerant. It has been widely used in the past for its excellent cooling properties and stability. However, due to its harmful effects on the environment, its production and use have been phased out in many countries.
If an application requires R-12, it is important to consider the following:
1. Availability: R-12 is no longer produced or readily available in most countries due to its harmful impact on the ozone layer. It has been replaced by more environmentally friendly refrigerants, such as R-134a or R-410A. Finding R-12 can be difficult and expensive.
2. Alternatives: If R-12 is not available or too expensive, it is recommended to explore alternative refrigerants that are compatible with the application. These alternatives should be approved by the manufacturer or a professional in the field to ensure proper functioning and safety.
3. Retrofitting: In some cases, it may be possible to retrofit the application to use a different refrigerant. This process involves modifying the system to accommodate a different refrigerant that is more readily available and environmentally friendly. Retrofitting can be complex and should be done by a qualified professional.
4. Legal requirements: It is essential to comply with local regulations and laws regarding the use of refrigerants. In many countries, the use of R-12 is prohibited or heavily regulated due to its harmful effects. Violating these regulations can result in fines or legal consequences.
In conclusion, if an application requires R-12, it may be challenging to find and use this refrigerant due to its environmental impact and restricted availability. Exploring alternative refrigerants or retrofitting the system may be necessary to ensure compliance with regulations and proper functionality.
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An application requires R-12 at −140°C. The triple-point tem...
The lowest temperature for R-12 is -90°C, so it must be extended to -140°C using the Clapeyron equation.
at T1= -90°C = 183.2 K, P1 = 2.8 kPa
R = 8.3145/120.914 = 0.068 76 kJ/kg K
ln P/P1 = (hfg/R)(T-T1)/(T*T1)
= (189.748/0.068 76)[(133.2 – 183.2)/(133.2 × 183.2)] = -5.6543
P = 2.8 exp(-5.6543) = 0.0098 kPa.
at T1= -90°C = 183.2 K, P1 = 2.8 kPa
R = 8.3145/120.914 = 0.068 76 kJ/kg K
ln P/P1 = (hfg/R)(T-T1)/(T*T1)
= (189.748/0.068 76)[(133.2 – 183.2)/(133.2 × 183.2)] = -5.6543
P = 2.8 exp(-5.6543) = 0.0098 kPa.
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An application requires R-12 at −140°C. The triple-point temperature is −157°C. Find the pressure of the saturated vapour at the required condition.a)0.0058 kPab)0.0098 kPac)0.0068 kPad)0.0088 kPaCorrect answer is option 'B'. Can you explain this answer?
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