Air Conditioner: Refrigerator or Heat Pump?

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SUMMARY

The discussion focuses on calculating the heat absorbed by refrigerant in an air conditioning system, specifically using a refrigerant mass of 7.00 kg with 54.0% in liquid phase. The initial calculation of heat absorbed (Qc) was incorrectly based on the total vapor mass. The correct approach requires calculating the heat needed to vaporize the additional mass of refrigerant transitioning from liquid to vapor, which is 49% of the total mass (7.00 kg). The heat of vaporization is given as 1.50×105 J/kg.

PREREQUISITES
  • Understanding of thermodynamics principles related to phase changes
  • Knowledge of refrigerant properties and heat transfer calculations
  • Familiarity with the concept of mass flow rates in HVAC systems
  • Basic proficiency in algebra for solving equations
NEXT STEPS
  • Calculate the heat absorbed during the vaporization of refrigerant using Qc = Mv * Lv
  • Study the principles of heat transfer in HVAC systems
  • Explore the properties of different refrigerants and their heat of vaporization
  • Learn about the efficiency of heat pumps compared to traditional air conditioning systems
USEFUL FOR

Students in thermodynamics, HVAC technicians, engineers involved in refrigeration design, and anyone interested in understanding heat transfer in air conditioning systems.

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Homework Statement


Air conditioners operate on the same principle as refrigerators. Consider an air conditioner that has 7.00 kg of refrigerant flowing through its circuit each cycle. The refrigerant enters the evaporator coils in phase equilibrium, with 54.0 % of its mass as liquid and the rest as vapor. It flows through the evaporator at a constant pressure and when it reaches the compressor 95% of its mass is vapor. In each cycle, how much heat (Qc) is absorbed by the refrigerant while it is in the evaporator? The heat of vaporization of the refrigerant is 1.50×105 J/kg .


Homework Equations



Qc = Mv*Lv
Mv = Mass of vapor
Lv=heat of vaporization

The Attempt at a Solution



I calculated what is the mass of the vapor
M of liquid = 7 kg *54% = 3.78kg
M of vapor = 7 kg - 3.78kg = 3.22kg
then Qc = Mv*Lv
3.22 * 1.50*10(5) = 483000 J

Please.. help me..
thank you
 
Physics news on Phys.org
You have calculated the energy that would be released if all of the vapor condensed. What is wanted is the energy to vaporise an additional (54%-5%) of the total mass.
 

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