Heat pumps: Questions about compressor pump refrigerant gas and evaporator

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SUMMARY

The discussion centers on the operation of heat pumps, specifically focusing on the mechanics of compressor function and refrigerant behavior. The user explores how a piston compressor compresses refrigerant gas within a sealed system, questioning the dynamics of pressure and temperature during the evaporation and condensation stages. Key insights include the understanding that the compressor does indeed pump refrigerant gas from the evaporator into the high-pressure space, and that the process involves a series of controlled valve operations to manage gas flow. The user also seeks clarification on the implications of constant pressure during evaporation and condensation phases.

PREREQUISITES
  • Understanding of thermodynamics principles, including latent heat and specific heat capacity.
  • Familiarity with vapor-compression refrigeration cycles.
  • Knowledge of pressure-volume and temperature-entropy diagrams.
  • Basic mechanics of reciprocating compressors.
NEXT STEPS
  • Research the operation of reciprocating compressors in detail.
  • Study the principles of vapor-compression refrigeration cycles.
  • Examine the effects of refrigerant properties on heat pump efficiency.
  • Learn about the thermodynamic cycles involved in heat pump operation.
USEFUL FOR

Engineers, HVAC professionals, and anyone interested in the mechanics and thermodynamics of heat pumps, particularly those using propane as a refrigerant.

  • #31
GreenWombat said:
Hi Russ. In your contribution (Saturday, 24 August), you wrote that the pressure drop across the evaporator was “too small to be visible on the P-V diagram and can be ignored.” For me, that was brilliant because it resolved the contradiction of (1) the pressure-volume diagram showing constant volume and (2) refrigerant moving across the evaporator without any pressure drop.
My error: I meant "the pressure-volume diagram showing constant pressure"
 

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