Refrigerants and altitude: Do water, alcohol, and ammonia provide the same refrigerating effect at different altitudes (i.e., varying ambient pressure)?

Introduction / Context:Refrigerating effect per unit mass depends on a refrigerant’s thermophysical properties (latent heat, specific heats) and operating pressures, which themselves are influenced by ambient conditions such as altitude.

Given Data / Assumptions:

• Comparison among water, alcohol, and ammonia as working fluids.
• Different altitudes imply different ambient pressures and heat sink temperatures.
• Conventional vapour compression or absorption cycles.

Concept / Approach:Refrigerating effect (per kg) is commonly approximated as the enthalpy difference between evaporator outlet and inlet. This depends on saturation temperatures/pressures and fluid properties, all of which vary distinctly for water, alcohols, and ammonia. Altitude alters condenser and sometimes evaporator pressures via ambient temperature/pressure changes, so the refrigerating effect is not identical across fluids or altitudes.

Step-by-Step Solution:Note that at a given evaporator temperature, each refrigerant has a unique latent heat and specific heat.Ambient (altitude) changes condenser pressure/temperature, shifting cycle state points.Therefore, the enthalpy change in the evaporator differs among refrigerants and with altitude.

Verification / Alternative check:Property charts (h–T or p–h) for ammonia vs. water vs. ethanol show markedly different latent heats and saturation curves, confirming unequal refrigerating effects.

Why Other Options Are Wrong:

• Yes/conditional options: ignore fluid-specific property differences and cycle dependence on ambient conditions.

Common Pitfalls:Assuming “same temperature lift” yields identical effects; property variability makes this false across different fluids.

Final Answer:No