Industrial/commercial reciprocating refrigeration: Which refrigerant is most widely used in larger plants due to excellent thermodynamic efficiency and zero GWP?

Introduction / Context:
Refrigerant choice in large reciprocating and screw plants balances efficiency, environmental impact, safety, and cost. Ammonia has remained the workhorse of industrial refrigeration for food processing, cold storage, and ice plants.

Given Data / Assumptions:

• “Larger” implies hundreds of kW to multi-MW capacities.
• Preference for mature technology and readily available components.
• Compliance with environmental regulations (ODP = 0, very low GWP).

Concept / Approach:
Ammonia (R-717) offers high latent heat, excellent heat-transfer coefficients, and high COP, reducing power per tonne of refrigeration. It has zero ozone depletion potential and essentially zero GWP. Though toxic and reactive with copper, proper design (steel piping, safety systems) mitigates risks. Other options have limitations in efficiency, pressure levels, or environmental impact.

Step-by-Step Reasoning:

Verification / Alternative check:
Industry standards and many installed plants confirm widespread use of ammonia in large systems.

Why Other Options Are Wrong:

• CO₂ (R-744) demands transcritical or very high pressures; used, but not the most common for reciprocating in large low-stage plants.
• SO₂ (R-764) is obsolete due to toxicity and corrosion.
• R-12 is banned; R-134a is common in medium systems but less dominant in large industrial reciprocating plants versus ammonia.

Common Pitfalls:
Overlooking material compatibility (ammonia attacks copper alloys) and necessary safety ventilation/detection systems.

Final Answer:
Ammonia (R-717)