1. Pure Thermodynamic NRE (Benchmark)

≈99.7 BTU/lb

This is the locked chart value calculated strictly as:

NRE = H₂ − H₁
at exactly 40°F evaporator (dew) / 110°F condenser (bubble)

No superheat, no subcooling, no field variables. Pure enthalpy difference from the refrigerant tables (Hg at evaporator minus Hf at condenser).

2. Field NRE (Recommended – Real World)

~96–102 BTU/lb (typical measured range with real SH/SC)

This includes your actual measured superheat and subcooling:

Thermodynamic NRE = (Hg_sat + SH × 0.24) − (Hf_liquid − SC × 0.22)
Field NRE = Thermodynamic NRE × 0.965

Use this number for diagnostics, charge calculations, and capacity estimates.

How to Read the Chart

• H1 = Enthalpy of liquid refrigerant after the metering device (post-flash)
• H2 = Enthalpy of vapor leaving the evaporator (at measured superheat)
• NRE = H2 − H1 → This is the actual refrigerating effect per pound of refrigerant circulating.

Our Numbers for R-32

Type	Value	When to Use
Pure Thermodynamic NRE	≈99.7 BTU/lb	Benchmark / manufacturer comparison (no SH/SC at 40/110°F std conditions)
Field NRE (Recommended)	~96–102 BTU/lb (varies with actual SH/SC)	Real-world diagnostics with measured SH & SC (derated ×0.965)
Sizing Reference NRE	~88–94 BTU/lb	Conservative value (Field × 0.92) to avoid oversizing equipment

Why the Numbers Are Different

The pure value (≈99.7 BTU/lb at standard 40°F evap / 110°F cond) assumes ideal saturated conditions with zero superheat and zero subcooling. In the real world we always have some superheat (adds energy to the suction vapor using Cp≈0.24, increasing H2) and subcooling (removes energy from the liquid using Cp≈0.22, decreasing H1). The thermodynamic NRE at actual conditions is then derated by 0.965 to produce the realistic “Field NRE” used for diagnostics. Sizing uses an extra conservative 0.92 factor on the Field value.

How to Use This Page / Find Your Own H1 & H2

1. Measure liquid line temperature and pressure right after the metering device → look up Hf (this is your H1 base).
2. Measure suction line temperature and pressure at the evaporator outlet → look up Hg and add superheat effect using the R-32 Cp ≈0.24 (this is your H2).
3. Thermodynamic NRE = H2 − H1
4. Field NRE = Thermodynamic NRE × 0.965
5. Compare your Field NRE to the pure benchmark (≈99.7 at std conditions) and the ranges shown in the table above. The main diagnostic tool (r32.htm) computes this automatically.

Tip: On the main R-32 diagnostic tool (r32.htm), the “Field NRE” value already includes your measured superheat and subcooling using the same method.

Note: The pure thermodynamic value (≈99.7 BTU/lb at standard 40°F/110°F conditions) comes directly from the saturation table in data/r32.json used by the diagnostic tool. Your actual thermodynamic NRE (and the final Field NRE after ×0.965 derating) will vary depending on measured superheat and subcooling. The main R-32 diagnostic tool computes all of this live.