Section 1 of 6
Chiller Configuration
Select chiller type, compressor drive, and nominal capacity. These selections drive refrigerant cycle inputs and applicable efficiency benchmarks.
Chiller Type & Capacity
Section 2 of 6
Condenser Water
Enter condenser water temperatures and flow rate. These values drive heat rejection duty, condenser approach temperature, and water-side fouling analysis.
Condenser Water Temperatures
Section 3 of 6
Evaporator (Chilled Water)
Enter chilled water supply and return temperatures and flow rate. These values determine cooling capacity, evaporator duty, and chilled water approach temperature.
Chilled Water Temperatures
Section 4 of 6
Refrigerant Cycle
Enter refrigerant saturation temperatures or pressures. These drive compressor lift, condensing and evaporating approach temperatures, and COP calculations. All inputs are optional — calculations will use water-side temperatures when refrigerant data is absent.
Saturation Temperatures
Compressor Power & Approach Temperatures
Section 5 of 6
Known Performance optional
Enter datasheet or design-rated values to calculate cleanliness factors and fouling resistance for both condenser and evaporator. Compare actual performance to design and detect fouling degradation.
Design / Datasheet Values
Section 6 of 6
Calculate & Results
Click Calculate to run all available computations. Blank optional inputs are skipped — the calculator computes what it can from the data provided.
Performance Summary
Section 7 of 7
Formulas & References
Engineering basis for all calculations performed by this tool.
Evaporator Heat Duty (Cooling Capacity)
Where ΔT_chw = CHWRT − CHWST. Constant 500 = 8.34 lb/gal × 60 min/h × specific heat ≈ 1.0 BTU/lb·°F for water.
Refrigeration Ton Conversion
One refrigeration ton = 12,000 BTU/h = 3.517 kW. Heat rejection duty: Q_cond = Q_evap + W_comp.
Coefficient of Performance (COP)
For vapor-compression chillers. A higher COP indicates better efficiency. Single-stage absorption chillers have COP ≈ 0.6–0.8; double-stage ≈ 1.1–1.4.
Energy Efficiency Ratio (kW/ton)
Lower kW/ton = better efficiency. ASHRAE 90.1 full-load benchmarks: centrifugal ≤ 0.634 kW/ton (water-cooled); screw ≤ 0.780 kW/ton. IPLV targets are typically 10–20% lower.
Carnot COP & Isentropic Efficiency
Temperatures in Kelvin (K = °F + 459.67) / 1.8. Typical isentropic efficiency for well-maintained centrifugal: 55–70%.
Condenser Heat Duty
Heat balance: all compressor work is rejected as heat plus the absorbed evaporator load. For absorption chillers, W_comp is replaced by heat input Q_generator.
LMTD — Condenser & Evaporator
For condenser (counterflow): ΔT₁ = T_ref_cond − ECWT; ΔT₂ = T_ref_cond − LCWT.
For evaporator (counterflow): ΔT₁ = CHWRT − T_ref_evap; ΔT₂ = CHWST − T_ref_evap.
Approach Temperature
Design condenser approach: 8–12°F (4.4–6.7°C). Design evaporator approach: 5–8°F (2.8–4.4°C). Values exceeding design by >3°F indicate fouling or scaling on water-side surfaces.
Overall Heat Transfer Coefficient (U)
A = N_tubes × π × OD × L × passes. U is then compared to datasheet U to compute cleanliness factor and fouling resistance.
Cleanliness Factor & Fouling Resistance
CF below 85% typically indicates significant fouling. TEMA allowable Rf for treated cooling water: 0.001 h·ft²·°F/BTU. Values > 0.002 indicate actionable fouling on either condenser or evaporator surfaces.
Compressor Lift
Lift is the primary driver of compressor energy consumption. Every 1°F increase in condensing temperature increases energy consumption by approximately 1.5–2%. Every 1°F decrease in evaporating temperature increases consumption by approximately 1.5%. Fouling-driven approach temperature increases directly elevate effective lift.
| Chiller Type | Full-Load kW/ton | COP Range | ASHRAE 90.1 Limit |
|---|---|---|---|
| Centrifugal (water-cooled) | 0.45–0.70 | 5.0–7.8 | ≤ 0.634 kW/ton |
| Screw / Scroll (water-cooled) | 0.65–0.85 | 4.1–5.4 | ≤ 0.780 kW/ton |
| Absorption (single-stage) | N/A (heat-driven) | 0.60–0.80 | COP ≥ 0.70 |
| Absorption (double-stage) | N/A (heat-driven) | 1.10–1.40 | COP ≥ 1.00 |
Efficiency Penalty from Condenser Fouling
Each 0.001 h·ft²·°F/BTU of condenser fouling resistance raises the condensing saturation temperature approximately 1–2°F, increasing compressor power by 1.5–2.0%. ASHRAE research (RP-884) confirms that condenser fouling is the most common cause of chiller efficiency degradation in operating plants.
References: ASHRAE Handbook — Refrigeration (2022); ASHRAE Standard 90.1-2022; AHRI Standard 550/590; ARI Standard 560 (absorption); TEMA Standards 10th Ed.; Engineering Toolbox.