Understanding the conversion between kilowatts and tons of refrigeration is essential for HVAC professionals and engineers. This calculation bridges electrical power and cooling capacity, enabling precise system design.
This article explores the ASHRAE standard for kW to tons of refrigeration conversion, providing formulas, tables, and practical examples. Learn how to accurately convert and apply these values in real-world scenarios.
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Comprehensive Tables for kW to Tons of Refrigeration Conversion (ASHRAE)
Below are detailed tables showing common conversions between kilowatts (kW) and tons of refrigeration (TR) based on ASHRAE standards. These values are widely used in HVAC design and equipment specification.
| Tons of Refrigeration (TR) | Cooling Capacity (kW) | Cooling Capacity (BTU/hr) | Approximate Electrical Power (kW) |
|---|---|---|---|
| 1 | 3.517 | 12,000 | 0.9 – 1.2 |
| 2 | 7.034 | 24,000 | 1.8 – 2.4 |
| 5 | 17.585 | 60,000 | 4.5 – 6.0 |
| 10 | 35.17 | 120,000 | 9.0 – 12.0 |
| 20 | 70.34 | 240,000 | 18.0 – 24.0 |
| 50 | 175.85 | 600,000 | 45.0 – 60.0 |
| 100 | 351.7 | 1,200,000 | 90.0 – 120.0 |
The table above shows the direct relationship between tons of refrigeration and kilowatts, with BTU/hr included for reference. The electrical power range depends on system efficiency and coefficient of performance (COP).
Fundamental Formulas for kW ↔ Tons of Refrigeration Conversion (ASHRAE)
Accurate conversion between kilowatts and tons of refrigeration requires understanding the underlying thermodynamic principles and standard definitions.
- Definition of 1 Ton of Refrigeration (TR): The amount of heat absorbed to melt 1 ton (2000 lbs) of ice at 0°C in 24 hours.
- Heat of Fusion of Ice: Approximately 334,000 J/kg or 144 BTU/lb.
- Standard Conversion: 1 TR = 12,000 BTU/hr = 3.517 kW (thermal).
Conversion from Tons of Refrigeration to Kilowatts
The basic formula to convert tons of refrigeration to kilowatts is:
- kW: Cooling capacity in kilowatts (thermal power)
- TR: Tons of refrigeration
Conversion from Kilowatts to Tons of Refrigeration
To convert kilowatts back to tons of refrigeration:
- TR: Tons of refrigeration
- kW: Cooling capacity in kilowatts (thermal power)
Electrical Power Considerations and Coefficient of Performance (COP)
While kW and TR conversions relate to thermal power, electrical power input depends on system efficiency, expressed as COP:
- COP: Coefficient of Performance, ratio of cooling output to electrical input
- Typical COP values for refrigeration systems range from 3 to 6 depending on technology and conditions
For example, a 10 TR system (35.17 kW thermal) with a COP of 4 would require:
Detailed Real-World Examples of kW ↔ Tons of Refrigeration Conversion
Example 1: Converting 15 kW Cooling Capacity to Tons of Refrigeration
A commercial refrigeration system has a cooling capacity of 15 kW. Determine the equivalent tons of refrigeration.
- Given: kW = 15
- Formula: TR = kW ÷ 3.517
Step 1: Apply the formula
Step 2: Interpretation
The system provides approximately 4.27 tons of refrigeration, suitable for medium-sized commercial applications.
Example 2: Calculating Electrical Power Required for a 20 TR System with COP of 3.5
An HVAC engineer needs to estimate the electrical power consumption of a 20 TR air conditioning system with a COP of 3.5.
- Given: TR = 20, COP = 3.5
- Step 1: Convert TR to thermal kW
- Step 2: Calculate electrical power input
Step 3: Interpretation
The system requires approximately 20.10 kW of electrical power to deliver 20 tons of refrigeration at the specified COP.
Additional Technical Insights on kW and Tons of Refrigeration
Understanding the nuances of kW and tons of refrigeration conversions is critical for optimizing HVAC system design, energy efficiency, and cost-effectiveness.
- Impact of Ambient Conditions: The actual cooling capacity and power consumption vary with ambient temperature, humidity, and system load.
- System Types: Vapor compression, absorption, and thermoelectric refrigeration systems have different COPs affecting electrical power calculations.
- Energy Efficiency Ratios (EER): Related to COP, EER is often used in the US to rate cooling efficiency (EER = COP × 3.412).
- ASHRAE Standards: ASHRAE Handbook and Standard 90.1 provide guidelines for HVAC system performance and energy calculations.
For further reading, consult the ASHRAE Standards and Guidelines for the most authoritative and updated information.