A capillary tube for a 1/3 HP compressor designed for medium-temperature applications has a length of 3 meters and a diameter of 0.042 inches, using R134a refrigerant.
The capillary tube’s characteristics depend on the refrigerant gas and the operating temperatures of both the evaporator and condenser. The small diameter and extended length of the tube help regulate the refrigerant flow by increasing pressure loss as the fluid passes through.
Overview of Capillary Tubes for 1/3 HP Refrigerators
Key Features:
- Diameter: Small enough to restrict refrigerant flow.
- Length: Long enough to regulate pressure loss effectively.
Recommendation: The following video by MundoChiller provides insights into selecting the proper capillary tube size.
Applications by Temperature Range
| Application | Evaporation Temperature | Condensation Temperature |
|---|---|---|
| LBP (Low Pressure) | -23.3°C (-10°F) | 54.4°C (130°F) |
| MBP (Medium Pressure) | -6.7°C (20°F) | 54.4°C (130°F) |
| HBP (High Pressure) | 7.2°C (45°F) | 54.4°C (130°F) |
Source: Tecumseh
Guidelines for Selecting a Capillary Tube
- Length and Diameter: Both influence flow restriction.
- Diameter Changes: A percentage change in diameter impacts flow more than an equivalent change in length.
- Flow Speed: Longer tubes slow flow; excessively long tubes may become inefficient.
- Critical Length: Shortening a tube can initially increase flow, but excessively short tubes behave like orifices, not capillary tubes.
- Recommended Lengths: Between 5′ and 16′ for optimal operation.
Capillary Tubes for 1/3 HP Compressors Using R134a
| Power (HP) | Application | Diameter (in) | Length (m) |
|---|---|---|---|
| 1/3 | LBP | 0.036 | 2.5 |
| 1/3 | MBP | 0.042 | 3.0 |
| 1/3 | HBP | 0.050 | 2.0 |
Source: Tecumseh
Capillary Tubes for 1/3 HP Compressors Using R410A
| Power (HP) | Evaporator Temperature | Diameter/Length |
|---|---|---|
| 1/3 | Low (-10°F) | 0.031 in / 38″ |
| 1/3 | Medium (25°F) | 0.031 in / 30″ |
| 1/3 | High (45°F) | 0.042 in / 62″ |
Source: Industries JB
Capillary Tubes for R404A Refrigerant
| Cooling Capacity | Evaporator Temp | Diameter/Length |
|---|---|---|
| 1,000 Btu/h | -10°F (-17.22°C) | 0.031″ / 4½ ft |
| 1,250 Btu/h | -3.89°C (25°F) | 0.040″ / 13 ft |
Capillary Tubes for R407C Refrigerant
| Power (HP) | Low Temp (in/in) | Medium Temp (in/in) | High Temp (in/in) |
|---|---|---|---|
| 1/3 | 0.031 / 30″ | 0.042 / 96″ | 0.042 / 47″ |
Cooling Capacity of 1/3 HP Compressor
| Evaporation Temp (°C) | Cooling Capacity (BTU/h) |
|---|---|
| -35°C | 388.47 |
| -20°C | 1,108.75 |
| -10°C | 1,817.44 |
Conditions:
- Superheat: 5°C at evaporator outlet.
- Subcooling: 5°C at condenser outlet.
- Ambient Temperature: 35°C.
When conditions deviate, the cooling capacity varies.
