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Selecting the Orifice for the T2/TE2 Thermostatic Expansion Valve – How It Works and Why It Matters
Thermostatic expansion valves are the heart of a refrigeration system – they control how much refrigerant flows into the evaporator. But they don’t work alone. A key component of every T2 or TE2 valve from Danfoss is the orifice insert, which regulates the liquid flow.
The operating principle is simple: based on the superheat measured at the evaporator outlet, the valve opens or closes, and the orifice meters the refrigerant. The insert size determines how much liquid passes through. In combination with the thermostatic element, this ensures stable superheat, optimal cooling capacity, and protection against compressor flooding.
Orifices are interchangeable, allowing the same valve body to be used in various applications – from display cases to cold rooms. You only need to change the insert size to match your system’s requirements.
Why are there different orifice sizes?
Every refrigeration system operates under different conditions. Evaporation temperature, refrigerant type, cooling load and pressure drop – all influence how much refrigerant the system needs. Choosing the wrong orifice (too small or too large) can lead to:
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reduced performance,
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unstable operation,
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or even compressor damage.
Refrigerants differ in physical properties like density and enthalpy. That’s why each refrigerant and cooling capacity corresponds to a specific orifice size. Danfoss provides detailed selection tables – and they’re not optional. They’re essential.
Orifice selection table – Danfoss T2/TE2
Conditions: To = –10 °C, Tc = +38 °C, SH = 4 K, Δp = 1 bar
| Orifice No. | R22 | R407C | R134a | R513A | R404A /R507 |
R407A | R407F | R448A | R449A | R454C | R455A | R1234yf |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0X | 0.9 | 0.92 | 0.68 | 0.58 | 0.64 | 0.88 | 1.00 | 0.90 | 0.88 | 0.77 | 0.86 | 0.49 |
| 0 | 1.8 | 1.8 | 1.2 | 1.2 | 1.2 | 1.7 | 2.0 | 1.8 | 1.7 | 1.5 | 1.7 | 0.87 |
| 1 | 3.5 | 3.5 | 2.1 | 2.1 | 2.6 | 3.4 | 3.9 | 3.5 | 3.4 | 2.8 | 3.3 | 1.5 |
| 2 | 4.7 | 4.8 | 2.6 | 2.2 | 3.7 | 4.7 | 5.4 | 4.8 | 4.6 | 3.6 | 4.4 | 1.8 |
| 3 | 8.2 | 8.1 | 4.3 | 3.7 | 6.4 | 8.1 | 9.4 | 8.1 | 7.9 | 6.2 | 7.6 | 3.1 |
| 4 | 12.1 | 12.1 | 6.4 | 5.3 | 9.9 | 12.4 | 14.3 | 12.6 | 12.1 | 9.3 | 11.5 | 4.6 |
| 5 | 16.7 | 16.5 | 8.4 | 6.8 | 13.0 | 16.3 | 19.0 | 16.3 | 15.7 | 11.8 | 14.7 | 5.9 |
| 6 | 19.7 | 19.7 | 10.2 | 8.6 | 15.5 | 19.6 | 22.9 | 19.8 | 19.1 | 14.8 | 18.3 | 7.3 |
Rated capacity is based on:
Evaporating temperature te = −4.4 °C
Condensing temperature tc = 38 °C
Refrigerant temperature ahead of valve tl = 37 °C
Example:
Refrigerant: R-448A, Cooling capacity: 7.6 kW, To = –10 °C → Use orifice no. 5
Want to make sure the valve will work properly? Always select a nozzle based on real operating parameters, not “by eye”. A diameter that is too large or too small can result in unstable overheating, loss of efficiency and even compressor failure.