Calculate condenser efficiency, inlet water temperature, outlet water temperature, or vacuum temperature from any 3 known inputs at once.
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Condenser Efficiency Formula
The condenser efficiency calculation compares the actual cooling water temperature rise to the maximum possible rise based on the vacuum temperature at the condenser absolute pressure.
- CE = condenser efficiency, as a percentage
- T_in = inlet water temperature, in °C
- T_out = outlet water temperature, in °C
- T_v = vacuum temperature at absolute pressure, in °C
If condenser efficiency is missing, the calculator uses the first formula. If outlet water temperature is missing, it rearranges the same relationship to solve for T_out. If vacuum temperature is missing, it solves for T_v. If inlet water temperature is missing, it solves the efficiency equation for T_in.
Condenser Efficiency Result Ranges
Use these ranges as a general check. Acceptable condenser efficiency depends on condenser design, cooling water conditions, fouling, air leakage, and operating load.
| Condenser Efficiency | General Meaning | What to Check |
|---|---|---|
| Below 50% | Low heat transfer performance | Tube fouling, low cooling water flow, air leakage, high heat load |
| 50% to 70% | Moderate performance | Compare with design data and recent operating history |
| 70% to 85% | Commonly acceptable for many operating condensers | Monitor trend over time |
| Above 85% | High efficiency or possible input issue | Verify temperatures, pressure conversion, and sensor accuracy |
Temperature Inputs and Checks
| Input | Expected Relationship | Why It Matters |
|---|---|---|
| Inlet water temperature | Usually the lowest of the three temperatures | It is the starting temperature of the cooling water. |
| Outlet water temperature | Should normally be higher than inlet water temperature | The water gains heat as steam condenses. |
| Vacuum temperature | Should be higher than inlet water temperature for a valid denominator | If it equals inlet temperature, condenser efficiency cannot be calculated. |
| Efficiency | Usually between 0% and 100% | Values outside this range usually mean one or more inputs should be checked. |
Example Problems
Example 1: Calculate condenser efficiency
You have an inlet water temperature of 25°C, an outlet water temperature of 35°C, and a vacuum temperature of 45°C.
The condenser efficiency is 50%.
Example 2: Calculate vacuum temperature
You have an inlet water temperature of 28°C, an outlet water temperature of 38°C, and a condenser efficiency of 62.5%.
The vacuum temperature at absolute pressure is 44°C.
FAQ
What does condenser efficiency mean?
Condenser efficiency shows how much of the available temperature difference is actually used to heat the cooling water. A higher percentage means the outlet water temperature is closer to the vacuum temperature, which usually indicates better heat transfer.
Why is vacuum temperature used instead of vacuum pressure directly?
The formula uses the saturation temperature corresponding to the condenser absolute pressure. Vacuum pressure itself is not a temperature, so it must be converted to the equivalent saturation temperature before using this calculation.
Can condenser efficiency be greater than 100%?
In normal use, condenser efficiency should not be greater than 100%. A result above 100% usually means the outlet water temperature is higher than the vacuum temperature, the pressure-to-temperature conversion is wrong, or one of the temperature readings is inaccurate.
