Calculator Inputs
Formula Used
The calculator uses the practical ratio
F = h_measured / h_reference.
The measured coefficient is h_measured = q'' / ΔT.
The automatic reference estimate is based on a smooth laminar condensation form:
h_laminar = 0.943[(ρl(ρl-ρv)g hfg kl³)/(μl L ΔT)]^0.25.
The corrected reference is
h_reference = h_laminar × shear multiplier × geometry multiplier.
You may also enter a manual reference coefficient from lab data, software, or a published case.
Example Data Table
| Case | q'' kW/m² | ΔT K | Measured h | Reference h | F factor | Reading |
|---|---|---|---|---|---|---|
| Low transfer | 14.0 | 18 | 777.78 | 1050.00 | 0.7407 | Below reference |
| Balanced case | 20.0 | 18 | 1111.11 | 1080.00 | 1.0288 | Near reference |
| Enhanced case | 28.5 | 18 | 1583.33 | 1110.00 | 1.4264 | Enhanced transfer |
How to Use This Calculator
- Enter the measured heat flux from the condensation test.
- Add the heat transfer area and temperature values.
- Enter fluid properties at the film or average temperature.
- Use correction multipliers when shear or geometry effects are known.
- Leave manual reference h as zero for automatic calculation.
- Press calculate, then review the result above the form.
- Use CSV or PDF buttons to save the report.
Engineering Notes on Yuann F Factor Evaluation
Purpose of the Factor
The F factor helps compare a measured condensation result with a reference model. It is useful when vapor and noncondensable gas move inside a tube. A value near one means the test follows the selected reference. A value above one shows stronger measured transfer. A value below one shows weaker measured transfer.
Why Inputs Matter
The result depends on heat flux, wall temperature, saturation temperature, and fluid properties. Small errors in temperature difference can strongly affect the coefficient. Viscosity and thermal conductivity also change with temperature. Use properties from a trusted table. Keep units consistent before comparing cases.
Reference Coefficient
This page calculates a smooth laminar reference coefficient. It also lets you override that value. This is helpful when a lab report gives its own baseline. The correction multipliers allow practical adjustment. They should not be used as hidden fitting values. Record the reason for every multiplier.
Interpreting Results
The calculator labels three common ranges. Values below 0.75 are below reference. Values from 0.75 to 1.25 are near reference. Values above 1.25 show enhancement. These ranges are practical guides. They are not universal acceptance limits.
Using the Report
The CSV file is best for spreadsheets. The PDF file is best for records. Save the notes with each run. Add test pressure, sensor details, and data source. This keeps later reviews clear. It also helps compare several tube runs.
Frequently Asked Questions
1. What does the F factor show?
It shows how measured heat transfer compares with a selected reference value. A value of one means both values match.
2. What is the main formula?
The main formula is F equals measured heat-transfer coefficient divided by the corrected reference heat-transfer coefficient.
3. Can I use a manual reference coefficient?
Yes. Enter a positive manual reference h value. The calculator will use it instead of the automatic laminar estimate.
4. What units should I use?
Use the units shown beside each field. Heat flux uses kW per square meter. Length values use meters.
5. Why is temperature difference important?
The measured coefficient equals heat flux divided by temperature difference. A small temperature error can change the result strongly.
6. What does a value above one mean?
It means measured transfer is higher than the corrected reference. This may reflect shear, waves, turbulence, or model mismatch.
7. What does the uncertainty band do?
It gives a simple upper and lower range around the F factor. Use it for quick sensitivity review.
8. Is this a final design tool?
No. It is a calculation aid. Validate important engineering work with test standards, property tables, and expert review.