Case 04 / BU ME304 laboratory report draft

Thermal model versus experiment

Compare measured heating and boiling traces with a simplified pot-and-water energy balance, then examine why inferred latent heat differs from the reference.

Team contribution

Team laboratory participation. Individual measurement and analysis roles, the final roster and experiment date remain unresolved; the report is a draft.

Key result

Inferred latent heats are about 49% and 39% below the report reference near 100 °C / 1 atm. Illustrative propagated uncertainty excludes systematic bias and does not resolve the mismatch.

Results and technical detail ↓

Two measured water-temperature traces from start to end; Trial 2 drops after 20 minutes. — FIG. 01Complete measured logger traces in minutes and °C, including Trial 2’s drop after the 20 min analysis endpoint. Probe handling is unknown.ME304 team laboratory study; Stage 2A replot and calculation from original measurements.

Constraints

Use logger time in minutes and logger starting temperatures.
Separate measurements, inferred quantities and reference properties.

Analysis and Evidence

The analysis infers average preboiling water-heating power from mass, temperature rise and time: P = m·c·ΔT/Δt, with c = 4,180 J/(kg·K). It reuses that power during boiling and assigns total mass loss to the boiling interval.

That indirect estimate omits changing heat transfer and pot/plate storage. Reusing it in the pot-plus-water Euler model does not provide independently calibrated heater input. The large reference mismatch exposes the limitation rather than validating the model.

The analysis interval ends at 20 min. The complete trace retains Trial 2’s later temperature drop; probe handling is unknown, so the drop is not established as bulk-water cooling.

Measured heating and boiling traces compared with dashed approximate preboiling model curves. — FIG. 02Measured temperatures versus the simplified pot-plus-water model over 0–20 min. Model input power is inferred from water heating, not independently measured.ME304 team laboratory study; Stage 2A replot and calculation from original measurements.

Two inferred latent heat estimates with assumption-based error bars below the nominal water reference. — FIG. 03Inferred latent heats versus the report reference near 100 °C / 1 atm. Error bars propagate assumed inputs and exclude systematic bias.ME304 team laboratory study; Stage 2A replot and calculation from original measurements.

Evidence & interpretation

Results & validation

Inferred latent heats are about 49% and 39% below the report reference near 100 °C / 1 atm. Illustrative propagated uncertainty excludes systematic bias and does not resolve the mismatch.

Simplified Euler model includes pot heat storage and approximate convection losses.

reproduced approximate model · team

Uses water-only inferred power as pot-plus-water input; not independently calibrated. Radiation, thermal gradients, preboiling evaporation and actual exposed area unresolved.

Trial 1 · initial water mass

0.543 kg

derived from measured masses

Initial total mass minus empty pot mass.

Trial 1 · logger start

24.8 °C

measured logger value

Logger start, not manual spreadsheet initial value.

Trial 1 · inferred heating power

284.5 ± 8.9 W

inferred model quantity

Water-only average preboiling heating rate; not hot-plate electrical input.

Uncertainty assumptions

Illustrative first-order propagation of assumed independent 1σ inputs; systematic bias excluded; not instrument-certified accuracy or a 95% confidence interval.

each scale kg: 0.001
each temperature C: 1
onset min: 0.25
endpoint min: 0.25

Trial 1 · inferred latent heat

1,146 ± 68 kJ/kg

inferred model quantity

Preboiling inferred power reused during boiling; total mass loss assigned to that interval. Fails agreement with nominal reference.

Uncertainty assumptions

Illustrative first-order propagation of assumed independent 1σ inputs; systematic bias excluded; not instrument-certified accuracy or a 95% confidence interval.

each scale kg: 0.001
each temperature C: 1
onset min: 0.25
endpoint min: 0.25

Trial 2 · initial water mass

0.741 kg

derived from measured masses

Initial total mass minus empty pot mass.

Trial 2 · logger start

32.9 °C

measured logger value

Logger start, not manual spreadsheet initial value.

Trial 2 · inferred heating power

330 ± 11 W

inferred model quantity

Water-only average preboiling heating rate; not hot-plate electrical input.

Uncertainty assumptions

Illustrative first-order propagation of assumed independent 1σ inputs; systematic bias excluded; not instrument-certified accuracy or a 95% confidence interval.

each scale kg: 0.001
each temperature C: 1
onset min: 0.25
endpoint min: 0.25

Trial 2 · inferred latent heat

1,373 ± 84 kJ/kg

inferred model quantity

Preboiling inferred power reused during boiling; total mass loss assigned to that interval. Fails agreement with nominal reference.

Uncertainty assumptions

Illustrative first-order propagation of assumed independent 1σ inputs; systematic bias excluded; not instrument-certified accuracy or a 95% confidence interval.

each scale kg: 0.001
each temperature C: 1
onset min: 0.25
endpoint min: 0.25

Nominal water reference

2,257 kJ/kg

report reference value

Approximate report reference near 100 °C and 1 atm; not a measured value from this experiment.

Engineering limitations

Water-only inferred power is reused for boiling and for a pot-plus-water model. Uncertainty uses assumed tolerances and excludes systematic bias. Actual electrical input, calibration, roster and experiment date are unconfirmed.

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