A factory test can demonstrate the cooler’s heat-transfer performance at specified temperatures and flows. At site, piping, pumps, valves and water conditions determine whether those inputs reach the cooler. The two acceptance stages should share a clear boundary rather than repeat the same rating statement. [1]
| Evidence | Factory boundary | Installed boundary |
|---|---|---|
| Thermal duty | Exchanger under defined fluid conditions | Transformer losses and actual cooling-loop temperatures |
| Flow and pressure | Measured exchanger resistance | Pump/header/valve operating point |
| Water condition | Test fluid specification | Site chemistry, solids and seasonal range |
| Leak monitoring | Supplied collection/detector function | Installed drain path, alarms and plant interface |
| Uncertainty | Test instruments and heat balance | Site sensors, placement, stability and flow measurement |
Check whether site conditions reproduce the premise
Measure four cooler terminal temperatures, oil and water flow and relevant pressures. Identify bypass mixing, module combinations and pump state; installed flow follows the pump and system resistance together. [2]
Compare oil-side and water-side heat duties with uncertainty and heat loss to the surroundings. Resolve nonsteady conditions, sensor placement and flow errors before deriving an apparent exchanger coefficient. Combine measurement uncertainties on the common duty-difference boundary. [3]
Fluid duty is ṁcpΔT under the stated heat-capacity and steady-flow assumptions; input temperatures and flows belong in the performance guarantee. [1]
Reconcile the two fluid heat balances
Assumptions: steady oil flow 2 kg/s, cp = 2.0 kJ/(kg K), cools by 10 K; water flow 1 kg/s, cp = 4.18 kJ/(kg K), warms by 9 K. Duties are 40 and 37.62 kW, a difference of 2.38 kW or 5.95% of oil duty. Assume independent standard duty uncertainties of 0.8 and 0.6 kW, with ambient loss already corrected. Then udifference = 1.0 kW and the k = 2 interval is 0.38–4.38 kW, excluding zero. The assumed uncertainty cannot close this heat balance; investigate conditions and measurements before interpreting installed exchanger performance. [1] [3]
Assign the source of a shortfall
If flows and inlet temperatures match the factory conditions but duty differs, examine exchanger condition and measurement evidence. If installed inputs differ, calculate the resulting duty before treating the factory guarantee as failed. Fouling allowance and clean performance must remain separately identified.
References
- U.S. Department of Energy, DOE-HDBK-1012/2-92, Thermodynamics, Heat Transfer, and Fluid Flow, Volume 2, 1992.
- U.S. Department of Energy, DOE-HDBK-1012/3-92, Thermodynamics, Heat Transfer, and Fluid Flow, Volume 3, 1992.
- B. N. Taylor and C. E. Kuyatt, NIST Technical Note 1297, Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results, 1994, sections 5 and 6.