Heat Rejection | Module 305
Shell-and-Tube Condenser Approach Audit
Field Status: Condenser approach temperature is the difference between the Saturated Condensing Temperature (SCT) and the Leaving Condenser Water Temperature (LCWT). If this value exceeds the manufacturer’s design specification, it is the primary indicator of fouled heat exchanger tubes.
Scaling creates an insulating barrier inside the tubes, preventing effective heat transfer. As scale thickens, the compressor must work harder, raising internal pressure and SCT, while the water leaving the condenser remains relatively cool. This inefficiency forces the chiller toward high-pressure cutouts.
SYS AUDIT: Condenser Approach Vector
APPROACH TEMP: —
FOULING STATUS: —
—
Fouling Dynamics
Condenser tubes require smooth, clean metal surfaces to facilitate rapid heat exchange. Minerals such as calcium carbonate precipitate on the tube walls, significantly raising the thermal resistance and driving up the SCT.
| Approach (°F) | Performance State | Required Maintenance |
|---|---|---|
| < 5.0 | Design Optimal | Routine monitoring. |
| 5.0 – 8.0 | Moderately Fouled | Chemical descaling pass. |
| > 8.0 | Critically Fouled | Mechanical brushing / tube cleaning. |
Diagnostic Gateway Challenge
The SCT is 115°F and LCWT is 95°F. The chiller is designed for a 5°F approach. What is the diagnosis?