Clean steam condensing, condensate recovery and feedwater heating. Steam duty looks like the simplest condensing application until air in-leakage and inadequate drainage get involved, at which point it becomes one of the most commonly misdiagnosed.
Distillation, fractionation and knock-back condensing. On a column the condenser is not a utility bolted to the end of the process — it sets the reflux ratio, and reflux sets the separation and therefore the product purity.
Solvent, VOC, waste gas and hazardous vapor recovery plus emissions abatement. Condensing recovers material worth money and cuts the load on carbon beds and thermal oxidizers, so these units often pay for themselves twice.