Industrial curing and process ovens are among the most energy-hungry machines on a factory floor. They hold product at precise temperatures\u2014often 150 to 250 \u00b0C for powders, paints, composites and food\u2014for minutes to hours at a time, and they do it continuously. Two things make them expensive to run: the energy needed to raise and hold the temperature, and the energy thrown away every time the ventilation system exhausts hot air to meet safety and product-quality rules. The good news is that ovens are also highly recoverable, because the duty is steady and the exhaust is hot and predictable. The trick is understanding that an oven has two distinct air loops\u2014recirculation and make-up\u2014and the recovery strategy is different for each. This article sets out how to recover oven energy without compromising cure quality or safety. For the broader industrial picture, see our industrial heat recovery guide<\/a>.<\/p>\n A curing oven constantly recirculates a large volume of air through the product zone to keep the temperature uniform; only a fraction is exhausted to control volatile organic compound (VOC) concentration and moisture. That recirculation loop keeps the heat where it belongs and is the first line of efficiency\u2014good oven design minimises the exhaust fraction while staying within the fire and health limits set by the process and the authority having jurisdiction.<\/p>\n The make-up air loop is where energy is lost. As hot air is exhausted, an equal volume of cooler outdoor air must be heated and introduced to replace it, and that replacement air is heated from scratch every cycle. In winter this make-up air load can rival the curing load itself. Recovering heat from the exhaust to preheat the make-up air is usually the single biggest saving available on a continuous oven. Good heat exchanger selection<\/a> here means matching the core to a dirty, hot, possibly VOC-laden airstream.<\/p>\n For most ovens the practical recovery device is a robust air-to-air plate or tube exchanger mounted in the exhaust stack, preheating the incoming make-up air before it reaches the burner or electric heater. The exhaust is hot enough that even a modest-effectiveness core reclaims a large absolute energy quantity. Where the two ducts are far apart, a run-around coil loop moves the energy through a fluid circuit instead. The table below contrasts the two strategies.<\/p>\nTwo loops, two opportunities<\/h2>\n
Recovery tactics that work<\/h2>\n