Conference article

With improved greenhouses; farmers have to ventilate. An air-to-air multi-tube counter flow heat exchanger unit was installed in a greenhouse used for the experimental cultivation of hydroponic tomatoes and cucumbers. This 24m long unit involves a 12” O.D. external shell used to exhaust moist air and five inner tubes to bring fresh air inside. The tests; carried out between March and May in a 576 m3 enclosure; demonstrated that average efficiencies of ?=84% and ?=78% were obtainable with air volumetric exchanges rates of 0.5 and 0.9 change per hour; respectively. Latent heat was found to play a major role in the overall heat transfer; contributing about 40% of the total energy exchanged in some situations. The exchanger could be buried underneath the ground or suspended above the crops. The unit made of plastic is durable; rot and rust resistant; affordable; and is ice and frost compliant. A pre commercial implementation with an improved design is now considered in collaboration with Gaz Metro. This paper presents the original prototype that help in reducing the consumption of natural gas; fuel; bunker; or propane.

Heat exchanger; Latent heat recover; Sensible heat recovery; Plastic