Heat exchangers may be right for cage-free layer houses

Cage-free layer houses provide more room per hen than do cage houses. Learn how a heat exchanger can be used to transfer heat from exhaust air to incoming air during winter months to reduce heating costs and maintain good air quality for cage-free houses.

A heat exchanger allows for the fresh cold air from outside the layer house to be preheated by the warm exhaust air. | Courtesy of Vencomatic
A heat exchanger allows for the fresh cold air from outside the layer house to be preheated by the warm exhaust air. | Courtesy of Vencomatic

The body heat given off by cage-housed hens is often sufficient for maintaining adequate temperatures and air quality in wintertime in belt-battery housing. Cage-free housing systems give birds more room, which means less heat is produced by the hens per cubic foot of house space. Also, the litter or scratch area of a cage-free house will result in the production of more ammonia and dust than is generated in a cage house with manure belts.

Controlling ammonia in a cage-free layer house is generally accomplished by keeping the litter area dry and increasing house ventilation. This increased ventilation rate coupled with less bird body heat per cubic foot means that many cage-free layer houses will need supplemental heat in cold weather. Heat exchangers provide the opportunity to transfer heat from exhaust air to fresh air brought in from outside to reduce heating costs.

Conserving heat while maintaining air quality

Heat exchangers are found all around us, in our car engines, factories and even to heat and cool our homes. Broiler houses in Canada have used heat exchangers for over 10 years, while the layer industries in the EU and other parts of the world have over 25 years of experience. However, U.S. egg producers have not traditionally used this technology. Improvements in design and efficiency coupled with increased building and retrofitting to incorporate cage-free production systems have allowed an opportunity to revisit the concept. New equipment installations in the U.S. are being made incorporating heat exchanger technology.

In basic terms, the heat exchanger works with fresh incoming air being heated by exhausted air being removed from the building. The two air streams are directed into channels or tubes of plastic or aluminum that conduct heat and prevent air flow cross-contamination. By using heat generated within the house, costs to warm the building are greatly reduced in the winter. Several equipment manufacturers offer different designs and approaches to the concept.

US heat exchanger installation

The Van Vuuren family has recently installed two Vencomatic heat exchangers in a barn in the upper Midwest that was retrofitted to an aviary system with the manure belt drying feature. As they plan to pass their operation to the next generation, the Van Vuurens looked for solutions that would be cost-efficient to operate and offer equipment longevity. Temperature ranges in the area are from -30 F to 100 F. There have been no operational issues this past winter, despite some very cold periods.

The only negative observation they report since last fall has been an increase in dust inside the house on some warm days due to manure becoming even more dry than normal. Mrs. Van Vuuren mentioned, “The ammonia levels are much lower due to the lower humidity. Litter quality is much better with the Clima+ unit. The environment is much better for both the birds and workers.”

Vencomatic has installed several heat exchanger units in the U.S. and claims 80 percent thermal efficiency. Producers are encouraged by the company to combine the heat exchanger with a manure belt aeration system. Pre-heated by normally wasted heat from exhaust air, warm fresh air is piped to manure belts under an aviary system to dry manure while still in the house and provide fresh warm air to the birds. Air brought in from outside in the wintertime will have lower relative humidity than house air, so using heated outside air will dry the manure more quickly than house air will.

As environmental contamination is becoming more closely scrutinized the heat exchanger incorporates filter systems to capture dust (particulate matter) from exhausted air reaching 80 percent efficiency.

Supplemental heating

Heat exchangers do not entirely eliminate the need for supplemental heat. Vencomatic employs a propane fired pre-heating unit to heat incoming air when temperatures fall below 15 F.

Maarten Vlug, engineer, Jansen Poultry Equipment, notes that in Jansen’s heat exchanger design, “With those low temperatures (under 5 F), we use a water or gas heater after the heat exchanger to get the temperature close to 64 F before the air enters the house. As for our heat exchanger, I would recommend installation inside the house with temperatures lower than -4 F or an external enclosure that is well insulated. At very low outside temperatures, the water supply will be shut off to prevent damage to the water or brush cleaning system.”

Dealing with dust                                                             

One concern with heat exchanger technology has been the ongoing cleaning and maintenance required to keep systems from plugging or clogging up with dust. “Cross-flow heat exchangers always have pulse jet air filters which are automatically cleaned by pulses of air. But the downside is that use of filters will create a high counter pressure, thus requiring stronger fans,” noted Vlug.

Jansen has an additional cleaning option that includes a patented automated brush system in combination with water flushing. Vencomatic has designed an automated flushing system which uses water to clean dust between the panels once a week.

In warm weather, when supplemental heat is not needed, the heat exchanger can be bypassed to eliminate the need for cleaning the system.

Payback period

Victor van Wagenberg, product manager, Vencomatic, estimates that the payback period for the complete heat exchanger system, including a pre-heating section, is from 3 to 5 years depending on customization requirements, energy prices and weather. The company’s heat exchangers are sized according to house design with the maximum number of hens per unit set at around 42,000. Houses with more birds are fitted with multiple units in order to keep air flow distances and efficiencies optimized.

As U.S. egg producers install cage-free systems, they are learning of the need to adapt many aspects of management and environmental control. Perhaps heat exchanger technology will find greater acceptance as a cost-effective tool that improves the production house air quality for both birds and those who care for them.


Learn more: 5 questions about cage-free hen health, welfare: www.WATTAgNet.com/articles/31143



Caption: A pre-heater can be added to a heat exchanger to provide the supplemental heat required to maintain good air quality in the layer house when it is extremely cold outside. | Courtesy of Vencomatic


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