15 April 2019

Methods used to calculate airflow in the aeronautical and motor industries have been tested for calculating the airflow in animal houses, in this case poultry houses with tens of thousands of chickens. With excellent results.

Chickens inside the poultry house
Chickens inside the poultry house
Roland Gårdhagen, assistant professor in the Division for Applied Thermodynamics and Fluid Mechanics, has been carrying out research in a slightly unusual area. His usual projects involve, for example, airflow and turbulence around aeroplanes and trucks, and blood flow inside blood vessels.

Vreta Kluster, centre of expertise for the green industries, has been awarded research funds from the Swedish Farmers’ Foundation for Agricultural Research for several projects to seek solutions to challenges in the poultry industry. One of them, the Digital Poultry House, requires Roland Gårdhagen’s expertise.

The egg producers had themselves defined two problems – moisture and high levels of ammonia in the buildings – and a first phase of the research project confirmed these.

“We examined a modern and newly built poultry house with 36,000 chickens, and confirmed that the level of ammonia was high during much of the winter”, says Max Jamieson of the Rural Economy and Agricultural Societies.

Digital Poultry House project

Together with Roland Gårdhagen and Malin Alm, project manager at Vreta Kluster, he has participated in the Digital Poultry House project. They have gathered a number of people from the industry to a workshop to obtain feedback about their work.

Shell eggs are a nutritious and convenient foodstuff in which Sweden is self-sustaining. The eggs that we purchase and eat have not undergone long transport, but come from Max Jamieson and Roland Gårdhagen at Vreta Kluster.chickens reared close to the consumers. However, in order to enjoy good health, the chickens need well-functioning ventilation, just like humans.

“Damp bedding is a major source of ammonia”, Max Jamieson tells us.

Roland Gårdhagen constructed a model of an animal house in a computer, based on a large poultry house in east Sweden.

“We use the same methods, the same physics and the same software that we normally use when calculating flows. They must be adapted to the application, of course, whether it is airflow around a truck, blood flow in a blood vessel, or ventilation in an animal house”, he says.

“We cannot, however, include 30,000 chickens in the model, so we instead simulate their effects. We include the heat produced by the chickens, ammonia from droppings on the floor, and carbon dioxide from the shelves and nests where the chickens are. Other parameters in the model are air intake, ventilation, additional sources of heat, etc.”

A generic model

The result is a model that demonstrates how the air spreads through the animal house and where it is extracted, together with large quantities of particles. The model shows locations that are too warm or too cold, if there are any draughty spots (which chickens don’t like), and places that the airflow doesn’t quite reach (which are probably therefore places where moisture collects).

The model is generic in the sense that it is possible to change the dimensions of the building, construct dividing walls, change the roof angle, and move the interior fittings around. This means that it can be used for other types of animal house, everything from poultry to pigs and cattle.

The difficulty of achieving effective ventilation in animal houses is well known, and how important the ventilation is for the chickens, in this case, to fare well and lay eggs.

“The ventilation system must remove carbon dioxide and ammonia, and supply fresh air to all the animals in the building”, one of the participants in workshop, Sivert Johansson, points out. He has long experience as a specialist in the ventilation of animal houses.

Increased focus on animal welfare

The model aroused the interest of the participants at the workshop, in that an increased focus on animal welfare has caused many poultry farmers to rebuild their poultry houses. New regulations for animal husbandry from the EU are in the pipeline, and the use of a digital model for simulation, before starting to refurbish or build, can both save money and prevent frustration.

“How long does it take to get results from the model?” asks a participant.

“It’s difficult to give a clear answer. Simple calculations can probably be completed by a powerful desktop in a week or so, while more advanced calculations, including seasonal variations in the outdoor temperature, need supercomputer capacity”, Roland Gårdhagen tells them.

Max Jamieson is careful to tone down expectations.
“What we’ve done so far is just an initial test to see whether the model works, and we have shown that it does. Now we need new research funds for the next step, and maybe also to ensure that a commercial product comes out of the work. We want to continue at a high academic level, but we are aware that the results must be useful for people in the real world”, he explains.

For Roland Gårdhagen the results will also mean an academic publication, because it’s clear that there is quite a lot of research in this topic – in Brazil, the Czech Republic and Spain. There is, however, a huge and growing need in a world in which animal welfare is becoming evermore important, while the number of people we need to feed is increasing.

Translated by George Farrants

Simulation of airflow in a poultry house, shows temperature and flow of particles. Illustration Roland Gårdhagen.

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