Characteristics of the ventilation in poultry buildings have been studied at the Hungarian Institute for Building Science. The pressure loss of the cross-building ventilation flow is determined for a section of a typical building and for two typical air inlet-outlet layouts. On the basis of velocity measurements the local hourly air change rates were determined in the cages and compared to the general air change rate in the building.
By observing animal housing in severely cold conditions it was realised that an airtight building with mechanical ventilation did not provide the optimum solution, but better results were obtained from porous buildings. Reports aninvestigation made on a large model building simulating the humidity and temperature conditions in animal housing during winter. The model had a porous ceiling of flax straw.
Presents a simple model for the calculation of wind induced ventilation. The model requires as input, pressure coefficient data, wind direction, and the open areas for each element of the building. Gives an example of the model applied to a model livestock building. Gives flow chart and listing of computer program. Note model does not include temperature effects.
Discusses the mechanisms of natural ventilation. Gives equations for stack effect and ventilation due to wind. Discusses use of natural ventilation in livestock buildings. Shows how minimum and maximum ventilation rates for winter housed cattle can be calculated using physiological data and a model for calculating the critical temperatures. Gives sample calculation of the ventilation rate necessary for beef cattle housed in a 9m. wide building.
The open ridge is a ventilator commonly used in cattle buildings. Reviews literature on the open ridge. Finds that there is outright disagreement between the sources referenced. Describes wind tunnel study to show whether or not the ridge design could influence the pressure coefficients when subject to wind. Finds there is no practical difference in pressure coefficients generated at the ridge of a building whether there are no upstands, upstands alone or with caps. For a 0deg.
Animal houses such as piggeries and cattle sheds are commonly ventilated using extraction fans in the ridge of the building. Fresh air is introduced through wide openings. These openings are screened by a baffle. Describes improved design of baffle which caters for a constant pressure difference between the inside and outside of the house.
Increasing use is made of open front or cold confinement buildings for fattening beef cattle. Reports model study of an open front beef confinement building a) to evaluate the effects of ridge vent design on airflow characteristics and temperature and b) to determine prediction equations forthe relationship between wind velocity and outlet velocity. Reviews literature on the subject. Compares results with previous studies. Discusses relationships between outlet velocity, wind speed and temperature difference. Recommends open and baffled ridge vents.
Compares methods of calculating ventilation rates in mechanically ventilated animal houses. Ventilation rates in several occupied animal houses were found by 1) measurement of internal to external temperature and moisture differences using a psychrometer;2) measuring decay rates of radioactive krypton as a tracer gas;3) estimating from manufactures rating of fans. Concludes that different methods agree to within the order of 5 or 10% and suggests the use of psychrometer techniques for simplicity.
Describes the ventilation of buildings by analogy with electric circuits and derives expressions for ventilation with and without flow through ducts in the roof. Finds that in general ventilation rate will vary linearly with wind velocity. Considers the effect of shelter belts on wind velocity and derives expression for sheltered ventilation rate. Suggests that eddy motion caused by shelters may be important. Gives measurements made on models in wind tunnels to show the affect on wind pressure of sheltering buildings at various distances.
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