The dairy plants of type MVA 1930 are compact structures with a floor area of 92mx120m. Despite this size the dairy plants - with the exception of certain special areas - can be naturally ventilated over long periods of time. The pen climate parameters for a mechanically and a naturally ventilated plant of the above mentioned type are essentially similar. It seems, therefore, unfounded to restrict natural ventilation to buildings of a certain width. It is rather the formation of the envelope of the building which should be seen as the deciding criterion.
The bacterial content of the air and physical environment of two crated veal calf units were monitored over the growing period of 16 weeks. The rate of release of bacteria colony forming particles (BCFP) from the calves was rapid.
A control program for a natural ventilation system for agricultural buildings is described which calculates a required ventilation rate, then adjusts vent openings to achieve this ventilation rate with equally distributed flows.
Discusses the established principles and rules of air hygiene for animal housing and areas in which guidelines have yet to be devised. The most common pollutants are ammonia, hydrogen sulphide, methane and carbon dioxide. Dust and aerial microbial flora also have to be considered. Ventilation criteria for pigs and poultry and for cattle, sheep and horses are discussed. The current threshold limiting values for noxious gases and inert dust which could be used in the design and operation of livestock buildings are based on studies of humans rather than farm animals.
The objectives of a ventilation system are to provide an aerial environment in which 1, animals' health and productivity can be maintained, 2, the stockman's comfort and health needs are satisfied, and 3, the building and equipment are protected from damage. Criteria for evaluating ventilation include: thecontrol of air temperature and air speed at animal height, the control of relative humidity and prevention of condensation, and the maintenance of tolerable concentrations of gases, dust, and airborne microorganisms.
A livestock building for 30 cows in loose housing was constructed in 1982. In the cow stable natural ventilation is provided through openings along the eaves. New types of inlets and outllets have been designed for natural ventilation systems. The regulation system for the air flow rate is a modified P-type regulator. Using timesharing of the regulation function, the inlet areas can be regulated in groups by means of four different temperature sensors in the building.
Instruments full-scale agricultural and horticultural buildings with surface pressure sensors to measure wind loads under natural wind conditions. To show the effect of building geometry on wind loads, presents results of pressure coefficients on a selection of these buildings. The results in this report relate to transverse wind direction only. Shows that wind load does not reduce to a function of the geometric variables of height/span and roof pitch.
Studies the ventilation of 9 air-conditioned animal rooms used for both housing and experiments. Samples dust, measures ventilation rate by anemometers and by tracer gas decay, and uses settle plates to determine the number of airborne bacteria. Detects a high amount of pariculate matter emanating from the animals which might sensitize personnel working in these rooms. Previously, attention has been paid to the ventilation requirements of the animals but where people also spend several hours in animal rooms then safety conditions for staff must be considered.
Uses a similitude approach to develop predictive graphs for the ventilation rate due to the stack or chimney effect. Uses a half scale model of an open side wall structure with a continuous and restricted open ridge, and finds that:< 1. Ventilation rate is approximately proportional to ridge outlet width< 2. Outlet Reynolds number response ie ventilation rate to changes in Grashof number is a function of the ratio between building height and ridge width.
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