No description available.

Pig production in Malawi and in most of the developing countries is shifting increasingly from pasture or dirt lot to total confinement with improved housing facilities. Keeping pig level temperatures within the comfort zone in hot weather is a common problem in naturally ventilated intensive pig buildings. Automatically controlled natural ventilation (ACNV) has proved to be effective in reducing the problem of heat build up in pig houses and is becoming very popular. However, a method for reducing summer temperatures at animal level in non-automated naturally ventilated intensive pig buildings has not been developed. An attempt was made to develop a natural ventilation system which would maximise the cooling effect of wind at animal level by manual control in buildings suitable for the Tropics. The research project was conducted in three stages: (1) air flow pattern studies, using 1:20 scale two-dimensional models, (2) wind tunnel testing, using three-dimensional, 1:20 scale models with simulated pigs, and (3) validation of results from the wind tunnel studies made with a 1:4 scale model, put out in the field. Air deflectors were used as a means of increasing the effect of wind on the ventilation pattern in the models. Monopitch, duopitch and offest gable models were tested in the water table, and monopitch models were tested in the wind tunnel. The use of air deflectors in monopitch and offset gable models showed a marked increase in airflow towards the animal zone area and a reduction in the difference between the surface temperature of the model pigs and the outside air temperatures. The deflectors improved the performance of the models by about 10% with the front orientation and about 20% with the rear orientation. In the duopitch model an increase in the roof overhang improved flow circulation on the leeward side. The use of air deflectors also improved flow circulation on the leeward side. The wind speed and air temperature at the experimental site for the 1:4 scale model were used to validate the results from the wind tunnel tests. The measured temperature values showed similar response curves to the predicted values. Temperature differentials increased with an increase in the angle of the deflector.

There is no abstract available for this dissertation.

In the present climate of energy conservation and CO2 emission consciousness, building heating, ventilating and air conditioning (HVAC) systems are required to achieve thermal comfort and indoor air quality in the most energy efficient manner possible. To this end optimising the use of natural ventilation is considered an area which can significantly reduce both the occupants discomfort and the energy consumption. The ability to effectively control the indoor environment would considerably enhance the use of natural ventilation. The overall aim of this research is to develop, commission and evaluate a fuzzy rule-based controller which can vary the resistance of ventilation opening in order to maintain an acceptable comfort conditions in the occupied space. The design of the fuzzy control system starts by establishing certain quantization levels for the input/output variables along with corresponding membership functions. Aspects of input and output variable choice together with their linguistic labels are explained and presented. Control rules are defined based on the off-line thermal modelling, experimental results and through discussions with experts. A dynamic air flow distribution is investigated through a series of experiments for different environmental conditions and opening levels without any control action. Three rule-bases of different complexity are developed and presented. All solutions are simulated in an input-output space and their differences presented in more detail through examples of the Mamdani inference method application. Controller validation is initially carried out using simulation as this offers the possibility of testing controllers under extreme conditions regardless of test room physical limitations. Simulations are carefully designed to allow simultaneous comparison of different controllers' performances. Then on-line validation is carried out in the test room by measuring the air flow distribution with and without the controller in action. A naturally ventilated test room and its instrumentation is set up. A controller commissioning methodology is established, involving the choice of software and hardware platforms and data acquisition methodology.

No description available.

Thesis (MEng)--University of South Australia, 1998

Thesis (MEng)--University of South Australia, 1998

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Tekniska högskolan, 2006. / Härtill 7 uppsatser.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.