The sensitivity of Arizona-grown grapefruit to chilling temperatures varied throughout the harvest period studied. This sensitivity was high in October, decreased in November and December, then increased in February. In April and May there was another decrease in sensitivity to chilling temperatures. Coating fruit with vegetable oils or fats successfully delayed the development of chilling injury and reduced the degree of injury, however, vegetable oils applied as water emulsions were even more effective in preventing chilling injury to 'Redblush' grapefruit extending the period of marketability more than 100 days. Postharvest application of CaCl₂ and certain plant growth regulators significantly increased the resistance of 'Marsh' grapefruit to chilling injury, but less so than oil emulsions. Scanning electron microscope photomicrographs of 'Marsh' grapefruit peels showed that severe chilling injury was a depressed area of collapsed cell, just beneath the epidermis layer. As the severity of chilling injury increased, non-collapsed cells gradually increased in size. Cell walls were irregularly shaped; thin in some areas and thick in others. Oil glands in depressed areas were not ruptured during cold storage. Hence release of toxic materials through rupturing of oil glands is not a factor in chilling injury. Compared to non-injured tissue, injured tissue from the same fruits had significantly lower water and osmotic potentials, and low, near zero, turgor pressures. There was a significant negative correlation (r = -0.5; p < 0.05) between the water potentials of the peels and the percentage of 'Marsh' grapefruit with severe chilling injury during storage at 2.8C. Ion leakage tended to increase during cold storage, and when the fruit were transferred to room temperature. Internal conductivities declined sharply during cold storage and then increased very strongly during periods at room temperature.

This thesis report outlines the creation of a MATLAB tool to design reversible machines that can function as both wind turbines and as agricultural frost protection fans. Frost protection fans are used to prevent crop loss during radiative freeze events during which a temperature inversion is present. Such a dual-purpose machine fundamentally has the constraint that it must use symmetric airfoils, so a suite of tools for automatically designing an optimized wind turbine blade with symmetric airfoils using the Blade Element Momentum (BEM) theory approach is presented. The BEM code is then re-derived and adapted for use with a frost protection fan, which is analogous to a propeller at zero free-stream windspeed. The relative performance of a blade operating in fan mode is investigated using a turbulent jet entrainment model to predict the time-averaged temperature rise provided by the fan during a thermal inversion event. With these tools, an optimal configuration of blade pitch angle, rotor tilt angle, and tower height can be found for a given wind turbine blade. The models are incorporated into a cohesive program with a graphical user interface. The feasibility of such machines is found to depend heavily on the wind resource at a given site.

This thesis deals with the Air to Ground Heat Exchangers (AGHEx) and their effects on the hygienic quality of the supplied air and the microbial microclimate in the interior of buildings. The theoretical part focuses on current findings and knowledge in the field of warm air heating, ventilation of the low-energy and energy passive houses and ground heat exchanger for the ventilation systems to family houses. The next chapter deals with the quality of the indoor environment and the influence on HVAC systems on the building microclimate. The experimental part of the thesis presents the results of energy simulations of operation of air to ground heat exchanger, obtained using the simplified model, and the data from long-term monitoring of experimental AGHEx built at FME BUT. Furthermore, the results of microbiological research of several already operating air to ground heat exchangers are evaluated. The research was carried out using two different sampling methods: the method using swabs taken from the pipe wall, and the sedimentation (gravimetric) method. The conclusion part mentions the practical experiences of users and knowledge of the author relating to the design, operation and use of air to ground heat exchangers.