Journal of Cold Regions Engineering

Spray freezing technology has been used in ice building construction in cold regions and artificial snow making. The spray freezing process involves heat and mass transfer and ice nucleation. The freezing temperature of the sprayed water is influenced by many factors, such as droplet size (volume), ambient air temperature, and impurity content of the water. An experimental study was carried out to investigate the influence of the droplet size (volume) and the ambient air temperature on the ice nucleation temperature of the freely suspended droplets of different qualities—piggery wastewater, pulp mill effluent, and oil sands tailings pond water. The time required to initiate freezing in the freely suspended wastewater droplets was measured under various experimental conditions using video-image technology. The ice nucleation temperature of the droplets were predicted based on the required freezing time and the rate of heat and mass transfer.

Bioremediation of petroleum-contaminated soils in cold regions is hampered by low temperatures, frozen soils, and short summers. Extreme environmental conditions limit remedial efforts to a few technologies. Bioventing and combined air-sparging and soil vapor extraction have shown promise in subarctic regions. Expensive thermal desorption or encapsulation of organically contaminated soil is practiced in arctic Alaska and Canada, in lieu of successful bioremediation. Thermal insulation systems have recently been developed for innovative bioremediation efforts in cold regions. Commercially available insulation, electrical heating elements, and construction materials have been uniquely packaged to enhance bioremediation at two petroleum-contaminated sites in Alaska. Thermally enhanced bioventing successfully remediated hydrocarbon contamination in the vadose zone at a subarctic site within two years. Preliminary results from an oxygenated and fertilized biopile, actively warmed and covered with a thermal insulation system, shows promise at an arctic site. A guide for thermal insulation system design for bioremediation application in cold regions is developed.

A method is proposed for estimating rates of sediment transport in ice-covered alluvial channels. The method extends existing, open-water procedures for estimating rates of sediment transport to conditions of ice-covered flow. A key aspect of the method is the assessment of flow resistance attributable to bed-surface drag. That assessment is used to estimate rates of bed load and suspended load, and thereby total bed-sediment transport rate. Estimation of ice-covered suspended load additionally entails an approximation whereby open-water suspended load is scaled in proportion to the ratio of a reference sediment concentration for ice-covered flow relative to that for open-water flow. The reference concentration is calculated in terms of bed-load rate and shear velocity attributed to bed-surface drag. Flume data are used to develop the method and tentatively verify it. Field verification of the method presently is hampered by the absence of field data on bed sediment transport in ice-covered channels.

The experimental data indicate that water in freezing or thawing wet soils undergoes a gradual phase change. The mathematical forms of reported correlations of the unfrozen water content of soils varies from researcher to researcher. An improved theoretical treatment of the gradual freezing/thawing process provides insight into the mechanism of the gradual phase change of water in wet soils and a proper means of correlating experimental measurements. Direct numerical solution of the resulting ordinary differential equation may provide accurate prediction of the unfrozen water content of wet soils, when accurate soil property data are available. Two approximate analytical solutions are derived using average thermal properties of the soil constituents. The simpler of these analytical solutions is applied to various data and shown to be sufficient for all practical purposes. The analysis presented in this article demonstrates that the unfrozen water content can be adequately correlated by means of an exponential decay function shifted by the amount of the water adsorbed over the soil grains, which cannot freeze.