Nonlinear inverse problem of reconstructing transport coefficients

The inverse coefficient problem for the quasilinear heat-conduction equation is solved numerically.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 6, pp. 909–915, December, 1985.     

Integrated modelling under uncertainty in watershed-level assessment and management.

Uncertainty in water quality model predictions is inevitably high due to natural stochasticity, model uncertainty, and parameter uncertainty. An integrated modelling system (modified-BASINS) under uncertainty is described and demonstrated for use in receiving-water quality prediction and watershed management. A Monte Carlo simulation was used to investigate the effect of various uncertainty types on output prediction. Without pollution control measures in the watershed, the concentrations of total nitrogen (T-N) and total phosphorus (T-P) in the Hwaong Reservoir, considering three uncertainty types, would be less than about 4.4 and 0.23 mg L(-1), respectively, in 2012, with 90% confidence. The effects of two watershed management practices, wastewater treatment plants (WWTP) and constructed wetlands (WETLAND), were evaluated. The combined scenario (WWTP + WETLAND) was the most effective at improving reservoir water quality, bringing concentrations of T-N and T-P in the Hwaong Reservoir to less than 3.4 and 0.14 mg L(-1), 24 and 41% improvements, respectively, with 90% confidence. Overall, the Monte Carlo simulation in the integrated modelling system was practical for estimating uncertainty and reliable in water quality prediction. The approach described here may allow decisions to be made based on the probability and level of risk, and its application is recommended.     

Characterisation and biological treatment of greywater.

Characterisation of greywater was conducted in two different greywater streams in the Netherlands (Groningen and Sneek). The concentrations of macropollutants and nutrients measured were very different in both streams; in particular the COD was 425 mg/L in Groningen's water whereas in Sneek it was 1,583 mg/L. The aerobic treatment of greywater in a fed-batch reactor led to a 90% removal of COD at different organic loading rates. Anaerobically, the removal reached 40% COD removal on average, the possible reason being the high amount of surfactants present in the influent.     

Thermal interactions between water and rock in an underground hot-water store

Storing solar or surplus heat in enormous unlined rock caverns has attracted considerable interest in Sweden. A comprehensive research programme on this subject has been running since 1982 in the city of Avesta, where a district-heating system has been completed with a hot water accumlator blasted in the rock. In the present paper it is shown that, if the cavity is assumed to be spherical, the complete mathematical formulation of the dynamic interaction between the temperatures of the stored water, of the rock mass and of the supply power can be solved. The results yield expressions for the rate of change of temperature, for time constants expressed in terms of the thermal properties of the rock and the water and linear dimensions of the cavity. For a relatively small store, like the one in Avesta (15 000 m³), the time for spontaneous cooling is extremely long (> 10 years). For big commercial stores it is even longer.     

Equilibrium distribution of water in the two-phase system supercritical carbon dioxide–textile

When natural fibres are dyed in supercritical carbon dioxide, the addition of a small amount of water increases coloration. For a process design it is important to know how much water has to be added to obtain a desired humidity of both textile and carbon dioxide. In this work a thermodynamic model is proposed to calculate the distribution of water over the textile phase and the supercritical phase as a function of pressure and temperature. The phase equilibrium is described with Raoult's law for non-ideal fluids. The absorbed water in the textile is a condensed phase and is modelled here as a non-ideal liquid, using the NRTL-equation. The non-ideality of the supercritical phase is described by a solubility enhancement factor, a new equation derived from statistical thermodynamics. Although the model is applied to cotton, viscose, silk and wool, it can be used for all water absorbing textiles.     

Countercurrent water-heating system with a heat exchanger in a solar energy collector loop

The counter current heat exchanger theory with periodic inlet temperatures has been applied to analyze the thermal performance of a water heating system. The theoretical results obtained are in agreement with the experimental data reported in the literature.     

Preserving poultry feeds in the humid tropics: A trial of calcium propionate under feed mill conditions

Calcium propionate was incorporated into a complete poultry feed and a feed concentrate at levels of 0, 0.3, 0.4 and 0.6%. The feeds were stored in 25 kg woven sacks in a feed mill. Air temperatures ranged from 22 to 34°C and relative humidity was in the range 67 to 93%. Mould growth was measured microbiologically and by measurement of feed temperature. Calcium propionate had a large effect on the microbiological measurements but only a small effect on heating in the feeds. As a preservative, it retained its activity for 6 weeks which extended the storage life by only 1 week in this case. The relative merits of the microbiological and temperature measurements are discussed.