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Year-round operation the solar powered hybrid adsorption-compression refrigeration cycle

Cyklis Piotr, Duda Robert

Journal of Mechanical and Energy Engineering

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2019

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Vol. 3, No 4

317--322

EN

In our earlier papers a hybrid adsorption-compression refrigeration cycle was presented. The hybrid, two stages cycle is based only on the natural refrigerants: water and carbon dioxide. The main advantage of the hybrid cycle is that the carbon dioxide compression cycle is subcritical because during the year-round operation it is possible to maintain the condensing temperature below 20°C. During the hot season, this is achieved by adsorption cooling, during cold seasons the wet cooling tower is sufficient. Already several years of experience, allowed to gather a considerable amount of measurement data. The refrigeration system is working in our laboratory constantly since 2013. In 2015 the adsorption system was upgraded by the manufacturer. In 2017 frequency inverter for wet tower fan controlling was introduced. The refrigeration chamber was used for tests with different content and operation of the refrigeration chamber (loading and unloading). The assumed CO2 evaporating temperature was -35°C. The averaged for HT (High Temperature) part of the cascade (adsorption cycle only) COPHT=0.51 for the whole year 2018. This may be considered a very good performance. Averaged total COP for the cascade system: COP=0.9 compared to COP=0.84 for compression only refrigeration cascade, with much higher TEWI index. For comparison for two-stage compression (R407CHT+R744LT) cycle was used. This means that if the cooling tower fan operation is controlled using an inverter, adjusted to the actual heat removal demand, the hybrid cycle is not only ecological but also energetically efficient.

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Preliminary long-term predictive modelling of groundwater resources in view of climate change : a case study from eastern Poland

Duda Robert, Stanek Justyna

Geological Quarterly

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2019

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Vol. 63, No. 4

643--656

EN

The paper discusses an effective and simple approach to preliminary long-term predictive modelling to the estimation of the effects of predicted climate change on groundwater resources in aquifer recharged by rain infiltration for the end of the 21st century. The groundwater resources in an analysed catchment were assessed based on predicted precipitation and air temperature from seven climate change projections in two sets of the Intergovernmental Panel on Climate Change (IPCC) greenhouse gas emission scenarios (SRES), associated with various regional climate models (RCM). The predicted groundwater resources were obtained by diminishing the predicted renewable resources by recent environmental flows in a river dewatering the catchment. The predicted reserve was assessed taking into account the forecasted groundwater abstraction. The study revealed that the predicted groundwater reserve depended on the assumed prediction model, based on particular SRES and RCM ensembles. The groundwater resources in the study area at the close of the 21st century are expected to considerably decrease when compared to the reference period 1971-1990. The future groundwater reserve assessed by the climate change model based on IPCC emission scenario B2 connected with the regional climate model HIRHAM and regional climate model RCAO, may decrease when compared to the reference period, by 51 or 92%, respectively. In view of the IPCC emission scenario A2 assumptions, this preliminary predictive modelling shows that there may be a shortage of groundwater resources in the analysed catchment in the final decades of the 21st century.

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Assessment of factors affecting the intrinsic vulnerability of groundwater rated by the mean residence time estimation method

Duda Robert, Kowalczyk Paweł

Geological Quarterly

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2019

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Vol. 63, No. 1

126--138

EN

We analyse the factors used for assessing groundwater intrinsic vulnerability to pollution in the mean residence time estimation method, providing a final vulnerability evaluation. The following factors were analysed: depth to shallow groundwater, effective precipitation infiltration coefficient, terrain inclination, volumetric water content of soils and rocks in the unsaturated zone and volumetric water content of the topsoil. GIS surveys were performed for two geomorphologically diverse regions: a highland piedmont and a lowland plain in Poland (Central Europe). In both cases, groundwater had spatially diverse vulnerability to contamination. The research method used relied on determining the percentage participation of the area with particular values of the parameters analysed in areas of different degrees of vulnerability. Knowledge of the extent and distribution of variability of the parameters analysed in areas of particular degrees of vulnerability helps explain the causes of spatial variation in groundwater intrinsic vulnerability to contamination in given areas.

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Kilka uwag o modelowaniu matematycznym zlewni Raby

Duda Robert, Zdechlik Robert, Paszkiewicz Magdalena

Geologos

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2006

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Vol. 10

47--56

EN

The paper describes methodology of hydrogeological modelling of Raba river watershed, about 1565 km2 area, in flysch Outer Carpathians. Hydrodynamic model was a first step in procedure of point out groundwater bodies threatened with the risk of not achieving the European Water Framework Directive environmental aims. There was accepted conceptual model of recharge and groundwater circulation in fissured-porous sandstone-shale material, assuming that groundwater circulation could be reduced to a one aquifer in surface part of flysch rocks, connected with quaternary river valleys. There was adopted effective infiltration coefficient of selected types of surface material. There was pointed the importance of comparison the recharge defined by the infiltration method with underground runoff to rivers described by Wundt-Kille hydrological methodology. There was mentioned the effect of model scale on the precision of hydrogeological conditions projection.