In the technical field the energy balances are derived from the 1st thermodynamic law, which covers merely the instantaneous quantitative aspects of heat flows. In terms of energy conservation law these balances are expressed in the form of constant sums of exergy and anergy. And that is why they cannot, or can only to a very limited extent, be used to define the transformation of part of the energy (exergy) to the less valuable energy (anergy). Using the 2nd thermodynamic law we have a chance to trace the energy transformation through entropy, a quality indicator of every heat process and an accompanying symptom of process irreversibility. The plate air-to-air heat exchanger, whose exergy analysis is in the spotlight of our interest, operates, in terms of the laws above, in irreversible changes, while the change of entropy induced by the heat flows depends on the construction and surface of the heat exchange areas. The article analyses the influence of air inlet temperatures on the thermal exergy efficiencies of the heat exchanger and the heat loss exergy. Assessment is based on extensive measurements of the temperature, humidity and flow rate of the heated and cooled air in the plate heat exchanger. Both ...
The article presents results of modeling and operational evaluation of specific energy consumption in four pig breeding categories, which have been realized under the project QF 3200 „Expert System for Determination Support and Optimization of Technology Processes Control in Agricultural Production“ supported by Czech Ministry of Agriculture. The first step of solution brought mathematical equations that describe physical relation of specific energy consumption to machine input, technology cycle duration, total efficiency and day time operation. As example of energy requirements of material manipulation during feeding operation, mulch treatment are presented in equations 1 to 4. Following performed analysis based on calculated and operationally proved energy consumptions were created simple mathematical equations (tab. I) that qualify relation of specific energy consumption Q [Wh∙d-1∙ks-1] to recommended or standardized values of dry pasture mkr [kg∙d-1∙ks-1], wet pasture mkr,v [kg∙d-1∙ks-1], specific mulch production mmr [kg∙d-1∙ks-1], liquid manure mk [kg∙d-1∙ks-1], stable area S1,u [m2∙ks-1], disinfected area S1,z [m2∙ks-1], technology cycle duration τTC [d] and average animal weight mz [kg-1∙ks-1]. The elementary mathematical models come out from hypothesis that individual operation and technology cycles of agricultural production is possible to optimize on the base of theoretical knowledge adjusted by real ...
A forecast of socio-economic changes in agricultural holdings and sustain-able agriculture until 2030 was presented against the background of necessary energy and ecological changes occurring in rural areas and in the whole Poland.Results of Agricultural Census of 2010 (PSR'10) and initial results of Na-tional Census (GUS) of 2011 were used to determine the trends of changes in rural areas and in agriculture. It was forecasted that by 2030 about 39% of the population of Poland will live in rural areas constituting 33.0% of individual households. Farmer population in agricultural holdings over 1.0 ha AL will con-stitute 13.3% of rural communities and 5.2% of the whole country population. There will be about 530 thousand commodity farms (agricultural enterprises) which will supply to the market almost all commercial output of food raw materials. Introducing sustainable production and new technologies based on modern machinery aggregates will diminish unit labour and energy outlays, simultaneously contributing to an improvement of ecological requirements for soil, water, air, plants animals and human protection in rural areas. Agriculture will reduce methane (CH4) and carbon dioxide (CO2) emission to the atmosphere, among oth-ers through increased use of renewable energy sources (RES). A critical and re-served attitude should be adopted ...
