Predicting the Heat-Exchange Intensity in the Biogas Production

Abstract

The intensity of the heat exchange between the internal thin-wall vessel and the experimental liquid medium has been studied. The mixture of the distilled glycerol, the substrate from the operating biogas plant, the fresh chicken manure with the moisture content of W = 90 %, chicken manure with the moisture content of W = 90 % aged for 5 days and the chicken manure with the moisture content of W = 90 % aged for 13 days was used as the experimental liquid medium. The experimental-calculative method was suggested to define the coefficient of the heat loss between the internal thin-wall vessel and the experimental liquid medium using the method of regular thermal mode. The main problems peculiar for the methods of the definition of the heat-exchange intensity in the multi-phase and multi-component media in the food industry and in the biogas production have been analyzed. The heat-exchange intensity prediction methods available for the food industry are of great importance for heat and power computations. These methods refute the characteristics of the media and it has a great effect on the computation of their thermal and physical properties. Food products subjected to the thermal processes of sublimation, evaporation, heating and crystallization have the properties of solid, liquid and gaseous bodies and transform from one aggregate state to another and it has a substantial effect on a change of their thermal and physical properties. Biogas technologies are used by the multi-tonnage production. These technologies use huge volumes of the substrate with unknown thermal and physical properties. Contemporary development of biogas technologies raises the problems relating to the thermal stabilization of the process and prediction of the heat-exchange intensity. The productions pay much attention to the problems of the stable temperature mode in the bioreactor. The operation of the biogas plant requires a stable temperature mode at different ambient temperatures. The main requirement to the bioreactor is that the temperature fluctuations should be within certain ranges. The waste treatment of different productions, in particular heating, cooling, thermal stabilization results in the anthropogenic load on the environment due to use of the outdated and not upgraded heat process equipment. It is rather difficult to solve this problem because the thermal and physical properties of the mixtures, liquids, substrates and their chemical compositions and molecular structure are limitedly known or unknown. It is also unknown how these are changed during the thermal treatment and how environmental factors affect their change. Relative errors of the main values, in particular the heat loss coefficient, heat transfer coefficient, specific heat capacity, heat exchange surface area, cooling (heating) rate, nonuniform temperature distribution factor, heat flow, temperature rush, temperature difference, mass of the experimental liquid media, experiment duration and table values have been determined.