Aivars Aboltins

Mathematical Model of Deep-Bed Grain Layer Drying by Ventilation

The research work is devoted to matematical modeling the deep-bed grain drying process by ventilation. The purpose of research is to determine the thicknessof the first and the next stew upon grain layers dependent on different grain moistures. The mathematical model encloses a set of four partial differential equations which contain grain and air temperature, grain moisture and air humidity. Initial and boundary conditions for the system are constant values. The system with initial and boundary conditions is solved numerically by weighted time and space finite differences. The permissible thickness of the first and the next strew upon grain layers for various grain moistures that doesn’t provoke grain deterioration is fixed. It is 1.5–2 times greater as that is used in production.

Special Splines of Hyperbolic Type for the Solutions of Heat and Mass Transfer 3-D Problems in Porous Multi-Layered Axial Symmetry Domain

AbstractIn this paper we study the problem of the diffusion of one substance through the pores of a porous multi layered material which may absorb and immobilize some of the diffusing substances with the evolution or absorption of heat. As an example we consider circular cross section wood-block with two layers in the radial direction. We consider the transfer of heat process. We derive the system of two partial differential equations (PDEs) - one expressing the rate of change of concentration of water vapour in the air spaces and the other - the rate of change of temperature in every layer. The approximation of corresponding initial boundary value problem of the system of PDEs is based on the conservative averaging method (CAM) with special integral splines. This procedure allows reduce the 3-D axis-symmetrical transfer problem in multi-layered domain described by a system of PDEs to initial value problem for a system of ordinary differential equations (ODEs) of the first order.

MANURE MANAGEMENT SYSTEMS AND NITROGEN EMISSIONS IN LATVIA

The information for the present overview on manure management in different countries was primarily gathered through a survey using Greenhouse Gas (GHG) Inventory reports. In Latvia, N2O emissions from manure management account for only 5 % of total N2O emissions. Dividing the N2O emissions by all livestock species, 75.9 % are produced by cattle, 12.67 % – by poultry, and 4.96 % – by pigs. In GHG Inventory reports, there are great differences in manure output calculations for all livestock species in different countries (V, % ≥ 20), because all livestock is included in the same group, without separating them according to age or size. Majority of the countries have adopted a significantly higher amount of excreted N with manure from dairy cows as compared to the norms set in Latvia. Especially large differences among the countries can be observed in the groups of fattening pigs and weaned piglets; therefore, additional clarifications are needed for Latvian regulations, as the normative data currently adopted in Latvia is outside the 95 % of the value range. Keywords: GHG, manure, nitrogen emission. Article DOI: http://doi.org/10.15544/RD.2015.047

INFRARED DRYING OF RHUBARBS CUBES

In order to obtain dehydrated products of high quality, infrared drying in rhubarb cubes was researched at different sample thicknesses with IR film drying possibilities with small heating up to 40 oC. The drying characteristics of rhubarb cubes were studied using non-linear multiple regression analysis. Using experimental data, the two arguments non-linear equation was obtained to evaluate the drying time and sample thickness effect on rhubarb moisture. The determination coefficient of this correlation was R2 = 0.98. The results indicated that after 20 hours drying rhubarb samples with thickness 0.5 cm are dried up to 2 %, samples with 1 cm and 2 cm thickness dried up to 17 % and 25 % correspondingly. 1 cm thick rhubarb samples temperature rose from 24 oC to 33 oC during the experiment. With decreasing moisture of the product more infrared energy is used to warm the body and less for water evaporation. Keywords: drying, IR film, rhubarb. Article DOI: http://doi.org/10.15544/RD.2015.026