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S. Gendelis and A. Jakovičs

Numerical Modelling of Airflow and Temperature Distribution in a Living Room with Different Heat Exchange Conditions

Numerical mathematical modelling of the indoor thermal conditions and of the energy losses for separate rooms is an important part of the analysis of the heat-exchange balance and energy efficiency in buildings. The measurements of heat transfer coefficients for bounding structures, the air-tightness tests and thermographic diagnostics done for a building allow the influence of those factors to be predicted more correctly in developed numerical models. The temperature distribution and airflows in a typical room (along with the heat losses) were calculated for different heater locations and solar radiation (modelled as a heat source) through the window, as well as various pressure differences between the openings in opposite walls. The airflow velocities and indoor temperature, including its gradient, were also analysed as parameters of thermal comfort conditions. The results obtained show that all of the listed factors have an important influence on the formation of thermal comfort conditions and on the heat balance in a room.

Open access

S. Sakipova, A. Jakovics and S. Gendelis

Abstract

The article discusses some aspects of the use of renewable energy sources in the climatic conditions prevailing in most of the territory of Latvia, with relatively low wind speeds and a small number of sunny days a year. The paper gives a brief description of the measurement equipment and technology to determine the parameters of the outer air; the results of the measurements are also analysed. On the basis of the data obtained during the last two years at the meteorological station at the Botanical Garden of the University of Latvia, the energy potential of solar radiation and wind was estimated. The values of the possible and the actual amount of produced energy were determined.

Open access

J. Grechenkovs, A. Jakovich and S. Gendelis

3D NUMERICAL ANALYSIS OF HEAT EXCHANGE IN BUILDING STRUCTURES WITH CAVITIES

In the paper, the heat transfer inside a building block with cavities is analyzed and a brief overview of the relevant physical problem is given. The equations governing the heat exchange processes are presented and a numerical model is derived with the help of ANSYS software. The role of radiation and convection inside the cavities is emphasized throughout the work. The results show that in such cavities the radiation mechanism of heat transfer is dominant. The authors also examine the dependence of the effective heat conductivity on the properties of clay material. Using the numerical model, attempts have been made to improve the heat resistance of a building block. Possibilities of practical application of numerical modelling in the heat insulation material engineering are discussed.

Open access

A. Ozoliņš, A. Jakovičs and S. Gendelis

Abstract

The aim of the current paper is to analyse thermal comfort and overheating risks in the low-energy buildings in a summer season under Latvian climate conditions both experimentally and numerically. An interior temperature and relative humidity are analysed under free-floating conditions. Two cases are analysed: in one case, the solar influence through the window is taken into account; in the other this influence is omitted. Three different building solutions are observed: two building structures which mainly consist of the mineral wool and wooden materials and one structure from aerated clay bricks and mineral wool. The experiments have been implemented in test stands in Riga, Latvia. The numerical simulations based on measurements obtained from test stands have been performed using software WUFI Plus. The results show that the wooden constructions have high overheating risks.

Open access

S. Gendelis, A. Timuhins, A. Laizans and L. Bandeniece

Abstract

The main aim of the current paper is to create a mathematical model for dual layer shell type recuperation system, which allows reducing the heat losses from the biomass digester and water amount in the biogas without any additional mechanical or chemical components. The idea of this system is to reduce the temperature of the outflowing gas by creating two-layered counter-flow heat exchanger around the walls of biogas digester, thus increasing a thermal resistance and the gas temperature, resulting in a condensation on a colder surface. Complex mathematical model, including surface condensation, is developed for this type of biogas dehumidifier and the parameter study is carried out for a wide range of parameters. The model is reduced to 1D case to make numerical calculations faster. It is shown that latent heat of condensation is very important for the total heat balance and the condensation rate is highly dependent on insulation between layers and outside temperature. Modelling results allow finding optimal geometrical parameters for the known gas flow and predicting the condensation rate for different system setups and seasons.