ТЕХНИЧЕСКИЕ НАУКИ/ 5.Энергетика

Barbasova T. A., Zaharova A. A.

South Ural State University, Russia

The thermal conditions modeling of the building blocks of the South Ural State University's educational complex

_{The modeling object under consideration is the blocks of the educational complex of South Ural State University. These blocks include the educational buildings 3BC and 3A. The facades of the buildings face different cardinal points, and this implies that the degree of influence of environmental disturbances, such as solar radiation and wind direction, differs for each point.}

_{As of today, during the modeling stage of thermal conditions it is customary to render building as a single object of thermal interaction with environment, that is not to single out minor premises in it, but to see it as a building in its complete arrangement, or divide building on several major elements, according to the character of existing heat exchange processes. This can be explained by the fact, that for building modeling with regard to all its premises, and, according to the existing heat exchange processes, it is necessary to have vast processing power of modeling systems. Moreover, usually the same indoor temperature is maintained in all premises of a building, and the temperature difference does not exceed 2-5 Centigrades, thus one may neglect the heat exchange rate between the rooms of residential building.}

_{The current research considers the following division of the buildings under study: Building 3A is divided according to its facades, its basements is divided separately; building 3C is divided according to its facades as well; building 3B includes lecture rooms, hall and basements.}

_{The general scheme of building heat supply is shown on figure 1.}

Set point

Domestic Heating Plant model

Heater model

Heating system heat

Indoor temperature

Heat accumulation model

Building’s heat losses

Heat loss model

Weather conditions

_{Figure 1 - Structured model scheme}

Simulink pack, which is the part of mathematical software package Matlab, has been used for designing of heat supply model of blocks, including heat load and heating system itself and the model of domestic heating plant with integrated control system as well.

General view of the design system model is shown on Figure 2. The model comprises several building blocks: Buildings, heat supply system, weather data, additional heat gains, graf (heat carrier delivery graphic of Chelyabinsk Heat Networks).

Figure 2 - General model view

Figure 3 shows the content of the block Building, which comprises model approximations of researched buildings. Buildings in this model represent the heat load for heat supply systems.

Figure 3 - Content of the block Buildings.

Inputs for building model are comprised of Additional gains, Heat supply temperature from supply system and weather data as well, which influence heat losses. On outputs from block we get heat loss value, according to the changing of weather data, indoor temperatures are calculated as well. Inner structure and equations, by means of which mathematical model is designed, are of one type for each section of researched buildings.

Each building is presented as assembly of sections it comprises. Each section has its heat loss model, according to geometric sizes of a section, system of heating equipment, which receives heat carrier from domestic heating unit, and where indoor temperature in premise is calculated. On appropriate inputs the increment of additional gains (aggregate) is carried out. The additional gains originate as consequence of presence of humans in premises, solar heat, heat gains from electrical appliances. Therefore, the influence of these factors on indoor temperature is traced.

Estimate of heat loss is carried out for all enclosing structures of section, to which windows, walls and ceilings belong. These heat losses are summarized for each section of researched building. Thus, considering infiltration and wind velocity adjustment, we get the comprehensive idea of crucial building's heat losses data.

Window openings have maximum heat loss potential because its thickness is rather small. Looseness in construction of walls and ceilings affect heat loss potential considerably.

Thermal imager snapshots indicate the heat loss value. Figure 4 shows what constructions have the highest thermal conductivity, and, thus, lose heat more intensively.

Figure 4 - Eastern facade of building 3B.

_{The modeling of thermal processes of building blocks with various geometric characteristics and geographic points has been carried out within the framework of this project. The time range equals to two full days, which is enough for demonstration of the operating conditions of heat supply system. The weather conditions are chosen for the period with mean ambient temperature of -8 Centigrade, as well as with significant degree of solar irradiation (March).}

_{These conditions of modeling indicate the efficiency of application of control algorithms on the particular heat unit. Thus, mean indoor temperature of heated premises is taken into account apart from generally accepted outdoor temperature feedback.}

_{Figure 5 - Diagrams of indoor temperature in all control sections of researched buildings.}

_{As is clear from Figure 5, control system maintains required temperature in all control sections of researched buildings. Initial temperature for all sections - 20 Centigrade above zero. The duration of heating-up of the premises to desired values is determined by various buildings characteristics and its sections.}

Therefore, within the framework of this project the model of thermal processes in buildings, which takes into account the interaction of thermal currents, has been designed. This simulation model has been used for working off the operation conditions of heat supply systems.

References

1. Potapenko, A. N. Automated control of processes of centralized heat supply of distributed building block with regard to modeling of these processes / A. N. Potapenko, A. O. Yakovlev, E. A. Potapenko, A. S. Soldatenkov. - Belgorod: BGTU Publishing House of V. G. Shuhova, 2007. - p. 13.

2. Schneider, D. A. Automated system of dispatching control of buildings heat supply on the basis of field technologies / D. A. Schneider // Vestnik SUSU Series "Computer-aided technologies, managing, radionics". – 2008. - issue 17. – p. 23-28.

3. Chistovich, S. A. Automated systems of heat supply and heating // S. A. Chistovich, V. K. Averianov, Yu. A. Tempel, S. I. Bykov. - Leningrad: Stroiizdat, 1987 - p. 248.