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Keywords

room, model, with, consists, mathematical, components, ANSYS, calculation, temperature, content, calculated, parameters, heat, moisture, Fluent, exchange, microclimate, four, line, error, which, experimental, transfer, results, air,, Thermophysical, Russian], 2016, experiment., Basis

Transcript

Simulation of the processes of heat- and the
mass transfer in the rooms of public building
with the natural ventilation
Maria Prorokova1,*, Vyacheslav Bukhmirov1
1State Educational Institution of Higher Professional Education Ivanovo State Power University
named after V.I. Lenin, 1153003 Ivanovo, Russia
Abstract. In the article the mathematical model of the processes of heat
exchange and mass exchange in the room of building with the natural
ventilation is shown. The verification of mathematical model is performed
via the comparison of the results of calculation in ANSYS Fluent with the
data of experiment. Experiment was conducted in the room of educational
institution. In the experiment were measured the temperature of air, air
speed and moisture content in air. A low relative error in the calculation
with the use of a mathematical model makes its use for predicting the
parameters of microclimate after the introduction of the energy-saving
measures possible
1 The mathematical model of the processes of heat exchange
and mass exchange in the room
The prediction of the parameters of microclimate in the rooms of habitable, public and
office buildings is urgent task. Solution of this problem will make it possible to estimate
influence on the microclimate of the rooms of factors, connected with the energy-saving
measures [1].
For the solution of this problem in Ivanovo State Power University was used the method
of mathematical simulation. The thermal, humid and air regime of room was described by
such parameters as the temperature of air (Тв, 0С), air speed (w, m/s), moisture content (d,
kg/kgd.a.) and the concentration of carbon dioxide (СО2, ppm). For calculating these
parameters the system of differential equations, which contains the equation of the
conservation of energy, pulse and quantity of substance, and also the integral-differential
equation of the transfer of the radiant energy, was solved [2-4].
The standard k-ε model of turbulence was used for calculating the turbulent properties
of air in the room [5]. The realization of the mathematical model of the processes of heatmass transfer is executed in ANSYS Fluent [6]. The solution of the equations of the transfer
in ANSYS Fluent is based on the method of final volumes.
* Corresponding author: prorokova_mv@list.ru
DOI: 10.1051/, (2017) 7920100792 matecconf/201MATEC Web of Conferences 01007
Thermophysical Basis of Energy Technologies - 2016
© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative
Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).
2 The verification of the mathematical model
The verification of the mathematical model of microclimate in the room was executed by
the comparison of the results of calculation in ANSYS Fluent with the data of experiment.
In the experiment in the room were measured the temperature, air speed and moisture
content in air. Measurements are taken on height 0.1, 0.6 and 1.7 m from the floor (for the
rooms, in which the people the large part of the time sit) [7].
During the first stage calculation in ANSYS Fluent is built the geometric model of
experimental room (figure 1) and with the aid of the grid editor Meshing to the calculated
region it is superimposed Cartesian multilevel grid (method CutCell). The automatic
generation of adapted grid made it possible to obtain grid from 1488278 the elements and
1817190 the units with the quality of the elements average by the volume of calculated
region 0.98. The exterior view of calculated grid is represented in the figure 2.
11
2
8
7
5
4
3 8
1
12
9
6
10
Fig. 1. The geometric model of the experimental room: 1, 3, 4, 5, 8 – table; 2, 10 – the sensors, which
measure the parameters of air; 6 – the source of the heat (oil cooler); 7 – window; 8 – the source of
the heat (heat-fan); 9 – sensor for measuring the parameters of surrounding air; 11, 12 - the door.
In the calculation it is accepted:
– air in the room is of four component mixture of nitrogen (N2), of oxygen (O2), of
carbon dioxide (CO2) and of water vapour (H2O);
– air is subordinated by ideal gas law;
– air in the room is diathermy;
– air it enters evenly only on the perimeter of window.
For describing the boundary conditions of task the results of the experiment were used:
the mean temperature of the surfaces of room, the temperature of air, the moisture content
in air, air velocity and the composition of surrounding air, the temperature of the surface of
man, composition and the temperature of air, which inhales and breathes out men, power of
the source of heat (oil cooler).
DOI: 10.1051/, (2017) 7920100792 matecconf/201MATEC Web of Conferences 01007
Thermophysical Basis of Energy Technologies - 2016
2
Fig. 1. Computational grid.
With the mathematical simulation of microclimate in the experimental room the
influence of air composition on the basic parameters of microclimate was investigated.
Calculations are executed for two air compositions:
– air in the room and tributary, and breathed out by man consists of the mixture of two
gases: of nitrogen (N2) and oxygen (O2);
– air in the room is the four-component mixture, which consists of nitrogen (N2), of
oxygen (O2), of carbon dioxide (CO2) and of water vapour (H2O).
Problem is solved for steady state of heat exchange and mass exchange with the
application of the method Pseudo Transient.
The results of calculation and experiment are given in the figures 3, 4 and 5.
In the tables 1 and 2 is given an relative error in calculated temperature and moisture
content in air in ANSYS Fluent (in comparison with the experiment).
Fig. 3. The temperature of air in the room: continuous line – air consists of four components (N2, O2,
CO2 and H2O); dashed line – air consists of two components (N2 and O2); point – the experiment.
DOI: 10.1051/, (2017) 7920100792 matecconf/201MATEC Web of Conferences 01007
Thermophysical Basis of Energy Technologies - 2016
3
Fig. 4. The velocity of air in the room: continuous line – air consists of four components (N2, O2, CO2
and H2O); dashed line – air consists of two components (N2 and O2); point – the experiment.
Fig. 5. Moisture content of the air in the room: continuous line – air consists of four components (N2,
O2, CO2 and H2O); dashed line – air consists of two components (N2 and O2); point – the experiment.
Table 1. An error in the calculated temperature of air in ANSYS Fluent.
№ the
point
Height
above
floor
level, m
Тв, К
(experiment)
Air consists of two
components
Air consists of four
components
Тв, К
(calculation)
Relative
error, %
Тв, К
(calculation)
Relative
error, %
1
0.1 303.1 301.94 3.85 302.18 3.06
0.6 303.1 303.67 1.89 303.05 0.17
1.7 303.2 303.95 2.48 303.37 0.56
2
0.1 303.4 302.05 4.44 302.50 2.96
0.6 303.5 303.80 0.98 303.35 0.49
1.7 303.6 304.47 2.84 303.33 0.88
DOI: 10.1051/, (2017) 7920100792 matecconf/201MATEC Web of Conferences 01007
Thermophysical Basis of Energy Technologies - 2016
4
Table 2. An error in the calculated moisture content of the air in ANSYS Fluent.
№ the
point
Height
above
floor
level, m
d, kg/kgd.a.
(experiment)
Air consists of two
components
Air consists of four
components
d, kg/kgd.a.
(calculation)
Relative
error, %
d, kg/kgd.a.
(calculation)
Relative
error, %
1
0.1 0.0143 0.0127 11.19 0.0130 9.09
0.6 0.0143 0.0127 11.19 0.0142 0.70
1.7 0.0142 0.0127 10.56 0.0151 6.34
The analysis of figures 3, 4 and 5 and tables 1 and 2 shows that the calculation of water
vapour and carbon dioxide in air increases the accuracy of the mathematical simulation of
microclimate. A difference in the calculated and experimental values of the air speed and
moisture content is caused by both the error in the numerical calculation and by error in the
experimental determination of these parameters.
3 Conclusion
Is proposed and realized in ANSYS Fluent the mathematical model of the processes of heat
transfer and mass transfer in the room of building, which considers water vapour and
carbon dioxide in air. Is proven the authenticity of mathematical model with the aid of the
comparison of the results of calculation with the experimental data.
References
1. V.V. Bukhmirov, M.V. Prorokova, Vestnik IGEU 4 (2015) [in Russian]
2. B. Gebkhart, Y. Dzhaluriya, R. Mekhadzhan, B. Sammakiya, Svobodnokonvektivnye
techeniya, teplo- i massoobmen (Mir, Moscow, 1991) [in Russian]
3. Yu.A. Tabunshchikov, M.A. Brodach, AVOK, 2002 [in Russian]
4. A.M. Grimitlin, T.A. Datsyuk, D.M. Denisikhina, AVOK Severo-Zapad, 2013 [in
Russian]
5. I.A. Belov, S.A. Isaev, Modelirovanie turbulentnykh techeniy (Balt. gos. tekhn. un-t,
2001) [in Russian]
6. I. Weinhold, J. Parry, The Three Waves of Commercial CFD. URL: www.mentor.com
[12.07.2016]
7. GOST 30494-2011 Zdaniya zhilye i obshchestvennye. Parametry mikroklimata v
pomeshchenii (2011)
DOI: 10.1051/, (2017) 7920100792 matecconf/201MATEC Web of Conferences 01007
Thermophysical Basis of Energy Technologies - 2016
5

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