Ensuring the Comfort in the Heated Space by Controlling the

Temperature in the Heating Installation of a Non-residential Building

Daniel Popescu

and Ioan Borza

Department of Electrical Engineering in Civil Engineering and Building Services,

Technical University of Civil Engineering Bucarest, Bucarest, Romania

Department of Civil Engineering and Building Services, Politehnica University of Timisoara, Timisoara, Romania

Keywords: Temperature Control, Nonlinear Control Systems, Modelling, Simulation, Building Automation,

Civil Engineering.

Abstract: In this article is modeled, with the help of Simulink, the automatic system that controls the thermal agent

temperature in a non-residential building chosen for study. It describes how the model has been drawn for the

subsystem entitled HEATED SPACE in the building. There were used mathematical relationships which show

how the indoor temperature is changing, depending on the heat input in building and the heat loss through

building envelope. The other subsystems have been modeled in the articles specified in the bibliography. By

simulation of the model for the automatic system is determinated his behavior during two days in the winter

season. The evaluation of the thermal comfort in the heated space from the building, ensured by using the

automatic system, is made by analyzing the graphs of the significant temperatures from the modeled system:

indoor temperature, outdoor temperature and thermal agent temperature in the heating installation. At the end

of the article are shown the main causes of low thermal comfort in the building, and also the reasons why this

type of automatic system is preferred in many non-residential buildings.

1 INTRODUCTION

The comfort is defined in the Oxford Dictionaries as

being „a state of physical ease and freedom from pain

or constraint”. The comfort can be of several types:

thermal comfort, visual comfort, acoustic comfort,

olfactory comfort.

The quality of the built space in a building depends,

among others, on the thermal comfort in building

(Clements-Croome, 2011; Oancea and Caluianu, 2012;

Frontczak et al., 2012). It can be evaluated using the

indoor temperature perceived by the occupants of the

building. This temperature can be maintained at the

desired constant value only if is kept the balance

between the input heat into the building and the lost

heat through the building envelope.

The thermal comfort in building can be ensured

only by using adequate automatic control systems for

the heating installations.

In the case of automated systems commonly used

in non-residential buildings there is no setpoint for the

indoor temperature, because the indoor temperature is

not controlled with an own control loop. It is used

only the setpoint for flow temperature of the heating

installation. This setpoint value can be established

using the heating curve by selecting the gradient of

circuit with valve, in correlation with the destination

and the constructive characteristics of the heated

building (Mira, 2010; Ilina, 2010).

The current systems used to automate heating

installations in buildings are provided with various

functions that improve the thermal comfort, save

energy and protect the building against frost during

periods when the building is unoccupied (Diematic,

2015). These functions are:

 adapting the time response of the systems to the

building inertia factor;

 time programming of the heating installation in

comfort period and reduced period;

 choosing the room temperature that activates the

antifreeze function;

 choosing the outside temperature required for

heating shut-off.

2 OBJECTIVES OF THE

ARTICLE

The objectives are the following:

462

Popescu, D. and Borza, I.

Ensuring the Comfort in the Heated Space by Controlling the Temperature in the Heating Installation of a Non-residential Building.

In Proceedings of the 5th International Conference on Smart Cities and Green ICT Systems (SMARTGREENS 2016), pages 462-467

ISBN: 978-989-758-184-7

- modeling the automatic heating system of the

non-residential building so that the model to represent

with accuracy the physical characteristics of the real

system;

- simulation of the functioning for the modeled

automatic system and recording the evolution of the

representative temperatures from the system.

- evaluation of the automatic system model by

analyzing the records over time for the indoor

temperature, flow and return temperatures in the

heating installation, depending on the outdoor

temperature changes.

3 PROCEDURE FOR

MODELING, SIMULATION

AND EVALUATION OF THE

AUTOMATIC SYSTEM

The automatic heating system is decomposed into

subsystems and then is modeled each subsystem. The

subsystems represent the used automation

equipments, the heating installation of the building,

the thermodynamic system of heated space and the

exterior environment of the building. There are

created block diagrams in Simulink for each

subsystem, based on mathematical equations, transfer

functions or graphs according to which the

subsystems work.

The evaluation of the model for the automatic

system is done by simulation and recording of the

evolution for representative parameters. The model

will be declared valid if he represents with accurately

the physical characteristics of the analyzed automatic

system.

4 AUTOMATIC SYSTEM FOR

TEMPERATURE CONTROL OF

THE THERMAL AGENT IN

NON-RESIDENTIAL

BUILDINGS

The classical control loop with three-points regulator

and three-way control valve is completed with

HEATING CURVE subsystem. This subsystem is

dedicated for automation of heating installations in

buildings, because it determines the set point for the

thermal agent temperature according to the outside

temperature. The set point value must take into

account the construction features of the building and

also its destination. In the current practice of the

automated heating installations for non-residential

buildings, the HEATING CURVE subsystem is

included in the automatic regulator.

Outside temperature evolution is modeled using

the OUTDOOR TEMPERATURE subsystem.

The heating of the indoor space delimitated in the

space of the Faculty of Building Services Engineering

Bucharest is performed by means of a heating circuit

independent from the other circuits which makes up

the heating installation of the whole building

(Popescu et al., 2008; Popescu and Ciufudean, 2008).

The block diagram of the automatic system is

shown in Figure 1.

In the analyzed non-residential building, the

heating installation is provided with radiators and the

thermal agent is water. The boiler is the heat source

that operates at a constant temperature of 800C.

The effect of the temperature control in the

heating installation must be to maintain the indoor

temperature in the heated space to a value as constant

as possible.

The models for the subsystems OUTDOOR

TEMPERATURE, HEATING CURVE,

NONLINEAR CONTROLLER, THREE-WAY

MIXING VALVE and HEATING SYSTEM were

made in Simulink (Popescu et al., 2009).

5 MODEL OF THE HEATED

SPACE FROM BUILDING

The heated space in the building is intended for

offices. The constructive characteristics of the heated

space are:

- walls without insulation applied to the outside;

- walls made of bricks;

- building with three levels (ground floor and two

floors);

- dimensions 20m x 10m x 10m.

The heat input

Q into the heated space by means

of the installation is

Tcq

agag

Δ⋅⋅=

(1)

where

indoor

retflow

T −

=Δ

(2)

- volumetric flow of the thermal agent in the

installation

- specific heat of the thermal agent

Ensuring the Comfort in the Heated Space by Controlling the Temperature in the Heating Installation of a Non-residential Building

463

Figure 1: Block diagram of the automatic system modeled.

Figure 2: Simulink model for HEATED SPACE subsystem.

flow

- flow temperature

ret

T - return temperature

indoor

T - indoor temperature

The temperature difference between flow and

return of the heating installation, can be calculated

with the relation

indoorret

indoorflow

retflow

−

=Δ

(3)

which shows the connection between the indoor

temperature in the building and the water temperature

in the heating installation.

The heat losses through the building envelope that

correspond to the heated space, is calculated with the

relation

)(

outdoorindoor

mPE

out

Rdt

−⋅= .

(4)

mPE

- average thermal resistance of the building

envelope

outdoor

- outdoor temperature

It is used the following simplifying hypothesis:

heat losses are only through the exterior wall, that has

the surface 20m x 10m = 200m

The equation which models the heated space in

the building is

airair

outinindoor

cmdt

⋅

⎟

⎠

⎞

⎜

⎝

⎛

−=

(5)

air

- mass of air in the heated space

air

- specific heat of the air

The numerical values that need to be introduced

in the equation of the heated space model are

established further.

Mass of the air from the heated space

kgmmm

airairair

2450101020225,1

=⋅⋅⋅=

=⋅=

MoMa-GreenSys 2016 - Special Session on Modelling Practical Paradigms of Green Manufacturing Systems

464

Figure 3: Results of simulation for the model of the automatic system.

The pump chosen for the circulation of the

thermal agent in heating installation has the

volumetric flow

694,0694,05,2

===

Specific heat of the air

Kkg

air

⋅

= 4,1005

Specific heat for thermal agent (water)

Kkg

⋅

= 4190

Average thermal resistance of the building

envelope (exterior wall) has been chosen

mPE

⋅

3,0

. A building envelope whose

average thermal resistance is 0,3 ... 0,5

⎥

⎦

⎤

⎢

⎣

⎡

⋅

corresponds to uninsulated buildings. The reference

buildings are characterized by thermal resistance with

values of 0,6...0,7

⎥

⎦

⎤

⎢

⎣

⎡

⋅

and the energy efficient

buildings are characterized by thermal resistance

values of

1...1,2

⎥

⎦

⎤

⎢

⎣

⎡

⋅

The thermal resistance of the exterior wall with

surface S is

mPE

mPES

0015,0

1020

3,0

⋅

and

mPES

670

0015,0

≈=

The Simulink model for the subsystem called

heated space from the building is shown in Figure 2.

The heated space model allows recording the

indoor temperature, the main parameter which

evaluates the thermal comfort in the built space.

6 SIMULATION AND

EVALUATION OF THE MODEL

The model of the automatic system shown in Figure

1 represents the current situation in the building

Ensuring the Comfort in the Heated Space by Controlling the Temperature in the Heating Installation of a Non-residential Building

465

which belongs to the Faculty of Building Services

Engineering Bucharest.

The simulation of the model for the automatic

system is performed in a time interval that lasts

180,000 seconds, that is to say 50 hours. Time

interval for simulation was chosen large enough

compared with the values for the time constants of the

processes of heating in buildings and with the

transitory regime for an automatic heating system.

Through simulation were recorded the evolutions

for the temperatures from the heating system, indoor

temperature and outdoor temperature. The graphs are

shown in Figure 3 and represent the behavior of the

automatic system in winter days with normal

temperatures for Romania.

After passing the transitory time, caused by the

putting into service of automatic heating system, it is

found the correct correlation between flow

temperature from the heating installation

][KT

and

outside temperature

][KT

, according to equation

KKTKT

otft

87,732][5,1][ +⋅−=

(6)

This equation has been used for modeling the

subsystem HEATIG CURVE.

7 CONCLUSIONS

The model can be validated because, according to the

results of the simulation, it accurately represents the

actual physical characteristics of the automatic

system analyzed.

The variations obtained for the outside

temperature and the thermal agent temperatures in the

heating installation, as well as the correlations

between them, are in accordance with the

requirements for correct operation of the heating

installation in the non-residential building. In the

conformity assessment we must take into account that

the precision of choice for the slope of the HEATING

CURVE depends on the degree of knowledge of the

characteristics of the building.

A poor result was obtained for indoor air

temperature of the heated space. There are noted

maximum temperature variations

CCC

indoor

000

6,22,188,20 =−=Δ

, which can be

felt as a discomfort by the building occupants.

The low thermal comfort arises because the

indoor temperature does not have an own control

loop. The indoor temperature in the heated space is

maintained approximately constant only by

controlling the thermal agent temperature in the

heating system depending on outside temperature. In

the temperature control of the thermal agent are

cumulated imprecisions that come from the non-

linear control, from the choice of the slope value in

HEATING CURVE and from the experimental

determination procedure of the mathematical model

for the heating installation.

The buildings and heating processes in non-

residential buildings are characterized by large and

very large thermal inertia, which is why the building

indoor temperature changes very slowly; these

variations of the indoor temperature represent a minor

thermal discomfort for the building occupants. Are

thus evident the main reasons for what the traditional

heating automation in buildings is based on the non-

linear control. An additional reason is the low price

for nonlinear automatic systems.

Local control of the indoor temperature in each

room of the building may be the ideal solution for

ensuring the thermal comfort of all building

occupants, but his high cost would allow rarely its

application.

REFERENCES

Clements-Croome, 2011. The interaction between the

physical environment and people. In: S.A. Abdul-

Wahab, ed. Sick building syndrome in public buildings

and workplaces. Berlin Heidelberg: Springer-Verlag,

239–261.

Oancea, C., Caluianu, S., 2012. Analysis of non-residential

buildings in Romania from the labour productivity and

intelligent buildings concept point of view. Intelligent

Buildings International, Volume 4, Issue 4, pages 216-

227, Publisher Taylor & Francis Ltd., ISSN 1750-8975.

Frontczak M, Schiavon S, Goins J, Arens E, Zhang H, and

Wargocki P., 2012. Quantitative relationships between

occupant satisfaction and aspects of indoor

environmental quality and building design. Indoor Air

Journal, Volume 22, Issue 2, 119-131. doi:

10.1111/j.1600-0668.2011.00745.x.

Mira, N. (coordinator), 2010. Technical Encyclopedia of

Installations, Volume E, ISBN 978-973-85936-5-7,

Publishing House Artecno Bucharest.

Ilina, M. (coordinator), 2010. Technical Encyclopedia of

Installations, Volume I, ISBN 978-973-85936-5-7,

Publishing House Artecno Bucharest, 2010.

DIEMATIC-m Delta, 2015. Control panel, Starting up and

operating Instructions, De Dietrich Thermique.

Available: http://www.dedietrich-thermique.fr.

Popescu, D., Ionescu, D., Iliescu, M., 2008. The fixed part

behavior of the heating automated systems in large

buildings, National Conference of Installations, Sinaia,

Romania, pp. 31-36, ISBN 978-973-755-406-2.

Popescu, D., Ciufudean, C., 2008. Automatic Control

System for Heating Systems in Buildings Based on

Measuring the Heat Exchange through Outer Surfaces.

MoMa-GreenSys 2016 - Special Session on Modelling Practical Paradigms of Green Manufacturing Systems

466

Proceedings of the 8th WSEAS International

Conference on Simulation, Modelling and

Optimization, pp. 117-121, ISSN 1790-2769.

Popescu, D., Ciufudean, C., Ghiauş, A., 2009. Specific

Aspects of Design of the Automated System for

Heating Control that Accounts for Heat Losses Through

the Building’s Envelope. Proceedings of the 13th

WSEAS International Conference on Systems, pp. 352

– 356, ISSN 1790-2768.

ISO 13789, 2007. Thermal performance of buildings-

Transmission and ventilation heat transfer coefficients-

Calculation method.

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