Indoor thermal comfort by controlling heat transfer through building envelope€¦ · ·...

Indoor thermal comfort by controlling heat transfer

through building envelope

DANIEL POPESCU1 and CALIN CIUFUDEAN

2

1Electrical Engineering Department

Technical University of Civil Engineering Bucharest

Bd. Pache Protopopescu nr.66, 021414 Bucuresti Sector 2

ROMANIA

[email protected]

2Computers and Control Systems Department

“Stefan cel Mare” University of Suceava

Str. Universitatii nr.9, 720225 Suceava

ROMANIA

[email protected]

Abstract: The assurance of thermal comfort in buildings with heating / cooling installations distributed on the

surface is the best common solution.

This article proposes a new approach for analyzing the heat transfer through building envelope. Our approach

consists in a distributed area of electro-thermal pumps over the building envelope capable to create antagonist

thermal fluxes to those that appear naturally. In this way we can easily control the inside temperature by

balancing the dynamic of heat transfer. The electro-thermal pump works by relying on the Peltier–Seebeck

effect. The thermal flux direction is given by the electric current direction.

Building envelope equipped with electro-thermal pumps is the process who must to be controlled automatically

by temperature control system dedicated.

The goal of this new concept is to optimize the thermal comfort, eliminate the moisture condense on the walls

and reducing the energy consumption by controlling the building’s envelope temperature.

Key-Words: thermal comfort, heat transfer, building envelope, HVAC (heating, ventilation, and air

conditioning), automatic control of heating systems of buildings, thermoelectric systems, electro-thermal pump.

1 Thermal comfort in buildings

with heating / cooling

installations distributed on the

surface 1.1 Temperature profiles and distributed

heat sources in buildings Energy saving for heating/cooling buildings

requires a fair thermal insulation of the buildings.

On the other side there is a maximum optimal size

of the thermal insulation.

Inner thermal sources balance heat loss and keep up

to the required comfort parameters. These sources

are concentrated in certain areas (heating radiators,

fan coil), therefore the comfort parameters may

vary in different places under discontinuous

functioning regimes. Therefore, distributed heat

sources made in floor, ceiling or walls are

increasingly used [1, 10].

16° 20° 24° 16° 20° 24° 16° 20° 24° 16° 20° 24°

1,80 m

0,10 m

Ideal

heating

Underfloor

heating

Radiator

outer wall

Radiator

inner wall

Fig.1 The „temperature profile“from floor

to ceiling

Latest Advances in Information Science, Circuits and Systems

ISBN: 978-1-61804-099-2 150

Figure 1 shows „temperature profile“ from floor to

ceiling for ideal heating system, with „temperature

profiles“ for under floor heating and wall mounted

radiators [2, 3]. Note that the floor heating system

ensures the best thermal comfort in building.

Figure 2 shows how to make the system of

heating / cooling floor [2].

Fig. 2 Under floor heating in a room

Desire to improve indoor thermal comfort in

buildings led in some cases to achieve the system

as wall heating / cooling (Fig.3). Under floor

heating elements are suitable for wall

heating/cooling systems.

Fig. 3 Wall heating system

1.2 The thermal insulation of surface for

heating / cooling Thermal insulation of floors used as surface

heating/cooling must accomplish certain

requirements, depending on the location in the

building floor (below room temperature) [2]:

a) surface heating above a heated room

(≈200C);

b) surface heating above a room

heated in irregular intervals (≈150C);

c) surface heating above a cellar (unheated

basement) (≈80C);

d) surface heating in direct contact

with outside air or ground;

Figure 4 shows how to make the thermal insulation

for heating / cooling systems, the first two cases

[2]:

a) Surface heating above a heated room (Fig.3,a)

- Insulation layer 35mm

- Thermal resistivity R ≥ 0,75 (m² K) / W

b) Surface heating above a room

heated in irregular intervals (Fig.3.b)

- Insulation layer 35 mm

- Additional insulation layer 20 mm

- Thermal resistivity R ≥ 1,25 (m² K) / W

+ 20 °C

+ 20 °C

hE

hD

hB

+ 20 °C

+ 15 °C

hBhE

hD

hZ

Fig. 4 Under floor heating - thermal insulation

a) hB = Floor covering hE = Screed

hD = Insulation layer

b) hB = Floor covering hE = Screed

hD = Insulation layer hZ = Additional

insulation


ISBN: 978-1-61804-099-2 151

Heating or cooling surfaces made in floor, ceiling

or walls can contribute to heat transfer through

building envelope.

2 Improving temperature control

systems performance for heating

under floor Under floor heating system is designed to ensure

room temperature of 200C if the temperature of

thermal agent in the flow pipe is 26 ÷ 270C.

The occurrence of additional heat input into the

building (eg the sun) will lead to overcoming the

room temperature of 200C and, therefore, the room

thermostat will stop the under floor heating for a

while (Fig.5). According to the classical method of

control, the under floor heating circuit is closed and

the flow of thermal agent is zero (Fig.6). Room

temperature will drop to a value of 200C and the

under floor heating must start now.

Total absence of heat flow (thermal agent with flow

zero) has cooled too much the floor and the time

response to turn on the under floor heating is too

large. The overshoot may be unacceptable and floor

temperature may be too high during certain periods

of time; human health may be affected, increase

comfort and decrease energy consumption of

building heat.

30 % outside heat

T = 21 °C > Tset

Heat flow from the

floor surface = 0 %

Heating circuit

closed

Operation with secondary heat source

- no flow rate in the heating circuit

- floor surface is cooling down

Fig. 5. Regulation of the under floor heating

by using the room temperature control

Fig. 6 Under floor heating with room thermostat

Current requirements increase thermal comfort in

buildings, along with requirements to reduce

energy consumption for heating led to the use of an

automatic control method for under floor heating

system, where the residual flow heat in the under

floor heating circuit remains constantly [2 ,4] when

the system is stopped (Fig.7, 8).

30 % outside heat

T = 21 °C > Tset

Heat flow from the

floor

surface = 70 %

Heating circuit

open

Operation with secondary heat source

- Thermostatic valve closed

- Bypass open

Fig. 7 Regulation of the under floor heating

by using the preset table bypass

The preset table bypass provides a

constant residual flow in the circuit and

therefore a minimum floor temperature. It reduces

the time for heating up by

1 ½ h [2].

Thermostat

Preset

table

bypass

Under floor

temperature

Volume

flow

Heating circuit closed

200C

300C

Time

Temperature [0C]

Volume flow [m3/h]


ISBN: 978-1-61804-099-2 152

Fig. 8 Under floor heating with preset table bypass

The preset table bypass prevents the floor from

cooling down too much, in case of the thermostat

isolating the heating circuit due to a secondary heat

source [2].

3 Electro-thermal pump distributed

on the surface Thermoelectric materials may have an important

role for a global sustainable energy solution.

The electro-thermal pump (Fig. 9) works by relying

on the Peltier–Seebeck effect: on an electrified

serial junction of two different metals (e.g. metals

with different electron charges) we obtain different

temperatures, respectively on obtain heat flow.

The electro-thermal pump distributed on the

surface as is composed of semiconductors plates

applied on the inner surfaces of the walls has no

kinetics elements and also occupies little spaces.

The heat transfer through the building’s envelope

depends on the electric current intensity delivered

by the thermal elements and is controlled by a

computerized control unit.

The electro-thermal pump is reversible: the thermal

flux direction is given by the electric current

direction.

In present, a lot of projects were selected to

accelerate the development of thermoelectric

systems that provides the heating, ventilation, and

air conditioning (HVAC) for automotive industry.

The use of solid state thermoelectric devices to heat

and cool a vehicle’s passenger compartment can

increase vehicle efficiency by reducing engine load,

by reducing or eliminating the need for

conventional air conditioning refrigerants, these

vehicles further reduce greenhouse gas emissions.

Thermoelectric HVAC enables the use of

distributed cooling/heating units that cool/heat the

occupants rather than the whole cabin and its

components [10].

Fig. 9 Electro-thermal pump

While applicable to all commercial and passenger

vehicles, thermoelectric HVAC is particularly

attractive for hybrids and plug-in hybrids where an

electrically driven air conditioning system can

maintain occupant comfort even when the engine

turns off.

Research direction is to develop a system

thermoelectric HVAC that provides thermal

comfort equivalent to current HVAC systems while

using significantly less energy. The thermoelectric

system components will be integrated into a

demonstration vehicle for testing and evaluation.

4 Automatic control of heat transfer

through building envelope Indoor thermal comfort and energy consumption of

buildings depends on the heat transfer by building

envelope [5].

Volume

flow

Under floor

temperature Heating circuit

partially closed 200C

300C

Time

Temperature [0C]

Volume flow [m3/h]

30% residual flow


ISBN: 978-1-61804-099-2 153

4.1 Infrared thermograph method of

building envelope Between the period 2007 – 2008 at the Technical

University of Civil Engineering Bucharest was

developed a research grant concerning the

automatic control of heating systems of buildings

by measuring the heat transfer through outside

bulding surfaces.

As a result of the research work for this grant there

have been designed and implemented an automat

control system that measures the heat transfer

through the building walls [6, 7. 8]; so that one may

thermo graphically measure the temperature of the

exterior walls and by converting from analog to

numeric the measured values one may control the

thermal confort through a computerized system

which control the debit of thermal agent inside the

bulding.

Automatic control basically consists on regulating

the flow of the thermal agent as a function of heat

loss through the exterior walls of the building. In

order to have an accurate control one may have to

supervise the temperature fluctuation at the surface

of the exterior walls. This process involves

experimentally charting the temperature of the

exterior walls and memorizing it into the

computerized control systems, such that any

changes in temperature distribution through the

walls surface is sesized by the control system

which will act on the thermal agent debit

accordingly [8].

4.2 Automatic control of heat transfer

through building envelope with electro-

thermal pump distributed on the surface This article proposes a different approach for

thermal transfer through buildings envelopes [9],

namely by surface distributed electro-thermal

pumps which control heat transfer through

envelope.

The above-mentioned approach is possible by

heating thermal flows opposite to natural flows

which will determine a controlled temperature

balance of the building’s inner walls.

This new approach will ensure the thermal comfort

as an alternative to the conventional heating

methods of buildings.

The solution is based on achieving an electro

pumps distributed on the surface, which controls

the heat transfer through the building’s envelope.

This new approach will ensure the thermal comfort

as an alternative to the conventional heating

methods of buildings eliminate condensation in

walls and reducing energy consumption in

buildings through building envelope temperature

control. It acts directly on the building envelope

that is the part of the building which loses heat to

the outside.

The thermoelectric elements are placed on different

types of materials constituting the walls of

buildings in order to obtain a homogeneous

temperature distribution. For walls equipped with

thermoelectric elements heat transfer is evaluated

by thermograph method.

Among those models who we studied, we choose

those that could withstand the winter and summer

weather, i.e. heating and cooling regimes and

determine the extreme limits of operation.

The building envelope equipped with electro-

thermal pumps is the process to be controlled

automatically with a dedicated temperature control

system.

5 Conclusions The new concept proposed allows obtaining the

same temperature inside the building envelope,

regardless of the orientation of the walls, so

basically dynamics of heat transfer through the

inner walls of the building depends only on

evolution of internal sources of heat.

Thermal insulation of building envelope can be

greatly reduced.

By adjusting the building envelope temperature is

obtained a good indoor thermal comfort, is

eliminated the condensation in walls and energy

consumption in building is reducing.

Control of heat transfer through building envelope

by using electro-thermal pumps distributed on the

surface can replace total or partial traditional

heating / cooling systems, remain to be used only

fresh air-conditioning systems that ensures indoor

air quality.

References:

[1] Atmaca, I., Kaynakli, O., Yigit, A., Effects of

radiant temperature on thermal comfort,

Building and Environment, Volume 42, Issue 9,

September 2007, pp. 3210–3220

[2] http://www.oventrop.de, Surface heating and

cooling

[3] Mira, N., Enciclopedia tehnică de instalaţii

Volume E, ARTECNO Bucureşti Publishing

House, 2010, ISBN 978-973-85936-5-7.

[4] Peters, R; Zerwas, M; Krempen, T; Krause, HJ,

Optimisation of thermal comfort in existing


ISBN: 978-1-61804-099-2 154

buildings, BAUPHYSIK, ISSN 0171-5445,

10/2010, Volume 32, Issue 5, pp. 303 – 307.

[5] Wang, SW and Ma, ZJ, Supervisory and

optimal control of building HVAC systems,

HVAC&R RESEARCH, ISSN 1078-9669,

01/2008, Volume 14, Issue 1, pp. 3 – 32.

[6] Popescu, D., A New Solution for Automatic

Control of Heating Systems in Buildings Based

on Measuring Heat Transfer Through Outer

Surfaces, Proceedings of the 10th WSEAS

International Conference on Automatic

Control, Modeling and Simulation

(ACMOS'08), pp. 206-209, Istanbul, Turkey,

May 27-30, 2008.

[7] Popescu, D., Ciufudean, C., Automatic Control

System for Heating Systems in Buildings

Based on Measuring the Heat Exchange

through Outer Surfaces, Proceedings of the 8th

WSEAS International Conference on

Simulation, Modelling and Optimization

(SMO'08), pp. 117-121, Santander, Cantabria,

Spain, September 23-25, 2008

[8] Popescu, D., Ciufudean, C., Ionescu, D.,

Experimental Analysis of the Automated

System for Heating Control based on Heat

Losses through Building’s Envelope. 9th

WSEAS International Conference on

Simulation, Modelling and Optimization

(SMO'09), pp. 160 – 166, Budapest Tech

University, Budapest, Hungary, September 3-5,

2009.

[9] Spiro N Pollalis, Energy and the Building

Envelope, Buildings, ISSN 0007-3725,

12/2005, Volume 99, Issue 12, p. 14.

[10] Nilsson, Hakan O., Local evaluation of

thermal comfort, International Journal of

Vehicle Design, Volume 42, Issue 1-2, 2006,

pp. 8-21.


ISBN: 978-1-61804-099-2 155

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