Ceiling panels radiant heating systems
M.Sc.ing. Agris Ikaunieks,Riga Technical University,M.Sc.ing. Dmitrijs Ivancovs,Riga Technical
University,M.Sc.ing Jelena Pshenichnaja, Riga Technical University,
Abstract - Radiant panel heating systems are widely used for
different kinds of building, both commercial and residential. The
aim of the publication is to identify advantages and disadvantages
of heating system technical design for industrial buildings, to
evade design deficiencies in future projects for practical use. It
was important to prove that heating systems with low
temperature of heat carrier could compensate building heat losses
and provide designed comfort temperature in transient season
(before and after heating season), when sharp changes of outdoor
temperature are typical. The topical issue of the system is based
on energy savings potential and ability of low temperature heating
systems usage with renewable energy sources, such as solar
systems and heat pumps. Radiant heating ceiling panels with low
temperature heat carrier were chosen as an object of theoretical
evaluation and experimental tests. To understand system’s
working outlines is important for us to show percentage ratio of
radiant and convection heat flow in the heated area. Proposal of
destratifacators usage for warm air of upper indoor air layers of
the heated area to heat the area additionally was described.
Keywords-Radiant panel heating systems, low temperature of
heat carrier, destratifacators, transient season of the year.
I. NOMENCLATURE
Af - total floor area in the heated space, m2
A r - available panel surface area in the heated space, m2
A u - total indoor surface area of the heated space, m2
A 1 - area-weighted average temperature of the indoor
surfaces at design conditions (excludes panel surfaces), °C
droom position index, dimensionless
D e - equivalent diameter of the heated indoor space, m
haltitude of the location above sea level, m
L f - perimeter of the heated space (measured at inside), m
Q – practical heating load of the indoor space, W
Q y - practical panel load, W
rlinearization factor for the radiation heat transfer
term, °C
t’a - indoor design temperature of a panel conditioned
space, °C
outdoor design temperature, °C
tbeffective panel surface temperature, °C
tpzadjustment factor for A1; °C
σStefan Boltzmann constant, 5.67 ·10 -8 W/m2 K4
II. ITRODUCTION
While convection heat transfer between liquid and rigid
body surface
takes place, heat transfer with thermal
conductivity occurs simultaneosly. Combined effect of thermal
conductivity and heat transfer is called heat conduction
exchange. Heat quantity transferred by convection, is contingent
on liquid or gas context motion character, its density,
temperature and viscosity, rigid body surface condition, value
of temperature drop among liquid and rigid body.
Heat output of a panel at a given surface temperature
depends upon the indoor air temperature, temperatures of the
uncontrolled indoor surfaces, air movement in the heated space
and other characteristics like surface emission. The natural
convective heat output depends also on the altitude, and the size
of the space. If these factors can be adequately coordinated, the
total heat output of the panel can be expressed in terms of the
effective panel surface temperature. When the thermal
relationship between the panel surface and the heated space is
established the required mean water temperature in the
hydraulic circuit may be calculated if the heat diffusion in the
panel is solved. [ 1,2,5]
It is assumed that the slab operates as a plate fin and loses
heat from the upper surface. The total panel heat flux is the
algebraic sum of the radiant and convective heat output fluxes
qy=qr+qc
(1)
where
qr= Ur · (tp – A1)
qc = Uc· (tp - t’a)
(2)
(3)
when there is outdoor exposure with large fenestration area,
the air temperature of the indoor air sweeping a heated floor
may approach A1.
Here, Ur and Uc are the radiation and convection heat
transfer coefficients on the panel surface, respectively:
U r = r · Ft · σ
(4)
Linearization factor r for the radiation heat transfer may be
further simplified in the practical temperature range for panel
heating:
r = [O.O105 ·( tp + A1)/2 + 0.7955] · 1O8
(15°C < (tP + A1)/2 < 30°C).
(5)
Fr is the simplified radiation interchange factor for
(6)
Ar/ Au ≤ 0.30
The convective term involves altitude (h) and room size (D,)
corrections [1]
Uc = (1 - 2.22·10-5 ·h) 2.67· (4.96/De)0.08·2.67·(tp- t’a)0.25 (7)
The room size is characterized by De:
De = 4 * Af/Lf
The area-weighted average temperature of the unheated
(uncontrolled) indoor surfaces, A1is rather difficult to predict. It
primarily depends on the area ratio of outdoor to indoor
exposure, thermal properties and dimensions of the partition and
wall elements, as well as the outdoor conditions.
An approximate expression was given for practical design
purposes: [1]
A1≈ t’a - d·z
Here d is the room position index. d is 1/2 for a room
without outdoor exposure; 1 is for a room with one outdoor
exposed side with fenestration <5% of A u or 2 for a room with
fenestration greater than 5% of A u and 3 is for a room with two
or more outdoor exposed sides. Z is a function of outdoor design
temperature, t,:
Table 1. demonstrates theoretically evaluated data for case
study.
Units
Value
Building parameters
Heating load of
Q, W
indoor space
Perimeter of heated
Lf (m)
space
Total floor area in
A f (m2 )
heated space
Total surface area in
AU (m2 )
heated space
Altitude of location
h (m)
above sea level
Total heat flux
De
70.588
[8]
Uc
(W/m2 K)
4.56
[7]
Ur
(W/m2K)
5.734
[4]
qR (W/m2)
166
[2]
qc (W/m2)
91
[3]
qy
(W/ m2)
257
[1]
III. CASE STUDY
z ≈15/(25 + tb) (tb> -20°C). (10)
Name of position
Area size
characterized value
Convection heat
transfer coefficient on
panel surface
Radiation heat
transfer coefficient on
panel surface
Radiant heat flux on
panel surface
( heat flux
Convective
on panel surface
Formula
The experimental polygon is one of industrial buildings,
where production of building construction prefabricated
components modules are planned to be done, for production
process heavy machinery transport is necessary. The building is
meant for a warehouse and production areas. This plant is
situated west part of Latvia territory, in Tukums.
500 000
340
6 000
8 720
40
Heating systems parameters
Single panel surface
Ap (m2)
108.00
Heating panel load
Panel surface area in
heated space
Indoor design
temperature of heated
space
Outdoor design
temperature
Effective panel
surface temperature
Qy
534.19
(W/m2)
2
AR (m )
t´a °C
15
tb (°C)
-20
tp (°C)
35
d
σ
Emissitivy
(W/m2K4)
Evaluated values
Function of outdoor
z (°C)
design temperature
Average temperature
AUST
of unheated indoor
(°C)
surfaces
Linearization factor
for radiation heat r (°C3)
transfer:
Simplified radiation
Fr
interchange factor
Room position index
Fig.1 Experimental polygon
936.0
According to the technical design radiant heating panels
were installed to compensate heat losses of the plant and heat
amount required by ventilation system for afterheating of supply
air. Heat carrier inlet temperature parameters were defined as
40-550C. This type of radiant panel is used for heating as there
is topside insulation on the panel. Partial sensible load of a
panel can be controlled by the supply water temperature. Panels
are situated in different zones that could provide convenient
regulation if indoor air temperature. Radiant ceiling panel
surface exchange heat with room air by convection and other
room surfaces through radiation.
3
0.0000000567
3.0
[10 ]
6.0
[9]
101 131 002
[5]
1.000
[6]
Fig.2 Panels in the experimental polygon
Radiant ceiling panels are made from 0.5 mm-thick sheet
steel with clip profiling. Each one accommodates four precision
steel tubes and the top-surface insulation. Folded side flanges
and galvanised box-section crossbars stiffen the steel sheeting,
and provide mounting for suspension. The outside surface is
polyester coated and the inside surface is coated with a
protecting lacquer to avoid corrosion. The system operates at
heat carrier temperatures with input of 40-55°C and output of
30-40C°. The 32 mm diameter tubular heaters are furnished
with a 1” externally threaded connection boss, blank cover and
an oppositely located 1/2“ sleeve as vent/drain. [4;6]
All the values of for theoretical evaluations such as heat
losses of the building, heat carrier supply temperature and as
also constructive parameters are shown in table 1. The
characteristic values and correspondent coefficients of the
experimental polygon are shown, based on formulas mentioned
in the theoretical part of the case study the evaluation has been
made and results are presented in the table below.
Pictures shown on fig.3 allow getting inside surfaces
temperature data of the building to estimate calculations.Gained
results can serve as material that will assess availiable variety of
heat energy consumption decrease in terms of heat carrier in
transmission from heat channel to room where temperature is
controlled.
While estimating it was important to find values
influenced on the radiant and convective heat flux the mostly.
Difference between effective panel surface temperature
and indoor design temperature of a heated space mostly effects
on the convective heat flux. Percentage ratio of the convective
heat flux is in range from 58.91% to 63.63% with heat carrier
supply temperature range from 37 to 55 °C. The blue graph
curve on the Fig.6 presents the range of percentage for
convective heat flux part in the whole heat flow.
Average temperature of the unheated indoor surfaces
influence on linearization factor for the radiation heat transfer,
which in combination with simplified radiation interchange
factor influence on the radiant heat flux. Percentage ratio of the
radiant heat flux is in range from 36.37 to 41.09% with heat
carrier supply temperature range from 37 to 55 °C. The higher
the difference is the higher the percentage is. The green graph
curve on the Fig.4 presents the range of percentage for radiant
heat flux part in the whole heat flow.
Fig.4 Range of percentage for radiant and convective heat flux
Fig. 3 Experimental polygon photo and thermo camera pictures
In practice radiant and convective heat fluxes have not
been measured in details, but smoke tests have been performed
by smoke generator. It was important to visualize air movement
scheme in the experimental polygon. On the base of theoretical
evaluation it was determined that percentage of convective heat
is in the range from 58.91% to 63.63%. As it can be seen on
Fig.5 warm air mass, formed by convective heat has been raised
and concentrated under the roof construction in the upper part of
the area. Lightened roofing farms allow air to spread across all
the building, not concentrating in one separate section of
roofing. Cooler air transfers to the lower part of the building
influenced by cold surfaces of the buildings, natural air
movement takes place. But the “warm air pillow” effect still
negatively influences on heat balance of the building. If there is
a necessity to use warm air concentrated under the roof
construction for work zone destratificators are proposed to be
used.
completely. As mentioned period of the year is about 30% of all
heating season, economical effect could be impressive.
CONCLUSIONS:
Fig. 5 Experimental polygon photo and thermo camera pictures
To improve the situation destratificators are proposed to be
used. These devices are designated for destratification of the air
for industrial areas with high ceiling height to lower useless
consumption of heat. Blasting grid is design allow to change air
deflation angle in dependence on installation height and
required comfort level. Destratificator design is aimed achieving
maximal effectively of the system, by aspirating air from areas
under the roof and direct it to the work zone.
Measurement instrument was installed in the industrial
plant for period of a week. Black ball thermometer measured
radiant temperature, while the installed thermometer was put to
measure indoor air temperatures (channel one and two) and
relative air humidity. Fig. 6 demonstrates values that give
common view on the heating balance (relative humidity – right
Y ax, temperature values – left Y ax) of the building and
outdoor air temperature changes during one day.
In conclusion it must be mentioned that having
experimental data, we managed to estimate theoretically radiant
and convective percentage ratio. The temperature difference
between the heating panel surface temperature and the
temperature of the building envelope is the main value
influencing on the range of percentage for radiant heat flux.
Percentage ratio of the radiant heat flux is in range from 36.37
to 41.09% with heat carrier supply temperature range from 37 to
55 °C. The temperature difference between the building
envelope and indoor air temperature is the main value
influencing on the range of percentage for convective heat flux.
Similarly to the above mentioned the more the difference is the
more the percentage is. Percentage ratio of the convective heat
flux is in range from 58.91% to 63.63% with heat carrier supply
temperature range from 37 to 55 °C.
Smoke tests showed “warm air pillow” effect spreading
across all the building due to lightened roofing farms,
destratificators are proposed to be used to improve the situation.
Having analyzing heating system’s operation in weather
conditions with sharp changes of outdoor air, assess
effectiveness must be mentioned. Taking into the account that
sharp changes of outdoor temperature are typical of transient
season, economical effect of low temperature heating system’s
usage could be impressive. The positive effect is possibility of
using natural resources as an energy source, as for example
ground heat pump could provide required temperature for heat
carrier inlet without additional heat up.
REFERENCES:
Fig.6 Measured values for one day
The graph indicates that during only one day the outdoor
air temperature ranged from -13°C to 0°C and heating system
with heat carrier temperature 45°C successfully managed to
provide indoor air designed temperature. These conditions allow
using heating source economically, which provides a positive
effect.
Temperature 2. curve on the fig. 8 increases during period
of time from 9:00 to 11:00, which is explained by sunshine
activity, fenestration location facilitated to this effect.
Fig. 6 curve demonstrates outdoor air changes during this
period of time, sharp changes of outdoor temperature are typical
of transient season. In Latvia in March and October, as well as
partly in April, September and November traditional heating
system with high heat carrier inlet temperature mostly does not
work on a full capacity, it is switched on and off periodically,
which is not effective, as system is heated and cooled down
[1] Kilkis I.B, Sager S.S, Uludag M, A simplified model for
radiant heating and cooling panels, Elsevier Simulation Practice
and Theory 2 (1994) p. 61-76
[2] ASHRAE Handbook, Fundamentals, Chapter 6: Panel
Heating and Cooling Atlanta .
[3] Missenard A.F, Radiant Heating (Le Chauffage et le
rafraichissement par rayonnement, Editions Eyrolles 1959
Trans.1961.) P.130-145
[4] Sabiana Invironmental Comfort, HeatingDuck Strip Radiant
PanelPLANNING AND CALCULATION MANUAL., 2005. p.
25-32
[5] Fokin K.F, Building heating physics of building construction
elements (К. Ф. Фокин Строительная теплотехника
ограждающих частей зданий /М.:АВОК-ПРЕСС,– 256 с
(2006)) . С.103-109
[6] Borodinecs A., Gaujena B. Improving energy performance
of buildings using the controlled buildings
envelopes//Proceedings of 30th AIVEC Conference “Trends in
High Performance Buildings and the role of Ventilation” and 4th
International Symposium on Building and Ductwork Air
tightness (BUILDAIR), Berlin, Germany, 1 – 2 October, 2009.
– 1 – 6 p.
Jeļena Pšeņičnaja, Dmitrijs Ivancovs, Agris Ikaunieks
Starošanas apkures paneli ar zemas temperatūras situma nesēju var būt pielietoti ka komerciālo tā
arī publiskā sektora ēkām. Raksta pamatdoma bija paradīt doto sistēmu priekšrocības un trūkumus,
materiāla sagatavošanai praktiskai pielietošanai nākotnē.
Eksperimentālā poligonā tika veikti ārējas un iekšējas temperatūras, kā arī relatīva mitruma
mērījumi. Mērījumu rezultātā tika veikts teorētiskais aprēķins, kas nosāka konvektīva un starojumā
situma procentuālo daļu kopā izstarotā siltumā. Starpība starp paneļa efektīvo temperatūru un telpas
iekšēja gaisa temperatūru galvenokārt ietekmē uz konvektīvo plūsmu. Konvektīvas plūsmas procentuālais
skaitlis atrodas robežas starp 58.91% un 63,63% pie siltuma nesēja temperatūras robežas no 37 līdz 55°C.
Vidēja virsmu temperatūra ietekmē uz starošanas siltuma plūsmu. Starošanas plūsmas procentuālais
skaitlis atrodas robežas starp 36.37% un 41,09% pie siltuma nesēja temperatūras robežas no 37 līdz 55°C.
Konvektīvas plūsmas vizuāla kustība tika paradīta ar dūmu ģeneratora iekārtu. Lai paaugstinātu
konvektīvas plūsmas lietderīgu izmantošanu ir piedāvāts izmantot destratifikatorus, kas ļauj izmantot
siltumu, kas nelietderīgi krājas zem jumta konstrukcijas un bez pielietojuma. Destratifikatora iekārta ļauj
virzīt siltu gaisu ar nepieciešamo spēku un virzienu, darba zonās, ja tur ir nepieciešams uzsildījums.
Kā arī veikto mērījumu pamatā var secināt, ka neskatoties uz straujām ārēja gaisa izmaiņām (no 13°C līdz 0°C) siltuma nesējs ar turpgaitas temperatūru 45°C spēja nodrošināt projekta paredzēto iekšēja
gaisa temperatūru. Tas liecina par darbības principa lietderību gādā parejas sezonās, pirms un pēc pilnas
jaudas apkures sezona laikiem.
Елена Пшеничная, Дмитрий Иванцов, Агрис Икауниекс
Отопительные панели лучистого отопления с теплоносителем низкой температурой могут
быть применены как для зданий коммерческого, так и для частного сектора. Основная цель
публикации показать преимущества и недостатки системы, для практического применения в
будущем.
На эспериментальном полигоне были произведены замеры температуры наружного и
внутреннего воздуха, а также измерения относительной влажности. На основании измерений был
сделан теоретический расчёт, где процентуально были определены части теплового и
конвекционного излучения. Разница между эффективной температурой панели и температурой
внутренного воздуха помещения в большей степени влияет на конвективный поток. Процентное
содержание конвективного тепла находится в пределах от 58.91% до 63,63% при температуре
теплоносителя от 37 до 55°C. Средняя температуры поверхности влияет на долю лучистого
тепла. Процентное содержание лучистого тепла находится в пределах от 36,37% до 41,09% при
температуре теплоносителя от 37 до 55°C.
Визуальное движение конвективного потока было показано при помощи дымогенератора.
Для повышения полезного использования конвективных потоков, предложено использовать
дестратификаторы, которые позволяют использовать тепло, скапливающееся под каркасом крыши.
Дестратификатор позволяет направлять в рабочие зоны тёплый воздух в той силой и с тем
направлением, с каким необходимо.
На основании снятых измерений можно сделать вывод о том, что не смотря на резкие
перепады температур наружного воздуха (от -13°C до 0°C) теплоноситель с температурой подачи
45°C смог обеспечить тепмературу внутреннего воздуха, предполагаемую в проекте. Это
свидетельствует о полезности данного принципа работы системы для переходного времени года,
перед и после отопительных сезонов полной мощности.