Progress in Exergy, Energy, and the Environment || Thermal Comfort Analysis of Novel Low Exergy Radiant Heating Cooling System and Energy Saving Potential Comparing to Conventional

Thermal Comfort Analysis of Novel Low Exergy Radiant HeatingCooling System and Energy Saving Potential Comparingto Conventional Systems

38

Aliihsan Koca, Zafer Gemici, Koray Bedir, Erhan Boke,Barıs Burak Kanbur, and Yalcın Topacoglu

Abstract

In this study characteristics of a model room with dimensions 6 m � 4 m � 3 m has been investigated using

Computational Fluid Dynamics method with regard to thermal comfort, in case of that the room is heated and cooled

by the means of radiant panels. Both general thermal comfort parameters [PMV (percentage mean vote), PPD (predicted

percentage of dissatisfied)] and local thermal comfort parameters (radiant temperature asymmetry, draught, vertical air

temperature difference, warm and cool floors) which are described by the standards ISO 7730 and ASHRAE 55 have been

taken into consideration. Radiant panels have been placed to exterior walls for heating system, and they have been put on

both exte\rior walls and ceiling for cooling system. According to the TS 2164 standards, different regions are identified

with regard to outdoor climate conditions for heating and cooling seasons in Turkey, and analysis of heating/cooling is

done for each region. Heat fluxes from radiant panels and corresponding values of room mean temperature required in

order for the conditions of thermal comfort described by the standards ISO 7730 to be met have been determined for these

regions and heating/cooling system configurations. Energy saving potential of radiant system has been evaluated for these

regions and heating/cooling mode.

Keywords

Energy saving � Thermal comfort � Low exergy � Heating � Cooling

Introduction

Energy saving and emission reduction are both affected by the energy efficiency of the built environment and the quality of

the energy carrier in relation to the required quality of the energy. Low exergy heating and cooling systems allow to use low

valued energy, which is delivered by sustainable energy sources (e.g., by using heat pumps, solar collectors, either separate

or linked to waste heat, energy storage, etc.) and improve their performances.

It is vitally important to have a clear image of the exergy balance of the human body in order to understand what the low

exergy systems for heating and cooling in buildings are. It is interesting that the thermal comfortable condition is provided

A. Koca (*) � Z. Gemici � K. Bedir � B.B. Kanbur � Y. TopacogluMir Arastirma ve Gelistirme Inc., Y.T.U. Technopark A1 Building, 34220 Istanbul, Turkey

e-mail: [email protected]; [email protected]; [email protected]; [email protected];

[email protected]

E. Boke

I.T.U. Mechanical Engineering Faculty, Istanbul Technical University, 34437 Istanbul, Turkey

e-mail: [email protected]

I. Dincer et al. (eds.), Progress in Exergy, Energy, and the Environment,DOI 10.1007/978-3-319-04681-5_38, # Springer International Publishing Switzerland 2014

435

mailto:[email protected]






with lowest exergy consumption rate with the human body. This suggests that rational heating and cooling systems in

building would go well with low exergy consumption under a condition in which we humans consume as low amount of

exergy as possible. That is we may be able to establish both thermal comfort and low exergy consuming systems at the

same time.

Human body doesn’t sense just the temperature of the air, but also feels the operative temperature that is combination of

air temperature, air humidity, air velocity, and radiant temperature. According to this relationship lowest exergy consump-

tion rate emerges at the point where the room air temperature equals 18 �C and mean radiant temperature 25 �C [1].

This suggest that use of warm radiant energy is more effective than use of convective warm energy for a heating purpose to

realise both thermal comfort and as low exergy consumption within human body as possible.

The work concerning low exergy systems (LowEx) by Virtane and Ala-Juusela [2, 3] encourages the use of low

temperature heating systems for buildings. Low exergy heating systems allow the use of low valued energy sources. Such

heating system operates at low temperature levels that are close to room temperature. These systems can provide the

occupants with comfortable, clean, and healthy environment. In addition, low temperature systems lead to efficient use of

energy and provide flexibility in the choice of the energy source. To the knowledge of the authors, there are only a few

papers available about low temperature heating systems.

Low temperature heating with heat pump or other low temperature devices has several advantages. When using, for

example, a heat pump in low temperature systems, energy may be saved because the thermal efficiency of the pump (COP)

increases and energy loses in the distribution net decrease. Energy efficiency aside, studies show that low temperature

heating may improve indoor air quality as well as the thermal comfort conditions [4–7].

Scientist and engineers are concerned about new heating and cooling systems in buildings due to conventional air

conditioning systems consuming large amount of energy. As a result of their studies, radiant heating and cooling systems

which can produce more comfortable conditions in occupied zone and energy saving are developed. Working principle of

radiant system is based upon at least 50 % of heat transfer occurring via radiation from radiant panel placed on floor, wall, or

ceiling. By the radiant panel heat transfer occurs in two ways, primarily via radiation between panel surface and occupants

which constitutes 60–80 % of heat transfer and secondarily, heat transfer to indoor air by means of natural convection [8].

The intent of radiant systems is to lower thermostat set point temperature in winter and to increase it in summer, resulting

in substantial energy savings for heating and cooling as compared with conventional systems [9]. A forced convection

air-conditioning system creates uncomfortable environment caused by draught and air temperature differences between the

human head and foot, whereas radiant air-conditioning systems can provide lower vertical air temperature differences

and air velocity. At a given volume flow rate, water is about 4,000 times more efficient for heat transport than air.

Therefore, water heating systems are very common in Europe, and hydronic cooling systems progressively replace

air conditioning [10].

Thermal Comfort

As defined by ASHRAE Standard 55, thermal comfort is that condition of the mind that expresses satisfaction with

the thermal environment. Thermal comfort is investigated considering both general and local thermal sensation of the

human body.

General Thermal Comfort

General thermal comfort that is mainly related to PMV–PPD index can be expressed as mathematically and occupant’s

thermal sensation temperature by the whole body called as operative temperature. PMV consists of six comfort variables

(metabolic rate, clothing insulation, ambient air temperature, mean radiant temperature relative humidity, and air velocity)

and is expressed Eq. (38.1) [11] as

436 A. Koca et al.

PMV ¼ 0:303 � e�0,036�M þ 0:028� �

M �Wð Þ � 3:05 � 10�3 � 5733� 6:99 � M �Wð Þ � paf g�0:42 � M �Wð Þ � 58:15f g � 1:7 � 10�5 �M � 5867� pað Þ�0:0014M 34� Tað Þ � 3:96 � 10�8f cl Tcl þ 273ð Þ4 � Tr þ 273ð Þ4

n o

�f cl � h � Tcl � Tað Þ

2666664

3777775

ð38:1Þ

PPD is expressed via Eq. (38.2) using PMV index value [11]:

PPD ¼ 100� 95 � exp �0:03353 � PMV4 � 0:2179 � PMV2� � ð38:2Þ

Operative temperature is not equal to the ambient air temperature and is affected by surface and object temperatures of

indoor environment. When mean air speed is less than 0.2 m/s, operative temperature is calculated by Eq. (38.3):

T0 ¼ Tr þ Ta

2ð38:3Þ

General thermal comfort criteria which are described by the standards ISO 7730 are shown in Table 38.1.

Local Thermal Comfort

In the earlier years of thermal comfort studies, comfort was usually described as affected by the occupant’s thermal sensation

by the whole body. But aside from the overall thermal state of the body, an occupant may also find the thermal environment

unacceptable if local influences on the body from radiant temperature asymmetry, draught, vertical air temperature

differences, and cold or warm floors.

Radiant temperature asymmetry is the difference between the maximum and the minimum radiant temperature on the

surfaces of a cube element located at a point in the space being conditioned [3].

Draught is the unwanted local cooling of the body caused by air movement.

Vertical air temperature difference is a high vertical air temperature difference between the ankle and the head (0.1 and

1.1 m above the floor) which usually causes discomfort. This air temperature difference should be less than 3 �C.Floor surface temperature is especially important for thermal comfort assessment of spaces with occupants wearing light

indoor shoes or in cases where occupants sit/lie on the floor or walk indoors with bare feet as common in Asia.

Room Modeling

A CFD model with dimensions 6 m � 4 m � 3 m is designed. Two single-glazed windows which are included in the CFD

model have 1.4 m height and 1.2 m weight. Four different room models are obtained to be placed on wall surfaces of panels

with dimensions 0.6 m � 1.2 m as shown in Fig. 38.1; panels are installed all around of the window in the first model

(Fig. 38.1a), windowless exterior wall in the second model (Fig. 38.2a), either walls in the third model (Fig. 38.3a), and

ceiling in the fourth model (Fig. 38.4a). The TS 2164 standards identify four different regions in Turkey with regard to

outdoor climate conditions in winter used in heating systems design. Each region has been represented in numerical analysis

by setting these climatological parameters as boundary conditions in heating mode (Table 38.2), where in the case of

cooling, summer conditions as well as incident radiation through window are taken into account.

Table 38.1 General thermal

comfort criteriaParameter Limit value

PMV �0.5 < PMV < 0.5

PPD (%) PPD < 10

Operative temperature (�C) Winter (1 clo/1.2 met) 20–24Summer (0.5 clo/1.2 met) 23–26

38 Thermal Comfort Analysis of Novel Low Exergy Radiant Heating Cooling System. . . 437

Fig. 38.1 (a) Model 1;

(b) Model 2; (c) Model 3;

(d) Model 4

a bVelocity

0.130

0.098

0.065

0.033

0.000[m s∧−1]

Temperature

295.987

297.614

294.361

292.734

291.108

289.481

287.855[K]

Fig. 38.2 (a) Streamline distribution in model 2; (b) Model 2 surfaces temperature distribution

0

20

40

60

80

100

-3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3

PP

D (

%)

PMV

Fig. 38.3 The relationship

between PMV and PPD

for model 2

438 A. Koca et al.

Numerical Solution Method

In fluid mechanics and heat transfer, basis of conservation equations stated as mathematical treatment of fluid depends on

conservation of mass, momentum, and energy. In this study, flow is steady state and three dimensional, and physical

properties of the fluid such as density, viscosity, and thermal conductivity are constant. Consequently, conservation

equations are obtained as below [12]:

Continuity equation,

∂u∂x

þ ∂v∂y

þ ∂w∂z

¼ 0 ð38:4Þ

Momentum equations of x, y, z direction can be stated, respectively:

u∂u∂x

þ v∂u∂y

þ w∂u∂z

¼ � 1

ρ

∂p∂x

þ ν∂2u

∂x2þ ∂2u

∂y2þ ∂2u

∂z2

� �ð38:5Þ

u∂v∂x

þ v∂v∂y

þ w∂v∂z

¼ � 1

ρ

∂p∂y

þ ν∂2v

∂x2þ ∂2v

∂y2þ ∂2v

∂z2

� �� g ð38:6Þ

u∂w∂x

þ v∂w∂y

þ w∂w∂z

¼ � 1

ρ

∂p∂z

þ ν∂2w

∂x2þ ∂2w

∂y2þ ∂2w

∂z2

� �ð38:7Þ

Energy equation can be stated as below:

u∂T∂x

þ v∂T∂y

þ w∂T∂z

¼ α∂2T

∂x2þ ∂2T

∂y2þ ∂2T

∂z2

� �ð38:8Þ

Fig. 38.4 Reference line 1, 2, 3

Table 38.2 Outside air temperature in different region for cooling and heating season

Region City

Heating season outside

air temperature (�C)Cooling season outside

air temperature (�C)1 Antalya 3 39

2 Istanbul �3 33

3 Ankara �12 35

4 Erzurum �21 31


Between radiant panels and indoor air, heat transfer occurs via natural convection which has been modeled by employing

Boussinesq method that yields good results provided with small difference in extremum values of temperature within the

space in question. Turbulence is simulated by the standard k-ε model which is reported to be a good approximation

especially for near-wall flows. Radiation heat transfer has been represented by employing the Discrete Ordinates method

which takes account scattering, semi-transparent media, reflecting surface, and wavelength-dependent transmission [13].

Results and Discussion

Heating Cases of Study

Room has two exterior and interior walls, a ceiling, and floor. This room heating analysis is done when room situate in

self-contained flat. In this case, ceiling, floor, and interior walls of the room are neighbor to cockloft, ground, and unheated

space, respectively. Heating analysis was made for room model 1, 2, 3.

Results of Heating CasesAnalysis results will be expressed with regard to model 2. These results were obtained when panel heating performance

was 35 W/m2, considering second region’s outside air condition. Figure 38.2a shows velocity streamline in room.

Natural circulation of air flow in contact with warm panel surface is obviously shown in Fig. 38.2a. On the panel, surface

had air speed 0.13 m/s which is the highest air velocity in the room. Figure 38.2b represents temperature distribution on

walls, window, and panels. Warmed panel, cold window, and whole wall surface mean temperatures were found to be

296.4, 288, and 292 K, respectively, in the room.

Investigation of General Thermal Conditions Comfort for Room Model 2

General thermal comfort is based on PMV and PPD indices and operative temperature. Therefore, these parameters must be

calculated. The PMV value is calculated from Eq. (38.1). For the purpose of solving this equation, mean radiant temperature

that must be calculated is expressed in Eq. (38.9) [14].

Tr ¼ Tp þ Taust

2ð38:9Þ

Panel surface temperature (Tp) was found to be 296.4 K as a result of numerical analysis. Area-weighted unheated surface

temperature (Taust) was calculated as 292 K with Eq. (38.10) [14].

Taust ¼ Ts1 � As1 � εs1 þ Ts2 � As2 � εs2 þ . . .þ Tsn � Asn � εsnð ÞAs1 � εs1 þ As2 � εs2 þ . . .þ Asn � εsnð Þ ð38:10Þ

Depending on these values, mean radiant temperature (Tr) was estimated to be 294.1 K using Eq. (38.9). As a result

of numerical analysis, mean air temperature and air velocity were found to be 292.5 K and 0.013 m/s, respectively. Clothing

in winter, metabolic rate of occupants, and relative humidity were admitted 1 clo, 1.2 met, and 50 %, respectively [11].

Values of these six comfort variables are shown in Table 38.3.

Operative temperature was computed 293.3 K with Eq. (38.3). PMV and PPD values were estimated by computer

program which is written based on ASHRAE 55 and ISO 7730 standards. Values of the these parameters are shown in

Table 38.4.


comfort input values for model 2Parameter Input values

Clothing insulation (clo) 1

Mean air temperature (�C) 19.5

Mean radiant temperature (�C) 21.1

Metabolic rate (met) 1.2

Air velocity (m/s) 0.013

Relative humidity (%) 50

440 A. Koca et al.

The relationship between PMV and PPD is shown in Fig. 38.3. Intersection of PMV and PPD values is within the region

defined by thermal comfort

Investigation of Local Thermal Comfort Conditions for Room Model 2

The occupied zone is defined as a space 0.6 m distant from all walls and up to 1.8 m above floor level [9]. Most critical plane

in the occupied zone is farthest from panels. Reference lines were all in the critical plane and the reference lines 1, 2, and 3

were 0.6, 3, and 5.4 m distant from exterior wall which has a window, respectively (Fig. 38.4).

Temperature differences between 0.1 and 1.1 m above the floor on reference line 1, 2, and 3 were found to be 0.4, 0.3, and

0.5 �C, respectively. None of the values exceed recommended limit that is given by ISO 7730 (Table 38.5).

Maximum air velocities on reference line 1, 2, and 3 were obtained as 0.013, 0.01, 0.017 m/s, respectively. These air

velocities are less than 0.18 m/s described by ISO 7730 (Table 38.6).

Figure 38.5 represents temperature distribution in the middle plane of the room. The difference between highest and

lowest temperature is 0.34 K, which is under the standard limitation of 23 K (radiant temperature asymmetry caused by

warm vertical wall) set by ISO 7730.

Room floor surface temperature was found to be 19.2 �C which is the range of floor surface temperatures (19–29 �C)described by ISO 7730.


comfort output values for model 2Parameter Output values

Operative temperature (�C) 20.3

PMV �0.28

PPD (%) 6.63

Table 38.5 Vertical air

temperature differences

0.1–1.1 m on reference line

Reference line T0.1 (K) T1.1 (K) T1.1–T0.1 (K) ISO 7730 (K)

1 292 292.4 0.4 <3

2 292.1 292.4 0.3 <3

3 291.8 292.3 0.5 <3

Table 38.6 Maximum air

velocities on reference lineReference line Maximum speed (m/s) ISO 7730 (m/s)

1 0.013 <0.18

2 0.01 <0.18

3 0.017 <0.18

Fig. 38.5 Temperature

distribution in the middle

plane of the room


Investigation of Thermal Comfort as Regards Clothing Insulation and Metabolic Rate

The relationship between PPD and clothing insulation is shown in Fig. 38.6. Thermal comfort requirement is provided in the

range of 1–1.6 clo. Clothing insulation and PPD values of the optimal thermal comfort are 1.2 clo and 5 %, respectively.

Figure 38.7 presents the relationship between PPD and metabolic rate. Thermal comfort is satisfied from 1.2 to 1.6 clo, so

occupants feel comfortable themselves in this metabolic rate range in room. Clothing insulation and PPD values of the

optimum thermal comfort are 1.3 met and 5.13 %, respectively.

Cooling Cases of Study

Room cooling analysis is done when room situate in mezzanine, so heat loss takes place from exterior walls and window

only. Cooling analysis was made for all room models.

Results of Cooling CasesAnalysis results will be explained considering model 4. These results were obtained when panel cooling performance

was 18 W/m2, considering second region’s outside air condition. Figure 38.8a represents velocity streamline in model 4,

and maximum air speed was 0.111 m/s. Figure 38.8b demonstrates temperature distribution on whole room surfaces.

Warm window, cooled panel, and other wall surface temperatures were found to be 302.2, 299, and 296.8 K, respectively.

Investigation of General Thermal Comfort Conditions for Room Model 4

Parameters of calculating PMV were given as follows: clothing, 0.5 clo in summer; metabolic rate of occupant, 1.2 met;

relative humidity, 50 % [11]. As a result of numerical analysis, mean air temperature and air velocity were found to be

298.5 K and 0.018 m/s, respectively, and mean radiant temperature was found to be 297.9 K using with Eq. (38.9).

Consequently, the values of these six comfort variables are shown in Table 38.7.

PMV, PPD, and operative temperature values are shown in Table 38.8. These values show that thermal comfort is provided.

0

5

10

15

20

25

30

35

0.5 1 1.5 2 2.5

PP

D (

%)

Icl (clo)


between PPD and clothing

insulation

0

5

10

15

20

25

30

35

40

45

0.5 1 1.5 2 2.5

PP

D (

%)

Metabolic rate (met)


between PPD and metabolic rate

442 A. Koca et al.

Minimum Heat Flux Requirements from Radiant Panels in the Case of Heating and Cooling

Minimum heat fluxes from radiant panels and corresponding values of PMV, PPD, and room mean temperature are shown

for different region and heating/cooling in Tables 38.9 and 38.10. Mean air temperature of model 1 became lower in cooling

and higher in heating than other models for different regions.

Comparison of Radiant and Conventional Systems Under Similar Thermal Conditions

Having compared radiant and conventional heating systems under similar thermal conditions, indoor air temperature was

found to be 1.1 �C less in case of radiant heating than that of conventional heating because mean radiant temperature in

radiant heating was 1.1 �C higher than in convective heating (Table 38.11).

baVelocity

0.111

0.083

0.055

0.028

0.000[m s∧−1]

Temperature

302.352

301.473

300.594

299.715

298.837

297.958

297.079

296.200

295.322[K]

Fig. 38.8 (a) Streamline distribution in model 4; (b) Model 4 surfaces temperature distribution


comfort input values for model 4Parameter Input values

Clothing insulation (clo) 0.5

Mean air temperature (�C) 25.5

Mean radiant temperature (�C) 24.9

Metabolic rate (met) 1.2

Air velocity (m/s) 0.018

Relative humidity (%) 50


comfort output values for model 4Parameter Output values

Operative temperature (�C) 25.2

PMV 0.21

PPD (%) 5.91

Table 38.9 Minimum heat flux requirements from radiant panels for different regions in heating

Region

Model 1 Model 2 Model 3

1 2 3 4 1 2 3 4 1 2 3 4

Heat flux (W/m2) 60 70 90 110 30 35 45 55 15 20 25 30

PMV �0.47 �0.29 �0.32 �0.39 �0.35 �0.28 �0.29 �0.32 �0.48 �0.28 �0.37 �0.44

PPD (%) 9.61 6.75 7.13 8.17 7.55 6.63 6.75 7.1 9.81 6.63 7.85 9.04

Operative temperature (�C) 20 20.4 20.4 20.2 20 20.3 20.3 20.2 20 20.2 20 20

Mean air temperature (�C) 17.2 18.4 17.8 17 19.2 19.5 19.2 18.9 18.9 19.7 19.2 18.8


Annual Energy Saving in the Case of Radiant Heating and Cooling

Table 38.12 demonstrates annual energy savings using radiant heating system for different regions. There is remarkable

energy saving using radiant system for heating. Energy saving was larger at regions where heating load was higher and could

reach maximum level in the coldest region. The more energy saving could be achieved using model 3.

Annual energy savings are shown for radiant cooling system in Table 38.13. Model 3 has maximum energy saving,

whereas model 4 has minimum energy saving. Energy saving is larger at regions where cooling load is higher.

Conclusion

Thermal comfort and energy efficiency performance of the novel radiant heating and cooling systems were investigated with

CFD method according to different building and heating/cooling system configurations in this study. The following

conclusions have been reached:

• The use of radiant heating and cooling systems in a model room fulfills general and local thermal comfort requirements

with lower air temperature for heating and higher air temperature for cooling than conventional system

Table 38.13 Annual energy saving use of radiant cooling systems

Region

Energy saving (Turkish currency)

Model 1 Model 2 Model 3 Model 4

1 25.7 30.0 36.4 15.1

2 15.0 15.0 16.7 10.1

3 11.9 12.5 14.5 7.6

4 1.3 1.5 1.6 1.1

Table 38.10 Minimum heat fluxes requirements from radiant panels for different regions in cooling

Region

Model 1 Model 2 Model 3 Model 4

1 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4

Heat flux (W/m2) 54 47 49 44 25.5 23.5 24 21 15.5 15 15 13.5 20.5 17.5 18.5 15.5

PMV 0.25 0.35 0.35 0.37 0.32 0.33 0.44 0.43 0.31 0.29 0.4 0.4 0.36 0.38 0.39 0.37

PPD (%) 6.3 7.55 7.55 7.85 7.13 7.26 9.04 8.86 7 6.75 8.33 8.33 7.7 8.01 8.17 7.85

Operative temperature (�C) 25.2 25.6 25.6 25.7 25.6 25.6 25.9 25.9 25.5 25.5 25.8 25.8 25.7 25.8 25.8 25.5

Mean air temperature (�C) 27 27 27 26.9 26.1 26.2 26.6 26.4 26 25.8 26.2 26.1 26 26.1 26.1 26

Table 38.11 Comparison of radiant and conventional systems

Parameter Radiant heating Conventional heating

Input Clothing insulation (clo) 1 1Mean air temperature (�C) 20.9 22Mean radiant temperature (�C) 22.3 21.2Metabolic rate (met) 1.2 1.2Air velocity (m/s) 0.028 0.028Relative humidity (%) 50 50

Output Operative temperature (�C) 21.6 21.6PMV 0 0PPD (%) 5 5

Table 38.12 Annual energy saving use of radiant heating systems

Region

Energy saving (Turkish currency)

Model 1 Model 2 Model 3

1 79.0 79.0 100.7

2 143.2 143.2 179.4

3 178.5 178.5 233.8

4 268.2 268.2 333.7

444 A. Koca et al.

• All investigated radiant heating and cooling systems gave an acceptable indoor environment, which has smaller vertical

temperature differences and almost no air movement field

• In order to meet the conditions of thermal comfort required heat flux from radiant panels are obtained numerically for

different regions

• There is remarkable energy saving using radiant system for heating, even much more in colder areas in Turkey. In cooling

season energy saving associated with radiant system is lower than it is in heating season, since there is a smaller

difference between values of indoor and outdoor temperature, and furthermore, cooling period is shorter than its heating

counterpart.

• Both in heating and cooling cases, energy savings increase when panels are placed and heat loss occurred in either

exterior walls

Nomenclature

As Surface area

M Metabolic rate, W/m2

W Effective mechanical power, W/m2

pa Water vapour partial, Pa

Ta Air temperature, �Cfcl Clothing surface area factor

Taust Area-weighted unheated surface temperature, �CTcl Clothing surface temperature, �CTo Operative temperature

Tp Panel surface temperature, �CTr Mean radiant temperature, �C

Ts Surface temperature

T0.1 Air temperature at 0.1 m above floor level, �CT1.1 Air temperature at 1.1 m above floor level, �Ch Convective heat transfer coefficient, W/m2�Cu Velocity component in x direction, m/s

v Velocity component in y direction, m/s

w Velocity component in z direction, m/s

x,y,z Cartesian coordinates

p Pressure, Pa

g Acceleration of gravity

Greek Letters

ρ Density, kg/m3

α Thermal diffusivity coefficient

ε Emissivity

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Progress in Exergy, Energy, and the Environment || Thermal Comfort Analysis of Novel Low Exergy Radiant Heating Cooling System and Energy Saving Potential Comparing to Conventional