PRESENTATION TITLE. Effect of Supply Air Temperature on Indoor Thermal Comfort in a Room with Radiant Heating and Mechanical Ventilation

Transcription

1 IREE 2017 Wollongong, Australia Effect of Supply Air Temperature on Indoor Thermal Comfort in a Room with Radiant Heating and Mechanical Ventilation Xiaozhou Wu Ph.D Centre for Building Energy Conservation, CBEC Xi an Jiaotong University, XJTU

2 Content 1. Background PRESENTATION 2. Methodologies TITLE 3. Results and conclusions 2

3 1. Background 3

4 Thermal comfort ISO 7730: Thermal comfort is that condition of mind which expresses satisfaction with the thermal environment. 4

5 Heat exchange between human and environment Respiration and evaporation 25~30% Radiation Convection 45~50% 25~30% Convective heating systems: Radiator or convector heating systems Radiant heating systems: Floor or ceiling heating systems 5

6 Vertical air temperature gradient Ideal vertical air temperature gradient Height 1 Convector Heating 2 Radiator Heating 3 Ceiling Heating 4 Floor Heating Compared with convective heating systems, radiant heating systems have lower temperature gradient and better thermal environment 6

7 Instalment of fresh air supply system Building energy efficient technology Increased thermal insulation Increased air tightness Insufficient fresh air supply Fresh air supply system: mixing or displacement ventilation systems 7

8 Hybrid systems The radiant heating systems should be combined with mechanical ventilation systems, such as mixing ventilation systems (MV) and displacement ventilation (DV). Floor Heating+ Mixing Ventilation (FH+MV) Floor Heating + Displacement Ventilation (FH+DV) Ceiling Heating + Mixing Ventilation (CH+MV) Ceiling Heating + Displacement Ventilation (CH+DV) 8

9 Indoor thermal comfortandard High comfortandards International Standard ISO7730 PMV -0.5 ~0.5 PPD <10% Draught <10% Temperature gradient <3 9

10 2. Methodologies 10

11 Test room The room has an approximate floor area of 72m 2 and a ceiling height of 2.7m Eight heated cylinders equipped with 80W light bulbs, computers and lights were resulting in a total power of 1650W.

12 Tesystems Ceiling heating Mixing ventilation Displacement ventilation Floor heating 12

13 Test conditions Hybrid systems FH+MV FH+DV CH+MV CH+DV Supply air temperature ( ) Supply air flow rate G (l/s) Nominal air temperature t a ( ) Ceiling surface temperature t c ( ) Floor surface temperature t f ( ) Internal heat load Q i (W) / ~ / ~ / ~ / ~ / ~ / ~ ~29.0 / ~27.0 / ~25.0 / ~29.0 / ~27.0 / ~25.0 / 1650

14 Measuring parameters Space air temperature, velocity and globe temperature Air temperature and globe temperature sensors as well as low velocity anemometer 14

15 3. Results and conclusions 15

16 Vertical air temperature profiles =19 =19 t t t = a a1.1 a0.1 PRESENTATION Hybrid Vertical air temperature difference TITLE ( ) systems = FH+MV FH+MV Mean air temperature ( ) Mean air temperature ( ) FH+DV t s CH+MV =19 =19 CH+DV FH+DV CH+MV CH+DV Mean air temperature ( ) Mean air temperature ( )

17 Vertical air velocity profiles 0.62 (34 - =19 a ) ( a - 5) (0.37 a 3.14) =19 DR = t v v Tu + = Draught near the neck(%) =15.0 = = Hybrid systems FH+MV Tu SD v v Mean air velocity (m/s) FH+MV Mean air velocity 5.6 (m/s) FH+DV 0.5 CH+MV CH+DV =19 100% FH+DV =19 CH+MV CH+DV Mean air velocity (m/s) Mean air velocity (m/s)

18 Vertical globe temperature profiles =19 =19 t =t v ( t - t ) r g a g a PRESENTATION Hybrid Mean radiant temperature ( ) TITLE systems =15.0 =17.0 = FH+MV FH+MV Mean globe temperature ( ) Mean globe temperature ( ) FH+DV t s CH+MV t s =19 =19 CH+DV FH+DV CH+MV CH+DV Mean globe temperature ( ) Mean globe temperature ( )

19 PMV-PPD Hybrid PMV in a typical room with normal workers (-) systems =15.0 =17.0 =19.0 FH+MV FH+DV CH+MV CH+DV Hybrid PPD in a typical room with normal workers (%) systems FH+MV = t s = = FH+DV CH+MV CH+DV

20 Conclusions The supply air temperature had nearly no impact on the vertical air temperature difference in the occupied zone for FH+MV or CH+MV, while it had a clear influence on the vertical air temperature difference in the occupied zone for FH+DV or CH+DV. The PRESENTATION supply air temperature had a slight impact TITLE on the draught near the neck for FH+MV or CH+MV, but nearly had no influence on the draught near the neck for FH+DV or CH+DV. The supply air temperature had a slight impact on the PMV- PPD for the four hybrid systems.

21 QUESTIONS? Xiaozhou Wu,Ph.D/Associate Professor Centre for Building Energy Conservation, CBEC Xi an Jiaotong University, XJTU ResearchGate/Linkedln: Xiaozhou Wu