MOISTURE TRANSPORT THROUGH

Transcription

1 ANNEX 41 MOIST-ENG, Working Meeting, October , Porto, Portugal MOISTURE TRANSPORT THROUGH A HORIZONTAL OPENING Test setup and initial results Sergio Vera, Jiwu Rao, Paul Fazio Building Envelope Performance Laboratory - Centre for Building Studies Department of Building, Civil and Environmental Engineering CONCORDIA UNIVERSITY

2 OUTLINE INTRODUCTION OBJECTIVES EXPERIMENTAL SETUP RESULTS - Influence of temperature difference - Influence of ventilation strategy - Influence of moisture source location CONCLUSIONS AND FUTURE WORK 2

3 RESULTS AND ANALYSES SETUP OBJECTIVES INTRODUCTION INTRODUCTION Large horizontal openings, such as staircase openings, provide a large path for the transport of heat, moisture and pollutants between floors in dwellings. Moisture transport through horizontal opening has been scarcely studied (Oldengarm and de Gids, 1991 and Woloszyn, 1999). CONCLUSIONS 3

4 RESULTS AND ANALYSES SETUP OBJECTIVES INTRODUCTION Studies of mass transport (SF 6 ) through large horizontal openings: Q 12 Zone 1: T 1, ρ 1 Zone 2: T 2, ρ 2 Q 21 Buoyancy-driven flow (Kohal, 1995) ΔT (-4 K to 4 K) Size opening Location of gas source Direction of the net flow Q INLET Q 12 Zone 1: T 1, ρ 1 Q N Zone 2: T 2, ρ 2 Q 21 Forced net flow (Klobut and Siréns, 1994) Q OUTLET CONCLUSIONS Q 12 = Q 21 Q N = Q 12 -Q 21 4

5 OBJECTIVES Carry out a full-scale test to: Study the moisture transport through a horizontal opening and resulting moisture distribution. Present the test setup and initial results. The main factors studied are ventilation strategies, temperature difference between the two rooms, and the location of the moisture source. 5

6 INTRODUCTION EXPERIMENTAL SET UP Two-rooms test-hut and wall cross section OBJECTIVES Inlet Sheathing (12.5 mm) Air cavity (19 mm) Gypsum board (12.5 mm) SETUP RESULTS AND ANALYSES CONCLUSIONS 2.43 m 2.43 m Door West Door West Second floor East Opening Inlet East First floor 3.62 m z x y Outlet PVC siding z x y Stud cavity: - 2 x6 wood 24 in m - Fiber glass insulation (140 mm) Opening dimensions: 1.19m x 0.91m x 0.22m (12.3% of the floor area) 6

7 RESULTS AND ANALYSES SETUP OBJECTIVES INTRODUCTION Test conditions Outdoor conditions: -4.7±0.2ºC and 68±4%RH Supply air conditions: 0.3, 0.5 and 0.75 ACH, 18ºC and 38%RH Room s air leakage at operating conditions: being determined Finishing material: Non-hygroscopic Temperature difference: -3.5ºK to 1.8ºK Ventilation strategies: no ventilation forced net flow up-to-down independent ventilation Moisture generation: 107±2 g/h (first floor) 113±2 g/h (second floor) CONCLUSIONS I II III IV V 7

8 INTRODUCTION Indoor monitoring SETUP RESULTS AND ANALYSES CONCLUSIONS OBJECTIVES Indoor RH and temperature was monitored with 32 Vaisala RH sensors (2%RH accuracy) in each room. Indoor airflow was monitored with 19 omnidirectional anemometers. 8

9 RESULTS AND ANALYSES General results ~1.2 g/kg 0.5 ach ΔT=0.82 K Time (h) Lower room_average Lower room_max Lower room_min Upper room_average Upper room_max Upper room_min Very fast transport of water vapor from the lower room to the upper room even though with downward net flow (two-ways airflow through the opening). Air is not well mixed. HR varies up to 0.68 g/kg across each room and up to 1.2 g/kg between the two rooms. 9

10 Influence of temperature difference a) CASE II ach ΔT (ºK) Lower room_average Lower room_max Lower room_min Upper room_average Upper room_max Upper room_min c) CASE III ach 1.7 ΔT (ºK) -2.0 Lower room_average Lower room_max Lower room_min Upper room_average Upper room_max Upper room_min Negative ΔT: upper room colder b) CASE II ach ΔT (ºK) Lower room_average Lower room_max Lower room_min Upper room_average Upper room_max Upper room_min d) CASE IV ach ΔT (ºK) Lower room_average Lower room_max Lower room_min Upper room_average Upper room_max Upper room_min Positive ΔT: upper room warmer 10

11 Influence of temperature difference (cont.) CASE II ach ΔT (ºK) Lower room_average Lower room_max Lower room_min Upper room_average Upper room_max Upper room_min Colder upper room (negative ΔT) promotes air and moisture exchange between the two rooms. The temperature difference significantly influences HR in the upper room when the moisture source is in the lower room. 11

12 Influence of ventilation strategy (cases II and IV at 0.5 ach) Humdity ratio (g/kg) Lower room_average Upper room_average II IV II IV II IV 0.82 / 0.75ºK -0.19ºK / -1.5ºK HR differences between the upper and lower rooms are smaller for independent ventilation (IV) in each room at any ΔT. The influence of ventilation strategy on HR is much less when the upper floor is colder (negative ΔT). II IV 12

13 Influence of air change rate (case II) CASE II ach ΔT (ºK) CASE II ach Lower room_average Lower room_max Lower room_min Upper room_average Upper room_max Upper room_min ΔT (ºK)

14 Influence of moisture source location CASE II ach ΔT (ºK) Less impact of ΔT on HR when the moisture source is placed in the second floor. CASE III ach Lower room_average Lower room_max Lower room_min Upper room_average Upper room_max Upper room_min 1.7 ΔT (ºK)

15 CONCLUSIONS Moisture exchange between both rooms starts at the same time the moisture generation begins. A colder upper floor promotes moisture and air exchange between two rooms for cases II, III and IV. Air is not well mixed in the rooms. Significant HR difference can be found between the two rooms, especially when the upper floor is warmer. Initial results were shown, but additional analyses is needed to get better understanding of the moisture and air exchange through a horizontal opening: - Calculation of upward and downward flows versus ΔT - Airflow simulations 15