Greenhouse Ventilation Rate: Theory and Measurement with Tracer Gas Techniques

Baptista, F.J.; Bailey, B.J.; Randall, J.M.; Meneses, J.F.

doi:10.1006/jaer.1998.0381

Cited by 110 publications

(54 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…We noticed that 6 h after the meal distribution the quantity of feed remaining in the trough was close to the quantity of refusals (0.05 to 0.10 of feed offered); from that time, interference was probably negligible. NH 3 emission measurements were therefore only considered between 1200 and 0700 h and between 1400 and 1700 h. The flow rate in each experimental room was determined with the tracer ratio method using the constant dosing approach (Baptista et al, 1999). Sulphur hexafluoride (SF 6 ) was continuously injected through PTFE sampling lines directly in the air entrance duct equipped with a mixing system to homogenise air and SF 6 .…”

Section: Measurements and Analysesmentioning

confidence: 99%

Low degradable protein supply to increase nitrogen efficiency in lactating dairy cows and reduce environmental impacts at barn level

Edouard

Hassouna

Robin

et al. 2016

animal

View full text Add to dashboard Cite

Generally, <30% of dairy cattle's nitrogen intake is retained in milk. Large amounts of nitrogen are excreted in manure, especially in urine, with damaging impacts on the environment. This study explores the effect of lowering dietary degradable nitrogen supplies -while maintaining metabolisable protein -on dairy cows' performance, nitrogen use efficiency and gas emissions (NH 3 , N 2 O, CH 4 ) at barn level with tied animals. Two dietary N concentrations (CP: 12% DM for LowN; 18% DM for HighN) were offered to two groups of three lactating dairy cows in a split-plot design over four periods of 2 weeks. Diets were formulated to provide similar metabolisable protein supply, with degradable N either in deficit or in excess (PDIN of 84 and 114 g/kg DM for LowN and HighN, respectively). Cows ingested 0.8 kg DM/day less on the LowN diet, which was also 2.5% less digestible. Milk yield and composition were not significantly affected. N exported in milk was 5% lower (LowN: 129 g N/day; HighN: 136 g N/day; P < 0.001) but milk protein yield was not significantly affected (LowN: 801 g/day; HighN: 823 g/day; P = 0.10). Cows logically ingested less nitrogen on the LowN diet (LowN: 415 g N/day; HighN: 626 g N/day; P < 0.001) resulting in a higher N use efficiency (N milk/N intake; LowN: 0.31; HighN: 0.22; P < 0.001). N excreted in urine was almost four times lower on the LowN diet (LowN: 65 g N/day; HighN: 243 g N/day; P < 0.001) while urinary urea N concentration was eightfold lower (LowN: 4.6 g/l; HighN: 22.9 g/l; P < 0.001). Ammonia emission (expressed in g/h in order to remove periods of the day with potential interferences with volatile molecules from feed) was also lower on the LowN diet (LowN: 1.03 g/h per cow; HighN: 1.25 g/h per cow; P < 0.05). Greenhouse gas emissions (N 2 O and CH 4 ) at barn level were not significantly affected by the amount of dietary N. Offering low amounts of degradable protein with suitable metabolisable protein amounts to cattle improved nitrogen use efficiency and lowered ammonia emissions at barn level. This strategy would, however, need to be validated for longer periods, other housing systems (free stall barns) and at farm level including all stages of manure management.

show abstract

Section: Measurements and Analysesmentioning

confidence: 99%

Low degradable protein supply to increase nitrogen efficiency in lactating dairy cows and reduce environmental impacts at barn level

Edouard

Hassouna

Robin

et al. 2016

animal

View full text Add to dashboard Cite

show abstract

“…Through promoting the exchange between indoor and outdoor air, natural ventilation can dissipate surplus heat and vapor in summer, while it can exclude excessive vapor and provide a suitable thermal climate in winter (Baptista, Bailey, Randall, & Meneses, 1999). However, the ventilation mechanism is complex and poorly understood, since it depends on many factors.…”

Section: Introductionmentioning

confidence: 99%

The effect of vent openings on the microclimate inside multi-span greenhouses during summer and winter seasons

Chen

Sun

et al. 2015

Engineering Applications of Computational Fluid Mechanics

View full text Add to dashboard Cite

In research literature, little attention has been applied to the effect of vent openings on greenhouse climates during cooling and dehumidification processes with natural ventilation, which would provide guidelines for greenhouse management. To address this problem, a 3D CFD model was successfully designed based on 11-span plastic greenhouses. The model was validated with the measured air temperature and relative humidity, and then used to investigate the effects of vent configuration and opening size on the greenhouse climate. The simulations show that the vent configuration affects greenhouse microclimate patterns and the spatial and temporal variations of the internal climate. Meanwhile, the vent opening size affects greenhouse dehumidification time, air temperature and relative humidity during the dehumidification process. Finally, the assessments of ventilation performance highlight that the roof plus side opening is most suitable for summer cooling, while the roof opening is most suitable for winter dehumidification.

show abstract

“…Reports by Baudoin and von Zabeltitz (2002) and Fatnassi et al (2002) on airflow restrictions caused by insect screens also support this. Therefore, it is worthwhile to test the actual ventilation capacity of the insect screen using advanced research techniques such as "tracer gas technology" (Lee et al, 2000) or "CFD modeling" (Baptista et al, 1999).…”

Section: Discussionmentioning

confidence: 99%

Natural ventilation in insect screened single span greenhouses under warm weather

Weerakkody¹,

Amarathunga²,

Warnakulasooriya³

et al. 2010

International Journal of Biological and Chemical Sciences

View full text Add to dashboard Cite

The ventilation rates of different types of ridge vents in combination with insect-screened side vents were assessed in single greenhouses in terms of the difference in temperature and humidity inside and outside under tropical conditions. The A-frame (slanted roof) was comparatively advantageous over the conventional arch frame (curved roof) for keeping daytime temperature lower in single span greenhouse with insect-screened side vents (mesh size: 1 by 1 mm) and without roof vents. The inclusion of ridge vents further reduced the internal temperature and relative humidity (RH) in the A-frame greenhouse during the daytime. The opening area of the ridge vent within the range between 9.3% and 14% (of the floor area) did not significantly change the ventilation based internal temperature and RH when operated under low wind speeds (0.5 ± 0.5 m s -1 ). Meanwhile the effect of ridge orientation, with respect to wind direction, on greenhouse ventilation was not obvious in terms of temperature or RH under inconsistent wind directions and low wind speeds. Greenhouse ventilation positively responded to low winds (0.25 m s -1 ) by reducing internal temperature as well as RH. However, the response to a further increase in wind speed from 0.25 to 0.5 m s -1 was not significant. Based on climate control characteristics an A-frame single-span greenhouse design with double sided alternate ridge vents and insect-screened side vents could be appropriate for tropical climates under low wind speeds and inconsistent wind directions as a cost effective and user-friendly greenhouse design. Particularly, it is highly applicable for the small-scale controlled environment vegetable production in mid and low elevations in the wet zone of Sri Lanka.

show abstract

Greenhouse Ventilation Rate: Theory and Measurement with Tracer Gas Techniques

Cited by 110 publications

References 11 publications

Low degradable protein supply to increase nitrogen efficiency in lactating dairy cows and reduce environmental impacts at barn level

Low degradable protein supply to increase nitrogen efficiency in lactating dairy cows and reduce environmental impacts at barn level

The effect of vent openings on the microclimate inside multi-span greenhouses during summer and winter seasons

Natural ventilation in insect screened single span greenhouses under warm weather

Contact Info

Product

Resources

About