Original papersUsing CFD to assess the influence of ceiling deflector design on airflow distribution in hen house with tunnel ventilation
Introduction
An appropriate indoor environment, e.g. air temperature, humidity, air speed and air quality in a hen house is crucial to the production performance, immune function and the welfare of hens (Mashaly et al., 2004). Thermoneutral zone for adult hens is generally from 18 to 24 °C (Hulzebosch, 2005). When the ambient temperature raises above the thermoneutral zone, hens will experience heat stress due to the decreased heat release between bodies and surroundings, which could diminish the feed consumption and conversion, body weight of hens and egg weight. Meanwhile, the mortality also increases (Freitas et al., 2017, Kocaman et al., 2006, Sterling et al., 2003). Below the thermoneutral zone, the birds need to consume extra energy to maintain normal body temperature and metabolic activities. This could decrease the feed conversion efficiency, body weight of hens, egg production and affects hens’ healthy condition (Campo et al., 2008, Ipek and Sahan, 2006). Whereas the excessively high or low ambient temperature, like in many regions in China where the maximum temperature is more than 35 °C in summer and the minimum is less than −20 °C in winter, mechanical ventilation systems with cooling and heating facilities are needed and the ventilation systems should be adjusted accordingly with seasons.
One of the most widely adopted ventilation strategies in hen houses in a region with cold winter and hot summer is to apply mix ventilation in winter and tunnel ventilation in summer. The mix ventilation consists of multiple sidewall inlets and a number of exhausted fans at a gable wall. To avoid cold air supply directly into caged-hen occupied zone (CZ), sidewall inlets with bottom hinged flaps are installed to direct the cold incoming air to the upper part of house and mix with warm air there before entry into CZ (Bjerg et al., 2002, Kwon et al., 2015). In summer, the tunnel ventilation that ventilating air is drawn into one end of the house and exhausted at the other end (Lott et al., 1998), is often applied to generate higher air speed that can increase the convective heat exchange between birds and ventilation air. The tunnel system is commonly used together with evaporation cooling pad installed behind the inlet when the outdoor temperature is high. Since after evaporation cooling, the inlet air is of low temperature and high humidity, it also needs to be directed to the upper part of house by bottom hinged flaps behind the cooling pad before entering the CZ (Xin et al., 1994). To ensure the proper mixing of the cold inlet airflow, a free space above the CZ remains in such a system. The free space, which has less resistance comparing with CZ, could allow a large portion of airflow passing through to the exhaust fans at the end of house. This will diminish the air speed in CZ. However, in tunnel ventilation, air speed is vital as it has a positive correlation with the cooling effect (Simmons et al., 2003). An air speed of between 2.29 m s−1 and 2.79 m s−1 would produce approximately a 5.5–6.6 °C wind chill effect (The University of Georgia, 1998) . To avoid the short-cut of air to the free spaces, installing deflectors under the ceiling was considered as a solution that could direct the airflow to CZ and increase the air speed in it.
The deflectors under the ceiling have been employed to decrease the cross section area of a broiler house, which can increase the local air speed in animal occupied zone (AOZ) (Mostafa et al., 2012). Similarly, ceiling deflectors have also been investigated in low-profile cross-ventilation (LPCV) cow house to divert airflow into the AOZ (Harner and Smith, 2008, Harner et al., 2009, Lobeck et al., 2011). Harner and Smith found that with deflectors, the air speed in AOZ increased from 0.9 to 1.3 m s−1 to 2.7–3.6 m s−1 during the summer. Dairies had better lay-down rates as well as a corresponding increase in milk production (Harner and Smith, 2008). Deng et al. added deflectors under ceiling and over headlocks in cattle house, which increased the air speed of AOZ by 52.8% comparing to that without deflectors (Deng et al., 2014). Chen et al. arranged deflectors of 2 m height with 6 m intervals in the beef cattle barn and the air speeds in AOZ were improved by 0.3–0.6 m s−1 (Chen et al., 2017). Ikeguchi et al. investigated the airflow pattern in LPCV and found that the most suitable installation location of deflectors was 9.5 m from the inlet sidewall and the height was 2.5 m (Ikeguchi et al., 2015). However, the literature concerning the application of deflectors with varied heights and intervals in the caged-hen house with tunnel ventilation is limited.
Recently, computational fluid dynamics (CFD) has been regarded as a powerful and versatile tool to study the airflow pattern and gas emission in livestock house with mechanical ventilation (Bustamante et al., 2017, Fidaros et al., 2017, Li et al., 2017, Wu et al., 2012b). Comparing with the field and wind tunnel experiment, CFD is time and economic saving, feasible to fully control the external factors and experimental variables. Also, rather than the limited measurement points in tests, it is more convenient for CFD to obtain all relevant environmental information within the simulation zone and the airflow pattern could be analyzed quantitatively and qualitatively. Nonetheless, the accuracy of the simulations is of controversial unless the validation and verification are made (Rong et al., 2016).
This study investigated the effect of ceiling deflectors with different heights and intervals on air speed in a parental breeding hen house with CFD. The objectives of this study were: (1) investigating the feasibility of deflectors to direct airflow from ceiling zone to CZ and aisle zone; (2) studying the influence of deflectors on air speed distribution inside the house; (3) evaluating the effects of varied heights and intervals of deflectors on indoor air speed, air speed variation trend and distribution in CZ.
Section snippets
Materials and methods
Some field measurements were done in an existing farm to validate a CFD model, and then the performance of deflectors was evaluated using CFD.
The resistance coefficients of CZ
Fig. 4a revealed the static pressure distribution in the model of virtual wind tunnel with inlet velocity of 2.5 m s−1 in x direction. When treating CZ as porous media, through Eq. (1), the resistance coefficients were obtained by regression between static pressure drops (Δpx, Δpy and Δpz) and inlet velocities (vx, vy and vz) in x, y and z directions (Fig. 4b). The viscous resistance coefficients are 7461.11 m−2, 22.2 m−2 and 8400 m−2, the inertial resistance coefficients are 0.675 m−1, 1.54 m−1
Conclusions
This paper investigated the effect of deflectors on air speed and distribution in CZ. The deflectors with various heights and intervals were researched by CFD to quantify the air speed distribution. The following conclusions could be drawn:
- (1)
The deflectors could significantly increase ventilation efficiency by directing airflow from ceiling zone to CZ and aisle zone. The air speeds in CZ and aisle zone were increased by 0.66 m s−1 and 0.91 m s−1, respectively, than those without deflectors, when
Acknowledgement
Thanks to China Scholarship Council (CSC) for the scholarship (201606350035) of Qiongyi Cheng for the Ph.D. study in Denmark and the research grant of National Innovation Foundation/Advanced Technology Foundation Denmark, New hot climate ventilation system for poultry and pigs (j.nr. 17-2013-3).
References (39)
- et al.
Measurement and numerical simulation of single-sided mechanical ventilation in broiler houses
Biosyst. Eng.
(2017) - et al.
Effects of housing system and cold stress on heterophil-to-lymphocyte ratio, fluctuating asymmetry, and tonic immobility duration of chickens
Poult. Sci.
(2008) - et al.
CFD study of the influence of laying hen geometry, distribution and weight on airflow resistance
Comput. Electron. Agric.
(2018) - et al.
Application of the k–ε turbulence model to the high Reynolds number skimming flow field of an urban street canyon
Atmos. Environ.
(2002) - et al.
Computational fluid dynamics analysis of the thermal distribution of animal occupied zones using the jet-drop-distance concept in a mechanically ventilated broiler house
Biosyst. Eng.
(2015) - et al.
Reliability of turbulence models and mesh types for CFD simulations of a mechanically ventilated pig house containing animals
Biosyst. Eng.
(2017) - et al.
Animal welfare in cross-ventilated, compost-bedded pack, and naturally ventilated dairy barns in the upper Midwest
J. Dairy Sci.
(2011) - et al.
Air velocity and high temperature effects on broiler performance
Poult. Sci.
(1998) - et al.
Effect of heat stress on production parameters and immune responses of commercial laying hens
Poult. Sci.
(2004) - et al.
Computational fluid dynamics simulation of air temperature distribution inside broiler building fitted with duct ventilation system
Biosyst. Eng.
(2012)
Assessing the ventilation effectiveness of naturally ventilated livestock buildings under wind dominated conditions using computational fluid dynamics
Biosyst. Eng.
A computational fluid dynamics study of air mixing in a naturally ventilated livestock building with different porous eave opening conditions
Biosyst. Eng.
The effect of wind speed and direction and surrounding maize on hybrid ventilation in a dairy cow building in Denmark
Energy Build.
Summary of best guidelines and validation of CFD modeling in livestock buildings to ensure prediction quality
Comput. Electron. Agric.
The effects of high-air velocity on broiler performance
Poult. Sci.
Relationships among strain, performance, and environmental temperature in commercial laying hens
J. Appl. Poult. Res.
Evaluation of methods for determining air exchange rate in a naturally ventilated dairy cattle building with large openings using computational fluid dynamics (CFD)
Atmos. Environ.
An assessment of a partial pit ventilation system to reduce emission under slatted floor–Part 2: Feasibility of CFD prediction using RANS turbulence models
Comput. Electron. Agric.
Comparisons of two numerical approaches to simulate slatted floor of a slurry pit model–large eddy simulations
Comput. Electron. Agric.
Cited by (33)
The role of opened fire doors in enhanced heat exchange of long-distance utility tunnels
2024, Tunnelling and Underground Space TechnologyHeat and mass transfer model for pork carcass precooling: Comprehensive evaluation and optimization
2023, Food and Bioproducts ProcessingCFD study on the impacts of geometric models of lying pigs on resistance coefficients for porous media modelling of the animal occupied zone
2022, Biosystems EngineeringCitation Excerpt :Wu et al. (2012) concluded that the animal occupied zone could be treated as porous media when determining the air exchange rate in a naturally ventilated dairy cattle building. Cheng, Li, et al. (2018) investigated airflow in a hen house using CFD simulation by simplifying the caged-hen occupied zone into porous media. Porous media modelling in CFD simulations requires the inputs of the resistance coefficients of the inertial and viscous terms in the relationship between air speed and pressure drop of the porous media region.
Influence of tunnel ventilation on the indoor thermal environment of a poultry building in winter
2022, Building and EnvironmentStudy on the air resistance of pigs in groups based on open-source CFD code: Influence of stocking density and live weight
2022, Biosystems EngineeringCitation Excerpt :Thus, different turbulence models need be evaluated to establish an accurate numerical model. Since it is extremely difficult to obtain the experimental data for the pressure drop of groups of animals to validate the simulation model, regular geometry instead of animal models has been used in some studies (Li et al. (2019); Cheng, Li, et al. (2018)). Thus, tube bundles where there are available experimental data and empirical equations are used to provide reference data for evaluating numerical model performance.
An effective temperature derived from a mechanistic thermophysiological model for sows reared in hot climates
2022, Biosystems Engineering