ww.sciencedirect.com

b i o s y s t em s e ng i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3

Available online at w

journal homepage: www.elsev ier .com/locate/ issn/15375110

Research Paper

Computational fluid dynamics simulation of air temperaturedistribution inside broiler building fitted with duct ventilationsystem

Ehab Mostafa a,b,*, In-Bok Lee b,**, Sang-Hyeon Song b, Kyeong-Seok Kwon b, Il-Hwan Seo b,Se-Woon Hong b, Hyun-Seob Hwang b, Jessie Pascual Bitog b,c, Hwa-Taek Han d

aAgricultural Engineering Department, Faculty of Agriculture, Cairo University, El-Gammaa Street, 12613 Giza, EgyptbDepartment of Rural Systems Engineering and Research Institute for Agriculture and Life Sciences, College of Agricultural and Life Sciences,

Seoul National University, 599 Gwanangno, Gwanakgu, Seoul 151-742, South KoreacDepartment of Agricultural Engineering, Nueva Vizcaya State University, 3700 Bayombong, Nueva Vizcaya, PhilippinesdDepartment of Mechanical Engineering, Kookmin University, South Korea

a r t i c l e i n f o

Article history:

Received 14 December 2011

Received in revised form

25 March 2012

Accepted 3 May 2012

Published online 12 June 2012

* Corresponding author. Tel.: þ202 35738929;** Corresponding author. Tel.: þ82 2 880 4586

E-mail addresses: ehababdelmoniem@ho1537-5110/$ e see front matter ª 2012 IAgrEdoi:10.1016/j.biosystemseng.2012.05.001

An investigation was conducted to develop ventilation systems to prevent cold air drafts

during the winter season and create a suitable atmosphere inside the broiler rearing

building. In the cold weather, ventilation ducts and low ventilation rates are used to

maintain the required air temperature. Perforated ducts are preferred for heating spaces

because they provide efficient and uniform distribution of the entire air volume. Four

ventilation systems were designed in order to establish a comfortable zone for the broilers

during winter season. To investigate these different systems under realistic conditions,

computational fluid dynamic simulation was used. Field experiments were conducted to

validate the designed cases. From the validation results, very low errors were observed.

The improved designs were compared with the standard design in terms of ventilation

rate, air temperature distribution and indoor gas concentration reduction. Case four (C-4)

of the improved designs achieved the highest ventilation rate in the broiler zone. In C-4,

theinlet duct was installed in building side and the outlet duct in the opposite side. It

achieved about 54% of the ventilation in comparison to standard design. All improved

designs showed high uniformity ranging around 60e70% compared to the standard design.

For gas dilution in broiler zone, C-4 showed 15% ammonia reduction efficiency 3 min after

operating the ventilator.

ª 2012 IAgrE. Published by Elsevier Ltd. All rights reserved.

1. Introduction broiler chickens involved in commercial meat production was

Broiler chicken production is one of the most important live-

stock industries worldwide. In South Korea the number of

fax: þ202 35717255.; fax: þ82 2 873 2087.tmail.com (E. Mostafa), ib. Published by Elsevier Lt

estimated in September 2010 to be 71 million (SSLI, 2010).

Broilers can be placed at high stocking densities of 18 birdm�2

inside the building (Corria & Naas, 2001). However, producing

lee@snu.ac.kr (I.-B. Lee).d. All rights reserved.

Nomenclature

Abbreviations

CFD Computational fluid dynamics

RNG Renormalisation-group

RSM Reynolds stress model

TGD Trace gas decay method

Symbols

r Density, kg m�3

d Thickness of the turbulent boundary layer, m

ε Turbulent dissipation rate, m2 s�3

m Viscosity, m2 s

meff Effective viscosity (m ¼ mt), m2 s

mt Turbulent viscosity, m2 s

AER Air exchange rate, min�1

Ai, Ao Inlet and outlet vent opening areas, respectively,

m2

C Gas concentration, mass fraction

Cm Experimental constant

C0 Initial concentration, mass fraction

C1ε and C2ε Constants of value 1.42 and 1.68

C3ε tanh (u1/u2), u1 and u2 are components of the flow

velocities parallel and perpendicular, respectively,

to the gravitational vector

Ccfd Predicted values from CFD simulation

Ci Initial data

Cm Measured values

Com Average of the measured values

Cop Average of the predicated values

E Total energy, J

Ev Error between the predicted and measured values

as a percentage to the initial data

F External force vector, N m�3

g Gravitational acceleration, m s�2

Gb Generation of kinetic energy due to the buoyancy,

kg m�1 s�2

Gk Generation of turbulent kinetic energy due to the

mean velocity gradients, kg m�1 s�2

h Specific enthalpy, J kg�1

J Component of diffusion flux, kg m�2 s�1

K Turbulent kinetic energy, m2 s�2

keff Heat transmission coefficient

M Increasing weight, kg

NMSE Normalised mean square error

P Pressure, Pa

R Gas-law constant, 8.31447 � 103 J kg mol�1 K�1

Sh Total entropy, J K�1

Sm Mass source, kg m�3

T Air temperature for the livestock building, �Ct,t0 Time, s

THP Total heat production, W m�2

u, v, w Velocity, m s�1

V Internal volume of the broiler building, m3.

vi, vo Air velocities at the inlet and outlet, respectively,

m s�1

YM Contribution of the fluctuating dilatation in

compressible turbulence to the overall dissipation

rate, kg m�1 s�2

Zn Height from the ground, m

aε

Generation of kinetic energy due to buoyancy,

kg m�1 s�2

ak Generation of kinetic energy due to the mean

velocity gradients, kg m�1 s�2

s Stress tensor, Pa

b i o s y s t em s e n g i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3294

a profitable broiler requires that certain animal welfare stan-

dards are met, some even before the chicks are placed on the

farm and during the grow-out period. Providing an acceptable

air quality to the bird space becomes very important particu-

larly with high density broiler production. The main factor

responsible for improving the broilers welfare is providing an

adequate the indoor climate, which is largely effected by

thermal environmental factors. These thermal factors,

involve heat exchange among the birds and the surrounding

environment as described by (Skomorucha & Herbut, 2005). A

flock of 25,000 four-pound chickens can give off 293 kWof heat

(Bucklin, Jacob, Mather, Leary, & Naas, 2009). The age of the

animal has a significant effect on heat flux (Cangar, Aerts,

Buyse, & Berckmans, 2008). The rectal temperatures of the

bantam chicks increase consistently. The ambient tempera-

ture requirements of broilers also change with age (Gates,

Overhults, & Zhang, 1996). The level of adult thermoregula-

tion is considered to be reached when the birds are able to

maintain a constant body temperature under changing

ambient temperatures. Recommended ambient temperatures

for all broilers decline progressively from 33 to 35 �C for one

day old chicks to 18e21 �C just before they are capture for

slaughter (Bayraktar, Artuko�glu, & Altan, 2004). Heat

production of broilers is affected by body weight, food intake

and quality, and activity level. Chicks show high mortality

during their first week and therefore suitable environmental

conditions during this critical period are very important (Lee

et al., 2009)

Ventilation system can be considered as a major factor

influencing thermoregulation. Ventilation in broiler facilities

is a process of controlling several environmental factors by

diluting inside air with fresh outside air. This process will

remove the heat and excess moisture, minimise dust and

odours, limit the build-up of harmful gases such as ammonia

and carbon dioxide, and provide oxygen for respiration

(Bucklin et al., 2009). Proper ventilated housing is essential for

ensuring thermal uniformity in the zone occupied by the

broilers. Sufficient air movement is also required to keep the

litter inside the building dry. When ambient temperatures are

below that in the bird zone air speed must be kept relatively

low to conserve bird body heat. The minimum ventilation is

characterised by the need for supplementary heat tomaintain

the desired building temperature (Gates et al., 1996). During

the winter ventilation ducts could be used where low air flow

conditions are required and the ventilation rate must mini-

mised to maintain the required air temperature. Inflatable

b i o s y s t em s e ng i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3 295

low-pressure ducts provide a uniform rate of ventilation

throughout the building (Carpenter, 1972). Duct ventilation

systems have also been used to increase air temperature

distribution uniformity and to prevent cold incoming air to

directly reach directly the animal rearing zone. Perforated

ventilation ducts can provide better fresh air distribution than

free wall slotted inlets (Barrington & MacKinnon, 1990a). The

air distribution uniformity of perforated ducts is a complex

function of inter-related factors such as duct construction

materials, fan capacities and performances, perforation

geometries (sizes and spacing), duct length, and internal

cross-sectional area (El Moueddeb, Barrington, & Barthakur,

1997) and (Barrington & MacKinnon, 1990b). The critical

factor in the design of a perforated duct is the aperture ratio

(Carpenter, 1972). Outlet velocity becomes more uniform over

duct length with lower aperture ratios (Barrington &

MacKinnon, 1990a). Aperture ratios should lie between 1.5

and 2.0 (Carpenter, 1972).

Unstable weather in Korea, where the outside air temper-

ature varies from �20 to 40 �C over the year, makes it impor-

tant to adapt forced ventilation systems for broiler rearing

buildings. Improved ventilation systems must provide

internal air temperature distributions with high uniformity,

stability and suitability. The current designed of ventilation

systems used during the winter season need to be modified to

consider the energy recovery inside the building using heat

exchanger. Unstable outside weather also creates drawbacks

for temperature measurements. To overcome these

measurement limitations and get more rapid and accurate

results, aerodynamic simulations using computational fluid

dynamics (CFD) can be carried out (Lee, Sase, & Sung, 2007 and

Seo et al., 2009). The use of CFD techniques to solve complex

fluid problems has greatly increased in recent years (Blanes-

Vidal, Guijarro, Balasch, & Torres, 2008). CFD could also save

the cost, time, and effort associated with field experiments to

establish the optimum system (Lee et al., 2009) but is accuracy

needs to be assessed.

The main objective of this study was to design different

duct ventilation systems in order to establish the most suit-

able design for use during the coldwinter season. The selected

design must be able to provide a uniform and stable air

temperature distribution and decrease the indoor ammonia

concentration in the broiler zone during the winter season. It

was also an objective to use heat exchangers installation

inside the building to recover the energy.

Four duct ventilation systemswere designed for the winter

season. To test these different systems under realistic condi-

tions, a computational fluid dynamic simulation was used to

overcome the limitations of field experiments. However,

a field experiment was conducted to validate the designed

cases.

Fig. 1 e The examined broiler building in Nonsan, Korea.

2. Materials and methods

2.1. Description of broiler rearing facilities

Field experiments were conducted at a naturally ventilated

double-winch curtain broiler rearing building. The experi-

ment was conducted to examine the real conditions as well as

provide validation for CFD simulation. The measured data

were also used to provide CFD input values. The orientation of

the broiler rearing building located at Nonsan city, Chung-

cheong Province, South Korea was north-west.

The facility was stocked with 6800 broilers. As shown in

Fig. 1 the dimensions of this building were 9 m width, 42 m

length, 2.2 m eave height, and 3.7 m ridge height. Throughout

the building, double-winch curtains on each side were used to

control the air temperature by rolling it up and down. To

improve the ventilation efficiency, tunnel ventilation and pipe

inlet systems were fitted for hot and cold weather respec-

tively. For tunnel ventilation, fans (2 small with 630 mm

diameter and 2 large with 1300 mm diameter) and four inlet

slots in the back wall of the building were installed. These

inlet slots were rectangular in shape with dimensions of 1.8 m

width and 0.4 m height. Three of these slots are located at 1 m

height from the floor and one is located in the middle of the

wall at 2.5mheight. During thewinter season, pipe inlets with

100 mm internal diameter were used. These pipe inlets were

in 21 groups with 2 m spacing along each sidewall. Each group

consists of two pipes, a short pipe (0.5m) and a long pipe (3m).

Heaters are placed throughout the houses to maintain the

recommended air temperature at productive levels. Chain

feeding and tap watering stations supplied the broilers with

fodder and water but manure removal was done manually.

Litter of rice straw with 200 mm depth was distributed over

the whole building floor.

2.2. Description of the designs investigation

CFD simulations were used to analyse the air temperature

distribution and ventilation rates computed by the trace gas

decay method according to the configurations of the ventila-

tion system (Hong et al., 2008; Seo et al., 2009). The CFD

simulation were computed for four different improved venti-

lation models and compared to the standard design (tunnel

ventilation) as shown in Fig. 3. The comparison between the

four improved designs and the standard design was carried

out investigating the effectiveness the ventilation rate on the

broiler zone and maintaining uniformity, suitability, and the

stability of the internal air temperature.

During the winter low ventilation rates and perforated

ducts are recommended. To achieve uniform air distribution

from the ventilation duct, three of the design cases (C-2, C-3

and C-4) used the inlet perforated duct as shown in Fig. 2 but

a perforated outlet duct was used only with C-3 and C-4. The

inlet ducts in C-2 and C-3 were located in the middle of the

building but in C-4 the inlet duct was located close to the

Fig. 2 e Schematic diagrams for the different upgraded ventilation cases and the standard system.

b i o s y s t em s e n g i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3296

sidewall. The outlet in C-2 operated without an outlet duct

where it connects directly with the heat exchanger in the

sidewall. The inlet and outlet in C-1 were directly connected

with the heat exchanger without using ducting. Small fans

were installed in the system.

The various input values of the boundary conditions for the

three-dimensional CFD simulation models are presented in

Tables 1 and 2.

2.3. Computational fluid dynamic techniques

Three-dimensional CFD grids were generated by GAMBIT

software (ver. 2.3, Fluent, Inc.,Lebanon, NH, USA). To improve

the accuracy of the CFD model, the computational domains

were constructed using fine and dense meshes. The CFD

solver, FLUENT (ver. 6.2, Fluent, Inc., Lebanon, NH, USA), was

used to perform the CFD calculations by solving the non-

linear partial differential equations from the conversation of

mass (Eq.(1)), momentum (Eq.(2)) and energy (Eq.(3)) equations

(Lee & Short, 2000).

4.2 8.4

X X

XX

XX

X Air temperature sensor Ammonia sensor

X

X

X

X

X

X

1.6

0.4

Front view

Fig. 3 e Sensor location for air temperature a

vr

vtþ Vðr v!Þ ¼ Sm (1)

v

vtðr v!Þ þ Vðr v!v!Þ ¼ �VPþ VðsÞ þ r g!þ F

!(2)

v

vtðrEÞ þ Vð v!ðrEþ PÞÞ ¼ V

0@keffVT�

Xj

hj Jj!þ ðs v!Þ

1Aþ Sh (3)

Where Sm is mass source, kg m�3; r is density, kg m�3; u, v, w

are velocity, m s�1; t is time, s; P is pressure, Pa; s is the stress

tensor, Pa; F is external force vector, N m�3; g is gravitational

acceleration, m s�2; E is total energy, J; keff is the heat trans-

mission coefficient; h is specific enthalpy, J kg�1; J is the

component of diffusion flux, kg m�2 s�1; Sh is total entropy,

J K�1; and T is air temperature for the livestock building, �C.

Many different types of turbulence models have been

developed to solve these non-linear equations, such as the

Standard k-ε, renormalisation-group (RNG) k-ε, Realisable k-ε,

Reynolds stress model (RSM). In comparison to other models,

X X X

X

X

X

X

X

X

8.4 8.4 8.4 4.2

1.5 1.5

3.0 3.0

Top view Dimension in m

nd ammonia inside the broiler building.

Table 1 e Data and variables used in the simulations.

Pre-processing Size (m) Length: 42

Width: 9

Ridge height: 3.7

Eaves height: 2.2

Mesh Type Hexahedron, Pave, Tetra

Number of mesh w3 million

Main Module Turbulence RNG k-ε turbulence model

Discretisation Second order upwind

Conditions Unsteady state

b i o s y s t em s e ng i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3 297

RSM requires additional memory and calculating time

because of the increased number of the transport equations

for Reynolds stresses (Lee et al., 2007).

The Realisable k-ε model satisfies certain mathematical

constrains on the Reynolds stresses, and it is consistent with

the physics of turbulent flows (Lee et al., 2007). RNG k-ε

equations have similar form to the standard k-ε model equa-

tions except that the dissipation rate equation has an addi-

tional term related to the mean rate of strain and turbulence

quantities that allows it to include more physical phenom-

enon. Additionally, themodel constants are derived fromRNG

theory as opposed to being empirically based. The analytically

derived constants are very similar to the empirical constants

in the standard k-ε model. This study used the RNG k-ε model

because it followed the work by Lee et al. (2007) who investi-

gated the different turbulence numerical models for model-

ling naturaleventilated broiler buildings and concluded that

Table 2e Constant input values for the case file of the CFDmodels.

Parameter Value Unit

Incoming air temperature Standard

case

0 �C

Designed

cases

10 �C

Inside air temperature Standard

case

20 �C

Designed

cases

25 �C

Density of air 1.225 kg m�3

Viscosity of air 1.86E-05 kg m�1 s�1

Thermal conductivity

of air

0.02647 W m�1 K�1

Specific heat of air 1006.43 J kg�1 K�1

Mass diffusivity of air 2.262E-05 M2 s�1

Molecular weight of air 28.966 g mol�1

Gravitational

acceleration of air

9.81 m s�1

Atmospheric pressure 101.325 kPa

Outside CO2 concentration 0.00061

(400)

Mass

fraction (ppm)

Inside CO2 concentration 0.003

(2000)

Mass

fraction (ppm)

Generated NH3

concentration

1.77E-05

(30)

Mass

fraction (ppm)

Designed ventilation rate 0.089 Air

exchanger

min�1

The calculated heat flux in the bottom 115 W m�2

the RNG k-ε model was the most suitable. The RNG model is

less dissipative than the standard k-ε model as presented by

Analytis (2003). The renormalisation-group (RNG) k-ε turbu-

lence model is defined using Eqs. (4) and (5).

rdkdt

¼ v

vxi

�akmeff

vkvxi

�þ Gk þ Gb � rε� YM (4)

rdεdt

¼ v

vxi

�aεmeff

vε

vxi

�þ C1ε

ε

kðGk þ C3εGbÞ � C2εr

ε2

k� R (5)

Where K is turbulent kinetic energy, m2 s�2; meff is effective

viscosity (m ¼ mt), m2 s; m is viscosity, m2 s; mt is turbulent

viscosity,m2 s; ak is the generation of kinetic energy due to the

mean velocity gradients, kg m�1 s�2; aεis the generation of

kinetic energy due to buoyancy, kg m�1 s�2; Gk is the genera-

tion of turbulent kinetic energy due to the mean velocity

gradients, kg m�1 s�2; Gb is the generation of kinetic energy

due to the buoyancy, kgm�1 s�2; ε is turbulent dissipation rate,

m2 s�3; YM is the contribution of the fluctuating dilatation in

compressible turbulence to the overall dissipation rate,

kg m�1 s�2; C1ε and C2ε are constants of 1.42 and 1.68; C3ε is

tanh (u1/u2), u1 and u2 are components of the flow velocities

parallel and perpendicular, respectively, to the gravitational

vector, and R is the gas-law constant,

8.31447 � 103 J kg mol�1 K�1.

The turbulence kinetic energy (k) and turbulence dissipa-

tion rate (ε), which are important factors for inlet conditions,

were calculated using Eqs. (6) and (7) (Fluent, 2006).

k ¼ 12

�u2 þ v2 þw2

�(6)

ε ¼ C3=4m � k3=2

l; l ¼ minðk� zn; k� dÞ (7)

Where Cm is an experimental constant; Zn is height from the

ground, m and d is thickness of the turbulent boundary layer,

m.

The total heat production of the broilers was determined

using Eq. (8) presented by Xin, Berry, Tabler, and Costello

(2001) based on the assumption that the entire floor area

was fully occupied with the broilers.

THP ¼ 9:84�M0:75�4� 10�5ð20� TÞ3þ1

�(8)

Where THP is total heat production andWm�2;M is increasing

weight, kg.

2.4. Description of the experimental procedures

Meteorological data were collected at 15 s intervals using

weather station (Campbell Scientific Inc., Lagon, UT, USA).

The weather station was installed above the main building

roof (around 2.5 m height from the floor) after adjusting its

direction using a compass. Thirty calibrated hygrometers,

sampled at 1 s intervals, (H8 Hobo, Onset Inc., Pocasset, MA,

USA) were installed inside the broiler building as shown in

b i o s y s t em s e n g i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3298

Fig. 3 to determine the internal air temperature distribution.

The air volume flow from the ventilators was measured using

an air flow traverse station (Flo-probes, Taehung, Korea).

Indoor ammonia concentration was measured by using

ammonia sensors (PAC III, Draeger, Germany). The four

ammonia sensors were distributed evenly at 1 m height above

the litter and the inlet perpendicular to the airflow in the

building as established by Redwine, Lacey, Mukhtar, and

Cary (2002).

2.5. Air ventilation rate computation

As presented by Hong et al., 2008; Seo et al., 2009, the designed

ventilation rate was computed considering the volumetric

flow rate of the operating fan using Eq. (9).

AER ¼P

viAi

V¼

PvoAo

V(9)

Where AER is the air exchange rate, min�1; vi, vo are air

velocities at the inlet and outlet, respectively, m s�1; Ai, Ao are

the inlet and outlet vent opening areas, respectively,m2; andV

is the internal volume of the broiler building, m3.

The designed AER, calculated using Eq. (9), was

0.0896 min�1. There are limitations calculating the local

ventilation rate using this method since problems such as air

circulation and stagnation effects could occur. The trace gas

decay method (TGD) method was used to overcome these

problems. A trace gas was initially injected uniformly into the

CFD models and its concentration, which decreased with

ventilation, monitored. The reduction of gas concentration

was calculated at different positions and the overall and local

ventilation rate computed from:

AER ¼ln

�C0

C

ðt� t0Þ � 60 min�1 (10)

Where C0 is the initial concentration, mass fraction; C is the

gas concentration, mass fraction; and t,t0 are time and initial

time, s

Fig. 4 e Air temperature versus ventilation time curve

measured in a commercial tunnel-ventilated broiler

rearing building.

2.6. CFD validation

Validation is a most important process to ensure that the CFD

model conforms to real conditions. The measured results

from the field experiments were compared with those

obtained from CFD model. The error between the measured

and simulated data, as a percentage of the initial data (Ev), was

calculated (Eq. (11)). The validation was also examined by

calculating the normalised mean square error (NMSE) as pre-

sented by Saraz et al., 2010 using Eq. (12). Values of NMSE less

than 0.25 were accepted asindication good agreement.

Ev ¼ Ccfd � Cm

Ci(11)

NMSE ¼�Ccfd � Cm

�2�Cop � Com

� (12)

Where Ev is the error between the predicted and measured

values as a percentage to the initial data; Ccfd is the predicted

values from CFD simulation; Ci is the initial data; Cm the

measured values; Cop the average of the predicated values and

Com the average of the measured values.

3. Results and discussion

3.1. Field experiments

3.1.1. Air temperature distributionTwo 0.63 m diameter exhaust fans with gravity controlled

shutters were mounted on one side of the broiler rearing

building, while on the other side three inlet slots with 2.16 m2

opening area were located. The measured ventilation rate for

these fans during the field experiment was around 0.15min�1.

As shown in Fig. 4, with the ventilator operating the internal

air temperature declined from 33.46 to 29.34 �C at broiler zone

and from 33.42 to 29.83 �C at 2 m height while the external air

temperature is ranged between 26 and 27 �C. During thewhole

ventilation period the air temperature is decreased 4.12 and

3.59 �C for broiler zone and 2 m height respectively.

Fig. 5 shows the contour plots for the internal air temper-

ature distribution every 10 min (i.e. at 14:45, 14:55 and 15:05 h)

during the ventilation period. The ventilators were started at

14:40. The highest air temperature was located close to the

exhaust fan while the lowest was located close to the opening

slot which was affected by the fresh external air entering

through it. In the broiler zone, little change in air temperature

was observed in comparison to 2m height. This is because the

low air movement at the broiler zone maintained more

uniform air temperatures. In contrast, air velocities were

higher at 2 m height. Accordingly, the air exchange rate

increased this affected the air temperature throughout the

whole building.

3.1.2. Indoor ammonia distributionA successful ventilation system must reduce the internal

ammonia concentration in addition to creating suitable

thermal conditions. As shown in Fig. 6, similar to the results

presented by (Redwine et al., 2002) the indoor ammonia

Fig. 5 e Contour map for air temperature distribution at the second period of the experiment.

b i o s y s t em s e ng i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3 299

concentration declines with turning the ventilator on at 1 m

height from 48 to 7.3 ppmwhere the outgoing air is carrying it

outside the building. By turning the ventilator off, the indoor

concentration increased gradually. The ventilation system

clearly plays an important role to achieve 84% concentration

reduction.

3.2. CFD validation

The validation was carried out in terms of the distribution of

air temperature in the broiler zone and dilution of indoor

ammonia concentration. The error between the simulated

and measured data (Ev) for ammonia dilution did not differ

significantly since Ev was 4.3%. The NMSE value for indoor

ammonia concentration was 0.2, indicating that the model is

capable of accuracy predicting indoor ammonia concentration

reduction efficiency. In case of the air temperature distribu-

tion, the error between the simulated and measured data (Ev)

was estimated at each sensor location as is shown in Table 3.

The highest errors were observed at the 5, 10, and 15 sensor

locations. These locations were located close to the inlet slots.

Fig. 6 e Ammonia concentration versus measured at 1 m

height from the floor for a commercial tunnel-ventilated

broiler building.

The highest value was 0.46%, which is considered an accept-

able error.

The NMSE values between the results from field experi-

ment and CFD simulation showed a slight change. It could be

concluded that the designedmodels are capable of estimating

ventilation efficiency of the broiler facilities under unsteady-

state conditions.

3.3. CFD simulation

3.3.1. CFD computed ventilation rateThe ventilation rates were calculated using the time-

dependent changes in CO2 concentration where CO2 was

used as a trace gas as recommended by Kwon et al., 2011. As

shown in Fig. 7, the computed CFD results indicated high

ventilation rate for the standard design in comparison to other

improved designs. In the standard tunnel ventilation system,

a similar volume of air is moved through the whole length of

Table 3 e The error values between the measured andpredicted air temperature results.

Points Broiler zone 2 m height

Cm � CCFD Ev (%) Cm � CCFD Ev (%)

1 0.08 0.03 0.08 0.03

2 0.34 0.11 0.34 0.11

3 0.08 0.03 0.08 0.03

4 0.04 0.01 0.03 0.01

5 0.49 0.16 1.29 0.42

6 0.34 0.11 0.34 0.11

7 0.08 0.03 0.34 0.11

8 0.08 0.03 0.09 0.03

9 0.12 0.04 0.28 0.09

10 0.59 0.19 1.42 0.46

11 0.08 0.03 0.08 0.03

12 0.34 0.11 0.34 0.11

13 0.08 0.03 0.08 0.03

14 0.03 0.01 0.03 0.01

15 0.50 0.16 1.27 0.42

Average 0.07 0.13

Fig. 7 e The air ventilation rates.

b i o s y s t em s e n g i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3300

the building from one end to the other. The position of inlet

slots and exhaust fans creates a high air movement inside the

building. The air velocity for standard design at broiler zone

was 0.525m s�1 while Donlad (2003) recommended that the air

velocity on the floor duringwintertime should be < 0.25m s�1.

Another study established by Liu, Wang, Beasley, and Oviedo

(2007) indicated that the mean air velocity at a 250 mm height

is 0.24 m s�1 with a standard division of 0.14 m s�1 in a stan-

dard cross-ventilated building. During winter season, this

high air velocity creates inconsistent conditions inside the

building. The cold air also reaches directly to the animal zone

where it rapidly decreases body temperature. Using the

ventilation system, it appears to be difficult to maintain the

desired indoor temperatures during cold weather. For energy

recovery inside the broiler building, heat exchangers should

be used. It is difficult to connect the heat exchanger with inlet

pipe ventilation systemswhere the heat exchanger needs only

two connecting points for inlet and outlet. For this reason,

four port ventilation systems have be designed. The predicted

air velocities in the broiler zone for the designed ventilation

systems were 0.44, 0.31, 0.3 and 0.29 for C-1, C-2, C-3 and C-4

respectively. This means C-4 could approach the target air

velocity in the broiler zone in unlike the other designed cases.

Table 4 describes the different ventilation rates across the

whole building and the broiler zones for the improved designs

compared to the standard design. In broiler zone, the venti-

lation rate wasmore than twice that of the whole zone in case

of standard tunnel ventilation. This high ventilation rate

could be acceptable only for summer conditions. Over the

whole zone, slight differences in the ventilation rates for all

designed cases were observedwhich ranged between 0.92 and

0.96 min�1 as shown in Table 4. In the broiler zone, compared

Table 4 e Average ventilation rate for 600 s: volume airchanges per minute, minL1.

Zones Designedvent. rate

Tunnel Case1

Case2

Case3

Case4

Broiler zone 0.089 0.249 0.102 0.110 0.107 0.134

Whole building 0.106 0.092 0.093 0.096 0.093

to the standard tunnel ventilation the highest ventilation rate

appeared with C-4 where it achieved about 54% compared to

the standard design as shown in Table 3. The other cases

achieved 43, 45, and 41% for C-2, C-3, and C-1 respectively.

3.3.2. Internal air temperature distributionIn terms of air temperature distribution in broiler zone, the

standard design was analysed and the improved designs

comparedwith that. As shown in Fig. 8 a, poor air temperature

distribution uniformity was observed in the standard design

where there was a clear discrepancy between the air

temperature close to the inlet opening slots and the outlet

exhaust fans.

The air temperature in standard design in the broiler zone

ranged between 2.63 and 34.12 �C with an average of 23.86 �C,

Fig. 8 e Air temperature distribution at 3 min after the

ventilation started.

Table 5 e Comparison of air temperature distribution forall cases at broiler zone (�C).

Models Highest Lowest Average Difference

Standard 34.12 2.63 21.29 31.49

Case 1 33.25 21.98 26.52 11.27

Case 2 33.60 22.72 26.06 10.88

Case 3 34.27 23.12 26.37 11.15

Case 4 33.16 20.27 25.55 12.89

Fig. 9 e Broiler zone ammonia distribution at 3 min after

the ventilation was activated.

b i o s y s t em s e ng i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3 301

as shown in Table 5, where the lowest temperature was

located close to the inlet slots and the highest temperature

was located close to the exhaust fans. This increase in air

temperature returned to the generated heat from the floor and

the warm air is stagnating next to the exhaust fan.

As shown in Fig.8, the fresh air in C-4 enters from the inlet

duct, which is located beside the wall and the air moves to the

other side of the building transferring heat to the exhaust

outlet duct in the other side. As shown in Fig. 8a, the air

temperature distribution is similar in modelsC-2 and C-3. The

fresh air in both cases enters from inlet duct located in the

middle of the model. In C-3, the air moves symmetrically to

both sides where the outlet ducts are located. In C-2, the

exhaust air goes out through an opening area connected with

the heat exchanger in the sidewall. Accordingly, most of the

air moves from the middle to the outlet in one direction and

the other side of the building has a limited fraction of the air as

shown in Fig. 8b. The position of inlet ducts close the ceiling of

the building assists air distribution. The inlet fan pushes air

through a perforated plastic duct which distributes air down

the full length of the room (Harms & Johnson, 1985). Air close

to the ceiling will mix with the fresh air from the duct before it

reaches to the broiler zone. This process encourages heat

exchange between air with high heat capacity and fresh air

with low heat capacity.

The outlet and inlet in C-1 occur through two opening areas

connected with the heat exchanger in the sidewall. Low air

temperatures were observed in C-1 at the opposite side of the

inlet as shown in Fig. 8a. The explanation for this phenom-

enon refers as shown in Fig. 8b to the fresh air movement

inside the building. The entered air is replacing the stagnating

air close to the building wall and reduces the air temperature

in this zone.

In the case of the uniformity distribution of air tempera-

ture, using the standard division as a measure, all cases show

higher uniformity ranging (around 60e70%) than the standard

design. The highest uniformity was observed by C-2. The

uniformity in C-2 was 3.4, 0.9 and 26.5% higher than C-1, C-3

and C-4 respectively. Model C-4 showed the poorest unifor-

mity in comparison to other cases due to only one exhaust

duct being installed at the stagnant area of the hot air near to

the ceiling. This location allowed the outlet air with high

thermal capacity discharge through it to outside. This

temperature decreased slightly in C-3 because two exhaust

ducts were installed. For the fresh air movement in the broiler

zone, C-4 achieved this with little difficulty compared to other

cases, as illustrated in Fig. 8b.

In terms of thermal suitability, the recommended air

temperature for the broilers decreases from 32 to 21 �C

according to the broiler age as mentioned by Kennedy,

Leonard, & Feddes, 1991 whilst the internal air temperature

is assumed to be 25 �C as shown by Seo et al. (2009). Thermal

suitability has been examined considering the difference

between the recommended air temperature for the broilers

and the CFD results at the broiler zone. All improved designs

maintained the required air temperature for the broilers as

shown in Table 5.

3.3.3. Dilution of internal gasesReducing the indoor ammonia concentration is one of the

main targets for the successful ventilation system. Not only

does ventilation have an effect on indoor ammonia concen-

tration but the temperature also has a large influence as

mentioned by Elliott and Collins (1982). During the winter

season, especially when the broilers are newly hatched, the

air temperature in the broiler zone was high and the ventila-

tion rate was low. These conditions impact the ammonia

release. Increasing the ventilation rate to the maximum level

that does not harm the broilers but reduces the ammonia

concentration in the air is required.

The improved designs were tested in terms of removing

the internal ammonia from the broiler building. Models C-2

and C-3 showed a high uniformity of ammonia distribution

whilst poor uniformity was observed with C-1 and C-4 as

shown in Fig. 9. The reduction efficiency of indoor ammonia

concentration in the broiler zone was very high with standard

design where it achieved 23% after 3 min from turning on the

ventilator. This high reduction efficiency was caused by the

high ventilation rate. Model C-4 followed the standard design

as shown in Fig. 10 since it reduced the indoor ammonia

concentration by 15% after the same ventilation period. The

removal efficiency of indoor ammonia concentration in C-2

and C-3 were similar as shown in Fig. 10; this reduction effi-

ciency was 12.6%. The lowest reduction efficiency of the

released ammonia from the floor at broiler zone was observed

with C-1. Among the improved designs, C-4 achieved 8.5%;

lower than the standard design efficiency. The design of C-4

helped the exhaust air, which is carrying the ammonia, leave

the broiler rearing building in one direction and let the fresh

air to replace it from the other as shown in Fig. 9. This means

that, during winter season, by installing the duct ventilation

system for the inlet and outlet, as in C-4, the lowest ammonia

concentration will remain inside the building compared to

other improved designs.

Fig. 10 e Indoor ammonia concentration in broiler zone for

the different improved designs.

b i o s y s t em s e n g i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3302

4. Conclusion

Three concepts for improving ventilation were investigated

and assessment parameters determined (ventilation rate, air

temperature distribution, and ammonia dilution). These

concepts were tested by using CFD simulation for four

designed ventilation systems. Field experiments were con-

ducted to validate the designed cases where very low errors

were observed. In the broiler zone, the highest ventilation rate

after tunnel ventilation was in C-4 where it achieved about

54% in comparison to the standard design. All cases showed

higher uniformity ranging around 60e70% than the standard

design. The highest uniformity in air temperature distribution

was observed by C-2. All improved designs showed a thermal

suitability which maintains a required air temperature for the

broilers. The reduction in indoor ammonia concentration at

broiler zone was high with the standard design but satisfac-

tory reduction was achieved by C-4 where the reduction effi-

ciencywas 15% after 3min from turning the ventilator on. The

least satisfactory reduction efficiency appeared in C-1while C-

2 and C-3 were almost similar.

For further study, an investigation into the installation of

an aireair heat exchanger for energy recovering using C-4 is

recommended.

r e f e r e n c e s

Analytis, G. T. (2003). Implementation of the renormalizationgroup (RNG) keε turbulence model in GOTHIC/6.lb: solutionmethods and assessment. Annals of Nuclear Energy, 30,349e387.

Barrington, S. F., & MacKinnon, I. R. (1990a). Air distribution fromrectangular wooden ventilation ducts. American Society ofAgricultural Engineers, Transactions of the ASAE, 33(3), 944e948.

Barrington, S. F., & MacKinnon, I. R. (1990b). Mathematicalmodeling of ventilation duct performance. American Society ofAgricultural Engineers, Transactions of the ASAE, 33(4),1329e1335.

Bayraktar, H., Artuko�glu, M., & Altan, A. (2004). Evaluation of thepad cooling system effectiveness used in hot weatherconditions in broiler houses: Izmir case study. HayvansalUretim, 45(2), 1e9.

Blanes-Vidal, V., Guijarro, E., Balasch, S., & Torres, A. G. (2008).Application of computational fluid dynamics to the predictionof airflow in a mechanically ventilated commercial poultrybuilding. Biosystems Engineering, 100, 105e116.

Bucklin, R. A., Jacob, J. P., Mather, F. B., Leary, J. D., & Naas, I. A.(2009). Tunnel ventilation of broiler houses. This document isFACTSHEET PS-46, one of a series of the Animal ScienceDepartment, Florida Cooperative Extension Service, Instituteof Food and Agricultural Sciences. University of Florida. http://edis.ifas.ufl.edu.

Cangar, O., Aerts, J. M., Buyse, J., & Berckmans, D. (2008). Spatialdistribution of surface temperature and heat loss in broilerchickens. publication number 701P0408 Livestock environmentVIII conference (pp. 789e796). Iguassu Falls, Brazil: ASAEB.

Carpenter, G. H. (1972). The design of Permeable ducts and theirApplication to the ventilation of livestock buildings. Journal ofAgricultural Engineering Research, 17, 219e230.

Corria M. E., Naas I. A. Adapting A tunnel ventilation for highdensity broiler production - a case study. In Livestockenvironment VI: Proceedings of the 6th International Symposium(Louisville, Kentucky, USA), 2001, 461e467.

Donald, J. (2003). Principles of successful wintertime broiler houseventilation. Aviatech, 1(4).

El Moueddeb, K., Barrington, S., & Barthakur, N. (1997). Perforatedventilation ducts: part 1, a model for air flow distribution.Journal of Agricultural Engineering Research, 68, 21e27.

Elliott, H. A., & Collins, N. E. (1982). Factors affecting ammoniarelease in broiler houses. Transaction of ASAE, 25(2), 413e424.

Fluent manual. Fluent user guide2006, Version 6.2.2. Lebanon, NH,USA.

Gates, R. S., Overhults, D. G., & Zhang, S. H. (1996). Minimumventilation for modern broiler facilities. American Society ofAgricultural and Biological Engineers, 39(3), 1135e1144.

Harms, R. G., & Johnson, P. D. A. (1985). Ventilation handbook:Livestock and poultry. B.C. Canada: B.C. Ministry of Agricultureand Food Victoria, ISBN 0-7726-0372-3.

Hong, S., Lee I-, B., Hwang, H., Seo, I., Bitog, J. P., Yoo, J., et al.(2008). Numerical simulation of ventilation efficiencies ofnaturally ventilated multi-span greenhouses in Korea.American Society of Agricultural and Biological Engineers, 51(4),1417e1432.

Kennedy, D. A., Leonard, J. J., & Feddes, J. J. (1991). Field test ofa PVC plate heat exchanger for animal housing. AmericanSociety of Agricultural Engineers. Applied Engineering inAgriculture, 7(4), 457e460.

Kwon, K.-S., Lee, I.-B., Han, H.-T., Shin, C.-Y., Hwang, H.-S.,Hong, S.-W., et al. (2011). Analysing ventilation efficiency ina test chamber using age-of-air concept and CFD technology.Biosystems Engineering, 110, 421e433.

Lee, I.-B., Sase, S., & Sung, S. (2007). Evaluation of CFD accuracyfor the ventilation study of a naturally ventilated broilerhouse. Japan Agricultural Research Quarterly, 41(1), 53e64.

Lee, I.-B., Sase, S., Han, H., Hong, H., Sung, S., Hwang, H., et al.(2009). Ventilation design for a chick incubator usingcomputational fluid dynamics. Japan Agricultural ResearchQuarterly, 43(3), 227e237.

Lee, I.-B., & Short, T. H. (2000). Two-dimensional numericalsimulation of natural ventilation in a multi-span greenhouse.American Society of Agricultural and Biological Engineers, 43(3),745e753.

Liu, Z., Wang, L., Beasley, D., & Oviedo, E. (2007). Effect of moisturecontent on ammonia emissions from broiler litter:a laboratory study. Journal of Atmospheric Chemistry, 58, 41e53.

Redwine, J. S., Lacey, R. E., Mukhtar, S., & Cary, J. B. (2002).Concentration and emissions of ammonia and particulatematter in tunnel-ventilated broiler houses under summerconditions in Texas. American Society of Agricultural andBiological Engineers, 45(4), 1101e1109.

b i o s y s t em s e ng i n e e r i n g 1 1 2 ( 2 0 1 2 ) 2 9 3e3 0 3 303

Saraz, J. A. O., Damasceno, F. A., Gates, R. S., Rocha, K. S. O.,Tinoco, I. F., Marin, O. L. Z. 3D-CFD modeling of a TypicalUninsulated and internal Misting tunnel ventilated Brazilianpoultry house. In ASABE Annual International Meeting. David L.Lawrence Convention Center Pittsburgh, Pennsylvania, 2010.

Seo, I., Lee, I.-B.,Moon,O. K., Kim,H. T., Hwang, H. S., Hong, S., et al.(2009). Improvement of the ventilation system of a naturallyventilated broiler house in the cold seasonusing computationalsimulations. Biosystems Engineering, 104(1), 106e117.

Skomorucha, I., & Herbut, E. (2005). Effect of an earth tube heatexchanger on broiler house climate in the summer period, Vol. 2.Warsaw, Poland: ISAH.

SSLI. (2010). Statistical survey of livestock industry. South Korea:NAPQMS (National Agricultural Product Quality ManagementService).

Xin, H., Berry, I. L., Tabler, G. T., & Costello, T. A. (2001). Heat andmoisture production of poultry and their housing systems:broilers. Transactions of the ASAE, 44(6), 1851e1857.