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Group Title: Bulletin
Title: Natural ventilation in swine housing
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 Material Information
Title: Natural ventilation in swine housing
Series Title: Bulletin
Physical Description: 38 p. : ill. ; 28 cm.
Language: English
Creator: Bucklin, R. A
Florida Cooperative Extension Service
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville Fla
Publication Date: 1991
 Subjects
Subject: Swine -- Housing -- Heating and ventilation   ( lcsh )
Swine -- Housing -- Florida   ( lcsh )
Swine -- Housing -- Heating and ventilation -- Data processing   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
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Bibliography: Includes bibliographical references (p. 23-25).
Statement of Responsibility: R.A. Bucklin ... et al.
General Note: Title from cover.
General Note: "May 1991."
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Bibliographic ID: UF00008531
Volume ID: VID00001
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Holding Location: University of Florida
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Resource Identifier: ltqf - AAA6793
ltuf - AJG6227
oclc - 26898568
alephbibnum - 001753263

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Full Text


Bulletin 270


Natural Ventilation

in Swine Housing


R.A. Bucklin, I.A. Naas, F.S. Zazueta, and W.R. Walker


UNIVERSITY OF FLORIDA


MPUTE


RIES


Florida Cooperative Extension Service/Institute of Food and Agricultural Sciences
University of Florida/John T. Woeste, Dean
I


May 1991








DISCLAIMER


The Board of Regents of the State of Florida, the State of Florida, the University of
Florida, the Institute of Food and Agricultural Sciences, and the Florida Cooperative
Extension Service, hereinafter collectively referred to as "UF-IFAS," will not be liable un-
der any circumstances for direct or indirect damages incurred by any individual or entity
due to this software or the use thereof, including damages resulting from loss of data. lost
profits, loss of use, interruption of business, indirect, special incidental or consequential
damages, even if advised of the possibility of such damage. This limitation of liability will
apply regardless of the form of action, whether in contract or tort, including negligence.

UF-IFAS does not provide warranties of any kind, expressed or implied, including but not
limited to any warranty of merchantability or fitness for a particular purpose or use, or
warranty against copyright or patent infringement.

The entire risk as to the quality and performance of the program is with you. Should the
program prove defective, you assume the entire cost of all necessary servicing, repair, or
correction.

The mention of a tradename is solely for illustrative purposes. UF-IFAS does not hereby
endorse any tradename, warrant that a tradename is registered, or approve a tradename
to the exclusion of other tradenames. UF-IFAS does not give, nor does it imply, permis-
sion or license for the use of any tradename.

IF USER DOES NOT AGREE WITH THE TERMS OF THIS LIMITATION OF LIABIL-
ITY, USER SHOULD CEASE USING THIS SOFTWARE IMMEDIATELY AND RETURN
IT TO UF-IFAS. OTHERWISE, USER AGREES BY THE USE OF THIS SOFTWARE
THAT USER IS IN AGREEMENT WITH THE TERMS OF THE LIMITATION OF LI-
ABILITY.

NATURAL VENTILATION IN SWINE HOUSING
Copyright University of Florida, 1990









NATURAL VENTILATION IN SWINE HOUSING


R. A. Bucklin, I. A. Naas, F. S. Zazueta and W. R. Walker*


INTRODUCTION


This program evaluates the capacity of an open swine building to provide

an optimum thermal environment for swine production in warm, humid climates such

as Florida's. Based on inputs dealing with building size, shape, orientation

and type of construction, this software is used to evaluate the performance of

an open building by determining its total heat balance.

Swine rate of weight gain and fertility decline during the hot conditions

experienced each summer in Florida. The use of properly designed and constructed

housing can reduce or eliminate these losses. The design of naturally venti-

lated open housing used by swine producers is difficult because of the large

number of variables that enter into the design process. The use of this software

simplifies the stages of the design process that require detailed calculations.


INPUT


The input for PIGS consists of data describing the thermal and physical

characteristics of the structure being evaluated. The building characteristics

and environmental conditions required to be input are:


I. Floor type.

Floor area: Total floor area under roof, (m2).



*Associate Professor, Department of Agricultural Engineering, Institute of Food
and Agricultural Sciences, University of Florida, Gainesville 32611; Professor,
Agricultural Construction Department, Agricultural Engineering College, FEAGRI-
UNICAMP, Campinas 13081 SP Brazil; Associate Professor, Agricultural Engineering
Department and Assistant Professor, Animal Science Department, Institute of Food
and Agricultural Sciences, University of Florida, Gainesville, Florida 32611.










2

Percentage wet area: Amount of floor area kept wet expressed as a per-

centage, (%).

Insulation coeff: Thermal resistance of the floor material, (m2 C/W).


II. Wind direction: Direction of incoming dominant wind during the period

simulated expressed as degrees clockwise from north, (0).


III. Wall material.

Thermal conductance: Thermal conductance of the wall material,

(W/m2 oC).

Thickness: Wall thickness, (m).

Outside area: Total outside wall area, (m2).

Area of openings: Area of outside wall openings, (m2).


IV. Roof material.

Solar rad absorptivity: Radiation absorptivity of roof material.

Thermal conductance: Conductance of the roof material, (W/m2 oC).

Roof area: Total roof area, (m2).

Percentage shaded area: percentage of roof that is shaded, (%).

Average height: Average height of roof, (m).


V. Roof slope: Roof rise divided by run expressed as a percentage, (%).


VI. Animal.

Initial weight: Starting weight of pigs, (kg).

Average daily gain: Average daily weight gain of pigs, (kg/day).

Number of animals: Total number of animals in the house being evaluated.

Body temperature: Pig body temperature in degrees Celsius, (C).











VII. Environmental conditions.

Inside temperature: Average temperature inside the structure, (OC).

Outside temperature: Ambient temperature outside the structure, (C).

Velocity: Windspeed outside the structure, (m/s).

Radiation: Total radiation measured on a horizontal surface outside the

structure, (W/m2).


EXAMPLE RUN


PIGS is based on a menu structure as shown in Figure 1. The main menu

offers the choices of entering data, performing calculations, displaying the

current result file, ploting the information contained in the result file or

returning to DOS. If "Data Entry" is selected, the mask shown in CRT 2 is

displayed and provides options for entering the required data into PIGS. The

program contains a set of thermal characteristics for common building materials.

By using the option "Menu Selectable Items", these characteristics can be auto-

matically loaded as constants. If it is desired to use materials not listed on

the menu, constants can be entered directly from the "Enter constants" option.

In all cases, some constants such as wind direction and roof slope must be

entered using the "Enter constants" option.

"DATA ENTRY" also allows users to save a set of constants entered on the

data screen, to retrieve a previous data screen and to edit the environmental

data contained on a data screen. The last option under "DATA ENTRY" allows the

user to return to the main menu. After returning to the main menu, using the

"calculate" option creates an ASCII file containing the results. The results

contained in this file can be displayed by selecting the "Display Results" option

and can be further analyzed by importing them into spread sheet or graphics









4

software packages. The option "Plot Total Heat" produces a plot of total heat

production versus time. The computer must have CGA or better graphics capability

for the graph to be displayed.

The following is a step by step example of how to use this software to

evaluate the heat balance in swine housing. First, a file containing environmen-

tal data in column format must be prepared with each column separated by at least

one space. Record the name of this file for later use. The values used in this

example will be environmental data for May 1 to May 3, 1988 for Gainesville,

Florida. Environmental data can be stored under any legal DOS filename. Values

are entered in the order: month, day, number of pigs, outside temperature, (oC),

inside temperature, (oC), wind velocity, (m/s) and total radiation, (W/m2). The

values shown in Table 1. are stored in file "Data.pig". The structure used in

this example will be a metal roofed swine finishing building as shown in Figure

2. The building characteristics are as shown in Table 2. Building geometry is

determined by measuring the quantities shown in Figure 1 from the building to

be evaluated. The thermal characteristics for many common building materials

are contained in PIGS. Thermal characteristics for materials not listed in PIGS

can be determined by referring to handbooks such as the ASHRAE Handbook of

Fundamentals (ASHRAE, 1985) or can be determined experimentally. Environmental

data should be collected at the location of the structure. This can be done by

manually reading sensing devices or by using automatic data acquisition equip-

ment. Temperatures are obtained from sensing devices such as thermometers,

thermocouples or thermistors. Temperature sensors located outside should be

shielded from direct solar radiation. Temperature sensors located inside the

structure must be kept out of the reach of swine. The radiation level is mea-











sured using a pyranometer measuring total radiation. Wind velocity is measured

using any type of anemometer.


Table 1. Example Environmental Data.


Month Day Time Pigs Ti To Vel Rad


5 1 8.0 111 16.65 16.41 2.66 135.00

5 1 12.0 111 18.38 21.80 3.95 380.28

5 1 16.0 111 21.54 19.95 3.39 119.17

5 1 20.0 111 19.63 14.80 0.80 0.00

5 2 8.0 109 15.54 20.56 3.81 376.11

5 2 12.0 109 23.02 27.03 3.84 573.89

5 2 16.0 109 25.16 24.89 3.14 190.20

5 2 20.0 109 21.79 17.23 0.99 0.00

5 3 8.0 109 15.03 23.48 2.80 376.11

5 3 12.0 109 22.77 27.58 3.08 634.16

5 3 16.0 109 26.13 25.99 3.95 135.56

5 3 20.0 109 23.24 22.10 3.32 0.00









6

Table 2. Example Building Thermal Characteristics and Geometry.


Wall thermal conductance 1.87 W/mnoC

Wall thickness 0.20 m

Wall outside area 150.12 m2

Area of wall openings 54.17 m2

Solar radiation absorptivity of roof material 0.50

Thermal conductance of roof material 113.60 W/m2oC

Roof area 273,00 m2

Percentage shaded area 20.0 %

Average roof height 3.0 m

Floor area 126.16 m2

Percentage of floor area wet 30.00 %

Floor insulation coefficient 0.07 m2oC/W

Animal initial weight 50.00 kg

Initial number of animals 111.00

Average daily gain 0.10 kg

Animal body temperature 36.00 C


1. To run the program, place the disk that contains the PIGS.EXE file in drive

A.


2. Type PIGS . If the message "(C)olor or (M)onochrome monitor?" is

displayed, type "C" or "M" as appropriate. If the screen shown in CRT 1

is shown, the program has loaded successfully. If the message "Bad Command

or file name" is displayed, you do not have the disk with the PIGS program

in Drive A (default drive). If the program fails to load successfully on









7

a machine equipped with a monochrome monitor, delete file MONITOR.TYP and

type PIGS .


3. After a few seconds, a display as shown in CRT 2 will appear on the screen.

Select "Data Entry" and press .


4. The menu shown in CRT 3 will be displayed.


5.a.l. If the building characteristics have been previously stored under a

filename, select the option "Retrieve from Disk". The prompt, "Enter

file name (no extension)" will appear. Enter the filename without any

extension and press . For this example, enter "Data" (leave

off the extension "cfn"). The "Data Entry" menu will appear. Select

"Enter Constants" and press . The values from the file

"Data.cfn" will be displayed. If you wish to make changes in the con-

stants displayed, the data file can be modified according to the

instructions contained in Appendix II. If the constants and filenames

displayed are correct or after changes have been made press and

then, select the "Exit This Menu" option. Results and environmental

data can be stored under any legal DOS filename. For this example,

the results will be stored in a file named "Results.pig" and environ-

mental data will be stored in a file named "Data.pig".

5.b.l. If the building characteristics have not been previously entered,

select the option "Menu Selectable Items".










8

5.b.2. The "Floor Type" menu will be displayed and will list the options:

Wooden slat

Insulated asphalt

Straw being

Concrete

Enter manually

Choose the floor type from those listed or if desired select

"Enter manually". When "Enter manually is selected, the prompt "Enter

floor insulation factor (0.2-1.0):" will appear. Enter the appropriate

value of thermal resistance in m20C/W for the floor material. For this

example select "Concrete".


5.b.3. After the floor type has been selected, the "Wind direction to opening"

menu will appear listing the following options:

10-30 degrees

30-50 degrees

50-70 degrees

70-85 degrees

85-90 degrees

Enter manually

Select the appropriate value of wind direction from the ranges

listed or if desired, use the "Enter manually" option. When "Enter

manually is selected the prompt "Enter opening efficiency (0.2-0.6):"

will appear. Guidance for estimating opening efficienies can be found

in the ASHRAE Handbook of Fundamentals in the chapter dealing with

ventilation and infiltration. Enter the appropriate value. For this











example, enter the efficiency automatically by selecting "30-50

degrees".


5.b.4. After the wind direction has been selected, the "Wall Material" menu

will appear, and give the following options:

Concrete Block

Wood Plank

Plastic Curtain

Enter manually

Select the wall material from those listed or use the "Enter

manually option". If "Enter manually is selected, the prompt "Enter

thermal conductance (0.25-2.0):" will appear. Enter the appropriate

value in W/m C. For this example, select "Concrete Block".


5.b.5. After the wall material has been selected, the "Roof material menu will

appear and list the following options:

Steel sheet metal

Aluminum Sheet metal

Clay tile

Asbestos sheet

Enter manually

Select the roof material from those listed or use the "Enter

manually option". If "Steel sheet metal" or "Aluminum sheet metal"

is selected, the question "Hardboard insulation? Y/N" will appear.

Enter "Y" or "N" depending upon whether or not hardboard insulation

is used under the roofing material.










10

Selecting "Enter manually" will result in the prompt, "Enter solar

radiation absorptivity coefficient (0.4-0.9):". After the appropriate

value has been entered, the prompt, "Enter roof global thermal conduc-

tance (1-250):". Enter the appropriate value in W/m C. For this

example select "Steel sheet metal" and "N" for a steel roof with no

insulation.


5.b.6. After the roof material has been selected, the "Roof Slopes" menu will

appear and-list the options:

one slope facing west

one slope facing south

one slope facing north

two slope facing north and south

two slope facing east and west

Select the appropriate slope and press . For this ex-

ample, select "two slope facing north and south".


5.b.7. After the roof slope has been selected the, "Data Entry" menu will

again be displayed.


5.b.8. Select the "Enter constants" option and press .


5.b.9. The data entry mask shown in CRT 4 will be displayed. Selection of

the menu selectable items will result in most of the required constants

being displayed. Using the data in Table 1, enter the remaining values

in each input field. The value of "Number of Animals" is the initial

number of animals housed. Details of how to enter and edit data are

found in Appendix II. If you desire to save a file before it is









11

modified, mark the beginning and end of the file, using the block

commands and then write the block to a file following the commands

listed in Table 3 (ctrl QR, ctrl KB, ctrl QC, ctrl KK, ctrl KW). Enter

the name of the file containing the environmental data under the

heading "Environmental Data" (leave off the extension "pig"). Note

that the number of animals can be varied with time in this file. For

this example enter the file name "Data". Enter the desired file name

for the file to be used to store the program output under the heading

"Results". For this example, enter "Results.pig". Make sure that the

screen looks exactly as shown in CRT 4.1.


5.b.10. When all constants and filenames have been entered, press the

key. The "DATA ENTRY" screen shown in CRT 3 will be displayed.


5.b.ll. To save the constants into a disk file for later use, use the "Save

to Disk" option. Select "Save to Disk" and press . The prompt

"Enter filename (no extension)" will appear. Enter the desired file-

name and press . Record the name of the file you used for

future reference. For this example save the input data under file-

name "Data". A file named "DATA.CFN" will be automatically created.


5.b.12. When the constants have been entered and saved, use the "Exit This

Menu" option.


6. The cursor will be under the heading "MAIN MENU". Select "calculate" and

press . A series of numbers showing intermediate calculations will

appear at the top of the screen. When calculations are complete, an ASCII









12

file named "Results.pig" will be created that contains the results of the

analysis.


7. When calculations are complete, use the "Display Results" option. The

screen will display the results on a mask as shown in CRT 5. Values of the

solar heat, conduction heat, evaporative heat, animal heat production,

ventilation heat load and the total heat balance are displayed in column

format. Press any key and the cursor will again be under the heading "MAIN

MENU".


8. Select "Plot Total Heat". A plot of total heat versus time will be dis-

played as shown in CRT6. Press any key and the cursor will be located under

the heading "MAIN MENU".


9. If you wish to make further calculations with PIGS, use the "Data Entry"

option, press and continue as in step 3.


10. If you desire to exit PIGS, select the "Exit to DOS" option and press

.


RESULTS


The results of this program consist of values of the magnitudes of heat

sources within a swine housing. This permits the user to make design changes

using program choices such as construction materials and/or geometric design,

orientation and area of openings. Each time a parameter is changed, the overall

heat balance inside the building is simulated. A final design or modification

can be evaluated based on the total heat balance of the building. A well venti-

lated structure will have a total heat balance close to or equal to zero. The









13

structure analyzed above was poorly ventilated. Inadequate wall openings pre-

vented ventilation heat from being removed and caused a high heat balance.

PIGS can be used to investigate the effect of modifications to the structure

on its suitability for swine production. Changes that should improve the total

heat balance of the example structure would be: (1) add roof insulation, (2)

increase the area of wall openings to 50% of the total wall area, (3) increase

the percentage of wet floor to 50% of the total floor area and (4) increase the

area per animal by reducing the number of animals in the building to 50. After

entering these changes, the screen will display the information shown in CRT 7.

Analysis of the data shown in CRT 7 will yield the results shown in CRT 8 and

CRT 9. Comparison of the total heat balance of the modified structure shows a

reduction in the total heat balance of 70%. The values of heat production in

the modified building approach zero. Ideally they would equal zero, but in this

building, a large amount of heat is stored in structural materials and is not

removed by ventilation. The 70% reduction indicates that the modifications would

result in a structure that would be much more effective in providing an environ-

ment suitable for swine production than the original building.


TECHNICAL NOTES


Background


The performance of a ventilation system can be measured in two ways: 1)

by physically measuring environmental factors, or 2) by monitoring various

output criteria such as level of pollution, operator welfare and livestock health

and productivity. Experiments to determine the effects of various ventilation

systems on.air temperature and velocity at stock level were carried out by

Carpenter (1974). Findlay et al. (1948) developed a method for determining the










14

adequacy of a ventilation system based on the concentration of CO2 over that of

fresh.air in closed housing. However, most structures used for animal housing

in warm climates are open sided buildings that rely on natural ventilation for

environmental control.

The purpose of a ventilation system is to remove the water vapor and excess

heat from the building as it is produced by the animals, while maintaining a

suitable temperature inside the structure. Pattie (1973), Kelly et al. (1954),

Bond et al. (1969), Timmons and Bottcher (1981) and Beckett (1964), studied the

thermal relationships between construction materials and the ventilation of ani-

mal housing, as well as the role of radiant energy in determining heat loads.

Poor environmental conditions adversely affect production. As the environ-

mental temperature falls, growth of young pigs becomes slow, and with further

reduction in temperature, the efficiency of food conversion (weight gain per unit

of food input) is reduced (Mangold, 1967). High air temperatures also result

in reduced rate of weight gain and reduced carcass quality of pigs and may also

cause low reproductive performance (McLean, 1969).

Past modeling work on heat flow has provided a basis for modeling the animal

housing environment. A method for calculating heat gain and losses through

building sections is presented in detail in ASHRAE (1985), and is further

described by Esmay (1982).

Designing buildings to create the necessary indoor thermal environment

requires the manipulation of an extensive array of interacting variables defining

building components, materials, orientation, geometry, occupancy and animal com-

fort requirements. The large number of variables and the complexity of their

interaction have resulted in the need to make simplifying assumptions in the

thermal design process in order to develop manageable models (Buffington, 1975).









15

The application of the transmission matrix method with a simplified

procedure for its use was developed by Albright and Scott (1974). The trans-

mission matrix method relates the periodic temperature and heat flux on one side

of a homogenous layer to the periodic temperature and heat flux on the other side

of a layer by means of a transmission matrix where the temperatures are expressed

in the form of a Fourier series. The convection and radiation heat transfer

constants and the steady state conduction equation derived from Fourier's theo-

retical equation can be used to determine steady state conduction, convection

and radiation heat transfer from the structure's surfaces. The differential

equation developed by Fourier, combined with material properties data, predicts

conduction heat transfer and heat storage based on temperature differences

(Kreith, 1966). In Albright's model, the heat transfer mechanisms are required

to be linearly related to inside temperature for implementing the Fourier

solution. This approach using a controlled air volume was the starting point

in this research.

The sol-air temperature is the outside temperature that, in the absence of

all radiation heat exchange, results in the same rate of heat exchange as would

occur with the actual combination of incident solar radiation, radiant heat

exchange with surroundings, and convective heat exchange (ASHRAE, 1985).

The heat transfer can then be expressed as:


q/A he(te-ts)


Where:


he Coefficient of heat transfer by long wave radiation and convec-

tion at the outer surface, (W/m2oC)

t. = Sol-air temperature, (oC)









16

ts Surface temperature, (OC)

q/A Heat flux at a surface, (W/m2)


Assuming that the sol-air temperature is proportional to the outside temper-

ature and the heat transfer coefficient for solar radiation, another way of

expressing the heat balance and temperature is:


te to+aIg/he-eR/he

q/A aI+he(to-ts)-eR


Where:


R Difference between the radiation incident on the surface and the

radiation emitted by a black body, (W/m2)

Ig Incident solar radiation, (W/m2)

ti Inside temperature, (OC)

to Outside air temperature, (OC)

t, Surface temperature, (oC)

e Surface emittance

a Surface absorptivity


Frota et al. (1984) suggest that the surface temperature can be assumed to

be equal to the outside temperature, and then the term "he(to-t.)-eR" represents

the heat exchange by longwave radiation and convection at the outer surface.

Also the ventilation coming into the building brings in a portion of the radiant

heat load transferred from the ceiling and walls by convective heat transfer.

This makes the heat flux associated with ventilation into the building propor-

tional to the convection and thus to wind velocity. The heat flux of the air









17

leaving the building is on the other hand, proportional to the rate of air

exchange within the building.

Studies conducted by Frota et al. (1984) and Croiset (1974) show that the

total volume of air within the building changes slowly and depends on the outside

and inside air velocity. However, even when outside air velocity equals zero

the building air change remains above zero due to thermal convection and the

movement of the animals.

The ventilation heat balance was expressed as:


Qv (-Qv.Qv.)


Where:


Qve is the air flux through the openings, as stated in ASHRAE (1985)

Qv F6c(to-ti)


and


F -EAov


Where:


E efficiency of openings

F air flow through the building, (m3/s)

Ao area of openings, (m2)

Q, ventilation heat gain or loss, (W)

Qv, total heat transmitted into the building by ventilation air, (W)

Q,, total heat transmitted out of the building by ventilation air,

(W)


c = air specific heat, (J/kgoC)












6 air density, (kg/m3)

to outside temperature, (OC)

ti inside temperature, (oC)

v wind velocity, (m/s)


In this model, the opening efficiencies used were:


E 0.6, for wind directions 850 to 900 to the openings

E 0.5, for wind directions at angles from 700 to 850 to the openings

E 0.35 for wind directions at angles from 500 to 700 to the openings

E 0.30, for wind directions from 300 to 500 to the openings

E 0.25, for wind directions from 100 to 300 to the openings.


The heat removed from the building by ventilation was expressed as:


Q, CNV(ti-to)


Where:


N number of building air changes per minute,

V volume of the building, (m3)

ti inside temperature, (OC)

S experimental constant, (W/m30C)


In a previous study by Naas (1986), N for open sided housing varied from

0.1 to 1.0, depending on the wind velocity. Air exchanges were assumed as

follows: For wind velocities below 0.3 m/s, N=0.1; for wind velocities higher

than 0.3 m/s and lower than 1 m/s, N-0.3; for wind velocities higher than 1.0

m/s and lower than 2.0 m/s, N=0.4; and for air velocities higher than 2.0 m/s,

and lower than 3.0 m/s, N=0.5; and for air velocities higher than 3.0 m/s, N=1.0.









19

The solar radiation energy, Q,, was expressed by the incident solar heat load

which is proportional to the roof's area and material. The indirect solar

radiation was neglected.


Qs QopAt

Qp aRIs+Ut

U 1/[(l/h.)+(l/K)]

R U/h,


Where:


K coefficient of global heat transmission, (W/m2oC)

At area of roof exposed to incident radiation, (m2)

I, global radiation intensity, (W/m2)

Qs total solar heat, (W)

Qop quantity of radiant heat for opaque materials, (W/m2)

t temperature gradient, (oC)




The total heat gain or loss by conduction was given by Koeningsberger et

al. (1977) as:












QC tA


Where:


A area of walls, (m2)

QC total heat exchange by conduction, (W)

e thickness of construction material, (m)

y coefficient of thermal conductivity, (W/moC)


A heat production model for growing pigs was developed by Bruce and Clark

(1979) that described the total heat transfer from a pig to the environment as:


Q A([1.0+(Af/A)((I,-lf)/(Ib+If).)-(A,/A)](T,-Ta)+LIa)/(Ia+Ib)

A 0.09W0o67

Ia 1/{5.3 + 15.7(v06/W0.13))

Ib 0.02W0-33

If If45(W/45)0.33(5Af/A)nO.5

Where:

A Pig surface area, (m2)

L Animal latent heat production, (W/m2)

W Live weight, (kg)

AC Pig surface area in contact with other pigs, (m2)

Af Pig surface area in contact with the floor, (m2)

Ia Thermal resistance of air interface, (m20o/W)

Ib Tissue thermal resistance, (m2oC/W)

If Effective thermal resistance of floor, (m2oC/W)

If45 Floor insulation factor measured as described by Bruce (1977)

Ta Air temperature, (OC)









21

Tb Deep-body temperature, (oC)

Qi Animal heat production, (W)

n Number of animals


Bruce also established that for live weights from 1.0 to 170.0 kg and for

temperatures below the thermoneutral zone:


L 8.0+0.07W


The latent heat production for hot and humid conditions is given by:


L 75.6(v0o6/W0.13)[T5-Ta]


where Ts is the skin temperature. For temperatures within the thermoneutral zone,


T, 0.55ti+18


otherwise, T. Tb


The total latent heat coefficient described by Bruce (1981) for temperatures

above the upper critical temperature in wet conditions can be added to the

denominator of Ia, then:


Ia 1/{5.3+91.3(v0o6/W .13))


The total latent heat production can be expressed as:


Qe nQep+Qea

Qp LIaA/(I,+Ib)

Qea 6cvtAm


where:










22

Am Area of wet floor, (m2)

Qe Total evaporative heat exchange, (W)

Qea Total sensible heat in the building, (W)

Qep Total latent heat per pig, (W)


The heat balance for the building is then given by:


Qi+QsQc+(Q.v-Qvs)-Qe 0


Figure 3 shows the heat sources in an open swine building. The model

reflects the following parameters:


1. Buildings with open sidewalls

2. External and internal temperatures

3. Mass of air exchanged through the building

4. Conduction heat exchange

5. Solar heat absorption through the roof

6. Sensible and latent heat generated in the building.


The following parameters are neglected in the model:

1. Fermentation heat production, and the

2. Heat stored in the building construction materials


Field Measurements and Results


A short term study evaluated the thermal behavior of a swine finishing

building located at Gainesville, Florida (Latitude, 29044'N; Longitude, 82026'W).

Inside temperatures were measured using thermocouples placed at a height of about

1.3 m from the floor of the swine unit. Outside temperature, wind velocity, and

solar radiation were measured at a nearby experiment station. Air density was









23

assumed to be 1.28 kb/m3 and air specific heat was assumed to be 0.001 J/kg C

(ASHRAE, 1985). The thermal and physical characteristics were used as input for

PIGS (CRT 4.1) and analyzed as described earlier. The results are displayed in

CRT 5.

From the results shown in CRT 5, it can be concluded that: 1) the model

described and quantified the internal environment as produced by the interaction

of climate, building characteristics and housed hogs; 2) the building at Gaines-

ville showed almost no effective natural ventilation because of the small area

of side openings; 3) the corrugated steel roof material provides a high solar

heat load because of its high heat conductance. This heat load could be reduced

with roof insulation; and 3) running the model with simulated changes as

described above, the total heat balance decreased 71% and approached the ideal

case of zero.

REFERENCES



Albright, L.D. and N.R. Scott. 1974. An analysis of steady state periodic

building temperature variations in warm weather-Part I & II. Transactions

of the ASAE 17(1):88-98.

ASHRAE. 1985. Handbook of Fundamentals. American Society of Heating and

Refrigerating and Air-Conditioning Engineers, Inc., Atlanta.

Beckett, F.E. 1964. Effective temperature for evaluating or designing hog

environments. ASAE Paper No. 64-911. American Society of Agricultural

Engineers. St. Joseph, Michigan.

Bond, T.E., S.R. Morrison and R.L. Givens. 1969. Influence of surroundings on

radiant heat load of animals. Transactions of the ASAE 12(12): 246-248.










24

Bruce, J.M. 1981. Ventilation and temperature control criteria for pigs.

Chapter 12, Environmental aspects of housing for animal production. Edited

by J.A. Clark. Butterworths, Boston.

Bruce, J.M. 1977. Conductive Heat Loss From the Recumbent Animal. Farm

Building R & D Studies 8:9-15.

Buffington, D.E. 1975. Simulation models of transient energy requirements for

heating and cooling buildings. ASAE Paper No. 75-4522. American Society

of Agricultural Engineers,. St. Joseph, Michigan.

Carpenter, G.A. 1974. Ventilation of buildings for intensively housed live-

stock. Chapter 19. Heat loss from animals and man. Edited by J.L.

Monteith and L.E. Mount. Butterworths, Boston.

Croiset, M. 1972. L'hygrotermique dans le batiment. Eyrolles Edition, Paris.

376 pp.

Esmay, M.L. 1982. Principles of Animal Environment. Avi Inc. Westport.

Findlay, J.D. 1948. Experiments on ventilation of cattle barns. Journal of

Agricultural Sciences 38:411-424.

Frota, A.B., S.R. Schiffer and L.C. Chichierchio. 1984. Manual tecnico de

comfort termico. FAU/USP.

Kelly, C.F., T.E. Bond and H. Heitman. 1954. The role of thermal radiation in

animal ecology. Ecology 35:4.

Koeningsberger, 0., et al. 1977. Vivenda y edificios en zonas calidas v

tropicales. Edited by Emilio Romero Ros, Paraninfo, Madri.

Kreith, F. 1966. Principles of heat transfer. International Textbook Co.

Scranton, Pennsylvania.

McLean, J.A. 1969. The environmental needs of farm animals and their output.

Journal of JIHVE. 37. Hannah Dairy Institute. Ayr, England.









25

Mangold, D.W., T.E. Hazen and V.W. Hays. 1967. Effect of air temperature on

performance of growing-finishing swine. Transactions of the ASAE 10(3):370-

375 and 377.

Naas, I.A. 1986. Natural ventilation for agricultural animal buildings in

Brazil. ASAE Paper No. 86-5013. American Society of Agricultural

Engineers, St. Joseph, Michigan.

Pattie, D.R. 1973. Ventilation by diffusion and filtration. Proceedings of

the fourth Canadian Congress of Applied Mechanics. University of Guelph,

Canada.

Timmons, M.B. and R.W. Bottcher. 1981. Finite element thermal analysis of

livestock housing. ASAE Paper 81-4025. American Society of Agricultural

Engineers, St. Joseph, Michigan.










26

APPENDIX II

Entering Data

Data entry into this software may be done in one or more of the following

ways:



1) By menu selection



Data entry by menu selection is made by simply selecting the item

in a menu with the light bar and pressing the key. In this

form of entry, the computer will assign appropriate value/values to

the variable/variables that are determined by the menu selection. The

light bar may be moved from one item to another using the arrow keys

or by typing the first letter of the item desired. When more than one

item starts with the same letter, the lightbar will go to the closest

one.



2) Input Screen



Data entry may also be required in the form of an input screen.

In this form, a window with a mask that describes each of the entries

and a corresponding data field is displayed. Data is typed in directly

in each field. The computer will validate the data by allowing only

characters of the proper type to be entered into a field and ignoring

other characters.









27

a) A numeric field will only accept digits, a <-> sign and a <.>,

also, after the datum is entered the value is checked to insure

that it is in an expected range. If the value is out of range,

an alarm will sound and the user will be asked to verify if the

datum is correct, the user must respond appropriately.



b) A character field will accept a single character and automatically

move to the next field.



c) A string field will accept any printable ASCII character.



Data can be modified in a screen by moving to the proper field

and editing the data. Using the keypad the following functions can

be performed:


right arrow

left arrow

up arrow

down arrow

Return

Pg Up

Home

Ins

Del

End


Go to right character

Go to left character

Go to previous field

Go to next field

Go to next field

Go to right field

Go to left field

Toggle insert/overwrite mode

Delete character

Exit data screen (or return to menu)










28

3) Screen Editor



ASCII data files are created/edited using a file editing facility.

The file editor supported here includes most basic functions of a text

editor, including global search/replace, and block movement/filing. The

editor supports most of Wordstar(Tm) editing commands (use ^K^X to exit

instead of ^K^D). Table 3 contains an abbreviated list of commands.












Table 3. Using the Data Editor


Character left
Character right
Word left
Word right
Line up
Line down
Scroll up
Scroll down
Page up
Page down
Beginning of file
End of file
Beginning of line
End of line
Top of screen
Bottom of screen
Top of block
Bottom of block
Jump to marker 0..3
Set marker 0..3
Previous cursor position
New line
Insert line
Insert control character
Tab
Delete current character
Delete character left
Delete word
Delete to end of line
Delete line
Find
Find-and-replace
Find next
Begin block
End block
Copy block
Move block
Delete block
Hide block
Mark current word as block
Read block from file
Write block to file
Print block
Toggle insert mode
Toggle autoindent mode
Toggle fixed tabs
Restore line
Exit editor
Save File
Abondon File
Resize Window


Ctrl-S or Left arrow
Ctrl-D or Right arrow
Ctrl-A or Ctrl-Left arrow
Ctrl-F or Ctrl-Right arrow
Ctrl-E or Up arrow
Ctrl-X or Down arrow
Ctrl-W
Ctrl-Z
Ctrl-R or PgUp
Ctrl-C or PgDn
Ctrl-QR or Ctrl-PgUp
Ctrl-QC or Ctrl-PgDn
Ctrl-QS or Home
Ctrl-QD or End
Ctrl-QE or Ctrl-Home
Ctrl-QX or Ctrl-End
Ctrl-QB
Ctrl-QK
Ctrl-QO..Ctrl-Q3
Ctrl-K0..Ctrl-K3
Ctrl-QP
Ctrl-M
Ctrl-N
Ctrl-P
Ctrl-I or Tab
Ctrl-G or Del
Ctrl-H or Backspace
Ctrl-T
Ctrl-QY
Ctrl-Y
Ctrl-QF
Ctrl-QA
Ctrl-L
F7 or Ctrl-KB
F8 or Ctrl-KK
Ctrl-KC
Ctrl-KV
Ctrl-KY
Ctrl-KH
Ctrl-KT
Ctrl-KR
Ctrl-KW
Ctrl-KP
Ins or Ctrl-V
Ctrl-QI
Ctrl-QT
Ctrl-QL
Ctrl-KX
Ctrl-KD
Ctrl-KQ
F10











Open Data Screen: Enter Geome
Thermal and Animal Properties.
Define Environmental Data
and Results


DATA ENTRY
F Floor type
r- Wind direction to open


Figure 1. Menu Structure


Wall Floor
Thermal conductance 1.87 Floor area 126.16
Thickness 0.20 Percentage wet area 30.00
Outside area 150.12 Insulation coeff. 0.07
Area of openings 54.17
Roof Animal
Solar rad. absorptivity 0.50 Initial weight 50.00
Thermal conductance 113.60 Average daily gain 0.10
Roof area 273.00 Number of animals 50.00
Percentage shaded area 20.00 Body temperature 36.00'
Average height 3.00
Environmental data Results
Data file name: data.pig Output file name: results.pig











1.0m

12
Li5 STEEL

CONCRETE
BLOCK
I 0.2m THICK


Figure 2. Building Characteristics

































Qi = Heat produced by the pig
Os = Heat by solar radiation
Qc = Heat exchange by conduction
Qe = Heat generated by evaporation
Qve= Heat carried by ventilation to inside the building
Qvs = Heat carried by ventilation to outside the building


Figure 3. Heat Sources in an Open Swine Building








33
















Version 2.0

CRT 1. Opening Screen


Version 2.0


CRT 2. Main Menu










DATA ENTRY

Enter constants
Menu selectable items
Save to disk
Retrieve from disk
Edit data file
Exit this menu


=MAIN MENU

Data Entry
Calculate
Display Results
Plot Total Heat
Exit to DOS



au ---------


Version 2.0


CRT 3. Data Entry Menu


Range: 2.0000000000E-01 to


5.0000000000E+00


CRT 4. Data Entry Screen


Wall Floor
Thermal conductance 0.00 Floor area 0.00
Thickness 0.00 Percentage wet area 0.00
Outside area 0.00 Insulation coeff. 0.00
Area of openings 0.00


Roof Animal
Solar rad. absorptivity 0.00 Initial weight 0.00
Thermal conductance 0.00 Average daily gain 0.00
Roof area 0.00 Number of animals 0.00
Percentage shaded area 0.00 Body temperature 0.00
Average height 0.00


Environmental data Results
Data file name: NoFile Output file name: NoFile


































Range: 2.0000000000E-01 to 5.0000000000E+00


CRT 4. 1. Data Entry Screen with Original Values


Solar heat
1168.74
4903.87
1302.47
0.00
5208.04
7148.91
2078.80
0.00
5158.10
7982.51
1481.61
0.00


Conduction
-336.87
4800.39
-2231.76
-6779.49
7046.18
5628.52
-378.98
-6400.52
11860.61
6751.42
-196.51
-1600.13


HEAT LOADS
Evaporative
141.76
216.93
90.80
104.24
262.61
235.07
131.69
96.44
374.41
270.43
122.24
105.66


(Watts)
Animal
8598.43
8162.76
6604.41
6201.03
9469.28
6016.93
4928.80
5583.24
9435.26
6018.54
4606.56
5859.54


Ventilation
11.78
-335.97
156.24
142.42
-493.18
-393.95
26.53
134.43
-414.76
-472.70
13.75
112.02


Total balance
9300.32
17314.11
5740.56
-540.28
20967.71
18165.35
6523.47
-779.30
25664.80
20009.34
5783.18
4265.77


CRT 5. Results for Original Values


Wall Floor
Thermal conductance 1.87 Floor area 126.16
Thickness 0.20 Percentage wet area 30.00
Outside area 150.12 Insulation coeff. 0.07
Area of openings 54.17


Roof Animal
Solar rad. absorptivity 0.50 Initial weight 50.00
Thermal conductance 113.60 Average daily gain 0.10
Roof area 273.00 Number of animals 50.00
Percentage shaded area 20.00 Body temperature 36.00
Average height 3.00


Environmental data Results
Data file name: data.pig Output file name: results.pig




















BUILDING HEAT BALANCE

80


70


so -
50 -



4 50 -
50
D 30 -


20 -


10 -


0

-10 I I I I
8 12 18 20 8 12 18 20 8 12 18 20

TIME


CRT 6. Plot of Heat Balance for Original Values


































Range: 2.0000000000E-01 to 5.0000000000E+00


CRT 7. Data Entry Screen with Modified Values


Solar heat
10582.57
36025.43
9568.40
0.00
38259.96
52518.22
15271.55
0.00
46705.18
58642.09
10884.39
0.00


Conduction
-336.87
4800.39
-2231.76
-6779.49
7046.18
5628.52
-378.98
-6400.52
11860.61
6751.42
-196.51
-1600.13


HEAT LOADS
Evaporative
325.19
332.12
271.07
442.51
358.52
341.52
298.60
404.62
456.02
384.52
272.45
278.94


(Watts)
Animal
18978.10
18018.88
14578.21
13678.79
20528.13
13043.93
10684.35
12096.96
20452.39
13046.55
9986.55
12702.20


Ventilation
11.80
-336.30
156.36
142.52
-493.64
-394.32
26.55
134.53
-415.33
-473.06
13.77
112.11


Total balance
28910.40
58176.28
21800.15
6599.30
64982.12
70454.84
25304.88
5426.35
78146.83
77582.50
20415.74
10935.25


CRT 8. Results of Modified Values


Wall Floor
Thermal conductance 1.87 Floor area 126.16
Thickness 0.20 Percentage wet area 50.00
Outside area 150.12 Insulation coeff. 0.07
Area of openings 75.00


Roof Animal
Solar rad. absorptivity 0.50 Initial weight 50.00
Thermal conductance 1.43 Average daily gain 0.10
Roof area 273.00 Number of animals 50.00
Percentage shaded area 20.00 Body temperature 36.00
Average height 3.00


Environmental data Results
Data file name: data2.pig Output file name: results2.pig








38










BUILDING HEAT BALANCE


8 12 10 20 8 12 18
TIME

CRT 9. Plot of Heat Balance for Modified Values


20 8 12 18 20


I I I I I I




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