Performance of earth-air heat exchanger in cooling, heating, and reducing carbon emissions of an industrial poultry farm: A case study

ABSTRACT

This paper aims to study an earth-air heat exchanger system proposed to cover the living environment needs and reduce energy consumption and greenhouse gas emissions of an industrial poultry house in southern Algeria. For this purpose, a detailed mathematical model was used to determine the thermal needs of this industrial building. The soil temperature was studied to estimate the appropriate depth for installing the earth-air heat exchanger, followed by a parametric and economic study to determine its dimensions and cost. Finally, compare its performance with the systems currently used in this industrial farm. The study results, which were obtained in extreme working conditions, showed that the earth air heat exchanger could cover 45% and 38% of the heating and cooling demands, respectively. In summer, the proposed heat exchanger was able to reduce the temperature from 47°C to 27.1°C, while in winter, it was able to increase the temperature from 4.8°C to 22.9°C, and its performance was stable compared to the systems currently used, and, it recorded temperatures better under hot outside conditions. Furthermore, its use reduces CO₂ emissions to 719 kg_CO2/day in heating and 2531 kg_CO2/day in cooling, making it a suitable solution for this type of industrial building.

KEYWORDS:

• Geothermal
• earth-air heat exchanger
• cooling
• heating
• renewable energy
• CO₂ emissions
• poultry houses
• heat losses
• heat gains
• soil temperature

Disclosure statement

No potential conflict of interest was reported by the author(s).

Nomenclature

A	=	Surface (m2)
Ccr	=	Residual heat corresponds to the share of energy remaining in the room %, Ccr = 1 [23].
cin	=	Overpower coefficient, Cin = 0.15 [23].
Cme	=	Coefficient of increase Cme = 1.2 [23].
Coc	=	The heat of occupants (W)
cp	=	Specific heat (W/kg.K)
cr	=	The ratio of heat losses due to the possible piping network, Cr = 0 [23].
C∆a	=	Major coefficient
C∆te	=	Increasing coefficient of gains (°C)
Dh	=	Diameter (m)
ECO2	=	CO2 emissions (kg)
Eelec	=	Consumption of electricity (kwh)
Efelec	=	The emission factor of electricity consumption (kgco2/kwh)
Effuel	=	The emission factor of fuel (kgco2/l)
Esave	=	Energy saving in (kwh)
f	=	Friction factor for smooth pipe
It,b	=	Total base radiation for the month, latitude, and orientation considered (W/m2)
It,b(40)	=	Total base radiation for July, latitude 40° north and the orientation considered (W/m2)
kl	=	Linear transmission coefficient (W/m.°C)
l	=	Internal length of the thermal bridge (m)
L	=	Tube length (m)
$\dot{m}$	=	Mass flow rate (kg/s)
mchick	=	Chicken mass (kg)
MCO2	=	CO2 mitigation (kg)
Mfuel	=	The volume of fuel consumed (l)
N	=	The hourly air renewal rate for the volume of the unheated room (h−1); N = 0.5 [23].
Nu	=	Nusselt number
P	=	Perimeter (m)
Pi	=	Perimeter of pipe (m)
Pr	=	Prandtl number
Q	=	Heating power (W)
Qelec,m	=	Gains due to machines driven by an electric motor (W)
Qlight	=	Lighting gains (W)
Qoc	=	Occupant gains (W)
qv	=	Minimum ventilation rates (m3/h)
r	=	Radius (m)
R	=	Thermal resistance (m2. °C/W)
Re	=	Reynolds number
T	=	Temperature (°C)
Tau	=	Temperature reduction coefficient
t	=	Time (day)
V	=	Volume (m3)
Weff	=	Nominal power (W)
Wn	=	Nominal wattage of bulb or fluorescent tube (W)
z	=	Depth (m)

Greeks’ symbols

${\varphi }_{HR}$	=	Gains from the various heated rooms to the unheated room (W/°C)
${\varphi }_I$	=	Internal gains (W)
${\varphi }_{Inf}$	=	Gains by air infiltration (W)
${\varphi }_{GS}$	=	Gains through a floor in contact with the soil (W)
${\varphi }_{lat}$	=	Latent heat gains (W)
${\varphi }_R$	=	Heat losses by air renewal (W/oC)
${\varphi }_{sen}$	=	Sensitive heat gains (W)
${\varphi }_{chick}$	=	Heat production of the chicken (W)
${\varphi }_t$	=	Sensitive total calorific gains (W)
${\varphi }_{UHR}$	=	Losses from the unheated room to the outside (W/°C)
∆te (t)	=	Equivalent temperature difference at time t (°C)
∆tes (t)	=	Temperature difference equivalent to hour t considering that the wall is in the shade (°C)
∆tem (t)	=	Equivalent temperature difference at time t for the orientation of the wall considered (°C)
$\nu$	=	Kinematic viscosity of air (m2/s)
$\lambda$	=	Thermal conductivity (W/m.K)
$\phi$	=	Thermal diffusivity of the soil (m2/h)
$\eta$	=	Efficiency of the motor, $\eta$ = 0.72 [23].
$\alpha$	=	Absorption factor of the wall, $\alpha$ = 0.5[23].

Subscripts

A	=	air
b	=	base
ext	=	external
int	=	internal
lat	=	Latent
m	=	medium
S	=	soil
sen	=	sensitive
tot	=	total

Abbreviations

DTR	=	Document Technique Reglementaire
EAHE	=	Earth Air Heat Exchanger
GHG	=	Green House Gas
HVAC	=	Heating, Ventilation, and Air Conditioning
EAHE	=	Earth Air Heat Exchanger