Performance analysis of an integrated cooling system consisted of earth-to-air heat exchanger (EAHE) and water spray channel


This study evaluates the cooling performance of a new hybrid system composing of an earth-to-air heat exchanger (EAHE) and a water spray channel to provide thermal comfort in Tehran, Iran. The inlet air temperature passing through the EAHE dissipates its heat to the surrounding soil and become slightly colder. To reach thermal comfort, the pre-cooled air flows upward through a channel spraying water downward and enters the living space. Considering the evaporative thermal comfort zone, the results showed that this system can meet comfort conditions for summer season Tehran. Moreover, according to the results, the cooling effectiveness of the proposed hybrid system is more than 100%, which means that the integrated system is capable of decreasing the air dry-bulb temperature below the inlet ambient wet-bulb temperature. Employing ground as a reliable source of alternative energy, the proposed cooling system can be considered an eco-friendly and energy-efficient system. Therefore, the introduced cooling system can be utilized as an alternative to conventional evaporative coolers or mechanical vapor compression systems while it can be considered an eco-friendly and energy-efficient system.

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A :

Annual amplitude of the ground surface temperature (°C)

A d :

Water droplet surface area (m2)

B :

Buoyancy (kg m s−2)

C d :

Drag coefficient

C pa :

Specific heat capacity of dry air (J kg−1 K−1)

C ps :

Specific heat capacity of soil (J kg−1 K−1)

C pma :

Specific heat capacity of moist air (J kg−1 K−1)

C pv :

Specific heat capacity of water vapor (J kg−1 K−1)

C pw :

Specific heat capacity of water (J kg−1 K−1)

D :

Drag force (kg m s−2)

d d :

Diameter of water droplet (m)

f :

Friction factor

G :

Gravity force (kg m s−2)

h a :

Heat transfer coefficient of air (W m−2 K−1)

h m :

Mass transfer coefficient (kg m−3 s−1)

i a :

Enthalpy of dry air (kJ kg−1)

i ma :

Enthalpy of moist air (kJ kg−1)

i v :

Enthalpy of evaporation of water (kJ kg−1)

i fgw0 :

Enthalpy of evaporation of water at 0 °C (kJ kg−1)

i masw :

Enthalpy of saturated air (kJ kg−1)

k a :

Thermal conductivity of air (W m−1 K−1)

k s :

Thermal conductivity of soil (W m−1 K−1)


Lewis factor

\(\dot{m}_{\text{a}}\) :

Mass flow rate of air (kg s−1)

m d :

Mass of water droplet (kg)

\(\dot{m}_{\text{w}}\) :

Mass flow rate of water (kg s−1)


Nusselt number

N d :

Number of water droplets in a control volume


Prandtl number

Q s :

Heat transfer from soil (W)

Q :

Total heat transfer (W)

Q e :

Evaporative heat transfer (W)

Q c :

Convective heat transfer (W)

r 1 :

Pipe inside radius (m)

R tot :

Overall thermal resistance (m2 K W−1)


Reynolds number

T :

Ground temperature (°C)

T m :

Mean annual temperature of the ground (°C)

T a :

Temperature of air (°C)

T avg :

Average temperature (°C)

T wb :

Wet-bulb temperature of air (°C)

U d :

Internal energy of water droplet (J)

U a :

Velocity of air (m s−1)

U d :

Velocity of water droplets (m s−1)

X, Y, Z :

Coordinate system (m)

τ 0 :

Time delay (s)

α s :

Thermal diffusivity of soil (m2 s−1)

ε :

Cooling effectiveness

ω a :

Absolute air humidity

ω sw :

Absolute humidity of saturated air

ρ a :

Density of air (kg m−3)

ρ s :

Density of soil (kg m−3)

ρ w :

Density of water (kg m−3)


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Correspondence to Sadegh Ahmadi.

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Ahmadi, S., Irandoost Shahrestani, M., Sayadian, S. et al. Performance analysis of an integrated cooling system consisted of earth-to-air heat exchanger (EAHE) and water spray channel. J Therm Anal Calorim 143, 473–483 (2021).

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  • Earth-to-air heat exchanger (EAHE)
  • Performance evaluation
  • Water spray channel
  • Hybrid cooling system
  • Thermal comfort