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

  • Sadegh AhmadiEmail author
  • Misagh Irandoost Shahrestani
  • Shahide Sayadian
  • Mehdi Maerefat
  • Amin Haghighi Poshtiri
Article
  • 3 Downloads

Abstract

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.

Keywords

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

List of symbols

A

Annual amplitude of the ground surface temperature (°C)

Ad

Water droplet surface area (m2)

B

Buoyancy (kg m s−2)

Cd

Drag coefficient

Cpa

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

Cps

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

Cpma

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

Cpv

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

Cpw

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

D

Drag force (kg m s−2)

dd

Diameter of water droplet (m)

f

Friction factor

G

Gravity force (kg m s−2)

ha

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

hm

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

ia

Enthalpy of dry air (kJ kg−1)

ima

Enthalpy of moist air (kJ kg−1)

iv

Enthalpy of evaporation of water (kJ kg−1)

ifgw0

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

imasw

Enthalpy of saturated air (kJ kg−1)

ka

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

ks

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

Le

Lewis factor

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

Mass flow rate of air (kg s−1)

md

Mass of water droplet (kg)

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

Mass flow rate of water (kg s−1)

Nu

Nusselt number

Nd

Number of water droplets in a control volume

Pr

Prandtl number

Qs

Heat transfer from soil (W)

Q

Total heat transfer (W)

Qe

Evaporative heat transfer (W)

Qc

Convective heat transfer (W)

r1

Pipe inside radius (m)

Rtot

Overall thermal resistance (m2 K W−1)

Re

Reynolds number

T

Ground temperature (°C)

Tm

Mean annual temperature of the ground (°C)

Ta

Temperature of air (°C)

Tavg

Average temperature (°C)

Twb

Wet-bulb temperature of air (°C)

Ud

Internal energy of water droplet (J)

Ua

Velocity of air (m s−1)

Ud

Velocity of water droplets (m s−1)

X, Y, Z

Coordinate system (m)

Greek letters

τ0

Time delay (s)

αs

Thermal diffusivity of soil (m2 s−1)

ε

Cooling effectiveness

ωa

Absolute air humidity

ωsw

Absolute humidity of saturated air

ρa

Density of air (kg m−3)

ρs

Density of soil (kg m−3)

ρw

Density of water (kg m−3)

Notes

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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2020

Authors and Affiliations

  • Sadegh Ahmadi
    • 1
    • 2
    Email author
  • Misagh Irandoost Shahrestani
    • 1
  • Shahide Sayadian
    • 3
  • Mehdi Maerefat
    • 2
  • Amin Haghighi Poshtiri
    • 4
  1. 1.School of Mechanical Engineering, College of EngineeringUniversity of TehranTehranIran
  2. 2.Department of Mechanical EngineeringTarbiat Modares UniversityTehranIran
  3. 3.Mechanical Engineering DepartmentK. N. Toosi University of TechnologyTehranIran
  4. 4.Department of Mechanical EngineeringUniversity of GuilanRashtIran

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