EARTH AIR TUNNEL COOLING SYSTEM

Pradeep Kumar Senior Fellow & Associate Director

Sustainable Habitat Division

TERI, New Delhi

Low Energy Cooling System

• Site: TERI university campus, New Delhi

• 32 rooms hostel

• Total air conditioning load: 35 TR

• System COP:2.34

Conventional design

Low Energy Cooling System

• Adaptive thermal comfort: 26~28 0 C /60~70 %

• Inside design condition: 27 0 C/65%

• Total RSH: 39909 W

• Temperature rise: 5 0 C

• Total air quantity required: 6000 lps

Earth air tunnel along with air washer & DX coil

EAT Cooling System at TERI University

EAT thermal performance in summer

DBT-41.8 C

WBT-23.6 C

DBT-28 C

WBT-20 C

DBT-21 C

WBT-20 C

DBT-22 C

WBT-20.3 C

DBT-27 C

RH-65%

AHU Room

EAT Duct AW

Conditions of air Entering & Leaving EAT

DBT-107 F

WBT-75 F

W – 79.5 Gr/lb

DBT-84 F

WBT-68 F

W – 79.5 Gr/lb

•Soil Thermo-physical properties selected: •Soil thermal conductivity = 2.0 W/m.K

•Soil density = 2000 kg/m3 •Soil specific heat = 2000 J/kg.K

EAT System Design

Earth Air Tunnel 2 Tunnel each having 3 pipes Pipe diameter: 450 mm Pipe length: 100 m

AHU System

Air Handling Unit

EAT Cooling System

Earth Air Tunnel Sizing

Pipe diameter selection

Case-1

• Diameter of pipe : 0.45 M

• Flow through pipe : 1000 lps

• Pipe velocity : 6.25 m/s

• Flow through pipe : 750 lps

• Pipe velocity : 4.7 m/s

Case-2

• Diameter of pipe : 0.6 M

• Flow through pipe : 1000 lps

• Pipe velocity : 3.57 m/s

• Flow through pipe : 750 lps

• Pipe velocity : 2.7 m/s

Pipe length selection

• L/D : 150~200

Earth Air Tunnel Simulation Results

EAT: Application of use of Geothermal Energy

• EAT is a technique in which air to soil heat exchange occurs to produce cooling in summer and pre-heating in winter.

• Two properties of underground soil: Dampening of temperature fluctuations with depth.

Phase lag between soil and ambient temperatures.

Performance Parameters

• Thermal conductivity of soil

• Pipe Diameter

• Length of tunnel

• Air velocity in pipes

Earth air tunnel outlet air temp in June

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5.0

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25.0

30.0

35.0

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45.0

50.0

12:00:00 12:30:00 13:00:00 13:30:00 14:00:00 14:30:00 15:00:00 15:30:00 16:00:00

Tem

pe

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Ambient and EAT outlet temperature variation for a typical day of June

Monitored EAT Outlet Temperature °C

Ambient Temperature °C

Earth air tunnel outlet air temp variation in July (Monsoon)

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5.0

10.0

15.0

20.0

25.0

30.0

35.0

40.0

45.0

Tem

pe

ratu

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Ambient and EAT outlet temperature variation for a typical day of July

Monitored EAT Outlet Temperature°C

Ambient Temperature °C

Thank You!!