# Model development and performance evaluation of an earth air heat exchanger under a constrained urban environment

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## Abstract

An earth air heat exchanger (EAHE) is an underground heat exchanger that captures or dissipates heat to the ground and hence moderates the temperature of the air flowing through it. Though a promising energy efficient option for thermal comfort, EAHE has not diffused much in the society. One reason for its limited application is space constraint. This includes restrictions on the length and route of the EAHE pipe, positioning of the EAHE, the forced interaction between the civil foundations and the EAHE etc. In order to investigate the effectiveness of such a ‘constrained’ EAHE, an EAHE was installed under such urban constraints and its performance was measured. Simultaneously a predictive 3-dimensional numerical transient model was developed to study the impact of model parameters on the EAHE’s performance. The model was coded on the MATLAB^{Ⓒ} platform. The developed mathematical model is robust, and it was validated at sites with and without urban constraints across three climatic zones. Model predictions were in good agreement with the measured values. The data and model predictions confirmed that in a semi-arid climatic zone if a constrained EAHE is placed strategically, its performance is not compromised, and it provides the desired cooling even when it is installed at a shallower depth.

## Keywords

Earth air heat exchanger (EAHE) Urban site Transient Model## Abbreviations

- α
Albedo of the ground surface

- ɛ
Emissivity of the ground

- ɛΔR
Long wave emission from the ground

- ρ
Density (kg m

^{−3})- χ
Volume fraction

- ΔL
Length (m)

- ΔxΔyΔz
Size of the control volume

- a, b
Constants

- C
_{p,air} Specific heat of air (J kg

^{−1}K^{−1})- Cv
Volumetric heat capacity (J m

^{−3}K^{−1})- d
_{i} Inner diameter (m)

- d
_{o} Outer diameter (m)

- EAHE
Earth to air heat exchanger

- E,W,U,D,F,B
Suffixes to indicate parameter values respectively to the right, left, above, below, in front and behind of the control volume under evaluation

- f
Moisture fraction

- G
Solar global irradiance incident on the ground (Wm

^{−2})- h
_{c} Convection heat transfer coefficient (Wm

^{−1}K^{−1})- k
Thermal conductivity (Wm

^{−1}K^{−1})- NTR
Net total radiation (W m

^{−2})- r
_{a} Relative humidity of air near the ground surface

- r
_{i} Inner radius (m)

- S
_{o} Heat source (Wm

^{−3})- SDS
Standard data set

- T
Temperature in (

^{°}C)- t
Time (s)

- u
Velocity (ms

^{−1})- x,y,z
Rectangular co-ordinate axes

## Notes

### Acknowledgements

The authors would like to thank TERI School of Advanced Studies, Delhi, Landmark Design Group, Pune and Dr. VVN Kishore for their expert comments and support.

## References

- Al-Ajmi F, Loveday DL, Hanby VI (2006) The cooling potential of earth–air heat exchangers for domestic buildings in a desert climate. Build Environ 41(3):235–244Google Scholar
- Babatunde OA, Abiye OE, Sunmonu LA, Olufemi AP, Ayoola MA, Akinola OE, Ogolo EO (2017) A comparative evaluation of four evapotranspiration models based on Eddy Covariance measurement over a grass covered surface in Ile-Ife. Southwestern Nigeria Model Earth Syst Environ 3:1273Google Scholar
- Badescu V (2007) Simple and accurate model for the ground heat exchanger of a passive house. Renew Energy 32:845–855Google Scholar
- Bahnfleth WP, Pedersen CO (1990) Three-dimensional numerical study of slab-on-grade heat transfer. ASHRAE Trans pt 2:61–72Google Scholar
- Bansal V, Misra R, Agrawal GD, Mathur J (2010) Performance analysis of earth–pipe–air heat exchanger for summer cooling. Energy Build 42:645–648Google Scholar
- Benazza A, Blanco E, Aichouba M, Río JL, Laouedj S (2011) Numerical investigation of horizontal ground coupled heat exchanger. Energy Procedia 6:29–35Google Scholar
- Bharadwaj SS, Bansal NK (1981) Temperature distribution inside ground for various surface conditions. Build Environ 16:183–192Google Scholar
- Carslaw HS, Jaeger JC (1959) Conduction of heat in solids, 2nd edn. Clarendon Press, OxfordGoogle Scholar
- Chowdhury A, Das HP, Pujari AD (1991) Subsoil temperature variation and estimation of soil heat flux at Pune. Mausam 42:357–360Google Scholar
- CSE (2014) Energy and buildings. Centre for science and environment. http://www.cseindia.org/userfiles/Energy-and-%20buildings.pdf. Accessed 9 Sept 2018
- Dalampakis P, Gelegenis J, IIlias A, Ladas A, Kolios P (2017) Technical and economic assessment of geothermal soil heating systems in row covered protected crops: a case study from Greece. Appl Energy 203:201–218Google Scholar
- De Paepe M, Janssens A (2003) Thermo-hydraulic design of earth-air heat exchangers. Energy Build 35(4):389–397Google Scholar
- Di Silvestre ML, Favuzza S, Sanseverino ER, Zizzo G (2018) How decarbonization, digitalization and decentralization are changing key power infrastructures. Renew Sustain Energy Rev 93:483–498Google Scholar
- Dolschak K, Gartner K, Berger TW, Model (2015) A new approach to predict soil temperature under vegetated surfaces. Earth Syst Environ Modeling Earth Systems and Environment 1:32Google Scholar
- ECBC (2017) Bureau of energy efficiency. https://beeindia.gov.in/sites/default/files/BEE_ECBC%202017.pdf Accessed 20 July 2018
- Efthimiou N (2018) The importance of soil data availability on erosion modeling”. CATENA 165:551–566Google Scholar
- Eppelbaum L, Kutasov I, Pilchin A (2014) Thermal properties of rocks and density of fluids. In: Applied geothermics. lecture notes in earth system sciences. Springer, BerlinGoogle Scholar
- Farouki OT (1981) Thermal properties of soils (No. CRREL-MONO-81-1). Cold Regions Research and Engineering LabGoogle Scholar
- Gan G (2014) Dynamic interactions between the ground heat exchanger and environments in earth–air tunnel ventilation of buildings. Energy Build 85:12–22Google Scholar
- Ghosal MK, Tiwari GN, Srivastava NSL, Sodha MS (2004) Thermal modelling and experimental validation of ground temperature distribution in greenhouse. Int J Energy Res 28(1):45–63Google Scholar
- Hollmuller P (2003) Analytical characterisation of amplitude-dampening and phase-shifting in air/soil heat-exchangers. Int J Heat Mass Transf 46(22):4303–4317Google Scholar
- Jacovides CP, Mihalakakou G (1995) An underground pipe system as an energy source for cooling/heating purpose. Renewable Energy 6(8):893–900Google Scholar
- Kadaverugu R (2015) Framework for mathematical modeling of Soil-Tree system. Model Earth Syst Environ 1:17Google Scholar
- Khatry AK, Sodha MS, Malik MAS (1978) Periodic variation of ground temperature with depth. Sol Energy 20:425–427Google Scholar
- Kottek M, Grieser J, Beck C, Rudolf B, Rubel F (2006) World map of Köppen Geiger climate classification updated. Meteorol 15:259–263Google Scholar
- Lee KH, Strand RK (2008) The cooling and heating potential of an earth tube system in buildings. Energy Build 40:486–494Google Scholar
- Mathur A, Srivastava A, Mathur J, Mathur S, Agrawal GD (2015) Transient effect of soil thermal diffusivity on performance of EAHE system. Energy Rep 1:17–21Google Scholar
- Mihalakakou G, Santamouris M, Asimakopoulos D (1994) On the cooling potential of earth to air heat exchangers. Energy Convers Manag 35:395–402Google Scholar
- Misra R, Bansal V, Agarwal GD, Mathur J, Aseri T (2012) Thermal performance investigation of hybrid earth air tunnel heat exchanger. Energy Build 49:531–535Google Scholar
- Niu F, Yu Y, Yu D, Li H (2015) Investigation on soil thermal saturation and recovery of an earth to air heat exchanger under different operation strategies. Appl Therm Eng 77:90–100Google Scholar
- Patankar S (1980) Numerical heat transfer and fluid flow. CRC Press, USAGoogle Scholar
- Peel MC, Finlayson BL, McMahon TA (2007) Updated world map of the Köppen-Geiger climate classification. Hydrol Earth Syst Sci Dis 4(2):439–473Google Scholar
- Peretti C, Zarrella A, De Carli M, Zecchin R (2013) The design and environmental evaluation of earth-to-air heat exchangers (EAHE). A literature review. Renew Sustain Energy Rev 28:107–116Google Scholar
- Rastogi A, Choi J, Hong T, Lee M (2017) Impact of different LEED versions for green building certification and energy efficiency rating system: a multifamily midrise case study. Appl Energy 205(1):732–740Google Scholar
- Rees SW, Adjali MH, Zhou Z, Davies M, Thomas HR (2000) Ground heat transfer effects on the thermal performance of earth-contact structures. Renew Sustain Energy Rev 4(3):213–265Google Scholar
- Russo S, Sillmann J, Fischer EM (2015) Top ten European heatwaves since 1950 and their occurrence in the coming decades. Environ Res Lett 10Google Scholar
- Santamouris M, Kolokotsa D (2013) Passive cooling dissipation techniques for buildings and other structures: the state of the art. Energy Build 57:74–94Google Scholar
- Sawhney RL, Mahajan U (1994) Heating and cooling potential of an underground air-pipe system. Int J Energy Res 18(5):509–524Google Scholar
- Sehli A, Hasni A, Tamali M (2012) The potential of earth–air heat exchangers for low energy cooling of buildings in South Algeria. Energy Procedia 18:496–506Google Scholar
- Selamat S, Miyara A, Kariya K (2016) Numerical study of horizontal ground heat exchangers for design optimization. Renewable Energy 95:561–573Google Scholar
- Shukla A, Tiwari GN, Sodha MS (2006) Parametric and experimental study on thermal performance of an earth–air heat exchanger. Int J Energy Res 30(6):365–379Google Scholar
- Singh R, Sawhney RL, Lazarus IJ, Kishore VVN (2018) Recent advancements in earth air tunnel heat exchanger (EATHE) system for indoor thermal comfort application: a review. Renew Sustain Energy Rev 82:2162–2185Google Scholar
- Sodha MS, Sharma AK, Singh SP, Bansal NK, Kumar A (1985) Evaluation of an earth—air tunnel system for cooling/heating of a hospital complex. Build Environ 20(2):115–122Google Scholar
- Su H, Liu XB, Ji L, Mu JY (2012) A numerical model of a deeply buried air–earth–tunnel heat exchanger. Energy Build 48:233–239Google Scholar
- Thanu NM, Sawhney RL, Khare RN, Buddhi D (2001) An experimental study of the thermal performance of an earth-air-pipe system in single pass mode. Sol Energy 71:353–364Google Scholar
- Thiers S, Peuportier B (2008) Thermal and environmental assessment of a passive building equipped with an earth-to-air heat exchanger in France. Sol Energy 82(9):820–831Google Scholar
- Tyagi AP (2009) Solar radiant energy over India. Indian meteorological department. http://www.mnre.gov.in/file-manager/UserFiles/solar_radiant_energy_over_India.pdf. Accessed 20 Jul 2018
- Vaz J, Sattler MA, dos Santos ED, Isoldi LA (2011) Experimental and numerical analysis of an earth–air heat exchanger. Energy Build 43(9):2476–2482Google Scholar
- Wang Y, Kuckelkorn J, Zhao FY, Spliethoff H, Lang W (2017) A state of art of review on interactions between energy performance and indoor environment quality in Passive House buildings. Renew Sustain Energy Rev (72): 1303–1319Google Scholar
- Wu H, Wang S, Zhu D (2007) Modelling and evaluation of cooling capacity of earth–air–pipe systems. Energy Convers Manag 48:1462–1471Google Scholar