An evaluation for spiral coil type earth-air heat exchanger at different climate conditions

ABSTRACT

The experiments have proven that the temperature level of subsoils in the summer and winter is, respectively, lower and higher than the ambient air temperature. The buried tubes in the soil can use this potential to cool or heat the ambient air. The spiral tube heat exchanger is a good choice for earth-air heat exchangers as they are buried in a fixed buried depth, and they serve higher heat transfer coefficient due to the existence of secondary flow in the cross section of tube. In this research, the spiral tube, in an earth-air heat exchanger, has been analyzed, and the performance has been evaluated in different eras and areas of use. Cities have been selected under different climatic conditions in Iran and thus the system had been simulated in both heating and cooling modes. Furthermore, the effects of various factors, such as the depth level of buried heat exchanger in soil, the velocity and the temperature of inlet air on the exhaust air temperature, as well as the thermal load absorbed by the heat exchanger, are all being investigated. Higher buried depth of the heat exchanger increases the transferred heat, while the increase in the inlet air velocity reduces the heat exchange between the soil and the air. Tabriz which is a city located in a semi-arid climate in Iran, serves the best heating and cooling loads; whereas Babolsar another city in Iran which has a humid subtropical climate, indicates the poorest performance of all in comparison to other cities and climate levels in Iran.

KEYWORDS:

• Renewable energy
• geothermal energy
• heat exchanger
• spiral tube
• heating and cooling modes

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Notes on contributors

Naghmeh Jamshidi

Naghmeh Jamshidi is an assistant professor of mechanical engineering at Payame Noor University (PNU). She graduated in Mechanical Engineering from Ferdowsi University of Mashad in 2007 and post graduated in Energy Conversion from Mazandaran University in 2009. She received her Ph.D in Mechanical Engineering from Mazandaran University in 2012. Her main research interest are computational fluid dynamics, numerical and experimental heat transfer, heat transfer enhancement techniques and turbulence phenomenon. Currently, her main research thrust is in renewable energy technology. She has co-authored more than 40 papers in journals and conference proceedings.Nasibeh Sadafi is an assistant professor at the department of art and architecture at Payame Noor University (PNU). She graduated in Architectural Engineering from Guilan University in 2005 and post graduated from University Putra Malaysia (UPM) in 2008. She earned her Ph.D in Architectural Engineering from National University of Malaysia (UKM) in 2012. Her general research interest are Sustainable Design, Flexible Design, Vernacular Architecture and Energy conservation. Her recent working papers are on Environmental & Building studies and Material Sciences.

Nasibeh Sadafi

Nasibeh Sadafi is an assistant professor at the department of art and architecture at Payame Noor University (PNU). She graduated in Architectural Engineering from Guilan University in 2005 and post graduated from University Putra Malaysia (UPM) in 2008. She earned her Ph.D in Architectural Engineering from National University of Malaysia (UKM) in 2012. Her general research interest are Sustainable Design, Flexible Design, Vernacular Architecture and Energy conservation. Her recent working papers are on Environmental & Building studies and Material Sciences.