Analytical model for heat transfer in an underground air tunnel

Krarti, Moncef; Kreider, Jan F.

doi:10.1016/0196-8904(95)00208-1

Cited by 134 publications

(35 citation statements)

References 6 publications

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“…Without consideration of these interactions, i.e., the soil temperature at pipe location is given by Equation 15 as used in some of the previous investigations [14][15][16], the predicted heat transfer rate would be much higher because of the much higher soil temperature and hence pipe temperature and the heat transfer rate would increase with time on a daily basis because of fast decreasing air temperature and thus increasing temperature difference between soil (or pipe) and air. Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Analytical models are generally based on the simplified solution of one dimensional (axi-symmetrical) heat transfer in a circular pipe or the surrounding soil of homogeneous properties. Different forms of analytical models have been developed to predict the heat transfer through the ground heat exchanger systems [14][15][16]. However, heat and moisture transfer in shallow soil surrounding a heat exchanger is neither axi-symmetric normal to the pipe nor varying uniformly along the pipe for long term operation due to the influence of daily and seasonal climatic variations and interactions between soil and the heat exchanger.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic interactions between the ground heat exchanger and environments in earth–air tunnel ventilation of buildings

Gan

2014

Energy and Buildings

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Earth-air tunnel ventilation is an energy efficient method of preheating or cooling of supply air to a building. The purposes of this study are to investigate the performance of earth-air heat exchangers under varying soil and atmosphere conditions and the interactions between the heat exchanger and environments. A computer program has been developed for simulation of the thermal performance of an earth-air heat exchanger for preheating and cooling of supply air, taking account of dynamic variations of climatic, load and soil conditions. The program solves equations for coupled heat and moisture transfer in soil with boundary conditions for convection, radiation and evaporation/condensation that vary with the climate both at the soil top surface and inside the heat exchanger. The importance of dynamic interactions between the heat exchanger, soil and atmosphere is illustrated from the comparison of the heat transfer rates through the heat exchanger. The predicted heat transfer rate varies with operating time and decreases along the passage of air in the heat exchanger. Neglecting the interactions would significantly over-predict the heat transfer rate and the amount of over-prediction increases with operating time.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Dynamic interactions between the ground heat exchanger and environments in earth–air tunnel ventilation of buildings

Gan

2014

Energy and Buildings

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“…Studies carried out (Krarti and Kreider, 1996) on relationship between temperature variation with tube diameter and distance from the entry point indicates that the outlet temperature depends significantly upon the pipe diameter. An increase in the tube diameter results higher outlet air temperature.…”

Section: Factor Affecting Performance Of Eahe Systemmentioning

confidence: 99%

“…The study carried out by Eckert in 1976 showed by very simplistic calculations, the potential of the earth to be used as an energy source i.e., a heat sink or a heat store. The earth temperature for light dry soil at a depth of approximately 10 feet's varies by ±3 o C from the mean soil temperature, which is approximately equal to the mean annual air temperature and has a phase lag of about 75 days behind the ambient air temperature (Krarti and Kreider, 1996).…”

Section: Introductionmentioning

confidence: 99%

Design and performance evaluation of low cost Earth to air heat exchanger model suitable for small buildings in arid and semi arid regions

et al. 2014

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An experimental study was performed on a prototype model of Earth to Air Heat Exchanger System (EAHE) equipped with low cost material like PVC pipes and exhaust fans made on temporary platform. Emphasis was given on the design of the duct system suitable for small houses without any space in urban and rural areas. Tests were performed to predict the cooling potential and impact of the material on the performance of EAHE system. Experiment was performed continuously for more than three weeks and the result shows that irrespective to the inlet air temperature (ranges from 34 o C to 44 o C), outlet air temperature was recorded between 20 o C to 22 o C, which shows the effectiveness of the system. No significant affect of the material used for making the underground air pipe system was recorded on the performance of the model. The Minimum EER (W/W) ratio calculated for the prototype model was around 3.78, which is equivalent to a Energy Star 5 rating, the most efficient system. The weekly energy saving potential of the model before and after integration of EAHE was analyzed i.e., around 5 kWh/week and 20 kWh/week respectively. This considerable increase in weekly energy savings potential of model due to EAHE leads to mitigation of CO 2 emissions if implemented in the residential, commercial and industrial buildings and the corresponding annual carbon credit of these buildings can be decreased manifold. The Life Cycle Cost (LCC) analysis of model also shows that the payback period is around 3 to 4 years for the investment on EAHE system. After a series of experimental analysis the study also reveals that EAHE system is easily and economically feasible technique which can drastically reduce the consumption of energy in future and eliminate the need for conventional compressor based cooling systems.

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“…However, the use of earth as a heat source and a sink with buried pipes or under ground tunnels as a direct heat exchanger is an old concept that has existed in Persian architecture for a number of centuries (Trombe and Serres, 1994). In south Tunisia and eastern Spain (Krarti and Kreider, 1996) complete underground houses were built to cope with the relatively hot and arid climates. In northern China (Sodha et al, 1985) large houses were excavated to avoid severe cold in winter conditions.…”

Section: Introductionmentioning

confidence: 99%

Thermal modelling and experimental validation of ground temperature distribution in greenhouse

Ghosal¹,

Tiwari²,

Srivastava³

et al. 2003

Int. J. Energy Res.

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SUMMARYA periodic analysis for daily and monthly variations of ground temperature with depths is presented both under greenhouse and bare surface conditions of Delhi and for bare surface condition in other climates of India in order to design an efficient earth to air heat exchanger for greenhouse system. Calculations were carried out for a typical winter and summer day of Delhi in year 2000. Predicted values of ground temperature at 1 m depth were in fair agreement with experimental values under both conditions. Ground temperatures at various depths inside greenhouse were found to be on an average 7-98C and 3-68C higher than bare surface for daily and monthly variations respectively.

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Analytical model for heat transfer in an underground air tunnel

Cited by 134 publications

References 6 publications

Dynamic interactions between the ground heat exchanger and environments in earth–air tunnel ventilation of buildings

Dynamic interactions between the ground heat exchanger and environments in earth–air tunnel ventilation of buildings

Design and performance evaluation of low cost Earth to air heat exchanger model suitable for small buildings in arid and semi arid regions

Thermal modelling and experimental validation of ground temperature distribution in greenhouse

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