Experimental and numerical study of an earth-to-air heat exchanger for air cooling in a residential building in hot semi-arid climate

Abstract

Experimental and numerical study of an earth-to-air heat exchanger for air cooling in a residential building in hot semi-arid climate, Energy and Buildings http://dx.doi.org/10. 1016/j.enbuild.2016.04.071 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. 3 ABSTRACT This work deals with an experimental and numerical study of an Earth-to-Air Heat Exchanger (EAHX) for air cooling, connected to a residential building located in Marrakech (Morocco) which climate is a hot semi-arid one. The EAHX consists of three parallel PVC pipes of 72 m length each and 15 cm inside diameter, buried at 2.2-3.2 m depth. Each pipe is equipped with a fan, which blows treated air into the building. The experimental study consists of summer monitoring of the EAHX via measurements of air temperature and humidity throughout the exchanger, as well as at its inlet and outlet to the building for two fixed values of the airflow rate. The experimental results show that the EAHX is a good semipassive system for air refreshment, as the recorded blown air temperature into the building is quasi-constant at 25 °C with air humidity around 40%, even though the outside temperature reaches more than 40 °C. Furthermore, the reduction of daily and annual air temperature amplitudes is characterized by an exponential drop as a function of pipe length. The characteristic length is found to be around 20m and 70m respectively for the daily and annual air temperature amplitudes reduction. Moreover, it is shown that the design guidelines from literature cannot straightforwardly be applied to an EAHX which is subject to meteorological disturbance from the upper surface and/or which is not operated all year round, for which numerical simulation with a validated models remains necessary. 1 EXPERIMENTAL AND NUMERICAL STUDY OF AN EARTH-TO-AIR HEAT EXCHANGER FOR AIR COOLING INOn the other hand, dynamic simulations of the EAHX using TRNSYS software (TYPE 460) were performed with one pipe or three pipes continuously running. Good agreement was found between the simulation and experimental results. Simulation results show that the EAHX can perform a maximum drop of air temperature as high as 19.5 °C and 18.3 °C respectively for an EAHX with one and three pipes. The achieving specific cooling capacity is 58 W/m 2 (one pipe) and 55 W/m 2 (three pipes) obtained for air temperatures of 25 °C and 26 °C respectively, at the EAHX outlet and 44.6 °C at its inlet.

Performance analysis of a hybrid ventilation system in a near zero energy building

“…Khabbaz et al [ 10 ], discussed one of the renewable systems that provides better energy performance to HVAC system, which is the geothermal ground-air system. Geothermal systems can be developed by means of geothermal heat pumps, or as EAHX.…”

A study of the potential of using the Earth to air heat exchanger for cooling and heating of residential buildings in Iraq

“…Their results showed that the saturation of soil by heat restricts the performance of the EAHE system, and this can be improved by running the system on winter days. Mohamed Khabbaz et al studied numerically and experimentally the EAHE connected to a residential building located in Morocco. Their experimental results showed that EAHX is a good semipassive system for air refreshment, as the recorded blown air temperature into the building is quasi‐constant at 25°C with air humidity around 40%, even though the outside temperature reaches more than 40°C.…”

Experimental and Numerical Study of an Earth-to-Air Heat Exchanger in Northeastern Poland

“…In summer, EAHE systems cool the air that enters a ventilation unit [4]. Ground-coupled duct systems are researched extensively in countries with a subtropical climate, such as Brazil [5][6], a hot and arid climate [7], the hot and humid climate of Mexico in zones 2A and 3A [8], and in Italy [9], Turkey [10], and Egypt [11].…”