| Abstract |
Passive air conditioning techniques are helpful to reduce the electrical consumption of houses, offices, and buildings. Earth-Air Heat Exchangers (EAHE) are part of these techniques. These air conditioning systems consist of buried tubes through which air flows from ambient to inside of a space to be climatized. Depending on their configuration they can be horizontal or vertical. In hot climates such as the one found in Temixco, Morelos, Mexico, it is desirable that, during working hours, the air temperature reaches the temperature of thermal comfort, or close to the stabilized temperature of the ground to be able to condition interior spaces. This work shows the experimental results of three EAHE systems of vertical pipes made with PVC pipe installed in Temixco, Morelos. Each system consists in a set of three vertical heat exchangers placed in drilled wells, which have a separation of 140 cm between each of them. The first system is 2 inches tubing with a maximum depth of 290 cm, the second is 3 inches tubing with a maximum depth of 285 cm, and the third is 3 inches tubing with a maximum depth of 280 cm. Air at environmental temperature was circulated inside the EAHE tubes with the help of a centrifugal fan. The air temperature inside the exchangers was recorded with the use of thermocouples that were placed over the airflow path. Not only was temperature recorded along the airflow path, but also perpendicular to the tube, into the soil surrounding the buried tubes. In this way, it was possible to observe the thermal disturbance that occurs on the periphery of the tubes due to the circulation of air inside the heat exchangers. EAHE were operated under various controlled conditions such as airspeed, run time, and overall length of the EAHE. The centrifugal fan used to drive the air into the buried tubes is variable speed, so the air at the outlet of the exchangers had a speed of 2.2 m / s, 4.8 m / s, or 5.4 m / s depending on the diameter of the tubes and the total length of the exchanger. The air velocity at the exit of the exchangers was measured with a rotating anemometer. The duration of the experiments ranged from 2 hours to 12 days. Data collection was carried out during March, April, and May 2020. With the temperature data obtained, it was possible to observe the temperature difference (ΔT) between the inlet and outlet of the heat exchangers, the coefficient of operation (COP) of the heat exchangers was calculated during the operating hours, and it was observed the thermal impact of the soil during the circulation of air inside the tubes. Results show that it is possible to obtain a ΔT among the inlet and outlet of the EAHE higher than 9 ° C when the diameter of the tubes is 2 inches, while for heat exchangers with tubes of 3 inches diameter the ΔT is 7.3 ° C. The average temperature at the EAHE outlet during the operating periods in all cases was 26 ° C. The average COP for EAHE systems with 3 inches diameter tubes was 6.6, while the experiment where 2 inches tubes were used was 1.6. |