Operation of a Tube GAHE in Northeastern Poland in Spring and Summer—A Comparison of Real-World Data with Mathematically Modeled Data

Abstract

The article analyzes a ground-to-air heat exchanger (GAHE) for a mechanical ventilation system in a building. The heat exchanger’s performance was evaluated in northeastern Poland between May and August of 2016, 2017, and 2018. In spring and summer, the GAHE can be theoretically used to precool air for HVAC systems. The aim of the study was to compare the real-world performance of GAHE with its theoretical performance determined based on the distribution of ground temperature and the temperature at the GAHE outlet modeled in compliance with Standard PN-EN 16798-5 1:2017-07. The modeled values differed considerably from real-world data in May and June, but the model demonstrated satisfactory data fit in July and August. In all years, the modeled average monthly air temperature at the GAHE outlet was 8.3 °C below real-world values in May, but the above difference was only 1.1 °C in August. The developed mathematical model is simple and easy to use, and it can be deployed already in the preliminary design stage. It does not require expensive software or expert skills. However, this study revealed that the model has several limitations. The observed discrepancies should be taken into account when modeling the performance of a GAHE.

The Applicability of Coanda Effect Hysteresis for Designing Unsteady Ventilation Systems

“…Mechanical ventilation is increasingly popular not least because it is energy-efficient and supports heat recovery. The energy efficiency of mechanical ventilation systems can also be improved through the use of ground heat exchangers [29,30]. Well-designed and maintained mechanical ventilation systems decrease energy consumption in cooling systems [31].…”

Impact of Air Density Variation on a Simulated Earth-to-Air Heat Exchanger’s Performance

“…In the study [33] for Polish conditions, it was also concluded that the model of EN 16798-5-1 underestimated heat gain and overestimated cooling load. In [34] authors com-pared the same model and measurements and they stated that annual heating and cooling energy from the model was lower by 20-30% and greater by 8-20% than that from measurements, respectively.…”

“…The ventilation airflow rate was 300 m 3 /h. The next one [33,52] was located in northern Poland. For a residential building with a usable floor area of 115 m 2 and ventilation airflow rate of 150 m 3 /h EAHE was built from a 41 m long pipe with 0.2 m diameter buried at an average depth of 2.12 m.…”

“…In the case of a low-energy building located in Polish climatic conditions [35] EAHE reduced annual simulated heating and cooling needs by 13% and 43%, respectively. Results of long-term measurements of EAHE supplying ventilation air in a residential building located in north Poland presented in [33] showed annual savings of around 20% and 3% for heating and cooling energy, respectively.…”

“…Skotnicka-Siepsiak [33] presented measurements of ground temperature and outlet air temperature of EAHE in a residential building in Olsztyn (northern Poland) in the warm months (May, June, July and August) of 2016, 2017 and 2018. Then, they were compared in the relevant charts with results based on EN 16798-5-1.…”