Computational Fluid Dynamic Modeling of Horizontal Air-Ground Heat Exchangers (HAGHE) for HVAC Systems

Abstract

Abstract:In order to satisfy the requirements of Directive 2010/31/EU for Zero Energy Buildings (ZEB), innovative solutions were investigated for building HVAC systems. Horizontal air-ground heat exchangers (HAGHE) offer a significant contribution in reducing energy consumption for ventilation, using the thermal energy stored underground, in order to pre-heat or pre-cool the ventilation air, in winter and summer, respectively. This is particularly interesting in applications for industrial, commercial and education buildings where keeping the indoor air quality under control is extremely important. Experimental measurements show that, throughout the year, the outside air temperature fluctuations are mitigated at sufficient ground depth (about 3 m) because of the high thermal inertia of the soil, the ground temperature is relatively constant and instead higher than that of the outside air in winter and lower in summer. The study aims to numerically investigate the behavior of HAGHE by varying the air flow rate and soil conductivity in unsteady conditions by using annual weather data of South-East Italy. The analysis shows that, in warm climates, the HAGHE brings a real advantage for only a few hours daily in winter, while it shows significant benefits in the summer for the cooling of ventilation air up to several temperature degrees, already by a short pipe. OPEN ACCESSEnergies 2014, 7 8466

Cost-optimal design for nearly zero energy office buildings located in warm climates

“…These results confirm that, for warm climate, the measures that have most influence on the reduction of primary energy are the heat pump with geothermal probes [59,60] and orientation of the panels to the south, while the walls affect the global costs. About the efficiency, the combinations with geothermal heat pump provide higher performance and lower global cost than those with airsource heat pumps.…”

“…of geothermal probes decrease the energy consumption by the good conditions of the ground temperature that facilitates the decrease of air temperature fluctuations, keeping the behavior of the heat pump stable [59]. A minimum difference of output values is found between the solutions (C-214 and C-246) that have different types of emission systems (H/C0eV0; H/C1eV1).…”

Performance Analysis of Air Cooled Heat Pump Coupled with Horizontal Air Ground Heat Exchanger in the Mediterranean Climate

“…Congedo et al [13] show that HAGHE has good performance in terms of high efficiency with a low environmental impact, operating on the ventilation air, using a pipe only 5 m long in the simulations. The geothermal heat exchanger horizontal air-to-ground (HAGHE) is a simple superficial system.…”

Horizontal Air-Ground Heat Exchanger Performance and Humidity Simulation by Computational Fluid Dynamic Analysis

“…The fundamental equations of fluid flow and heat transfer have been implemented in the analysis. The mesh, geometric modeling, physical and thermal parameters are the same as in previous research work [59]. In the present analysis, CFD simulations have been performed using a structured grid.…”

“…Compared to recent studies [59], the main focus of this work is the monitoring of the humidity level to demonstrate that, at least in the summer season, it is possible to implement the free cooling avoiding the need for post-treatment with a heat pump.…”