Abstract
The energy slab is a novel type of horizontal Ground Heat Exchanger (GHEX), where heat exchange pipes are encased in building slab structures. The thermal performance of energy slabs is usually inferior to the conventional closed-loop vertical GHEX because its installation depth is relatively shallow and therefore affected by ambient air temperature. In this paper, heat exchange pipes were made of not only conventional high-density polyethylene (HDPE), but also stainless steel (STS), which is expected to enhance the thermal performance of the energy slabs. In addition to a floor slab, a side wall slab was also used as a component of energy slabs to maximize the use of geothermal energy that can be generated from the underground space. Moreover, a thermal insulation layer in the energy slabs was considered in order to reduce thermal interference induced by ambient air temperature. Consequently, two different field-scale energy slabs (i.e., floor-type and wall-type energy slabs) were constructed in a test bed, and two types of heat exchange pipes (i.e., STS pipe and HDPE pipes) were installed in each energy slab. A series of thermal response tests (TRTs) and thermal performance tests (TPTs) were conducted to evaluate the heat exchange performance of the constructed energy slabs. Use of the STS heat exchange pipe enhanced the thermal performance of energy slabs. Additionally, the wall-type energy slab had a similar thermal performance to the floor-type energy slab, which infers the applicability of the additional use of the wall-type energy slab. Note that if an energy slab is not thermally cut off from the building’s interior space with the aid of thermal insulation layers, heat exchange within the energy slabs should be significantly influenced by fluctuations in ambient temperature.
Highlights
The Ground Source Heat Pump (GSHP) is a heating and cooling system that is usually coupled with the Ground Heat Exchanger (GHEX) to utilize geothermal energy
If energy slabs are installed in a building along with conventional GHEXs, the construction cost can be economized by reducing the length of boring depth and the number of GHEXs
In-Situ Thermal Performance Tests (TPTs) the effective thermal conductivity of the ground, it cannot evaluate the actual thermal performance mentioned in Section the thermal response tests (TRTs) to cannot be directly applied to energy slabs withofthe of GHEXs
Summary
The Ground Source Heat Pump (GSHP) is a heating and cooling system that is usually coupled with the Ground Heat Exchanger (GHEX) to utilize geothermal energy. Lee et al (2012) and Zhang et al (2014) conducted experimental studies on an energy textile with various arrangements [2,3], and compared the thermal performance indirectly with the conventional closed-loop vertical GHEX [2]. If energy slabs are installed in a building along with conventional GHEXs, the construction cost can be economized by reducing the length of boring depth and the number of GHEXs. to the best of our knowledge, no comprehensive experimental studies have been conducted for enhancing the thermal performance of energy slabs or evaluating the effect of system parameters. An energy slab is usually installed in the basement floor of buildings because such an underground environment may enhance their thermal performance, along with a relatively constant temperature throughout the year and the high thermal conductivity of ground formations. Thermal performance tests (TPTs) were performed to evaluate the thermal performance of the energy slabs
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