• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.4
• /
• pp.351-357
• /
• 2012

To reduce the summertime cooling load of a plant factory, a concept design was performed for the double skin window which utilizes the low temperature air from a ground coupled heat exchanger. The design parameters were selected as the number of cavity air inlet, the cavity thickness, the location of cavity air inlet, and the configuration of cavity air outlet. A parametric study was conducted in a systematic way to evaluate the heat transfer characteristics of the double skin window. As the number of cavity air inlet and the cavity thickness increase, the heat flux from outside air to indoor air was decreased. The effect of the location of cavity air inlet was not significant and the larger cavity air outlet area gave us relatively better heat blocking performance from outside hot air. This study demonstrated that it is possible to develop an improved double skin window by utilizing a ground coupled heat exchanger.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.769-775
• /
• 2008

The objective of this report is to determine the difference of thermal response that grouted two different materials, and compare the simulation result of the length of total ground heat exchanger length that using the ground thermal conductivity. And also to know heat exchange variation of ground heat exchanger temperature that measured with various test depth. The result shows that the test hole grouted with water permeable material got better thermal response than grouted with water impermeable material. However, with consideration of ingnore for the initial 12 hour data, the test hole grouted with impermeable material has larger thermal conductivity than the other. By former thermal conductivity, simulated data by engineering program shows only 3.4% difference or less. This result shows that ground thermal conductivity is not the main variables for the design program of ground heat exchanger. At the cooling or heating mode, base on the depth of -150m, the ground heat exchanger has best temperature at $-90{\sim}-60m$ and than getting worse because of entering water heat exchanged with leaving water in the same hole.

• Proceedings of the SAREK Conference
• /
• 2009.06a
• /
• pp.45-51
• /
• 2009

A ground-loop heat exchanger in a ground source heat pump system is an important unit that determines the thermal performance of a system and its initial cost. The size and performance of this heat exchanger is highly dependent on ground thermal properties. A proper design requires certain site-specific parameters, most importantly the ground effective thermal conductivity, the borehole thermal resistance and the undisturbed ground temperature. This study was performed to investigate the effect of some parameters such as borehole lengths, various grouting materials and U-tube configurations on ground effective thermal conductivity. In this study, thermal response tests were conducted using a testing device with 9-different ground-loop heat exchangers. From the experimental results, the length of ground-loop heat exchanger affects to the effective thermal conductivity. Among the various grouting materials, the bentonite-based grout with silica sand shows the largest thermal conductivity value.

• 한국신재생에너지학회:학술대회논문집
• /
• 2006.06a
• /
• pp.431-433
• /
• 2006

Accurate information on the ground surface temperature is essential for design of a borehole heat exchanger and thus ensuring the performance of a ground source heat pump system along with knowledge on thermal diffusivity and conductivity of ground. In this study we analyzed the shallow subsurface temperature monitoring data of 58 Korea Meteorological Administration synoptic stations. As a result, we compiled mean annual ground surface temperature distribution map using multiple regression analysis of the monitoring data.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.23 no.5
• /
• pp.356-364
• /
• 2011

Storage and transfer heat in soils is governed by the soil thermal properties and these properties are therefore needed in many engineering applications, including horizontal ground heat exchanger for ground-coupled heat pumps. This paper presents the evaluation results of the thermal diffusivity of soils (silica, quartzite, limestone, sandstone, granite, and two masonry soils used for the trench backfilling materials of the horizontal ground heat exchanger. To assess this thermal property, we (i) measure the soil thermal conductivities using single-probe method and (ii) use the de Vries method of summing the heat capacities of the soil constituents. The results show that the thermal diffusivity tends to increase as dry soil begins to wet, but it approaches a constant value or even decreases as the soil continues to wet. Combined algorithm with and improved model for the thermal conductivity of soils and the constituent equation provides accurate estimates of the soil thermal diffusivity.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.24 no.6
• /
• pp.487-496
• /
• 2012

Recently, utilization of building foundations as ground-coupled heat exchangers has attracted much attention because they reduce the cost and enhance the heat transfer. The objective of this study is to evaluate the performance of energy-slab ground-coupled heat exchanger installed in a commercial building. In order to demonstrate the energy transfer characteristics of the energy-slab, experiments were conducted from October 2010 to September 2011. The 1-year measurement results showed that the mean EWTs of brine returning from the energy-slab were $9.6^{\circ}C$ in heating season and $24.9^{\circ}C$ in cooling season, which were in a range of design target temperatures. In addition, the geothermal heat pump system with the energy-slab showed on-off operation according to the setting temperatures of secondary fluid in water storage tank. The results also showed that the energy-slab extracted heat of 198.6 kW from the ground and injected heat of 318.9 kW to the ground, respectively.

• Proceedings of the SAREK Conference
• /
• 2008.06a
• /
• pp.1347-1352
• /
• 2008

The SCW ground heat pump system releases ground energy from the ground water of ground heat exchanger. In other word, ground water is used to heating through releases ground energy which oneself has. But the thermal efficiency of system is going to down because repetitive process of ground water will lost ground energy in standing column well system and if heating load is continually increase, energy of ground water may be frozen or there are no benefits to use ground energy as it owes just little energy. To solve these problems, there are need to exchange water to the ground heat exchanger then the way will be used to maintain Efficiency continually as the way of to be supplied with fresh ground water into ground heat exchanger. However, this type causes waste of ground water. Therefore it is essential to discharge water to outside timely on a heat exchanger. Therefor through a study, find out the best time to discharge water to outside and exchange water to ground heat exchanger, and propose to the DB of design of the ground heat exchanger.

• 한국신재생에너지학회:학술대회논문집
• /
• 2005.06a
• /
• pp.684-687
• /
• 2005

Ground source heat pump systems are used for heating, ventilating and air-conditioning systems in commercial buildings, schools, and factories because of low operating and maintenance costs. These systems use the earth as a heat source in heating mode and a heat sink in cooling mode. Ground heat exchangers are classified by a horizontal type and vertical type according to the installation method. A horizontal type means that a heat exchanger is laid in the trench bored in 1.2 to 1.8 m depth. The solar heat and the rainwater are affected by the performance of heat exchanger and causes mutual influence among heat exchangers. In this study, to evaluate the performance of straight type, slinky type, and spiral type of horizontal ground heat exchangers designed on 1 RT scale, test sections are buried on the earth and experimental apparatus is installed. Therefore the performance of these is estimated.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.28 no.7
• /
• pp.293-298
• /
• 2016

A three-dimensional (3D) numerical model of the vertical ground-coupled heat exchanger is useful for analyzing the modern ground source heat pump system. Furthermore, a detailed description of the inner side of the exchanger allows to account for the effects of the thermal capacity. Thus, both methods are included in the proposed numerical model. For the ground portion, a FDM (Finite Difference Method) scheme has been applied using the Cartesian coordinate system. Cylindrical grids are applied for the borehole portion, and the U-tube configuration is adjusted at the grid, keeping the area and distance unchanged. Two sub-models are numerically coupled at each time-step using an iterative method for convergence. The model is validated by a reference 3D model under a continuous heat injection case. The results from a periodic heat injection input show that the proposed thermal capacity model reacts more slowly to the changes, resulting in lower borehole wall temperatures, when compared with a thermal resistance model. This implies that thermal capacity effects may be important factors for system controls.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
• /
• v.25 no.11
• /
• pp.600-605
• /
• 2013

Ground source heat pump systems (GSHP) can achieve higher performance of the system, by supplying more efficient heat source to the heat pump, than the conventional air-source heat pump system. But building clients and designers have hesitated to use GSHP systems, due to expensive initial cost, and uncertain economic feasibility. In order to reduce the initial cost, many researches have focused on the energy-pile system, using the structure of the building as a heat exchanger. Even though several experimental studies for the energy-pile system have been conducted, there was not enough data of quantitative evaluation with economic analysis and comprehensive analysis for the energy-pile. In this study, a prediction method has been developed for the energy pile system with barrette pile, using the ground heat transfer model and ground heat exchanger model. Moreover, a feasibility study for the energy pile system with barrette pile was conducted, by performance analysis and LCC assessment. As a result, it was found that the heat exchange rate of a barrette pile was 2.55 kW, and the payback period using LCC analysis was 8.8 years.