• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.13 no.1
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• pp.14-20
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• 2017

Groundwater heat pump (GWHP) system can achieve higher performance of the system by utilizing heat source of the annual constant groundwater temperature. The performance of GWHP system depends on the ground thermal environment such as groundwater temperature, groundwater flow rate and hydraulic conductivity. In this study, the geothermal environment was analyzed by using numerical simulation for develop the two-well geothermal system. As the result, this paper shows the change of the groundwater level and underground temperature around wells according to the conditions of flow rate and hydraulic conductivity.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.4
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• pp.83-92
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• 2016

The Korean government has been making efforts to use renewable energy to reduce the consumption of fossil fuels for the heating system in greenhouses. The number of greenhouses that installed a geothermal heat pump system is 201 EA with the volume of 132.8 ha and 108,467kW from 2010-2014. The geothermal system, called a shallow geothermal system, with the temperature of $10-20^{\circ}C$ has accessories composed of a BHE and heat pump. Moreover, it is necessary to have a wide area to install the BHE and to drill to the depth of 200 m. On the other hand, even though the deep geothermal system needs a high drilling cost to obtain the temperature of $40-150^{\circ}C$, the system has the advantages of the small area required for the BHE and operation without a heat pump. In this study, the temperature of the return water and heat capacity were measured to obtain the geothermal energy efficiently on the condition of the water flow being changed in the BHE. The temperature according to the return water changes through the heat conduction based on the increase of ground temperature up to the underground depth has been calculated to conduct a simulation and is compared with the field experiment test results.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.14 no.1
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• pp.1-7
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• 2018

A ground source heat pump system should be equipped with devices to measure the generated heating or cooling heat amount in Korea. Generally, the heat measuring devices have been developed to estimate consumed heat amount in residential or commercial buildings from a central air-conditioning system or a district heating system. In this study, two representive heat measuring devices used for buildings were selected, and the accuracy of them were experimentally estimated at the ground source heat pump operating conditions. The obtained heat amounts from the heat measuring devices were deviated within 4.3% comparing with the precise values calculated from an accredited test facility. Even though the accumulated heat amount values of the heat measuring devices had a small difference comparing with the precise values, the temperatures of heat measuring devices showed greatly different values comparing with the precise temperature. Therefore, it is highly recommended to develop the heat measuring devices which is appropriate for the ground source heat pump systems.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.14 no.2
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• pp.15-22
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• 2018

As heat pump application has been extending to residential, commercial, and industrial fields, the heat pump should have many operation modes. It is required to optimize refrigerant charge amount at all operation modes in order to enhance the annual performance of heat pumps. In this study, the performance analysis of the heat pump which has cooling, heating, cooling-hot water, heating-hot water, and hot water modes was executed with the variation of refrigerant charge amount. As the refrigerant charge amount changed, the maximum COPs of the heat pump at different operation modes were changed within ${\pm}10%$. Therefore, it is highly recommended to select optimum charge amount for the heat pump based on the analysis of annual load for each operation modes.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.626-629
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• 2008

In this study, a geothermal power generation system using the Kalina cycle was investigated by the simulation method. The Kalina cycle system can be used for the utilization of a low-temperature heat sources such as geothermal and industrial waste heat that are not hot enough to produce steam. The sea/river water can be considered as a cooling media. A steady-state simulation model was developed to analyze and optimize its performance. The model contains a turbine, a pump, an expansion valve and heat exchangers. The turbine and pump were modelled by an isentropic efficiency, while a condenser, an evaporator and a regenerative heat exchanger were modeled by UA-LMTD method with a counter-flow assumption. The effect of the ammonia fraction at the separator inlet on the cycle performance is investigated in detail.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.1
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• pp.31-38
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• 2015

Geothermal heat pump (GHP) systems have become an efficient alternative to conventional cooling and heating methods due to their higher energy using efficiency. These systems use the ground as a heat source in heating mode operation and a heat sink in cooling mode operation. The aim of this study is to evaluate the heating performance of the GHP system for a residential building ($420m^2$) in Ulaanbaatar, Mongolia. In order to demonstrate the feasibility of a sustainable performance of this system, we installed the water-to-water geothermal heat pump with ten vertical ground heat exchangers and measured operation parameters from October 19, 2013 to March 26, 2014. The results showed that the entering source temperature of brine from the ground heat exchangers was in a range of the design target temperature of $-10^{\circ}C$ for heating. For total values of the representative results, the ground heat exchangers extracted heat of 53.51 MWh from the ground. In addition, the GHP system supplied heat of 83.55 MWh to the building and consumed power of 30.27 MWh. Consequently, the average heating seasonal performance factor ($SPF_h$) of the overall system was evaluated to be 2.76 during the measurement period of the heating season.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.11 no.1
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• pp.15-20
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• 2015

In this study, the optimization and performance characteristics of a cascade heat pump system was analyzed with the variation of low stage refrigerant charge amount. The cascade heat pump was designed and constructed with R134a and R410A as the refrigerant for high stage and low stage cycle, respectively. Experiments were conducted by varying the low stage charge amount and the performance characteristics of the cascade heat pump were studied. The refrigerant charge amount of the low stage cycle was varied between the ranges of -15% and +10% of the optimum charge amount. The performance variation experienced in the cascade heat pump due to the variation of refrigerant charge amount shows greater effect in the undercharge regions than the overcharge regions. COP reduction in the undercharge region is larger than the decrease in the overcharge region. Some cycle variation such as power consumption and cycle pressure according to low stage refrigerant charge amount showed different trends comparing with those according to high stage refrrgerant charge amount. Therefore, the optimum charge amount of the cascade heat pump should be determined based on the experimental data obtained by the variation of high and low stage refrigerant charge amount.

• KIEAE Journal
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• v.12 no.4
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• pp.41-46
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• 2012

In Korea, Apartment houses recently occupy over 80% of all buildings. Ground source system has to be designed to consider feature of apartment house. Most apartment houses use PHC pile to get a bearing power of the soil. Therefore, the purpose of this study is to evaluate performance of ground source heat pump system utilizing energy pile under apartment. Object of experiment is low-energy experiment apartment in Song-do and Energy Pile are applied to 80%, 100% energy reduction model for heat-source. First, performance evaluation of Energy Pile geothermal system was done during summer season. As a result, The COP(coefficient of performance) about geothermal heatpump was approximately 5-6 while cooling. In winter season, Long experiment was performed because it was very important to evaluate ground condition for long time. During heating experiment, Indoor room set temperature was $20^{\circ}C$ and kept constant by heating. Coefficient of performance for heat pump and overall system was calculated. It was 3.5-4.5 for COP and 2.5-3.7 for system COP.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.1395-1400
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• 2004

A centrifugal compressor for geothermal heat pump system using R134a as working fluid has been developed. The centrifugal compressor consists of an impeller with splitters, two vaneless diffuser, a low solidity vaned diffuser and a volute. In this compressor, diffuser blade angles are controlled to satisfy both heating and cooling conditions. A aerodynamic design was done by applying the repeating design procedure including a meanline design, a 3D geometry generation and fluid dynamic calculation. In this paper, design and performance prediction results of the compressor are presented.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.10 no.3
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• pp.17-23
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• 2014

One major breakthrough in the field of heating, ventilation and air conditioning has been the development of heat pumps. Heat pump systems offer economic alternatives for recovering heat from different sources for use in various industrial, commercial and residential applications. In recent years, the heat pump has been tipped to have a very good potential for hot water production. This paper investigated the performance of a vapor injection heat pump with the variation of sub-cooler capacity at heating mode. The heating capacity of the vapor injection heat pump slightly increased with an increment of sub-cooler capacity, while COP didn't increase continuously. The 20% capacity of sub-cooler comparing with system capacity could be used as a standard to select sub-cooler capacity.