Development of a Variable Water Flow Rate Control Method for the Circulation Pump in a Geothermal Heat Pump System

Shin, Ji-Hyun; Cho, Young-Hum

doi:10.3390/en11040718

Cited by 7 publications

(5 citation statements)

References 15 publications

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“…Therefore, the ground temperature can change during long-term operation because of the imbalance of cooling and heating loads [32]. Figure 2 shows the change in ground temperature during long-term operation caused by unbalanced cooling and heating loads [33]. In the case of a large imbalance between heating and cooling loads, the deterioration of the ground thermal environment because of heat accumulation in the ground occurs during long-term operation, which reduces the efficiency of the GHP.…”

Section: Hybrid Ghp Systemmentioning

confidence: 99%

“…VWF control is one of the ways to reduce the energy consumption of the GHP system [22,24]. In a system that controls the discharge pressure when the discharge flow rate changes, a flow-regulating valve can be installed at the discharge end of the pump to control it according to the flow rate to control the discharge pressure.…”

Section: Variable Water Flow Controlmentioning

confidence: 99%

“…Hybrid GHP systems need variable water flow (VWF) control to prevent energy waste caused by the supply of a constant water flow rate independent of the design maximum load [22]. Variable water flow rates for the load side and source side can be controlled in a hybrid GHP system.…”

Section: Introductionmentioning

confidence: 99%

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Variable Water Flow Control of Hybrid Geothermal Heat Pump System

Shin,

Kim,

Lee

et al. 2023

Energies

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Ground heat accumulation caused by imbalanced heating and cooling loads in a building can cause the heat-source temperature to increase as the operating age of a geothermal heat pump (GHP) system increases. An alternative system to improve upon this situation is the hybrid GHP system. This study reviews existing research on GHP systems and hybrid GHP systems, variable water flow (VWF) control, and coefficient of performance (COP) prediction. Generally, constant flow control is applied to the circulating pump to provide a flow rate according to the maximum load. The need for VWF control was identified because the hybrid GHP system is used mainly as a heating and cooling heat source system for partial loads rather than the entire building load. Previous studies on predicting the COPs of GHP systems developed prediction models by selecting input values based on mathematical models, collecting data through multiple measurement points, and utilizing data from production environments. The model can be limited by the field environment, and it is necessary to predict the COP using machine learning based on existing field monitoring data.

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Section: Hybrid Ghp Systemmentioning

confidence: 99%

Section: Variable Water Flow Controlmentioning

confidence: 99%

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Variable Water Flow Control of Hybrid Geothermal Heat Pump System

Shin,

Kim,

Lee

et al. 2023

Energies

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“…For the analysis of the differential sewage temperature within the pipe, the sewage flow rate was measured as 0.83 m/s from the South End Sewage Treatment Plant (SEWPCC) in Winnipeg and verified by standard slopes for gravity-fed sewage systems (Mihelcic & Zimmerman, 2014). The volumetric flow rate of the heat exchange fluid was 13 l/min (Shin & Cho, 2018). Table 2: Thermal properties of model materials (Bergman et al, 2007;Hafeez & Abdalla, 1972;Melinder, 2007;Zhu & Michalowski, 2005).…”

Section: Parameterizationmentioning

confidence: 99%

Evaluation of an integrated sewage pipe with ground heat exchanger for long-term efficiency estimation

et al. 2020

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Extracting heat from a sewage pipe through a typical horizontal ground heat exchanger has recently been introduced as a renewable energy alternative to reduce fossil fuel usage. This paper presents a novel design for a ground heat exchanger that extracts heat from the surrounding soil and sewage within the pipe while simultaneously being carried to a wastewater treatment plant. This research focuses on the long-term efficiency of the system under transient conditions in a cold climate. A numerical model using COMSOL Multiphysics was developed to verify the sustainability of the system for over 25 years. The model used constant inlet fluid temperatures to evaluate heat by conductive and convective heat transfer mechanisms within the pipe and surrounding soils by considering phase change of pore water. The results showed, by adopting the operation strategy proposed in this study, a maximum temperature change in the surrounding soil adjacent to the heat extraction system over 25 years was 0.10°C during the heating season in Winnipeg, Manitoba. The horizontal distance at which the heat extraction system did not show an impact on temperature change of adjacent soil was determined at 4 meters. Critical parameters in this evaluation were system depth, sewage level, and the high-density polyethylene pipe thermal properties. The sustainability of the system was not affected by the system depth due to thermal balancing between climatic, subsurface and sewage heat fluxes. Sustainable behavior was achieved at 50% and 75% of sewage pipe capacity. The effect on thermal performance from the high-density polyethylene pipe thermal properties was deemed insignificant.

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“…In a previous study, the optimal water flow rate for the maximum performance of the geothermal heat pump system was derived from the results of COP analysis according to the water flow rate and temperature difference. When the temperature difference at the geothermal side was 5 • C, the calculated water flow rate equaled the actual water flow rate, which represents the maximum performance [20]. Therefore, in this paper, the optimal temperature difference was utilized.…”

Section: Of 18mentioning

confidence: 99%

Development of Operating Method of Multi-Geothermal Heat Pump Systems Using Variable Water Flow Rate Control and a COP Prediction Model Based on ANN

2019

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As the global energy trend continues, the importance of energy savings and efficient use is being emphasized, and the installation and operation of geothermal heat pump systems is increasing. In many buildings, where an actual geothermal heat pump system has been installed, problems of efficiency deterioration occur frequently because of the inefficient operation after installation of the heat pump system. The purpose of this study was to develop and verify the operating method for energy saving and performance improvement of multiple geothermal systems. A coefficient of performance (COP) prediction model using an artificial neural network for real-time COP predictions was developed. The operating method of a multi-geothermal heat pump system using a variable water flow rate control method and COP prediction model was developed. The geothermal heat pump system operates sequentially depending on the water flow rate of the circulation pump. The COP prediction model enabled real-time performance prediction during system operation. The circulation water flow rate was reduced by up to 29% compared to the existing operating method. Approximately 23% of the energy was saved. The COP system, including the consumption power of the circulation pump, was improved.

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Development of a Variable Water Flow Rate Control Method for the Circulation Pump in a Geothermal Heat Pump System

Cited by 7 publications

References 15 publications

Variable Water Flow Control of Hybrid Geothermal Heat Pump System

Variable Water Flow Control of Hybrid Geothermal Heat Pump System

Evaluation of an integrated sewage pipe with ground heat exchanger for long-term efficiency estimation

Development of Operating Method of Multi-Geothermal Heat Pump Systems Using Variable Water Flow Rate Control and a COP Prediction Model Based on ANN

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