scholarly journals THE OPTIMAL PARAMETERS TECHNIQUE FOR THE VERTICAL GROUND HEAT EXCHANGERS OF THE GEOTHERMAL HEAT PUMP SYSTEMS

2020 ◽  
Vol 8 (3) ◽  
pp. 113-124
Author(s):  
B. A. Semenov ◽  
◽  
D. S. Saponenko ◽  
Keyword(s):  
Heat Pump ◽  
Heat Exchangers ◽  
Net Present Value ◽  
Optimal Parameters ◽  
Present Value ◽  
Geothermal Heat ◽  
Ground Heat Exchangers ◽  
Geothermal Heat Pump ◽  
Vertical Ground

Представлена научно обоснованная методика определения оптимальных параметров вертикальных теплообменников грунтового контура геотермальной теплонасосоной установки по условию достижения максимума интегрального эффекта или чисто дисконтированного дохода (Net Present Value). Расчетами подтверждено, что максимальная экономическая эффективность вертикальных теплообменников грунтового контура может достигаться при соблюдении оптимальных значений двух определяющих параметров: общей длины U-образной тепловоспринимающей трубы и расхода проходящего по ней теплоносителя. Оптимальные значения этих параметров рассчитываются в зависимости от вида и температуры грунта, диаметра и марки полиэтиленовых труб, начальной температуры теплоносителя на входе, тарифов на теплоту и электроэнергию, удельных капитальных вложений во все элементы грунтового зонда, включая земляные работы, с учетом реальной нормы дисконта и ряда дополнительных исходных данных. Методика позволяет при различных климатических условиях и типах грунта определять оптимальные конструктивные и режимные параметры вертикальных грунтовых теплообменников и количественно оценивать максимально достижимую экономическую эффективность использования грунтовых контуров с вертикальными U-образными зондами для отбора низкопотенциальной теплоты грунта...

scholarly journals The energy source for heat pumps with vertical heat exchangers

2018 ◽  
Vol 44 ◽  
pp. 00157
Author(s):  
Piotr Rynkowski
Keyword(s):  
Heat Pump ◽  
Heat Exchangers ◽  
Electricity Consumption ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Temperature Analysis ◽  
Heat Flows ◽  
Ground Heat Exchangers ◽  
Vertical Heat ◽  
Vertical Ground

The paper presents the ground temperature analysis, heat flows and energy transferred from the soil massif by the vertical ground heat exchangers (VGHE). Three cases – with one, two and three vertical heat exchangers were compared. Their influences on the soil massif temperature in the heat exchangers area were shown. The mass flow and the temperature at the inlet and outlet side of the heat pump were measured in each circuit. Additional, the electricity consumption by the heat pump and energy supply to buffer vessel were measured. Finally, the Coefficient of Performance (COP) as a function of length of VGHE is shown for selected interval time.

scholarly journals Simulation Analysis on the Heat Performance of Deep Borehole Heat Exchangers in Medium-Depth Geothermal Heat Pump Systems

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 754 ◽  
Author(s):  
Jiewen Deng ◽  
Qingpeng Wei ◽  
Shi He ◽  
Mei Liang ◽  
Hui Zhang
Keyword(s):  
Heat Transfer ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Geothermal Energy ◽  
Heat Transfer Performance ◽  
Deep Borehole ◽  
Geothermal Heat ◽  
Temperature Heat ◽  
Geothermal Heat Pump ◽  
Borehole Heat Exchangers

Deep borehole heat exchangers (DBHEs) extract heat from the medium-depth geothermal energy with the depth of 2–3 km and provide high-temperature heat source for the medium-depth geothermal heat pump systems (MD-GHPs). This paper focuses on the heat transfer performance of DBHEs, where field tests and simulation are conducted to analyze the heat transfer process and the influence factors. Results identify that the heat transfer performance is greatly influenced by geothermal properties of the ground, thermal properties and depth of DBHEs and operation parameters, which could be classified into external factors, internal factors and synergic adjustment. In addition, the long-term operation effects are analyzed with the simulation, results show that with inlet water temperature setting at 20 °C and flow rate setting at 6.0 kg/s, the average outlet water temperature only drops 0.99 °C and the average heat extraction drops 9.5% after 20-years operation. Therefore, it demonstrates that the medium-depth geothermal energy can serve as the high-temperature heat source for heat pump systems stably and reliably. The results from this study can be potentially used to guide the system design and optimization of DBHEs.

scholarly journals Sustainability, climate resiliency, and mitigation capacity of geothermal heat pump systems in cold regions

2020 ◽  
Author(s):  
Ali Fatolahzadeh Gheysari ◽  
Hartmut Hollaender ◽  
Pooneh Maghoul ◽  
Ahmed Shalaby
Keyword(s):  
Finite Element ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Ground Surface ◽  
Geothermal Heat ◽  
Cold Regions ◽  
Thermal Output ◽  
Operation Modes ◽  
Geothermal Heat Pump

Geothermal heat pump (GHP) systems have recently gained popularity in providing heat to buildings. In this study, the short-term and long-term performance of closed-loop horizontal GHP systems in cold regions and the effectiveness of seasonal balancing were investigated. A period of 50 years was simulated to cover the life of a conventional system. A repeating block of heat exchangers at three depths was modelled in a series of 3D multi-physics finite element simulations. Two operation modes were defined, representing the non-balanced mode and the seasonal balancing through the injection of lake water in summer. The climate conditions at the ground surface were explicitly modelled by defining a temperature boundary condition. A novel AI framework was developed to generate the projections of ground surface temperatures from air temperature and other atmospheric variables. An artificial neural network was trained using the air and ground temperature measurements at the nearby weather station. Several training approaches were compared to minimize prediction errors. The model was then used to convert the air temperatures from downscaled outputs of the CanESM2 climate model into surface temperatures. Finite element models, representing the two operation modes under three climate change scenarios and various heat exchanger spacing, were simulated and verified by comparing the resulting ground temperatures with the local measurements. The outputs were processed into extraction power, thermal output, and carbon emissions. Results suggest that in order to attain a stable heat extraction throughout a year, heat exchangers should be placed at depths that are not affected by seasonal variations of surface conditions. Simulations revealed thermal depletion and its inverse correlation with heat exchanger spacing. The seasonal balancing operation approach showed enhancement in total thermal output by 55%. The system was found to be resilient when subjected to the major climate pathways. In a rough estimate based on the average carbon footprint of electricity production in Canada, a system with 100 heat exchangers was found to save up to 800 tons and 1300 tons of equivalent CO2 emissions over its life, under the non-balanced and balanced operation modes, respectively.

scholarly journals What Is the Main Difference between Medium-Depth Geothermal Heat Pump Systems and Conventional Shallow-Depth Geothermal Heat Pump Systems? Field Tests and Comparative Study

2019 ◽  
Vol 9 (23) ◽  
pp. 5120 ◽  
Author(s):  
Jiewen Deng ◽  
Qingpeng Wei ◽  
Shi He ◽  
Mei Liang ◽  
Hui Zhang
Keyword(s):  
Heat Pump ◽  
Heat Exchangers ◽  
Field Tests ◽  
Energy Performance ◽  
Heat Pumps ◽  
Geothermal Heat ◽  
Temperature Heat ◽  
Geothermal Heat Pump ◽  
Water Pumps ◽  
Whole Systems

Recently, the medium-depth geothermal heat pump systems (MD-GHPs) have been applied for space heating in China. Theoretically, the MD-GHPs use deep borehole heat exchangers (DBHEs) to extract heat from the medium-depth geothermal energy with the depth of 2~3 km, thus, improving the energy performance of whole systems obviously. This paper conducts field tests of nine conventional shallow-depth geothermal heat pump systems (SD-GHPs) and eight MD-GHPs to analyze the energy performance of heat pump systems, as well as heat transfer performance of ground heat exchangers. Then the comparative studies are carried out to analyze the difference between these two ground coupled heat pump systems. Field test results show that the outlet water temperature of DBHEs in MD-GHP can reach more than 30 °C with heat extraction of 195.2 kW~302.8 kW per DBHE with a depth of 2500 m, which are much higher than that of SD-GHPs. However, the heat pumps and water pumps in the ground side should be specially designed to fit the high-temperature heat source instead of following operation mode of SD-GHPs. Then with variable speed compressor which has high energy efficiency under a wide range of load rate and compressor ratio, and with the ground-side water pumps which efficiently operate under high water resistance and low flow rate, the COP of heat pumps and COPs of whole systems could reach 7.80 and 6.46 separately. Thus, the advantage of high-temperature heat source could be fully utilized to achieve great energy-saving effects.

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