scholarly journals Low-Temperature Enhanced Geothermal System using Carbon Dioxide as the Heat-Transfer Fluid

2014 ◽  
Author(s):  
Alan D. Eastman ◽  
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Low Temperature ◽  
Heat Transfer Fluid ◽  
Geothermal System ◽  
Enhanced Geothermal System

scholarly journals Analysis and Comparison of Some Low-Temperature Heat Sources for Heat Pumps

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1853 ◽  
Author(s):  
Pavel Neuberger ◽  
Radomír Adamovský
Keyword(s):  
Heat Transfer ◽  
Low Temperature ◽  
Heat Source ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Ambient Air ◽  
Heat Transfer Fluid ◽  
Heat Sources ◽  
Ground Heat Exchangers ◽  
Temperature Heat

The efficiency of a heat pump energy system is significantly influenced by its low-temperature heat source. This paper presents the results of operational monitoring, analysis and comparison of heat transfer fluid temperatures, outputs and extracted energies at the most widely used low temperature heat sources within 218 days of a heating period. The monitoring involved horizontal ground heat exchangers (HGHEs) of linear and Slinky type, vertical ground heat exchangers (VGHEs) with single and double U-tube exchanger as well as the ambient air. The results of the verification indicated that it was not possible to specify clearly the most advantageous low-temperature heat source that meets the requirements of the efficiency of the heat pump operation. The highest average heat transfer fluid temperatures were achieved at linear HGHE (8.13 ± 4.50 °C) and double U-tube VGHE (8.13 ± 3.12 °C). The highest average specific heat output 59.97 ± 41.80 W/m2 and specific energy extracted from the ground mass 2723.40 ± 1785.58 kJ/m2·day were recorded at single U-tube VGHE. The lowest thermal resistance value of 0.07 K·m2/W, specifying the efficiency of the heat transfer process between the ground mass and the heat transfer fluid, was monitored at linear HGHE. The use of ambient air as a low-temperature heat pump source was considered to be the least advantageous in terms of its temperature parameters.

scholarly journals Analysis of Heat Transfer Mechanism for Shelf Vacuum Freeze-Drying Equipment

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
Hong-Ping Cheng ◽  
Shian-Min Tsai ◽  
Chin-Chi Cheng
Keyword(s):  
Heat Transfer ◽  
Heat Exchange ◽  
Low Temperature ◽  
Temperature Gradient ◽  
Freeze Drying ◽  
Heat Transfer Fluid ◽  
Processing Temperature ◽  
Fluid Temperature ◽  
Three Dimension ◽  
Flow Rates

Vacuum freeze-drying technology is applicable to the process of high heat-sensitive products. Due to the long drying period and extremely low processing temperature and pressure, the uniform and efficiency of heat transfer fluid temperature in shelf are critical for product quality. Therefore, in this study, the commercial computer fluid dynamics (CFD) software, FLUENT, was utilized for three-dimension numerical simulation of the shelf vacuum freeze-drying process. The influences of different inlet and outlet positions for shelves on the uniformity of the flow rate and temperature were discussed. Moreover, it explored the impacts on the temperature gradient of shelves after heat exchange of different flow rates and low temperature materials. In order to reduce the developing time and optimize the design, the various secondary refrigerants in different plies of shelves were investigated. According to the effect of heat exchange between different flow rates and low temperature layer material shelves on the temperature gradient of shelves surface, the minimum temperature gradient was 20 L/min, and the maximum was 2.5 L/min.

scholarly journals Progress on Heat Transfer in Fractures of Hot Dry Rock Enhanced Geothermal System

2021 ◽  
Vol 118 (4) ◽  
pp. 797-823
Author(s):  
Yiya Wang ◽  
Hailong Yu ◽  
Shucheng Wu ◽  
Li Liu ◽  
Liuyang Huang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Geothermal System ◽  
Enhanced Geothermal System ◽  
Hot Dry Rock

Numerical Investigation of Combined Sensible/Latent Heat Thermal Energy Storage With Supercritical Carbon Dioxide As Heat Transfer Fluid at 650°C

2019 ◽  
Author(s):  
Kelly Osterman ◽  
Diego Guillen ◽  
D. Yogi Goswami
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Energy Storage ◽  
Supercritical Carbon Dioxide ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Heat Storage ◽  
Storage System ◽  
Heat Transfer Fluid ◽  
Dry Air

Abstract This paper numerically explores a high-temperature sensible-latent hybrid thermal energy storage system designed to store heat with output temperatures stabilized at approximately 550–600 °C for direct coupling with supercritical carbon dioxide (sCO2) power cycles operating at their design point. sCO2 and dry air at 25 MPa are used as heat transfer fluid (HTF) in a packed bed storage system that combines rocks as sensible heat storage and AlSi12 as latent heat storage. The base model using dry air at atmospheric pressure is compared to similar work done at ETH Zurich; the model is then extended for use with sCO2 to compare the performance of air and sCO2 at similar volumetric flow rates. It was found that sCO2 is capable of storing a significantly larger amount of energy (∼40 kWh) in the same time period as the air system (∼19 kWh), and can discharge that energy much quicker (1.5 hours compared to 4 hours). However, in order to achieve similar degrees of temperature stabilization, the total height of PCM had to be increased significantly, from 9 cm to 45 cm or more.

scholarly journals Coupled Thermo-Hydro-Mechanical-Chemical Modeling of Permeability Evolution in a CO2-Circulated Geothermal Reservoir

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Jing Tao ◽  
Yu Wu ◽  
Derek Elsworth ◽  
Pan Li ◽  
Yang Hao
Keyword(s):  
Heat Transfer ◽  
Initial Pressure ◽  
Mineral Dissolution ◽  
Geothermal Reservoir ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Geothermal System ◽  
Permeability Change ◽  
Short Term ◽  
Mineral Precipitation

The meager availability of water as a heat transfer fluid is sometimes an impediment to enhanced geothermal system (EGS) development in semi-arid regions. One potential solution is in substituting CO2 as the working fluid in EGS. However, complex thermo-hydro-mechanical-chemical (THMC) interactions may result when CO2 is injected into the geothermal reservoir. We present a novel numerical model to describe the spatial THMC interactions and to better understand the process interactions that control the evolution of permeability and the heat transfer area. The permeability and porosity evolution accommodate changes driven by thermo-hydro-mechanical compaction/dilation and mineral precipitation/dissolution. Mechanical and hydraulic effects are demonstrated to exert a small and short-term influence on permeability change, while the thermal effects are manifest in the intermediate and short-term influence. The most significant and long-term influence on permeability change is by chemical effects, where decreases in fracture permeability may be of the order of 10-5 due to calcite precipitation in fracture throats, which causes the overall permeability to reduce to 70% of the initial permeability. The initial pressure and temperature of the injected CO2 exerts an overriding influence on permeability. In particular, an increased temperature reduces the mineral precipitation in the fracture and enhances mineral dissolution within the matrix and pore but results in mechanical closure of the fractures. Optimizing injection pressure and temperature may allow the minimization of precipitation and the maximization of heat recovery.

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