The performance of a BTES （borehole thermal energy storage） system is primarily governed by ground heat flux, soil thermal properties and groundwater conditions. However, the design of the heat exchanger used within...The performance of a BTES （borehole thermal energy storage） system is primarily governed by ground heat flux, soil thermal properties and groundwater conditions. However, the design of the heat exchanger used within the BTES system can also make a significant difference in the efficiency of the system. A thermal response test was carded out for a Kelix GHE （ground heat exchanger） system, the latest innovation in geothermal ground loop construction, on an Ecofarm in the town of Caledon East, Ontario, Canada. In addition, a verifying test was performed for a CEES （conventional earth energy system） located 6 m away from the Kelix GHE. The boreholes for these two different heat exchanger designs were drilled with the same diameter, to the same depth and were located in the same/identical geo-hydrological conditions. The response test provided the effective average of undisturbed ground temperature, geothermal properties including thermal conductivity, heat capacity and thermal resistance between the fluid and the borehole wall. The mathematical analysis method used for the response test is presented here. Results of the response test were verified, analyzed and are further discussed.展开更多
The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(F...The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(FEM) in polar or cylindrical coordinates for the solution of heat transfer problems. This document shows how to apply the most often used boundary conditions. The global equation system is solved by the Crank-Nicolson method. The proposed algorithm is verified in three numerical tests. In the first example, the obtained transient temperature distribution is compared with the temperature obtained from the presented analytical solution. In the second numerical example, the variable boundary condition is assumed. In the last numerical example the component with the shape different than cylindrical is used. All examples show that the introduction of the polar coordinate system gives better results than in the Cartesian coordinate system. The finite element method formulation in polar coordinates is valuable since it provides a higher accuracy of the calculations without compacting the mesh in cylindrical or similar to tubular components. The proposed method can be applied for circular elements such as boiler drums, outlet headers, flux tubes. This algorithm can be useful during the solution of inverse problems, which do not allow for high density grid. This method can calculate the temperature distribution in the bodies of different properties in the circumferential and the radial direction. The presented algorithm can be developed for other coordinate systems. The examples demonstrate a good accuracy and stability of the proposed method.展开更多
The W UMa-type contact binaries have been observed for several decades.To construct the evolutionary model for W UMa-type contact binaries,many difficulties were encountered due to the existence of complicated physica...The W UMa-type contact binaries have been observed for several decades.To construct the evolutionary model for W UMa-type contact binaries,many difficulties were encountered due to the existence of complicated physical processes in such systems.The model introduced by Huang,Song and Bi includes some special and unique understandings of the physical processes of contact binaries.It is necessary to test whether this model can be used for W UMa-type contact binaries.The best way to test a theoretical model is to know whether this model can explain the observational phenomena of such systems.For this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et al.and those from the astronomical observations.The result of the comparison indicates that this model can be applied to W UMa-type contact binaries and can explain the observational phenomena of such binaries.展开更多
文摘The performance of a BTES （borehole thermal energy storage） system is primarily governed by ground heat flux, soil thermal properties and groundwater conditions. However, the design of the heat exchanger used within the BTES system can also make a significant difference in the efficiency of the system. A thermal response test was carded out for a Kelix GHE （ground heat exchanger） system, the latest innovation in geothermal ground loop construction, on an Ecofarm in the town of Caledon East, Ontario, Canada. In addition, a verifying test was performed for a CEES （conventional earth energy system） located 6 m away from the Kelix GHE. The boreholes for these two different heat exchanger designs were drilled with the same diameter, to the same depth and were located in the same/identical geo-hydrological conditions. The response test provided the effective average of undisturbed ground temperature, geothermal properties including thermal conductivity, heat capacity and thermal resistance between the fluid and the borehole wall. The mathematical analysis method used for the response test is presented here. Results of the response test were verified, analyzed and are further discussed.
文摘The aim of this paper is the formulation of the finite element method in polar coordinates to solve transient heat conduction problems. It is hard to find in the literature a formulation of the finite element method(FEM) in polar or cylindrical coordinates for the solution of heat transfer problems. This document shows how to apply the most often used boundary conditions. The global equation system is solved by the Crank-Nicolson method. The proposed algorithm is verified in three numerical tests. In the first example, the obtained transient temperature distribution is compared with the temperature obtained from the presented analytical solution. In the second numerical example, the variable boundary condition is assumed. In the last numerical example the component with the shape different than cylindrical is used. All examples show that the introduction of the polar coordinate system gives better results than in the Cartesian coordinate system. The finite element method formulation in polar coordinates is valuable since it provides a higher accuracy of the calculations without compacting the mesh in cylindrical or similar to tubular components. The proposed method can be applied for circular elements such as boiler drums, outlet headers, flux tubes. This algorithm can be useful during the solution of inverse problems, which do not allow for high density grid. This method can calculate the temperature distribution in the bodies of different properties in the circumferential and the radial direction. The presented algorithm can be developed for other coordinate systems. The examples demonstrate a good accuracy and stability of the proposed method.
基金supported by the National Natural Science Foundation of China (Grant No. 10933002)
文摘The W UMa-type contact binaries have been observed for several decades.To construct the evolutionary model for W UMa-type contact binaries,many difficulties were encountered due to the existence of complicated physical processes in such systems.The model introduced by Huang,Song and Bi includes some special and unique understandings of the physical processes of contact binaries.It is necessary to test whether this model can be used for W UMa-type contact binaries.The best way to test a theoretical model is to know whether this model can explain the observational phenomena of such systems.For this aim,a comparison is performed for the relations of mass-luminosity,mass-radius,and the distribution in the HR diagram obtained from the model introduced by Huang et al.and those from the astronomical observations.The result of the comparison indicates that this model can be applied to W UMa-type contact binaries and can explain the observational phenomena of such binaries.
