Yu T.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Liu P.,Hong Kong Polytechnic University |
Chu G.,Shandong University of Technology |
Li Y.,Northeast Forestry University
Advanced Materials Research | Year: 2012
Constant geothermal temperature is necessary to the long-term efficient operation of the ground source heat pump. SGSHP (Solar-Ground Source Heat Pump) system adopts solar energy as assistant heat source to maintain the geothermal temperature in cold regions. A design method based on equilibrium geothermal temperature was illustrated with an example of a villa in Beijing, China. Flowchart and control strategy of the combined system were introduced. Average heat collection efficiency and necessary area of the solar collector were derived on the basis of energy balance equation. Geothermal temperature variation was also researched to test if the solar energy and geothermal energy were reasonably matched. Results show that the combined system can maintain a constant geothermal temperature if it is well designed. The solar-ground source heat pump system is efficient, reliable and energy-saving. © (2012) Trans Tech Publications, Switzerland.
Man Y.,Hong Kong Polytechnic University |
Man Y.,Shandong Jianzhu University |
Man Y.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Yang H.,Hong Kong Polytechnic University |
And 3 more authors.
Applied Energy | Year: 2012
Ground coupled heat pump (GCHP) system is regarded as one of the effective energy saving technologies, and obtains popular applications for air conditioning all over the world. However, experimental studies on the GCHP system are still insufficient. In order to investigate the practical performance of GCHP system, the detailed on-site experiments are carried out on a GCHP test rig located in temperate zone. Operation parameters recorded during tests mainly include the temperature distributions of borehole at different depths, the temperature and flow rate of water circulating in the heat pump as well as the ground heat exchanger, the refrigerant pressure, and the power consumption of heat pump as well as circulating pumps. The GCHP system for both cooling provision and heating provision are investigated with two operation modes, which are the intermittent mode and continuous mode. Experimental results indicate that the performance of GCHP system is affected by its operation conditions and modes. Besides, heat and cold accumulation in the ground during cooling and heating provision of the GCHP system are analyzed. © 2011 Elsevier Ltd.
Cui P.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Cui P.,Shandong Jianzhu University |
Cui P.,Shandong Key Laboratory of Building Energy saving Technique |
Li X.,Shandong Key Laboratory of Building Energy saving Technique |
And 2 more authors.
Applied Energy | Year: 2011
This paper investigates the transient heat conduction around the buried spiral coils which could be applied in the ground-coupled heat pump systems with the pile foundation as a geothermal heat exchanger. A transient ring-coil heat source model is developed, and the explicit analytical solutions for the temperature response are derived by means of the Green's function theory and the image method. The influences of the coil pitch and locations are evaluated and discussed according to the solutions. In addition, comparisons between the ring-coil and cylindrical source models give that the improved finite ring-coil source model can accurately describe the heat transfer process of the pile geothermal heat exchanger (PGHE). The analytical solutions may provide a desirable and better tool for the PGHE simulation/design. © 2011 Elsevier Ltd.
Zhang L.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Zhou S.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Liu J.,Shandong Jianzhu University
Proceedings - 2015 6th International Conference on Intelligent Systems Design and Engineering Applications, ISDEA 2015 | Year: 2015
In order to the further analyze the impact of pipe temperature drop on the thermal characteristics of the central heating system, this study uses the method of fluid network analysis with considering the pipe temperature drop, and adds the heat exchanger model. Using the mathematical models of thermal, the pipe network thermal imbalance phenomenon was analyzed and simulated under the hydraulic balance. Meanwhile, this paper uses the quality adjustment and quantity adjustment method to realize the pipe network simulation of thermal balance. Through the comparative analysis of five kinds thermodynamic conditions pipe network characteristic, the results show that the temperature drop of the pipeline has an important influence on thermal balance and heating effect, with realizing the necessity of thermodynamic equilibrium. © 2015 IEEE.
Yang D.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Lu X.,Shandong Jianzhu University
Advanced Materials Research | Year: 2014
As Zibo power plant original steam pipes for a long time to run, the strength decreased and resistance was large, transformation was proposed to optimize. A mathematical model of the main steam pipe network was established to analysis changes of temperature, pressure and velocity vector before and after transformation. After transformation, the loss was significantly reduced,so transformation successfully achieve the optimization, adjustment and analysis functions of the main steam pipe network. © (2014) Trans Tech Publications, Switzerland.
Xu L.,Shandong Jianzhu University |
Xu L.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Chang J.,Shandong Jianzhu University |
Wang Z.,Shandong Jianzhu University
Modern Tunnelling Technology | Year: 2015
Because a concentred smoke extraction system enables the diffusion range of upstream and downstream smoke to be better controlled, it is widely used in the design of long tunnels. In this paper, a theoretical model of defined diffusion of a fire plume in a tunnel with a concentred smoke extraction system is established for a small-scale fire scenario, and these theoretical results are compared with experimental results to verify the theoretical model and predict such thermal parameters as the maximum temperature rise and the offset distance of smoke underneath the tunnel roof. The prediction results show that: 1) the maximum temperature rise of smoke drops sharply with an increase of equivalent wind velocity when the fire intensity is unchanged, and the fire intensity has a remarkable effect on the temperature rise; 2) when the equivalent wind velocity is over 1.5 m/s, the rising temperature will slow down until it becomes constant; 3) however, the plume has no obvious offset when the wind velocity is small, as its offset increases with an increase of wind velocity but its change rate decreases with an increase of fire intensity. Based on the regression method, a dimensionless criterion correlation is obtained regarding the maximum temperature rise and offset distance of smoke underneath the tunnel roof. ©, 2015, Editorial Office of "Modern Tunnelling Technology". All right reserved.
Wang D.,Hong Kong Polytechnic University |
Lu L.,Hong Kong Polytechnic University |
Zhang W.,Hong Kong Polytechnic University |
Cui P.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Cui P.,Shandong Jianzhu University
Applied Energy | Year: 2015
The effect of groundwater flow on the heat transfer performance of pile geothermal heat exchanger (PGHE) with spiral coils was simulated by a 3-D simulation model using finite element method. Different groundwater flow conditions were taken into consideration by applying different hydraulic gradients. Based on the moving ring-coils model and simulation results, an improved analytical model is developed by introducing a key parameter of effective dimensionless velocity. The calculation results shows that the improved model can better describe the heat transfer performance of PGHE with spiral coils. Both numerical and analytical results indicated that the groundwater flow has an enhancing effect on the heat transfer performance of the PGHE with spiral coils and can accelerate the heat transfer process into stability. When the groundwater flow mean velocity equal to 6.98E-06. m/s, the amount of heat exchange is higher than 26.72% than it of non-advection situation. The improved ring-coils analytical model can be used as a reliable tool for the design of pile geothermal heat exchanger with spiral coils under groundwater flow. © 2015 Elsevier Ltd.
Li M.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Li M.,Central South University |
Li P.,Central South University |
Chan V.,Nanyang Technological University |
Lai A.C.K.,City University of Hong Kong
Applied Energy | Year: 2014
Heat transfer by borehole ground heat exchangers involves diverse time-space scales and thus imposes a significant challenge to geothermal engineers. In order to overcome this challenge, this paper develops an analytical full-scale model from the idea of matched asymptotic expansion. The full-scale model is a composite expression consisting of a composite-medium line-source solution (inner solution), a finite line-source solution (outer solution), and an infinite line-source solution. The full-scale model is first verified by a frequency-decomposition method. Furthermore, the full-scale model is reformulated as a multi-stage model based on Duhamel's theorem to reduce the computational cost. The multi-stage model combines the three separate solutions in a sequential way, i.e., the inner solution for the short-time scale, the conventional infinite line-source solution for the intermediate time scale, and the outer solution for the long-time scale. Finally, we perform a parametric study on a ground heat exchanger with single U-shaped tube, by which the spacing between U-tube legs, the length-to-radius ratio of borehole, the ratios of thermal diffusivities and conductivities of the ground and backfilling material are analyzed. © 2014 Elsevier Ltd.
Li H.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Liu F.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Duan P.,Shandong Key Laboratory of Building Energy saving Technique
Chinese Control Conference, CCC | Year: 2016
The Ground Source Heat Pump (GSHP) module provided by Transient System Simulation Program (TRNSYS) simulation software will lead to wrong simulation results on partial load, which is only suitable for full load operation. In order to solve this problem, a new mathematical model of GSHP is established based on the experience knowledge of GSHP and the sample data provided by manufacturer. Firstly, the cooling capacity and energy consumption of a GSHP are analyzed according to the GSHP principle. Then, the Cerebellar Model Articulation Controller (CMAC) mathematical models of cooling capacity correction coefficient and power correction coefficient on full load are established according to the sample data provided by manufacturer, and the mathematical model of power correction factor on partial load is established based on the nonlinear regression model. Finally, the Coefficient of Performance (COP) of a GSHP and the outlet temperature of condenser are calculated according to the GSHP principle. Experimental results show that the accuracy of the CMAC mathematical models of cooling capacity correction coefficient and power correction coefficient on full load are better than that of the conventional multivariate nonlinear regression model. The developed GSHP mathematical model can be used to simulate the GSHP system very well. © 2016 TCCT.
Qian H.,Jinan Key Laboratory of Renewable Energy Utilization Technologies In Buildings |
Qian H.,Shandong Key Laboratory of Building Energy saving Technique |
Wang C.,China University of Petroleum - Beijing
Applied Mechanics and Materials | Year: 2011
Experiments have been performed to observe flow pattern and investigate convective heat transfer for air-water vertical flow in a forced circulation system. The bubbles motion was recorded by a high-speed CCD camera. For the bubble and slug flow pattern, the temperature fluctuation signals and local heat transfer coefficients were obtained in a short heated tube. The probability density function classical was applied to analyze the temperature. The results qualitatively reflected characteristics of local heat transfer in two phase flow comparing with that in single-phase liquid. The comparison revealed that the gas phase could enhance the heat transfer. © (2011) Trans Tech Publications.