Optimization And Experimental Validation Of Unsteady Heat Transfer RC Model For Thermally Active Building Systems

The unsteady heat transfer of concrete slab is an important research subject for Thermally Active Building Systems, and it is significant for the system operation and control in practice. The RC simplified model is a simplify method for concrete slab heat transfer research. Zhang Cheng has created a method which establishes the simplified models according to the geometry and thermal parameters, and verified the model by FEM numerical method to test the accuracy and find the applicable scope of the RC simplified model. The object of the project is to modify the existent RC simplify method, and extended its application. In addition, a standard test chamber is established to give a further verification for the model.There are two aspects for the model optimization: Firstly, adding the water flow parameter to original three-node simplified model in order to simulation the joint condition of water temperature and water flow. Secondly, extending the RC simplified model to the entire air-conditioning room through finite difference method. In addition, a standard test chamber will be established to determine the heat transfer performance under a step change in water temperature, water flow rate, inner heat gains, and starting process, downtime process. Finally, the simplified model will be validated by experimental data.The following results were summarized. Firstly, the vertical temperature distribution within the slab was calculated using the analogy of thermal processes to electrical circuits; Secondly, an unsteady flow model (Model 2) was obtained combining energy equation based on the existent simplified model (Model 1); Thirdly, the expanded model (Model 3) was build up according to the dimensions of the air conditioning room, the construction of concrete slab, the pipe layout and so on. Fourthly, the computer program was written with the help of MATLAB. Fifthly, the thermal response performance of the tested slab was discussed at varies steady and unsteady conditions through experimental measurement. Sixthly, Grey relational analysis and thermal retardation time methods were adopted to compare simulation data with tested one.The results showed that, the water flow rate had little effect on the cooling performance of concrete slab. It was unsuitable to regulate energy through changes of water flow rate. The steady-state simulation error of the three models was small, and in the unsteady-state conditions, the simulation parameters of the model curve and experimental data were basically the same trend. What's more, the error was smaller when the parameter in a significantly step change condition.