Study On Heat Transfer And Operational Characteristics Of Novel Thermal Storage Heating Floor In Low-energy Buildings

With the upgrading of building energy-saving requirements,thermal insulation and heat storage characteristics of envelopes of low-energy building in severe cold regions have been significantly improved,which make building envelops have thermal storage and energy flexibility potential for assisting the heating systems in shifting the energy consumption from power grid within a range.Building heating terminal is the key facility to achieve thermal energy storage of building thermal mass.As a common heating terminal of low-energy buildings in severe cold regions,the thermal response speed,operational flexibility and thermal storage stability of radiant heating floor are low,which restrict the potential of deploying radiant heating floor as the flexible thermal storage terminal.In this study,a novel thermal storage heating floor made of air duct and phase change mortar is proposed to improve the heating and thermal storage means of radiant heating floor in low-energy buildings.The heating and thermal storage performance is experimentally investigated,and the heat transfer and thermal storage processes are modelled.On this basis,the impact of key structural and operating parameters on heating performance and energy consumption characteristics are analyzed,the operating characteristics of the floor in both traditional power system and mixed wind power heating system are investigated,and the optimization algorithm for the operation of the heating floor is proposed.The main research contents are as follows:First,in view of the slow thermal response characteristics of the traditional radiant heating floor,a novel thermal storage heating floor was proposed,and micro-encapsulated phase change material was added to improve the stability of floor heating and energy storage.Based on the scaled experimental system,the impact of phase change material distribution,phase change material content,different ventilation systems and intermittent operation modes on the heating and energy consumption characteristics of heating floor was analyzed.Next,based on the principle of heat transfer,the heat transfer model and the heat storage and release model of the novel thermal storage heating floor were built.Based on the model,parameter analysis and response surface methods were used to study the impacts of key structural parameters and operating parameters on the thermal performance,heat storage performance and heat use efficiency of the thermal storage heating floor,and the mathematical relationship between the heat storage/use efficiency and relevant parameters under different operation modes were quantified.After that,a thermal storage heating floor was set up in a low-energy demonstration building in a severe cold region,and the space heating performance of the floor under different operating modes and operation conditions were tested.The measurement showed that outdoor thermal disturbances have significant impacts on the heating performance,and the floor can use solar radiant heat absorbed during the daytime to maintain a stable thermal environment at night.Afterwards,the heat transfer mathematical model of the system under actual conditions was constructed.Orthogonal test method and variance analysis method were adopted to analyze the impact of structural and operating parameters on energy consumption and indoor thermal comfort characteristics of the system in both traditional electric heating system and mixed wind power heating system under the set operating rules.The key structural parameters of the ventilated heating floor were optimized,and the best structure design strategy and operation scheme of the thermal storage heating floor for the two energy systems were proposed.Results show that renewable energy consumption,energy-saving performance and indoor thermal stability of the system are significantly improved because of the increased operating flexibility of the floor.In the last,in order to further explore the energy storage potential and operating flexibility of the novel thermal storage heating floor,an improved stochastic optimization algorithm,in which the operating cost,wind power consumption,carbon emission cost and indoor thermal comfort duration were optimized,was proposed,and the performance of the system under single-objective and multi-objective optimization scenarios was analyzed.Results show that compared with the single-objective optimization algorithm,the multi-objective optimization algorithm can find the comprehensive optimal solution.Compared to the performance of the system in the rule-based operating mode,the energy consumption of the optimized system is significantly reduced,and active time of wind power consumption is significantly improved.In summary,based on the characteristics of the building envelopes in severe cold regions,a novel thermal storage heating floor that fully exploits the energy storage capacity of traditional radiant heating system and improves the heating flexibility is proposed in this study,and the optimal floor structural design strategy and operating optimization method of the floor are analyzed.The research findings provide a feasible technical means,a design scheme and an optimization strategy for improving the operating flexibility and thermal comfort of low-energy building heating systems in severe cold regions,and lay a theoretical foundation for the design and application of the novel thermal storage heating floor.