| The new solar air collector with hollow ventilated interior wall（SAC-HVIW）heating system can effectively improve the thermal comfort of residential buildings at night,but it will inevitably be affected by external heat such as auxiliary heat sources and sun patch during use.The instability of sun radiation and the outdoor environment,the fluctuation of the air temperature at the outlet of the collector,the start or stop of the intermittent auxiliary heat source and the irregularity of the power,the change of the sun patch exposure in the room,lead to the heat storage and transfer process of HVIW and the indoor thermal environment poor controllability and large uncertainty.Grasp the heat storage and transfer mechanism of HVIW and its influencing factors under the above-mentioned thermal disturbance coupling,and obtain the accurate calculation method of heat collection,storage and release of SAC-HVIW heating system.By changing the operating parameters of the SAC-HVIW heating system and the intermittent auxiliary heat source,the structure and thermal properties of the HVIW,and the building structure,the heat transfer and heat storage performance of the HVIW can be adjusted to improve the indoor temperature at night,thereby achieving the purpose of adjusting the indoor thermal environment.This is the key to the study of the thermal process of this type of buildingThis article takes full use of the SAC-HVIW heating system to reduce the operating time and operating load of the intermittent auxiliary heat source,ensure the lowest indoor temperature and maximize energy conservation as the control objectives.Aiming at the key technical issues involved in the adjustment of the SAC-HVIW heating system under the coupling of external heat,a combination of theoretical analysis,experimental research and building thermal process simulation is used to study the HVIW heat storage and release characteristics and building dynamic thermal response.Reveal the influence of HVIW’s heat storage and release process on indoor thermal stability,master the optimization and control methods of building dynamic thermal environment,and provide theoretical basis and technical support for solar thermal utilization of residential buildings in cold areas.The detailed study is as follows:First of all,starting from the structural characteristics and operating principles of buildings using the SAC-HVIW heating system under the coupling of external heat,based on reasonable assumptions and simplifications,mathematical analysis methods are used to analyze the heat storage and release,solar incidence,and The thermal process of the building under the combined action of intermittent auxiliary heat sources is theoretically analyzed.Establish mathematical models of building indoor thermal environment with different operating modes and operating periods.Analyze the calculation method of the SAC-HVIW heating system for heat collection,storage and release,obtain the change law of the indoor air temperature of the building using the system,and propose SAC,HVIW and indoor thermal environment evaluation indicators.Secondly,designed a building experiment platform using SAC-HVIW heating system under external heat coupling.By adjusting the air supply volume,internal circulating air heating volume,and external electric film heat control methods,23 groups of steady state and13 groups of non-heating are carried out respectively.Steady-state comparative experiment,grasp the influence of system operation and thermal disturbance parameters on the steady-state heat transfer and non-steady-state heat storage and release performance of the system.The steady-state results show that:（i）The coupling effect of supply air temperature and external heat will not affect the heat transfer coefficient of the inner surface of the HVIW cavity,and the inner surface can be considered linearly related to the supply air speed;（ii）For inherent buildings In terms of form,the radiation heat transfer coefficient of the outer surface of HVIW can be considered as a constant;（iii）The natural convection heat transfer coefficient of the external surface of HVIW increases almost logarithmically with the increase of the heat gain of the HVIW system.The non-steady-state experimental results show that:（i）The greater the total heat gain,the greater the heat flow value of the outer wall of the HVIW,and the full-day maximum and minimum heat flow values of the external heat step are higher than the corresponding stable input conditions;（ii）At the same wind speed and hot air heating capacity,the non-ventilated heat release efficiency when external heat is coupled is greater than 60%,which can be increased by 5-10%compared to when there is no external heat coupling;（iii）Storage when external heat is stably input The occurrence time of thermal efficiency lower than 50%can be delayed by more than 0.5h compared with the absence of external heat coupling;（iv）The higher the air supply speed,the higher the instantaneous heat storage efficiency at the initial start-up stage of the hot air,but it is not conducive to the non-ventilation of heat.Thirdly,an overall model of dynamic heat transfer of buildings with SAC-HVIW heating system under the coupling of external heat is constructed.Using the RC thermal network method,a sub-model of the building envelope and indoor air considering the solar incidence and indoor auxiliary heat sources was constructed,and the Energyplus software was used for verification.In view of the external heat coupling effect of HVIW,the overall coupling model of RC and NTU was improved to a series simplified heat exchange unit model,and the accuracy of the model was proved by experimental data.The sub-calculation model of the collector is established based on the heat balance method.Couple the above three sub-models to obtain the overall model,and use computer programming to solve the model.Then,based on the overall dynamic heat transfer model,the SAC-HVIW heating system’s collection,storage,and heat release characteristics that match the control objectives and the influencing factors of the building thermal process are studied,and the optimization method of the system and building structure is obtained.Taking maximizing the lowest indoor temperature at night as the main optimization goal,the basis for the selection of design and operating parameters such as circulating air volume,meteorological parameters,building structure,and auxiliary heat source is obtained.The results show that:（i）When considering the energy consumption of the circulating fan,the optimal cavity circulating wind speed is about 2～3m/s;（ii）The lowest indoor temperature is linearly related to the intensity of solar radiation;（iii）The wall thickness of HVIW is about 120mm;（iv）For energy-saving buildings,it is more reasonable to choose medium-quality materials to form HVIW;（v）The larger the window-to-wall ratio,the higher the highest indoor temperature,but the lower the lowest temperature;（vi）There is a power function relationship between the lowest indoor temperature and the volumetric depth product,and the fitting formula isTmin（28）188.69（BHD2）-0.421;（vii）When there are 3 or more sunny days in Ganzi Prefecture,even if there is a cloudy day,the minimum indoor temperature requirement of the passive solar house can be met;（viii）The convective auxiliary heat source will inhibit the convective heat transfer of the HVIW into the room,and the radiant auxiliary heat source will inhibit the radiant heat exchange.The low-power hot-air heat source has an ideal effect for long-term operation in low temperature periods.Taking a house in Dangxiong County as an example,the dynamic control requirements of the fans in the buildings with SAC-HVIW system（controlled by frequency conversion according to the temperature of the collector plate with distributed photovoltaic power supply）and the convective auxiliary heat source（2℃control accuracy）are analyzed.The control strategy of the SAC-HVIW and auxiliary heat source combined heating system is carried out and the operation effect analysis of the full heating season is conducted.The total energy consumption of the combined heating system in the heating season is 293.5k W·h,and the total energy consumption of only auxiliary heat source operation is 1151.6k W·h.The energy consumption of the combined heating system is only 25%of the total auxiliary heat source operation.The combined heating system costs￥158.5 for the entire heating season（only auxiliary heat source system is￥621.9）,and the monthly electricity cost is only￥31.7.In this paper,through an in-depth study of the thermal response of HVIW of the SAC-HVIW heating system under the coupling of external heat gain and the change mechanism and law of the indoor dynamic thermal environment.It provides a basis for design optimization and control strategies for residential buildings using this system in the Qinghai-Tibet Plateau to achieve the goals of energy saving,emission reduction and improvement of night comfort,and deliberately explores the phenomenon of solar radiation directly acting on the heating surface. |
