| Room air conditioner(RAC) is widely used with the advantages of high efficiency, energy-saving and environmental protection. It performs well in summer with high efficiency of refrigeration while its heating promotion is limited in scope during winter due to the dependence on climate. Hence, radiation heating room air conditioner (RHRAC) system was introduced in the research of this dissertation to improve heating efficiency of RAC and reduce its dependence on climate. Based on RAC system, the buried condenser pipes are added to RHRSAC system where refrigerant acts as heat medium for direct floor radiant heating.A steady-state condition model for RHRAC system was established during the research. The modeling of condenser and evaporator adopted the distributed parameter method while the theoretical calculation method was used for compressor modeling. Additionally, the capillary model was established by the combination of relational and distributed parameter methods. For buried condenser pipes, differential equations were introduced for the modeling of heat transfer process. On the basis of dichotomy, MATLAB simulation were adopted to solve the RHRAC system models with R290 and R410a. The simulation results for RHRAC system with R290 were analyzed when heated by condenser or buried condenser pipes and during different heating modes. Furthermore, under the same condition, the simulation results were then compared between the RHRAC system with R290 and R410a. Lastly, the RHRAC system was optimized in three aspects which were concluded as the further optimization of buried condenser pipes, the best filling volume of R290 and the variable load operation of RHRAC system. Results of the main research are followed as below:1. For RHRAC system with R290, the heating efficiency of buried condenser pipes is better than that of condenser. Under the same condition, heat exchange amount of buried condenser pipes is lower than that of condenser while the indoor temperature is higher when using buried condenser pipes for heating than using condenser. During heating periods, buried condenser pipes are beneficial to maintain the higher COP by reducing the fluctuation of indoor temperature and the system’s dependence on climate. Continuous operation and intermittent operation of R290 system are both able to meet the demand of heating. Besides, intermittent operation saves more energy by making good use of the well heat storage capability of floor radiant heating.2. By comparing the heating characteristics of RHRAC system with R290 and R410a, results are calculated as follows:Under the same condition, the working pressure of R410a is about 56% higher than that of R290. Using refrigerants of R290 and R410a respectively can both obtain comfortable indoor temperature and well heating effect. Heating COP with R410a is only about 85.5% of that with R290.3. Results of optimization design are stated as follows:(1) Welding wire mesh on buriedcondenser pipes improve the heat transfer. The less gap of mesh spacing, the higher value of floor surface temperature and heat flux density. In this paper,60mm wire mesh spacing is recommended. The effect of strengthening heat transfer of copper wire, aluminum wire, iron wire, steel wire decreases in turn. With the high cost of copper wire and the poor heat transfer performance of steel wire, copper wire and aluminum wire are recommended in this paper. (2) During the period of heating by radiation, condensing pressure and condensing temperature increased with the increase in the filling volume of R290 while the evaporating pressure decreased slightly. In addition, the value of heating COP increased firstly and then decreased as a result. The best filling quantity of this system is founded as 390g in this research.(3) When RHRAC system with R290 operates stably, the system performs with the highest heating COP at capacity output of 40% load. |
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