No abstract

Windows have a great impact on building energy consumption, and the thermal performance of window frames directly affects its energy-saving potential. In this paper, a novel method is proposed to optimize the thermal performance of commercially available broken-bridge aluminum window frames, by incorporating radiant insulation panels (RIPs) into the window frame cavity. A typical aluminum alloy window frame heat transfer model is theoretically analyzed and validated, and the effects of key design parameters on the equivalent thermal conductivity (ETC) of the cavity radiation heat transfer and the heat transfer coefficient (U-factor) of window frames are quantitatively analyzed by a finite element simulation method using the THERM software. Moreover, the RIP, the insulation material filling, and low surface emissivity on the thermal performance of the window frame are compared and analyzed. The results show that the RIP is better placed in the middle, the width and quantity of RIPs are negatively correlated with the U-factor, while the surface emissivity of RIPs is positively correlated with the U-factor. Adding RIPs in the cavity can reduce the U-factor of the window frame by more than 7.43%, slightly lower than 8.97% for the filling type, but significantly higher than 0.81% for the low-emissivity type. Inserting RIPs is a simple and effective way to reduce the U-factor of the window frame and have a great potential of use.

Thermal performance assessment and optimization for energy conversion and utilization systems are of high significance in building energy efficiency. Generally speaking, the evaluation of actual thermodynamic system performance is mainly based on the first law of thermodynamics, with emphasis on the quantity of energy consumption, while ignoring the energy quality. Thus, it results in a one-sided evaluation in the analysis of system energy saving. In this paper, the electricity equivalent is used to analyze and evaluate the air source heat pump (ASHP) heating system under the different working conditions. Moreover, the dynamic thermal performances of three typical space heating devices (radiator, fan coil and radiant floor) are investigated and compared by weighing both energy quantity and quality. The results show that the COP of radiator, fan coil and are radiant floor are 3.00, 3.82 and 4.76, and COEQ are 48.32%, 51.43% and 50.57%, respectively. However, the robustness of its thermal performance is lower than that of radiator and fan coil. This work can provide reference for energy systems assessment and guidance for practical design of building heating systems.