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.

High outdoor PM_2.5 levels in Chinese cities pose significant challenges to maintaining healthy indoor air quality in residential buildings, where mechanical ventilation systems are increasingly adopted for pollution control. In this paper, to control the indoor PM_2.5 concentration, a mass balance equation for the non-uniform mixing model has been established to calculate the filter efficiency. This study aims to optimize PM_2.5 pollution control in residential buildings through mechanical ventilation systems by evaluating the synergistic effects of filter efficiency and ventilation air flow rates under high outdoor PM_2.5 conditions. Field measurements and numerical calculations were conducted to monitor indoor and outdoor PM_2.5 concentrations. Results showed that, When outdoor PM_2.5 concentrations remain below 100 μg/m³, an air exchange rate of 3 h⁻¹ effectively maintains indoor PM_2.5 levels below 35 μg/m³ for M6-F8 air filters. Experimental data demonstrate that when a fresh air system equipped with H10 filters operates at an outdoor PM_2.5 concentration of 150 μg/m³, the corresponding optimal ventilation rate is 0.45 h⁻¹. Increasing the mechanical ventilation rate to 1 h⁻¹ enables the system to effectively handle higher outdoor concentrations up to 176 μg/m³. Under severe pollution scenarios with outdoor PM_2.5 concentrations reaching 250 μg/m³, the air exchange rate should be further increased to 1.65 h⁻¹ to maintain indoor PM_2.5 concentrations within acceptable limits. This study provides practical insights for improving residential indoor air quality under high outdoor PM_2.5 conditions in Chinese cities.

A new type of safety valve that has been authorized will be mainly used in high pressure pipelines or pressure vessels in the fields of petroleum, chemistry, heating and others. In the purpose of overcoming some design flaws of traditional safety valve, it has improved in technology, making that all kinds of high-pressure medium will be safely discharged or imported into the appropriate processing system. It can prevent effectively the staff and environment from the accidental spatter or leakage from loose screw connection caused by the larger impact. To illustrate the fine nature of this improvement, we analyze the different structure characteristics between traditional safety valve and this new type of safety valve and have a CFD simulation.