在通风系统设计中，过滤单元的配置方式直接影响空气净化效能与运维成本。内置过滤与外置过滤作为两种主流方案，其选型需综合考量空间布局、过滤效率、维护便利性及全生命周期成本，方能实现系统性能与经济性的平衡。

　　In the design of ventilation systems, the configuration of filtration units directly affects the air purification efficiency and maintenance costs. As the two mainstream solutions, the selection of internal and external filters requires comprehensive consideration of spatial layout, filtering efficiency, maintenance convenience, and full lifecycle costs in order to achieve a balance between system performance and economy.

　　结构形式与空间适配性

　　Structural form and spatial adaptability

　　内置过滤系统将过滤单元集成于通风管道内部，通常采用抽屉式或模块化设计，直接嵌入风管截面。这种形式对安装空间要求极低，尤其适合层高受限的既有建筑改造项目。例如，在办公楼吊顶内敷设管道时，内置过滤器可避免占用额外净空，但需预留检修口以便滤材更换。外置过滤系统则独立于主风管，通过旁通管道或独立机组实现过滤功能，需配置专用设备间或吊装空间。对于新建项目，外置方案可规避风管内操作难度，但需在建筑设计阶段统筹规划设备布局。

　　The built-in filtering system integrates the filtering unit inside the ventilation duct, usually using a drawer style or modular design, directly embedded in the duct section. This form has extremely low requirements for installation space, especially suitable for existing building renovation projects with limited floor height. For example, when laying pipes in the ceiling of an office building, a built-in filter can avoid occupying additional clearance, but it is necessary to reserve an access hole for filter material replacement. The external filtering system is independent of the main air duct and achieves filtering function through bypass pipelines or independent units, requiring dedicated equipment or lifting space. For new construction projects, the external solution may specify the difficulty of operating inside the wind shelter, but the equipment layout needs to be planned and coordinated during the architectural design phase.

　　过滤效能与阻力特性

　　Filtering efficiency and resistance characteristics

　　过滤效率方面，两种方案均能实现从初效到高效的全系列覆盖。内置系统因滤材直接接触气流，容尘量相对较大，但高阻力滤材会导致系统压降显著增加。实测数据显示，采用F9滤材的内置过滤会使风机能耗提升15%-20%，需校核风机曲线确保运行在高效区。外置系统可通过变频风机动态调节风量，维持恒定静压，但旁通管道会产生附加局部阻力。对于洁净度要求严苛的场景，外置方案更易实现多级过滤串联，如预过滤+高效过滤的组合，延长高级滤材使用寿命。

　　In terms of filtration efficiency, both schemes can achieve full range coverage from initial efficiency to high efficiency. The built-in system has a relatively large dust holding capacity due to the direct contact of the filter material with the airflow, but high resistance filter materials can significantly increase the system pressure drop. Actual test data shows that using F9 filter material for built-in filtration can increase the energy consumption of the fan by 15% -20%. It is necessary to verify the fan curve to ensure that it operates in the high-efficiency zone. The external system can dynamically adjust the air volume through a variable frequency fan to maintain a constant static pressure, but the bypass pipeline will generate additional local resistance. For scenarios with strict cleanliness requirements, external solutions are more likely to achieve multi-stage filtration in series, such as the combination of pre filtration and high-efficiency filtration, extending the service life of advanced filter materials.

　　运维管理与成本分析

　　Operations Management and Cost Analysis

　　维护便利性是选型的关键考量。内置过滤器更换需进入风管内部，操作空间受限，单次维护耗时是外置系统的2-3倍。某医院项目实测显示，更换内置F7滤材需4人协同作业2小时，而外置机组仅需1人30分钟即可完成。从全生命周期成本看，内置系统初期投资较低，但滤材更换频率高，运行5年总成本可能反超外置方案。外置系统虽设备成本高20%-30%，但标准化滤材采购成本可降低15%，且支持在线监测与自动报警功能，减少非计划停机风险。

　　Convenience of maintenance is a key consideration in selection. The replacement of the built-in filter requires entering the interior of the air duct, which limits the operating space and results in a maintenance time 2-3 times that of the external system. According to actual testing in a hospital project, replacing the built-in F7 filter material requires 4 people to work together for 2 hours, while the external unit only takes 1 person 30 minutes to complete. From the perspective of full lifecycle cost, the initial investment of the built-in system is relatively low, but the frequency of filter material replacement is high, and the total cost after 5 years of operation may exceed that of the external solution. Although the cost of external systems is 20% -30% higher, the procurement cost of standardized filter materials can be reduced by 15%, and they support online monitoring and automatic alarm functions, reducing the risk of unplanned downtime.

　　特殊工况适配策略

　　Adaptation strategy for special working conditions

　　在高温高湿环境，外置过滤系统可配置独立温湿度调节单元，避免滤材受潮失效。对于腐蚀性气体处理，内置系统需采用316L不锈钢框架与耐腐蚀密封胶条，而外置机组可通过正压设计防止气体侵入电气舱。在洁净室应用中，外置方案更易实现气密性检测，通过压力衰减试验验证泄漏率≤0.01%/h，内置系统则需分段保压测试，检测效率降低50%。

　　In high temperature and high humidity environments, the external filtration system can be equipped with an independent temperature and humidity control unit to prevent the filter material from becoming damp and ineffective. For the treatment of corrosive gases, the built-in system requires a 316L stainless steel frame and corrosion-resistant sealing strips, while the external unit can prevent gas from entering the electrical compartment through positive pressure design. In cleanroom applications, external solutions are easier to achieve airtightness testing, with a leakage rate of ≤ 0.01%/h verified through pressure attenuation tests. For internal systems, segmented pressure holding tests are required, reducing detection efficiency by 50%.

　　选型决策模型

　　Selection Decision Model

　　建立三维评价体系可科学指导选型：

　　Establishing a three-dimensional evaluation system can scientifically guide selection:

　　空间维度：当可用层高＜2.6米或风管间距＜0.5米时，内置系统为必选项；

　　Space dimension: When the available floor height is less than 2.6 meters or the air duct spacing is less than 0.5 meters, the built-in system is a mandatory option;

　　效率维度：对PM2.5去除率要求＞95%时，优先采用外置双级过滤；

　　Efficiency dimension: When the requirement for PM2.5 removal rate is greater than 95%, external two-stage filtration should be prioritized;

　　成本维度：运行时间＞4000小时/年时，外置系统综合成本优势显现。

　　Cost dimension: When the operating time exceeds 4000 hours per year, the comprehensive cost advantage of external systems becomes apparent.

　　通过典型场景对比可见，医院手术室因空间局促且需定期消毒，更适合内置HEPA过滤；电子厂房因洁净度要求高且连续运行时间长，外置方案更具优势。实际应用中，混合部署模式逐渐兴起，如在主风管采用内置初效过滤降低大颗粒负荷，在屋顶设置外置高效过滤机组，实现分级净化与能效优化。

　　By comparing typical scenarios, it can be seen that hospital operating rooms are more suitable for built-in HEPA filters due to limited space and the need for regular disinfection; Due to high cleanliness requirements and long continuous operation time, the external solution is more advantageous for electronic factories. In practical applications, the hybrid deployment mode is gradually emerging, such as using built-in primary filtration in the main air duct to reduce the load of large particles, and setting up external high-efficiency filtration units on the roof to achieve graded purification and energy efficiency optimization.

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