空调系统中各类(火用）负荷分析与比较

 从(火用)概念出发分析了空调系统中的各类(火用)负荷，探讨其在多种因素影响下的变化规律。为此，以室外空气状态为参考环境，建立了各类(火用)负荷的计算公式，包括室内显热(火用)负荷、室内潜热(火用)负荷、新风显热(火用)负荷和新风潜热(火用)负荷。以长沙某办公建筑标准层为例，分析了其空调系统在夏季工况下间隙运行时的空调负荷与风冷和水冷两种情况下的(火用)负荷。结果显示，空调负荷和(火用)负荷在范围及变化趋势上存在明显差异；空调负荷的品质很低，应采用低品位能源；新风潜热(火用)负荷在空调(火用)负荷构成中最大，采用表冷器除湿将产生大量冷凝水(火用)损；室内显热(火用)负荷的峰值比室内显热负荷要推后4h；采用水冷空调系统的(火用)负荷明显低于风冷空调系统的(火用)负荷。

Analysis and Comparison of Different Types of Exergy Loads in HVAC Systems

The exergy loads of the HVAC system are analyzed to see the variation patterns under different influencing factors. The state of outdoor air is selected as the reference state and the equations for exergy load calculations are derived, including exergy loads of sensible heat and latent heat for indoor air and fresh air, respectively. Then, different types of air conditioning loads and the corresponding exergy loads are analyzed for a standard floor of an office building in Changsha as a case study, which is equipped with an air-cooled system or a water-cooler system under the intermittent operation condition. The results show that the significant differences exist between the air conditioning loads and the exergy loads with respect to variation range and change trend. The energy quality of air-conditioning loads is very low, so it is more suitable to use low-grade energy sources to drive air conditioning systems. The exergy load of latent heat of fresh air is the highest in all exergy loads because of its large amount of exergy destruction of condensed water. The maximum indoor exergy load of sensible heat is observed 4 hours later than its air conditioning part. Moreover, the exergy loads in the water-cooled system are considerably less than those in the air-cooled system.