Supply ventilation – energy use impact
I downloaded BEOpt and EnergyPlus and have been experimenting. Some of the outputs are surprising at first but make sense when I think more deeply, However, I have not been able to make sense of the results I am getting for different ventilation options. I am trying to determine if there is some physics advantage to supply ventilation or whether the results I am getting are modeling errors.
I have four cases: no ventilation, exhaust, supply, and 70% efficient HRV. The later three all use the same ventilation rate in cfm. The software reports the source energy used per year for various categories. The source energy for heating comes out:
none:40.9
排气：52.12
supply: 47.79
hrv: 44.79.
The relative values make sense for none, exhaust, and hrv. But why wouldn’t supply be about the same as exhaust? In each case, you are bringing in the same quantity of unconditioned air. The fan vent energy is the same for exhaust and supply. (It goes up dramatically for HRV, making the total energy for HRV higher than for supply.) The HVAC fan energy is close, with exhaust being slightly higher than the other three. I would have expected supply to be higher in that category if the software is modeling a CFIS system.
The software automatically determined the following heating capacities:
none: 29.53
排气：30.99
supply: 27.73
HRV：30.74。
GBA细节库
由气候和房屋部分组织的一千个建筑细节的集合
答复
里德，
供应通风系统最常见的类型是中央粉丝集成的供应通风系统。（要了解有关这些系统的更多信息，请参阅设计良好的通风系统.)
我不知道BEOPT假设是否基于实际房屋中的能量监视数据，或者Beopt是否基于计算。Beopt可能会做出良好的假设，或者其假设可能存在缺陷。
也就是说，这是您引用的数字的一种可能的解释：在一年中的大部分时间里，中央粉丝集成的供应通风系统都在没有任何额外的风扇能源的情况下运行。它使用了已经需要用于其他目的的风扇（空间加热和冷却）。相反，没有风扇能量，排气通风系统无法运行。
BEOpt报道通风机能源、暖通空调风扇energy, and heating energy separately. If it was modeling CFIS, I would expect vent fan energy to be much lower than exhaust only, HVAC fan energy to be much higher, and heating energy to be the same. It is reporting equal vent fan energy, slightly lower HVAC fan energy, and much lower heating energy. That leads me to believe that it is modeling some other configuration of supply ventilation than CFIS. I cannot envision a configuration that would produce those results. I am inclined to attribute this to some bad data somewhere in the software. However, since the results are favorable, if there is a real system that would produce those results, I would be interested in it.
我在Beopt论坛上找到了关于似乎是同一问题的对话。那里的响应表明这是由于与管道泄漏的相互作用所致。我将尝试在该论坛上获得更多澄清，并在此处报告，如果答案对此读者来说很有趣。
经过一些更详细的分析，我能够回答自己问题的主要部分。供应通风和排气通风之间的加热能量的差异是由于与浸润速率和浴室风扇和射程引擎盖（例如浴室风扇）的相互作用。如果没有发生斑点通风，供应通气和排气通风都会增加浸润 +机械通气的数量相同（尽管小于机械通气速率）。然而，当斑点通风启动时，它进一步增加了排气类型的浸润 +机械通气，但减少了供应类型的渗透通气。该软件将斑点通风算作机械通气的一部分并报告净流。因此，当发生斑点通风时，供应通气比排气通风更有效。
在每种情况下，该模型都假设整个房屋通风系统都以Ashrae速率连续运行。在该假设下，供应优于排气。一旦人们考虑了如何实际实施，结论可能会有所不同。例如，如果使用浴室风扇实现排气系统，则控制控制至少要考虑点频道通风的部分。同样，以更高的流速（例如CFI）间歇性运行的系统可能不会显示出相同的行为。