变风量(VAV)空调系统相比定风量系统为什么更节能?
Why is a variable air volume (VAV) system more energy efficient than a constant volume (CAV) system?
VAV系统根据末端负荷实时调节送风量,而不是始终以设计风量运行。风机功耗近似与风量的三次方成正比,部分负荷下转速下降带来的节能非常显著。同时避免了定风量系统中常见的再热冷热抵消损失。
A VAV system modulates supply airflow in real time to match zone loads instead of running at design flow continuously. Fan power scales roughly with the cube of airflow, so slowing fans at part load yields large savings. It also avoids the reheat penalty of simultaneous cooling and heating typical of CAV systems.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-11-03
来源 · Source
ASHRAE Handbook—HVAC Systems and Equipment,变风量系统章节
ASHRAE Handbook—HVAC Systems and Equipment, Variable Air Volume systems chapter
独立核验依据 · Independent verification: 核验依据 1 OPENLIBRARY 标识 /works/OL38979624W：2004 ASHRAE Handbook--
#暖通空调 #变风量节能
评价冷水机组为什么不能只看名义工况 COP,而要引入 IPLV 这类部分负荷综合性能系数?部分负荷时机组效率为何常常不降反升?
Why is full-load COP alone inadequate for judging chillers, and why do integrated part-load metrics like IPLV exist? Why does efficiency often rise rather than fall at partial load?
建筑冷负荷全年绝大部分时间处于设计值的 40%-80% 区间,名义满载点仅代表少数极端时刻,IPLV 按 100%、75%、50%、25% 四档负荷加权,更能反映实际电耗结构。部分负荷下冷却水温自然回落,冷凝压力降低使压缩比减小,压缩机功耗降幅大于制冷量降幅,COP 随之上升。但过低负荷会因频繁启停或热气旁通抵消这一红利,这正是变频调速机组与多机头分级调节的价值所在。
Building cooling loads sit between 40 and 80 percent of design capacity for most annual hours, while the nameplate point captures only rare extremes; IPLV weights four load points at 100, 75, 50, and 25 percent and therefore tracks real energy use far better. At part load the condenser water naturally runs cooler, condensing pressure and compression ratio drop, and compressor input falls faster than delivered capacity, lifting the COP. Very low loads can erase that gain through frequent cycling or hot-gas bypass, which is precisely where variable-speed drives and staged multi-compressor plants earn their keep.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：此条未指向带版次的可引用著作（通识性内容、机构文件或未展开的英文书名），本库不提供独立书目出处；如需精确引用，需由编辑补全具体篇目与版次。
AHRI Standard 550/590 (I-P): Performance Rating of Water-chilling and Heat Pump Water-heating Packages Using the Electrically Driven, Positive Displacement, Centrifugal or Screw Machines, Air-Conditioning, Heating, and Refrigeration Institute.
AHRI Standard 550/590 (I-P), Performance Rating of Water-chilling and Heat Pump Water-heating Packages, Air-Conditioning, Heating and Refrigeration Institute.
#冷水机组 #部分负荷性能
变制冷剂流量(VRF)多联机相比传统风冷冷水机组+风机盘管方案,节能的原因主要来自哪里?
Where does the energy saving of a VRF multi-split system mainly come from compared with an air-cooled chiller plus fan-coil arrangement?
VRF采用变频压缩机和电子膨胀阀,按室内机实际负荷连续调节制冷剂流量,避免了定频系统的启停损耗和过冷过热再热损失。制冷剂直接蒸发换热省去了冷冻水二次换热的温差损失和水泵功耗。多室内机可分区独立控制并在部分负荷时压缩机长期运行于高效率区间,实测部分负荷季节能效比(IPLV)通常显著高于定容系统。
A VRF system uses inverter-driven compressors and electronic expansion valves to modulate refrigerant flow continuously against the actual load of each indoor unit, avoiding the start-stop losses and reheat penalties of fixed-speed systems. Direct refrigerant evaporation eliminates the temperature-glide loss and pump power of a secondary chilled-water loop. With zoned independent control and compressors operating mostly in their high-efficiency band at part load, measured integrated part-load efficiency (IPLV) is typically well above that of fixed-capacity systems.
难度 进阶 · 适合 大众
CC BY 4.0 · 来源待核验 · Source pending review
来源 · Source
出处备注：此条未指向带版次的可引用著作（通识性内容、机构文件或未展开的英文书名），本库不提供独立书目出处；如需精确引用，需由编辑补全具体篇目与版次。
Zhou et al., Applied Energy, 2008, 85(8): 675-689 / Aynur, Hwang & Radermacher, HVAC&R Research, 2010, 16(3): 293-309
Zhou et al., Applied Energy, 2008, 85(8): 675-689; Aynur, Hwang & Radermacher, HVAC&R Research, 2010, 16(3): 293-309
#变制冷剂流量 #建筑空调节能
为什么密闭会议室待久了昏昏欲睡?二氧化碳浓度多少就该开窗了?
Why do sealed meeting rooms make you drowsy — at what CO2 level should you open a window?
室外二氧化碳约420 ppm,人呼出的气含4%以上。通风不良时浓度节节攀升:1000 ppm 是通行舒适上限,约2000 ppm 起多数人报告闷倦与注意力下滑,5000 ppm 才是职业限值——昏沉远早于危险出现。伦敦大学学院与伯克利实验室的对照实验发现,高浓度下复杂决策得分明显下降。对策是按每人每小时30立方米左右供给新风,或用CO2传感器联动新风,别指望鼻子报警——人嗅不出缺氧。
Outdoor CO2 sits near 420 ppm while exhaled breath carries over four percent. In poorly ventilated rooms concentration climbs: 1000 ppm is the common comfort guideline, around 2000 ppm most people report stuffiness and fading attention, though occupational limits sit at 5000 — meaning drowsiness ambushes decision quality long before danger. Controlled experiments at Lawrence Berkeley National Laboratory and University College London show complex strategy scores dropping significantly at elevated levels. Fix by supplying roughly thirty cubic meters of fresh air per person per hour or wiring CO2 sensors to ventilation — do not wait for your nose; it cannot smell oxygen debt.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-11-04
来源 · Source
Satish 等,《Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance》,Environmental Health Perspectives,2012 (DOI: 10.1289/ehp.1104789)
Satish et al., 'Is CO2 an Indoor Pollutant? Direct Effects of Low-to-Moderate CO2 Concentrations on Human Decision-Making Performance', Environmental Health Perspectives, 2012, DOI: 10.1289/ehp.1104789
独立核验依据 · Independent verification: 核验依据 1 Crossref DOI 10.1289/ehp.1104789
#室内空气质量 #二氧化碳浓度 #新风量
数据中心为什么开始泡在水里冷却?液冷比风冷强在哪?
Why are data centers diving into liquid cooling — what beats air?
芯片功率密度逼近每平方厘米百瓦,风扇吹风的散热极限约为每平方米数千瓦,再往上只能靠液体。冷板式液冷把水路贴到CPU与GPU上,带走同等热量所需流量仅为风的百分之一量级,且允许更高的进水温度,机房可省去大部分空调、用自然冷源全年运行,PUE从1.5压到1.1附近。浸没式更彻底:整台服务器泡进介电油里。附带红利是余热回收——45度回水正适合区域供暖,北欧已有城市片区靠数据中心余热供暖。
Chip power density approaches a hundred watts per square centimeter, while fan-driven air tops out near kilowatts per square meter — only liquid goes further. Cold plates pipe water directly onto CPUs and GPUs, moving equal heat with about one-hundredth of the flow, tolerating warmer inlet water so most CRAC units vanish and free cooling runs year-round, pushing PUE from 1.5 toward 1.1. Immersion goes further, bathing whole servers in dielectric oil. A bonus: forty-five-degree return water suits district heating — districts of Nordic cities already warm themselves on data-center heat.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
ASHRAE TC 9.9,《Thermal Guidelines for Data Processing Environments》第5版,ASHRAE,Atlanta,2021
ASHRAE TC 9.9, Thermal Guidelines for Data Processing Environments, 5th ed., ASHRAE Datacom Series, Atlanta, 2021
独立核验依据 · Independent verification: 核验依据 1 ISBN 9781947192645 (2021)
#液冷 #PUE #余热回收
空调既能把屋里吹凉又能把热量排到更热的室外,它违反热力学吗?
An air conditioner cools rooms and dumps heat into hotter outdoors — does that violate thermodynamics?
不违反,因为它是热泵而非热量的单向搬运工。制冷循环四步:压缩机把低压气态制冷剂压成高温高压气体;冷凝器中向室外空气放热凝结成液体;膨胀阀骤然降压降温;蒸发器在室内侧沸腾吸热,带走房间热量。电力的作用不是制造冷,而是把热量从低温处泵到高温处——这正是热力学第二定律允许的,功就是过路费。能效比COP可达3到5,远超电阻加热,同一原理反过来用就是冬天供暖的空气源热泵。
No — a heat pump moves heat rather than making cold. Four steps: the compressor squeezes low-pressure refrigerant gas into hot high-pressure gas; the condenser dumps its heat outdoors as it condenses; the expansion valve drops pressure and temperature; the evaporator boils it indoors, absorbing room heat. Electricity pays the toll for pumping heat against its gradient, exactly what the second law permits. Coefficients of performance reach three to five — one kilowatt-hour moves three to five worth of heat, beating resistive heating; run in reverse, it becomes a winter air-source heat pump.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
ASHRAE,《Handbook — Fundamentals》,ASHRAE Atlanta,2021
ASHRAE Handbook — Fundamentals, ASHRAE, Atlanta, 2021
独立核验依据 · Independent verification: 核验依据 1 ISBN 9781947192898 (2021)
#热泵 #制冷循环 #能效比