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制冷·暖通空调
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制冷·暖通空调
12
engines
蒸气压缩制冷循环(COP)
Vapor-compression refrigeration cycle (COP)
蒸发/压缩/冷凝/节流 · COP=Qc/W · Carnot Tc/(Th−Tc)
Four components, two COPs: COP_cooling = Q_evap / W_comp, COP_heating = Q_cond / W_comp = COP_cooling + 1
制冷剂压焓图(P-h 图)
Refrigerant pressure–enthalpy (P–h) diagram
P-h图4状态点 · 饱和穹顶 · 制冷效应h1−h4 · COP=(h1−h4)/(h2−h1)
Four state points trace the cycle on the P–h plane: refrigerating effect = h₁ − h₄, work = h₂ − h₁, COP = (h₁ − h₄)/(h₂ − h₁)
过热与过冷
Superheat & subcooling
蒸发器出口过热保护压缩机 · 冷凝器出口过冷增制冷量
A few degrees of superheat at the evaporator exit protect the compressor; a few degrees of subcooling at the condenser exit raise capacity
制冷吨与冷量单位换算
Refrigeration ton & cooling-capacity units
1冷吨=12000BTU/h=3.517kW · 吨↔kW↔BTU/h · 选型
Convert cooling capacity between tons, kW and BTU/h, and size to a load
空调能效比 EER / SEER
Air-conditioner efficiency (EER / SEER)
EER=BTU/h每W · EER=3.412×COP · SEER季节 · 年能耗
EER = cooling BTU/h ÷ input W; higher is more efficient — estimate annual energy and cost
节流膨胀阀(等焓节流)
Expansion valve (isenthalpic throttling)
等焓节流h=const · 闪发气 · x=(h−hf)/hfg
Isenthalpic throttling (h constant) drops condenser pressure to evaporator pressure, producing flash gas
焓湿图(湿空气性质)
Psychrometric chart
干球/含湿量/RH/焓 · 状态点 · 25°C/50%→9.9g/kg,50.5kJ/kg
From dry-bulb temperature and relative humidity to humidity ratio and enthalpy, plotted as a state point
干湿球温度与湿度
Wet-bulb vs dry-bulb temperature
湿球vs干球 · 蒸发冷却 · 湿球差指示湿度 · 25/50%→WB18°C
Evaporative cooling lowers the wet-bulb reading; the depression (dry−wet) indicates humidity
冷负荷:显热与潜热分解
Cooling load: sensible & latent split
Q显=ṁcpΔT · Q潜=ṁh_fgΔw · SHR=Qs/(Qs+Ql)
The coil's heat removal splits into sensible (cooling) and latent (dehumidifying) parts; SHR gives their ratio
风机 / 水泵相似定律
Fan & pump affinity laws
流量∝N · 压头∝N² · 功率∝N³ · 降速20%省功49%
As speed changes: flow ∝ N, pressure ∝ N², power ∝ N³ — power follows the CUBE of speed
换气次数(ACH)与通风量
Air changes per hour (ACH) & ventilation
ACH=60·CFM/Vol=3600·(m³/s)/m³ · 办公4–10 · 新风
ACH = 3600·supply / room volume — how many times the whole room's air is replaced each hour
采暖度日与制冷度日(HDD / CDD)
Heating & cooling degree-days (HDD / CDD)
HDD/CDD=Σmax(0,T基−T均) · 基18°C · 能耗≈UA·DD·24
Degree-days = Σ (daily gap from a base temperature) × days — used to estimate seasonal energy