The heating, ventilation, and air conditioning (HVAC）方程.
空气方程
速度
美国单位
or for standard air (d = 0.075 lb/cu ft)
解决“ D”：
V = Velocity (fpm)
Vp = Velocity Pressure (in. w.g.)
d = Density (lb/cu ft)
Pb = Absolute Static Pressure (in. Hg)
(Barometric pressure + static pressure)
T = Absolute Temp. (460° + °F)
公制单位
or for standard air (d = 1.204 kg/m3）
解决“ D”：
V = Velocity (m/s)
Vp = Velocity Pressure (Pascals or Pa)
d = Density (kg/m3）
Pb = Absolute Static Pressure (kPa)
(Barometric pressure + static pressure)
T = Absolute Temp. (273° + °C = °K)
热流
美国单位
Q (sens.) = 60 x Cp XDX CFMXΔT
or for standard air (Cp = 0.24 BTU/LB - °F）：
Q (sens.) = 1.08 x cfm x Δt
Q (lat.) = 4750 x cfm x ΔW (lb.)
Q (lat.) = 0.67 x cfm x ΔW (gr.)
Q (total) = 4.5 x cfm x Δh
q = a x uxΔt
R = 1/U
Q=Heat Flow (Btu/hr)
Cp = Specific Heat (Btu/lb · °F)
d = Density (lb/cu ft)
At = Temperature Difference (°F)
AW = Humidity Ratio (lb or gr H2O/LB干空气）
Ah = Enthalpy Diff. (Btu/lb dry air)
A = Area of Surface (sq ft)
U = Heat Transfer Coefficient (Btu/sq ft · hr * °F)
R = Sum of Thermal Resistances (sq ft· hr · °F/Btu)
P = Absolute Pressure (lb/sq ft)
V = Total Volume (cu ft)
T = Absolute Temp. (460° + °F = °R)
R = Gas Constant (ft/°R)
M = Mass (lb)
公制单位
Q (sens.) = 60 x Cp XDXL/SXΔT
or for standard air (Cp = 1.005 kJ/kg - °C）：
Q (sens.) = 1.23 x l/s x Δt
Q (lat.) = 3 x l/s x ΔW (lb.)
Q (total) = 1.2 x l/s x Δh
q = a x uxΔt
R = 1/U
Q=Heat Flow (watts or kW)
Cp = Specific Heat (kJ/kg – °C)
d = Density (kg/m3）
At = Temperature Difference (°C)
AW = Humidity Ratio (g H2O/kg干空气）
Ah = Enthalpy Diff. (kJ/kg dry air)
A = Area of Surface (m2）
U = Heat Transfer Coefficient (W/m2 . ℃)
R = Sum of Thermal Resistances (m2 . °C/W)
P = Absolute Pressure (kPa)
V = Total Volume (m3）
T = Absolute Temp. (273° + °C = °K)
R = Gas Constant (kJ/kg °R)
M = Mass (kg)
总压力
美国单位
TP = Vp + SP
CFM = A X V
TP = C x Vμ
TP = Total Pressure (in. w.g.)
Vp = Velocity Pressure (in. w.g.)
SP = Static Pressure (in. w.g.)
V = Velocity (fpm)
V米 = Measured Velocity (fpm)
d = Density (lb/cu ft)
A = Area of duct cross section (sq ft)
C =管道拟合损耗系数
公制单位
TP = Vp + SP
l/s = 1000 x a x v
TP = C x Vμ
TP = Total Pressure (Pa)
Vp = Velocity Pressure (Pa)
SP = Static Pressure (Pa)
V = Velocity (m/s)
V米 = Measured Velocity (m/s)
d = Density (kg/m3）
A = Area of duct cross section (m2）
C =管道拟合损耗系数
风扇方程
美国单位
CFM =每分钟立方英尺
rpm =每分钟旋转
P = Static or Total Pressure (in. w.g.)
必和制动马力
d = Density (lb/cu ft)
公制单位
I/S =每秒升
米3/s =每秒立方米
P = Static or Total Pressure (Pa)
kW =千瓦
d = Density (kg/m3）
泵方程
美国单位
gpm =每分钟加仑
rpm =每分钟旋转
D =叶轮直径
H = Head (ft. w.g.)
必和制动马力
水力等效物
- 一个。一加仑水= 8.33磅
- b. Specific heat (Cp) water = 1.00 Btu/lb °F (@ 68°F)
- c. Specific heat (Cp) water vapor = 0.45 Btu/lb °F (@ 68°F)
- d。一英尺的水= 0.433 psi
- e. One ft. of mercury (Hg) = 5.89 psi
- f。一个cu.ft。水= 62.4 lb = 7.49加仑。
- g. One in. of mercury (Hg) = 13.6 in.w.g. = 1.13 ft. w.g.
- h。大气压= 29.92英寸hg = 14.696 psi
- 我。一个psi = 2.31英尺wg = 2.04英寸
公制单位
I/S =每秒升
米3/s =每秒立方米
rad/s =每秒弧度
D =叶轮直径
H = Head (kPa)
BP =制动马力
水力方程
美国单位
gpm =每分钟加仑
Q = Heat flow (Btu/hr)
Δt = Temperature diff. (°F)
ΔP = Pressure diff. (psi)
Cv = Valve constant (dimensionless)
WHP =水马力
gpm =每分钟加仑
必和制动马力
H = Head (ft w.g.)
Sp. Gr. = Specific gravity (use 1.0 for water)
EP =泵的效率
NPSHA =可用的净正吸头
P一种 = Atm. press. (use 34 ft w.g.)
P小号 = Pressure at pump centerline (ft w.g.)
V2/2g = p点速度头小号 (ft w.g.)
PVP = Absolute vapor pressure (ft w.g.)
g = Gravity acceleration (32.2 ft/sec2）
h = Head loss (ft)
f = Friction factor (dimensionless)
L = Length of pipe (ft)
D = Internal diameter (ft)
V = Velocity (ft/sec)
在各种水温下，以汞的英寸为英尺转换压力
水温度
f f f |
60
∘
60
∘
60^(@) |
150
∘
150
∘
150^(@) |
200
∘
200
∘
200^(@) |
250
∘
250
∘
250^(@) |
300
∘
300
∘
300^(@) |
340
∘
340
∘
340^(@) |
英尺hg的头部差异。微分 |
1.046
1.046
1.046 |
1.07
1.07
1.07 |
1.09
1.09
1.09 |
1.11
1.11
1.11 |
1.15
1.15
1.15 |
1.165
1.165
1.165 |
公制单位
Q = Heat flow (kilowatts)
Δt = Temperature diff. (°C)
ΔP = Pressure diff. (Pa or kpa)
Cv = Valve constant (dimensionless)
米3/s =每秒立方米
l/s =每秒升
WP = Water power (kW) or (W)
米3/s =每秒立方米
I/S =每秒升
Sp. Gr. = Specific gravity (use 1.0 for water)
BP = Brake power (kW)
E，=泵的效率
H = Head (Pa) or (m)
NPSHA =可用的净正吸头
P一种 = Atm. press. (Pa – Std. Atm. press. = 101,325 Pa)
P小号 = Pressure at pump centerline (Pa)
V2/2g = p点速度头小号 (m)
PVP = Absolute vapor pressure (Pa)
g = Gravity acceleration (9.807 m/sec2）
h = Head loss (m)
f = Friction factor (dimensionless)
L = Length of pipe (m)
D = Internal diameter (m)
V = Velocity (m/sec)
电动方程
美国单位
I = Amps (A)
E = Volts (V)
PF =功率因数
R= ohms (Ω)
P = watts (W)
必和制动马力
公制单位
kW =千瓦
I = Amps (A)
E = Volts (V)
PF =功率因数
R = ohms (Ω )
P. = watts (W)
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