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for an example if supply air is3000 l/s or6000 cfm and return air is2700 l/s or5400 cfm how caan we find out TMBH (TOTAL MEGA BRITISH THERMAL UNIT PER HOUR) and SMBH (SENSIBLE MEGA BRITISH THERMAL UNIT PER HOUR )
You can find this through HAP or if you know the air condition i mean temperature DB and WB and RH and Humidity then you can find by Psychometric Chart
The sensible heat flow can be expressed in SI-units (metric) as
Qs = cp ρ q Δt /3600 (1)
where
Qs = sensible heat flow (kW)
cp = specific heat of air (kJ/kg K)
ρ = air density at standard conditions (kg/m3)
q = air flow (m3/hr)
Δt = temperature (oC)
In English (imperial) units the sensible flow heat can be expressed as
Qs=60 cp ρ q Δt =1.075 q Δt (2)
where
Qs = sensible heat flow (Btu/hr)
cp =0.2388 - specific heat (Btu/lboF)
ρ =0.075 - air density at standard conditions (lb/ft3)
q = air flow in (ft3/min)
Δt = temperature difference (oF)
LATENT HEAT
The latent heat flow can be expressed in English (Imperial) units as
Ql =60 hwe ρ q Δx (1)
where
Ql = latent heat flow (Btu/hr)
hwe =1060 - latent heat of vaporization of water (Btu/lb)
ρ =0.075 - air density at standard conditions (lb/ft3)
q = measured air flow (ft3/min)
Δx = humidity ratio difference (lb water/lb dry air)
The latent heat flow can be expressed in SI-units (metric) as
Ql = hwe ρ q Δx /3600 (2)
where
Ql = latent heat flow (kW)
hwe =2465.56 - latent heat of vaporization of water (kJ/kg)
ρ =1.202 - air density at standard conditions (kg/m3)
q = air flow (m3/hr)
Δx = humidity ratio difference (kg water/kg dry air)
And by adding both you will find total Heat
also u can use enthalpy instead of temperature or humidity in the same formula and it will give same result
TMBH= 4.5* CFM* (HI-H2)
WHERE H1= ENTHALPY AT COOLING COIL INLET
H2= ENTHALPY AT COOLING COIL OUTLET
ENTHALPY VALUES WE CAN CALCULATE FROM PSYCHOMETRIC CHART BY DRAWING GSHF AND RSHF LINES FOR SPECIFIC AIR CONDITIONING SYSTEM
SMBH= 1.08*TOTAL ROOM AIR CFM(T1-T2)
T1= ROOM SUPPLY TEMP
T2= ROOM DESIGN TEMP
SMBH = sensible cooling capacity in thousands of BTU's per hour.
TMBH= total cooling capacity in thousands of BTU's per hour.
Sensible Heat Calculation (at sea level): SMBH =1.* (CFM/) * (∆T air)
Total Heat Calculation (at sea level): TMBH =4.5 * (CFM/) * (∆h air)
as shown in equations and as per eng Muhammad Arsalan Siddiqui you have to get inlet and outlet air condition to use Psychometric Chart to get ∆h air then you can use the equation
as an estimation: (this calculation not accurate don't use it as final)
usually for FAHU one ton =toCFM take it asCFM that means total cooling load is around.5ton
for sensible load take outdoor temp. as.8F and the outlet temp..4F then ∆T air =.4F
the sensible heat will beBTU/HR =.1MBTU/HR which equal.ton
SMBH=(1.08)*OACFM*(TEMP OUT SIDE-TEMP ROOM )/1000
TMBH=4.5*CFM*(ENTHALPY OUTSIDE-ENTHALPY ROOM)/1000
Enthalpy values corresponding to the temperatures will get from the psychrometric chart...
if you know the cfm the simple formula is Q=M. X DELTA H
DELTA H can be obtained from psychometric chart that is H at inside temperate and H at out side temperature
and M. is the flow rate in m3 /hr
We know the ambient and room temperature as well
We can caiculate by using psychrometric chart and caculating the entalpy.
Sir I have much need calculate cfm and smbh but how
