Psychrometric software
Psychrometric Air-Conditioning calculation (Android): a PsychroAC
calculate and plot air-conditioning cooling & dehumidification pyschrometric process; with precool air unit, heat pipe, run-around coil, heat recovery unit . . .
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Go to a PsychroAC module:
more calculation EXAMPLES . . . in psychrometric air-conditioning
The following design calculations are done with aPsychroAC program.
Worked Example 5 - Operating Room 100% OA + Heat Recovery System (in IP units)
Given the following design information for an Operating Room of approx. 430 ft2 x 10 ft high:
RSH = 8.19 MBtu/hr.
RLH = 1.6 MBtu/hr.
Summer outdoor conditions = 100 oF DB, 74 oF WB.
Room design conditions = 62 oF DB, 55% RH.
OA ventilation airflow = 100% outdoor air (one pass system).
Use Enthalpy Wheel heat recovery device to pre-cool the OA.
Room air-change/hr to be about 15.
Ignore heat gain from suppy air fan motor.
1st Step Calculation:
Conditioned Air (CA) from HRW
Heat Recovery Wheel Calculations
=======================
*** Inputs ***
Sensible Effectivenss (%) = 73
Total Effectivenss (%) = 69
OA Airflow (CFM) = 1050 (100% OA to room)
OA Tdb (°F) = 100
OA Twb (°F) = 74
EA Airflow (CFM) = 1050 (100% exhaust from room)
EA Tdb (°F) = 62
EA RH (%) = 55
*** Results ***
Sensible recovery (MBtu/hr) = 31.3
Latent recovery (MBtu/hr) = 17.7
Total recovery (MBtu/hr) = 49.0
Total recovery (Ton) = 4.1
SA (CA) airflow (CFM) = 1050.0
----@ OA point----
Tdb = 100.0
RH = 29.4
w = 0.0120
m = 78.7
h = 37.31
----@ SA (CA) point----
Tdb = 72.3 (result export to AHU)
RH = 50.8 (result export to AHU)
w = 0.0086
m = 78.7
----@ EA in point----
Tdb = 62.0
RH = 55.0
w = 0.0065
m = 78.7
h = 21.93
----@ EAout point----
Tdb = 89.7
RH = 33.5
w = 0.0100
m = 78.7
h = 32.54
------------------------------
OA = Outdoor Air
EA = Exhaust Air
SA = Supply Air
CA = Conditioned Air
Tdb = Dry bulb temp., °F
RH = Relative humidity, %
w = Moisture content, lb/lb
m = Mass flow rate, lb/min
h = Enthalpy, Btu/lb
2nd Step Calculation:
AHU with CA imported from HRW
Psychrometric Air-conditioning Process Calculations
=======================
*** Inputs ***
SA Temp approach
100% OA system
SA Temp (°F) = 55
RSH (MBtu/hr) = 8.19
RLH (MBtu/hr) = 1.6
OA Tdb (°F) = 72.3 (CA imported from HRW)
OA RH (%) = 50.8 (CA imported from HRW)
RA Tdb (°F) = 62
RA RH (%) = 55
Coil ADP (°F) = 43.5
*** Results ***
Coil ADP (°F) = 43.5
Coil BF = 0.08
Coil sensible (MBtu/hr) = 31.0
Coil total load (MBtu/hr) = 43.4
Coil total load (Ton) = 3.6
OA sensible (MBtu/hr) = 12.1
OA total load (MBtu/hr) = 22.8
GSHF = 0.715
OA airflow (CFM) = 1088
SA Airflow (CFM) = 1048.8
SA temperature (°F) = 55.0
Supply Fan load (MBtu/hr) = 0.0
Reheat (MBtu/hr) = 10.8
----@ OA point----
Tdb = 72.3
RH = 50.8
w = 0.0086
m = 80.0
h = 26.71
----@ RA point----
Tdb = 62.0
RH = 55.0
w = 0.0065
m = -
h = 21.93
----@ MA / on coil point----
Tdb = -
RH = -
w = -
m = -
h = -
----@ off coil point----
Tdb = 45.8
RH = 94.8
w = 0.0062
m = 80.0
h = 17.66
------------------------------
OA = Outdoor Air
RA = Room / Return Air
MA = Mixed Air
Tdb = Dry bulb temp., °F
RH = Relative humidity, %
w = Moisture content, lb/lb
m = Mass flow rate, lb/min
h = Enthalpy, Btu/lb
Comments:
The above example illustrates the function of import CA from HRW to AHU.
Notes:
1) In HRW calculation, Standard Airflow option is used for the purpose of this calculation.
2) In AHU calculation, Reheat option is turn-on with coil ADP set at 43.5 oF.
3)The above example shall not be taken as the only solution approach. There are various design approaches available. You can "play" with various design input parameters with just a few clicks in aPsychroAC.
4) The coil ADP at 43.5 oF is fairly low. DX system or 39 oF chiller system is feasible.
Worked Example 5 - Operating Room Schematic (for illustration only)
Worked Example 5 - psychro chart plot for Heat Recovery Wheel (HRW)
Worked Example 5 - psychro chart plot for AHU
