Resources

Software Resources

The following software is available for ThermalNetics customers. Please contact us for access.

McQuay

• Energy Analyzer
• Acoustic Analyzer
• Pipe Sizer
• Duct Sizer
• Psychrometric Analyzer

Neptronic

• Humidisoft Selection Software

Enviro-Tec

• Web-based selection software

Lennox

• DaveNet

 

Commonly Used HVAC Formulae and Conversions

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Air Side

Q_Total = CFM x (h_i - h_f) x 4.5 Btuh

Q_Sensible = CFM x (t_i - t_f) x 1.085 Btuh

Q_Latent = CFM x (Gr_i - Gr_f) x .068 Btuh

Humidification = CFM x (Gr_f - Gr_i) / 1,555 lbs/hr

CFM = l/s x 2.12

Air Pressure Drop (in. wg) = Pa / 249

 

Water Side

Q = USGPM x (t_i - t_f) x 500 Btuh

Q = USGPM x (t_i - t_f) x 450 Btuh (50% E.G.)

Q = USGPM x (t_i - t_f) / 24 Tons

USGPM = l/s x 15.85

Water Pressure Drop (ft. wg) = kPa x 0.335

1.0 PSI = 2.31 wg

7,000 Grains = 1.0 lb

 

Miscellaneous

1.0 Ton = 12 MBH = 12,000 Btuh

1.0 Therm = 100,000 Btuh = 100 MBH

COP = 3.516 / (kw / Ton)

EER = Tons x 12 / (Total kW input)

Btuh = Watt x 3.412

HP = kW x 1.3405

1 Boiler HP = 33.48 MBH

1 US Gallon = 8.33lbs

Latent heat of vaporization of steam in air (average) = 1,050 Btuh/lb

 

The Affinity Laws (Fan/Pump Laws)

`text(rpm)_(2)/text(rpm)_(1)=text(Flow)_(2)/text(Flow)_(1)`

`(DeltaP_(2))/(DeltaP_(1))=(text(Flow)_(2)/text(Flow)_(1))^(2)`

`"mhp"_2/"mhp"_1=("Flow"_2/"Flow"_1)^3`

`"Pump BHP"= ("USGPM " xx " Head (ft. wg)")/("3960 "xx" Pump Efficiency")`

`"Fan BHP"= ("CFM " xx " S.P. (inches wg)")/("6356 "xx" Static Efficiency")`

 

Air-Conditioning Formulas

1 Btu = amount of heat required to raise or lower temperature of one pound of water 1°F

1 ton refrigeration = 12,000 Btu/h = 200 Btu/min

1 watt = 3.412 Btu/h

1 horsepower = 2545 Btu/h

1 lb = 7000 grains

1 ft (head) = 0.433 psi

1 square foot EDR (equivalent direct radiation) = 240 Btu

1 boiler horsepower = 33,479 Btu/h

No. of air changes (N) =60 cfm/ft³

Sensible heat (Btu/h) = 1.08 `QDeltat`
Where `Deltat` = difference between entering and leaving dry-bulb temperature and `Q` = airflow rate in cubic feet per minute

Latent heat (Btu/h) = 0.68 `QDeltag`
Where `Deltag` = difference in moisture content of entering and leaving air, grains per pound of dry air

Water quantity (gpm) required for heating and cooling = q/500 `Deltat_(water)`
Where q = load in Btu/h

Chiller capacity (tons) = `"gpm (chilled water) " xx (Deltat_(water))/24`

For air:

1 lb/h = 4.5 Q

1 ton = `(QDeltah)/2670`

Fan HP = `("cfm " xx " static pressure" " (in. w.g.)")/("6356 " xx " Efficiency")xx"Density of air"/"Density of standard air"`

Small fans 0.40 – 0.50 efficiency
Large fan 0.55 – 0.60 efficiency

For water:

1 lb/h = 500 gpm

1 ton = (gpm) `(Deltat)/24`

Pump HP = `("gpm " xx " ft head")/("3960 " xx " Efficiency")xx" Specific gravity"`

Small pumps 0.40 – 0.60 efficiency
Large pumps 0.70 – 0.85 efficiency