CT-Natural
Windows Application

### CT-Natural

#### Graphical User Interface

Figure 2. Graphical User Interface for Demand Curves.

Input Variable Definition
WET-BULB TEMPERATURE Temperature of air wet-bulb entering the cooling tower
COOLING RANGE Difference between hot water temperature and cold water temperature
PRESSURE Total pressure referred to atmospheric
COEFFICIENT C Constant defined for a particular packing design
EXPONENT N Exponent defined for a particular packing design
Table 3. Definition of input variables in Demand Curves.

#### Range of Input Variables

Property Range in SI Units SI Units
WET-BULB TEMPERATURE 1.0 ≤ T ≤ 90.0 °C
COOLING RANGE 0.1 ≤ T ≤ 90.0 °C
PRESSURE 60000 ≤ P ≤ 110000 Pa
COEFFICIENT C 1.0 ≤ C ≤ 3.0 1
EXPONENT N -2.0 ≤ N ≤ -0.1 1
KaV/L 0.1 ≤ KaV/L ≤ 5.0 1
L/G 0.1 ≤ L/G ≤ 5.0 1
Approach 1.0 ≤ T ≤ 60.0 °C
Table 4. Full ranges of input variables in Demand Curves (SI Units).

Property Range in SI Units SI Units
WET-BULB TEMPERATURE 33.8 ≤ T ≤ 194.0 °F
COOLING RANGE 0.1 ≤ T ≤ 162.0 °F
PRESSURE 8.70226426 ≤ P ≤ 15.95415115 psia
COEFFICIENT C 1.0 ≤ C ≤ 3.0 1
EXPONENT N -2.0 ≤ N ≤ -0.1 1
KaV/L 0.1 ≤ KaV/L ≤ 5.0 1
L/G 0.1 ≤ L/G ≤ 5.0 1
Approach 1.0 ≤ T ≤ 140.0 °F
Table 5. Full ranges of input variables in Demand Curves (I-P Units).

#### Calculation Results

Figure 3. Numerical Results in a Demand Curves calculation project.

#### Introduction

Psychrometrics Calculator allows the calculation of physical properties of humid air, water, steam, ice and psychrometrics commonly used in the design and operation of cooling towers.

• Calculation of 42 properties of humid air, water, steam, ice and psychrometrics.
• Allows for 17 combinations of two thermodynamic properties to be entered as input variables:
• Dry-bulb Temperature / Wet-bulb Temperature
• Dry-bulb Temperature / Dew Point Temperature
• Dry-bulb Temperature / Relative Humidity
• Dry-bulb Temperature / Humidity Ratio
• Dry-bulb Temperature / Specific Enthalpy
• Dry-bulb Temperature / Specific Volume
• Wet-bulb Temperature / Dew Point Temperature
• Wet-bulb Temperature / Relative Humidity
• Wet-bulb Temperature / Humidity Ratio
• Dew Point Temperature / Relative Humidity
• Dew Point Temperature / Specific Enthalpy
• Dew Point Temperature / Specific Volume
• Relative Humidity / Humidity Ratio
• Relative Humidity / Specific Enthalpy
• Relative Humidity / Specific Volume
• Humidity Ratio / Specific Enthalpy
• Humidity Ratio / Specific Volume
• Supports input parameters and calculation results in both SI (metric) and I-P (english) system of units.
• For each combination of input thermodynamic variables, it calculates and provides the user with information about the appropriate values in the valid range of computations.
• Calculation results can be saved to a to a database for later retrieval.
• Calculation results can be exported to excel/pdf file formats.

Calculation of the properties of humid air, water, steam, ice and psychrometrics are based on the precision provided by the mathematical formulations of the following thermodynamic and transport properties models:

Properties of Water and Steam

• Formulations from the IAPWS (International Association for the Properties of Water and Steam) IAPWS-IF97 Industrial formulation (Revision 2007) and related models.

Properties of Humid Air

• Thermodynamic and psychrometric property algorithms from the ASHRAE Research Project 1485.
• Scientific Formulation IAPWS-95, IAPWS Formulation 2008 and IAPWS Formulation 2006. Properties of dry air are from the NIST Reference equation of Lemmon et al.

#### Graphical User Interface

Figure 1. Graphical User Interface in Psychrometrics Calculator.

#### Range of Input Variables

Property Range in SI Units SI Units
DRY-BULB TEMPERATURE -143.15 ≤ Tdb ≤ 350.0 °C
WET-BULB TEMPERATURE -143.15 ≤ Twb ≤ 350.0 °C
DEW POINT TEMPERATURE -143.15 ≤ Tdp ≤ 350.0 °C
RELATIVE HUMIDITY 0 .0 ≤ RH ≤ 100.0 [%]
HUMIDITY RATIO 0.0 ≤ W ≤ 10.0 kg/kg
SPECIFIC ENTHALPY -311.357 ≤ h ≤ 32135.848 kJ/kg
SPECIFIC VOLUME 1.469E-3 ≤ v ≤ 3.055E5 m3/kg
PRESSURE 10.0 ≤ P ≤ 10.0E6 Pa
Table 1. Full range of input variables in Psychrometrics Calculator (SI Units).

Property Range in I-P Units I-P Units
DRY-BULB TEMPERATURE -225.67 ≤ Tdb ≤ 662.0 °F
WET-BULB TEMPERATURE -225.67 ≤ Twb ≤ 662.0 °F
DEW POINT TEMPERATURE -225.67 ≤ Tdp ≤ 662.0 °F
RELATIVE HUMIDITY 0 .0 ≤ RH ≤ 100.0 [%]
HUMIDITY RATIO 0.0 ≤ W ≤ 10.0 lb/lb
SPECIFIC ENTHALPY -126.174 ≤ h ≤ 13823.61 Btu/lb
SPECIFIC VOLUME 2.353E-2 ≤ v ≤ 4.893E6 ft3/lb
PRESSURE 0.00145 ≤ P ≤ 1450.4 psia
Table 2. Full range of input variables in Psychrometrics Calculator (I-P Units).

#### Calculation Results

Property SI Units I-P Units
Dry-Bub Temperature °C °F
Wet-Bulb Temperature °C °F
Dew Point Temperature °C °F
Humid Air Pressure Pa, kPa, bar, mmHg psia, inHg, inH2O, atm
Water Vapor Partial Pressure Pa, kPa, bar, mmHg psia, inHg, inH2O, atm
Dry Air Partial Pressure Pa, kPa, bar, mmHg psia, inHg, inH2O, atm
Saturation Water Vapor Pressure Pa, kPa, bar, mmHg psia, inHg, inH2O, atm
Dry Air Mole Fraction [-] [-]
Water Mole Fraction [-] [-]
Dry Air Mass Fraction [-] [-]
Water Mass Fraction [-] [-]
Humidity Ratio kg(w)/kg(da), g(w)/kg(da) lb(w)/lb(da), gr(w)/lb(da)
Saturation Humidity Ratio kg(w)/kg(da), g(w)/kg(da) lb(w)/lb(da), gr(w)/lb(da)
Relative Humidity [%] [%]
Absolute Humidity kg(w)/m3 lb(w)/ft3
Parts per million by weight ppmw ppmw
Parts per million by volume ppmv ppmv
Enhancement Factor [-] [-]
Specific Volume of Dry Air m3/kg, cm3/g ft3/lb, in3/lb
Specific Volume of Humid Air m3/kg, cm3/g ft3/lb, in3/lb
Specific Volume of Saturated Water m3/kg, cm3/g ft3/lb, in3/lb
Specific Volume of Saturated Ice m3/kg, cm3/g ft3/lb, in3/lb
Specific Volume of Water Vapor m3/kg, cm3/g ft3/lb, in3/lb
Density of Dry Air kg/m3, g/cm3 lb/ft3, lb/in3
Density of Humid Air kg/m3, g/cm3 lb/ft3, lb/in3
Density of Saturated Water kg/m3, g/cm3 lb/ft3, lb/in3
Density of Saturated Ice kg/m3, g/cm3 lb/ft3, lb/in3
Density of Water Vapor kg/m3, g/cm3 lb/ft3, lb/in3
Specific Enthalpy of Dry Air J/kg, kJ/kg Btu/lb, ft lbf/lb
Specific Enthalpy of Humid Air J/kg, kJ/kg Btu/lb, ft lbf/lb
Specific Enthalpy of Saturated Water J/kg, kJ/kg Btu/lb, ft lbf/lb
Specific Enthalpy of Saturated Ice J/kg, kJ/kg Btu/lb, ft lbf/lb
Specific Enthalpy of Water Vapor J/kg, kJ/kg Btu/lb, ft lbf/lb
Specific Entropy of Dry Air J/(kg·K), kJ/(kg·K) Btu/(lb·°R), ft lbf/ (lb·°R)
Specific Entropy of Humid Air J/(kg·K), kJ/(kg·K) Btu/(lb·°R), ft lbf/ (lb·°R)
Specific Entropy of Saturated Water J/(kg·K), kJ/(kg·K) Btu/(lb·°R), ft lbf/ (lb·°R)
Specific Entropy of Saturated Ice J/(kg·K), kJ/(kg·K) Btu/(lb·°R), ft lbf/ (lb·°R)
Specific Entropy of Water Vapor J/(kg·K), kJ/(kg·K) Btu/(lb·°R), ft lbf/ (lb·°R)
Specific Internal Energy of Dry Air J/kg, kJ/kg Btu/lb, ft lbf/lb
Specific Internal Energy of Humid Air J/kg, kJ/kg Btu/lb, ft lbf/lb
Specific Isobaric Heat Capacity of Humid Air kJ/(kg·K) Btu/(lb·°R)
Compressibility of Humid Air [-] [-]
Table 3. Properties and their units calculated in Psychrometrics Calculator.

CT-Natural - Introduction (2:12)

CT-Natural - Demand Curves (Part I) (5:26)

CT-Natural - Natural Draft (Part I) (4:28)

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