thermodynamics

On [a] psychrometric chart, this process is represented as [a] line sloping downward and to the left. This process is assumed to occur as simple cooling first and then condensation. While the moisture is condensing the air is assumed to remain saturated.

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CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

Determine the total, sensible and latent cooling required cooling 20,000 cfm of air from a temperature of 90 F and a relative humidity of 60% to a temperature of 55 F and 100% relative humidity.

Source

CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

Hot humid day 90°F and 90% RH. Condition the air to 70°F at about 50% RH. Chill the air to condense out enough moisture to dehumidify it: goal is air with absolute humidity not exceeding 0.008 lbs of moisture per pound of air. Show processes.

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CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

How much moisture is added to 20 lb of air going from 50°F, 50% RH to 80°F, 60% RH?

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CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

Determine the amount of sensible heat needed to increase the temperature of air from 50°F and 50% RH to 90°F.

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CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

Ninety cubic-ft of lumber is dried at 140°F 'tdb' and 125.6°F 'twb'. The drying rate of the lumber is 5.68 lb of water per hour. If outside air is at 80.6°F 'tdb' and 80% relative humidity how much outside air is needed per min to carry away the moisture?

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CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

Determine the cooling required to sensibly cool 20,000 cfm of air from a temperature of 90 F and a relative humidity of 60% to a temperature of 75 F.

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CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

Calculate the amount of sensible heat that must be added to 100lb of air at 85°F dry bulb and 75°F wet bulb to raise the temperature of air to 100°F dry bulb.

Source

CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

The dry bulb reading is 85°F and the wet bulb is 60F. Using the chart determine the following values. Using the chart determine the following values: Relative humidity; Dew Point; Absolute humidity; Specific volume; [Specific] enthalpy.

Source

CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

The dry bulb reading is 70°F and the wet bulb is 54°F. Using the chart determine the following values. Using the chart determine the following values: Relative humidity; Dew Point; Absolute humidity; Specific volume; [Specific] enthalpy.

Source

CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

The dry bulb reading is 78°F and the wet bulb is 58°F. Using the chart determine the following values: Relative humidity; Dew Point; Absolute humidity; Specific volume; [Specific] enthalpy.

Source

CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

An air-conditioned room at sea level has an indoor design temperature of 75°F and a relative humidity of 50%. Determine the humidity ratio, enthalpy, density, dew point, and thermodynamic wet bulb temperature of the indoor air at design condition.

Source

CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

A sling psychrometer gives a dry-bulb temperature of 78°F and a wet-bulb temperature of 65°F. Determine other moist air properties from this information.

Source

CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

Heat released by a system into its surroundings is by convention a negative quantity (Q < 0); when a system absorbs heat from its surroundings, it is positive (Q > 0).

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Webel: Psy/MPsy: Psychrometrics for Mathematica: CONVENTION: 'Q' as a quantity symbol in equations indicates the energy GAINED BY the system as heat energy transfer; 'W' indicates the work DONE BY the system on its external surroundings.

In thermodynamics, heat is defined as the form of energy crossing the boundary of a thermodynamic system by virtue of a temperature difference across the boundary

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Defined quantitatively, the heat involved in a process is the difference in internal energy between the final and initial states of a system, and subtracting the work done in the process. This is the formulation of the first law of thermodynamics.

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Heat is energy in transfer to or from a thermodynamic system, by a mechanism that involves the microscopic atomic modes of motion or the corresponding macroscopic properties.

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A thermodynamic system does not contain heat. Nevertheless, the term is also often used to refer to the thermal energy contained in a system as a component of its internal energy and that is reflected in the temperature of the system.

Source

CED Engineering course PDF: 'Air Conditioning Psychrometrics (A.Bhatia)'

TRAIL: Air Conditioning Psychrometrics (vs CED Engineering course): Example results (only) in Mathematica and SysML using the Webel Psy package and MPsy class

Jump to first slide

Example 01: Values from 'tdb' and relative humidity 'r'

Sections

HVAC&R Zone

Keywords

Keywords

This zone presents some reference information on Heating, Ventilation, Air-Conditioning, and Refrigeration (HVAC&R), including some worked examples in Mathematica and SysML models.

CoolProp: HOWTO reproduce a pressure vs specific enthalpy chart in Mathematica. Example: R32 refrigerant.

CoolProp: LIMITATION: DOES NOT accept specific enthalpy 'H' and vapor quality 'Q' as input pairs

CoolProp zone

Keywords

Keywords

CoolProp is a handy free open source replacement (or stand-in) for NIST's commercial RefProp. However, CoolProp has some quirks, some of which are recorded here.

The Boltzmann constant is defined to be exactly 1.380649×10^(−23) J⋅K^(−1)

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As part of the 2019 redefinition of SI base units, the Boltzmann constant is one of the seven "defining constants" that have been given exact definitions. They are used in various combinations to define the seven SI base units.

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When calibrated to ITS-90, where one must interpolate between the defining points of gallium and indium, the boiling point of VSMOW water is about 10 mK less, about 99.974 °C.

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Precise measurements show that the boiling point of VSMOW water under one standard atmosphere of pressure is actually 373.1339 K (99.9839 °C) when adhering strictly to the two-point definition of thermodynamic temperature.

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Fun fact: The normal boiling point of water isn't exactly 100 °C (at least not since 2019 when the definition of the Kelvin scale was changed to use the Boltzmann constant and decoupled from the triple point of water)

Mathematica: TIP: The ThermodynamicData function of Mathematica uses NIST's RefProp under the hood.

MultiDomainControl

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

07. Components [MOST]

Slide kind

SysML Block Definition Diagram (BDD)

SysML Parametric Diagram

AmbientConvectionCapacitance (combined)

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

07. Components [MOST]

Slide kind

SysML Block Definition Diagram (BDD)

SysML Internal Block Diagram (IBD)

Cooling

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

07. Components [MOST]

Slide kind

SysML Block Definition Diagram (BDD)

SysML Internal Block Diagram (IBD)

AmbientCondition

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

07. Components [MOST]

Slide kind

SysML Block Definition Diagram (BDD)

SysML Internal Block Diagram (IBD)

SysML Parametric Diagram

Convection

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

07. Components [MOST]

Slide kind

SysML Block Definition Diagram (BDD)

SysML Internal Block Diagram (IBD)

SysML Parametric Diagram

CoolingToAmbient

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

07. Components [MOST]

Slide kind

SysML Block Definition Diagram (BDD)

SysML Internal Block Diagram (IBD)

SysML Parametric Diagram

ThermalCapacitance - Adiabatic

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

07. Components [MOST]

Slide kind

SysML Block Definition Diagram (BDD)

SysML Internal Block Diagram (IBD)

SysML Parametric Diagram

Thermal Connectors

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

07. Components [MOST]

Slide kind

SysML Block Definition Diagram (BDD)

SysML Internal Block Diagram (IBD)

Webel vs SysPhS-1.1: Suggest SysPhSLibrary should support Heat and FlowingHeat as conserved quantities with HeatFlowElement interface block and HeatFlowRate value type.

In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter.

Source

SimpleDomains - Thermal

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

Slide kind

SysML Block Definition Diagram (BDD)

SysML Internal Block Diagram (IBD)

Hysteresis - ChatteringControl

Gallery

Tutorial

TRAIL: SysML+SysPhS vs Modelica By Example in MagicDraw/Cameo SysML [tested with the Wolfram SystemsModeler for Modelica]

Section

02. Discrete Behavior

Slide kind

SysML Block Definition Diagram (BDD)

SysML Parametric Diagram

Export to Modelica and execution of the SysML/SysPhS block HumidifierSystem_S1

Gallery

Tutorial

TRAIL: SysPhS-1.1 Annex A examples in MagicDraw/Cameo SysML vs Modelica (Wolfram SystemsModeler)

Section

Annex A.5: Humidifier (with Units)

Slide kind

The enthalpy of vaporization of Water at 100 deg C = 2257 (J/g)

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The enthalpy of vaporization is often quoted for the normal boiling temperature of the substance.

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The enthalpy of vaporization is a function of the pressure at which that transformation takes place.

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The enthalpy of vaporization (symbol ∆Hvap), also known as the (latent) heat of vaporization or heat of evaporation, is the amount of energy (enthalpy) that must be added to a liquid substance to transform a quantity of that substance into a gas.

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Webel vs SysPhS-1.1: Annex A.5: Humidifier: Dimensional analysis of TemperatureIncrease and EvaporationCalculation implies the 'specificHeat' is a volumetric heat capacity, not a specific heat capacity (heat capacity per unit of mass).

The volumetric heat capacity can also be expressed as the specific heat capacity (heat capacity per unit of mass, in J/K/kg) times the density of the substance (in kg/L, or g/mL).

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The SI unit of volumetric heat capacity is joule per kelvin per cubic meter, J/K/m3 or J/(K·m3).

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Informally, it is the amount of energy that must be added, in the form of heat, to one unit of volume of the material in order to cause an increase of one unit in its temperature.

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The volumetric heat capacity of a material is the heat capacity of a sample of the substance divided by the volume of the sample.

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Isobaric volumetric heat capacity C(P,v) J⋅cm−3⋅K−1 of liquid Water at 100 °C = 4.2160

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Isobaric volumetric heat capacity C(P,v) J⋅cm−3⋅K−1 of liquid Water at 25 °C = 4.1796

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