Psychrometric Calculator

- May 10, 2025
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Psychrometrics is the study of moist air properties and processes. This calculator helps you determine various properties of moist air including relative humidity, dew point, wet-bulb temperature, and more based on different input parameters.

Select your input parameters and the calculator will determine all other psychrometric properties of the air-water vapour mixture.

Select Input Parameters

Atmospheric Conditions

? The air temperature measured by an ordinary thermometer.
? Local atmospheric pressure. Standard atmospheric pressure at sea level is 101.325 kPa.
%
? The ratio of the partial pressure of water vapour to the equilibrium vapour pressure of water at a given temperature, expressed as a percentage.

Display Options

? If provided, barometric pressure will be estimated based on altitude. Otherwise, the entered barometric pressure will be used.

About Psychrometrics

Psychrometrics is the field of engineering concerned with the physical and thermodynamic properties of gas-vapour mixtures, particularly the mixture of air and water vapour.

Key Psychrometric Properties:
  • Dry-bulb Temperature: The temperature of air measured by an ordinary thermometer exposed to the air but not to direct solar radiation.
  • Wet-bulb Temperature: The temperature recorded by a thermometer with its bulb wrapped in wet cloth exposed to moving air. It is lower than dry-bulb temperature due to evaporative cooling.
  • Dew Point Temperature: The temperature at which air becomes saturated with water vapour (100% RH), causing condensation to occur.
  • Relative Humidity (RH): The ratio of the partial pressure of water vapour to the equilibrium vapour pressure at the current temperature.
  • Humidity Ratio: The mass of water vapour per unit mass of dry air (kg/kg), also known as specific humidity or mixing ratio.
  • Enthalpy: The total heat content of the air-vapour mixture per unit mass of dry air (kJ/kg).
  • Specific Volume: The volume occupied by a unit mass of dry air (m³/kg).
Common Applications:
  • HVAC Systems: Designing, analysing, and controlling heating, ventilation, and air conditioning systems.
  • Comfort Analysis: Determining indoor air conditions for human comfort.
  • Industrial Processes: Controlling air conditions for manufacturing, food processing, and material handling.
  • Meteorology: Analysing atmospheric conditions and predicting weather phenomena.
  • Building Science: Preventing condensation issues and designing building envelopes.
  • Agricultural Systems: Controlling greenhouse environments and storage conditions for crops.
Key Relationships:
  • At 100% relative humidity, the dry-bulb, wet-bulb, and dew point temperatures are all equal.
  • The difference between dry-bulb and wet-bulb temperatures (wet-bulb depression) indicates the humidity level.
  • Lower relative humidity creates a larger wet-bulb depression.
  • The dew point is always lower than or equal to the dry-bulb temperature.
  • Psychrometric calculations are pressure-dependent, so barometric pressure affects all derived properties.

Understanding Psychrometrics

Psychrometrics is all about the properties of moist air. It involves studying how air and water vapour interact. This knowledge is useful in many fields, from building design to weather forecasting. By grasping these principles, we can better manage temperature and humidity in different environments.

What is the Psychrometric Calculator?

The Psychrometric Calculator is a handy tool that helps you find various properties of moist air. Whether you want to know the relative humidity, dew point, or wet-bulb temperature, this calculator can do it all. Just enter your chosen parameters, and it will calculate the rest for you, making complex information easy to understand.

Selecting Your Input Parameters

When using the Psychrometric Calculator, you first need to choose input parameters. You can select combinations like dry-bulb temperature with relative humidity or wet-bulb temperature. Here are some examples of the combinations you can choose:

  • Dry-bulb + Relative Humidity
  • Dry-bulb + Wet-bulb
  • Dry-bulb + Dew Point
  • Dry-bulb + Humidity Ratio

Inputting Atmospheric Conditions

Next, you'll input the atmospheric conditions. This includes the dry-bulb temperature and barometric pressure. Additionally, you can enter values for relative humidity, wet-bulb temperature, dew point temperature, or humidity ratio. Each of these measurements plays a vital role in understanding the air's properties.

Understanding the Results

Once the calculations are complete, you’ll receive a range of results. These include dry-bulb temperature, relative humidity, and humidity ratio. You can also find secondary results like wet-bulb temperature and dew point. Insights from these results help you analyse air conditions comprehensively.

Visualising Psychrometric Properties

The calculator provides a visual representation of psychrometric properties. A chart illustrates the relationship between dry-bulb temperature, humidity ratio, and relative humidity. This visual tool aids in understanding how these properties interact and change under different conditions.

Applications of the Calculator

The Psychrometric Calculator has various practical applications. It can be beneficial in fields like HVAC, meteorology, and agriculture. Here are some specific areas where this calculator is used:

  • Designing heating and cooling systems.
  • Assessing comfort levels in indoor spaces.
  • Controlling humidity in agricultural settings.
  • Predicting weather patterns.

Getting Started with the Calculator

Using the Psychrometric Calculator is straightforward. You enter your selected parameters and atmospheric conditions. The calculator then quickly computes all relevant properties. This quick access to important data helps in making informed decisions in various applications.