Psychometric calculator

Psychometric calculator

Program that allows you to trace all the values ​​of humid air starting from temperature and relative humidity – The temperature can be indicated in degrees Celsius (°C) or Fahrenheit (°F) – The air flow can be indicated in m3/ h or CFM – Also excellent for determining the dew point temperature of refrigerated floors.

In the vast panorama of thermal engineering, energy design and air conditioning (but not only), psychrometric analysis plays a fundamental role. Humid air, with its complex and interconnected properties, plays a crucial role in a wide range of industrial and domestic applications. That's why Itieffe is pleased to present you the “Psychrometric Calculator”, an innovative and powerful tool designed to simplify and enrich your approach to humid air analysis.

Understanding relative humidity, enthalpy, air temperature, and other psychrometric parameters is essential for designing efficient cooling systems, evaluating the performance of humidification and dehumidification devices, and optimizing the energy efficiency of buildings. However, psychrometric analysis can often be complex and challenging, requiring elaborate formulas and detailed calculations.

This is where the “Psychrometric Calculator” comes into play. This program was created to make moist air analysis accessible to everyone from seasoned professionals to students and enthusiasts. Thanks to an intuitive interface and an efficient calculation system, the Psychrometric Calculator allows you to explore scenarios, solve problems and make informed decisions quickly and efficiently.

Humid air psychrometric calculator

We will walk you through some of the key features and benefits of the Psychrometric Calculator:

  1. Ease of Use: The very simple to use interface will allow you to easily enter input data and obtain accurate results in just a few steps. No matter your experience level, the Psychrometric Calculator will effortlessly walk you through moist air analysis.
  2. Instant Results: Complex psychrometric calculations will be performed in moments, instantly providing you with the information you need to make informed decisions and address specific challenges.
  3. Adaptability to Different Applications: Whether you are involved in the design of air conditioning systems, humidity control in industrial processes or the evaluation of the thermal performance of a building, the Psychrometric Calculator is a versatile tool that adapts to your needs.
  4. Supporting Learning: Students and newcomers to the field of thermal engineering will find the Psychrometric Calculator a reliable companion for exploring and understanding psychrometric concepts in a practical way.
  5. Optimization of Solutions: By exploring different options through simulations and analyses, you will be able to optimize solutions and strategies to improve the efficiency and sustainability of your projects.

We are excited to make the “Psychrometric Calculator” tool available to you and hope it will become a valuable ally in your professional and academic journey. Whether you are an engineer, student, technician or enthusiast, we invite you to take full advantage of this program's capabilities to explore the fascinating and complex world of humid air and its practical implications.

Humid air psychrometric calculator

To perform calculations of the mixture values ​​of two masses of air with different flow rates and values.

Elaborate that allows to trace all the values ​​of humid air starting from temperature and relative humidity. The temperature can be indicated in degrees Celsius (° C) or Fahrenheit (° F).

Psychrometry (from the Greek: ψυχρόν, cold and μέτρον, measure) means the study inherent in the determination of the properties of a gas-vapor system.

Concepts used in psychrometry.

Here is a list of some useful quantities in the field of psychrometry:
absolute humidity, relative humidity, specific humidity, vapor content, specific molar wet heat, dew point (in English: dew point), adiabatic saturation temperature (in English: adiabatic saturation temperature), wet bulb temperature (in English: wet bulb temperature). Source Wikipedia.

The principles of psychrometry are applied to any thermodynamic system that contains a gas-steam mixture, and in particular in the HVAC (heating, ventilating, and air-conditioning) and meteorological fields.

First indications

Temperature (° C - ° F), in degrees Celsius (centigrade) or Fahrenheit.

Relative humidity (%), expresses as a percentage the ratio between the amount of water vapor contained in an air mass and the maximum amount that it can contain in the same conditions of temperature and pressure. Relative humidity therefore provides information on how far a mass of air is from the saturation condition.

Absolute humidity (x), is the quantity of water vapor expressed in grams which is contained in cubic meter of air (or kilogram) to a certain temperature and pressure. Absolute humidity tends to increase with increasing temperature.

enthalpy (J), can be expressed in joules (International system) or in calories, it expresses the quantity of internal energy that a thermodynamic system can exchange with the environment.

In particular for a transformation:

  • isobar in which there is only mechanical work, the enthalpy variation is equal to the heat exchanged by the system with the external environment;
  • isochorobaric (at constant volume and pressure), the enthalpy variation coincides with both the heat (Q) and the internal energy variation (ΔU) that occurred during the process;
  • isobarentropic (at constant pressure and entropy), the change in enthalpy expresses the change in free energy. (Source Wikipedia)

Specific volume (V), is the volume occupied by moist air always referring to the kg of dry air.

Total pressure P of a gas mixture, expressed in millibars (mbar), corresponds to the sum of the partial pressures of the individual gases.

Partial pressure p of a gas expressed in millibar (mbar), is the pressure it would exert if it were alone in the vessel.

First indications (continued)

Dew temperature (° C), is the temperature at which the air reaches saturation conditions (UR = 100%). Condensation (dew) forms on each element (wall, glass surface etc.) which is at a temperature just below the dew point.

Wet bulb temperature (° C), is the ambient air temperature measured with a thermometer whose bulb is kept humid water gauze. interpolation of the temperatures achieved with a psychrometer (dry and wet bulb temperature meter) by means of the “Psychrometer table”It is possible to go back moisture relative (%).

air flow (Q in m³ / h), quantity of both external and internal air that is used.

Saturation, are the temperature and humidity values ​​to which the machine used to modify the parameters of the air mixture (transformation) is set. The lower the value, the more the quantity of air introduced into an environment (m³ / h) is the minimum necessary to cool it (introducing air into an environment at very low values, however, is neither hygienic nor economical). Obviously the temperature must be lower than that of the Dew Point.

Supply air, it is a reasonable temperature to send the air mixture into the circuit. Relative humidity is calculated automatically. It can coincide with SATURATION.

Pressure (hPa), modify this parameter with the real one, calculating that the wet bulb temperature varies with pressure variation.

Instructions

Instructions for using the psychrometric calculator

1) Choose the temperature measurement between Celsius (° C) and Fahrenheit (° F).

2) Set the outdoor temperature and relative humidity (see "External project temperatures"and "World project temperatures").

3) Enter the quantity of external air foreseen in m³ / h or in CFM (see "Outdoor air per person""Air changes per hour").

4) Set the desired room temperature (° C - ° F) and relative humidity (RH%).

5) Enter the quantity of recirculation air envisaged in m³ / h or in CFM.

By entering all that foreseen so far, the values ​​of the AIR MIXTURE (total air) are obtained.

Now you need to choose the temperature and relative humidity of our SATURATION point.

Finally, enter the temperature value for DELIVERY AIR (which can also coincide with the SATURATION point) the higher it is, the lower the relative humidity will be.

If the supply air temperature is high, there will be no dehumidification phenomena.

The wet bulb temperature varies with varying pressure. For this reason, the pressure (in hPa) relative to the site under consideration is entered.

Example

Let's fill in the highlighted boxes:

1) choose the temperature measurement - Celsius;

2) external temperature = 35 °C;

3) relative humidity = 60%;

4) once this is done, we can read all the humid air values ​​related to the choice of the initial parameters:

absolute humidity = 21,36 g/kg;

enthalpy in kcal/kg = 21,5;

enthalpy in kJ/kg = 89,8;

specific volume = 0,901 m³/h;

total pressure = 56,06 mbar;

partial pressure = 33,63;

dew point temperature = 26,05 °C;

wet bulb temperature = 28,25 °C;

(note: having done this, in many cases, the program has already done its duty and that is to find the values ​​of the thermohygrometric parameters linked to the initial data of temperature and humidity).

Let's continue with the data entry:

5) desired internal temperature = 26 °C;

6) relative humidity - 50%;

7) We choose the measure of air to be used between m³ / h or CFM (International or British system);

8) we enter the expected amount of external air - 1.000 m³ / h;

9) we introduce the expected amount of recirculated air - 3.000 m³ / h;

10) we can now read all the calculated values ​​for this specific mixture of humid air;

11) set the saturation temperature = 13 °C;

12) same thing for the relative humidity = 90%;

13) set the delivery air temperature = 15 °C (with this temperature, the air mixture will have a relative humidity of 79%);

14) lastly we can enter the pressure of the air mixture in hecto Pascal (1.013 hPa) which is needed exclusively for the calculation of the wet bulb temperature.

Easy?

good job

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Humid air psychrometric calculator

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