A psychrometric chart presents physical and thermal properties of moist air in a graphical form. It can be very helpful in troubleshooting and finding solutions to greenhouse or livestock building environmental problems.
What is the purpose of a PUD? problems with planned unit development.


What is psychrometric chart in HVAC?

Psychrometric chart is one of the chart that is commonly used in solving HVAC problems. The properties of air such as wet bulb temperature, dry bulb temperature, dew point temperature, relative humidity, humidity ratio, specific enthalphy and specific volume are shown on this chart.

How is a psychrometric chart helpful for understanding human comfort?

A psychrometric chart for a given location can tell you information about temperature (wet bulb and dry bulb) and humidity (relative and absolute). … Psychrometric charts show temperature vs. humidity, and can be used to express human thermal comfort, design strategies, and energy requirements for those strategies.

Is psychrometric chart accurate?

While this method is not accurate enough for laboratory calculations, it is useful for field calculations using the psychrometric chart, where extreme accuracy is not of prime importance. On most psychrometric charts space is limited so that only the total heat content of the air is shown.

What is psychrometric process?

a psychrometric process that involves the increase or decrease in the temperature of air without changing its humidity ratio. Example: passing moist air over a room space heater and of kiln air over the heating coils.

Which physical property does the psychrometric chart not represent?

Hence partial vapour pressure is not shown on psychrometric chart.

What is the range of DBT on the psychrometric chart usually used?

What is the range of DBT on the psychrometric chart usually used? Explanation: Generally, the temperature range of dry bulb temperature lines on the psychrometric chart is from -6 to 45°C. These lines are drawn with a difference of every 5°C of DBT.

Where is the dew point on a psychrometric chart?

Vapor pressure is measured in units of mercury. For this specific graph, it is measured in inches of mercury. The dew point is represented on the chart by Point 3. The dew point is measured vertically and usually measured in degrees Fahrenheit or degrees Celsius, on this chart it is measured in Fahrenheit.

What is the comfort zone on a psychrometric chart?

One of the major applications of the Psychrometric Chart is in air conditioning, and we find that most humans feel comfortable when the temperature is between 22°C and 27°C, and the relative humidity φ between 40% and 60%. This defines the “comfort zone” which is portrayed on the Psychrometric Chart as shown below.

How do you plot a comfort zone on a psychrometric chart?

  1. Find the annual mean temperature, Tav. …
  2. Find the thermal neutrality (Tn) …
  3. Find the lower (L) and upper (U) limits of Tn. …
  4. Find the SET slope expressions. …
  5. Find the base line intercepts for L and U from the SET slope expressions.
What is a psychrometric chart and how is it developed explain any five psychrometric processes and represent them on a psychrometric chart?

A Psychrometric chart graphically represents the thermodynamic properties of moist air. Standard psychrometric charts are bounded by the dry-bulb temperature line (abscissa) and the vapour pressure or humidity ratio (ordinate). The Left Hand Side of the psychrometric chart is bounded by the saturation line.

What do you understand by adiabatic humidification show the process on psychrometric chart?

Adiabatic humidification injects water (not steam) directly into the air using a spray mechanism or wetted medium, and the heat from the surrounding air causes the water to evaporate. So instead of sliding up the vertical dry bulb temperature line on the psychrometric chart, we move diagonally up the wet bulb line.

What are the components of psychrometric chart?

  • Dry Bulb (DB) Temperature Lines: The dry bulb temperature scale is shown along the base of the shoe shaped psychrometric chart forming the sole. …
  • Moisture Content: …
  • Wet Bulb (WB) Temperature Lines: …
  • Dew Point (DP) Temperature Lines:
What are psychrometric chart and steam tables and how are these used?

Psychrometric charts are complex graphs that can be used to assess the physical and thermodynamic properties of gas-vapour mixtures at a constant pressure. They are often used to assess the properties of moist air.

How do you plot points on a psychrometric chart?

Take a ruler and draw a vertical line at the dry bulb temperature of 70 and draw a horizontal line where the dew point is 50. The point where these two lines intersect is known as a ‘state point’. Plot the state point and you can also read the rel- ative humidity, wet bulb, enthalpy, vapor pressure and humidity ratio.

Can psychrometric chart wet bulb temperature lines are?

Concept: Every psychometric chart includes vertical lines that represent the dry bulb temperatures, diagonals line represents wet bulb temperature and curved lines represent relative humidity.

What is sensible heat factor and what does it represent on psychrometric chart?

Sensible Heat Factor – The ratio of sensible to total heat. Alignment Circle – Located at 24°C DB and 50% RH and used in conjunction with the sensible heat factor to plot the various air conditioning process lines. Kilograms of Dry Air – The basis for all psychrometric calculations.

Who invented the psychrometric chart?

Willis Carrier is known as the Father of Air Conditioning. He also invented the psychrometric chart. It was a result of his research studying the effects of heat and humidity on heat and cooling comfort.

What is psychrometric chart Mcq?

Concept: Every psychometric chart includes. vertical lines that represent the constant dry bulb temperatures, The diagonal lines that represent wet bulb temperature and enthalpy. curved lines that represent relative humidity.

What is DBT and WBT in psychrometric chart?

Knowing both the dry-bulb temperature (DBT) and wet-bulb temperature (WBT), one can determine the relative humidity (RH) from the psychrometric chart appropriate to the air pressure.

What does the curved lines on a psychrometric chart indicates *?

Psychrometry is the study of the properties of mixtures of air and water vapor. Curved lines represent relative humidity.

Which of the following denotes dehumidification process on the psychrometric chart?

Explanation: Psychrometric chart has DBT on the x-axis and sp. Humidity on the y-axis. So, if a process is going down on the chart, then there is a decrease in relative as well as specific humidity. So, the vertical line with an arrow downwards denotes dehumidification process.

Why is the dew point important?

The dew point is the temperature the air needs to be cooled to (at constant pressure) in order to achieve a relative humidity (RH) of 100%. … The higher the dew point rises, the greater the amount of moisture in the air. This directly affects how “comfortable” it will feel outside.

How do you interpret dew point?

The higher the dewpoint is, the more moisture that is in the air. The higher the dewpoint is above 65 F, the stickier it will feel outside (feels like you have to breathe in a bunch of moisture with each breath). 75 F or above dewpoint, the air really feels sticky and humid.

What does humidity 70% mean?

However, when the air is already saturated with water vapor (as it is when humidity levels rise to 70 percent and higher), sweat can’t evaporate. So instead of cooling down, you just feel hotter and stickier. At that point, the body is forced to resort to other means to try to cool off.

How do you read absolute humidity on a psychrometric chart?

On the vertical line corresponding to the temperature of 20°C, we go up until we reach the 60% HR curve. Moving to the right until the end of the diagram we find the absolute humidity vertical line. This give us the information that our air contains 8.77 g of water vapor.

How do I create a psychrometric chart in Excel?

You can install the package as a plug-in in Microsoft Excel. Once installed, if you click on ‘insert function’ and select the ‘user-defined’ category. You can find a list of the available psychrometric functions: With this fantastic plug-in installed, plotting a psychrometric chart is straightforward.

What does the dry bulb temperature measure?

The Dry Bulb Temperature refers basically to the ambient air temperature. It is called “Dry Bulb” because the air temperature is indicated by a thermometer not affected by the moisture of the air.

What are two ways to increase relative humidity?

Relative humidity can be changed in two ways. One is by adding or subtracting water vapor. The second is by changing the air’s temperature.

What is comfort chart?

The Comfort Chart is a tool that helps operators determine how well air-handling equipment is providing thermal comfort for the building occupants or for a process within the facility.

What is the human comfort zone for temperature and humidity?

Humans generally feel comfortable between temperatures of 22 °C to 27 °C and a relative humidity of 40% to 60%.

What is psychrometric chart in HVAC?

Psychrometric chart is one of the chart that is commonly used in solving HVAC problems. The properties of air such as wet bulb temperature, dry bulb temperature, dew point temperature, relative humidity, humidity ratio, specific enthalphy and specific volume are shown on this chart.