HVAC introduction

HVAC-

HVAC stands for heating ventilation and air conditioning.

HEATING- 

To increase the temperature

VENTILATION- 

The process of supplying clean air and removing polluted air by natural or mechanical means to and from a particular space is called ventilation.

AIR-CONDITIONING- 

To make a comfort condition.

Air conditioning is defined as "the process of treatment of air. There or four important actions are involved in air conditioning.

A. Temperature

B. Humidity

C. Cleanness of air 

D. Air distribution

Now we describe all the point.

A. Temperature 

Human feel comfort in the range of 22 degree celcious to 26.5 degree celcious temperature.

B. Humidity 

For human comfort relative humidity lies between 30% to 70%.

C. Cleanness of air.

It's measure in grade or class.less grade means good quality air. Grade is depend upon particles which presents in a finite amount of air.

As like as 

1st class or grade 1.

Grade 2 

D. Air distribution

For human comfort the velocity of air lies between

5-8 meter per minute.

Femperature of any

Psychometric.

  The psychrometry is that branch of engineering science which deals with the study of moist air . 

Moist air is the mixture of air and water vapour. dry air mixed with water vapour or humidity. We study about some psychrometric term.

1. Dry air.

The pure dry air is a mixture of number of gases such as nitrogen (N2), oxygen(O2) , carbon dioxide (CO2), hydrogen(H2), argon(Ar), neon (Ne), helium (He) etc. but the nitrogen and oxygen have the major portion combination.

2. Wet air or moist air 

 It is a mixture of dry air and water vapour. The amount of water vapour, in the air, depends upon the absolute pressure and temperature of the mixture.

3. Saturated air 

It is a mixture of dry air and water vapour, when the air has mix up with amount of water vapour into at saturated conditioning. Means no more water vapour can add in this saturated air. The relative humidity of saturated air is 100%.

4. Degree of saturation.

 The ratio of actual mass of water vapour in a unit mass of dry air the mass of water vapour in the same mass of saturated dry air at the same temperature and pressure is called degree of saturation.

5. Humidity.  

 The mass of water vapour present in 1 kg of dry air, and is generally presented in terms of gram per kg of dry air (g/kg of dry air). It is also called specific humidity ratio.

It's represented by 'w'

         Mass of vapour (gm)
w=   / Mass of air (kg) 

6. Absolute humidity.

 Mass of water vapour present in 1 m³ of dry air,  the unit  of  absolute humidity is gram per cubic metre of dry air (g/m³ of dry air). 

7. Relative humidity.

 the ratio of actual mass of water vapour in a given volume of moist air and  the mass of water vapour in the same volume of saturated air at the same temperature and pressure is called relative humidity.

There is no unit of relative humidity. It's represented in present.

8. Dry bulb temperature.

It is the temp.  of air recorded by a thermometer, when it is not ting by the moisture present in the air. 

9. Wet bulb temperature.

 It is the temp. of air recorded by a thermometer, when its bulb wrapped by a wet cloth. Such a thermometer is called wet bulb thermometer. 

10. Wet bulb depression.

 It is the difference between dry bulb temperature and wet bulb emperature at any point. The wet bulb depression shows the relative humidity of the air.

 11. Dew point temperature.

 It is the tempe. of air recorded by a thermometer, when the water vapour present in it begins to condense. 

In other words, the dew point temp. the saturation temperature corresponding to the partial pressure of water vapour. 

12 Dew point depression. 

It is the difference between the dry bulb temperature and dew pit temperature of air.




You can also read following links 


 https://akrhvac.blogspot.com/2022/10/what-is-meaning-of-c-s-and-r-in-non.html

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 











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