The point of intersection P between the 20☌ isotherm from the dry bulb temperature (1) and the line of 50% constant relative humidity (6) clearly defines the position of the required condition. The point on the chart is defined by the temperature and the relative humidity given above. These are typical values to provide comfort in an office.Įxample: Find the missing values for the following Note that the chart indicates a condition of 21 ☌ Dry bulb temperature and 48% Relative humidity. Allowances may be made for changes in barometric pressure by using correction factors. Since the properties and behaviour of moist air depend on barometric pressure, a psychrometric chart can only be drawn for a specific barometric pressure. The procedure can be time consuming.īy presenting the interrelated factors on a psychrometric chart, an immediate decision can be made regarding the feasibility of controlling an airĬonditioning system and the means required to carry this out.įor a given air sample nine different parameters are shown on the psychrometric chart.Ī position on the chart can be established at the intersection of two ordinates for known conditions and the others obtained. This may be achieved by a good knowledge of physics, with theoretical calculations using complicated formulae and tables. I promised you it’s simpler than it sounds.In air conditioning technology, it is necessary to define thermodynamic processes and the properties of moist air. That’s it for psychrometric chart analysis for air conditioning. Thus, addition of water vapour into the heated air will increase its humidity.
If the absolute humidity of the space is within the comfort region, then an air heater will do the trick. low dry bulb temperature, high relative humidity area.Relative humidity will increase to the comfort region and dry bulb temperature will decrease as a result of heat transfer Since the relative humidity is low, the water vapour will absorb heat and occupy the air space. Humidifiers will introduce water vapour into your air. Your money will be best spent if you chose humidifiers, if this is the case. high dry bulb temperature, low relative humidity area.It will also remove humidity by condensing water vapour Reasons being, air conditioning unit will cool the air by lowering the dry bulb temperature. If the temperature and humidity plot of your local area falls within this region, then consider buying or renting an air conditioning unit. high dry bulb temperature, high relative humidity area.These are stated RELATIVE to the comfort zone. Let us use four major regions within a psychrometric chart, to simplify the analysis. We have to plot this area inside the psychrometric chart, before we can proceed further with the air conditioning, "million dollar question". The area, or region was concluded by ASHRAE, after gathering sample from a very large group of people. A quick glance into the comfort zone.Ĭomfort zone is the area where most people will be comfortable. I suggest, we go through psychrometric chart page, if you need to know more about it. It is the first step in air conditioner buying guide. Psychrometric chart analysis can be used, and in fact, recommended to be used if you are at the cross road.Īir conditioning, OR no air conditioning?