Carrier psychrometric chart sensible heat

#Carrier psychrometric chart sensible heat pdf#
#Carrier psychrometric chart sensible heat skin#

The value of RH reduces from left towards right. The different curves of RH indicate different values of humidity measured in percentage.

#Carrier psychrometric chart sensible heat pdf#

In ' The Pyschrometic Chart, Part 2,' I'll take this example further by putting that air inside a piece of process equipment such as a dryer or oven.Д®ditor's Note: Use the link at the bottom of the page to receive a PDF document containing the article, which will show the graphic.The RH lines are the curves extending from the lower left to the upper right part of the psychrometric chart.

#Carrier psychrometric chart sensible heat skin#

The skin of the dryer is hotter than ambient steel. The product has increased in temperature. Where has it gone? Losses! There are losses from radiation, conduction and convection. This is a reduction of 6 BTUs per pound of dry air.

The energy in the air has reduced to 58 BTUs per pound of dry air.

The air has densified so that 15.0 ft 3 of air now weighs one pound. The relative humidity is at about 52 percent. It has picked up 0.015 pounds of moisture per pound of dry air from the product. The humidity ratio has increased to 0.029 pounds of moisture per pound of dry air. The dew point temperature has risen to 88 oF (31 oC). For the air to follow path B to D, you obtain the following data: And, by placing some wet gauze on the bulb in the same location, you measure a wet bulb temperature of 94 oF. Presume you take your dry bulb thermometer and measure the temperature of 110 oF above the product bed. Let's not make any more assumptions instead, we will replace them with presumptions. This is part of our huge assumption that the sensible heat in the air has been replaced by latent heat in the moisture. The energy in the air has remained relatively constant. The air has densified so that 15.15 ft 3 of air now weighs one pound.

The relative humidity is back to 60 percent. It has picked up 0.021 pounds of moisture per pound of dry air from the product. The humidity ratio has increased to 0.035 pounds of moisture per pound of dry air. The dewpoint temperature has risen to 94 oF (34 oC). The wet bulb temperature has remained the same. At this point, you obtain the following data: If this were the case, and we chose that the air, after passing through the product, was at 110 oF (43 oC), the air would follow the constant wet bulb temperature line (adiabatic because no heat is entering or leaving the system) until it reached the dry bulb temperature of 110 oF, which is point C. It never is, but I can take the liberty under guise of illustration. For this example, we'll make a huge assumption that all the energy in the air is used for evaporation. Suppose you now pass this heated air through a moist product. The enthalpy, or energy of the air, has increased to 64 BTU per pound of dry air. The air has expanded so that 17 ft 3 of this air now weighs one pound. The relative humidity has dropped from 60 percent to 3 percent. The dewpoint temperature has not changed. The wet bulb temperature has increased to 96 oF (36 oC). Again, from the curve, you read off the corresponding properties of the air as follows: The amount of water in the air remains the same, so you can follow the humidity ratio line until you reach the dry bulb temperature line of 200 oF. In terms of the physical constituents of the air, you are changing nothing. Next, imagine that you take this same air and heat it up indirectly to 200 oF (93 oC). The enthalpy is 36 BTU per pound of dry air. The specific volume is 14 ft 3 per pound of dry air. The humidity ratio is 0.014 pounds of moisture per pound of air. That is, if you cool the air, the water will start to condense out at 68 oF. The dewpoint, or saturation, temperature is 68 oF (20 oC).

The wet bulb temperature is 72 oF (22 oC). From the chart, you can read off the remaining properties of this air as follows: Looking at the chart in figure 1, you plot this condition at point A. You take a reading with your hygrometer that tells us that the relative humidity is 60 percent. Taking a thermometer and measuring the ambient air temperature, you get 82 oF (28 oC).