The air leaves the coil at 55 F db and 54 F wb. (a) Sea level Dry (b) 5,000 feet Dry Wet Dew Point Ratio (lbmv/lbma) Enthalpy (Btu/lbma) Relative (%) Specific Volume ( 3 /lbma) Wet Dew Point Ratio (lbmv/lbma) Enthalpy (Btu/lbma) Relative (%) Specific Volume ( 3 /lbma)ģ ME 44 Homework Solutions Set Air enters a cooling coil at the rate of 5,000 cfm at 80 F db, 68 F wb and sea-level pressure. 2 aĢ ME 44 Homework Solutions Set Complete the table using the ASHRAE psychrometric chart for (a) sea level and (b) 5,000 feet. This value can be obtained analytically from the above results or by translating the line 2 to the protractor scale as illustrated below. Total heat transfer = h h2 = 8.28 Btu/bma The sensible heat factor (or ratio) is the sensible heat transfer divided by the total heat transfer. On a pound of dry air basis this is the change in enthalpy between a and 2 Sensible heat transfer = h a h 2 = 6.2 Btu/lbma (d) The total heat removed is the energy required to move from point to point 2 and represents the sum of the latent and sensible heat transfer. This is the energy required to move from point a to point 2. Latent heat transfer = h h a = 2.6 Btu/lbma (c) The sensible heat removed is the heat transfer that causes a change in the air temperature. On a pound of dry air basis this is the change in enthalpy between and a. This is the energy required to move from point to point a. (a) The pounds of moisture removed per pound of dry air is given by ω - ω 2 = ω = lbmv/lbma (b) The heat removed to condense the moisture is the latent heat.
Properties are read from a full-size psychrometric chart (the chart below is only used to illustrate the graphical procedure).
The initial and final states of the air are plotted along with an intermediate point a which represents a state with the same dry bulb temperature as and the same humidity ratio as 2. Solution: The solution utilizes the ASHRAE sea level psychrometric chart. Using the psychrometric chart, find (a) the moisture removed per pound of dry air, (b) the heat removed to condense the moisture, (c) the sensible heat removed, and (d) the total heat removed. 1 ME 44 Homework Solutions Set 3 3- Air (assumed to be at standard atmospheric pressure) is cooled from 80 F db and 67 F wb until it is saturated at 55 F.
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