Presentation 11th april
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The document discusses a weather report stating the temperature is 24°C and relative humidity is 50%. It then asks the reader to: 1) Use a psychrometric chart to estimate various properties including absolute humidity, humid volume, specific enthalpy, wet-bulb temperature, and dew point temperature. 2) Calculate that a thermometer mounted outside would read 24°C. 3) Determine that condensation would begin when air is cooled to the dew point of 13°C. 4) Explain that feeling cold after exiting a pool is from skin evaporation lowering temperature to the dew point of 13°C, and this effect would be reduced at 98% relative humidity due to slower
Presentation 11th april
- 2. The latest weather report states that the temperature is 24ᵒC and the relative humidity 50%. a) Use the psychometric chart to estimate the absolute humidity, humid volume, specific enthalpy, wet-bulb temperature, and dew-point temperature of the air. b) A thermometer is mounted on the back porch of your house. What temperature would it read? c) A sample of outside air is cooled at constant pressure. At what temperature would condensation begin? d) You step out of your neighborhood pool and feel quite cold until you dry off. Explain why. Estimate your skin temperature while you were still wet. Explain your answer. What would be different if the relative humidity were 98%?
- 4. a) Absolute humidity = 0.009 kg water/kg DA Humid Volume = 0.855 m3/kg DA Specific enthalpy = 48 kJ/kg DA Wet-bulb temperature = 17ᵒC Dew point temperature= 13ᵒC b) The temperature would be 24ᵒC
- 5. c) Condensation will be at the dew point which is 13ᵒC. d) => When your skin is wet the evaporation of the moisture takes heat away from your skin and makes you feel cold. => As evaporation is taking place on your skin temperature will be approximately at dew point which is 13ᵒC => If the relative humidity is at 98%, the rate of evaporation would be slower. Thus, skin temperature would not drop as much.