Use the psychrometric chart for the following questions unless asked to “calculate”, in which case you must use the appropriate calculations. 1. Calculate the enthalpy (H in kJ/kg) of an air/water vapour mixture which is at 25oC and 0% rh (i.e. dry air). 2. Check your result from question 1 with the psychrometric chart. Are they the same? 3. Now calculate the new enthalpy of the same air/water vapour mixture after raising the rh to 50% (still at 25oC). 4. Check your result again with the psychrometric chart. Are they the same? 5. How much water vapour had to be added to it to raise the rh to 50%? 6. Without changing the enthalpy (i.e. an adiabatic process), how much more water vapour could the air/water vapour mixture from question 4 hold before becoming saturated? 7. What is the new temperature of the air/water vapour mixture of question 5 at saturation? (See over for #8) Timusk 2007 8. Calculate the January ventilation cost for a typical leaky old Toronto house measuring 5m wide x 20m long x 9m tall with a ventilation rate of 3 ACH. It is electrically heated and electricity costs $0.10 per kilowatt hour. (Base the air change volume/density on indoor air, using 101,325 Pa as the pressure). Check the enthalpy values outside/inside with values from the psychrometric chart. Outside conditions: -10oC / 75% rh Inside conditions: 21oC / 40% rh

Engineering Fundamentals: An Introduction to Engineering (MindTap Course List)

5th Edition

ISBN:9781305084766

Author:Saeed Moaveni

Publisher:Saeed Moaveni

Chapter13: Energy And Power

Section: Chapter Questions

Problem 22P

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Use the psychrometric chart for the following questions unless asked to “calculate”, in which case you must use the appropriate calculations. 1. Calculate the enthalpy (H in kJ/kg) of an air/water vapour mixture which is at 25oC and 0% rh (i.e. dry air). 2. Check your result from question 1 with the psychrometric chart. Are they the same? 3. Now calculate the new enthalpy of the same air/water vapour mixture after raising the rh to 50% (still at 25oC). 4. Check your result again with the psychrometric chart. Are they the same? 5. How much water vapour had to be added to it to raise the rh to 50%? 6. Without changing the enthalpy (i.e. an adiabatic process), how much more water vapour could the air/water vapour mixture from question 4 hold before becoming saturated? 7. What is the new temperature of the air/water vapour mixture of question 5 at saturation? (See over for #8) Timusk 2007 8. Calculate the January ventilation cost for a typical leaky old Toronto house measuring 5m wide x 20m long x 9m tall with a ventilation rate of 3 ACH. It is electrically heated and electricity costs $0.10 per kilowatt hour. (Base the air change volume/density on indoor air, using 101,325 Pa as the pressure). Check the enthalpy values outside/inside with values from the psychrometric chart. Outside conditions: -10oC / 75% rh Inside conditions: 21oC / 40% rh

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