19677599
Description
Flashcards by Alice Kimpton, updated more than 1 year ago
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Created by Alice Kimpton
almost 5 years ago
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| Question | Answer |
| What is the psychrometric chart? | A graphical representation of: - thermodynamic properties of moist air - air conditioning processes Not very accurate but convenient for quick estimatationgs 101325 Pa (760 mm Hg) from -10 ~ 60°C |
| Percentage saturation lines graph and equation | |
| Specific enthalpy lines graph and equation | |
| Wet bulb temperature lines graph and equation | |
| Specific volume lines graph and equation | |
| On psychrometric chart: - Find state point using temp and percentage saturation - Moisture content | Find temperature at 15C, draw vertical line (state point). Draw horizontal right line from state point to find moisture content, to also get partial pressure. |
| On psychrometric chart: - Dew point temperature - enthalpy | Draw horizontal left from state point to find dew point of moist air, then vertical line down for temperature reading. Move ruler from state point to the right so points on each ruler are the same e.g. 35 to find enthalpy. |
| On psychrometric chart: - Wet bulb temperature - Specific volume | Wet-bulb temperature by following enthalpy line to the left, draw vertical line down to get temperature reading. From state point you can estimate specific volume. |
| Steady flow process of typical summer air conditioning system | |
| 5-->1 sensible heating process | Note heat gain into reheater, no change in moisture content. Dry air is also constant. |
| 4--->5 cooling and dehumidification process | Note heat and moisture reduced from cooler, moisture is now balanced. |
| 2+3--->4 mixing process | where mad,2 = mda,2,recirculated + mad,2,exhaust |
| Mass of dry air is in balance (ingoing and outgoing air). When air supply is supplied into the room air coming from outside will mix with inside air, also from infiltration. Energy balance equation, people, light, laptops release heat into the room, plus energy associated from moisture transfer from equipment. | |
| Room sensible and latent heat load | |
| Supply air condition and ratio method 1: | |
| Supply air condition and ratio method 2: | Make position of room condition (point 5, 50% 22C). Use lower section of protractor to draw line from pint to indicating process from 1 to 2. Draw a line parallel to this line, crossing point 2 (light blue line) called room ratio line, slope corresponding to room ratio. Chose any temperature e.g. 18C and draw it on the chart. Draw horizontal line from point 1 to moisture content). |
| Winter air conditioning system: |
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