Let's break down and solve each part of QUESTION 3 step by step: --- ## **Q 3(a): Dead End Lines vs Ring Mains for Compressed Air Distribution** **Question:** Several problems may be encountered when distributing compressed air to point of use. Dead End Lines or Ring Mains may be used. Highlight the advantages and disadvantages of each distribution method. ### **Dead End Lines** **Advantages:** - Simple and cheap to install. - Suits small installations with limited use points. **Disadvantages:** - Pressure drop at the point furthest from the compressor. - If a section needs maintenance, the entire line is affected. - Air quality may deteriorate at the ends due to stagnant air and water/oil accumulation. ### **Ring Mains** **Advantages:** - More uniform pressure throughout the system. - Multiple paths for air; if one part is under maintenance, the rest can still operate. - Better air quality due to air movement and less accumulation. **Disadvantages:** - More expensive and complex to install. - Requires more pipework and fittings. --- ## **Q 3(b): Take-off Points in Ring Main Systems** **Question:** Secondary lines are used at point of use to link the ring main to equipment. Various options exist to ensure air quality. Highlight the advantages/disadvantages of **taking off from the top vs bottom** and the effect on air quality. ### **Take-off from the Top** - **Advantage:** Less moisture/oil enters the equipment, as these settle at the bottom of the pipe. - **Disadvantage:** May require more complex fittings. ### **Take-off from the Bottom** - **Advantage:** Simpler installation. - **Disadvantage:** More moisture and oil can be drawn into the equipment, reducing air quality and potentially damaging equipment. **Summary:** **Top take-off** is preferred for better air quality at the point of use, as it reduces the risk of moisture/oil carryover. --- ## **Q 3(c): Psychrometric Calculations** **Given:** - Partial pressure of water vapour, \( p_v = 0.02063 \) bar - Total pressure, \( p_{atm} = 1.01325 \) bar - Temperature, \( T = 305K \) ### **1) Degree of Saturation of the Vapour** - **Saturation pressure of water at 305K (32°C):** (From steam tables) \( p_{wsat} \approx 0.0562 \) bar \[ \text{Degree of Saturation} = \frac{p_v}{p_{wsat}} \times 100\% \] \[ = \frac{0.02063}{0.0562} \times 100\% \] \[ = 36.73\% \] --- ### **2) Specific Humidity and Relative Humidity** #### **Specific Humidity (\( \omega \ ))** \[ \omega = 0.622 \times \frac{p_v}{p_{atm} - p_v} \] \[ = 0.622 \times \frac{0.02063}{1.01325 - 0.02063} \] \[ = 0.622 \times \frac{0.02063}{0.99262} \] \[ = 0.622 \times 0.02079 \] \[ = 0.01294 \text{ kg water/kg dry air} \] #### **Relative Humidity (\( \phi \ ))** \[ \phi = \frac{p_v}{p_{wsat}} \times 100\% \] Already calculated above: \[ \phi = 36.73\% \] --- ### **3) Temperature at which air must be cooled for condensation (Dew Point)** Dew point is the temperature at which the partial pressure of water vapor equals the saturation pressure. - Given \( p_v = 0.02063 \) bar. - From steam tables, the saturation temperature for \( p_{wsat} = 0.02063 \) bar is approximately **~18.3°C** (Check steam tables for more precise value). --- ## **Summary Table** | Part | Calculation/Discussion | Final Answer | |------|-----------------------|--------------| | 3(a) | Dead End vs Ring Main | See above | | 3(b) | Take-off points | Top take-off is better for air quality | | 3(c-1) | Degree of Saturation | 36.73% | | 3(c-2) | Specific Humidity | 0.01294 kg/kg | | 3(c-2) | Relative Humidity | 36.73% | | 3(c-3) | Dew Point Temp | ~18.3°C | --- **Let me know if you need further explanations or calculations!**