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Egypt Engineering Consultant Mechanical study materials
Egypt Engineering Consultant Mechanical study resources

Egypt Engineering Consultant Mechanical: HVAC and Refrigeration Systems Design

Egypt Engineering Consultant Mechanical · Work through your exam, one topic at a time.

All guide sections

HVAC and Refrigeration Systems Design

What the exam tests

This domain checks whether you can take Egyptian design conditions, apply ECP 306 and ASHRAE fundamentals, and produce a defensible load, equipment and air-distribution design. Expect psychrometrics, cooling-load breakdown, ventilation, duct and pipe sizing, chiller and VRF selection, and refrigerant safety.

Core rules

  • Design conditions: Cairo summer is around 40 °C DB and 27 °C WB, winter 8–10 °C; comfort indoor design is commonly 24 ± 1 °C and 50 ± 5 % RH. Use the project brief over generic values.
  • Load has external, internal and ventilation parts. Compute sensible and latent separately: airflow follows sensible load, coil capacity follows total load.
  • Fresh air: use ASHRAE 62.1 rates or ECP 306, whichever governs; add the outdoor-air load to the coil, not to the room load.
  • Air side: equal-friction or static-regain duct sizing; keep mains around 6–8 m/s and branches lower; check fan total pressure, not only external static.
  • Water side: chilled-water ΔT of 5–7 K; variable-primary or primary/secondary; size on velocity and pressure drop, not nominal size.
  • Refrigerants: R-410A is A1, R-32 is A2L, R-290 is A3. A2L and A3 systems need charge limits, ventilation and ignition-source control under EN 378 or ASHRAE 15.

Worked example

A hall has 24 kW sensible and 6 kW latent room load. Supply air is 14 °C and room air 24 °C. Using Qs = 1.2 × L/s × ΔT gives L/s = 24,000 / (1.2 × 10) = 2,000 L/s, or 2.0 m³/s. The total coil load is 30 kW, about 8.5 TR because 30 / 3.517 = 8.5. If 15 % fresh air at 40 °C DB and 27 °C WB is added, the coil load rises but the room airflow does not. Separating these two calculations is the key exam skill.

Traps

Using total load to find airflow; mixing kW and TR; forgetting fan and duct heat gain; ignoring fresh-air latent load on the humid coast; selecting a chiller on nominal capacity without fouling correction; specifying an A2L refrigerant without a leak and ventilation strategy.

Key points

  • Separate sensible and latent load; airflow comes from sensible load.
  • Use project design conditions and the stricter of ECP 306 and ASHRAE 62.1 for ventilation.
  • 1 TR = 3.517 kW; 1.2 W per L/s per K is a useful air-side check.
  • A2L and A3 refrigerants require charge limits, ventilation and ignition control.
  • Add duct and fan heat gain to the coil load.