Compressor Room Ventilation Worksheet

It does not replace detailed duct, fan, acoustic, fire/smoke or building-services design.

1. Purpose and Engineering Decision

A compressor room can overheat even when compressor capacity is adequate. The key ventilation question is how much air must move through the room, under the selected design ambient condition, to remove the heat that actually remains inside the room.

2. Core Sensible-Heat Equation

Q_room = rho_air x V_dot x cp_air x DeltaT

V_dot = Q_room / (rho_air x cp_air x DeltaT)

Q_room is the residual room heat load in kWth. V_dot is ventilation airflow in m3/s. rho_air and cp_air must match the design condition or be entered as documented assumptions. DeltaT is the permitted room-air rise from supply/inlet air to the selected room/extract condition.

3. Required Asset - Ventilation Calculation Worksheet

4. Air-Temperature Rise

The selected DeltaT is one of the strongest drivers of required airflow. A smaller permitted temperature rise requires more ventilation air.

5. Mechanical Airflow

V_mech = max(V_thermal - V_natural_verified, 0)

V_design = V_mech x (1 + Margin%)

Natural ventilation should be credited only when opening area, pressure driving force, wind/stack assumptions and operating availability are known. An unverified louver or open door should not be treated as guaranteed cooling capacity.

6. Recirculation Penalty

If hot discharge air is pulled back into the compressor-room intake, effective supply-air temperature rises and the useful DeltaT falls. The simplest conservative method is to replace outdoor supply temperature with the measured or calculated intake-air temperature at the compressor-room inlet.

DeltaT_effective = T_room,max - T_supply,effective

7. Air-Cooled vs Water-Cooled Room Ventilation

8. Supply and Extract Arrangement

Airflow quantity alone is not enough. Supply air must reach compressor cooling inlets without short-circuiting directly to the extract. Hot discharge should leave the room without being recirculated to compressor intakes.

9. Fan Duty Boundary

Detailed fan selection additionally requires total external static pressure across louvers, filters, ducts, bends, silencers, dampers and discharge points.

Fan Power approx = V_dot x DeltaP_total / eta_fan_system

This fan-power expression is optional for screening only. Final fan and duct selection must use the actual fan curve, density, static pressure and efficiency data.

10. Reference Test Case A - Thermal Airflow

Outdoor/supply air is 35 C and maximum room/extract temperature is 45 C. Use rho = 1.10 kg/m3 and cp = 1.006 kJ/(kg.K).

V_dot = 150 / (1.10 x 1.006 x 10) = 13.56 m3/s

Required thermal airflow is approximately 48,798 m3/h before any explicit project margin.

11. Reference Test Case B - Margin and Natural-Air Credit

Synthetic validation case: thermal requirement is 48,800 m3/h. Verified natural-air contribution is 6,000 m3/h. Apply a 10% explicit design margin to the required mechanical airflow.

12. Reference Test Case C - Recirculation Effect

Synthetic validation case: room maximum remains 45 C. Outdoor air is 35 C, but recirculation raises actual supply air at the compressor intake to 39 C. For the same 150 kWth heat load, allowed DeltaT falls from 10 C to 6 C.

The example shows why correcting hot-air recirculation can be more effective than simply increasing fan size.

13. Reference Test Case D - Peak Fleet Scenario

Synthetic validation case: Compressor A contributes 70 kWth, Compressor B 55 kWth, Compressor C 30 kWth, and treatment/electrical auxiliaries 15 kWth to the room. Supply air is 34 C and maximum room temperature is 44 C. Use rho 1.11 kg/m3 and cp 1.006 kJ/(kg.K).

Peak room heat load = 170 kWth. Required thermal airflow = approximately 54,806 m3/h before design margin.

14. Ventilation Opening Screen

The result is a geometric screening area only; it does not replace pressure-drop and acoustic selection of louvers or filters.

Free Area = V_dot / Face Velocity

15. Natural Ventilation Limitation

Natural ventilation depends on wind, buoyancy, opening geometry and obstructions. It can vary sharply with weather and door/louver position.

16. Hot Ambient Condition

The worst ventilation condition may occur on the hottest design day because room-to-outdoor temperature difference is smallest.

17. Seasonal Heat-Recovery / Duct Switching

A recovery damper failure that returns hot air to the compressor room should be included as an abnormal operating case where relevant.

18. Input Model

19. Validation and Guardrails

20. Output Specification