Route: /engineering-tools/compressed-air-cooling-load-worksheet/ (proposed until route reconciliation).

1. Purpose and Engineering Decision

A compressor package converts electrical input into compressed-air energy and heat that leaves the selected system boundary through several paths. For cooling design, the critical question is not simply 'how many compressor kilowatts are installed?' but 'where does the heat go during the operating state being designed?'

It distinguishes heat rejected to room air, heat rejected to cooling water, heat deliberately recovered for useful service, and heat carried out with the compressed-air stream or other documented paths.

Mode	Primary output
Package heat balance	Heat rejection by path for one compressor operating point
Air-cooled room load	kWth released into compressor-room / duct air stream
Water-cooled duty	Required cooling-water flow from kWth and allowable water temperature rise
Heat-recovery scenario	Residual cooling load after verified useful heat recovery
Fleet profile	Cooling duty by compressor operating state and simultaneous combination
Design condition	Peak, normal and future cooling-load comparison

2. Cooling Boundary Must Be Declared

Boundary	Include / exclude decision
Compressor package electrical input	Main motor plus package auxiliaries if measured at package feeder
Separate ventilation fans	Include only if the room HVAC/ventilation design treats them as internal heat loads
Dryer / treatment electrical load	Separate row unless the project intentionally includes treatment-room cooling
Cooling-water heat rejection	Remove from room-air load when genuinely transferred out of the room
Recovered useful heat	Subtract only when a verified recovery system exports heat outside the cooling boundary
Compressed-air enthalpy leaving package	Keep as a separate documented path where quantified

The worksheet must display the chosen boundary. A water-cooled compressor cannot be treated as if all package input becomes room-air heat, and an air-cooled compressor with ducted hot air cannot be treated as if all heat remains in the room.

3. Steady-State Heat-Balance Framework

P_electrical + Other Internal Heat Inputs = Q_room + Q_water + Q_recovered + Q_air_stream_out + Q_other

This is a bookkeeping equation. Individual terms should come from manufacturer data, measured heat balances or explicit engineering assumptions.

4. Cooling Duty Worksheet with Assumptions - Required Asset

Item	Input / formula	Unit	Evidence / assumption
Package input power	Measured or verified	kW
Operating state	Load / unload / VSD point	-	Controller / logger
Room-air heat rejection	Entered / calculated	kWth	Model data / balance
Cooling-water heat rejection	Entered / calculated	kWth	Model data / measured water side
Useful heat recovery		kWth	Recovery circuit
Compressed-air / other exported heat	Entered if quantified	kWth	Method source
Room residual heat load	Balance result	kWth	Calculated
Cooling-air inlet temperature	User input	deg C	Design ambient / measured
Cooling-air outlet temperature	User input	deg C	Design / measured
Cooling-water inlet/outlet	User input	deg C	Design / measured
Air / water flow	Calculated or measured	m3/s, m3/h, L/min	Calculation
Design margin	Explicit user input	% or kWth	Project basis

5. Room Residual Heat Load

Q_room,residual = P_in + Q_other,in - Q_water - Q_recovered - Q_air_or_other_export

If the user directly enters a verified room heat-rejection value from a package heat-balance document, that value may be used instead of reconstructing the whole balance. The tool should preserve whether the result is direct or residual-by-difference because confidence is different.

6. Air-Side Cooling Relationship

Q_air = rho_air x V_dot_air x cp_air x DeltaT_air

V_dot_air = Q_air / (rho_air x cp_air x DeltaT_air)

7. Water-Side Cooling Relationship

Q_water = m_dot_water x cp_water x DeltaT_water

Water flow (L/min) approx = Q_kW x 60 / (4.186 x DeltaT_C)

The water-side calculation is valid as a sensible-heat balance for liquid water over ordinary cooling ranges. Actual pump sizing, water quality, fouling allowance, pressure drop, glycol correction or cooling-tower design are separate engineering tasks.

8. Heat-Recovery Credit

Heat recovery reduces cooling duty only when recovered heat is exported outside the cooling boundary. If recovered hot water later releases its heat back into the same compressor room, no room-cooling credit exists.

Q_residual_after_recovery = Q_base_cooling - Q_useful_exported_recovery

9. Air-Cooled Compressor Boundary

For an air-cooled package, the package cooling air may discharge directly into the compressor room or be ducted outdoors.

Discharge arrangement	Room-cooling implication
Hot air discharged into room	Most package air-side heat remains a room load
Hot air fully ducted outdoors	Room load is limited to package radiation/leakage and other internal sources
Seasonal heat-recovery duct	Use separate summer / winter scenarios
Partial recirculation	Model only the verified fraction returned to room

10. Water-Cooled Compressor Boundary

For water-cooled machines, the dominant heat path may be the cooling-water circuit, but motor, radiation and auxiliaries can still add heat to the room.

11. Reference Test Case A - Air-Side Flow for Known Room Load

Synthetic validation case: residual room heat load is 120 kWth. Cooling air enters at 32 C and may leave at 42 C. Use air density 1.12 kg/m3 and cp = 1.006 kJ/(kg.K).

V_dot = 120 / (1.12 x 1.006 x 10) = 10.65 m3/s

Reference result: approximately 38,341 m3/h of air to carry 120 kWth across a 10 C temperature rise.

12. Reference Test Case B - Cooling-Water Flow

Synthetic validation case: cooling-water circuit must remove 180 kWth with water entering at 30 C and leaving at 38 C.

Water flow = 180 x 60 / (4.186 x 8) = 322.5 L/min

This is the heat-balance flow only. Pump head, exchanger pressure drop, fouling and water-treatment requirements remain separate.

13. Reference Test Case C - Split Heat Paths

Synthetic validation case: package electrical input is 200 kW. Verified water-side rejection is 145 kWth, useful heat recovery exported outside the room is 25 kWth, and another 8 kWth leaves with a documented external air stream.

Q_room = 200 - 145 - 25 - 8 = 22.0 kWth

Residual room heat load is 22.0 kWth under the stated steady-state boundary. The worksheet should flag any unexplained residual as either room heat or an unresolved balance term rather than forcing it to zero.

14. Reference Test Case D - Fleet Operating Scenario

Synthetic validation case: three compressors have room heat loads of 80, 55 and 25 kWth in the selected operating states. A separate dryer adds 12 kWth to the same room.

Item	Heat load
Compressor A	80 kWth
Compressor B	55 kWth
Compressor C	25 kWth
Dryer / treatment	12 kWth
Scenario total	172 kWth
With explicit 10% project margin	189.2 kWth

15. Part-Load and Control-State Cooling Duty

Cooling duty follows the actual operating state, not only installed motor rating.

Q_scenario = Sum(Q_heat,state,i x simultaneous state flag_i)

16. Peak, Normal and Future Design Cases

Scenario	Purpose
Normal production	Routine ventilation / water-cooling requirement
Peak production	Maximum credible simultaneous operating heat load
Hot ambient	Check reduced cooling-air temperature difference / cooler capability
Future expansion	Planned additional machines / treatment equipment
Emergency / temporary	Rental or temporary compressor heat load

17. Design Margin

Q_design = Q_calculated x (1 + Margin%)

Margin is explicit and project-specific.

18. Air-Side Temperature Difference Sensitivity

For the same heat load, required air volume rises sharply as the allowed air-temperature rise becomes smaller.

Allowed DeltaT	Required air flow	Required air flow
5 C	21.30 m3/s	76,683 m3/h
8 C	13.31 m3/s	47,927 m3/h
10 C	10.65 m3/s	38,341 m3/h
12 C	8.88 m3/s	31,951 m3/h
15 C	7.10 m3/s	25,561 m3/h

This sensitivity table is why ventilation design must use realistic inlet and discharge temperatures rather than a generic air-change rate.

19. Water-Side Temperature Difference Sensitivity

Water DeltaT	Flow for 180 kWth
4 C	645.0 L/min
6 C	430.0 L/min
8 C	322.5 L/min
10 C	258.0 L/min
12 C	215.0 L/min

20. Input Model

Input group	Field	Validation / note
Package	Electrical input kW	> 0 for operating state
State	Loaded / unloaded / VSD / standby	Required
Heat path	Room-air heat	Direct or balance-derived
Heat path	Water-side rejection	>= 0
Heat path	Exported heat recovery	>= 0
Heat path	Other exported heat	>= 0
Air side	Inlet / outlet temperatures	Outlet > inlet
Air side	rho and cp	Visible assumptions / measured
Water side	Inlet / outlet temperatures	Outlet > inlet
Water side	cp / density	Visible assumptions
Design	Margin	>= 0
Evidence	OEM data / measurement / calculation source	Recommended

21. Validation and Guardrails

Condition	Required behaviour
Negative heat-path value	Block calculation unless explicitly defined as a credit/export
Sum of known exported heat > electrical + other heat input	Flag impossible balance
Air outlet temperature <= inlet	Block air-flow calculation
Water outlet temperature <= inlet	Block water-flow calculation
Heat recovery deducted but not exported outside cooling boundary	Warn / do not subtract
Installed motor rating used as measured package input	Label preliminary
Peak scenario omits simultaneously operating auxiliaries	Warn
Room heat derived as small residual from uncertain large terms	Lower confidence / recommend direct measurement
Air-side flow interpreted as fan selection

22. Output Specification

Output	Display rule
Room residual heat load	kWth
Water-side cooling duty	kWth
Recovered/exported heat	kWth
Required cooling-air flow	m3/s and m3/h
Required cooling-water flow	L/min and optional m3/h
Scenario total	Normal / peak / future
Design duty	After explicit margin
Heat-balance closure	Known inputs vs known heat paths
Confidence / warnings	Always visible

Compressed Air Cooling Load Worksheet

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