NMX‑VCS‑30 / Rev 00 / airborne thermal management / cycle · pack · charge 2026 · Product Page

NMX-VCS-30 · ENGINEERED TO ORDER — AIRBORNE VAPOUR COMPRESSION SYSTEMS

The heat has to go somewhere. At altitude, somewhere keeps moving.

Name: Airborne Vapour Compression System
Brand: Neometrix

A refrigeration plant on the ground rejects its heat into an ambient that sits still, and it is allowed to be heavy. An airborne pack has neither luxury. Its sink is ram air, whose temperature, pressure and density all move at once with altitude and speed — so the cycle is sized for the worst point of the envelope, never the average day, and has to stay stable everywhere in between. Its mass and volume are paid for out of what the platform could otherwise carry, which makes kilowatts per kilogram the real specification and pushes every choice towards compact, high-speed and minimum-charge. And because vibration, manoeuvre loads and attitude change all attack a sealed circuit, leak rate and oil return are qualification items rather than commissioning notes. Equipment of this class has been quoted against successive airborne vapour compression system requirements for a defence research organisation; no delivered airborne vapour compression system is claimed — the class is engineered to order.

Enquire — airborne cooling packs Capability sheet (PDF)

Illustrative of the class — a compact refrigeration pack on a clean light-grey laboratory bench: an open machined aluminium frame about the size of a suitcase containing a small cylindrical compressor on black elastomer anti-vibration mounts at one end, two flat rectangular finned heat exchanger blocks standing upright on opposite sides, smoothly formed copper and stainless refrigerant tubes with neat brazed joints running between them, a small cylindrical receiver vessel, a compact valve and sensor manifold, and a machined electrical connector plate with two blank circular connectors, no people and no readable markings

Fig · 01 The pack — a whole refrigeration cycle inside a frame small enough and light enough to be carried

Sink

ram airit moves with the flight

Sized for

the cornernot the average day

Judged on

kW per kgand per litre

Qualified for

shake, g, altitudeand the charge staying in

Status

engineered to orderquoted class

ISO 9001 / 14001 Engineered to order Airborne thermal management Cycle design & qualification Noida · India

Overview

The cycle is ordinary. Everything around it is not.

Compress, condense, expand, evaporate — the thermodynamics are a century old and entirely unremarkable. What makes an airborne pack hard is that all four steps have to keep working while the sink moves, the mass budget bites and the airframe shakes.

Illustrative of the class — close view of a compact heat exchanger core resting on a clean light-grey laboratory bench: a flat rectangular block of very fine bright aluminium fins between narrow flat tubes, with a cylindrical manifold header along each end and short polished stub tubes brazed into the headers, clean even brazed fillets, a regular undamaged fin pack, and a machined aluminium mounting flange with plain bolt holes along one edge, no people and no readable markings

Fig · 02 The core — surface area bought with fin density, and paid for in air-side pressure drop

A moving sink changes the whole sizing problem. A ground chiller is designed against a design ambient and a safety margin. An airborne condenser rejects into air whose temperature rises with speed, whose density falls with altitude, and whose available mass flow depends on both at once — so the same pack that has ample capacity at one point of the envelope can be short of it at another. The design case is therefore not a temperature but a combination: the hottest, thinnest air the platform is allowed to meet, at the heat load it is allowed to be carrying, with the air-side pressure drop the installation can actually afford. Size for the average and the pack will disappoint exactly when it is needed.

Mass and volume are not constraints, they are the specification. Every kilogram of cooling plant is a kilogram not carried as something more useful, and every litre it occupies is volume taken out of an equipment bay. So the figure of merit is specific capacity — kilowatts per kilogram, and per litre — and it drives everything: a compact high-speed compressor rather than a slow heavy one, heat exchangers that buy surface with very fine fin geometry rather than with size, short and well-formed refrigerant lines, and the smallest charge that will still run the cycle. A ground design on a diet is not the same machine; the architecture has to be reconsidered, not shrunk.

And the sealed circuit is what gets qualified. Two things keep a vapour compression system alive: the refrigerant staying inside it, and the oil finding its way back to the compressor. Vibration works on every joint and brazed connection; manoeuvre loads pull on line routing in several axes at once; attitude changes move where liquid collects; thermal cycling loosens what vibration has already found. So leak rate is a measured, qualified property rather than a commissioning check, and oil return is proven at the awkward combinations — low load, high attitude, after a cold start — not merely at the rating point.

Equipment of this class has been quoted against successive airborne vapour compression system requirements for a defence research organisation, in each case as a system with its accessories. No delivered airborne vapour compression system is claimed: the class is engineered to order, and the record is stated as it stands.

Envelope-sized

Built for the corner

Hottest, thinnest air at the highest load — because the average day is not the design case.

Weighed

Kilowatts per kilogram

Compact, high-speed, minimum charge — a reconsidered architecture, not a shrunken ground unit.

Sealed

The charge is the qualification

Leak rate measured and oil return proven at the awkward combinations, not just at the rating.

Architecture

Reject, carry, contain.

The schematic follows the duty — a sink that moves, a worst point to size against, a mass budget that is paid for, and a charge that has to stay put — then the machine underneath: compressor and drive, condenser and ram-air side, evaporator and load side, and the control, charge and accessories.

FIG · 03AIRBORNE VAPOUR COMPRESSION ARCHITECTURE · COMPRESSOR + DRIVE / CONDENSER + RAM-AIR SIDE / EVAPORATOR + LOAD SIDE / CONTROL, CHARGE + ACCESSORIES

Fig · 03 A sealed circuit that stays sealed for the whole of its service life

Arc · 01

Compressor & Drive

Compact, high-speed, on anti-vibration mounts — taken from the platform's electrical supply, with soft start and protection.

Arc · 02

Condenser & Ram-Air Side

Heat rejected into a sink that will not hold still — sized for the envelope corner, within the air-side pressure drop available.

Arc · 03

Evaporator & Load Side

Air-cooled or liquid-cooled loads, superheat held steady — the expansion device chosen so a stepping load does not destabilise the cycle.

Arc · 04

Control, Charge & Accessories

Receiver, filter drier, service valves, sensors, protection — and the charge and oil management the qualification rests on.

Cooling something that has to fly, drive or deploy? Send the heat load, the ambient and altitude envelope, the mass and volume budget and the electrical supply — a clause-by-clause compliance matrix within two working days · [email protected]

Send tender spec

Specifications

Reference packs, built to the envelope.

The parameters below describe reference packs. Compressor selection, heat exchanger surface, refrigerant choice, charge, mass and control strategy all follow from three givens: the heat load and how it varies, the ambient and altitude envelope the platform must cover, and the mass, volume and electrical supply available to carry it.

Illustrative of the class — close view of a compact refrigeration compressor on a clean light-grey laboratory bench: a squat cylindrical machined-aluminium compressor body standing upright on four black elastomer anti-vibration mounts bolted to a machined baseplate, two polished copper suction and discharge tubes leaving the top in smooth formed bends, a small dark cast terminal box on the side with a blank cover and a cable gland, a braided flexible hose section in one line and bright new stainless fasteners throughout, no people and no readable markings

Fig · 04 The compressor — isolated from the structure it sits on, and the reason oil return has to be designed

Where airborne cooling goes wrong

Sized for the average condition — ample on the bench, short of capacity at the one corner of the envelope where the air is hot and thin and the load is high. A ground design put on a diet — mass taken out, but the architecture never reconsidered, so the pack is heavy for its duty and marginal everywhere. Oil return assumed — proven at the rating point and nowhere else, so the compressor starves at low load, at attitude, or after a cold start. Leak rate treated as a commissioning check — rather than a qualified property measured after vibration and thermal cycling, which is the only version of the number that predicts what happens in service. Control tuned at one operating point — and then hunting, or tripping, the first time a load steps on. The air side forgotten — a condenser that needs more pressure drop than the installation can give it, so the paper capacity never appears. And no protection at the edge — a pack that has no defined behaviour beyond its envelope will find one of its own.

So the discipline runs the other way. The design case is a combination, agreed in writing: ambient, altitude, speed, heat load and available air-side pressure drop, at the corner rather than the mean. The architecture is chosen for specific capacity from the start. Oil return is designed — line sizing, routing, traps and velocities — and then demonstrated at low load and at attitude. Leak rate is measured after the vibration and thermal cycling, not before. Control is proven against stepping loads and cold starts, with defined protection outside the envelope. And the whole pack is qualified as it will be installed, because a refrigeration circuit is only as good as the mounting, the routing and the charge it was built with.

Full specification — expand

System	Airborne vapour compression system — compressor & drive, condenser & ram-air side, evaporator & load side, control, charge & accessories
Governing Idea	The heat sink moves — ram air changes temperature, pressure and density with altitude and speed, so the cycle is sized for the worst point of the envelope, not the average
The Constraint	Mass and volume are the specification — specific capacity in kilowatts per kilogram and per litre drives compressor speed, heat exchanger surface, line routing and charge
The Qualification	The charge must stay where it is put — leak rate and oil return under vibration, manoeuvre load, attitude change and thermal cycling are qualified properties, not commissioning checks
Compressor	Compact high-speed machine taken from the platform's electrical supply, carried on anti-vibration mounts, with soft start, protection and defined behaviour on supply disturbance
Heat Rejection	Condenser and ram-air side sized at the envelope corner, within the air-side pressure drop the installation can afford — fine-surface compact cores rather than large frontal area
Load Side	Evaporator serving air-cooled or liquid-cooled loads; expansion device and superheat control selected so a stepping load does not destabilise the cycle
Accessories	Receiver, filter drier, service and isolation valves, pressure and temperature sensors, control laws and protection — the accessories the requirement names, and the ones qualification depends on
Off-Design	Cold-soak start, stepping heat load, transient response and defined protection beyond the envelope — a pack that only behaves at its rating is not qualified
Refrigerant	Selected for the duty, the temperatures and the environment, and stated generically — never by trade name; minimum charge consistent with running the cycle
Environmental	Vibration, shock, manoeuvre loading, attitude, altitude, temperature and humidity qualification, with leak rate measured after the environmental sequence
The Split	The site's ground air-conditioning cart does the same thermodynamics with none of the same constraints — it is wheeled to a parked aircraft, rejects heat to a fixed ambient, and may weigh what it likes. The liquid cooling system and coolant distribution unit is airborne but moves heat rather than making cold — it cannot take a load below its own sink temperature, which is precisely why a vapour compression pack exists, and the two are frequently used together. The ECS test bench is the machine that tests one of these, not the machine itself
Scope Boundary	Ours: cycle design & sizing, compressor & drive integration, compact heat exchangers, line routing & brazing, charge & oil management, control & protection, vibration & environmental qualification, acceptance test procedures, installation, commissioning, documentation, training, spares & AMC — including build to the customer's specification. Bought-in certified: compressors, heat exchanger cores, valves, sensors, control hardware. The customer's: the platform, its heat loads, its envelope and its acceptance limits
Status	Engineered to order — equipment of this class quoted against successive airborne vapour compression system requirements for a defence research organisation; no delivered airborne vapour compression system is claimed

PDF · 1 page

Airborne Vapour Compression System — Capability Sheet

Tender Response

Send heat load, envelope & mass budget — compliance matrix in two working days

Variants

One cycle, four installations.

What changes is what the cold is delivered to, and how hard the platform squeezes the mass budget.

Var · 01

Air-Cooled Load Packs

Cold air delivered straight to the bay or the cabinet — the simplest installation, and the one most sensitive to ducting.

Var · 02

Liquid-Loop Packs

Chilling a coolant loop feeding distributed electronics — paired with a coolant distribution unit rather than replacing it.

Var · 03

Ground & Shelter Variants

The same architecture with the mass budget relaxed — transportable cabins, shelters and mobile platforms.

Var · 04

Accessories, Control & Charge

Receivers, driers, valves, sensors and control laws — supplied with the pack, or retrofitted to make an existing one behave.

Applications

Wherever heat must leave and the sink will not sit still.

The bays, loops and shelters that need cooling below ambient with a mass budget attached.

A · 01Airborne equipment & electronics bays

A · 02Liquid-cooled electronics loops

A · 03Transportable shelters & cabins

A · 04Mobile & marine platforms

A · 05Test cells needing compact cooling

A · 06Development & qualification programmes

FAQ

Common questions.

Plain-language answers from the engineering team.

Q · 01 Why can’t you just fit a smaller version of a ground chiller?

Because almost every assumption a ground design rests on is untrue in the air, and removing mass does not repair them. A ground chiller rejects heat to an ambient that is effectively constant, draws from a supply that is stiff and unlimited, sits on a floor that does not move, and is allowed to weigh what its duty requires. An airborne pack faces the opposite of all four. Its sink is ram air, so the condensing condition moves continuously with altitude and speed, and the worst case is a combination of hot, thin air and high load rather than a single design temperature. Its electrical supply is finite and shared, so starting current and power factor are somebody else's problem too. It is shaken and manoeuvred, so every joint, mount and line run is a structural item. And its mass and volume are paid for directly out of what the platform could otherwise carry. The consequence is architectural, not cosmetic: a compact high-speed compressor instead of a slow heavy one, heat exchangers that buy their surface with fine fin geometry rather than frontal area, short well-formed lines, the minimum refrigerant charge that will still run the cycle, and control that is stable across the whole envelope rather than around one comfortable operating point. A shrunken ground unit ends up heavy for its duty and marginal everywhere — the two failure modes you were trying to avoid.

Q · 02 What exactly does “size it for the corner of the envelope” mean?

It means the design point is a combination of conditions, not a temperature. Cooling capacity depends on how easily heat leaves the condenser, and that depends on the temperature of the air arriving, how much of it there is, and how much pressure drop you are allowed to spend pushing it through. As the platform climbs, air density falls, so the same face area delivers less mass flow and the same core rejects less heat. As it goes faster, ram effects raise the temperature of the air arriving, reducing the temperature difference doing the work. Meanwhile the heat load is set by whatever the platform is doing, and it is not obliged to be small when the air is unhelpful. The design case is therefore the worst simultaneous combination the envelope permits — high ambient, low density, high load, limited air-side pressure drop — and it must be agreed in writing at the start, because it drives compressor displacement, condenser surface and ultimately the mass of the whole pack. Sizing against an average condition produces a machine that tests beautifully and then disappoints at exactly the moment it is needed. The other half of the same discipline is checking the mild corners too: a cycle optimised only for the hardest case can become unstable at low load or low ambient, which is why control and expansion-device selection are part of sizing rather than a later refinement.

Q · 03 Why is oil return such a preoccupation?

Because the compressor's lubricant does not stay in the compressor, and an airborne installation gives it many more chances to get lost. In any vapour compression circuit a small amount of oil is carried out with the discharge gas and travels the whole loop, and it only comes home if the refrigerant is moving fast enough in the right places to carry it — which means line sizes, velocities, routing, rises and traps are all lubrication decisions rather than plumbing details. On the ground the geometry is fixed and gravity is predictable, so a conventional design works. In the air, neither holds. Attitude changes move where liquid pools and can strand oil in a low point that was not low yesterday. Low-load operation reduces velocity, sometimes below what is needed to lift oil at all. Cold-soak starts bring the added problem of refrigerant that has migrated and condensed into the compressor overnight, diluting the oil and threatening a liquid slug at start-up. And the consequence of getting it wrong is not degraded performance, it is a bearing failure. So oil return is designed deliberately — velocity checks at minimum load, routing and trap arrangement chosen for the attitude range, charge management and where the receiver sits — and then it is demonstrated at the awkward combinations rather than assumed from the rating point.

Q · 04 Why measure leak rate after the environmental testing?

Because a leak rate measured on a new, undisturbed pack tells you about the workmanship, and a leak rate measured after vibration and thermal cycling tells you about the service life — and only the second one is a useful prediction. A vapour compression circuit is a closed system holding a charge that must last for years, because there is rarely any convenient way to top it up in service, and losing charge does not fail cleanly: capacity fades, superheat drifts, the compressor runs hotter, and the first symptom is often something that looks like a different fault entirely. What attacks the seal is precisely what the environmental sequence reproduces. Vibration works on brazed joints, on threaded connections, and on any line run whose natural frequency the installation happens to excite. Thermal cycling expands and contracts dissimilar materials against each other, working loose what vibration has already fretted. Manoeuvre loading pulls on the mass of the components themselves, which is another argument for keeping them light. So the meaningful acceptance test is: charge it, put it through the vibration and temperature sequence it will actually meet, and then measure how much it holds and how fast it loses it. That is also why joint design, brazing procedure, line support and mount selection are treated as qualification items on this class of equipment rather than as shop-floor decisions.

Q · 05 How does this differ from your ground cart and your liquid cooling unit?

Three machines, three genuinely different problems. The ground air-conditioning cart runs the same thermodynamic cycle with none of the same constraints: it is wheeled up to a parked aircraft, rejects heat to a fixed ambient on an apron, draws from a ground supply, and may weigh whatever its duty needs — so it is optimised for capacity, robustness and serviceability rather than for kilowatts per kilogram. The liquid cooling system and coolant distribution unit is airborne, but it moves heat rather than making cold: it circulates coolant, distributes it to distributed loads and controls flow and temperature, and it can never take a load below the temperature of whatever it ultimately rejects into. That limitation is the entire reason this pack exists — when the load must sit below ambient, only a refrigeration cycle will do it — and the two are natural partners rather than alternatives: the pack makes the cold, the distribution unit delivers it where it is needed. The ECS test bench is the third relative and the easiest to distinguish: it is the machine that tests equipment of this kind, applying loads and conditions and measuring what comes back, which is a different discipline from designing the article under test.

Q · 06 What do you build, what is bought in — and what is claimed?

Divided honestly. What Neometrix provides: the cycle design and sizing against the agreed envelope corner, including the off-design and stability cases; compressor and drive integration with anti-vibration mounting, soft start and protection; the compact heat exchangers and their installation, sized within the air-side pressure drop available; line routing, forming and brazing, which on this class of equipment is a qualification activity rather than a fabrication one; charge and oil management — charge determination, receiver sizing, velocity and trap design, and demonstration of oil return at low load and at attitude; control and protection, proven against stepping loads, cold-soak starts and conditions beyond the envelope; vibration and environmental qualification with leak rate measured after the sequence rather than before; and installation, commissioning, documentation, training, spares and AMC — including build to the customer's own specification, which is how requirements of this class are framed. What is bought-in certified: compressors, heat exchanger cores, valves, sensors and control hardware — proprietary products of established makers, integrated rather than imitated. What is the customer's: the platform, its heat loads and how they vary, its ambient and altitude envelope, and the acceptance limits the pack must meet. And the record, stated plainly: equipment of this class has been quoted against successive airborne vapour compression system requirements for a defence research organisation, in each case as a system with its accessories. No delivered airborne vapour compression system is claimed; the class is engineered to order, around the envelope it has to cover.

↗

The thermal management family from Neometrix.

Make the cold, move the cold, or prove the machine that does either.

↗ Ground

Ground Air-Conditioning Cart

The same cycle with a fixed sink and no mass budget — wheeled to a parked aircraft.

↗ Distribute

Liquid Cooling & Distribution Unit

Moves heat rather than making cold — the natural partner to this pack.

↗ Prove

ECS Test Bench

The machine that tests equipment of this kind, rather than the equipment itself.

Browse all Neometrix product lines.

Get a quotation

Send the heat load
and the envelope.

The projects desk replies within two working days with a clause-by-clause compliance matrix and a budgetary quotation. Write to [email protected] or use the form.

Enquire — airborne cooling packs Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 ENGINEERED TO ORDER — AIRBORNE VAPOUR COMPRESSION SYSTEMS THE HEAT SINK MOVES · MASS AND VOLUME ARE THE SPECIFICATION · THE CHARGE IS THE QUALIFICATION ENGINEERED IN NOIDA · INDIA

The heat has to go somewhere. At altitude, somewhere keeps moving.

The cycle is ordinary. Everything around it is not.

Built for the corner

Kilowatts per kilogram

The charge is the qualification

Reject, carry, contain.

Compressor & Drive

Condenser & Ram-Air Side

Evaporator & Load Side

Control, Charge & Accessories

Reference packs, built to the envelope.

Where airborne cooling goes wrong

One cycle, four installations.

Air-Cooled Load Packs

Liquid-Loop Packs

Ground & Shelter Variants

Accessories, Control & Charge

Wherever heat must leave and the sink will not sit still.

Common questions.

The thermal management family from Neometrix.

Ground Air-Conditioning Cart

Liquid Cooling & Distribution Unit

ECS Test Bench

Send the heat load
and the envelope.

Similar Products

Share This Page

The heat has to go somewhere. At altitude, somewhere keeps moving.

The cycle is ordinary. Everything around it is not.

Built for the corner

Kilowatts per kilogram

The charge is the qualification

Reject, carry, contain.

Compressor & Drive

Condenser & Ram-Air Side

Evaporator & Load Side

Control, Charge & Accessories

Reference packs, built to the envelope.

Where airborne cooling goes wrong

One cycle, four installations.

Air-Cooled Load Packs

Liquid-Loop Packs

Ground & Shelter Variants

Accessories, Control & Charge

Wherever heat must leave and the sink will not sit still.

Common questions.

The thermal management family from Neometrix.

Ground Air-Conditioning Cart

Liquid Cooling & Distribution Unit

ECS Test Bench

Send the heat loadand the envelope.

Similar Products

Share This Page

Send the heat load
and the envelope.