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How cool are you?


How cool are you?

It is no news that all armed forces require their equipment to outperform standard solutions every single time. This is not just true for normal circumstances, but more often than not the environments these are placed in are harsh and demanding. Given the ever-increasing global warming situation, coupled with an increasing thermal design power (TDP) of chips by almost 50% in the last decade ( it is not surprising that also the armed forces are faced with an ever-increasing need for cooling solutions. The trend of using more sustainable methods for cooling that has been seen in the private market is sure to take over the armed forces too, as savings as much as 80% on cooling expenses are expected.

However, cost factors aside (which are an important factor no doubt), one of the most important things to remember is to choose the best cooling system for your need, which will help not only cut down on costs but be more relevant for your unique situation.

The three most prominent technologies are cold plates, single-phase liquid immersion cooling, and compressor-based air conditioners. In this short series of articles, we will first explain and then compare these three cooling systems. Hopefully, these insights will help you understand the technical differences, enabling you to choose the best solution for your operation.

How Do These Cooling Technologies Work?

Compressor-Based Air Conditioners

A compressor-based air conditioner or vapor cycle system, consists of three parts:

  1. The evaporator, the cold section, is where the pressurized refrigerant is forced through a valve where it expands, boils, and finally evaporates. Heat is absorbed as the refrigerant changes from liquid to gas.
  2. The compressor, which acts as the pump that recompresses the gas into a liquid.
  3. The condenser, which discharges the heat absorbed at the evaporator and the one produced during compression into the ambient environment.


The compressor-based air conditioner is part of the “whole air-cooling process,” which is outdated for several reasons, such as being rather inefficient and complex. In essence, fans (air handler) move outside air into a computer room air conditioning (CRAC) unit where it is cooled. This cool air is then transported to a raised floor and up into the “cold aisle” of the server racks cooling the servers. The hot air exits via the so-called “hot aisle,” where it is collected and moved back to the fan to repurpose it.


Cold plate cooling systems are among the oldest and most popular forms of liquid cooling for both electronics and IT needs.

With “touch,” “direct-to-chip,” or “liquid-to-chip” cold plates, as the name suggests, a metal plate is attached on top a CPU or GPU, which transfers heat through a heat-spreading material from the chip to the plate. Since the plate is cooled with a liquid, a much better conductor of heat than air, the plate can absorb the heat. The heated fluid circulates from the plate through a coolant distribution unit (CDU) to a water circuit connected to a chiller. The cooling liquid is then redirected back to the plate.

Cold plates typically cool CPUs by 60-70% of the total heat load, with air-cooling making up the remaining 30-40%. Thus, cold plate technology is a hybrid solution that involves both liquid and fan-blown air cooling.


Single-Phase Immersion Cooling

Single-phase immersion cooling is based on the principle that air isn’t the best heat conductor, while liquid is better suited. The servers are installed vertically in a horizontally-oriented coolant bath of an electrically non-conductive liquid kept at a user-specified temperature. The heat is transferred through direct contact with server components via the coolant. The hot coolant is then directed to an exit at the top of the rack. It is circulated back through a cooling distribution unit to a warm-water loop. A further heat removal unit, a cooling tower or a dry cooler, finishes the cooling unit.

The cooled liquid is then returned to the heat exchanger rack at a user-specified temperature.

Which cooling technology is the best?

So, which cooling technology is the best for you? In our next article, we will compare these three systems with each other according to upfront costs, running costs, efficiency, cooling capacity, and reliability. Look out for our next article.

While you are here- check out what extreme conditions our Military Environmental Control Units can stand