In a data cetner, a coil wall is installed along one or both sides of serveroom. It consists of a chilled-water coil and fans, forming a large continuous wall.
A Concept
Coil Wall
The basic operating principle is simiar to that of a CRAH(Computer Room Air Handler), where air passes through a cooling coil supplied with chilled water. However, unlike the CRAH, which is a standalone unit, the coil wall is designed as a continuous panel system intergrating into the room structure.
CRAC/ CRAH
- CRAC(Computer Room Air Conditioner: A CRAC contains a refrigenrant and a compressor within a single unit (DX type)
- CRAH(Computer Room Air Handler): A CRAH contains only a chilled-water coil and fans. Chilled water is suppplied from a chiller located outside the sever room.
Performance perspective
Coil wall
- A coil wall, consisting of large-scale coils and fans , is used to cover high-density racks in the server room. It offers high energy efficiency becuase effective heat exchange can be achieved with a low delta-T and low fan speed.
CRAC/ CRAH
- A CRAH system is advantageous for larege-scale data centers connected to chilled-water plant, while a CRAC unit is more suitable for medium or small-scale data centers that do not use a chiller.
Form an Application and operation Perspective
Coil Wall
It is suitable for unified design at the initial stage if the data hall is designated as a high-density zone.
By modularzizing fans and valves, it is easy to build a structure in N+1 or N+N configuration, as allowing the entier wall to continue operating even if some molues fail.
CRAH/CRAC
These systems allow flexible, unit-based expansion in incremental deployment scenarios (such as additional racks or thermal loads) or in multi-tenant colocation enviroments requiring mixed-density configurations.
CRAC units are still widely ued in legacy building without a chiller plant, small IT rooms, and edge data centers, while CRAH units are mainly applied in campus-type data centers equipped with a central cooling plant.
Ref.https://www.researchgate.net/figure/Layout-of-CRAC-a-and-CRAH-b-cooling-solutions_fig1_381272054