Due to increased use of high-performance computing in datacenters to cater to huge workloads, old low-performance compute servers must be replaced endlessly with high-performance compute servers. Traditional air-cooling systems are insufficient to provision and run the servers in optimal conditions as the datacenter thermal footprint or rack density grows, resulting in thermal throttling. To sustain the growing needs, Rear Door Heat Exchangers (RDHx) are deployed in existing datacenters along with peripheral Computer Room Air Handling/Conditioning (CRAH/CRAC) units. RDHx transfers heat from the rear end of the racks and rejects it into the facility’s chilled water. This study will demonstrate the suitability of RDHx for low density as well as high density rack applications. A baseline CFD model had a generic datacenter layout with peripheral CRAH/CRAC units and RDHx. Several case studies were conducted by varying the air and liquid inlet temperatures for rack and RDHx, respectively. We also compared active and passive modes of operating RDHx while server fans provide flowrate based on the IT inlet temperature. The paper will also discuss the feasibility of designing a datacenter with only RDHx and no peripheral CRAC/CRAH units while maintaining the thermal envelop. The research will also provide a guideline in implementing RDHx based on the heat load and server design.