A cooling system for transferring heat from a heat load to an environment has a volatile working fluid. The cooling system includes first and second cooling cycles that are thermally connected to the first cooling cycle. The first cooling cycle is not a vapour compression cycle and includes a pump, an air-to-fluid heat exchanger, and a fluid-to-fluid heat exchanger. The second cooling cycle can include a chilled water system for transferring heat from the fluid-to-fluid heat exchanger to the environment. Alternatively, the second cooling system can include a vapor compression system for transferring heat from the fluid-to-fluid heat exchanger to the environment.
