Flat metal plates with an inner channel along which a liquid coolant circulates are used in various engineering applications as the basis of cooling systems, for applications where control of the maximum temperature or the temperature distribution is required, such as electronic devices, PV cells, or electric batteries. The shape drawn by the channel across the plate directly affects the cooling capacity and the pressure drop associated with the circulation of the coolant. In this work, the cooling performance of flat plates with an inner channel of circular cross section through which water circulates is evaluated experimentally. A novel configuration with a shape inspired by the outline of cruciform flowers is proposed and compared with a traditional square-shaped configuration to quantify the improvement on the cooling capacity, keeping the same volume of liquid in both channels. The flat plates were made of aluminum and built by a 3D printer. An experimental facility was designed and optimized to characterize the cooling capacity of the plate for various flow rates of cold water. The facility allows to control the ambient temperature, the temperature of the liquid at the inlet of the plate, and the flow rate of cooling water. An infrared camera measures the temperature distribution of the top surface of the plate. The temperatures of the cooling water at the inlet and outlet of the plate are also measured. The experimental tests were carried out for transient refrigeration, starting with the plate at a selected temperature and refrigerating it with a laminar flow of cold water. Three Reynolds numbers of the cooling water were evaluated, namely 750, 1250, and 1750. The time evolution of the plate temperature distribution and its characteristic values were studied and compared between the different configurations proposed, showing the improvement that can be attained with the cruciform configuration. The high repetitiveness of the experimental procedure is proved by the low deviations for five replicates of each Reynolds number measured, which is below 5 % in all cases.