cylinder 39 s crossover ports 148 and 152 have a generally rectangular configuration with arced parallel top and bottom sides the valve housing 39 s cold and hot water supply ports 160 and 162 are generally square with radiused corners and are physically larger than the valve cylinder 39 s crossover ports 148 and 152 in this way there is minimal restriction offered by the valve housing 39 s supply ports and the volume of coolant allowed to the heat exchanger is maximized the valve housing 39 s cold and hot water return ports 164 and 166 are equilateral triangular shaped with two radiused corners the non radiused corners face each other this configuration serves to help characterize the flow it allows the flow through the valve 102 to have a more tapered response to the percentage opening of the valve and the flow of fluid through the valve often referred to a chacteerizing when a valve has radical changes in flow with a small opening that valve has greatly reduced its usefulness for control applications characterizing of the return ports of the valve so that it has close to an equal percentage characteristic ensures good stability of control this type of characteristic produces a linear variation in thermal output according to the amount of opening of the valve the increase in flow as the valve is opened is very slow and controlled this produces better part load behavior and improved stability of control while also optimizing energy consumption because of this design there is no need for a separately installed flow restricting orifice or characterization disk to customize the flow response to match a more linear heat transfer result about.