This is determined by the structure of the faucet valve core. If you disassemble the faucet valve core, you will see that the proportion of hot and cold water intake is controlled by the upper and lower ceramic sheets, which have irregular holes. When the handle is placed in the closed position, the upper ceramic sheet blocks the position of the lower ceramic sheet corresponding to the water intake (no matter whether hot or cold water can enter the valve core), and when you lift the handle, the ceramic sheets are displaced to expose the hot and cold water intake holes, and water flows out at this time. When you turn the handle left and right, with the change of the position of the hole, the proportion of hot and cold water will change, thus adjusting the temperature. However, this hole is irregular, so when you adjust the flow rate at a certain angle, the cold and hot water inlet holes will also change in different degrees, that is, the proportion of cold and hot water inlet will change, so the temperature will change, which is specific to your situation. Of course, this hole is symmetrical, and the temperature will not change when the handle is in the middle position to adjust the flow.

According to the law of conservation of heat, the heat loss of the use environment you mentioned can be ignored, and the temperature of the hot and cold water inlet pipe is assumed to be constant, so the temperature of the same proportion of hot and cold water mixed should be constant regardless of the flow rate. But I have also tried, and I can still feel the temperature change in the middle position. Please ask other friends to continue to explore. ?

Combined with the inspiration of 3L, the main reason should be that after you turn down the tap water of the pressure-bearing electric water heater, more cold water enters the water tank, which leads to the increase of hot water outlet pressure, so the hot water quantity becomes larger and the water temperature becomes hotter at the same angle.