Like many pumps, peristaltic pumps also have inlets and outlets, but there are significant differences between them.
1. Pressure Difference: The pressure at the inlet is actually suction, generated by the rebound of the peristaltic pump tubing. This pressure is generally close to the wall thickness of the tubing; for example, the pressure of a 1.6mm thick tubing is typically around 0.1MPa. The outlet pressure is the pressure generated by the rollers pushing the liquid forward through the tubing, which can be understood as a thrust, but this thrust is smaller than the suction.
2. Liquid Pulsation: At the inlet of a peristaltic pump, the liquid is steadily drawn in very smoothly. At the outlet, however, a vacuum space is created due to the rollers releasing the tubing, causing significant fluctuations in the liquid, generally referred to as pulsation or pulse. The larger the tubing’s inner diameter, the greater the pulsation.
3. Suction Head and Discharge Head: The suction head and discharge head of a peristaltic pump are not significantly different and are related to the suction force at the inlet and the thrust force at the outlet.
4. Inlet and Outlet Height: If the inlet is below the peristaltic pump, it creates suction lift, which reduces the flow rate. Conversely, if it’s above the pump, gravity increases the flow rate. The outlet is the opposite; when the outlet is above the pump, the flow rate decreases; when it’s below, the flow rate increases. However, the magnitude of these increases and decreases is relatively small in both cases.