Consider a device with one inlet and one outlet. If the volume flow rates at the inlet and at the outlet are the same, is the flow through this device necessarily steady? Why?
For a flow to be steady, the properties should not change with respect to time. Generally, the fluids are considered to be incompressible when the density remains constant with respect to time.
A flow is steady when the mass flow rate through the device is constant. The state of density has not been mentioned.
Hence, the flow through the device is not necessarily steady.