Expalin what is the reason for the connection of flow transmitter at the upstream of the control valve
The reason for the installation of the flow transmitter, to the upstream of control valve is because of the pressure drop of the control valve. so due to the pressure drop in the control valve the flowmeter will not measure the required flow if the control valve is installed upstream.
The valve removes energy from the flow stream; it does not remove mass.
Upstream flow and downstream flow is the same. Otherwise the mass in the pipe would have disappear somewhere and mass, inside the pipe, does not disappear.
What changes is the pressure due to the pressure drop of the valve. The upstream pressure is higher than the downstream pressure.
The reason flow meters are upstream of a control valve is that the control valve creates turbulence which disrupts the flow profile that most flow meters require when the installation calls for X pipe diameters upstream and Y pipe diameters downstream of straight run pipe in order to get a reasonable flow profile.