A rotary isobaric pressure exchanger for transferring pressure energy from a high pressure first fluid to a low pressure second fluid, comprising: a cylindrical rotor configured to rotate circumferentially about a rotational axis and having a first end face and a second end face disposed opposite each other with a plurality of channels extending axially therethrough between respective apertures located in the first and second end faces; a first end cover (62, 114) having a first surface that interfaces with and slidingly and sealingly engages the first end face, wherein the first end cover (62, 114) has at least one first fluid inlet and at least one first fluid outlet that during rotation of the cylindrical rotor about the rotational axis alternately fluidly communicate with at least one channel of the plurality of channels; a second end cover (64, 100) having a second surface that interfaces with and slidingly and sealingly engages the second end face, wherein the second end cover (64, 100) has at least one second fluid inlet and at least one second fluid outlet that during rotation of the cylindrical rotor about the rotational axis alternately fluidly communicate with at least one channel of the plurality of channels; and a first port disposed through the first surface of the first end cover and/or a second port disposed through the second surface of the second end cover, wherein during rotation of the cylindrical rotor about the rotational axis the first and/or second port is configured to fluidly communicate with at least one channel of the plurality of channels within the rotor, characterized in that the first fluid inlet comprises a high pressure first fluid inlet, the first fluid outlet comprises a low pressure first fluid outlet, the first surface comprises a first transition area from the low pressure first fluid outlet to the high pressure first fluid inlet, and the first port is disposed on the first transition area of the first surface, and/or that the second fluid inlet comprises a low pressure second fluid inlet, the second fluid outlet comprises a high pressure second fluid outlet, the second surface comprises a first transition area from the high pressure second fluid outlet to the low pressure second fluid inlet, and the second port is disposed on the first transition area of the second surface. a cylindrical rotor configured to rotate circumferentially about a rotational axis and having a first end face and a second end face disposed opposite each other with a plurality of channels extending axially therethrough between respective apertures located in the first and second end faces; a first end cover (62, 114) having a first surface that interfaces with and slidingly and sealingly engages the first end face, wherein the first end cover (62, 114) has at least one first fluid inlet and at least one first fluid outlet that during rotation of the cylindrical rotor about the rotational axis alternately fluidly communicate with at least one channel of the plurality of channels; a second end cover (64, 100) having a second surface that interfaces with and slidingly and sealingly engages the second end face, wherein the second end cover (64, 100) has at least one second fluid inlet and at least one second fluid outlet that during rotation of the cylindrical rotor about the rotational axis alternately fluidly communicate with at least one channel of the plurality of channels; and a first port disposed through the first surface of the first end cover and/or a second port disposed through the second surface of the second end cover, wherein during rotation of the cylindrical rotor about the rotational axis the first and/or second port is configured to fluidly communicate with at least one channel of the plurality of channels within the rotor, characterized in that the first fluid inlet comprises a high pressure first fluid inlet, the first fluid outlet comprises a low pressure first fluid outlet, the first surface comprises a first transition area from the low pressure first fluid outlet to the high pressure first fluid inlet, and the first port is disposed on the first transition area of the first surface, and/or that the second fluid inlet comprises a low pressure second fluid inlet, the second fluid outlet comprises a high pressure second fluid outlet, the second surface comprises a first transition area from the high pressure second fluid outlet to the low pressure second fluid inlet, and the second port is disposed on the first transition area of the second surface.