Question

During suction stroke of a reciprocating pump separation may take place

Answer 1

Reciprocating pumps operate by drawing liquid into a chamber or cylinder by the action of a piston, a plunger or a diaphragm; the liquid is then discharged in the required direction by the use of check valves. This results in a pulsed flow.

There are three classes of reciprocating pumps:

1. Piston pumps

2. Plunger pumps

3. Diaphragm pumps

Fundamentally, the action of the liquid-transferring parts of each of these types of pump is the same: a cylindrical piston, plunger or bucket, or a round diaphragm being caused to pass or flex back and forth in a chamber.

Reciprocating pumps are equipped with inlet and discharge valves, the operation of which is synchronised with the motions of the piston. In modern units, these are check valves operated by pressure difference. That is, when the pump is on its suction stroke and the pump cavity is increasing in volume, the pressure is lowered within the pump cavity, permitting the higher suction pressure to open the suction valve and allowing liquid to flow into the pump. At the same time, the higher discharge-line pressure holds the discharge valve closed. Likewise on the discharge stroke, as the pump cavity is decreasing in volume, the higher pressure developed in the pump cavity holds the suction valve closed and opens the discharge valve to expel liquid from the pump into the discharge line.

One basic disadvantage of a reciprocating pump is the velocity surge that occurs during the stroke. One solution is to use more than one pumping element in parallel. A simplex pump possesses only one plunger or piston, a duplex has two, a triplex three, and so on.

Piston-type pumps may be single or double-acting; i.e. pumping may be accomplished from one or both ends of the piston. Plunger pumps are always single-acting.

There are two basic types of drives. A power pump is driven by a driver like a motor, turbine, etc. A direct acting pump is driven by steam, gas, air, etc.

The overall efficiency for a powered reciprocating pump typically will be 85 to 92% when operating at over a 50% load factor. The efficiency of direct-acting pumps will be lower, depending primarily on their speed.

Reciprocating pumps offer a particular advantage with slurries, highly viscous liquids, and where a high fluid head is required. Additionally, because of the slower speeds involved, maintenance costs of reciprocating units tend to be less than for centrifugal pumps.

Answer 2

Answer:

In refrigeration and air conditioning systems, the suction pressure' is the intake pressure generated by the system compressor while operating. The suction pressure, along with the suction temperature and the wet bulb temperature of the discharge air are used to determine the correct refrigerant charge in a system.