Refrigerant Condensers: Types, Operation, and Selection
**Characteristics and Function of Condensers**
Its role is in condensing the refrigerant. Recall that the refrigerant leaving the compressor is in a superheated vapor state and thus enters the condenser. This will give the ‘heat’ (as it is a heat exchanger) to the condensing agent, either water or air, producing a cooling of the refrigerant to reach the temperature of condensation, which will develop a change of state. For that heat exchange between the refrigerant and the condensing agent to occur, the heat exchanger shall be of conductive material, typically a metal surface.
**Types of Condensers**
**Water-Cooled Condensers**
**Double Tube**
Also known as countercurrent, with two tubes of different diameters and concentric (as one goes into another). The fluid is discharged into the space left free between the two tubes and circulates towards the downstream accumulator. The water flows upward into the compressor in a manner contrary to the coolant.
**Multitubular**
These are formed by a metallic envelope, cylindrical, closed at the sides with some covers that can be disassembled for maintenance and inspection. Inside and along the package is a mounted tubular. The materials used vary according to the refrigerant since each has different properties. Water enters the bottom of one side (which is inside a wall that prevents water from entering all the tubes). Thus, it enters the bottom, covering this whole part until you reach the other side, following a path opposite to the refrigerant. The refrigerant from the compressor enters and fills the upper bound. Because of the heat transfer, the fluid condenses and exits through the bottom as a liquid.
**Air-Cooled Condensers**
**Smooth Tube**
Used in small installations, such as refrigerators. The material is copper, and they operate by natural circulation.
**Finned Tube**
These are for higher-capacity facilities. They consist of a coil of copper and aluminum fins. The heat transfer occurs through the tube and fins so that the area of transmission is greatest.
**Mixed Condensers**
They use water and air together to effect condensation. The most commonly used are the evaporative condensers.
**Evaporative Condensers**
Their operation is based on a combination of upstream water and air to effect condensation. They are usually located on the outside; to install them in the interior, one has to provide for the introduction of air.
Their performance is a function of the wet-bulb temperature of the air at the entrance, and the lower the temperature, the greater the yield.
- The compressor unloads the fluid in the condenser, and it flows through the coil, which is inside an envelope of galvanized material.
- At the top is fitted with a line of water jets that spray water over the coil. The water falls through the bottom and is pumped back to the nozzles.
- The fan circulates the atmospheric air upward from one part to another so that before being expelled into the air again, it passes through the cooling coil. Due to the moisture from the water spray, the air is further cooled.
**Difference Between a Condenser and a Cooling Tower**
The basic difference is that in the cooling tower, the condensing agent (water) is cooled and reaches the condenser, while in evaporative condensers, condensation is carried out directly, and the cooling tower is abroad.
**Water Circulation Pump**
To determine the necessary pump, we calculate:
- Required flow (liters/hour)
- Pressure drop in the circuit (m.c.a.)
The pressure depends on the speed with which the electric motor rotates. The pressure drop can be caused by the pipes, elbows, altitude, the circuit elements, etc.