Further components of the refrigeration system

Suction-side cleaning filter

In branched pipe works having many soldered or welded joints, formation of scale and other impurities can often not be avoided entirely. This is why the installation of a suction-side cleaning filter with interchangeable block inserts is urgently recommended. The filter elements remain in the system only temporarily, in order to collect detached impurities. Where required (e.g. motor damage), it is also possible to use acid-binding filters.

Installation position upstream of the suction header.

Suction-side suction accumulators

Any suction accumulator that may be required is selected taking into account the maximum and minimum capacities specified by the manufacturer. However, in particular with low temperature applications, the capacity ranges are relatively strongly limited with respect to pressure drop and oil return. If necessary, it is recommended to install several accumulators distributed over the individual sections. In series applications, it is advantageous to design the suction header as a suction accumulator. In most cases, the installation of a special accumulator can be avoided by designing and controlling the system accordingly. An exception are systems with reverse cycling or when there is a danger of intermittent return of refrigerant or oil. Here, in particular the pipe layout with respect to a continuous oil return and a time delay when defrosting individual evaporators must be taken into account.

Condensers, desuperheaters, liquid receivers

For uniform distribution and optimum use of the condenser, only one common heat exchanger should be used. When liquid receivers, desuperheaters and water-cooled condensers are connected in parallel, one pipe joint each must be provided between liquid and gas.

Due to the large capacity range and seasonally different ambient temperatures, a condenser pressure control is required. This largely avoids larger variations in the condensing temperature and the resulting effect on the evaporation temperature. In pressure control, the following aspects should also be taken into account:

• Limiting the minimum possible condensing temperature according to the application limits of the compressors
• "Intelligent" control of the condensing temperature (as a function of load and supply air temperature) through variable air volumes of the condenser fans. For the best possible coefficient of performance (COP), the control algorithm should guarantee an optimum balance between the power consumption of compressors and fans under all conditions.

If a desuperheater is used for heat recovery, in addition to the performance, the refrigerant-side connections must also be taken into account, while the line cross-section must be tailored to the overall performance. The desuperheater may only be installed between oil separator and condenser. If used alternately as desuperheater and condenser, additional measures may be necessary, in order to avoid pressure-side liquid slugging and refrigerant migration.

Evaporators

Depending on the type of compound system, either individual evaporators or a larger number of evaporators will be used. Due to the in most cases large capacity range, in particular for individual evaporators, it may be necessary to have several refrigerant circuits controllable by solenoid valves, each of which a separate expansion valve is assigned to. As protection against large liquid surges during start, the suction gas line should be raised directly downstream of the evaporator (swan neck).
If a pump down system is in place, this measure can be omitted.