An air-cooled condensing unit consists of a compressor and an air-cooled condenser combined with various ancillary components, such as a liquid receiver, shutoff valves, filter drier, sight glass and controls. The unit is factory assembled and wired as a complete unit. It provides a convenient method for ‘powering’ a cold room or other cooling equipment that has an evaporator with expansion valve control. Refrigerant vapour from the evaporator is compressed and condensed for return to the evaporator as a high pressure liquid.
Automated permanent refrigerant leak detection systems are products designed to continuously monitor the atmosphere in the vicinity of refrigeration equipment and, in the event of detection of refrigerant, raise an alarm. The early warning of refrigerant leaks allows repairs to be carried out early. This improves the energy efficiency of the refrigeration system and reduces carbon emissions and other greenhouse gases.
Refrigerant leakage may lead to a reduction in the efficiency of refrigeration equipment by causing a direct reduction in COP. Leaking systems can therefore contribute twice to climate change; once through the direct emission of refrigerant, and secondly through increased emissions from higher electricity consumption. Automatic permanent leak detection systems are usually multi-point or single point sensing devices. A single point detector is a self-contained device installed in a plant room in a location where it is likely to detect the early onset of leakage. Multi-point detectors are often aspirated (they draw or suck air down tubes from each sample point to a central detector unit and control panel) and can typically monitor up to 16 locations.
Cellar cooling systems maintain an indoor (cellar) environment at 10-12°C – suitable for the storage of chilled beverages. They are used in pubs, restaurants and hotels, and can be packaged, split or remote. The equipment listed on the ETL has a capacity between 2kW and 12kW, and therefore encompasses most cellar applications.
Many refrigerated display cases are open-fronted, which significantly increases the heat load on the refrigeration system. There are various components available that can be added to reduce the heat load. These include:
- Strip curtains – Overlapping, transparent plastic strips that fit permanently to the open front of display cases. With a typical cost of £170 per blind, the payback period could be as little as 7 months.
- Doors – Sliding or hinged transparent doors that fit permanently to the open front of display cases.
- Covers (bubble lids) – rigid plastic covers that fit permanently to the top of open freezers.
- Blinds – roller-type blinds fitted to the front of open cabinets and may incorporate a motorised control system.
- Enhanced air flow management devices – these enhance the descending air curtain at the front of an open cabinet to reduce infiltration of ambient air.
The use of curtains, doors and covers reduces the heat load on the system, and variation in product temperature will be less. To be effective in reducing the heat load, and therefore improving energy efficiency, care should be taken to ensure they are fitted correctly.
Condensers are used in a refrigeration system to liquefy the refrigerant gas discharged by the compressor. Most condensers used are air-cooled, i.e. ambient air is used to remove the heat from the condensing refrigerant. In an evaporative condenser, the gas to be condensed flows through a coil which is continually wetted on the outside by recirculated water. Air is drawn over the coil, evaporating some of the water. This improves the rate at which heat is rejected from the refrigerant gas, allowing it to condense at a lower temperature relative to the air temperature. Evaporative condensers allow refrigeration systems to operate with lower head pressures and higher efficiencies than can be achieved using air-cooled condensers or water-cooled condensers.
Packaged chillers are factory assembled refrigeration units that are designed to cool liquid using a self contained, electrically-driven mechanical vapour compression system. A packaged chiller includes the refrigeration compressor(s), controls and the evaporator in the packaged unit. The condenser may be built-in or remote. Some packaged chillers may also include a hydronic unit comprising a chilled water buffer tank and a chilled water circulation pump.
Professional refrigerated storage cabinets (PRSCs) are appliances which have one or two solid doors and are typically used for the storage of food and beverages in commercial kitchens. They hold chilled food at between minus 1°C and 5°C and frozen food at between minus 18°C and minus 15°C. Professional refrigerated storage cabinets are usually self contained (integral ‘plug in’) systems. The evaporator is either inside the cabinet, or immediately above it so that the cooled air flows directly into the cabinet. The evaporator is coupled to the condensing unit which is usually located at the top of the cabinet. Cabinets with single and double doors, larder and chest type, counter and under counter models for the storage of chilled and frozen food are listed on the ETL. PRSCs are fitted with solid faced lids, doors or drawers and are not used for displaying food (see instead refrigerated display cabinets section). To be eligible for listing on the ETL, products must have an energy efficiency index which is lower than the thresholds laid out in the ETL criteria, representing best performing products.
Refrigerated display cabinets exhibit food and beverages to best effect for retail purposes. The cabinet incorporates one or more evaporator/expansion device combinations which are either supplied by liquid refrigerant from an integral condensing unit, or from a remote system. All the common types of cabinet are listed on the ETL, including multi decks, chest freezers, upright freezers with glass doors and serveover cabinets. They cover a wide range of storage temperatures from frozen food at minus 18°C, to chilled food at 5°C and at 10°C.
The compressor in a refrigeration system compresses the refrigerant gas from the low pressure of the evaporator to a higher pressure so that it can condense in the condenser, thus rejecting heat to ambient air or water.
Refrigeration system controllers vary enormously in function and complexity. The simplest control is a thermostat which simply controls the temperature of the cooled space. More complex refrigeration systems, such as those with multiple compressors, ideally require more sophisticated control. When used in the right way, these controls can significantly reduce the amount of energy a refrigeration system uses.More information (PDF)