Refrigeration
Refrigeration System types & Drives
This section looks at each system separately and provides information on how they work:
Cryogenic
A cryogenic system works using liquefied gas that is carried in a vacuum-insulated storage vessel on the vehicle. The gas is automatically injected into the insulated box at the rate required to maintain the correct operating temperature.
Independent diesel engine
This system uses an engine built into the refrigeration unit, which drives the compressor with an integral or remote evaporator. It can be powered by two types of fuel: red diesel, which is the most widely used, or white diesel, which has less environmental impact. An optional particle filter and catalyst can clean the exhaust emissions from a separate engine run on white diesel. In combination with modern common rail diesel engines, the emissions could be reduced by over 90%.
Direct drive
There are two types of system that can be used - the alternator drive and the v-belt drive:
Alternator drive
This system uses an alternator, driven by a belt from the main traction engine, which generates power to drive an electric motor in the
refrigeration unit. The refrigeration compressor is either directly coupled to this electric motor or is driven by it via a v-belt. Fan motors and the control
system are also fed from the alternator output. When using a semi-trailer, tractor units must be fitted with an alternator.
V-belt drive:
This system drives the refrigeration compressor directly from the vehicle engine and is connected by pipe work to the other parts of the
refrigeration system. The fans for the evaporator and condenser are fed by a 12 or 24 volt DC current from the truck, with a total efficiency of battery and
alternator of less than 50%.
Eutectic system (mains electric drive)
This system is constructed from hollow tubes, beams or plates filled with a eutectic
solution*.The system is mounted in the insulated box and used to release the stored cold. A full downloadable version of the “Best Practice” guide to refrigeration is to be found in the members only area. |
