All the following can be found in portable or fixed formats . Cool boxes The simplest and cheapest option for portable cooling, passive coolers use reusable packs which you freeze at home before your journey to keep the contents of your cool box chilled. Powered cool boxes Thermo-electric coolboxes These fridges work on a process called the Peltier effect. Mr Peltier discovered this in a simple experiment by joining two pieces of copper wire to each terminal of a battery. He then connected a piece of bismuth wire between the open ends of the copper wire to close the circuit. The effect happens at the two copper/bismuth junctions where one junction will get hot and the other will get cold. Cools around 15 to 20 degrees lower than the ambient temperature outside. Pros, Cheep Easy to use normally comes with a lead to plug in to fag lighter Cons, Use around 40w or 4 amps all the time it was switched on so will only last around 1 day. No temperature control either on or off Absorption fridges 2 way(12v/gas or 12v/230v) 3 way(12v/230/gas) The basic cycle works like this Heat is applied to the generator by electric elements or gas flame. In the generator is a solution of ammonia and water. The heat raises the temperature of the solution until the ammonia boils.The boiling solution rises to the separator In the separator, water separates from the ammonia gas.The ammonia gas flows upward to the condenser. The condenser is composed of metal coils with fins that allow the ammonia gas to dissipate its heat and condense to form liquid ammonia.The liquid ammonia makes its way to the evaporator, where it mixes with hydrogen and evaporates, removing heat from inside the refrigerator cabinet The mixture of ammonia and hydrogen gases flows to the absorber. Here, the water that has spilled from the separator is mixed with the ammonia and hydrogen mixture. Ammonia readily mixes with water and returns to the generator while the hydrogen does not mix, so is separated for return to the evaporator. Absorption fridges will generally achieve a temperature drop of around 25 to 30°C below . Pros, Silent when running Multiple power sources to suit No moving parts Cons, Use around 10 amps all the time it is switched on so will only last around 1/2 day on 12v Will need a hole in the side of the van for the gas flue and a drop hole in the floor if useing gas Limited temperature control thermostat normally only on 230v Needs to be level to work any more than 4 deg slope it may not work Compressor units Compressor units are the same as your one at home The basic cycle works like this The refrigerant gas is passed through a compressor. the gas is compressed and so the pressure on it increases. The temperature of the refrigerant gas in turn increases as a result of the increased pressure and it takes the form of superheated vapor. The refrigerant passes through the heat exchanging pipes and releases heat to the surroundings. the refrigerant cools down due to the loss of heat to the surroundings. As the refrigerant passes through the condenser, its temperature reduce. However, the pressure on the refrigerant remains the same. Due to the reduction in its temperature, the refrigerant gets converted into its liquid form.The expansion valve causes a sudden reduction in the pressure on the refrigerant. Some of the refrigerant evaporates and expands. This expansion results in the lowering of the temperature of the refrigerant.During the evaporation of the liquid refrigerant, it is present in the evaporator, which absorbs the heat from the foodstuffs kept in the refrigerator and thus, cools them. The second law of thermodynamics is used here.The refrigerant again heats up to form a gas. This refrigerant, which is now in the gaseous form, again enters the compressor and the cycle repeats. Compressor fridges will achieve a temperature of around -15 . Pros Full temperature control No holes needed in the van Often comes with a freezer compartment Uses 4 amps but only for around 24% time switched on so should last around 4days Cons Expensive can be noisy when running heavy
Good summary @matty ....may be worth mentioning that absorption fridges need to be installed properly ie. with a sealed cowling, for best efficiency. Very few bus owners take the trouble to do this, and then wonder why their fridge doesn't work that well. With a sealed cowling made from sheet aluminium (fireplace back plate sheet can be had for about £8 from B&Q) these fridges work really well, use significantly less gas/amps... Good basic guide here Also worthy of note...most compressor fridges use Danfoss compressors...these can be mounted remotely if you use a longer hose connection, so you could stick the unit somewhere out of the way, mount it on rubber feet and insulate the compartment for noise
