First and foremost always allow plenty of cool air for drying. That is, leave the laundry window or door open. If in a closed cavity do not box the dryer in. Leave the doors for the compartment open while the dryer is on. Effective drying may not be achieved if the dryer has to operate in a 'hot box'.
Rear vented tumble. The original tumble dryer. Clothes tumble in a single direction action . The vent is at the rear and a flue can be attached to take the hot moist air away.It is advisable not to vent into the ceiling cavity, but to vent right through the ceiling space and through the roofing material to the atmosphere. If the situation allows, venting through the wall is convenient. There is a 'flap vent' available to cover the through the wall flue so that the vent is closed when the dryer is idle. The 'chimney' style can be covered with a 'lid' of some sort , but allowing the hot moist to pass. These rear vented dryers have a filter in the rear of the drum. The filter must be cleaned every time the dryer is used. Build up of fine fluff is highly inflammable and could, and has, caused fires. Be very diligent about cleaning this filter. Filters made of foam can be washed carefully. Mesh filters can be cleaned with a damp cloth, or just lick your fingers and wipe it. You will be amazed at how easily it comes clean with 'licked ' fingers. Owning this type of dryer that is vented properly is simple and easy. These are easy to repair and give the least amount of trouble, once you have taken the trouble to set them up.
Reverse tumbling rear vented dryer. Same as above but the drum turns both ways to assist with keeping the load tangle free.
Front vented dryer Works the same as rear vented but the airflow comes out through a filtered front door.
Condenser tumble A dryer that collects the water from the clothes in a container mounted like a drawer in the control panel, or the water can be evacuated to the drain by a small tube. A condenser, that looks a bit like a car radiator, is mounted in a drawer at the bottom of the appliance, A fan draws air from the atmosphere to cool the condenser., The hot circulating air which is controlled by a heater element and sensors, contains the moisture from the clothes. As the condenser is colder than the hot air from the dryer, the water in the hot air 'condenses' and falls into a reservoir. There is a water pump to deliver this water to a storage container or into the waste tube and down the drain. The user maintenance of this type of appliance is very important. The condenser must be cleaned regularly. It builds up with lint, and if not cleaned will cause unnecessary expense eventually. A build up of lint can find it's way into the water pump and 'jam' it. Keep the condenser clean. Take it outside and 'hose' it out. This condenser dryer is an excellent way of keeping the laundry 'clean' and free from fluff and moisture if venting of a simpler machine is not suitable. Most suitable for use in an apartment or an inside laundry where ventilation is limited. These dryers cost about twice as much as a similar quality vented machine mentioned above. User tips click here
Heat pump dryers works with refrigeration. There is no heating element. The 'refrigeration device' cools the condenser and heats the load. Just like a refrigerated air conditioner. So there is a temperature difference between the hot air passing through the dryer containing moisture from the clothes, and the cold condenser. Moisture in the air from the wet clothes condenses and falls into a reservoir and is pumped into a container to be emptied by the user. ( Exactly like the condenser dryer above) The drying temperature on the hot side output of the heat pump is about ninety degrees, but the heat loss through the air flow drops the temperature to about fifty five degrees. This is the effective drying temperature for the garments, so the drying is slightly cooler than other dryer types and the drying time can be shorter. The cooling side of the heat pump operates in the low twenties, so creating a cool condenser to effectively 'drop' the moisture into the reservoir from the hotter air from the garments via the condenser.The process is therefore kinder to the clothing and more gentle.This type of machine is much cheaper to run . As low as one third the cost of other dryers is reported. The initial outlay can be around $2500. User tips click here.
Tip..... Combination units, that is, Washer-Dryers don't work as you might think. If the washer is rated at say 6kg capacity, and you want to dry the load too, you can only load the machine with 3kg of washing. That is, using the dryer feature as a full cycle halves the capacity of the machine. Also it takes 'hours' more time to completely finish the job. Separate appliances suit most people the best. Ask Tony Having said that, one washer dryer of 9kg capacity will dry a 4.5kg load in 5 hours. That seems a long time, but it does it without user intervention. This might be considered convenient, but to be practical you will need a very large machine to achieve this load size. How many 9kg or 10kg machines are there? Not many and they are expensive to buy. Condenser washer-dryers use extra water to operate the condenser action too.
Steam feature in a dryer dryers.... just for freshening up really.
My advice is to 'keep your feet on the ground' and consider the most practical and effective machine for you. Think about the cost of maintenance in years to come, and whether you can easily set up the simplest dryer.Ask Tony All you really need to achieve is to dry clothes with the effective disposal of the moisture for the lowest cost in your situation.
Also some machines have added features like anti crease, and degrees of dryness (e.g. iron dry feature leaves a slight amount of moisture in the garments for easier ironing) Consider the need for these features. The use of later technology with NTC devices in replacement of thermostats does allow the more sensitive moisture measurement in the garments being dried.
An older model Hoover external vent dryer. I fixed thousands of these. They hung on many walls in Australian houses. Wall mounted dryers are on the way out now with the condenser action dryers and heat pump dryers on the way in.
The ultimate drying machine.
Siemens Heat Pump Dryer
This one I have in my own house.
Only draws low current for maximum power saving. Dry to your hearts content without worrying about the power bill.