We often hear these complaints in laundry owners’ group chats:

  • It takes a long time to dry clothes in my dryer
  • I am spending too much on air-conditioning (electricity) and dryer (LPG)
  • Clothes in the dryer are turning black. What’s wrong?

While these complaints sound very different issues, one thing that ties all together is how drying works inside machines and the impact of bad air circulation to the output of the drying process.

Allow me to explain:

The physics of drying

Let’s first talk about science. How do clothes dry after getting washed?

When wet clothes contact air, evaporation happens. You’re already familiar with how evaporation happens from the sea: Heat energy from the sun allows water molecules to become water vapor (gas state). It’s the same with moisture on clothes, and higher temperature can accelerate the process. When hot air meets wet fabric, heat is transferred to the fabric and therefore facilitates evaporation.

Now, in several conditions, you can dry clothes naturally without a machine. But if you’re talking about tonnage of fabric, you’ll need machines to accelerate that process.

Dryers work by sucking in air from the atmosphere. A blower pushes air into the belly of the machine, but not before it meets heat energy produced by any of the following – steam, heat from a flame (powered by LPG), or heat from a coil (powered by electricity). This hot air increases the temperature of clothes inside a dryer, facilitating and accelerating the evaporation process.

As the blower pushes in air continuously, the air which is already inside needs to move out. This used air carries water vapor – the output of evaporation – which has no business staying inside a dryer. An exhaust allows used air to exit a dryer, into a series of ducts and back to the atmosphere.

Where operators often go wrong

This process relies mainly on ventilation. Free-flowing air must be present around a dryer so the machine can do its work.

This is the reason why a dryer inside an air-conditioned room, where good ventilation is lacking, will likely struggle to work efficiently.

But there is also humidity and moisture diffusion. When clothes dry, its surrounding air becomes humid because of water vapor. Air can only hold so much moisture until it reaches a saturation point when the drying process becomes inefficient.

Therefore, not only must a dryer effectively push out water vapor during the drying process, but it must also use good, dry air to do its work properly.

It’s the reason why it is harder to dry clothes in Baguio than in Manila and why extra drying time (or extra fabric conditioner) is needed during rainy season. Even when air circulation is good, the drying process becomes hard when moisture in the air is high.

Operators, therefore, must think carefully about putting an air-conditioning machine inside an enclosed area where the dryers are. They must ensure good air flow is present – and this effectively negates any use for an A/C and the electricity expenses that go with it.

Sustainability: Can we reuse exhaust air?

As I have emphasized on a previous article, drying is expensive. So why don’t we reuse exhaust air, which are still hot, to dry more clothes?

You can do this manually. If you are a business owner or operator, try to channel exhaust air into a room which has its own fans to blow hot exhaust air in and blow it out. You can dry clothes here especially for customers who are not on a rush. The key, still, is air circulation to maximize the heat energy from the exhaust air, accelerate the evaporation process, and keep the atmosphere in this room from getting humid.

Check on your dryer

I have already explained how blowers push air inside a dryer but not before the air picks up heat produced by steam, LPG, or electricity.

Of the three power sources, LPG is the cheapest to use by small laundromats. (Steam is perfect for industrial use, while electricity is more advisable for residential or household purposes.)

But LPG has its own unique problems. First, carbon monoxide can darken clothes. Second, one must be cautious about the accumulation of flammable materials, such as lints. Third, LPG tanks must be in well-ventilated areas to avoid disasters when leaks occur.

This is how LPG works: LPG fuels a flame that produces heat energy. Dryer technicians will adjust the right mix of oxygen and LPG to create an effective firing. However, there are instances when the higher heating value (or HHV) is too low and too much carbon monoxide is pumped into the dryer. This blackens the clothes and causes a lot of subsequent problems.

Beyond HHV, laundry operators must always ensure good maintenance of its ducting. Lints blown out along with used air will tend to accumulate in pipes, and over time these block the path of exhaust air, leading to longer drying time. Clean your lint filters regularly.

The business of laundry is drying

In a previous article, I’ve detailed how the business of laundry is more drying than washing. That is true from a cost perspective, but obviously without discounting the fact that an effective wash must still be ensured.

By understanding the science behind drying, laundry business owners and operators can question industry staples (like air-conditioning and too much real estate), adjust their processes, avoid losing money, and speak the truth to customers of how we can help them better.