A Natural Gas-Driven Highly Efficient Thermo-Vacuum Clothes Dryer

Modern laundry drying is energy-intensive, consuming on average 630,000 Btu (664 MJ) of heat (for each 1,000 pounds of wet laundry), which is released into the atmosphere along with 200 pounds of steam. Additionally, the fans in dryers consume 40 kW/h of power to blow hot air through the same amount of laundry. This project will develop a thermo-vacuum drying method that allows intensification of the drying process using a pressure and temperature difference that removes moisture 5–10 times faster than any conventional drying method. Its operation relies on heat produced by an integrated steam boiler that circulates in the closed cycle between the vacuum ejector and the rotary drum. The system enables continuous heat recuperation, which makes the process highly energy efficient. The innovative concept will save up to 50% of the drying heat and almost 100% of the water entrained in the wet laundry. The recovered water can be recycled to wash the next batch of laundry, and the surplus heat can be used to preheat the water. Electrical power will be consumed only for centrifugal drum rotation and the automated control system. The combined energy factor (CEF) is expected to be 6.0 or higher, which is at least 50% higher than in conventional laundry dryers. Non-energy benefits of the thermo-vacuum drying method include simple design, high durability, low maintenance requirements, and reduced operational cost.

Project Impact

This technology will have a transformational impact on the state-of-the-art clothes drying process, leading to at least 50% energy savings in the commercial cloth-drying sector. It will save significant amounts of water, which can be recycled to reduce, by at least 20%, the amount of water drawn to wash a subsequent load of laundry. The recovered heat can be used to reduce, by at least 10%, the energy needed for water preheating. The improved washing process also will increase the average life of laundered fabrics by 100%. Large-scale deployment of the proposed concept will result in at least 250 TBtu of overall energy savings and a 5–10 times reduction in the time required for the drying process. Additionally, because the technology allows dryers to be more compact, thermo-vacuum dryers will take up only half as much space as conventional dryers.