Numerical modeling of laundry drying in a commercial laundry plant: Incorporating water potential as a driving force for heat and mass transfer

Abstract

Increasing energy efficiency and reducing emissions in industrial processes through waste-heat recovery systems are vital. The energy-intensive nature of professional laundry care generates waste heat from machines such as washers, dryers, and boilers. We focused on a waste-heat recovery system tailored for this sector. An accurate drying model is essential for analyzing its energy-saving potential.This study presents a water-potential-based drying model using equilibrium thermodynamics. Two measurement experiments and numerical simulations were conducted to verify the accuracy of the proposed model, and the experimental results were incorporated into the simulations. The first experiment collected and determined laundry samples' basic information and hygrothermal properties, including the surface area, initial weight, and heat and moisture transfer coefficients. The second experiment attempted to determine each laundry item's equilibrium water content and capacity at various humidity levels. Through simulations, a comparison was made between the surface temperature and water content predictions of the existing and proposed models. Experimental results revealed that the laundry surface temperature remained constant during the constant-rate drying period. However, during the falling rate period, it was influenced by water content. The drying characteristics differ based on the material and quilting method. The proposed model improved the temperature and water content predictions by approximately 80.07% and 63.08%, respectively, compared with the existing model. This model can effectively assess laundry drying processes, including the latent heat flux assessment of the indoor environment.