Cooling Beer With a Wet Paper Towel

Abstract

Beer is a drink often stored warm but served cold, a fact that has led to the development of many ways to cool beer and other beverages rapidly. One method suggests that wrapping a beer in a wet paper towel accelerates the cooling in a freezer, but the effectiveness of this method has been debated across the internet. Does a wet paper towel slow cooling by insulating a beer, or does evaporation from the towel enhance cooling? We performed low-cost, easily reproducible experiments and simulations to answer these questions. We employed a Radau, finite-volume method to solve the heat equation in cylindrical coordinates and simulated each material using the best available thermal conductivities, densities, and specific heats. Experiments were performed in the presence of varying levels of advection in the surrounding air. We found increasing advection by placing beers near the freezer fan reduced the cooling time (\(70^\circ\)F (\(21.1^\circ\)C) to \(45^\circ\)F (\(7.2^\circ\)C)) by 60%-70%; the wet paper towel had a negligible impact. With two lower levels of advection, we found that the wet paper towel reduced the cooling time by approximately 25%. Experiments with multiple thermometers were used to generate time-space diagrams that showed the evolving radial temperature profile in materials. Infrared images revealed convection patterns caused by the warm bottle, even when the bottle was protected from airflow from the fan. Our simulations agreed with our data when we used boundary conditions that mimicked convection. This agreement was also evident when comparing data from an environment without air advection, implying the presence of natural convection.