Simulation of a Predominantly Passive Natural Air Cooling System

Climate control is an everyday challenge. With the rapid surge in electricity prices over the past few years, air conditioning operating expenses necessarily increased. The effects, furthermore, of global warming result in increased cooling, and therefore, energy demand. The purpose of this paper is to propose two models that simulate a natural air cooling system. The first model simulates cooling through an earth to air heat exchanger, utilising the soil as a heat sink. The second model simulates the transient cooling of a control volume, which receives cooled air and is open to the environment. A scale model of an earth-to-air heat exchanger system was designed, constructed and used to verify results from the proposed models. Following verification, a real-life size heat exchanger was simulated in order to cool down a room of 60 m(3) within one hour, using only the underground soil as a heat sink. Results showed that a room at an initial 30 degrees C can be cooled down to 20.5 degrees C with a 1.2 m underground heat exchanger and down to 17.8 degrees C if the length is increased to 2.0 m. Only fan power is needed to increase the air's dynamic pressure, resulting in flow conditions. As a result a coefficient of performance between 60 and 80 can be achieved.