UC San Diego

Natural and forced displacement ventilation offer promising strategies for cooling buildings in an energy efficient manner. However, there is the issue of whether or not they can provide adequate indoor air quality. Here, we investigate this in two studies - one for passive and the other for particulate contaminants. The complex internal stratification of buoyancy, typical of displacement systems, affects the transport of contaminants in a non trivial manner. While on average traditional and modern low energy ventilation systems are comparable regarding efficiency of contaminant removal, we show that the detailed vertical distribution of contaminants tells quite a different story regarding personal exposure. Further, most previous studies on natural displacement ventilation focus only on steady states, while most true buildings have continuously changing heat loads. Here, two projects on transients in natural displacement ventilation are presented. The first studies the influence of sudden changes in heat loads, while the second focuses on heat sources that vary in a periodic fashion. Many benefits of natural ventilation are observed, including that it is self controlling in a very favorable manner and that a well designed space is capable of handling even very large changes in heat load. This thesis presents a separate investigation of contaminants in coastal aquifers. Due to buoyancy effects, saltwater from the ocean often intrudes into aquifers, which gives rise to a nontrivial flow pattern that is very different from that typical of inland aquifers. Using a simple mathematical model, we investigate the influence of these flow patterns on the transport of conservative contaminants in a coastal aquifer. We find that depending on the specific characteristics of the aquifer that the saltwater intrusion can play a significant role on transport. It forces contaminant towards the upper seaward boundary, thus causing elevated contaminant discharge into the surf zone at beach areas