Expanded psychrometric landscapes for radiant cooling and natural ventilation system design and optimization

Abstract

Maintaining the thermal comfort of building occupants is a challenge typically negotiated by air based heating and cooling systems that rigidly maintain supply air temperatures and humidity levels. Such a practice overlooks several other design variables, including the mean radiant temperature, TMRT, which is responsible for a significant portion of an occupant's thermal comfort, or air velocity, vair . The increased deployment of low exergy cooling strategies such as evaporative cooling and radiant cooling allows temperature potentials to be efficiently and effiectively leveraged. However, the precise execution and subsequent control of these potentials in air based or radiant systems is driven by incomplete empirically based standards, removing heuristic guiding. Deciding where system setpoints should be for systems that go beyond simple air based cooling is difficult to arrive at through intuition and current metrics, as the inclusion and modulation of other thermal comfort variables such as air velocity, skin temperature, skin wettedness and metabolic rate are not entirely independent variables. The focus of this research is to approach thermal comfort with an occupant-centered stance, comparing heat loss through primary modes of heat transfer generated by an occupant's metabolic rate. In doing so, the holistic integration of all comfort variables currently missing from the literature opens a window into an integrated design landscape including air temperature, TMRT, and relative humidity as the relevant independent variables for thermal comfort. Building on the array of low exergy building systems with integrated evaporative and radiative cooling systems in the literature, this new landscape will be presented as a tool for assessing a new radiant cooling system.