Micro-environmental control for efficient local cooling

Abstract

Micro-environment is hereby defined as the air space and environment around a person that directly impacts his/her thermal sensation. Most existing HVAC systems condition the air of the entire room including the unoccupied space, which leaves a big potential to save energy. This study aims at evaluating the performance of three existing air terminal devices (ATDs) to locally remove enough heat from the micro-environment to manage the thermal balance so as not to sacrifice thermal comfort when the ambient unoccupied space temperature is increased by 2.2 °C from 23.9 °C to 26.1 °C in the summer to reduce the external cooling load. A computational fluid dynamics (CFD) model was developed, validated by full-scale chamber tests and applied to evaluate different configurations of the ATDs for local cooling. Results show that the predicted performance agreed well with the measurements, and the selected ATD, with only 50 W cooling power, was always able to remove a sufficient amount of heat from the microenvironment in a room of raised temperature, when the manikin was moved inside a semicircle movement range. The cooling performance of the jet was increased more by increasing the supply air flow rate than reducing the supply temperature and was highly dependent on the shooting angle. The heat flux from the manikin surface is very sensitive to the surface temperature and furniture placement, and proper specification of the surface temperature is crucial for the CFD simulation to match the measured results.

Effects of Semi-Open Space on Micro-Environmental Control

“…A CFD model based on the guidelines given by Russo's validated CFD case (Russo, 2011) was developed and further validated by the experimental work (Kong et al 2017). A 1.8 m × 1.8 m cubicle placed in a typical office space was built in the CFD model ( Figure 1).…”

“…The room modeled is the same as those used in the previous work (Kong et al 2017). The cubicle was created symmetrically around the desk and seated occupant.…”

“…The emission from the wall is used to present the case in which pollutant sources are outside the cubicle and that from the desk to represent the sources inside the cubicle. The μX placed under the table has a supply duct attached to the bottom side of the table and two suction openings on both sides of the box (Kong et al 2017). When the μX is on, the air purification starts to work by taking in contaminated air and supplying clean air.…”

A Review of CFD Analysis Methods for Personalized Ventilation (PV) in Indoor Built Environments

“…There are no relevant standards for the sizes, shapes, and postures of CTMs, and their usage mostly depends on the purposes of research studies. CTMs used a surface area of 1.57 m 2 [36,92] [115], and a simple shape, e.g., rectangular, or exact-shape, as well as sleeping, seated, or standing postures. Most studies used complex CTM geometry, the exception being a rectangular person used to assess the performance of a CMPV system in regard to inhaled air quality influenced by a moving person [94].…”

“…For instance, the human body releases its metabolic heat production to the surrounding environment, 49.3 W by convection, 65.1 W by radiation, 41.3 W by evaporation, and 14.8 W by respiration [136]. Moreover, a total of 115 W for a seated person with very light work was generated, including 70 W of sensible heat loss due to convection and radiation, and 45 W of latent heat loss induced by evaporation and respiration, representing the amount of heat released to the surrounding environment to achieve thermal balance [115].…”