MacDonald I.,National Research Council Canada |
Rimmer J.,Price Industries
ASHRAE Transactions | Year: 2011
Stratified air distribution systems are increasingly being installed in Canadian buildings. Field studies have shown that existing guidelines for their design are often not followed leading to oversizing of systems. Simulation offers a design mechanism whereby the performance of a system can be predicted. This reduces the uncertainty over performance and increases the likelihood that the designed system will perform as intended and be correctly sized. In recent years several approaches and models have been developed to model stratified air distribution systems (UFAD or Displacement) in energy simulation programs. While models for UFAD are well advanced those for displacement have attracted less attention. In addition much of the research has focussed on cooling season performance, rather than heating season. The focus of this paper is displacement ventilation modelling in heating season. In the current study predictions are compared to the output from a CFD model. The results show surprisingly little variation between the different energy models in terms of temperature predictions, but a large variation in energy demands. Future work will compare these results to measured data. © 2011 ASHRAE.
Nelson I.C.,Texas A&M University |
Culp C.H.,Texas A&M University |
Rimmer J.,Price Industries |
Tully B.,Price Industries
Building and Environment | Year: 2016
Experiments were conducted in a temperature controlled test room with a passive chilled beam and thermal manikins to measure the effect of heat source locations on the beam cooling capacity. Two configurations of thermal manikins and one configuration using radiant panels were tested through a range of conditions of the supply water to the passive chilled beam. The results of the experiments showed a dependence on the location, but not the type, of heat source on the cooling delivered to the test room by the beam. Thermal manikins placed asymmetrically to the beam location resulted in a 16% reduction in beam capacity as compared to thermal manikins placed symmetrically. Radiant panels oriented symmetrically on the floor of the test room resulted in an equivalent beam cooling rate compared to the symmetrically placed thermal manikins. A model based on fundamental heat transfer equations predicted the beam capacity of the symmetric thermal manikins but could not account for the reduced cooling capacity of the asymmetric configuration. © 2015 Elsevier Ltd.
Fatemi I.,University of Manitoba |
Wang B.-C.,University of Manitoba |
Koupriyanov M.,Price Industries |
Tully B.,Price Industries
Building and Environment | Year: 2013
This paper reports a new set of experimental data and presents an in-depth analysis of the flow physics of a non-isothermal jet stream produced by a large quarter-round corner-mounted displacement diffuser. The air velocity, temperature and turbulence intensity inside the displacement ventilation (DV) jet have been thoroughly analyzed and compared with the reported findings of previous studies and model predictions. Through the experiment, it is observed that the DV jet development is significantly altered by buoyant forces and can be divided into four distinctive zones. The results of the present study refine the physical understanding of the coupled thermal-fluid fields characteristic of a DV jet stream, and are useful for improving the design of the DV system tested. © 2013 Elsevier Ltd.
Arens E.,University of California at Berkeley |
Zhang H.,University of California at Berkeley |
Hoyt T.,University of California at Berkeley |
Kaam S.,University of California at Berkeley |
And 8 more authors.
Science and Technology for the Built Environment | Year: 2015
There is great energy-saving potential in reducing variable air volume box minimum airflow set-points to about 10% of maximum. Typical savings are on the order of 10%-30% of total HVAC energy, remarkable for an inexpensive controls set-point change that properly maintains outside air ventilation. However, there has long been concern whether comfort and room air mixing are maintained under low flows through diffusers, and this concern has prompted variable air volume minima to be typically set at 20%-50% of maximum. RP 1515 evaluated occupants’ thermal comfort and air quality satisfaction in operating buildings under both conventional and reduced minimum variable air volume flow set-points, and measured the air diffusion performance index and air change effectiveness for typical diffuser types in the laboratory. The hypotheses were that lowered flow operation would not significantly reduce comfort or air quality and that HVAC energy savings would be substantial. The hypotheses were almost entirely confirmed for both warm and cool seasons. But beyond this, the reduction of excess airflow during low-load periods caused occupants’ cold discomfort in the warmseason to be halved, a surprising improvement. It appears that today’s widespread overcooling of buildings can be corrected without risk of discomfort by lowering conventional variable air volume minimum flow set-points. © 2015 ASHRAE.
Raftery P.,University of California at Berkeley |
Bauman F.,Price Industries |
Schiavon S.,University of California at Berkeley |
Epp T.,Price Industries
Energy and Buildings | Year: 2015
Underfloor air distribution (UFAD) systems use the underfloor plenum beneath a raised floor to provide conditioned air through floor-mounted diffusers, which typically discharge cool air with both horizontal and vertical momentum components. These systems usually create a vertical temperature stratification when in cooling mode and this has an impact on energy, indoor air quality and thermal comfort. The purpose of this study was to characterize the stratification performance of a previously unstudied type of floor diffuser that discharges air horizontally, with almost no vertical velocity component, and that aims to combine the benefits of both UFAD and displacement ventilation (DV) strategies. We performed 19 full scale laboratory experiments in which we varied the number of diffusers and the internal loads over a range of values typically found in office spaces. We quantified the amount of thermal stratification by measuring the dimensionless temperature at ankle height and found a degree of stratification that is typical of DV systems - higher than is typical in UFAD systems. We developed a model based on these results that can be used to simulate these systems in whole building energy simulation tools, such as EnergyPlus, and simplified UFAD design tools. © 2015 Elsevier B.V. All rights reserved.