Based on measured wall temperatures made by an infrared camera the flow and temperature fields were computed for an atrium. The nature of this atrium is a large enclosure inside a school building surrounded by halls and classrooms. Within a hybrid ventilation concept the stack effect during the summer time is used to form the main driving force for the night cooling of the classrooms. Time dependant computations were carried out to obtain the flow and temperature fields inside the atrium under various boundary conditions.
Decision about the use of natural, mechanical or hybrid ventilation system in a building should be taken at the early stages of the building design. While for a mechanical system the decision may be taken on the grounds of purely deterministic procedures, the use of natural forces requires a different approach. Therefore, a simple tool is needed which, given a few important and readily known building parameters and information about the local outdoor climate, enables the designer to determine the most suitable ventilation system.
As part of IEA Annex 35 "Hybrid Ventilation in New and Retrofitted Office Buildings" a number of pilot study buildings are monitored for demonstration of hybrid ventilation performance. The monitoring programmes investigates the performance regarding indoor air quality (IAQ), thermal comfort, control strategies and energy consumption. This paper presents detailed measurements from the Danish contribution. Detailed results from short-term measuring periods are presented.
This paper presents a stochastic single zone model for a hybrid ventilated building. Wind pressure and stack effect are used to drive air through the enclosure assisted by a fan in case of insufficient natural driving forces. Based on Monte Carlo Simulation, the model calculates the time varying airflow rate considering the random nature of input. An important aspect when considering stochastic models for hybrid ventilated buildings is the control strategy. The airflow in the present model is controlled by a damper and a fan using a PI controller.
In this paper, a full-scale test house constructed in Tohoku University, Japan and some kinds of residential ventilation systems including hybrid ventilation within it is described firstly, and then the ventilation systems' performance is evaluated by field studies and numerical simulations.
Three hybrid ventilation concepts are described: alternate use of natural and mechanical ventilation; fan assisted natural ventilation; stack and wind supported mechanical ventilation. The concepts described comprise some newly constructed rather advanced buildings but also some existing more traditional type buildings. All buildings with hybrid systems up till now are far from what might be the optimum solution. There is a knowledge gap especially on dimensioning and control of hybrid ventilation systems.
To investigate the possibility of indoor air quality (IAQ) control by hybrid energy saving ventilation with an air cleaner using the sorption effect of building materials, this paper describes the identification to estimate the parameters related to the sink effect of materials, the concept of the novel air cleaner, and the performance evaluation of IAQ control for a house installed with the hybrid ventilation system to remove chemical contaminants by computer simulation.
This paper summarizes part of the work held at ENTPE within the framework of the IEA Annex 35 project. The aim of the work is to develop and experimentally evaluate control strategies for hybrid ventilation systems to provide comfortable indoor environment and good air quality by combining the best aspect of natural and mechanical ventilation. To reach this target and asses the physical model elaborated in this project, a test cell "HYBCELL" has been designed within the laboratory.
Describes how a Wisconsin engineer is using basic thermodynamic principles and readily available equipment to design innovative heating, ventilating and air conditioning systems. The hybrid HVAC designs offer two crucial elements: supply ventilation composed of 100% outdoor air and significantly reduced energy consumption. The new systems are both competitive in price to conventional systems and also less expensive to maintain. In one case study the hybrid system ventilates a 33 year old school building with 100% outdoor air and reduces building energy costs by at least 21%.
When natural ventilation is being used, the quality of the air inside a building depends on the quality of the outside air. What is the outside air quality trend in the urban environment and what are the forecasts for the future? How is air quality measured and what are the expected European standards for outside air quality in 2010? The implications of these developments for the hybrid ventilation of buildings close to roads and motorways are explained.
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