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No compartments or dividing walls Unlike ducting, thrust ventilation allows the construction of enclosed car parks that have an open, clean and safe environment without compartments or dividing walls.
The exhaust air is extracted using the main exhaust extract fans. The air flow is determined by the current regulations for car park ventilation systems BS — and Approved Documents B and F. In the case of fire, visibility of at least 30 metres should be provided minutes after the fire has started and this is often examined and proved by the use of a CFD model at the design stage.
Should this not be practical, supply air will need to be introduced mechanically. Thrust ventilators use this natural property of propulsion to accelerate the maximum mass of air and this is the force we measure in terms of Newtons, with fans that are multi-speed and supplied in either 50 Newton or Newton versions. Greater volume of air It is worth noting that ultimately the total amount of air that can be moved will be a multiple of the actual air passing through the fan.
This is the induced power and it varies dramatically with the type of fan. Induction fans, depending on design, induce up to 19 times the volume of air passing through the fan. With the older impulse fans this multiple is at best only 8 times.
The location of the thrust fans in the car park is extremely important for the overall efficiency of the system. With many older systems efficiency was influenced by the Coanda or skin friction effect, the entry and exit conditions of the fan and the difficulty of positioning the fans above parked vehicles because of their physical size.
In practice fans were often fixed against the soffit near to down stand beams or at worst at the junction of the wall and soffit. This meant there was always a Coanda effect at varying levels.
Because of the Coanda effect, the theoretical thrust was rarely if ever available in the installed mode. Also, an operational car park would have many vehicles parked that would inevitably hinder the flow pattern. As a result performance between test and actual could be drastically different. Discharge pattern The discharge pattern of the modern induction fan virtually removes any concern about loss of performance due to the Coanda effect. The fans are ultra slim in design, which means that they can be fixed directly above the driving lane where their volumetric efficiency will have the maximum effect.
This is one of the big advantages of the induction fan over the impulse fan. Upon detection a signal is sent to a PLC within the main control panel. This is the heart of the parking ventilation system.
In the case of fire, the thrust fans can create a virtual smoke corridor, enabling the removal of large volumes of smoke and heat.
Demand driven Basement parking ventilation using induction thrust fans is demand driven, air flow through a car park continually fluctuates in line with the local environmental conditions, therefore there will be less aerodynamic loss and lower energy demand. Should there be a change in air quality or should smoke be present, the detection system will record this and the PLC will react accordingly.
Depending on the location and status of any change in air conditions, the PLC will activate the ventilation system in accordance with the programmed functionality diagram. Possible operation conditions 1 Continuous low rate ventilation or time delayed daily ventilation.
BS 7346 Part 8 standard for smoke ventilation systems is a crucial life saving requirement
BS Part 8 standard for smoke ventilation systems is a crucial life saving requirement 15 Aug However, while Building Regulations Approved Document B, The Machinery Directive and The Construction Product Regulations, via the various parts of EN , provide a relatively tight regulatory framework, until the BS Code of Practice, no single document existed that provided guidance for the industry from initial design, through installation to maintenance. The over arching benefit of this new document is that by adhering to its guidelines designers, installers, commissioning engineers and maintenance teams can create, install and operate a fully compliant smoke control system. Throughout BS , there are some constant themes that are present. Not only does it deal with product quality, location, performance and operation, but also the key questions of assessment of needs together with the certification and verification by authorised bodies. Developing the standard The Smoke Control Association SCA , of which SE Controls is a long-standing corporate member and has been present on the British Standards committee for more than 15 years, recognised that there was a need to raise the standards across the industry. A key driver in the early stages of the process was evidence suggesting that smoke control systems in residential high-rise developments were of variable quality, an issue created by a number of factors. For example, although there are several inter-related product standards governing individual components within smoke control solutions, nothing existed that encompassed the entire system.
There are broadly two methods of complying with the Building Regulations regarding ventilation and these are natural or mechanical ventilation. Whichever method is used, the required results are defined as: Why ventilate? Also, radiation depends on the concentration and composition of smoke. This has led to a review of the heat output from burning cars and the risk of fire spread between cars.