Building Services Engineering Research & Technology

Articles on the state of the art of developments in building services engineering Welcome to the 'Blue Pages'. This is where guest editors from the Editorial Advisory Panel for Building Services Engineering Research and Technology address current developments in building services engineering practice and research. The articles are very short, on one theme of current interest, and do not go through the longer refereeing process for conventional research papers. This is to encourage consultants and contractors to discuss their latest developments in a non-commercial manner. Academics will also be asked to outline current research areas in universities and colleges. Without the constraint of full refereeing there is scope in the articles to provoke interest and to raise issues for discussion. Consequently the Editor of BSER&T is happy to receive and publish letters furthering the discussion of 'Blue Pages' articles. If you have a suggestion for an article or topic you would like to see included in the 'Blue Pages' please inform the Editor, Barry Copping. Comments on the 'Blue Pages' are also welcome. 'Blue Pages' will only succeed if readers of the journal wish the feature to succeed and contribute to its success.

The aim of this study is to assess the performance of the mechanical ventilation system and air quality in an office building. The perfluorocarbon tracer (PFT) technique was used to measure air flow in an air handling unit and to estimate flow rates supplied to the office. In order to validate the PFT technique as a viable means of measuring air flow in the mechanical ventilation system, the PFT measurements were compared with measurements made using a pitot-static tube. Air exchange range, ventilation effectiveness and age of air were examined. The concentrations of carbon dioxide (CO₂), carbon monoxide (CO), formaldehyde (HCHO) and dust particles were monitored. In addition, a questionnaire was completed by the staff in order to provide a subjective assessment of indoor air quality.

An analysis is presented concerning the relative proportion betwen the sums of rated capacities of on-off controlled and modulating controlled terminal units in differential-pressure-bypass type chilled water distribution systems. In these systems, there is the chance that differential temperature across the supply and return mains at system part-load conditions could be lower than the system design value. The ratio of the sum of rated capacities of on-off controlled terminal units to the sum of the rated capacities of all terminal units should be smaller than the smallest value of the ratios of the pressure difference across the mains at the distribution end (when all the connected terminal units are receiving their rated water flows) to the constant supply differential pressure for all distribution circuits. This excludes units designed for precooling intake outdoor air to or above the design room air temperature.

A criterion and procedure for balancing differential-pressure-bypass chilled/heating water systems is described. Theoretical analysis has been carried out which suggests that the proposed criterion is feasible. The drawback is that slight oversizing of coils is required. Advantages are simplification in balancing procedure, and achieving a higher operating differential temperature across the mains than the system design value which would allow chillers/boilers to operate to their design thermal output.

Rapid advances in adaptive signal processing are making active noise control products a practicable proposition. One unit available in the industry was chosen in this study to evaluate its application and effectiveness in controlling noise in ventilation systems. Its performance with aerodynamic and static noises was evaluated against the conventional duct lining approach. Experimental results indicate that the system is applicable in air-conditioning systems despite the existence of some constraints that have to be taken care of. It is proposed to use the equipment to supplement the traditional dissipative silencer for noise level control and for the achievement of spectrum balance.

Many premises have been equipped with building and energy management systems in recent years. Users are now becoming very familiar with their use, and this paper presents and discusses feedback of their perceptions. Particular issues emerging are the increasing expectations for systems communications and the scope for improvements in system usability. Also, users are evidently not giving high priority to energy saving and, consequently, this potential is not being fully exploited.

The objective of the research described in this paper is to improve the speech intelligibilty of multiple loudspeaker public address systems in long and flat enclosures, such as underground stations and supermarkets. It was theoretically demonstrated that strong directional loudspeakers are effective for increasing the speech transmission index (STI), and thus, a series of experiments were carried out to increase the loudspeaker directionality by an architectural method. It was found that a significant increase can be obtained by putting the loudspeaker inside a box, both with and without absorbers on the inner surfaces. The corresponding frequency spectrum change is very small and acceptable.

This paper presents mathematical formulae for analysis of passenger traffic using double decker lifts. The formulae are general allowing any possible traffic flow to be considered. A Poisson approximation of passenger arrivals at lift landing stations is assumed allowing probable number of stops and average lowest and highest reversal floors to be calculated. Conventional techniques can then be used to calculate round trip time, interval and capacity factor. The calculations are iterative and require computer implementation.

A previous paper by the author showed that the selection of inappropriate combinations of wall and window designs by the 'passive solar' designer could lead to a seasonal auxiliary energy penalty instead of the expected advantage. A simple method was proposed whereby a designer could calculate a 'critical house temperature difference' which would enable the average efficacy of different combinations of window and wll designs for different orientations to be evaluated over a heating season and so reduce the risk of incurring an energy penalty. The proposed method has now been tested using DEMON, a program derived from BREDEM 8, and shown to be effective for the cases used. This paper describes the testing of the proposed calculation method.

Thermal resistance, noise reduction, daylight and solar energy admittance are some of the expected duties of a window. A window manufacturer or a building services engineer employed to select windows for optimum performance does not necessarily need to know the intricate details of the thermal, sound, daylight and solar transmission characteristics of multiple glazed windows. Rather, they require broadly based information on critical design parameters and their influence on window performance. This paper presens charts which enable appropriate design of windows for any given duty and set of constraints.

The CIBSE Building Energy Code was first published in 1981 but has not been widely used among architects, civil engineers or building services engineers. A full calculation will require about 60 separate data inputs with some 80 calculation steps; perceived complexity and opacity perhaps inevitably lead to reduction in confidence. It is however, an ideal candidate to transferring to spreadsheet format. This paper presents work developed from an educational programme which allows simplified use of an otherwise complex and time-consuming procedure. It also allows the building thermal demand targets to be calculated from first principles.