Building Services Engineering Research and Technology current issue

Formaldehyde exposure risk in air-conditioned offices of Hong Kong

Mui, K., Wong, L., Hui, P., Chan, W. — Mon, 16 Nov 2009 02:51:28 PST

Formaldehyde (HCHO) is a carcinogenic toxicant commonly present in an air-conditioned office environment. This study examines the lifetime exposure risk of HCHO in air-conditioned offices of Hong Kong under various indoor environmental conditions. Using the regional indoor air quality assessment results of 511 Hong Kong offices recorded from 1996 to 2005, together with the mathematical correlations among HCHO exposure concentration, ventilation and thermal environment verified at 43 other local air-conditioned offices, the exposure risk in terms of loss of life expectancy (USEPA standard) was predicted for an office environment preset at certain air temperature and atmospheric carbon dioxide (CO₂) level. It was reported that the average increment of HCHO exposure risk was 2% for every 1°C increment in the air temperature range of 22.5—25.5°C, or 2.5% for every 10 ppm increment in the CO₂ concentration range of 800—1000 ppm. This study presents useful information on HCHO exposure risk evaluation for air-conditioned offices associated with various policies on indoor air temperature and ventilation demands.

Practical applications: This study outlines an approach to lifetime exposure risk assessment for HCHO inhaled in air-conditioned offices of Hong Kong under various indoor environmental conditions. In a typical office environment, the findings demonstrated that the average increment of HCHO exposure risk was 2% for every 1°C increment in air temperature or 2.5% for every 10 ppm increment in CO₂ concentration.

Fuzzy multi-criteria evaluation model of HVAC schemes in optimal combination weighting method

Wang, J., Jing, Y., Zhang, C. — Mon, 16 Nov 2009 02:51:28 PST

Six heating, ventilation and air conditioning (HVAC) schemes, constant air volume, variable air volume, fan-coil, induction unit, variable refrigerant volume and distributed HVAC system are evaluated and compared in multi-criteria. Because of the uncertainty of qualitative criteria, this paper presents a fuzzy multi-criteria model to select the optimal HVAC system. The methods of fuzzy set theory, linguistic value, analytic hierarchy process, entropy weighting and optimal weighting are used to obtain the criteria weights. Fuzzy technique for order preference by similarity to ideal solution (TOPSIS) method is employed to get the ranking of HVAC schemes. Finally, the application of the fuzzy multi-criteria evaluation model demonstrates detailedly the computation and evaluation procedure in the selection of HVAC schemes.

Practical applications: The fuzzy multi-criteria evaluation model combined with the optimal weighting method in this paper is believed by the authors to contribute to the selection and comparison of HVAC systems or schemes in the building. It is proposed that both qualitative and quantitative criteria existing in reality are used to evaluate HVAC schemes and the decision-making method combines both subjectivity and objectivity. In addition, simple and practical computation and evaluation procedure is easily applied by HVAC designers or decision-makers. Such an approach could become a powerful tool to make an optimal selection for HVAC schemes.

Modelling sanitary demands for occupant loads in shopping centres of Hong Kong

Mui, K., Wong, L., Lam, H. — Mon, 16 Nov 2009 02:51:28 PST

This paper presents a quantitative mathematical model of sanitary demands from occupants in shopping complexes. In-situ measurements and interview surveys with occupants were conducted in typical local shopping malls in order to determine the model parameters for their visiting patterns, load patterns, demand patterns and their preferred or acceptable duration for waiting and using water closets (WCs). The model is used to assess the probable acceptance of sanitary facilities towards the acceptable amount of time for waiting at a typical female washroom designed for an occupant load of 600 occupants in a shopping mall. The results showed that the current sanitary provisions for female washrooms in local shopping malls could meet occupants’ minimum expectation, while with an additional 33% of WC, the sanitary would fully satisfy ‘all’ occupants in terms of amount of time for waiting.

Practical applications: This paper presents a quantitative mathematical model of sanitary demands from a group of building occupants. This model is applied to evaluate the performance of sanitary provisions at typical female washrooms in Hong Kong shopping malls and to quantify the provisions required to achieve the most acceptable amount of time for waiting to their users.

Normalised spectrum for flow-generated noise prediction using computational fluid dynamics

Mak, C., Au, K. — Mon, 16 Nov 2009 02:51:28 PST

Flow-generated noise from in-duct strip spoilers was radiated from an open exhaust termination unit into a 70 m³ reverberation chamber and have been measured in 1/3 octave bands using sound power spectra. Computational fluid dynamics (CFD) software package was adopted to model the strip spoilers in the air duct. Based on the results of CFD simulation of relevant configurations, the technique of Mak and Au and Mak and Oldham was adopted to normalise the experimental data. A normalised spectrum has been produced for predicting the sound power level of flow-noise produced by the strip spoilers in a rectangular air duct. The data collapse for the strip spoilers is generally good at higher Strouhal numbers, but is less efficient at lower Strouhal numbers where considerable scatter is observed. Together with the normalised spectrum, the predictive equations of Mak and his co-investigators can be used to predict the flow-generated noise produced by in-duct strip spoilers in a ventilation system at design stage using CFD.

Practical application: Together with the normalised spectrum, the predictive equations of Mak and his co-investigators can be used to predict the flow-generated noise produced by in-duct strip spoilers in a ventilation system at design stage using CFD.

Thermal behaviour model identification for an office space using BMS data

Mustafaraj, G., Chen, J., Lowry, G. — Mon, 16 Nov 2009 02:51:28 PST

In this study, linear Box—Jenkins, output-error and non-linear neural network autoregressive NARX models are investigated to predict the thermal behaviour of an office positioned in a modern commercial building. External and internal climate data recorded over a summer season were used to build and validate models. The paper exploits the potential of using linear and non-linear models to predict room temperature at different time scale ahead (5 min or 4 h ahead). The prediction performance is evaluated using the criteria of goodness of fit, errors and mean-squared error between predicted model output and real measurements. The results demonstrate that all models provide reasonably good predictions but non-linear models outperform linear models.

Practical application: Prediction of room temperature by black-box linear and non-linear models obtained can be utilised in the building temperature control strategy. When there is any change in the building thermal behaviour (e.g. more equipments added or office equipment re-arranged), the performance of traditional non-adaptive building temperature proportional—integral (PI) or proportional—integral—derivative (PID) controls will deteriorate. The models based on immediate past records and actual behaviour can be adapted to any changed. The PI and PID controller with such models integrated are adaptable to any changes and hence maintain performance. The modelling techniques studied in here are not restricted to office building temperature prediction and control problems; they can be extended to other types of buildings such as hospitals, supermarkets, airports and schools.

An urban drought-prevention model using raft foundation and urban reservoir

Cheng, C., Liu, Y., Ting, C. — Mon, 16 Nov 2009 02:51:28 PST

The main purpose of this research is to develop a practical operation model for water conservation, in responding to the challenges of climate change, to propose a solution for urban drought period. This paper presents an urban drought-prevention model with allocation to prevent-drought using abundant idle raft foundation of existing buildings and the information of urban reservoir implemented by linear programming. The proposed model is developed to provide substantial demand for residential water utilisation during a period of urban drought. This operation model is of adaptable system underpinned by sustainable water management principles. The simulation and validation assumed that the water used is the rainwater and just to flush the toilets. According to the results of this research, the proposed model has been proven to be practicable and feasible for urban drought-prevention solution.

Practical implications: This research illustrates the important contribution of abundant idle capacity in existing building raft foundations. This paper also shows the sustainable water management technologies and the solution for the designer, which has the opportunity to implement and adapt to the best benefit for water conservation and sustainability.

Improvements to the Meteorological Office equations in the computation of degree days

Layberry, R. — Mon, 16 Nov 2009 02:51:28 PST

Meteorological Office (MO) equations are used to calculate daily degree days from daily minimum and maximum air temperatures. The resultant degree days are widely used in building energy analysis for monitoring, targeting, prediction and exception reporting and their accuracy is consequently important. Regression analysis has been performed on minimum, maximum and average daily air temperatures and daily degree days from over 100 weather stations over a 20-year time period. The results show how the MO equations consistently overestimate the degree days. This overestimation becomes progressively severe as the air temperature increases relative to the base temperature used in the degree day calculation. The use of optimised equations containing the maximum, minimum and average temperatures in a day most accurately calculates degree days and where the daily average is not available, using the daily minimum and maximum with different coefficients to those used in the MO equations leads to a significant improvement in the calculated degree days. Practical applications: Degree day data is vital in building energy management. Often hourly temperatures are not available and degree days have to be calculated from the MO equations using daily minimum and maximum temperatures. These equations are approximations developed from limited datasets and this paper describes better equations using minimum and maximum data and further improved equations when average daily data is also available. The reductions in errors in either degree days or energy use is important for reducing errors in data extracted from the resultant performance charts.

Thanks to Reviewers

Mon, 16 Nov 2009 02:51:28 PST

Erratum

Mon, 16 Nov 2009 02:51:28 PST

The articles listed below were first published online ahead of print with incorrect DOIs. The articles have subsequently been published in journal issues with correct DOIs. The articles have now been removed from the Online First listing. SAGE apologises for any inconvenience the error may have caused.

M. Davies and Z. Ye. A ‘pad’ sensor for measuring the moisture content of building materials. Building Services Engineering Research and Technology, first published on July 16, 2009 as 10.1177/0143624409339964. This version is no longer available. The version of record is published in Vol 30 No 3 as 10.1177/0143624408339964

Erratum

Mon, 16 Nov 2009 02:51:28 PST

M. Ning and M. Zaheeruddin. Fuzzy set-based uncertainty analysis of HVAC&R systems: a simulation study. Building Services Engineering Research and Technology, first published on July 16, 2009 as 10.1177/0143624409338321. This version is no longer available. The version of record is published in Vol 30 No 3 as 10.1177/0143624408338321

Erratum

Mon, 16 Nov 2009 02:51:28 PST

A. Baranowski and J. Ferdyn-Grygierek. Heat demand and air exchange in a multifamily building simulation with elements of validation. Building Services Engineering Research and Technology, first published on July 16, 2009 as 10.1177/0143624409338139. This version is no longer available. The version of record is published in Vol 30 No 3 as 10.1177/0143624408338139