M.Y. Chan

Field measurement on transient carbon monoxide levels in vehicular tunnels

Abstract Carbon monoxide (CO) and oxides of nitrogen (NOx) produced from internal combustion engines would be accumulated to harmful levels in vehicular tunnels if the design and operation of ventilation system are unsatisfactory. There are 11 vehicular tunnels in Hong Kong with an average of over 650,000 vehicles crossing the tunnels daily. To have a preliminary understanding on the background pollutant levels and identifying the further areas to improve the ventilation provisions, a field study on air quality in those tunnels was carried out. CO levels measured in each tunnel are presented in this paper. Results revealed that the demand control ventilation rates derived from CO and NOx are different. Which one is more important is to be decided by the tunnel management. Air quality was assessed by the temperature difference between the ambient and inside the vehicular tunnels. This is because hot gases emitted would be trapped inside the tunnel due to poor ventilation, and so measurement on the temperature difference would give an indication of air quality. A simple model based on pressure balancing is used to calculate the CO levels for justifying the measured values. The levels of nitrogen dioxide (NO2) were derived from the equation suggested by the Environmental Protection Department (EPD) of the local government. The levels are compared with the internationally recommended standards.

Parameter optimization for operation of a bed-based task/ambient air conditioning (TAC) system to achieve a thermally neutral environment with minimum energy use

The purpose of this paper is to optimize the operating parameters such as: supply air temperature, supply air flow rate and supply air humidity, for a bed-based task/ambient air conditioning (TAC) system installed in an experimental bedroom with two total insulation values of beddings and bed to obtain a thermally neutral sleeping environment with minimum energy use. A computational fluid dynamics (CFD) method was applied to calculate the values of predicted mean vote (PMV) and energy utilization coefficient (EUC) based on conditions of 16 simulation cases. From the simulation results, the design of experiment method was applied to identify operating parameters, individually or combined, that could significantly affect thermal neutrality and energy use for the bedroom environment to establish linear regression models for PMV and EUC. These models were used to obtain the optimum operating parameters of the bed-based TAC system. These models were validated by comparing the obtained optimization results using the models with the predicted results given by the CFD method. The results suggested that for a bed-based TAC system at a specified total insulation value of beddings and bed, a lower energy use can be achieved through adjusting operating parameters while the thermal comfort is maintained.

ENERGY USE FOR VENTILATION SYSTEMS IN UNDERGROUND CAR PARKS

Abstract The use of energy for operating ventilation systems in underground car parks in Hong Kong is considered. A site survey has been carried out in 22 underground car parks. The physical size, configurations, and electrical rating of ventilation fans were the main matters of interest. The indoor thermal environments, carbon monoxide concentrations, and operation of ventilation systems were examined. Mathematical expressions are developed and the predicted results examined for another 54 underground car parks. The results show that significant savings can be achieved if a two-level ventilation strategy is implemented.

IAQ in Large Enclosed Car-Parks in Hong Kong

With the increasing number of vehicles on Hong Kongs roads there is a heavy demand for car parking spaces, especially in commercial areas. Given the shortage of land for development in the territory, multi-storey and under ground car-parks seem to offer the best solution for Government and develop ers alike. However, provision of adequate mechanical ventilation is essential to maintain an acceptable air quality in enclosed and underground car-parks. The overall purpose of a study undertaken by the authors was to develop improved methods for designing car-park ventilation systems. This paper con siders current concerns in Hong Kong on the environment in car-parks, and reports on an ongoing survey of car-park environments, as determined by car bon monoxide concentrations, and on existing ventilation system design and operation. Current design guidelines and ventilation design methodologies used in Hong Kong are reviewed and their suitability for local application is examined. Typical design and operating problems found in car-parks are dis cussed. Case studies of typical underground car-parks in the territory are included.