Building Services Engineering Research & Technology

This study evaluates the thermal performance of geothermal borehole heat exchangers (BHEs) in various Canadian locations during winter, focusing on soil freezing effects. Using a computational fluid dynamics approach, it examines how soil porosity and thermal conductivity influence BHEs’ thermal performance. Ninety case studies across nine Canadian zones assessed these effects under winter conditions. The RNG k-ɛ turbulent model tracked fluid flow, and the solidification model monitored ice formation. Soil temperature fluctuations along the ground depth were incorporated using user-defined function codes. Coefficients of performance (COP) were calculated for heat pump thermal performance. Results showed substantial soil freezing around the borehole in Saskatchewan and Manitoba. The BHE systems in Alberta and Manitoba had the highest thermal resistance, while those in Saskatchewan and Prince Edward Island had the lowest. Increasing soil porosity from 0.4 to 0.55 and decreasing thermal conductivity from 2.0 to 1.385 W/mK led to up to 40% and 58% increases in ice formation, respectively. The COP of the heat pump in British Columbia was maximized, reflecting the peak temperature of the outlet fluid from the BHE. By incorporating site-specific climatic data and addressing gaps in existing standards, this research enhances geothermal system guidelines with practical design recommendations.

This study investigates the combined effect of humidity control and simulated natural airflow on human thermal comfort in indoor thermal environments. A custom-built device was developed to simulate natural wind while controlling spray volume under varying ambient temperatures (27°C–30°C) and relative humidity levels (40–60%). 12 participants were subjected to 24 experimental conditions, and their thermal comfort and airflow preferences were evaluated using structured questionnaires. The results indicated that when the temperature exceeded 28°C and humidity reached 60%, increasing airflow had a more significant impact on comfort than adjusting spray volume. Conversely, at temperatures below 28°C, adjusting spray volume significantly enhanced comfort. These findings provide insights into optimizing indoor climate control systems, offering practical applications for reducing energy consumption while maintaining occupant comfort.

Oily fine particles (PM2.5) are considered important pollutants in the industrial environment, and long-term exposure to such oil mist pollutants can bring serious harm to the health of production personnel and the quality of processed products. Acoustic agglomeration is a mechanism of particle agglomeration in which the acoustic wave enhances the entrainment effect of the flow field on fine particles, promotes the collision polymerisation of fine particles and then reduces the suspended concentration of fine particles in the factory environment. However, the existing theory of acoustic agglomeration does not consider the effect of the cohesive force of adjacent oily fine particles on entrainment motion. In this paper, an entrainment model of oily fine particles is established, and a gas wave model of standing wave acoustic field is used to deduce the entrainment coefficient of the sound wave’s ability to carry oily fine particles. The results reveal that the less dense oily fine particles are more easily carried by sound waves. There is a frequency range where the entrainment coefficient changes most significantly.

This paper investigates air leakage rates between the common corridor and the lift shaft within modern high-rise residential buildings via the lift doors. A literature review has been undertaken which indicates that leakage areas for lift doors are suggested as being between 0.047 and 0.060 m² with only the latest version of BS EN 12101-13:2022 indicating that a reduction may be necessary to 0.020 m² for more modern buildings. Leakage areas have been investigated for a 22 storey residential building by recording on-site flowrate and pressure measurements whilst a lift car is in operation as well as attempting to measure the gaps across a set of lift doors. The maximum instantaneous flowrate measured was −89 L/s into the shaft and +99 L/s out of the shaft. The largest pressure change recorded was a depressurisation of −22.5 Pa and the highest pressure recorded was +19.5 Pa. These values result in a maximum calculated leakage area of 0.020 m² for this building. This value is approximately half of the lift leakage area previously quoted in BS EN 12101-6:2005, however is closer to the suggested tight lift door value of 0.020 m² in BS EN 12101-13:2020 and would indicate that these are more appropriate for use in analyses of modern buildings.

This study examines the performance of a new oscillating air-conditioning dehumidification system, designed to overcome the limitations of traditional methods, such as energy-intensive defrost cycles and inconsistent dehumidification in high-humidity conditions. Experimental tests demonstrate that the system achieves a dew point as low as −9.38°C with specific humidity reaching to 1.67 g/kg and coefficient of performance (COP) ranging from 3.3 to 4.7. Apart from testing, numerical modelling of the system has been built in TRNSYS and validated using experimental data. A validated TRNSYS model was used to extend the analysis across various climate zones, revealing that the system performs optimally in high-humidity regions like Hong Kong and Chongqing, with an annual average COP of 3.89 in Hong Kong. In contrast, colder and drier regions like Urumqi maintained lower but stable energy efficiency, with an annual average COP of 2.30. These findings suggest that the oscillating air-conditioning dehumidification system offers versatile, climate-adaptable operation with potential applications in diverse building types.

Swimming pools are critical public health infrastructure that provide benefits to diverse user groups. However, they are also energy-intensive and expensive to operate. Therefore, national policies regarding swimming pool circulation requirements need to balance these factors to ensure multi-dimensional sustainability. We develop a methodology to gather quantitative information to support industry-wide policy recommendations. We use openly-available data from 6433 non-domestic swimming pools in England to estimate national-scale energy use, cost and carbon footprint associated with swimming pool circulation. Our results show that total annual energy use for pool water circulation, assumed to be operating within national guidelines, is 369,000 MWh at a cost of £100M. A further 109,000 MWh (£6.33M) is associated with filter backwashing processes. The combined annual carbon footprint from energy and water use is 98,400 tCO₂e. We investigate three industry-recognised interventions to reduce energy use in pool water circulation, which would not typically compromise water quality or safety, and demonstrate these could reduce costs by up to 70%. Differences between national guidelines on pool circulation also suggest overly cautious requirements for certain pool types. The results demonstrate the substantial impact changes to policy guidelines could have on the financial and environmental sustainability of non-domestic swimming pools.

Heat pumps are considered a key technology for the decarbonisation of space and water heating in domestic dwellings in the UK. Heat pumps that employ high-temperature working fluids such as CO₂ have the potential to be used in retrofit applications. This paper presents the characteristics of a CO₂ heat pump developed at Brunel University of London and the simulation results of its application to provide space and domestic hot water heating in a well-insulated four-bedroom semi-detached house with four occupants. The heating system is assumed to employ water thermal energy storage. Analysis has shown that storage volumes between 200 L and 300 L can satisfy the space temperature control requirements of the domestic dwelling if a heat pump capacity of 4.5 kW at 7°C ambient temperature and 60°C water flow temperature is employed. A comparison of the heat pump with a gas boiler reveals that with current gas and electricity prices, running costs for the heat pump can be 91% higher and CO₂ emissions 40% lower than those of the gas boiler. Further design and control optimisation of the heat pump is expected to reduce both its running costs and CO₂ emissions.

Despite the known effects of UHI on building energy consumption, there is currently a lack of generalizable methods to incorporate UHI into building energy simulations (BES) for accurate energy performance evaluation of urban buildings. The absence of generalizable methods is mainly due to the complex and interconnected relationships among the urban built environment, UHI and building energy performance which not only determine the magnitude of UHI intensity, but also its effects on the energy performance of buildings. With the overarching aim of enabling a generalizable UHI-BES integration method, this literature review examines the relationships between urban morphology, UHI and building energy consumption to determine the knowledge gaps that hinder the development of a robust and generalizable integration method. More specifically, this literature review presents a critical analysis of methods and data sources used in the existing literature to (1) derive UHI intensity based on urban built environment attributes, and (2) analyze the effect of calculated UHI intensities on the cooling, heating, and annual energy consumption of buildings. Methods and materials used by various studies are examined given their potentials for generalizability, level of accuracy and application possibility for BES purposes.