Energy and Built Environment最新文献

Shell and tube heat exchangers (STHE) are essential thermal equipment and widely used in daily life. A novel thermosyphon system called falling-film thermosyphon (FFTS) is introduced and integrated into STHE system, resulting in a better thermal performance. In this study, a rectangular solid tube bank of FFTS bundles with a baffle design is studied. The numerical simulation for heat and mass transfer of the FFTS heat exchanger is developed to predict the condensation rate of the vapor in the flue gas, and a lab-scale prototype is also built up in COMSOL. The prediction is validated with the experimental data from references, and the model's accuracy is verified within 10%-12% error. Also, the Non-dominated Sorting Genetic Algorithm, version 2 (NSGA-II) is implemented to improve the thermal performance of rectangular tube banks in this paper. Several parameters, e.g., baffle number, tube number, and tube space, are optimized. As a result, compact configurations with more baffles are preferred to enhance the performance associated with a high-pressure drop correspondingly. The optimized layout for the lab-scale prototype can increase by 18 to 32% condensation with a pressure loss of less than 200 Pa.

Daylight is one of the essential criteria for decent housing. However, in an urban kampung, access to daylight is limited due to the high-density population in urban Kampung Kota. This study aims to improve the visual and thermal conditions by modifying the aperture of the light pipe based on visual daylight distribution, illuminance level, and thermal conditions in multi-storey houses in hot-humid climates. Light pipe was developed experimentally through the simulation model to investigate the performance and impact on the visual and thermal conditions like operational temperature and RH in densely populated Kampung Kota without vertical apertures. According to the results, the two-aperture light pipe residential space enhanced the current situation but did not fulfill the standards. The two aperture light pipe visually improved daylight distribution by 1.05% –31.36% and illumination level by 8.4% - 14.8%. We also found that light pipe also impacts thermal conditions with a 10.92% RH reduction while at the same time increasing temperature up to 10.57%. Therefore, it can be concluded that a two-aperture light pipe has the potential to be applied to actual conditions in hot-humid climates.

The assessment of the thermal energy performance of earth-based buildings with respect to the semi-arid Mediterranean climate of Morocco is scarce, even if the country is historically known for its earthen dwellings. According to this need, this work aims to understand and evaluate the indoor thermal comfort and energy performances of passive building in two different locations. We have used EnergyPlus modeling tool and in addition, the monitored ten-day indoor temperatures in two different thermal zones in the test prototype to justify the empirical validation of Building Energy Model. The findings demonstrate, the use of compressed earth blocks coupled with passive design strategies provides better comfort and great sustainability. Thus, the summer discomfort hours are reduced about 12% for both cities compared to conventional building. However, the combination of semi-arid climate-responsive passive design has allowed to reach a thermal energy intensity reduction difference from 20 to 65 kWh.m⁻². y⁻¹.

Thermoacoustic heat pumps are a promising heating technology that utilizes medium/low-grade heat to reduce reliance on electricity. This study proposes a single direct-coupled configuration for a thermoacoustic heat pump, aimed at minimizing system complexity and making it suitable for domestic applications. Numerical investigations were conducted under typical household heating conditions, including performance analysis, exergy loss evaluation, and axial distribution of key parameters. Results show that the proposed thermoacoustic heat pump achieves a heating capacity of 5.7 kW and a coefficient of performance of 1.4, with a heating temperature of 300 °C and a heat-sink temperature of 55 °C. A comparison with existing absorption heat pumps reveals favorable adaptability for large temperature lift applications. A case study conducted in Finland over an annual cycle analyzes the economic and environmental performance of the system, identifying two distinct modes based on the driving heat source: medium temperature (≥250 °C) and low temperature (<250 °C), both of which exhibit favorable heating performance. When the thermoacoustic heat pump is driven by waste heat, energy savings of 20.1 MWh/year, emission reductions of 4143 kgCO₂/year, and total environmental cost savings of 1629 €/year are obtained. These results demonstrate the potential of the proposed thermoacoustic heat pump as a cost-effective and environmentally friendly option for domestic building heating using medium/low-grade heat sources.

Advanced data mining methods have shown a promising capacity in building energy management. However, in the past decade, such methods are rarely applied in practice, since they highly rely on users to customize solutions according to the characteristics of target building energy systems. Hence, the major barrier is that the practical applications of such methods remain laborious. It is necessary to enable computers to have the human-like ability to solve data mining tasks. Generative pre-trained transformers (GPT) might be capable of addressing this issue, as some GPT models such as GPT-3.5 and GPT-4 have shown powerful abilities on interaction with humans, code generation, and inference with common sense and domain knowledge. This study explores the potential of the most advanced GPT model (GPT-4) in three data mining scenarios of building energy management, i.e., energy load prediction, fault diagnosis, and anomaly detection. A performance evaluation framework is proposed to verify the capabilities of GPT-4 on generating energy load prediction codes, diagnosing device faults, and detecting abnormal system operation patterns. It is demonstrated that GPT-4 can automatically solve most of the data mining tasks in this domain, which overcomes the barrier of practical applications of data mining methods in this domain. In the exploration of GPT-4, its advantages and limitations are also discussed comprehensively for revealing future research directions in this domain.

The thermal performance of a “U” type earth-to-air heat exchanger is presented in this experimental study. The device has a serial-connected vertical configuration. The wells where tubes were installed have a depth of fewer than 3 m and are separated every 1.5 m, using an installation area of 3m². The experimentation was carried out in March in Morelos, Mexico when the environmental temperature reaches 35 °C during the day. The performance of the device was measured and compared to the requirements of an office for cooling purposes within a university campus to reproduce the space restrictions found in urbanized areas. By using a small land surface, it is feasible for urbanized areas. The air temperature inside the “U” type earth-to-air heat exchanger, the surrounding soil temperature, the airspeed, and the power consumed by the fan were measured. The air temperature and the fan's power consumption data were obtained by modifying the airspeed in four constant values, from 1.3 m/s to 6.6 m/s. Results show that the device evaluated in this work has adequate thermal performance for cooling purposes compared to the requirements of an office. A decrease in air temperature was recorded in a range of 5.1 °C to 9.4 °C. Over 70% of the total temperature difference was reached in the first well, where the average soil thermal disturbance at 5 cm was 2.8 °C. The device achieved a maximum COP of 12.8 and a maximum effectiveness of 88.4%. With these results, it is concluded that the system is suitable for cooling purposes in areas with space restrictions. This work is novel since the dimensions available for installation in urbanized areas are considered and compared with the thermal requirements of an office. In addition to the fact that there are no published works with vertical heat exchangers connected in series.

International Energy Agency (IEA) predicts India's AC stock will reach 1144 million units by 2050, making it the second largest ACs holder globally. Studies on the effect of building geometry on cooling load reduction are primarily focused on material and envelope specifications. However, studies on building morphological parameters in the Indian context are scarce. Therefore, this research quantifies the effect of four morphology predictors, namely, FL (floor number), ESA (exposed surface area), CZB (conditioned zones per building), and CZF (conditioned zones per floor) on cooling load in 75 dominant residential built forms of Navi Mumbai. The selected buildings are simulated using the Rhinoceros 6 tool with the energy plus plugin. Despite having the same simulation inputs, envelope parameters, and conditioned volume, the results indicated a 90 % variation between the compact and loosely designed forms. Multiple Linear Regression shows that the four predictors explain 78% (R² = 0.78) of variation in the cooling load. It is observed that tall buildings show greater efficiency in cooling load reduction due to lesser CZF values. Also, an increase in CZB and a decrease in ESA significantly reduce the mean cooling load due to compactness and wall sharing, respectively.

Rational urban design helps to build sustainable cities with high ventilation capacity and pollutant removal capacity, but the effect of building height on ventilation and pollutant dispersion inside asymmetric canyons has not been fully studied. In this paper, we studied the effect of increasing the degree of building height asymmetry (DBHA) on canyon ventilation and pollutant diffusion in shallow and deep asymmetric street canyons by considering six different building height ratios (BHR = 3/4, 1/2, 1/3, 4/3, 2/1 and 3/1). The results show that increasing the DBHA in asymmetric canyons can improve the ventilation and pollutant removal capacity. For step-up canyons, increasing the downwind building height is very useful to improve ventilation and pollutant removal. For shallow/deep step-up canyons with BHR = 1/3, the air exchange rate (ACH) increased to 211.2% and 380.1% of the flat canyons, respectively. The spatially-average pollutant concentration in the pedestrian zones (leeward K_avg* ang windward K_avg*) decreases significantly with the increase of DBHA, especially for the deep step-up canyon with BHR = 1/3, the leeward K_avg* and windward K_avg* decrease to 15.3% and 3%, respectively. Also, increasing the upwind building height can also improve the ventilation capacity in the step-down canyons. For the deep step-down canyon with BHR = 3/1, the leeward K_avg* and windward K_avg* decreased to 40.6% and 24.1% of the deep flat canyon, respectively. Notably, the ventilation capacity is very low for step-down canyons with BHR = 4/3, and for step-down canyons with BHR ≥ 2/1, the ventilation capacity and pollutant removal capacity increase significantly with the increase of DBHA. Therefore, in urban planning, step-down canyons with BHR = 4/3 should be avoided and designed to satisfy the condition of BHR ≥ 2/1. These findings will be a valuable reference for urban designers to build sustainable cities with high ventilation capacity.

Frosting is a common phenomenon of the ASHP under the heating mode in winter, and the outdoor air flow rate flowing through the evaporator of the ASHP was always thought to be a major contributor. In order to validate its contribution, effects of outdoor fan airflow rate on the performance of air source heat pumps (ASHPs) were investigated under the winter heating condition. The experiment was conducted in a laboratory at the standard 2 °C air dry bulb temperature (DB)/ 1 °C air wet bulb temperature (WB) frosting condition, which enabled the analysis of the operating performance, frosting performance, and heating performance of the ASHP unit by changing the airflow rate of the outdoor fan. Results showed that as the airflow rate of the outdoor fan reduced from 100% to 36%, the operating performance decline and the elevated frosting-defrosting loss were observed. Meanwhile, both the frosting rate and the operating efficiency during frosting-defrosting cycles showed an increasing trend then followed by decreasing tendency. The maximum frosting rate and operating efficiency were 0.92 g/m².min and 2.92, respectively, which were observed at 74% airflow rate of the outdoor fan of the ASHP unit. The observation implied the existence of the “minimum frosting suppression airflow rate”. At 36% airflow rate of the outdoor fan of the ASHP unit, however, the performance of the ASHP unit was attenuated greatly, with the frosting-defrosting efficiency loss coefficient of 0.47, the heating capacity and COP reduction by 51.5 and 38.8%, respectively. These findings provided significant references to the optimization of ASHPs performance with variable airflow rate of the outdoor fan under frosting conditions.

Local agro-industrial wastes-based particleboards and fiberboards in Egypt are manufactured mainly from sugarcane-bagasse and flax shives. These panels are used in decorations and interior claddings. This paper aimed to broaden their market to be utilized in local low-cost and simple building envelope retrofitting packages instead of conventional packages that depend on imported expanded polystyrene and wet-rendered gypsum boards. Thermal conductivities of various existing sugarcane-bagasse and flax-shives-based panels were measured to be used in developing multilayered interior claddings with adequate thermal insulating performance to increase the thermal mass of a validated non-insulated case-study residential building as recommended by the Egyptian Code for Energy Efficiency of Residential Buildings. Models retrofitted using the developed cladding assemblies were simulated using Design Builder to determine their achieved annual energy savings and predict their profitability. Thermal conductivities of sugarcane-bagasse and flax-shives-based particleboards were lower than wood-based cladding panels, with the range of 0.05–0.1166 W/mK. Moreover, the thermal conductivities of sugarcane-bagasse fiberboard had the range of 0.0926–01,111 W/mK which is significantly lower than wood-based fiberboards. Simulation results showed that both models retrofitted, sugarcane bagasse-based and flax shives-based, achieved better energy savings, 5.07% and 5.04%, than the conventionally retrofitted model, 3.73%. Furthermore, the flax-shives-based model showed higher profitability, with positive income achieved in the 15th year, than a conventionally retrofitted model, achieved in the 20th year, and the sugarcane-bagasse-based model, achieved in the 19th year. Thus, it was recommended that although flax-shives-based wall claddings were usually 14–20% thicker than sugarcane-bagasse-based claddings, they provided similarly high annual energy savings with lower initial costs and higher profitability.