Outdoor Environment Temperature Research Articles

Energy consumption analysis and operating characteristics research on small time scale of variable refrigerant flow air conditioning systems in public buildings

In order to analyze the energy consumption and operation characteristics of the variable refrigerant flow (VRF) air-conditioning system on small time scale and put forward effective energy-saving suggestions, the VRF system operation experiments are carried out under different indoor set temperatures, different indoor unit opening quantities and different indoor set air velocities. This experiment studies the main influencing factors of energy consumption and operation of the VRF system, such as indoor temperature difference, indoor air velocity, outdoor environment temperature and so on. The results show that the rated power of indoor unit is linearly related to the energy consumption of the VRF system. The total active power changes greatly when the VRF starts and stops, and the outdoor ambient temperature changes. The indoor set air velocities have a great influence on the energy consumption and operation of the VRF system. The performance parameters increase first and then decrease with the increase of compressor frequency and load rate. When the load rate is 40 %∼60 %, the performance parameters can reach 3.2 ∼ 4.2.

Experimental study on comparison of indoor and multiple outdoor thermal environments excluding visual and acoustic interference

To make holistic assessment of the urban environment, it is important to consider both indoor and outdoor thermal environment. Outdoor thermal parameters play key roles in high quality urban life. This study concentrates on differences between indoor and outdoor thermal comfort excluding visual and acoustic interference. An experiment was carried out in indoor climate chamber and three types of outdoor spaces to explore subjective evaluation and physiological parameters of personnel. Subjects can achieve higher thermal comfort and are less sensitive to the change of thermal parameters outdoors. In a wide range of operative temperature and wind speed in outdoor thermal environment, subjects can be more inclined to stay outdoors. With VR glasses on between 27.5 and 33.5 ℃ under direct sunlight, people feel significantly cooler. In this study, VR glasses and noise-cancelling earphones were used in a pioneering way to exclude the influence of visual and auditory factors and comprehensively compare indoor and outdoor thermal comfort. According to the results, outdoor thermal environment can bring more comfort than indoor air conditioning environment, which highlights the importance of improving outdoor thermal environment. The benefits of comfortable outdoor thermal environments compared with indoor neutral environments can be further explored.

Fiber bridging mechanism in moisture‐induced mode I delamination in carbon/epoxy composites: Finite element analysis and experimental investigation

AbstractProlonged exposure of fiber reinforced composite structures to high moisture and temperature in outdoor environment could lead to the degradation of mechanical properties of the materials. To provides reliable prediction of the delamination behavior as the moisture progressively ingresses into the composites, we proposed a Bilinear‐Exponential Traction‐Separation (BETS) law‐which can account for the fiber bridging mechanism‐for investigating the mode I delamination of unidirectional carbon fiber reinforced epoxy composite laminates in wet states. Finite element analysis (FEA) of the delamination model was conducted to evaluate the effects of moisture content on the global force‐displacement curves. A cohesive zone model (CZM) was used to describe the delamination behavior at the interface. With regard to the force‐displacement curves, the BETS law agrees well with results from experimental study (using the double cantilever beam testing on the wet specimens) at both the elastic and failure regions. The delamination model governed by the BETS law also showed good agreement with the crack length versus the crosshead displacement. The FE model that considered the inputs from the BETS law yielded prediction about the evolution of the damage parameter and crack growth profile. In particular, the predicted crack extension increases linearly with increasing crosshead displacement. The proposed BETS law has the advantage of not requiring crack growth monitoring during experiment, and only one fitting parameter was needed to describe the bridging law at different moisture content levels.

Field Measurements and Analysis on Temperature, Relative Humidity, Airflow Rate and Oil Fume Emission Concentration in a Typical Campus Canteen Kitchen in Tianjin, China

This study investigated the annual variation of the indoor thermal environment in a typical canteen kitchen and tried to evaluate the actual working status of the exhaust fume system. Parameters were measured in the canteen kitchen, including indoor environment (temperature, humidity, air velocity); outdoor environment (temperature; humidity); exhaust fume system (temperature, airflow rate, oil fume concentration, energy consumption), and makeup air system (temperature, humidity, air velocity) from April 2019 to January 2020. In addition, we also interviewed the chef’s thermal comfort in this kitchen. From the data available, we could find that 82.92% of the working hours in summer were above the acceptable range. Only 17.08% of the working hours were within the tolerance range (26–32 °C). The questionnaire results showed that 83.33% of chefs felt hot in summer. Most chefs’ wet sensations in the four seasons were neutral, and 91.6% of the chefs felt dissatisfied with the draft sensation. In addition, 88.33% of the chefs felt the fume overflowing from the exhaust hood. This may be because the exhaust fume system of the canteen kitchen was operated under the air velocity of 9.18 ± 1.6 m/s, and its exhaust airflow rate was 10,634.80 ± 189.30 m3/h, which is lower than the minimum exhaust airflow rate (12,312 m3/h). The measurement results indicated that the exhaust fume system could not remove the waste heat and fume pollutants effectively.

Numerical study on the impact of wall structure on the thermal performance of double-channel porous solar wall

With the improvement of people’s living standards, they have higher requirements for indoor thermal comfort in the cold season. Solar wall utilizing solar energy for heating can reduce carbon emissions and achieve carbon neutrality. In the aspect of solar wall research, the influence of wall structure on the thermal performance of double-channel porous solar wall is limitedly investigated. In fact, the optimization design of wall structure is important for the thermal performance of solar wall and its applications. Therefore, a simplified three dimensional room model is built to study the influence of the wall structure on the thermal performance of porous solar wall by numerical simulation. With this model, different channel spacing and thickness of porous walls were used to determine the optimal design for a double-channel porous solar wall in terms of enhancing the heat storage. Moreover, the influence of the surface emissivity on the characteristics of heating and temperature field of double-channel porous solar wall are studied based on the optimal structure. The CFD simulation results indicate that the optimal structure parameters should include spacing of 0.08 m for channel 1, the porous wall thickness should be 0.08 m, and the air channel 2 spacing should be 0.06 m. The temperature of air channel 1 and air channel 2, the indoor temperature, and the heat storage of porous wall decrease with the increase of the surface emissivity of the porous wall. In order to improve the heat storage performance of double-channel porous solar wall, the outer surface of the porous wall should use a lower emissivity material. The outer surface emissivity of porous wall has a significant impact on the heat storage of the porous wall and little effect on the thermal storage wall. The temperature of porous wall is always higher than that of outdoor environment temperature.

Energy Analysis and Forecast of a Major Modern Hospital

Healthcare buildings often have high energy use intensity, which is potentially influenced by a few factors, such as occupancy and climate. A suite of data analysis methods, including principal component analysis and regressions, is applied to analyse monthly electricity data of a modern major hospital in subtropical Australia. The analysis shows that occupancy is not highly correlated with the hospital’s electricity use, nor is it important for building energy modelling. However, outdoor environment temperature is highly correlated with the hospital’s electricity use. Then, the hospital’s electricity uses in 2030 to 2090 scenarios are forecast with future climate files. The impacts are analysed in terms of bill increases and renewable capacity needed to offset the increased electricity use. This study has established a process to predict future hospital energy use using data-driven energy modelling. This succinct article provides vital evidence to support the healthcare sector to continuously improve energy efficiency for health buildings, which is a major asset to adapt to the changing climate.

Effects of intermittent cold-exposure on culprit plaque morphology in ST-segment elevation myocardial infarction patients: a retrospective study based on optical coherence tomography

Abstract Objective Present study aimed to explore the effects of intermittent cold-exposure (ICE) on culprit plaque morphology in patients with ST-segment elevation myocardial infarction (STEMI) in frigid zone. Methods Totally 848 STEMI patients with plaque rupture (N = 637) or plaque erosion (N = 211) were enrolled consecutively according to optical coherence tomography imaging. Data on the changes of outdoor air temperature corresponding to 24 solar terms were collected. Patients were divided into different groups according to 24 solar terms and the number of days with indoor central heating. Imaging data were measured and analyzed qualitatively and quantitatively. Statistical analysis was conducted to elucidate the possible association of the STEMI patients of different groups with plaque morphology of culprit vessel with alterations of ambient temperature. Results The incidence of both plaque rupture and plaque erosion presented trough in summer. The incidence of plaque rupture reached a peak value in early winter when outdoor air temperature dropped below 0 °C and declined with supply of central heating. Persistent cold exposure in early winter was positively and significantly associated with plaque rupture. The incidence of plaque erosion presented a peak in severe winter with outdoor air temperature dropping below −20°C and steady supply of central heating. ICE in severe winter was positively and significantly associated with plaque with intact intima, especially in aged male or current smoking patients. The positive correlation of cold exposure with lipid size in culprit plaque in winter weakened with central heating. Conclusion ICE resulted from switching staying in between outdoor cold environment and indoor warm temperature with central heating in severe winter changed culprit plaque morphology in STEMI. Plaque rupture decreased whereas plaque erosion increased impacted by ICE. The effect of ICE on the transformation of plaque morphology might be explained by reduced lipid deposition.

Comparing different recalibrated methods for estimating mean radiant temperature in outdoor environment

Mean radiant temperature (MRT) is a significant variable for outdoor thermal comfort studies. Two measurement-based methods can estimate MRT, one is globe thermometer – cheap, easily-applied but relatively inaccurate, another is integral radiation measurement method (also known as the six-directional method) - accurate but expensive. Due to low-cost and convenience, the globe thermometer has been widely used. Previous studies have improved its estimation accuracy by recalibrating the convection coefficients in the ISO method. Thus, it is pending to cross-compare the performance of these recalibrated methods.This study aims to investigate the transferability of the recalibrated methods for estimating MRT in outdoor environment. First, field measurement was conducted in a subtropical city, Hong Kong. MRT was obtained through two methods: globe thermometer and integral radiation method. Second, the existing recalibrated convection coefficients were summarized, and the localized convection coefficient was recalibrated. Third, all recalibrated methods were compared for their performance. The impacts of measurement locations, devices, analysis time intervals were examined.The results showed that the newly recalibrated method achieved the lowest estimation errors (RMSE = 3.84 °C). Other recalibrated methods presented higher RMSE (3.84–17.52 °C), similar as conventional ISO method (7.91 °C). Especially for open spaces, the coefficients from other cities should be cautiously applied when the accuracy requirement is less than ±2 °C. Kestrel and Grey globe are more recommended in subtropical cities. This study shed light on the application of globe thermometer for outdoor environment, and emphasized the necessity in recalibrating the convection coefficients locally.

Coupled Conductive-Convective-Radiative Heat Transfer in Hollow Blocks with Two Air Cells in the Vertical Direction Subjected to an Incident Solar Flux

This work presents the results of a set of steady-state numerical simulations about heat transfer in hollow blocks in the presence of coupled natural convection, conduction and radiation. Blocks with two air cells deep in the vertical direction and three identical cavities in the horizontal direction are considered (typically used for building ceilings). Moreover, their outside horizontal surface is subjected to an incident solar flux and outdoor environment temperature while the inside surface is exposed to typical indoor environment conditions. The flows are considered laminar and two-dimensional over the whole range of parameters examined. The conservation equations are solved by means of a finite difference method based on the control volumes approach, relying on the SIMPLE algorithm for what concerns the coupling of pressure and velocity. The effects of the number of cells in the horizontal direction and the thermal conductivity on the heat transfer through the alveolar structure have been investigated. The results show that the number of holes has a significant impact on the value of the overall heat flux through the considered structure.

Synthesis of petaloid and origami-lantern shaped MnO2/Co2CH@C hierarchical core-shell nanorod arrays for portable asymmetric supercapacitor

Freestanding electrodes fabricated with hierarchical core-shell micro-/nano-structured materials synthesized from redox-type metal oxides show enormous potential for portable electronic devices. In this, a novel and facile strategy for the preparation of petaloid and origami-lantern shaped MnO2/Co2CH@C hierarchical porous core-shell nanorod arrays is proposed. The fabricated electrode based on MnO2/Co2CH@C hybrid composite exhibits superior capability of 2022 mF cm−2 under high current density of 5 mA cm−2, which can be explained by the well-oriented petal-like and origami-lantern shaped nanosheets as well as the 3D core-shell porous hierarchical structure. Additionally, a solid-state asymmetric supercapacitor equipment is assembled on basis of the synthesized hierarchical MnO2/Co2CH@C hybrid, exhibiting an energy density of 15 Wh kg−1 at the power density of 255 W kg−1. Notably, the multifunctional instrument can be operated by the assembled device for 8 min, while monitoring time, temperature and air humidity in a portable outdoor environment. Moreover, a blue indicator can also be operated for 9 min long, evidencing their potential commercial applications. Overall, this work demonstrates the promising potential of the synthesized novel origami-lantern shaped and highly oriented hierarchical composites for electrochemical energy storage applications.

Design and test data analysis of a heating system for a wellhead room in a coal mine

This paper introduces the design and the test data analysis of a heating system for a wellhead room in a coal mine. Combined with the system design, the actual operational data of the water jet spray heat exchange device was analysed to calculate some coefficients, the thermal efficiency and the spray heat resistance. For demonstrating the practical application of this heating system, a field test was conducted where the outdoor environment temperature was -7.4°C. The air outlet temperature of the air heating unit was 27.8°C and the air inlet temperature of a wellhead room after mixing the outdoor air and the hot air supplied from the air heating unit was 11.5°C. This performance data demonstrated that this mine return air heat exchange system well satisfies the heating requirement for the wellhead facilities in coal mines located in cold areas and shows significant advances in the designing and operation of the heating system.

Influencing factors of the drying rate of sludge for solar drying chamber

In view of the problems of low solar energy utilization efficiency, drying efficiency to be improved and sludge adhesion in the process of solar drying sludge, the research was carried out on the heat collection effect of solar collectors, sludge drying characteristics and sludge drying process, as well as the influence of sludge drying process parameters on the sludge drying rate such as hot air temperature, solar radiation intensity and air substitution,. on the self-built industrial simulation test bench. The results show that: the maximum temperature difference between the inside and the outdoor environment of the solar collectors is 36°C, when the outdoor environment temperature of the developed solar collectors is 13-26°C; the optimum process parameters of sludge drying rate under the experimental conditions that the moisture content of wet sludge is 82.7%, are as follows: the temperature of hot air is 43°C, the maximum solar radiation intensity (about 12:00), the optimal flow rate of air is controlled at 1.2m/s, the thickness of the material layer is 3cm, the large contact between air and materials improves the problem of sludge adhesion. All which provide a theoretical basis for the implementation on the industrialization of solar drying sludge.

Numerical investigation of combined heat transfer through hollow brick walls

The present study aims to investigate coupled heat transfer by natural convection, conduction and surface radiation through hollow brick walls. The numerical simulations are conducted for two typical walls built with hollow bricks in order to find the configuration that minimizes the heat gains or losses and then improves the thermal performances of the building. The outside vertical surface is submitted to an incident solar flux and outdoor environment temperature, while the inside surface is submitted to indoor environment temperature. The effects of the incident solar flux, the internal aspect ratio of hollow bricks and the thermal emissivity on the fluid flow and heat transfer through the building walls are analyzed. The results show that the hollow brick wall of type 1 improves the thermal resistance and leads to the lowest global heat transfer between the outside and inside of the building.

Performance analysis of a novel organic fluid filled regenerative heat exchanger used heat recovery ventilation (OHeX-HRV) system

In this study, a novel organic fluid-filled regenerative heat exchanger used heat recovery ventilation (OHeX-HRV) system was designed. Five organic-based fluids (R11, R123, R245fa, n-Pentane and Isopentane) were selected by considering operating conditions. Indoor air exit temperature, outdoor air inlet temperature and recovered heat by regenerative heat exchanger were analysed depending on varying airspeeds (Vair = 1,2,3 m/s) and outdoor environment temperatures (0–40 °C). As a result of the study, it was observed that recovered heat decreased as the outdoor environment temperature approaches from 0 °C to comfort temperature of indoor environment (24 °C). In contrast, the amount of heat recovered increased as the outdoor environment temperature diverges from indoor comfort temperature. The amount of recovered energy increased directly related to increasing airspeed thanks to increasing air mass flow. Among selected working fluids, n-Pentane (10.812 kJ/kg) and Isopentane (10.716 kJ/kg) used OHeX-HRV system resulted in the highest energy recovery per unit air mass. From n-Pentane used OHeX-HRV system, hourly energy recovery was calculated as 426.22 kJ/h when airspeed was 3 m/s. After comprehensive analyses, it was concluded that n-Pentane which has also superiority in terms of safety and environmental impact showed the best heat recovering performance when used in proposed OHeX-HRV system.

Numerical simulation of coupled heat transfer through double solid walls separated by an air layer

The present study aims to investigate combined heat transfer by natural convection, conduction and surface radiation through double solid wall separated by an air layer. The outside vertical surface is submitted to an incident solar flux and outdoor environment temperature. The inside surface is submitted to indoor environment temperature. The radiative coefficient (hr), the convective coefficient (hc) and the overall thermal resistance (Rg) of the air layer were generated. The effects of the incident solar flux, the air layer thickness and the thermal emissivity on the heat transfer through the double wall were examined. The results showed that the use of an air layer thickness of 5 cm combined to a low emissivity of the structure surfaces would greatly help in reducing the energy consumption of buildings.

Cold priming the chickpea seeds imparts reproductive cold tolerance by reprogramming the turnover of carbohydrates, osmo-protectants and redox components in leaves

Chickpea, a vital food legume, shows high sensitivity to cold stress at reproductive stage, and temperatures below 20/10 °C, (as day/night temperature) at this stage result in disruption in developmental and functional aspects of reproductive components, causing floral abortion, poor pods and significant yield losses. In the present study, chickpea seeds (a cold sensitive genotype GPF2) were cold primed at 5 °C ± 1 °C in the dark for 30 days, followed by gradual air-drying at 15 °C to the original moisture content (11–13%). The crop was raised in the month of November from non-primed and primed seeds in the outdoor environment (temperature profile: 11.7 °C; mean day/night temperature; 1300–1500 μmol m−2 s−1 light intensity, 65–70% relative humidity), until the onset of budding and flowering (45 days after sowing). Subsequently, the plants were separated into different sets to impose following treatments in controlled environment a) control (at optimum temperature; a set of plants were grown at optimum temperature (25/18 °C) until maturity, b) cold-stressed; a set of the plants were grown at low temperature (15/8 °C) until maturity, c) raised from cold-primed seeds but grown at optimum temperature (25/18 °C) until maturity, d) raised from cold-primed seeds and exposed to low temperature (15/8 °C), until maturity. The plants were tested for various traits in the leaves at 0–25 days after exposure to stress. Cold stress resulted in damage to membranes, photosynthetic ability (as loss of chlorophyll, photosystem II function and chlorophyll fluorescence, stomatal conductance), photo-assimilation capacity (as sucrose metabolism), hydration status (as leaf water content), production of osmolytes (as disruption in metabolism of proline, trehalose, glycine betaine, and GABA production) and decreased the redox status of the cells (as decrease in activity and expression of various enzymatic and non-enzymatic antioxidants. Reproductive function was markedly decreased, as was evident from reduction in pollen viability, pollen germination, stigma receptivity and ovule viability). Pod number and seed weight plant−1 showed 65.5 and 68.4% reduction because of cold stress. The plants raised from cold-primed seeds were remarkable benefitted at reproductive stage, which showed significantly improved pollen and stigmatic function, resulting in considerable recovery of the pod number and seed weight plant-1. The benefits of the cold priming were possibly related to improved leaf function (hydration status, photosynthetic and carbon fixation ability), which increased the sucrose concentration in the leaves to support the reproductive function, along with enhanced anti-oxidative capacity and osmo-protectants’ production, which were significantly more in cold-stressed plants, grown from cold-primed seeds, compared to the controls. Our findings in this regard are novel and suggest an effective strategy to enhance cold tolerance in chickpea.

Comparative Study of the Electrical Characteristics of Different Photovoltaic Modules in Outdoor Environment

The electrical characteristics of photovoltaic (PV) modules are affected by solar radiation and module temperature in outdoor environment. It was found that polycrystalline gained a yearly 0.50°C more average module temperature than monocrystalline. Non-crystalline amorphous modules got a yearly 0.83°C more average temperature than thin film modules. The attainment and release of module temperature was related with material properties of PV module technologies. The amorphous module gave 5.7%, 2.7% and 15.0% more yearly average open-circuit voltage than polycrystalline, monocrystalline and thin film modules. Besides that, the thin film modules gave 6.5% and 1.7%, 9.3% and 4.0%, and 11.3% and 8.8% more yearly average normalized short-circuit current and power output than polycrystalline, monocrystalline and thin film modules respectively. It was shown that the maximum annual average open-circuit voltage was given by amorphous modules and maximum short-circuit current and power output by thin film modules during the study period.

The Effect of Using Hard Landscape Material on Thermal Environment (A Case Study on Malioboro Street)

One of the current issues of temperature warning that is greatly discussed is Urban Heat Island (UHI). It is a phenomenon that can affect people’s level of comfort in doing outdoor activities with respect to the rising air temperature. There are many factors that affect the occurrence of UHI. One of them is the increasing use of hard landscape materials. This research was conducted to find out how big the influence of the use of hard material of the landscape on the decrease of outdoor environment temperature. The sample selection was taken on the research site, namely Malioboro Street, Yogyakarta, through the simulation of temperature evaluation using the Envi-Met software. The landscape materials studied include brick road (red stone) / red brick, sandy soil, asphalt road, dark concrete pavement, concrete pavement gray, and dark granite pavement. Then, each object of the study was tested and compared to determine the most optimal landscape component in the thermal environment degradation. From the results of the simulation test conducted through Envi-Met software, the change of thermal condition in each material can be identified. The difference in the changes that occurred between the materials tested was not quite significant. The hard landscape material that absorbs heat the least, and thus causing the largest thermal temperatures is the brick material, while the environment with the lowest thermal conditions use sandy soil material. Keywords: Landscape elements, Thermal environment, Temperature

Effect of highly reflective building envelopes on outdoor environment temperature and indoor thermal loads using CFD and numerical analysis

In recent years, the climate change (CC) and urban heat island (UHI) effects are becoming serious problems, affecting people’s life and health, especially in hot summer. For large cities such as Tokyo and Osaka in Japan, the UHI effect is particularly intense. It is known that about 40% of urban anthropogenic heat comes from buildings in large cities. To reduce the anthropogenic heat of buildings is an important countermeasure to this problem. Strategies for UHI mitigation include urban ventilation, urban greening, green roof, highly reflective (HR) roads, and HR building envelopes, etc. Among these mitigation strategies, the research on HR building envelopes has been carried out globally. However, it is not clear that how the HR building envelopes affect the urban outdoor environment temperature and indoor thermal loads of urban buildings which is directly related to the selection of heating, ventilation and air conditioning (HVAC) system. Thus, this study aims to evaluate the effect of solar reflectivity of building envelopes varied from 0.1 to 0.9, on the outdoor environment temperature and indoor thermal loads of buildings located on Osaka University Suita Campus, Japan, using Computational Fluid Dynamics (CFD) and numerical analysis.

Distance-based separability criterion of ROI in classification of farmland hyper-spectral images

The hyper-spectral image contains spectral and spatial information, which increases the ability and precision of objects classification. Despite the classification value of hyper-spectral imaging technology within various applications, users often find it difficult to effectively apply in practice because of the effect of light, temperature and wind in outdoor environment. This research presented a new classification model for outdoor farmland objects based on near-infrared (NIR) hyper-spectral images. It involves two steps including region of interest (ROI) acquisition and establishment of classifiers. A distance-based method for quantitative analysis was proposed to optimize the reference pixels in ROI acquisition firstly. Then maximum likelihood (ML) and support vector machine (SVM) were used for farmland objects classification. The performance of the proposed method showed that the total classification accuracy based on the reference pixels was over 97.5%, of which the SVM-M model could reach 99.5%. The research provided an effective method for outdoor farmland image classification. Keywords: distance-based separability criterion, near-infrared hyper-spectral image, ROI, farmland image classification DOI: 10.25165/j.ijabe.20171005.2264 Citation: Tang J L, Miao R H, Zhang Z Y, Xin J, Wang D. Distance-based separability criterion of ROI in classification of farmland hyper-spectral images. Int J Agric & Biol Eng, 2017; 10(5): 177–185.