Exhaust Air Temperature Research Articles

Analisis Pengaruh Faktor Meteorologi Terhadap Konsentrasi Gas SO2 dan NO2 dari Cerobong Ketel Pabrik Gula X

The process of burning bagasse in a steam boiler produces pollutants in the form of exhaust gas emissions through the chimney, which can pollute air quality and harm health. The aim of this study is to determine the great influence of meteorological factors including exhaust gas temperature, air temperature, and flow speed in 4 areas of the boiler pipe that can affect the load of SO2 and NO2 gas pollutants through statistical data analysis. The ANOVA test used in this study was the ANOVA One Way test. The results of the study showed that there was a significant influence of the air temperature factor on SO2 in Boiler 4 / Cheng Chen with a value of F value 14,553 and a sig value of 0,032, as well as the influence that exists on the exhaust gas temperature factor and air temperature on NO2 in Stork Boiler 2 with an F value of 15,358 ; 17,889 and a sig value of 0.030 ; 0.024. The results of the analysis can be used as monitoring to evaluate the success rate and operational efficiency of the boiler under the management that has been carried out.

Thermal performance of an economical air heater for space heating using composite energy storage materials

ABSTRACT Energy storage materials have the potential to improve the performance of thermal systems due to their excellent thermo-physical properties. Different energy storage materials have been tested for different thermal systems and found adequate to improve their thermal performance. Present work focuses, (i) on the development of two different composite energy storage materials (CESM) by mixing graphite black powder (obtained from lithium batteries cells) in paraffin wax and coconut oil, and (ii) testing of these materials for solar space heating inside the two similar air heating systems namely, Model-2 and Model-3. Air heating trials have been conducted on four different configurations by placing CESM-filled containers on the absorber of the tested heaters. Results of natural and forced convective operations have been compared with a similar conventional air heater (Model-1) and also to some other relevant works on air heating systems. Results revealed that Model-3 is the best model. For this system, improved heat transfer was observed at 356.20 W/m2.K, thermal efficiency was observed at about 78.8%, overall heat loss was computed at 5.91 W/m2.K and maximum exhaust air temperature was observed at about 322.05 K. The cost of Model-3 was about $51.14 (₹ 4110 in Indian currency). Model-3 can be easily developed and used for air heating and drying operations under mild cold climate conditions.

Natural Ventilation for Cooling Energy Saving: Typical Case of Public Building Design Optimization in Guangzhou, China

Heating ventilation and air conditioning systems account for over one-third of building energy usage, especially for public buildings, due to large indoor heat sources and high ventilation and thermal comfort requirements compared to residential buildings. Natural ventilation shows high application potential in public buildings because of its highly efficient ventilation effect and energy-saving potential for indoor heat dissipation. In this paper, a building design is proposed for a science museum with atrium-centered natural ventilation consideration. The floor layout, building orientation, and internal structure are optimized to make full use of natural ventilation for space cooling under local climatic conditions. The natural ventilation model is established through computational fluid dynamics (CFD) for airflow evaluation under indoor and outdoor pressure differences. The preliminary results show that such an atrium-centered architectural design could facilitate an average air exchange rate over 2 h−1 via the natural ventilation effect. Moreover, indoor thermal environment simulation results indicate that the exhaust air temperature can be about 5 °C higher than the indoor air mean temperature during the daytime, resulting in about 41.2% air conditioning energy saving ratio due to the free cooling effect of natural ventilation. This work can provide guidance and references for natural ventilation optimization design in public buildings.

Study on Effects of Operating Parameters on a Water-Cooled Loop Thermosyphon System under Partial Server Utilization

During the operation of a data center, servers are gradually installed in racks, causing most racks to work under a low heating load for a long time and affecting the cooling efficiency of the loop thermosyphon system (LTS). Thus, the effects of operating parameters on the thermal performance should be investigated. In this study, a water-cooled LTS was experimentally investigated under different airflow rates and heating loads. The results show that the additional liquid refrigerant reduced the heat transfer performance and aggravated a drop in cooling capacity when the airflow rate and heating load were decreased. To further reveal the effects of the operating parameters on the thermal performance and cooling efficiency, a steady-state distributed-parameter model was developed and validated based on the experimental data. The results show that the excessive cooling capacity was reduced by decreasing the airflow rate according to the upper limit of the server exhaust air temperature under partial server utilization. The excessive cooling capacity was reduced by 14.5–52.1% under 5–56.5% server utilization. To further reduce the excessive cooling capacity while ensuring thermal security, the water side operating parameters (including the supply chilled water temperature and water flow rate) were adjusted according to the upper limit of the rack’s average outlet air temperature, which reduced the excessive cooling capacity by more than 23.8% under partial server utilization.

Numerical investigation of the effect of rectangular and semicircular cavities filled with phase change materials installed on the solar wall

The use of alternative energy sources, particularly solar energy, in buildings is rising and spreading around the globe. In this paper, a solar wall is analyzed using a numerical method. On the wall, a number of obstacles are placed in two shapes, rectangular (REC) and semicircular (SEC). The cavities are filled with organic phase-change materials. This study was performed in 7 h in the absence of solar radiation on the wall for different dimensions of obstacles in 5 different modes. Various temperatures have been investigated, including exhaust air temperature (TAR), Trombe wall temperature (TWL), and mean volume % of molten PCM in cavities. COMSOL software is used to carry out this numerical study. The results of this study showed that the use of SECs compared to RECs causes the TWL to be higher. In the most extreme case, at a 16 cm aspect ratio, the use of SECs gives a 2.1 °C increase in TWL relative to the REC one. The outlet TAR is also increased by the usage of SECs. The use of larger dimensions of the cavities has increased the TAR leaving the wall so that the TAR after 7 h of the absence of solar radiation, in the most significant case of SECs, was more than 295.5 K. The use of SECs also increases the PCM freezing time. In the largest case of cavities, using SECs increases the freezing time by 15 min compared to RECs.

Simultaneous cooling of plate and cylindrical batteries in an air-cooled lithium battery thermal management system, by changing the distances of the batteries from each other and the pack wall

BackgroundIn this paper, heat transfer in a battery pack (BTPC) located in an air duct is subjected to numerical study. This BTPC is of both cylindrical and plate batteries and all of them are of lithium-ion type. The BTPC consists of 5 cylindrical battery columns and 4 plate battery columns, which are placed one in the middle. There are 10 battery cells in each cylindrical battery column and 9 battery cells in each battery column. The duct contained two inlets and outlets for airflow. MethodsThis study was performed for different distances of battery columns from 0.8 to 1.4 cm and the effect of battery temperature in different conditions of battery column distances was measured. This BTPC was simulated using COMSOL software. Significant findingsThe batteries in the first column are the coldest, while the batteries in the final column are the hottest, according to the findings of this research. The temperature of plate batteries is greater than that of cylindrical batteries. The quantity of heat transfer coefficient increases as the distance between the batteries grows. The maximum temperature (TMXM) of the BTPC was increased by 0.93°C by increasing the spacing between the battery pillars from 0.8 to 1.4 cm. The quantity of exhaust air temperature was decreased when the battery interval was increased from 0.8 to 1.0, but it was increased when the distance between the battery columns was increased to 1.4 cm.

An intelligent digital twin system for paper manufacturing in the paper industry

Based on the rapid development of intelligent technologies in recent years, the digital transformation of the whole industry and society has become increasingly important. Among them, digital twins and artificial intelligence have great potentials in improving industry processes and further enhancing productivity. This paper proposes an Intelligent Digital Twin System (IDTS) based on artificial intelligence and digital twins for the paper industry. The system includes the prediction models for the stirring speed of the dump chest, the water consumption of the deflaker, the supply air pressure of the dryer, and the exhaust air temperature of the dryer. The sensors, 5G network slices, and other equipment collect related data during the papermaking process for generating twin data, and we use the prediction models to analyze the data and monitor important indicators (stirring speeds, water consumptions, supply air pressures, and exhaust air temperatures) for the manufacturing processes, which are used to improve the energy utilization and production efficiency of the paper industry and thus facilitate cost saving. We apply this intelligent digital twin system and its associated prediction models to an actual paper manufacturing factory and show their effectiveness by improving the operational efficiency and saving labor and maintenance costs.

Monitoring exhaust air temperature and detecting faults during milk spray drying using data-driven framework

The advanced data analytics platform bridges the gap between industrial automation technology and new cloud-based technology. The information on the implementation of a data analytics platform to convert huge data into valuable information and use it to serve the scheduled maintenance of the components involved in the food processing industry is rarely reported in the literature. This work reports a data-driven framework for prediction and fault detection in key performance parameters for a milk spray drying process plant. The framework consists of different data analysis methods and it helps to take decisions about the selection of key performance parameters involved in improving the spray drying thermal efficiency. The neural network-based NARX model demonstrates a better performance than the linear models in the prediction of cyclone exit air temperature which is the key performance parameter in spray drying as it governs thermal efficiency. The performance of the predictive model is validated using RMSE. The ML-based classification methods are also used in the present work to classify the different faults and the decisions regarding the maintenance of the components responsible for the faults. The performance of these models was verified using a confusion matrix. It is proposed that the decision tree classifier and random forest classifier are best suitable for fault finding as their accuracy is highest at 99.83%.

Numerical investigation of gas-solid heat transfer process and parameter optimization in shaft kiln for high-purity magnesia

As the core equipment for the production of high-purity magnesia, the determination of suitable structure and operating parameters has a significant impact on its efficient production. In present work, a three-dimensional numerical model of the high-purity magnesia shaft kiln is established to study the influence of different operating and structural parameters on outlet clinker temperature and outlet exhaust air temperature. The novelty is adding a convective term to the solid-phase equation of the energy model, as well as embedding the heat transfer coefficient and a modified Ergun’s correlation, obtained by a homemade experimental setup. Production data verify the accuracy and reliability of the model. The results indicate that with all other parameters being constant, the most significant impact on the outlet temperature of clinker and exhaust air is cooling air flow rate, followed by sintering gas flow rate, height below the burners and height above the burners. Finally, a combination of parameters for the 50,000 tons shaft kiln is obtained through orthogonal experiment and optimization, which is 2622 m3/h for sintering gas flow rate, 2422 m3/h for cooling air flow rate, 7.07 m for the height above the burners, and 12.14 m for the height below the burners.

기존 주택용 창문 부착형 현열교환 환기장치 제안 및 성능 평가

Purpose: Air pollution is becoming serious around the world, and indoor air quality in buildings is also deteriorating. For energy-saving ventilation and good indoor air environment, this research proposed and made a window type heat exchange ventilation system that can be installed easily in an existing house, and examined its performance. A plate type heat exchange element for ventilator was made by a 3D printer. Method: According to the Korean Industrial Standard KS B 6879:2020 Test Method for Heat Recovery Ventilator, the ventilator was tested four times in a real environment. Two experiments were measured for 10 minutes, and the remaining two were measured for 11 hours and 10 hours, respectively. Ventilation, supply air, exhaust air, and outside air dry-bulb temperatures were measured every 5 seconds. After that, the temperature exchange efficiency was calculated for ventilation, supply air, exhaust air, and outside air average temperature using the temperature exchange efficiency formula described in KS B 6879:2020. Result: The performance was 70.97% in the first experiment, 68.11% in the second experiment, 56.47% in the third experiment, and 64.16% in the fourth experiment.

Analysis of the influence of outdoor surface heat flux on the inlet water and the exhaust air temperature of the wetting pad of a direct evaporative cooling system

The study investigates the interconnectivity between the inlet water temperature, wind flow rate, and storage water heat flux with the performance of biomass wetting pads in direct evaporative cooling under the external ambient condition of Sub-Saharan Africa. Thus, a standalone direct, evaporative cooling system with an upper water storage tank exposed to wind flow was locally developed and evaluated with jute, palm fruit mesocarp and wood charcoal as biomass cooling pad at three air velocities and constant pad thickness and three different air flow rates. The results indicated that increasing the heat flux around the water tank and decreasing the relative humidity of the inlet air through the wetting pad will lower both the inlet water and pad exhaust temperatures. The water demand was higher in palm fruit mesocarp fibre at airflow rates of 3 m/s, while at 4 and 4.5 m/s, it was higher in wood charcoal, and the value ranged from 9.64 × 10−4 to 1.46 × 10−3 kg/s. Except for jute fibre at 4 m/s, higher humidity difference or low cold room temperature did not translate to higher evaporative cooling effectiveness or efficiency. However, the lower inlet water temperature significantly affected the evaporative effectiveness. This shows the possibility of free moisture transfer into the cold room from the pad materials at increased air flow rates that helped boost the exhaust air's humidity. The average evaporative efficiency for the three pads ranged from 56.4 % to 80.96 %. The values for the enlargement coefficient ranged from 5 to 6.82, while the temperature thermal stress ranged from 24.37 to 28.66 °C.

Exhaust Smoke Validity of Vertical Shaft in Restrooms using the Stack Effect

This study is performed to validate a quantitative relationship between the exhaust rate through vertical shaft, which are used for restroom ventilation, and smoke generation based on NFSC 501. The exhaust rate is calculated using heat balance equations and is based on the input and exhaust air temperatures. The neutral plan in the vertical shaft was formed at approximately 46% of the total height. Because the smoke that is exhausted through the vertical shaft is more than 20% of the minimum smoke generation suggested by NFSC 501, the smoke exhaust through the vertical shaft is considered to be possible.

Simulation of a desiccant air-conditioning system integrated with dew-point indirect evaporative cooler for a school building

In this study, a desiccant based air-conditioning system supported by a dew-point indirect evaporative cooler, a direct evaporative cooler, two heat recovery units was investigated during a complete cooling season for air-conditioning of a school building located in Adana, Turkey. A mathematical model of the air-conditioning system was developed by deriving new equations for modelling two key components of the system, namely desiccant wheel and dew-point indirect evaporative cooler using the available correlations and experimental data. Effectiveness of desiccant wheel and dew-point evaporative cooler, heat transfer rates realized in the main system components, the thermal energy requirement to drive the system and cooling performance of the system are investigated thoroughly. The effect of desired building indoor air temperature and mixing ratio of exhaust air on the operation and performance of the system was detailed. The results show that it is possible to obtain desired comfort conditions within the building during complete cooling season with the air-conditioning system considered. The monthly average thermal COP is maximum in October with 0.78 and minimum in July with 0.22. The seasonal thermal COP of the system is 0.43.

Recuperative Heat Exchanger-Utilizer Thermodynamic Modes in Low Capacity Supply-and-Exhaust Ventilation Unit

The increase in the thermal protection level of the existing buildings enclosing structures, due to the need to comply with the current norms of building heat engineering requirements, leads to increasing in the part of heat losses in the thermal balance of a building due to infiltration and exhaust ventilation operation. After exhaustion of the possibilities for the implementation of technical measures to reduce energy costs by changing in volumetric planning solutions and insulating building envelopes further decreasing heat consumption level should be associated with the use of the secondary and renewable resources potential. The paper presents the results of assessing the technical and economic feasibility of using the exhaust air thermal potential for heating the supply air in the forced supply-and-exhaust ventilation system of a building taking as a low-capacity unit as an example. For a counterflow air-to-air recuperative type heat utilizer finned with ribbed heat pipes in the form of a plurality of continuous sheets, the influence of changes in the physical properties of the exhaust air during the phase transition of the water vapor contained in it into a liquid state on the heat exchanger-utilizer performance and characteristics of its efficiency has been established. The conditions of heat exchange are determined (without condensate, with condensate in the part of the heat exchanger-utilizer, with condensate in the entire heat exchanger-utilizer and with the risk of icing) in the supply air temperature range from (–26) to (+8) °C for three variants of its operation with a balance of the nominal amount of exhaust and supply air and with two variants of imbalance. Variants with imbalances have been investigated in order to find possible combinations of supply and exhaust air temperatures, at which there would be no phase transition of water vapor in the exhaust air flow to the liquid state in the entire volume of the heat utilizer, which would eliminate the need for measures to collect and remove condensate and preventing it from freezing.

Frost prevention research of the enthalpy wheel in air conditioning systems and industrial heat recovery systems

Enthalpy wheels are often used for air dehumidification and waste heat recovery. Application scenarios include air conditioning systems and industrial systems.Frost formation inside the enthalpy wheel is common in cold climates and has serious impacts on operational reliability and heat recovery performance. It is found that frost type, frosting area and frosting limit vary between different scenarios. Experimental and numerical investigations are conducted in the present research. For a certain wheel, inlet parameters of supply air and outlet parameters of exhaust air are the key factors influencing frosting formation. The enthalpy wheel will operate regularly without frost formation if exhaust temperature is higher than the frosting limit. Reducing the enthalpy wheel rotation speed below 6 rpm is an effective method to prevent the enthalpy wheel from frosting, but heat recovery efficiency is correspondingly reduced. Industrial systems are less affected by the cold climate, especially at higher exhaust air temperatures. Even if the climate temperature drops to −30 °C, the heat recovery efficiency can still exceed 85%. The research is anticipated to be useful for the application of enthalpy wheels in cold climates.

A comparative study of different low-cost sensible heat storage materials for solar air heating: an experimental approach

ABSTRACT Among various applications of solar energy, solar air heater is a common method to fulfill the demand of hot air for space heating. In this experimental work, a low-cost solution is discussed for solar air heating. This solution deals with integration of modified models of air heaters with graphite powder, brick powder, and desert sand. These sensible heat storage materials have been filled inside a small cylindrical-shaped container to be placed over the absorber of modified heaters for performance enhancement. Total three different configurations have been developed for comparative analysis such as, configuration 1 for graphite powder testing, configuration 2 for brick powder testing, and configuration 3 for desert sand testing. Results are compared to the same design conventional heater to find out the best configuration, which shows that the configuration 1 is the best among all tested configurations. Under the configuration 1, enhanced heat transfer is observed about 541.2 W/m2K, thermal efficiency about 37.62%, overall heat loss about 6.71 W/m2K, and maximum exhaust air temperature about 41.2°C. For a better comparative analysis, configuration 1 is further compared to some other designs of solar heaters purposely for the plate temperature and thermal efficiency. Total cost of the best configuration (model) is about $59.5.

Performance comparison of different flow arrangements of 4-fluid internally-cooled liquid desiccant dehumidifiers

In this study, the performance of 10 different flow arrangements of 4-fluid internally-cooled liquid desiccant dehumidifiers were compared. The four fluids are supply air, exhaust air, liquid desiccant, and water. The comparison was performed using a two-dimensional heat and mass transfer model of the dehumidifier that was solved numerically. The model’s predictions of supply air outlet humidity ratio matched experimental measurements within 6.7%. The two-dimensional variation of the air temperature and humidity ratio in the supply channel showed the importance of using a two-dimensional heat and mass transfer model when at least one of the fluids is in cross-flow with the other fluids. Moreover, a sensitivity analysis was performed to evaluate the effect of nine input parameters (supply air temperature and humidity ratio, exhaust air temperature and humidity ratio, liquid desiccant temperature, concentration, and flow rate, supply air mass flow rate, and exhaust to supply air mass flow rate ratio) on the performance of the dehumidifiers. The results showed that the best performance, in terms of the supply air humidity ratio and enthalpy decrease, was obtained when the supply air was in counter-flow with the exhaust air, liquid desiccant, and water. While the poorest performance was obtained when the supply air was in parallel-flow with the exhaust air and in counter-flow with the liquid desiccant and water. The approximate difference between the best and poorest performing flow arrangements in terms of the decrease in supply air humidity ratio and enthalpy is 4.3% and 10.5%, respectively. The results of the sensitivity analysis showed that for the 10 flow arrangements, the liquid desiccant inlet temperature, and flow rate have the least effects on the performance of the dehumidifier.

Combining an active method and a passive method in cooling lithium-ion batteries and using the generated heat in heating a residential unit

In this paper, a gentle air flow is simulated among cylindrical lithium-ion battery (LIIB) cells using COMSOL software. A circular PCM compartment is placed around the battery cells. The hot air from cooling the battery is used to heat the house. By changing the battery position in three modes in PCM in the air speed range of 1 × 10−3 to 5 × 10−3m/s, the volume fraction of solid PCM, the average PCM temperature (TAve−PCM), the maximum battery temperature (Tmax−b) and the exhaust air temperature at different times from 0 to 1000 seconds are analyzed. The percentage of time energy provided by this system of the total energy required for this residential house has also been examined. The results of this study show that over time at high speeds, the Tmax−b of the LIIB first increases and then decreases. The passage of time also reduces the amount of TOutlet. If the LIIB is placed on the air inlet side of the PCM instead of the air outlet side, the Tmax−b is reduced by 1.53 degrees at high speeds. Placing the LIIB on the left side of the PCM causes the output temperature (TOutlet) to be higher and also increases the amount of solid PCM by up to 5% in 1000 seconds compared to placing the LIIB on the right side. Using 50 cells of LIIB and air flow of 0.005 m/s in this system can provide up to 22% of the required energy for heating the building in a winter day.

Thermal awareness to enhance data center energy efficiency

Data centers aim at provisioning on-demand processing, storage and networking capabilities in a reliable and scalable way. In this context, proper maintenance of IT equipment within data center (DC) premises is crucial as it ensures prolonged lifetime of servers and uninterrupted availability of resources. This paper focuses on the analysis how the exact temperatures in a real big DC cluster of 10 368 cores correspond to thermal guidelines for IT devices. Available readings of servers exhaust air temperature, inlet air temperature, as well as CPUs temperature have been analyzed to uncover general statistical properties which are subsequently aggregated into several descriptive metrics that reveal global and local trends. The ultimate outcome of this research is the improvement of DC thermal management for sustainable operations via a set of recommendations.

Performance of New Absorber Coating Strategy in Solar Air Heaters: An Experimental Case Study

Asphalt materials commonly have high absorption coefficients, and their surface temperature reaches as high as 80 oC during daytime hours since their surfaces are exposed to solar radiation for long periods. Hence, asphalt pavements can easily be converted to solar air heaters (SAHs) to collect solar energy. Even though asphalt materials have low thermal conductivity, resulting in a weak convection heat exchange rate between the flowing air and asphalt surface. The current experimental study analyzes utilizing aluminum shavings as asphalt coating materials to improve SAHs’ thermal performance. To this aim, a serpentine SAH prototype was constructed, and several sensors were utilized to monitor its dynamic thermal response. Black-painted aluminum shavings were utilized as coating materials to improve the convective heat exchange rate and increase the roughness of the absorber surface. Two scenarios were considered, including the uncoated absorber plate and coated one with 0.2 kg aluminum shavings. The experiments were carried out for two air mass flow rates of 0.02 kg/s and 0.03 kg/s under field conditions. Based on the air mass flow rate, the coated absorber reaches higher temperatures, approximately 5 oC to 9 oC, than the uncoated one. The acquired results illustrate that the coated SAH has nearly 4 oC to 5 oC higher maximum exhaust air temperature; hence, the coating strategy improves the thermal efficiency by 24.75% and 44% in two air mass flow rates of 0.02 kg/s and 0.03 kg/s, respectively.