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AbstractAs a new type of building material for plants, photovoltaic roof building materials can be used as roofs of ordinary plants to reduce damage caused by secondary construction to the roofs, and can also absorb and utilize solar radiation to make full use of renewable energy. This article combines photovoltaic modules with air channels to form building material structures with ventilation ducts, establishes physical and mathematical models for photovoltaic roofs in three different inlet modes, and studies the flow and heat transfer characteristics inside air cooling integrated photovoltaic roofs. The simulation results show that the staggered-overlap-joint waterproof double-inlet photovoltaic roof can prevent rain and snow infiltration, and meanwhile, has a cooling effect on the PV panels significantly better than that of the traditional single-inlet air cooling system and the ordinary parallel double-inlet system, and its temperature difference between the inner and outer surfaces of the PV panels is increased by 19.88% compared to the traditional single-inlet air cooling system and by 15.12% compared to the parallel double-inlet system at the maximum. When the included angle between the PV panels of the staggered-overlap-joint waterproof double-inlet photovoltaic roof and the roof is 3°, the change in average temperature difference between the inner and outer surfaces of the PV panels is maximum, which is increased by 3.88% compared with that at 2°. The thickness of the air channel has small influences on the temperature change inside the air channel, the temperature difference between the inner and outer surfaces of the PV panels, and the outlet temperature. When the thickness increases from 50 mm to 200 mm, the change in outlet temperature does not exceed 0.3 K, but the increase in thickness of air layers increases the airflow velocity, which helps to take away more heat. [ABSTRACT FROM AUTHOR]

In recent years, electric vehicles (EVs) have grown in popularity as a viable way to reduce greenhouse gas emissions by replacing conventional vehicles. The need for EV batteries is steadily increasing. An essential and expensive part of electric transportation is the battery. The operating temperature of the lithium-ion (Li-ion) battery significantly impacts the performance of the EV battery pack. Battery packs undergo temperature fluctuations during the charging and discharging procedures due to internal heat generation, necessitating an examination of the temperature distribution of the battery pack. The geometrical spacing between cells is considered larger and identical and is kept open on two sides for free air circulation. A novel battery thermal management system (BTMS) design is required to effectively dissipate heat from the prismatic battery pack module. The electro-thermal behaviour of the prismatic Li-ion battery pack module was investigated based on the high charge/discharge rate. This study presents the development of a three-dimensional free open-source OpenFOAM computational fluid dynamics model for prismatic cell battery packs that simulates heat generation, air flow field, and temperature distribution across the width and depth of the battery pack module. The prismatic battery pack simulation results are compared with the experimental and simulation results of the cylindrical battery pack. It was also revealed that prismatic cells generate more heat on the backside, requiring battery packs to have increased cooling and space between individual cells to ensure sufficient air circulation for cooling and gas removal. The BTMS is improved by designing with increased space among the prismatic battery cells as compared with the conventional prismatic cell battery pack design.

[Introduction] With the development of wind power generation technology, the unit capacity of permanent magnet wind generator is increasing, and the heating power is also increasing. The heat dissipation of generator is facing unprecedented challenges. How to effectively solve the problem of generator temperature rise and heat dissipation difficulty has been the focus of our study. [Method] Based on the STAR-CCM+ software platform, an integrated numerical simulation method for generator heat dissipation and cooling was proposed in this paper. The reliability of the numerical calculation method was verified by comparing the calculated values with the experimental values. On this basis, a study was conducted on the internal temperature distribution law and the factors influencing the cooling system heat dissipation performance of the high power permanent magnet wind generator. [Result] Under the rated power, the highest temperature of the winding and stator core appear in the middle area. If the process conditions allow, the cooling water pipe should be as close to the winding as possible to take away more heat. The stator core temperature and winding temperature can be reduced significantly by increasing the total intake air volume of the generator. The intake air temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake air temperature, the maximum temperature will be reduced by about 1.4℃. Reducing the intake air temperature can improve the heat dissipation performance of the generator to a certain extent. The intake water temperature has a linear relationship with the maximum temperature of the winding and stator core. For every 5℃ decrease in the intake water temperature, the maximum temperature will be reduced by about 3.3℃. Reducing the intake water temperature can greatly improve the heat dissipation performance of the generator. In addition, the gap between the cooling water pipe and the stator core greatly hinders the heat transfer of the cooling water pipe. Filling the gap with materials with good thermal conductivity can effectively improve the heat dissipation performance of the generator. [Conclusion] The conclusions drawn in this paper can effectively guide the heat dissipation design of permanent magnet wind generator and ensure the safe operation of wind turbines in normal work.

The current refrigeration system plays an important role in human life, especially in the field of shipping, the need for refrigerants is needed for shipping and logistics storage in ships. Refrigerant R22, as stated in the regulation of the Indonesian Minister of Industry number 41/MIND/PER/5/2014, is in accordance with the regulations set forth for the removal of HCFC-22. There are alternatives needed such as refrigerant R32, R410a and R290 but the use of this type of refrigerant also creates new problems, especially damage to the refrigeration machine, problems arising from damage to parts or components in this machine according to the system supported itself. The research has been conducted by using the Failure Mode and Effect Analysis (FMEA) method. Obtained Risk Priority Number (RPN) ranking with the number of priorities that give the largest amount to the compressor on each type of refrigerant while the highest RPN value obtained 729 or 72.9% ratio for R32 refrigerant types, while R290 has a value of 576 with a ratio of 57, 6 % and R410a have a value of 448 with a ratio of 48.8%. In the calculation of this RPN mitigation will be made. The use of R32 components that should be considered is thermostatic, while R290 and R410a are the capacitors because they have the highest risk of damage. [ABSTRACT FROM AUTHOR]

• This is the first study including 3D numerical analysis on lithium-ion batteries. • Effects of height ratio, longitudinal ratio, and distance of batteries on the thermal and hydraulic behaviour have been examined. • Air cooling system with an original honeycomb configuration for electrical vehicles have been analyzed. • Velocity, temperature, and wall heat flux distribution for the BTMS design with 52 batteries were presented. This study focuses on the thermal challenges faced by lithium-ion batteries in electric vehicles and the importance of effective thermal management systems. It has been conducted a 3D numerical analysis to investigate the impact of different distances between batteries on heat transfer and flow characteristics in an air-cooled cooling module with an innovative honeycomb configuration. Boundary conditions and the study results were given with dimensionless parameters with longitudinal ratio (x/λ) , distance ratio (λ) , and height ratio (y/H). It was found that smaller distances between batteries let to higher temperatures at the beginning of the cooling channel due to the shorter channel width. However, as the distance between batteries increases, convective heat transfer performance improves, resulting in better temperature distributions and higher Nusselt numbers. The results shed light on the importance of optimizing the spatial arrangement of batteries in a cooling module to achieve efficient thermal management. This research contributes to bridging existing gaps in knowledge regarding battery thermal management in electric vehicles and provides insights for the design and development of more effective cooling strategies for lithium-ion batteries. In conclusion, according to the distance between batteries (S=1–3-5 mm) under a laminar flow regime, the best average Nussell numbers obtained for S=5 mm %17 and %7 heat enchantments compared to other S=1 mm and S=3mm cases, respectively. It can be observed that the convective heat transfer performance is optimal when all cases are located on the 9th battery. After the 9th battery column, the optimal heat transfer performance was observed for a thickness of 5 mm. The S=3 mm case exhibited a 7 % reduction in convective heat transfer performance compared to the S=5 mm case. [ABSTRACT FROM AUTHOR]

Research on an air-conditioning (AC) system that uses soil as a heat storage is still not widely conducted in Indonesia. The soil functions as a hot or cold storage medium by flowing fresh air through a heat exchanger due to its constant temperature tendency throughout a year. Earth-air exchanger (EAHE) application was simulated and got the results that soil with a volume of 12 m3 is potentially used as a heat exchange medium with a heat transfer surface area of 24.4 m2. The EAHE cooling capacity obtained is 1,002–1,282 watts depending on soil condition. Increasing the pipe diameter and airflow velocity decreases the average temperature difference by 42.9% per inch and 47.2% per m/s, respectively. Meanwhile, increasing the pipe thickness and soil depth increases the average temperature difference by 1.59% per millimeter and 6.06% per meter, respectively. The pipe interface distance recommended is greater than or equal to 200 mm. The EAHE can meet the Indonesian National Standard thermal comfort standard and ASHRAE breathing zone outdoor airflow for ventilation standard but can only meet 23.5%–30.0% of simple house-cooling loads. It consumes 75.8% lower energy and has an 139%–230% higher coefficient of performance than a split AC system.

• The coupling of CCPP power generation units to an inlet air cooling system has been presented. • Classifications and performance of the inlet air cooling systems have been reviewed. • Technical characteristics of various inlet air cooling techniques on the CCPP have been compared. • The thermal performance of the inlet air cooling technique and its effect on the CCPP performance augmentation has been reviewed. This work aims to provide a state-of-the-art review of the performance of combined cycle power plant (CCPP) based on several proposed inlet air cooling systems. Investigators strive to meet the significant need to promote and develop inlet air cooling technologies to recover heat from the wasted energy in the exhaust gasses of the CCPP and diminish the environmental impacts. Various types of cooling systems mainly offer a boost for electric power generation during the peak load hours. The output power of the CCPP directly depends on the mass flow rate of air that flows through the air compressor. Therefore, during extremely hot weather conditions, subsequently, the air density drops, and this leads to a drastic decrease in the power output. This paper reviews available studies investigated the impacts of inlet air cooling systems on the performance of the CCPP. The fogging cooling system contributed by up to 17% in improving the total performance of the CCPP; however, with the use of the evaporative cooling, the performance was enhanced by only 4%. The energy consumption of mechanical chiller compared to that of evaporative cooling is high due to the effectiveness of the evaporative cooler which depends on the humidity of inlet airflow. Further, the mechanical cooling system can provide the CCPP with a cooling effect for around 7-hour on-peak periods. This method increases the gain of the CCPP performance by 13.6%. Ultimately, the CCPP equipped with an absorption chiller demonstrates the best solution to increase the performance by up to 23%. [ABSTRACT FROM AUTHOR]

Photovoltaic (PV) cells lose in their efficiency when operating under high temperatures. Proposing a new system of cells cooling is considered an overriding necessity. For this purpose, the main objective of this paper is the development of a suitable mathematical model that can calculate the internal temperature of the PV module as a function of ambient temperature, wind speed, and total irradiance. This paper presents an electrical and thermal model that analyses the heat transfer mechanisms in PV modules such as conduction, convection, and radiation. An air forced cooling is introduced principally to improve the performance of our studied system and reducing the internal temperature. This work demonstrates a good relevant result obtained through the comparison between the PV module with and without the air-cooling system. [ABSTRACT FROM AUTHOR]

This work presents an active thermal management system (TMS) for building a safer module of lithium-ion capacitor (LiC) technology, in which 10 LiCs are connected in series. The proposed TMS is a forced air-cooled TMS (ACTMS) that uses four axial DC 12 V fans: two fans are responsible for blowing the air from the environment into the container while two other fans suck the air from the container to the environment. An experimental investigation is conducted to study the thermal behavior of the module, and numerical simulations are carried out to be validated against the experiments. The main aim of the model development is the optimization of the proposed design. Therefore, the ACTMS has been optimized by investigating the impact of inlet air velocity, inlet and outlet positions, module rotation by 90° towards the airflow direction, gap spacing between neighboring cells, and uneven gap spacing between neighboring cells. The 3D thermal model is accurate, so the validation error between the simulation and experimental results is less than 1%. It is proven that the ACTMS is an excellent solution to keep the temperature of the LiC module in the desired range by air inlet velocity of 3 m/s when all the fans are blowing the air from both sides, the outlet is designed on top of the module, the module is rotated, and uneven gap space between neighboring cells is set to 2 mm for the first distance between the cells (d1) and 3 mm for the second distance (d2).

For an air cooling system that is applied in dry machining, the thermodynamic properties of cold compressed air have an important influence on the cooling of the cutting region. In this study, the air cooling system of the dry cutting machine tool is mathematically modeled and analyzed in terms of the exergy and economic aspects of the system design and component selection. With the exergy analysis of system components, the relations between system components parameters and thermodynamic properties of compressed air are obtained. The exergy functions are verified to be acceptable for industrial application by comparing measured values with calculated values of the thermodynamic properties of cold compressed air. A multi-objective optimization process is carried out using GA (genetic algorithm) combined with the Euclidean technique and the TOPSIS (technique for order preference by similarity to ideal solution) decision-making method. Exergetic efficiency and total cost rate of the air cooling system are the objectives, while the thermodynamic properties of cold compressed air supplied to the cutting region are the constraints. The results show that an optimum solution with an exergetic efficiency of 55.1% and total cost rate of 9.37 × 10 US$/s is achieved. Furthermore, air compressor, aftercooler, and air refrigerator are the components with the highest exergy destruction rate and capital cost, and have great potential for further improvement. [ABSTRACT FROM AUTHOR]

Efficient cooling strategies are very important issues in thermal management of lithium-Ion battery system and these techniques should provide cost effective and energy saving solutions for temperature rise of the system during battery operation. A pseudo 2D electrochemical model has been used to investigate the electrochemical and thermal condition of commercial 18650 Lithium-Ion battery. This analysis was compared to previous experimental studies and results showed that the model predicts the temperature rise and thermal power generation very well. Results from the electro-thermal analysis were used to examine a cooling method. In this strategy, the cylindrical Li-ion cell is submersed within a thin cylindrical tank containing water-Al 2 O 3 nanofluid. Air flow is employed to remove the heat from the system during discharge process. After testing this method for a single cell with various sizes of the secondary cylinder, critical and thermally dangerous arrangements of Li-ion cells were analyzed employing the new technique. 3D transient Computational Fluid Dynamics (CFD) simulations were used to see the effect of presence of the secondary cylinder on temperature rise. Results revealed that the new method reduces the maximum temperature of the cells efficiently. [ABSTRACT FROM AUTHOR]

Within the existing European building stock, a large share of the suburban multi-storey residential building stock was built in the 60's-70's, when there were only few or no requirements for energy efficiency. These buildings are characterized by very high energy consumption, low air quality due to poor ventilation, and low architectural value. In this context, the European project E2VENT, that started in January 2015, aims at providing new solution of retrofitting of residential building. The proposal is a modular and adaptable ventilated façade retrofitting system that integrates an energy efficient HVAC system. This paper first presents the concept of the E2VENT module, its architecture and how it is currently designed aiming at the reduction of the energy consumption and the improvement of not only the indoor air quality but also of the aesthetic of the building. Then the presentation focuses on the LHTES system, presenting its working principle, its thermal model and how it is designed in order to allow a daily thermal storage for both cooling and heating to allow the peak shaving. Three different PCM encapsulations are presented and discussed based on their efficiency calculated with a simple model but also on more practical considerations. Finally, the first prototypes are shown and the experimental protocol to be carried out is detailed. [ABSTRACT FROM AUTHOR]

Centrifugal forces and Coriolis forces significantly influence the airflows and heat-exchange during rotation of a power hydrogenerator with one pair of poles and air conditioning of the rotor and stator. Ventilation and heat calculations of the rotor and stator are carried out using the finite element method. The influence of the motion of airflows in the ventilation ducts of the stator core, interpole space, and operating clearance on distribution of the rotor temperature is researched. The design data satisfactorily agree with the results of experimental research. It is shown that the suggested calculation method can be used while analyzing the heat condition of a hydrogenerator with a capacity of up to 1000 MW with a complete air cooling system. [ABSTRACT FROM AUTHOR]

The paper analyzes air conditioning systems of different coolants on the basis of an example of a typical office building. Depending on the type of a coolant fan coil unit, active chilled beams, variable refrigerant volumes and air cooling systems were designed. The article suggests hydraulic and aerodynamic calculations and evaluates initial investments, energy expenditures and operating costs of the compared systems. Considering economic calculations, the pay-back time of the systems was assessed and the sensitivity analysis of electricity prices was carried out. The results of the conducted investigation show the most appropriate analysed system for office buildings taking into account the efficient use of electricity and initial investments. Santrauka Tipinio administracinio pastato pavyzdžiu nagrinėjamos skirtingų šilumnešių vėsinimo sistemos. Atsižvelgiant į šilumnešio tipą suprojektuotos ventiliatorinių konvektorių, aktyviųjų šalčio sijų, freoninė ir orinė vėsinimo sistemos. Atlikti hidrauliniai ir aerodinaminiai skaičiavimai, įvertintos sistemų pradinės investicijos, apskaičiuotos energijos sąnaudos ir eksploatacijos išlaidos. Ekonominio skaičiavimo metu buvo įvertintas sistemų atsipirkimo laikas ir atlikta elektros kainų jautrumo analizė. Šio tyrimo rezultatai rodo, kokia sistema yra tinkama biurų pastatams pagal efektyvų elektros energijos naudojimą ir pradines investicijas. Raktiniai žodžiai: vėsinimas; šilumnešiai; ventiliatoriniai konvektoriai; orinė sistema; freoninė sistema; aktyviųjų šalčio sijų vėsinimo sistema

Highlights: [•] We optimized capital cost of an air cooling system using DE and PSO algorithm. [•] We conduct a comprehensive comparison of evolutionary methods. [•] We concluded evolutionary algorithms are more powerful optimization methods. [•] Best cost is obtained for varying thermodynamic parameters of the system. [ABSTRACT FROM AUTHOR]

The increasing demand for faster computing and high storage capacity has resulted in an increase in energy consumption and heat generation in datacenters. Because of the increase in heat generation, cooling requirements have become a critical concern, both in terms of growing operating costs as well as their environmental and societal impacts. Presently, thermal management techniques make an effort to thermally profile and control datacenters' cooling equipment to increase their efficiency. In conventional thermal management techniques, cooling systems are triggered by the temperature crossing predefined thresholds. Such reactive approaches result in delayed response as the temperature may already be too high, which can result in performance degradation of hardware. In this work, a proactive control approach is proposed that jointly optimizes the air conditioner compressor duty cycle and fan speed to prevent heat imbalance-the difference between the heat generated and extracted from a machine-thus minimizing the cost of cooling. The proposed proactive optimization framework has two objectives: (i) minimize the energy consumption of the cooling system, and (ii) minimize the risk of equipment damage due to overheating. Through thorough simulations comparing the proposed proactive heat-imbalance estimation-based approach against conventional reactive temperature-based schemes, the superiority of the proposed approach is highlighted in terms of cooling energy, response time, and equipment failure risk. [ABSTRACT FROM AUTHOR]

Finite Element Method (FEM) and Lumped Parameter Network (LPN) based thermal designs for the fractional slot permanent magnet synchronous motor are considered. The obtained results of temperature distribution inside the motor are validated by temperature measurements performed on a permanent magnet synchronous motor (PMSM). Thermal analysis based on Computational Fluid Dynamics (CFD) is presented here to show its advantages in cases of forced air cooling. The presented methods of the thermal modeling can be applied to other low power PMSM with passive air cooling or forced air cooling systems. [ABSTRACT FROM AUTHOR]

Abstract: In machine tools such as numerical control machines, thermal error in the ball screw induces a direct position error. A high-speed ball screw system naturally generates more heat and results in greater thermal expansion, adversely affecting the accuracy of positioning. In this paper, we discussed the placement of an air cooling system in a ball screw shaft to overcome thermal errors and achieve temperature equilibrium faster. In order to estimate the thermal error of the ball screw system and effectiveness of the air cooling system, thermal behavior models using the finite element method (FEM) and a modified lumped capacitance method (MLCM) were developed separately. This included heat generation from the main heat source of the ball screw system and other boundary conditions. The completed models were used to simulate temperature distribution, thermal deformation and air cooling performance. Comparing the experiments shows that these methods can well predict thermal behavior of the ball screw system and air cooling performance. And the positioning accuracy will significantly improve with the use of the air cooling system in the ball screw drive system. [Copyright &y& Elsevier]

Abstract: This study presents energy and exergy analyses and sustainability assessment of one novel and three conventional types of air cooling systems for building applications. First, effectivenesses of the systems are determined using energy analysis method. Second, exergy aspects of the systems are investigated for twelve different dead state temperatures varying from −5°C to 50°C with a temperature interval of 5°C. The specific exergy flows of humid air, dry air and water, exergy efficiency, and specific exergy destruction are then calculated. Sustainability index is also used to define and discuss the systems’ sustainability aspects. Finally, the results obtained here show that at the dead state temperatures of higher than 23°C (comfort temperature), exergy efficiency and sustainability of the novel system, which is based on the novel Maisotsenko cycle (M-Cycle), is higher than those of the conventional systems. At a dead state temperature of 50°C, novel cooling system''s exergy efficiency can reach 60.329% as the maximum, while the minimum exergy efficiency of other conventional cooling systems becomes as low as 35.866%, respectively. [Copyright &y& Elsevier]

Abstract: This paper investigates the development of a low cost air cooling system used for small scale applications. Its operation is based on the rational and efficient use of energy available in conventional freezers, used for other purposes than air conditioning, to cool small areas. In this paper, the proposed air cooling system is applied to small kiosk prototype (called “periptero”), found very often in the streets of Greek cities and villages, used to sell goods to people. The proposed air cooling system is using the low temperature air inside the freezers to cool the air inside the kiosk and provide a better living environment for the owner, particularly during summer period. The basic principle of the system operation and the experimental installation will be described and the experimental results will be presented and discussed. [Copyright &y& Elsevier]

Abstract: The STAR silicon strip detector (SSD) completes the three layers of the silicon vertex tracker (SVT) already installed inside the time projection chamber (TPC). This additional fourth layer provides two-dimensional hit position and energy loss measurements for charged particles, improving the STAR tracking performances and the extrapolation of the TPC tracks to the SVT hits. The design of the barrel is described; in particular the choice of the tape automated bonding (TAB) technique to connect the detectors to their front-end electronics (FEE). Several hardware aspects of the detector are presented like the power supply, the readout chain and the cooling system, as well as the production chain from the detection module to the barrel. [Copyright &y& Elsevier]

This work presents an active thermal management system (TMS) for building a safer module of lithium-ion capacitor (LiC) technology, in which 10 LiCs are connected in series. The proposed TMS is a forced air-cooled TMS (ACTMS) that uses four axial DC 12 V fans: two fans are responsible for blowing the air from the environment into the container while two other fans suck the air from the container to the environment. An experimental investigation is conducted to study the thermal behavior of the module, and numerical simulations are carried out to be validated against the experiments. The main aim of the model development is the optimization of the proposed design. Therefore, the ACTMS has been optimized by investigating the impact of inlet air velocity, inlet and outlet positions, module rotation by 90° towards the airflow direction, gap spacing between neighboring cells, and uneven gap spacing between neighboring cells. The 3D thermal model is accurate, so the validation error between the simulation and experimental results is less than 1%. It is proven that the ACTMS is an excellent solution to keep the temperature of the LiC module in the desired range by air inlet velocity of 3 m/s when all the fans are blowing the air from both sides, the outlet is designed on top of the module, the module is rotated, and uneven gap space between neighboring cells is set to 2 mm for the first distance between the cells (d1) and 3 mm for the second distance (d2). [ABSTRACT FROM AUTHOR]

This article presents a new dual purpose technique to improve photovoltaic (PV) array efficiency and has a great effect for the net power saving. To realize the first aim, the forced-air cooling technique with the optimal flow rate for PV array is designed and implemented. The decreasing rate in cell temperature has a direct proportional relation with PV efficiency. At the same time, the output hot air is very useful for air conditioning houses and for heating water systems, especially in remote areas. The electrical performance of PV modules also was studied. Finally, the effect of power saving was cleared and the economical results were achieved. [ABSTRACT FROM AUTHOR]

• Air natural convection in vertical parallel plates is investigated experimentally for wall temperature conditions up to 500 °C. • When both side walls are heated, the reverse flow does not occur at the outlet. • Flow behavior is considered by the thermal behaviors based on the measured wall and air temperatures. • Flow pattern in the channel would be determined by the geometry rather than thermal boundary condition. • Two physical correlations related to the heat transfer and induced flow rate are presented In this study, we investigated the turbulent air natural convection phenomena between open-ended vertical parallel plates under asymmetric heating conditions. The rectangular air channel consisted of two insulating walls and two heated walls: one of the vertical walls is heated to maintain uniform wall temperature conditions at various temperatures from 50 to 500 °C, and the other wall is indirectly heated by thermal radiation from the directly heated wall. We measured both wall temperature distributions in the vertical direction and the air temperature profiles with the horizontal direction at certain heights. The results showed that when both walls are heated asymmetrically, reverse flow was absent at the outlet of the channel, as confirmed by a simple visualization method. In addition, we confirmed the practical result of a deviation between the mean air temperature and the measured air temperature at the center of the channel. From the results of the wall temperature distributions and the air temperature profiles, we suggest a reasonable flow behavior, which is the generation of two different recirculation flow patterns that are not affected by changes in the thermal boundary. In addition, we compared the ratio between the convective and radiative heat rates on the directly heated wall. Based on the experimental results, we analyzed the natural convection heat transfer between vertical parallel plates and we proposed two correlations. The heat transfer correlation agreed well with the correlation for turbulent natural convection on a single infinite vertical plate. The correlating equation related to the induced flow rate was presented as a modified Rayleigh number to estimate the flow rate. [ABSTRACT FROM AUTHOR]