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The optimal performance of dew point indirect evaporative cooler with respect to the operational environment is a challenging task as the same is affected by many parameters. This paper reports the regression modeling and optimization of a counter flow indirect evaporative cooler using the response surface methodology. Experimentation is conducted using the central composite design and regression models are statistically evaluated for adequacy and found within 7% maximum error limit as compared with literature. Results show that supply temperature and cooling capacity increase with increasing inlet air velocity and inlet air temperature. Moreover, dew point and wet bulb effectiveness have a direct relationship with inlet air temperature and an inverse relationship with inlet air velocity. After validation, the regression models are subjected to single-objective and multi-objective optimization based upon the desirability function technique. The multi-objective formulation reveals that optimal performance of the system is achieved at 41.31 °C inlet air temperature, 3.61 m/sec inlet air velocity, 12 g/kg inlet air humidity, and 24.48 °C water temperature. Finally, an operational envelope is proposed to evolve a zone for the best-suited operation of such a device which ensures a reasonable cooling capacity within 1.5 – 2.5 kW while enabling thermal comfort for the conditioned space.

Recently, fluidic thrust vectoring control is popular for micro space launcher propulsion systems due to its several advantages, such as fast dynamic responsiveness, better control effectiveness, and no moving mechanical equipment. Counter-flow thrust vectoring control is an especially effective technique by utilizing less suction flow to control the mainstream deflection flexibly. In the current work, theoretical and numerical analyses are performed together to elaborate on the performance of the three-dimensional rectangular counter-flow thrust vectoring control system. A new propulsion nozzle of Mach 2.5 is devised by method of characteristics. To testify the feasibility and accuracy of the present research methodology, numerical results were validated against experimental data from the open literature. The computational result using the standard k-epsilon turbulence model reveals a good match with experimentally measured static pressure values along the centerline of the upper suction collar. The influence of several key parameters on vectoring performance is investigated herein, including the mainstream temperature, collar radius, horizontal collar length, and gap height. Critical parameters have been quantitatively analyzed, such as static pressure distribution along the centerline of the upper suction collar, pitching angle, suction mass flow ratio, and thrust coefficient. Furthermore, the flow-field features are qualitatively expounded based on the static pressure contour, streamline, iso-turbulent kinetic energy contour, and iso-Mach number contour. Some important conclusions are offered for further studies. The mainstream temperature mainly affects different dynamic characteristics of the mixing shear layer, including the convective Mach number of the shear layer, density ratio, and flow velocity ratio. The collar radius influences the pressure gradient near the suction collar surface significantly. The pitching angle increases rapidly with the increasing collar radius. As the horizontal collar length increases, the systematic deflection angle initially increases then decreases. The highest pitching angle is obtained for L/ H = 3.53. With regard to the gap height, a larger gap height can achieve a higher pitching angle.

In recent years, there has been a rapid increase in the use of counter-flow-type ion mobility spectrometers (IMS) due to their improved resolution and functionality. In this study, we developed a new type of counter-flow ion mobility device named the U-shaped mobility analyzer (UMA) for coupling with a mass spectrometer, where the analyte ions could travel along a gas flow in the first channel of the UMA device and then against a gas flow in the second channel of the device. Hence, a mobility band-pass filter was formed by setting different electric fields in the two channels, which enables high-resolution mobility selection of analyte ions. A resolution of ca. 180 was achieved for singly charged small organic molecules, and a resolution of up to ca. 370 was achieved for multiply charged +15 myoglobin. It was thus demonstrated that this filtering function can greatly enhance the dynamic range of an IMS-MS instrument, particularly favoring targeted analysis in complex matrices. Alternatively, the analyte ions could be operated in a so-called trap-scan mode in which ions were trapped first in one of the channels and released sequentially for mobility analysis with an even higher resolution (ca. 210 for singly charged small organic molecules and ca. 590 for +15 myoglobin). Overall, this new UMA device would enable many new applications in omics studies with its high resolution and dynamic range, especially when using the filter-scan mode for scrutinizing analytes with very low concentrations under high chemical backgrounds.

Experimental and computational fluid dynamics (CFD) are investigated through the vortex tube system. The benefit of vortex tube is a counter flow type tube, which has further designed and fabricated for investigation. The whole set up is consisting of a simple device that can separate a single stream of compressed air into two streams; one is at high temperature and the other is lower temperature following an inlet gas stream. The advantages of this tube are their compactness, safety, and low equipment cost mainly used in cooling and heating applications. This study addressed three-dimensional flows; the domain is using computational fluid dynamics (CFD) method and experimental approach to optimize the direction of RHVT. Through the CFD analysis, the best cold end diameter (dc), number of nozzles, and the best parameters for obtaining the highest hot gas temperature and lowest cold gas temperature were obtained and verified by experimental procedures.

This paper presents a transient investigation on the performance of a solar desiccant cooling system integrated with a counter flow Maisotsenko cycle heat and mass exchanger as an air-conditioning system for the buildings in hot and humid areas. The investigation is performed using TRNSYS software linked with a MALAB code for simulating the Maisotsenko cycle. The developed model is validated using the experimental data with the highest deviation of 4.5%. Three different mixtures of the indoor and outdoor air [100%:0% (RA1), 75%:25% (RA2) and 50%:50% (RA3)] are considered as the return air. It is found that the COP and the cooling capacity of the system decrease by the more fraction of outdoor air in the return air, whereas the supply and regeneration temperatures increase. The findings show that the solar fraction in the case of RA1 is approximately half that in the case of RA3. Based on the results of the sensitivity analysis of the system with 100% indoor air as return air, the system EER increases slightly from 0.78 to 0.82 by increasing the collector area from 16 to 25 m2. However, the system COP has a reducing trend by the collector area. Both COP and EER are enhanced by the heat wheel efficiency, because the more sensible load from the supply air is transferred to the return air.

In the present study, heat transfer characteristics of MgO-oil based nanofluid in a miniature counter-flow double-pipe heat exchanger are investigated experimentally and numerically. The nanofluid is a mixture of corn oil as a base fluid and MgO particles in nanorange. The heat exchanger is fabricated from 316 stainless steel with length 500 mm. Cold water flows in the annulus side, and the nanofluid is utilized as the hot medium in the inner tube. ANSYS FLUENT 17,0 commercial software was employed for numerical investigation. The results obtained from using nanofluids are compared with the pure oil base fluid as a hot medium. Effects of inlet flow rate of hot nanofluids and concentration of nanoparticles are considered. It is observed that the average heat transfer rates for nanofluids are higher than those for pure corn oil. The improvement of both MgO concentration and inlet flow rates of nanofluid has a positive impact on the overall heat transfer coefficient and heat transfer rate. In contrast, the pumping power augments as well as the pressure drop increases.

Membraneless microfluidic fuel cells (MMFCs) are being studied extensively as an alternative to batteries and conventional membrane fuel cells because of their simple functioning and lower manufacturing cost. MMFCs use the laminar flow of reactant species (fuel and oxidant) to eliminate the electrolyte membrane, which has conventionally been used to isolate anodic and cathodic half-cell reactions. This review article summarizes the MMFCs with six major categories of flow configurations that have been reported from 2002 to 2020. The discussion highlights the critical factors that affect and limit the performance of MMFCs. Since MMFCs are diffusion-limited, most of this review focuses on how different flow configurations act to reduce or modify diffusive mixing and depletion zones to enhance the power density output. Research opportunities are also pointed out, and the challenges in MMFCs are suggested to improve cell performance and make them practical in the near future.

This paper studies numerically the impact of installing longitudinal fins on the performance of a DPHE. Different heights were considered for these fins and three different profiles; rectangular, triangular, and semi-circular were investigated. Fins were fixed on the internal surface of the annulus side. The numerical investigation was carried out for counter flow. The study is performed in two cases. The first one was of a constant hot water mass flow rate (mh) at (0.3) kg/s and varying values of cold water mass flow rate (mc) which was from 0.2 to 1 kg/s. The second case was of a constant cold water mass flow rate (mc) at (0.3) kg/s and changing hot water mass flow rate (mh) which was from 0.2 to 1 kg/s. Inlet temperature of hot water was 353k and for cold water was 298k. The results showed that using longitudinal fins enhances the (DPHE) thermal performance. Also, semi-circular profile gave more enhancement in the rate of heat transfer compared to other studied profiles

We proposed a novel structure Y-branch waveguide based on counter flow. An intensity ratio of two light branches from 0.1 to 0.9 is realized by optimizing the core and cladding flow rate.

In this paper, we investigated the heat transfer characteristics of a brazed plate heat exchanger by using Computational Fluid Dynamics (CFD). Heat exchangers were generally analyzed considering both rating and sizing parameters. We just examined the rating parameters such as flow direction, mass flow rate, and the inlet temperature value of hot water on the thermal performance of a brazed plate heat exchanger, numerically. We also employed experiments for getting comparative results and each experiment was performed under the same conditions selected in the numerical simulations. Theoretical calculations were achieved by using the Logarithmic Mean Temperature Difference (LMTD) method for a single-phase flow and the thermal efficiency of the heat exchanger was evaluated for different conditions. The maximum total heat transfer rate was calculated about 3.1 kW for experimental study whereas this value was lower than 3 kW for numerical study in counter flow conditions. Another important result was that the effectiveness values of the heat exchanger were calculated higher under counter flow conditions as expected. The numerical results were in good agreement with the experimental data used in the study., In this paper, the heat transfer characteristics of a brazed plate heat exchanger were investigated by using Computational Fluid Dynamics (CFD) method. Due to its compact structure, the plate type heat exchangers are used in many engineering applications such as manufacturing, automotive, etc. Heat exchangers are generally analyzed considering both rating and sizing parameters. We only examined the rating parameters such as flow direction, mass flow rate, and the inlet temperature value of hot water on the thermal performance of a brazed plate heat exchanger, numerically. We also conducted experiments under the same conditions for getting comparative results with the numerical simulations. Theoretical calculations were achieved by using the Logarithmic Mean Temperature Difference (LMTD) method for a single-phase flow and the thermal efficiency of the heat exchanger was evaluated for different conditions. The maximum total heat transfer rate was calculated about 3.1 kW for experimental study whereas this value was about 3 kW for numerical study under the counter flow conditions. Considering the increase in percentage for the total heat transfer rate, the mass flow rate had more effects than the other rating parameters such as flow direction and hot water inlet temperature values. Another important result was that the effectiveness values of the heat exchanger were calculated higher under the counter flow conditions. The numerical results were in good agreement with the experimental data used in the study.

The goals of this exploration were to find out the optimum conditions of ultrasound assisted extraction (UAE) of L. Barbarum crude polysaccharides. Furthermore, to research the impacts of three multi-frequency ultrasound assisted extraction modes on the yield of L. Barbarum crude polysaccharides. The results showed that by applying the traditional single-frequency UAE mode, the optimum extraction time was 30 min, extraction temperature of 60 °C, and solid/liquid ratio of 20 g/600 mL, at a power density of 300 W/L, and ultrasound frequency of 28 kHz. Secondly; a comparison was carried out between three UAE modes using the optimum extraction conditions obtained previously. The energy aggregation counter flow dual-frequency UAE mode gave the highest yield of 38.93% of crude polysaccharides. Followed by the Opposite-sit dual-frequency UAE mode and the energy aggregation counter flow single-frequency UAE mode with yields of 33.60%, and 26.38% of crude polysaccharides, respectively. As a result the ultrasound assisted extraction with dual-frequency mode is more effective for the extraction of L. Barbarum crude polysaccharides. Furthermore, the yield of crude polysaccharides increased by 73.41% using the dual-frequency ultrasound extraction compared to traditional hot water extraction.

The optimization principle, ΔT/T = const, was wrongly shown to hold for balanced counter-flow heat exchangers due to an inappropriate analogy between a balanced counter-flow heat exchanger and a one-dimensional thermal insulation system in a paper entitled “A general variational principle for thermal insulation system design” by Bejan and then in his subsequent papers. The heat exchanger effectiveness of a balanced counter-flow heat exchanger is well known to be highest where the local temperature difference between the hot and cold streams is uniform along the entire length, with this principle ΔT = const, being independent of the absolute temperatures of the streams as the uniformity principle of the temperature difference field indicates. That is, the optimization principle for heat exchangers with the purpose of heating objects is ΔT = const, rather than ΔT/T = const. Hence, Bejan’s accusation that the uniformity principle of the temperature difference field is a duplication of his optimization principle, ΔT/T = const, for the one-dimensional thermal insulation system, is unfounded. These principles should not be confused since they apply to different scenarios.

A counter-flow heat pump driven liquid desiccant dehumidification (HPLD) system is considered as an energy-efficient approach for the humid air handling process, with advantages in terms of higher efficiency and simpler configuration. It is found that the adoption of a multi-stage heat pump cycle can improve the system performance, and then experimental tests for the system performance of the HPLD system with a two-stage heat pump cycle are investigated in the present study. The effects of solution flow rate, air inlet parameters including outdoor air and indoor exhaust air, and supplementary water capacity for the system on the system performance are elucidated according to the experimental results. It is found that the solution flow rate could affect the heat recovery performance between outdoor air and indoor exhaust air, and the performance of the heat pump. Thus, there exists an optimal solution flow rate for this counter-flow HPLD system, and the coefficient of performance of the system (COPsys) can be as high as 6.5 under the experimental condition. Besides, the increase of outdoor air inlet parameters and the decrease of indoor exhaust air inlet parameters with enough indoor exhaust air flow rate for the system have favorable effects on the system performance, due to the promotion to the heat recovery performance of the system. And more supplementary water capacity to remove the redundant heating capacity of the system would also improve the system performance mainly through lowering the condensing temperature. However, supplementary water capacity cannot be added too much for the system due to the dehumidification demand. Furthermore, the coefficient of performance of this counter-flow HPLD system is approximately 30% higher than that of a cross-flow HPLD system, handling more dehumidification demand.

Relations between effectiveness (e) and expense coefficients (ζ) were derived, and an economic simulation model was developed to simulate heat exchangers (HE) and HE networks (HEN) in all flow types for the first time. e values of parallel flow, counter flow, cross flow and all HEs under the condition of Cr = 0 were derived in terms of ζ, NTU (Number of Transfer Unit) and minimum heat capacities (Cmin). e values obtained from economic calculations were used for developing economic simulation model of HEs. Vectors including outlet temperatures and inlet temperatures of flows were obtained from static simulation to utilize in economic simulation model. Then, case studies were performed with counter flow HE and e values randomly determined in a sample HEN. Use (N), expense (P) and savings (E) of all HEs in a HEN were calculated easily by the way of linear equation systems without any complex processes, iterations, software and special hardware, in terms of both cold and hot flows properties by using economic simulation model.

In this work, the results of an experimental study on heat transfer and friction factor in a counter flow double pass solar air heater (DPSAH) duct with discrete multi V-shaped and staggered rib roughness on two broad surfaces of the heated plate have been investigated. The investigation covers a wide range of Reynolds number (Re) from 2000 to 20,000, relative staggered rib pitch (p′/p) from 0.2 to 0.8, relative staggered rib size (r/e) from 1 to 4 and relative roughness width (W/w) from 5 to 8. The optimum values of flow and geometrical parameters of roughness have been attained and explained in detail. For the Nusselt number (Nu), the maximum increase of 4.52 times to the corresponding value of smooth double pass duct has been achieved, however it has also been seen that the friction factor (f) enhanced by 3.13 folds as compared to smooth one. The rib parameters corresponding to maximum increase in Nu and f are r/e = 3.5, p′/p = 0.6 and W/w = 7. Further, correlations for Nu and f have also been developed on the basis of experimental data.

A parallel hybrid model for mechanical draft counter flow wet-cooling tower is proposed in this paper. The model consists of mechanistic model based on Merkel’s theory and Least Squares Support Vector Machine (LSSVM) model which is used to remedy the decline of prediction accuracy brought about by the theoretical assumptions in the mechanistic model. Moreover, in consideration of the variation of outlet water temperature caused by the changes of operating conditions in the cooling tower, the Gaussian Mixture Model (GMM) is applied to assess the performance of the parallel hybrid model and the model is updated according to the assessment results. The simulation results show that the proposed parallel hybrid model has better prediction accuracy compared with the mechanistic model and the hybrid model without updating, which lays an important foundation for energy-saving optimization of the mechanical draft counter flow wet-cooling tower.

Recently there has been growing interest in regenerative evaporative coolers (REC), which can reduce the temperature of the supply air to below the wet-bulb of intake air and approach its dew-point. In this paper, we designed, fabricated and experimentally tested a counter-flow REC in laboratory. The REC’s core heat and mass exchanger was fabricated using stacked sheets composed of high wicking evaporation (wickability of available materials was measured) and waterproof aluminium materials. The developed REC system has a much higher cooling performance compared to conventional indirect evaporative cooler. However, the decision to use the REC for China buildings depends on a dedicated evaluation of the net energy saved against the capital expended. Such an evaluation requires the hourly-based data on the availability of cooling capacity provided by the REC for various climates. The paper used an experiment-based method to estimate the cooling capacity and energy savings provided by the proposed REC for China’s various climates. By using the experimental results and regional hourly-based weather data, the energy saving potential of the REC against an equivalent-sized mechanical air conditioner alone was analysed. The results indicate that, for all selected regions, the REC could reduce 53–100% of cooling load and 13–58% of electrical energy consumption annually.

Energy is a holistic way of analysing multi-domain systems. By using energy, system information can be reduced to essential or dominant dynamics. This could be advantageous for the purpose of fault diagnosis. In this paper, a procedure that identifies which type of fault has occurred on a counter-flow heat exchanger and makes use of energy-visualisation is proposed. The novel methodology is achieving said energy-visualisation by using attributed graph matching. A model of a counter-flow heat exchanger is used for fault experiments. Thereafter, energy information is extracted from the model and packaged into attributed linear graphs. An attributed graph matching technique is applied to the linear graphs in order to obtain energy-visualisations for each fault. The approach of graph matching for energy-visualisation could uniquely identify three different faults.

Liquid desiccant (LD) dehumidification has attracted increasing attentions and its applications in air conditioning are emerging in recent years. The dynamic characteristics of the dehumidifier are essential to design and tune controllers for LD hybrid air conditioning systems. Existing research on liquid desiccant dehumidifier focuses on steady state condition. There is a lack of a computationally efficient yet accurate dynamic dehumidifier model for the purpose of control and dynamic simulations. This study develops a simplified one-dimensional dynamic model of a counter flow packed-type dehumidifier. The approach to quantifying the thermal mass of packing material and desiccant solution held in dehumidifier is developed for the first time and implemented in the dynamic model. Validation results show that the dynamic model is in better agreement with experiment than the static model. Root-Mean-Square Errors (RMSEs) between the simulation results of dynamic model and the experimental results are about 0.2 g/kg for the outlet air humidity ratio and 0.2 °C for the outlet air temperature. In addition, sensitivity analysis is conducted to investigate the effects of the thermal mass on the dehumidifier dynamics. The dynamic model and the results are valuable to design and tune controllers and dynamic simulations of the LD hybrid air conditioning systems.

Fluid flow design and heat transfer components utilising computational fluid dynamics (CFD) are relatively new because of cheaper and accurate method that becomes popular and reliable today. In this study, the helical coil tube heat exchanger is designed and modelled on solid modelling software. The modelled designs are analysed through ANSYS Fluent. The water is considered as working fluid, and copper as the solid material. The CFD analysis of parallel flow as well as counter flow is compared for the parameters like effective thermal conductivity, velocity and pressure. As an outcome, counter-flow heat exchanger provides effective outcome than the parallel-flow heat exchanger. The study explains about the numerical design and CFD analysis’ procedures of the helical coiled tube heat exchanger.

Energy is a primary commodity of nature that transmits between parts of a system in the output of physical change within the system and usually considered as the capacity to do work. Energy sources could be abundant; however, conversion and utilization to a more effective output need to be discovered. There is a wide variety of existing vertical axis wind turbines, VAWT, but the efficiency is low compared to that of a horizontal axis wind turbine because of the presence of counter flow drag. In order to address this problem, a vertical axis wind turbine with deflectable blades that would minimize counter drag flow and maximize efficiency is designed and developed. The newly developed VAWT makes the blades deflect at a certain angle. The deflection of the blade eliminates the counter flow drag force that makes the efficiency of the vertical axis turbine increase. The results of the tests show that using the deflecting blades for vertical axis wind turbine is more efficient. The developed deflectable blade can be further improved by using lighter materials and a gear system can be considered for better speed ratio.

Background & Aim With growing proof of efficacy in varied indications, regenerative medicine has reached a positive inflection point in the investment of time and money by established industry leaders and disruptive startups. With rapid growth comes the need to devote resources to the engineering challenges that currently prevent the quick and cost-effective manufacture of therapies that maintain a consistent, high-level of quality and, in turn, can support commercial manufacturing. This is especially true when looking at patient specific cell therapies that require rapid change over of equipment and benefit little from traditional sterile barriers (i.e. filters and heat inactivation). Counter-flow centrifugation (CFC) presents an intriguing technology that, when implemented using closed and automated system, provides a platform for upstream and downstream processing of cellular therapies by incorporating multiple unit processes and mitigating the risk imposed with manual equipment transfers. Methods, Results & Conclusion The CFC technology under development by a partnership Hitachi Chemical Advanced Therapeutic Solutions (HCATS) and Invetech compounds the benefits of a fully integrated, closed processing kit with easily customizable procedures to integrate multiple unit processes onto a singular device. Increased integration of unit processes will be integral to addressing the dynamic challenges of commercial cell therapy manufacturing in a scaled-out model. The CFC device has shown the capability to perform platelet wash on apheresis collections with 99% efficiency and retain 100% of the mononuclear cells. Elutriation was able to recover 95% of all monocytes from the MNC population at 78% purity. For lymphocyte isolation, CD3/CD28 beads were incubated with the MNC fraction on the device post platelet wash where 48.6% fewer beads were required to conjugate with the T-Cell population. By incorporating multiple unit processes onto a device that also meets the need for rapid change-over between lots this device offers a unique solution to the emergent challenges of cell therapy manufacturing.

Much insight into pedestrian flow dynamics has been achieved by conducting simulations and experiments. However, the combination of pedestrian movement and psychological influence in discrete models has not been well investigated. Here we employ a multi-grid model to understand pedestrian dynamics in counter flow, coupled with the effect of emotion propagation in a crowd stampede induced by panic. The time evolution of average speed under conditions with and without emotion propagation is obtained. Though emotion propagation increases the desired speed, it easily leads to congestion because of an increase in competition in counter flow. According to the speed–density relationship, a function of the crowd density and percentage of pedestrians in counter flow is employed to identify the flowability of pedestrians in a long channel. Thus, three regimes, i.e., lane formation, the transition stage and clogging, are presented. This is useful in the organization of safe mass events with respect to crowd density. The force distribution and cumulative distribution of the largest force that pedestrians bear are further analyzed to understand a tragic incident related to crushing such as the Cambodian stampede. These results provide an estimation of the number of injuries from the perspective of force. It is hoped that this research will be helpful in crowd management.

The rotary desiccant dehumidifier is an important component which can be used in air conditioning systems in order to reduce the electrical energy consumption and introduce renewable energy sources. In this study a one dimensional gas side resistance model is presented for predicting the performance of the desiccant wheel. Measurements from two real sorption wheels are used in order to validate the model. One wheel uses silica gel as desiccant material and the other lithium chloride. The simulation results are in good agreement with the experimental data. The model is used to compare the counter flow with the co-current wheel arrangements and to explain why the counter flow one is more efficient for air dehumidification.

This paper numerically investigates the performance and heat and mass transfer processes that occur in counter-flow indirect evaporative air coolers. Different types of counter-flow air coolers were compared: a typical counter-flow unit, the same unit operating as a heat recovery exchanger, a regenerative unit and a novel modified exchanger, proposed by authors. Additionally the paper investigated impact of location of the perforated holes in the channel plate of regenerative air cooler. The numerical model is based on a one-dimensional heat and mass transfer analysis that was validated against existing experimental data. The results obtained from the simulation reveal the high effectiveness of the presented units. It was established that selected arrangements of the presented exchangers are characterized by the different efficiency in different air-conditioning applications.

The current methods used to assess the energy performance of ventilation devices do not consider all the aspects necessary for a comprehensive evaluation of decentralised ventilation concepts and can only be partially adapted to their needs. In order to improve the energy evaluation and to ensure the comparability of different systems, a calorimetric method was developed and implemented in test facilities for the evaluation of two decentralised devices: one equipped with a recuperative counter flow heat exchanger and one with a regenerative heat exchanger. This method, based on direct measurements of the heating load in an insulated test room, includes the effect of the electrical consumption of the fans on the energy performance of the ventilation devices. The calorimetric evaluation method was extended to a seasonal evaluation on the basis of a heating-degree-day method implemented for a warm, a cool and a moderate location in Europe: Athens, Strasbourg and Copenhagen. All the results are above 50% efficiency for both devices, even in Athens where the use of heat recovery ventilation is not usual.

The process of formation of a counter jet as a result of impinging of jets radially injected into a confined crossflow of cylindrical duct was studied experimentally and numerically. The axial temperature distributions upstream of the jet injection plane were measured at various jets/crossflow mass flow rates, also near the jet injection plane. Obtained data were analyzed, the conditions of formation of the jet toward the main flow were determined. The point estimates of axial and radial mixing fractions in overpenetration mode with counter jet formation have been obtained. Experimental data are in satisfactory agreement with the numerical analysis results.

The counter flow condition on the escape stairs is a situation that may occur during the evacuation from buildings when the downward flow of evacuating occupants passes the upward flow of firefighters heading to the fire floor. The aim of this work is to provide data of firefighter movement speeds for numerical modelling and calculations. A series of experiments was conducted on a staircase with and without a simultaneous counter flow of ascending firemen. Language: en

The structure of inertial-type counter flow screen is presented in this paper. It can be proved that the solid wastes with different friction factors and elasticity coefficients can be well separated by inertial-type counter flow screen. The more difference they have in friction factors and elasticity coefficients, the better sorting performance can be achieved. The selection and calculation on the dynamical parameters of inertial-type counter flow screen is carried out. The study provides the theory basis for the design on new-type friction separation equipment and develops new prospects for the application of inertial-type counter flow screen.

A numerical study is conducted by using ANSYS CFX 14.5, a commercial computational fluid dynamics program to predict the thermal performance of a counter and parallel flow on triangular double layered microchannel heat sink for various channel aspect ratios. Findings reveal that the counter flow configuration leads to a better heat transfer performance for low channel aspect ratio (α < 4) and higher Reynolds Number (Re > 700). For the parallel flow configuration, improved performance is normally shown when channel aspect ratio, α is more than 4 and lower Reynolds Number (Re < 700).

In the present study, a recuperator to improve the t hermal efficiency of a micro gas turbine is considered. The counter flow plate-fin heat exchanger with o ffset strip fins is chosen as the type of the recuperator. From the optimization study as varying design parameters of the recuperator determined from the ideal cycle analysis, the internal structure of the re cuperator is determined. The recuperator is made from stainless steel 304. In order to evaluate performance of the recuperator, experimental investigation is performed. The effects of inlet temperature of hot-side of the recuperator on the thermal performance of the recuperator are investigated. As a result, e ffectiveness of the recuperator obtained from the experiments is well consistent with that obtained from the correlations. Key words : Recuperator, Offset strip fin, Correlations, Pressure drop, Effectiveness에너지공학, 제24권 제2호(2015) Journal of Energy Engineering , Vol. 24, No. 2, pp.72~78(2015)http://dx.doi.org/10.5855/ENERGY.2015.24.2.072

With 1 the development of society, more and more large-scale activities are conducted in the cities. The issue that how to avoid emergency in respect of human performance has attracted a lot of researchers. It is easy to find the counter-flow in large-scale activities. Bi-directional movement has attracted a lot of researchers to investigate. More attention is paid to the existence of lane formation in respect of experiments and simulations. However, few attentions are drawn to the definition of lane formation in counter-flow. In this paper, a method based on deep learning technique(DBSCAN) is proposed to define lane formation. Lane formation based on DBSCAN is used to gather the pedestrians in a group, and order parameters and time step are taken into consideration in order to obtain the number of lane formation explicitly. Then proposed method is compared with previous lane formation definition. All the lanes defined by previous method are quantified during movement process, which could reflect self-organization in time, while method introduced in this manuscript are measured after movement, which needs more data after event. The proposed method has the ability to calculate the number of the lanes. The work in this paper is intended to better understand movement during counter-flow in a corridor and develop a technical foundation for evacuation strategies in large-scale activities.

Despite long period of study, Ranque effect remains unexplored in natural gas industry. There is a lack of industrial operation data. No information was found about achieving high temperatures due to Ranque effect on natural gas plants. In present experimental research, temperature separation in high pressure natural gas stream within a counter flow vortex tube was investigated. An industrial vortex tube was designed and implemented into low-temperature separation plant. It was found that Joule-Thomson effect has significant influence on temperature separation process and should be taken into account when analyzing operation data. Noticeable heating effect under investigated conditions could be seen only at very small hot stream mass fractions. To avoid liquid loading problems free gas condensate and water should be removed before the vortex tube or directly from its body. The increase of pressure ratio leads to higher temperature differences. Cold stream temperature drop is higher than Joule-Thomson effect on almost all range of cold stream mass fractions. The ejecting type of flow was achieved in experiments that causes the reduction of Ranque effect efficiency. However, such flow could also be useful for utilization of flashed petroleum gases.

Solid oxide fuel cells (SOFCs) have the potential to become one of the efficient and cost effective systems for direct conversion of a wide variety of fuels to electricity. In this study, we developed a three-dimensional multiphysics model for a single cell SOFC using COMSOL multiphysics (version 5.2) software and performed simulations to examine the effect of gas flow patterns (radial flow and counter flow) in different operating temperatures (700° C, 800° C and 1000° C) for a planar anode supported SOFC. With the help of the simulation results, we have analyzed the electrical characteristics of the single cell SOFCs. From the simulation results, it is observable that the radial gas flow pattern yields higher performance compared to the counter flow pattern and the performance also increases with operating temperature of the cell.

This paper deals with an experimental investigation of thermal performance of a forced draft counter flow wet cooling tower filled with a rotational splash type packing. Tower’s parameters are compared when the packing has been rotated and when it does not rotate (like common existing towers). However, no references regarding the effect of the rotational packing on the cooling tower performance have been found in the reviewed bibliography. The packing has 0.85 m2 area and consists of six horizontal wooden slats fixed on a threaded metallic shaft. This investigation is carried out for three inlet air temperatures 27 °C, 34 °C and 41 °C while water temperature is kept constant at 45 °C. The ranges of packing velocities are between 0 to 17 RPM and also several ranges of water to air flow rate ratio are experimented: 0.4

Experimental investigation and numerical calculation of the macromixing of multi-orifice impinging radial jets and main crossflow in the plasma-chemical reactor channel were performed. The emphasis is on the analysis of the conditions providing the formation of a jet on the channel axis directed toward the main flow. Axial and radial distributions of the temperatures were measured in four channel cross sections above the jets injection point. An empirical dependence is proposed to calculate the axial depth of penetration the counter flow jet. The dependence generalizes the measurement results and is in agreement with the data of other authors. The relationship between the parameter of counter flow jet penetration depth and the parameter of impinging jets radial depth of penetration was revealed. Experimental data are in qualitative agreement with the numerical simulation results.

This study discuss the application of Taguchi method in assessing maximum cooling tower effectiveness for the counter flow cooling tower using different types of packing. The experiments were planned based on Taguchi’s L9 orthogonal array. The trial was performed under different conditions of liquid-to-gas flow ratio, inlet water temperature and packing materials. Signal-to-noise ratio analysis, analysis of variance and regression were carried out in order to determine the effects of process parameters on cooling tower effectiveness and to identify optimal factor settings. Finally, confirmation tests verified the reliability of Taguchi method for optimization of counter flow cooling tower performance with sufficient accuracy.

Double-pass counter flow v-grove collector is considered one of the most efficient solar air-collectors. In this design of the collector, the inlet air initially flows at the top part of the collector and changes direction once it reaches the end of the collector and flows below the collector to the outlet. A mathematical model is developed for this type of collector and simulation is carried out using MATLAB programme. The simulation results were verified with three distinguished research results and it was found that the simulation has the ability to predict the performance of the air collector accurately as proven by the comparison of experimental data with simulation. The difference between the predicted and experimental results is, at maximum, approximately 7% which is within the acceptable limit considering some uncertainties in the input parameter values to allow comparison. A parametric study was performed and it was found that solar radiation, inlet air temperature, flow rate and length have a significant effect on the efficiency of the air collector. Additionally, the results are compared with single flow V-groove collector.

Fruits drying had become a broader technology in fruits and vegetables value addition.The technology is reported to be a promising way of drying without incurring higher costbut its adaptation has not been feasible in rural areas. Solar dryers have been developedbut its poor performance limits its applicability. In this study, several techniques formodifications of traditional solar collector were addressed. It was observed that, varyingcollector designs in different techniques, a range of collector performances can bearchived. The research shows that, collector efficiency can be improved by 9.6% whenemploying double duct counter flow compared to conventional collectors. Likewise,performance difference between conventional collectors and studied models were found tobe 8%, 7.2%, 6.1% and 5.2% for model parked with charcoal, 5 mm wire mesh, 4 mmglass thickness and 8 baffles respectively. This study shows that, double duct counter flowsystem is the best option for improving the performance of the collectors, followed bycharcoal and wire mesh. On the hand, using 4 mm glass thickness gave improvedperformance, however, it is recommended for collector size not exceeding 2 m in length.

In this study, thermal performances of counter flow Ranque-Hilsch vortex tubes were experimentally investigated and modeled with a Rule Based Mamdani-Type Fuzzy (RBMTF) modeling technique. The vortex tubes were made of brass. Diameter of vortex tube (D) was 10 mm. Length of vortex tube (L) was 10D, 11D, 12D, 13D, 14D. Input parameters (ξ, L/D) and output parameters (ΔTh, ΔTc) were described by RBMTF if-then rules. 45 experimental data sets were used in the training step. R2 for the ΔTh was found to be 99.42 % and R2 for the ΔTc was 99.66 %. The actual values and RBMTF results demonstrated that RBMTF can be successfully used for the determination of heating and cooling performances of counter flow RHVT with different geometric constructions for brass.

In this study, heating and cooling performances of counter-flow Ranque–Hilsch vortex tubes (RHVT) were experimentally investigated and modeled with a RBMTF (Rule-Based Mamdani-Type Fuzzy) modeling technique. Input parameters (ξ, L/D) and output parameters ΔTh, ΔTc were described by RBMTF if-then rules. 81 experimental data sets were used in the training step. Numerical parameters of input and output variables were fuzzificated as linguistic variables: Very Very Low (L1), Very Low (L2), Low (L3), Negative Medium (L4), Medium (L5), Positive Medium (L6), High (L7), Very High (L8) and Very Very High (L9) linguistic classes. R2 for the ΔTh was found to be 99.60% and R2 for the ΔTc was 99.80%. The actual values and RBMTF results indicated that RBMTF can be successfully used for the determination of heating and cooling performances of counter-flow RHVT with different geometric constructions for steel.

This study discuss the application of Taguchi method in assessing maximum cooling tower effectiveness for the counter flow cooling tower using expanded wire mesh packing. The experiments were planned based on Taguchi?s L27 orthogonal array .The trail was performed under different inlet conditions of flow rate of water, air and water temperature. Signal-to-noise ratio (S/N) analysis, analysis of variance (ANOVA) and regression were carried out in order to determine the effects of process parameters on cooling tower effectiveness and to identity optimal factor settings. Finally confirmation tests verified this reliability of Taguchi method for optimization of counter flow cooling tower performance with sufficient accuracy.

In this paper, an extended small-grid lattice gas model is built up for pedestrian counter flow. A previous experimental work is used to compare with the extended model A simulation results to select the key parameters. The result shows that when the step in unit time is chosen as 1/2 * cnt or 1/4 * cnt and drift point is selected between 0.5 and 0.7, the model A simulation will have good agreement with the experimental study. Then model B with the same rule and the suitable key parameters is used to study pedestrian counter flow. It is found that the step in unit time and drift point have no effect on the general trend of a dynamical jamming transition from the freely moving state at low density to the stopped state at high density, but have influence on the value of critical density.

The Great East Japan Earthquake on March 11, 2011 generated a series of large tsunami waves. The tsunami waves reached area deep within the units at Fukushima Daiichi nuclear power plant. The station blackout and loss of all instrumentation and control systems at reactor 1-4 at Fukushima Daiichi nuclear power plant caused the loss of control and cooling means of three reactor units that were operational up to the time of the earthquake. These three reactor cores were heated up due to reactor decay heating. Severe damage of the fuel and a series of explosions occurred. The explosions of unit 1 and 3 at Fukushima Daiichi nuclear power plant have been investigated using image processing. The explosion of unit 1 is a typical gas explosion with the following steam release from the reactor container vessel. It seems that the destruction of the reactor building of unit 3 initiated by the major leakage from the reactor container vessel or gas explosion and following massive release of internal fluid accelerated the structural destruction. The ejected flammable gas burned as a counter flow flame on the roof of the reactor building of unit 3.